HARVARD UNIVERSITY

LIBRARY

OF THE

Museum of Comparative Zoology

Tfie WIson Bulletin

PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY
WEST VIRGINIA U. • MORGANTOWN, W. VA.

VOL. 84, NO. 1 MARCH 1972 PAGES 1-116

The Wilson Ornithological Society
Founded December 3, 1888

Named after ALEXANDER WILSON, the first American Ornithologist.

President — Pershing B, Hofslund, Dept, of Biology, University of Minnesota Duluth,
Duluth, Minnesota 55812.

First Vice-President — Kenneth C. Parkes, Carnegie Museum, Pittsburgh, Pennsylvania
15213.

Second Vice-President — Andrew J. Berger, Dept, of Zoology, University of Hawaii,
Honolulu, Hawaii 96822.

Secretary — James Tate, Jr,, Laboratory of Ornithology, Cornell University, Ithaca, New
York 14850.

Treasurer — William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.

Elected Council Members — Ernest P, Edwards (term expires 1972) ; Elden W. Martin
(term expires 1973); Robert D. Burns (term expires 1974).

Membership dues per calendar year are: Active, $8.00; Sustaining, $15,00;

Life memberships, $200 (payable in four installments).

The Wilson Bulletin is sent to all members not in arrears for dues.

The Josselyn Van Tyne Memorial Library
The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed
in the University of Michigan Museum of Zoology, was established in concurrence with
the University of Michigan in 1930, Until 1947 the Library was maintained entirely
by gifts and bequests of books, reprints, and ornithological magazines from members
and friends of the Society. Now two members have generously established a fund for
the purchase of new books; members and friends are invited to maintain the fund by
regular contribution, thus making available to all Society members the more important
new books on ornithology and related subjects. The fund will be administered by the
Library Committee, which will be happy to receive suggestions on the choice of new books
to be added to the Library. William A. Lunk, University Museums, University of Michi-
gan, is Chairman of the Committee. The Library currently receives 104 periodicals as gifts
and in exchange for The Wilson Bulletin. With the usual exception of rare books, any
item in the Library may be borrowed by members of the Society and will be sent prepaid
(by the University of Michigan) to any address in the United States, its possessions, or
Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers,
as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to
“The Josselyn Va i Tyne Memorial Library, University of Michigan Museum of Zoology,
Ann Arbor, Michigan.” Contributions to the New Book Fund should be sent to the
Treasurer (small sums in stamps are acceptable). A complete index of the Library’s
holdings was printed in the September 1952 issue of The Wilson Bulletin and newly
acquired books are listed periodically.

The Wilson Bulletin

The official organ of the Wilson Ornithological Society, published quarterly, in March, June, September,
and December, at Morgantown, West Virginia. The subscription price, both in the United States and elsewhere,
is $10.00 per year. Single copies, $2.50. Subscriptions, changes of address and claims for undelivered
copies should be sent to the Treasurer. Most back issues of the Bulletin are available (at $2.50
each) and may be ordered from the Treasurer. Special prices will be quoted for quantity orders.

All articles and communications for publications, books and publications for reviews should be addressed to
the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology,
Ann Arbor, Michigan.

Second class postage at Lawrence, Kansas, U.S.A. 66044

Allen Press, Inc., Lawrence, Kansas 66044

THE

WILSON BULLETIN

A Quarterly Magazine
of

Ornithology

George A. Hall

Editor

Editorial Advisory Board

Ornithological Literature Editor
Peter Stetteniieim

William C. Dilger
Douglas A. James
William A. Lunk

Helmut C. Mueller
Robert W. Nero
Kenneth C. Parkes
Glen E. Woolfenden

Andrew J. Meyerriecks

Volume 84

1972

Published

by

THE WILSON ORNITHOLOGICAL SOCIETY

THE WILSON BULLETIN

A QUARTERLY MAGAZINE OE ORNITHOLOGY

Published by The Wilson Ornithological Society

VoL. 84, No. 1 March 1972 Pages 1-116

CONTENTS

Laysan Albatross, Erontispiece photo by Harvey I Fisher 6

The Oceanic Distribution of the Laysan Albatross, Diomedea

IMMUTABILIS Harvey I. Fisher and James R. Fisher 7

Habits of the Crimson-Crested Woodpecker in Panama

Lawrence Kilham 28

Territorial Behavior in Savannah Sparrows in Southeastern

Michigan Peter E. Potter 48

Flocking Associates of the Pinon Jay

Russell P. Baida, Gary C. Bateman, and Gene F. Foster 60

On the Evolution of Sociality, with Particular Reference to

Tiaris OLIVACEA Ronald Pulliam, Barrie Gilbert, Peter Klopfer,

Dennis McDonald, Linda McDonald, and George Millikan 77

General Notes

FURTHER NOTES ON THE PINNATED BITTERN IN MEXICO AND CENTRAL AMERICA

Robert W. Dickerman 90

CHRONOLOGY OF HATCHING BY LAYING SEQUENCE IN CANADA GEESE

James A. Cooper and Jon R. Hickin 90

SPRING MIGRATION OF SWAINSON’s HAWK AND TURKEY VULTURE THROUGH VERA-
CRUZ, MEXICO James R. Purdue, Charles C. Carpenter,

Dale L. MarcelUni, and Robert F. Clarke 92

AN UNUSUAL NEST OF THE SANDHILL CRANE Carroll D. Littlefield 93

variability of TAIL MOLT IN THE BURROWING OWL William D. Courser 93

ANOTHER RECORD OF A SHORT INCUBATION PERIOD FOR THE ROBIN

Henri C. Seibert 95

DISCOVERY OF THE NEST OF THE KAUAI AKEPA C. Robert Eddinger 95

MOBBING OF A FISH CROW BY PASSERINES Walter Kingsley Taylor 98

VESPER SPARROW NESTS ABANDONED AFTER SNOW . Max //. Schroeder 98

RECORDS OF THE SCARLET IBIS AND RED-BREASTED BLACKBIRD IN ECUADOR

Henry M. Stevenson 99

Ornithological News

100

Conservation Section, Bird Damage to Corn in the United States

IN 1970 Charles P. Stone, Donald F. Mott,

Jerome F. Besser, and John W. DeGrazio 101

Ornithological Literature 106

John A. Wiens, An Approach to the Study of Ecological Relationships among
Grassland Birds, reviewed by D. Jean Tate; Phillip S. Humphrey, David
Bridge, Percival W. Reynolds, and Roger Tory Peterson, Birds of Isla Grande
{Tierra del Fuego), reviewed by Claes C. Olrog; Theodore C. Fitzgerald, The
Coturnix Quail; Anatomy and Histology, reviewed by Robert D. Klemm; Peter
Slater and others, A Field Guide to Australian Birds. Non-passerines, reviewed
by Roy P. Cooper; Robert J. Raikow, Evolution of Diving Adaptations in the
Stiff tail Ducks, reviewed by Lowell Spring; John S. Dunning, Portraits of
Tropical Birds, reviewed by Stephen M. Russell; Jack McCormick, The Pine
Barrens. A Preliminary Ecological Inventory, reviewed by Ernest A. Choate.

Publication Notes and Notices 99, 105, 116

Laysan Albatross in Flight. Photo by Harvey I. Fisher

THE OCEANIC DISTRIBUTION OF THE LAYSAN
ALBATROSS, DIOMEDEA IMMUTABILIS

Harvey L Fisher and James R. Fisher

The purpose of this paper is to portray the oceanic distribution of the Lay-
san Albatross (Diomedea immutabilis) as indicated by records in the
literature and by recoveries of birds banded by us. An attempt is also made
to understand the reasons for the general distribution, as well as for changes
associated with season and age.

The distribution of breeding colonies has been reviewed by Rice and
Kenyon (1962), but no one has yet attempted an analysis of the pelagic
range of the species. Present knowledge of the range is based upon incidental
sightings at sea and recoveries of a few banded birds. Several publications
list Laysan Albatrosses observed during transects of the North Pacific Ocean
(for example, Clark, 1946; Hamilton, 1958; and Cogswell, 1946), and there
are regional surveys as by Sanger (1965) off the coasts of Oregon and Wash-
ington, by Kuroda (1955) in the northwest Pacific Ocean, and by King
(1970) near the eastern end of the Hawaiian Islands.

METHODS

Data used in the analysis consisted of 109 recoveries of birds we banded, 53 published
records of birds banded by others, and 113 sight records. Of the 109 recoveries, 64 birds
were less than 3 years of age, 23 were 3 to 7 years old, and 22 were adults, including 19
known breeders. No significance can be attached to the relative numbers of the different
age classes; we banded several times as many young as juveniles or adults. The sightings
date from 1897 (Kaeding, 1905), but most are since 1945. Sight records prior to 1897
were not included because of possible confusion between records of the Laysan and the
Short- tailed Albatross (D. albatrus) prior to that date. Attempts have been made to
verify all records and to eliminate questionable sightings, hut data collected over such a
long period and by so many different persons are subject to some error. Gathering of
data over three-fourths of a century does have one advantage; it tends to smooth out
annual vagaries such as Ingham (1959) and Tickell and Scotland (1961) noted in the
annual patterns of dispersal of Giant Petrels iMacronectes f^iganteus) .

The paucity of verified records (276) spread over the millions of square miles of the
North Pacific Ocean is troublesome and in several instanc(‘s makes impossible more than
tentative statements. The problem is ameliorated, however, by multiple records in certain
regions. Another (juestion is whether our data reflect the distribution of albatrosses or
of persons recapturing albatrosses. A minimum of 69 p(*r cent and a tnaximum of 89 p(‘r
cent of the recaptures were made by .Japanese tuna fishermen; 9 per cent were taken
as scientific specimens. Tin; unc('rtainty in actual figures aris(‘s because tin* codes us«‘d
by the IJ.S. Fish and Wildlife S(‘rvice to indicate the method of n'coveiw are not mutu-
ally exclusive.

This possible confusion as to the distribution being indicated is pcuhaps immat(*nal,
for we can assume that most tuna fish(*rmen are where tuna ai(* or wlnue tuna can be

7

8

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

expected. The evidence also indicates a probable similarity in the distribution of tuna
and albatrosses in the North Pacific because both derive a large proportion of their food
from squid. Our studies on Midway indicate that at least 90 per cent of the Laysan’s
diet consists of squid. Nakamura (1965) reported that the main molluscan food item of
skipjack tuna {Katsuwonas pelarnis) in 1957-59 was squid. Waldron and King (1963)
found that in Hawaiian waters squid constituted 35 to 83 per cent of the food items of:
skipjack tuna; yellow fin tuna {N eothunnus macropterus) ; and bigeye tuna i Parathunnus
sibi) .

In analyzing the variation in oceanic distribution with age, three categories were estab-
lished: young birds (to 3 years of age) ; juveniles (3-7 years) ; and adults (7 plus years) .
Separation into these classes is based upon differences in behavior. Until they are three
or more years old, the young Laysans are at sea and seldom return to the breeding colony
(Fisher and Fisher, 1969). Between three and seven years the juveniles establish patterns
of return, territories, and pairs. They visit the breeding colony at intervals between
January and June. After the age of seven, the birds can be expected to be breeders, or
within a year of breeding. They tend to return to the colony initially between November
and February. Such differences in the relationship between albatrosses of different ages
and the breeding grounds may affect oceanic distribution despite the remarkable flight
powers of the albatross.

All oceanic records in the immediate vicinity of the Hawaiian Island breeding colonies
were omitted. Records associated with these colonies add nothing to our knowledge of
oceanic distribution, and their inclusion in analyses of latitudinal and longitudinal move-
ments or even of distribution introduces a bias. Breeding albatrosses are of necessity
restricted in their oceanic travels, although perhaps less than many other species.

Sea-surface temperatures are 20-year means ( 1947-66) furnished by R. A. Schwartlose
of Scripps Institution of Oceanography.

RESULTS

All 276 records reported here lie within the limits of 8 to 59° N lat. and 132°
E to 116° W long. Published reports of occurrences within these limits in-
clude: 1) 25 sightings off Japan made by Kuroda (1955). Macdonald and
Lawford (1954) and Wilhoft (1961) reported incidental sightings in the
western and central Pacific area, as did Clark (1946), Dixon and Starrett
(1952) and Hamilton (1958) ; 2) 11 sightings around the Aleutian Islands
made by Kenyon (1961), Kuroda (1955), Macdonald and Lawford (1954),
and Murie (1959) ; 3) Sight records off the west coast of North America by
Sanger (1965), Love (1958), Willet (1913), Stager (1958), Thompson
(1951), McHugh (1950), Kenyon (1950), Fredrich (1961), Holmes (1964),
Kaeding (1905), and Yocum (1947) ; and 4) Occurrences around the Hawai-
ian Islands and other eastern North Pacific islands were recorded by Fisher
(1948), Munro (1945, 1946), Hanson (1959), Jensen (1949), Cogswell
(1946), Eastman and Eastman (1958), and Thompson (1951).

Few Laysan Albatrosses have been found south of approximately 28° N,
except around the breeding colonies which are essentially between 28 and 22°
N. According to Amerson (1969), Laysans are “accidental on islands in the

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

9

Fig. 1. Records of Laysan Albatrosses in the North Pacific Ocean: sight records and
handed birds more than 3 years of age.

northern Marshalls [approx. 13° N] probably at-sea-visitor.” However, he
reported a Laysan Albatross at Mejit Island in the Marshalls, 10° 17' N and
172° 52' E. And there is the lone record at 8°. Dixon and Starrett (1952)
stated that Laysans are “Noted south of 30th parallel only to eastward of
Wake Island.” Baker (1951) in his review of Micronesian ornithology re-
ported no records of Laysan Albatrosses in the Micronesian Islands.

The plot of all the sightings of birds of unknown age and of recaptures of
our banded birds more than three years of age (Fig. 1) indicates that the
primary oceanic range of the Laysan Albatross lies between 28 and 52° N and

Fig. 2. Records of Laysan Alliatrosses in the North Pacific Ocean: handed l)irds 3
or fewer years of age.

10

THE WILSON BULLETIN

March 1972
Vol. 81, No. 1

Number of records

11 7 7 10 22 14 21 19 21 12 30 28

-I ^ ^ 1 1 \ 1 1

— h-

70

-J-

51

— t-

54

-H \ 1 h-

61 66 68 59

-H h-

60 60

41

— h-

45

H

52

Water Temperatures (F)

Aug.-

Sept.-

I

4-'

O

0

Nov.-

Dec.-

Jan.-

Feb.-

Mar.-

April-

May -

June-

Ju ly-

Fig. 3. Distribution of Laysan Albatrosses in the North Pacific Ocean by latitude,
month and surface water temperature: birds of all ages.

between 140° E and 120° W. This area includes 83 per cent of all records.
Within this general range are four areas of concentration: 1) east of Japan
and the Kurile Islands; 2) south of the western Aleutians; 3) off the west
coasts of British Columbia and the United States; and 4) at sea around the
eastern end of the Hawaiian Islands.

Certain regions contiguous to the general range have few or no instances of
sightings or recaptures of Laysans: 1) the Sea of Okhotsk and the Sea of
Japan; 2) the Bering Sea; 3) west of lower California; and 4) a vast circle
of ocean between the eastern Aleutians and the Hawaiian Islands, centering
at 40° N and 170° W. The only evidence of Laysan Albatrosses in the seas
west of Japan consists of the recovery of a banded bird off the southwest coast

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

11

Fig. 4. Distribution of Laysan Albatrosses in the North Pacific Ocean by latitude,
month and age: banded birds less than 3 years of age.

of Japan and another off the city of Okhotsk. Dement’ev et al. (1951) re-
ported that the Laysan is a casual straggler “in Russia” but listed as evidence
only one Laysan obtained in Kamchatkan waters. Kenyon ( 1950 ) reported no
certain records in the Bering Sea, and Arnold (1948) and Kuroda (1955)
saw no Laysans north of the Aleutians.

Records of birds three or fewer years of age are concentrated ( 87 per cent )
in an area east of Japan and roughly bounded by 30 to 45° N and 140 to 160°
E ( Fig. 2 ) . With only two exceptions, all birds recaptured at a year or less
of age have been between 35 and 45° N and 140 and 175° E.

Seventy-two per cent of the 3- to 7-year-old birds recaptured (23) were in
this area, and 17 per cent were nearby. One bird in the Aleutians and one in
Hawaiian waters represented the records most distant from the concentration.

Although the 22 banded adults were recajitured in widely sejia rated places,
two-thirds were in this same area east of Jajian.

The mean latitude of all recaptures or sightings is 38° N. The monthly mean
latitude of these records and the 20-year means of sea-surface temperatures at
these mean latitudes are shown in Figure 3. From May through November the
albatrosses are most freijuently north of 10° N and in temjieratures of 11 to

12

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Degrees of Longitude
East-I-West

OOOO OOOOOOOO
CO^lDCD h-OOr^CDlO'^COCN

Fig. 5. Distribution of Laysan Albatrosses in the North Pacific Ocean by longitude
and month: birds of all ages.

61° L (except in August). From December into April the majority of the
albatrosses are south of 35° N and in M ater temperatures of 59 to 68° F.

Albatrosses less than three years of age exhibit essentially the same seasonal
shift in latitude <Fig. 4i. HoMCver. in their first 12 months (excluding, of
course, approximately 5 months in the natal colony) the young birds are
found mostly north of 38° N. Although they are south of this during the
M'inter months at the beginning of their second year, none have been retaken
beloM' 30° N. They shift north a full month ahead of the older birds ( NIarch
versus April, Figs. 3 and 4, respectively) .

When the recaptures and sightings of all albatrosses are plotted by month
and mean longitude (Fig. 5i, the average longitude of occurrence appears to
be 176° E. Seasonal shifts are apparent. From May through August and from

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

13

November through January the majority of albatrosses are found between
150 and 160° E; from February to April and from September-October most
are found between 155 and 175° W.

DISCUSSION

General Considerations. — The Laysan Albatross ranges in significant num-
bers over most of the North Pacific Ocean north of 28° N and exclusive of
the contiguous seas to the west and north. Continental land to the northwest,
east, and northeast is an obvious barrier to this pelagic species. Islands to
the north and west may function similarly, as is discussed later. But no land
masses, even intermittent ones, delimit the southern extent of the range.

It is suggested that food is the most important single factor in determining
the southern limits of the range and the relative abundance of Laysan Alba-
trosses within the range. Such a positive correlation between the occurrence
of oceanic birds and their food supply is not new, of course. Kurochkin
(1963), for example, regarded food as a primary determinant of distribution
for many species including several procellariiform species. Voous (1965)
stated that the distribution of many antarctic birds corresponded with the dis-
tribution of surface plankton. The papers of Jameson (1961) and of Gibson
and Sefton (1959) on the Wandering Albatross iD. exulans) ^ of Thompson
(1951) on the Black-footed Albatross [D. nigripes) and of J. Fisher (1952),
Salomonsen (1965), and Brown (1970) on the Fulmar {Fulmarus glacialis)
also emphasized the importance of plankton.

With these views in mind, and recognizing that Midway Laysans obtain
90 per cent of their food from plankton-feeding squid whose distribution is
less known than that of plankton, it is logical to relate the occurrences of
plankton and these albatrosses.

Four factors directly and indirectly affect the volume of plankton in an
area — nutrients, water movements, water temperature, and water salinity.
Water movements, as in currents, convergences of currents, and upwellings,
affect available nutrients, temperature, and salinity. Any type of turbulence
that mixes deep and surface layers of the sea increases the availability of
nutrients in the surface layers and lowers temperatures, and both actions are
basically favorable to the growth of plankton. It is also established ( Marr.
1956, for example) that the larger euphausicls upon which both s(juid and
albatrosses feed occur primarily in the near-surface, eutrophic waters and
are virtually limited to cold currents. Thus, Laysans, plankton, s(juid. certain
temperatures, and turbulence should coincide in their distribution. J he avail-
able data support this view.

Laysan Albatrosses occur most frecjuently and in larger numbers where
water temperatures range from 10 to 65° F (King, 1970, said helow 72° F).

14

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Fig. 6. Major water masses and currents in the North Pacific Ocean.

although the temperature variance over their general range is 36 to 84° F.
And this temperature zone of preference coincides with the zone of highest
plankton productivity — between 28 and 35° N (King and Iversen, 1962).
In this zone, the south edge of the North Pacific Current, they obtained ap-
proximately 14,500 organisms per hour of trawling. North of 35° and in the
Aleutian area the catch was 9,500 per hour. Between 28 and 5° N (Hawaiian
and North Equatorial waters) King and Iversen reported less than 500 orga-
nisms per hour.

Therefore, the southern limit of the range of the Laysan Albatross appears
to be formed by a major drop in the abundance of food organisms. Tempera-
ture may be the primary factor, but salinity may also be significant as Sanger
(1970) suggested for the offshore waters west of North America. King
(1970:96) stated that albatrosses “. . . tended to be most numerous over high-
salinity water. . . .” but later “. . . it appears unlikely that surface salinity is
a significant limiting factor in the distribution of sea birds in the study area.”
However, Seckel and Yong (1970:191) noted that “Hawaii is located in the
vicinity of a relatively high salinity gradient that delineates the boundary of
the North Pacific Central Water.” The southern limit of the range of the
Laysan thus appears to coincide with major, though gradual, changes in tem-
perature and salinity. The limit can also be identified as the northern edges
of the westward-trending Equatorial Current west of the Hawaiian Islands
and of the North Pacific Equatorial Water between Hawaii and Central
America (Fig. 6 ) .

The correlation of turbulence and records of Laysan Albatrosses, mentioned

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

15

earlier, is discussed in connection with the four major concentrations of birds

(p. 15-18).

Extralimital areas. — The few records west of Japan and the Kuriles, north
of the Aleutians, and west of Lower California, despite the presence of numer-
ous fishing boats (Ommaney, 1963) which have been the main source of
records elsewhere, support the hypothesis that these areas are indeed outside
the regular range of the species.

The Japanese, Kurile, and Aleutian islands may form partial barriers to the
seas behind them, since these albatrosses do not normally approach land other
than that of the breeding grounds. Even more significant is the fact that to
reach these outer, fringe areas an albatross would have to pass through or
over rich seas which are presumably attractive feeding grounds for the species.
It is probable that the Tsushima Current just west of the Japanese islands, with
its warmth and its low productivity (Sorokin and Koblentz-Mishke, 1958),
is a major deterrent to the Laysan Albatross. The warm North Pacific Equa-
torial Water west of Lower California may be a similar factor.

The Central North Pacific area, in the south edge of and just south of the
Pacific Subarctic Water (Fig. 6), also lacks significant numbers of records.
Less than 10 per cent are from this several-million-square-mile region which is
devoid of strong currents, turbulences or upwellings and which is lower in
plankton productivity than the regions to the north or south ( King and
Iversen, 1962). The occasional records within this vast expanse of sea are
in either the fringes of the Aleutian Current or the eastward extension of the
North Pacific Current, and the birds may be assumed to be vagrants from the
richer areas near the source of these currents. However, the scarcity of records
may reflect the lesser human use of this region, despite our earlier discounting
of this possibility for other parts of the North Pacific.

Areas of eoneentration. — Four major concentrations of albatrosses are evi-
dent on Figure 1: 1) east of Japan; 2) south of the western Aleutians: 3)
west of North America; and 4) around the larger, eastern islands of Hawaii.

There are reasons for the Laysan Albatrosses to be numerous in each of
these areas. In each instance the conditions within the region of the concen-
tration are generally constant from year to year within a certain range of
coordinates. Bourne (1967:141) has noted that seabirds . . are normalK
restricted to very limited sea-areas by strict preferences for certain ty})es and
temperatures of surface water. . . .” Bailey (1968) noted this same phenom-
enon among seabirds in the western Indian Ocean. The Lavsans apparently
respond to permanently profitable foraging areas and do not utilize inter-
mittent, locally enriched seas. The first reason may he the time and sj)ace lag
between surface enrichment and the resulting production of suitable food.
Secondly, the exigencies of amount of food, of lime, and of distanct‘ probably

16

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

make it impossible for the Laysans to rely on spotty food resources during
such critical times of the year as the immediate pre-egg stage and the chick-
feeding period ( Eisher, 1967 ). And last, species in which each member is so
closely restricted to its own island and natal colony for breeding (Eisher,
19716) might he expected to be similarly related to its feeding areas.

The major concentration of records is east of Japan where the cold waters
of the Oyashio Current collide with the warmer waters of the Kuroshio Cur-
rent ( Eig. 6). The resulting turbulence and many eddies occur between 35
to 40° N and 140 to 160° E ( Seckel, 1970 ) and subside into the North Pacific
Current still farther east. This region has been identified by Koblentz-Mishke
(1965, Eig. 2) as having the greatest primary production in the North Pacific
Ocean. More than a third (36 per cent) of the records are within the longi-
tudinal limits of the turbulence and 30 to 45° N. Nearly half ( 45 per cent )
are here, if sightings and recaptures on the immediate fringes of the region
are included. Kuroda (1955) said of the Laysan in the northwest Pacific
“This species was most plentiful 180-200 miles eastsoutheast of Shinshiru
Island, where we saw 14 birds in one day.” This is within the area of turbu-
lence. Because of the turbulence and the consequent abundance of nutrients,
plankton and squid occur year-round, with only minor seasonal changes, and
the albatrosses find a plentiful food supply which they exploit constantly.

Although the second area of concentration, the western Aleutian region,
includes only 7 per cent of the records, we believe the Laysan Albatross uses
this area more extensively than the data may indicate. One reason is that
Laysans tend to move into cooler waters during the summer months where
plankton and presumably squid, are seasonally more abundant ( King and
Iversen, 1962 ). Another is that the Aleutian Current courses northeastward
through the islands while the Oyashio comes southward in the western part of
this region. Such flows may produce major eddies and turbulence and rich
waters around islands (Wyrtki, 1967), as has been demonstrated behind the
islands of Johnston and Hawaii ( Planar, 1969 ). Larrance (1971) has noted
the higher primary productivity in Aleutian coastal waters, as compared to
areas to the south. Bourne (1963:836) also noted the higher productivity of
seas around islands. The Aleutian region thus has all the features of a major
seasonal feeding ground.

Along the west coast of North America (120-140° W and 30-50° N) is
the third concentration (25 per cent of the records). Only two of our banded
Midway birds have been found here. Eew of these North American records
are inshore, and winter reports are negligible. It appears that the Davidson
Current, which in winter flows north along the coast to about 48° N, rather
than the continental shoreline, forms the eastern boundary of the Laysan range
in these latitudes. The Davidson and the various northward extensions of

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

17

the North Pacific Equatorial Water are probably responsible for the absence
of Laysan Albatrosses in the area south of 30° N and east of 145° W. The
warmth of this water and its low oxygen and salinity are not typical of waters
frequented by albatrosses.

Considering the amount of ship traffic, the number of scientific voyages,
and the number of persons involved here in the past 75 years, it is apparent
that this is a lesser concentration of Laysan Albatrosses than occurs east of
Japan. Although these offshore waters are reportedly rich and upwellings are
prevalent from March through July (Sverdrup et al., 1942) , there are a number
of reasons why albatrosses may occur here less frequently. 1 ) The richness of
these waters, as in the Aleutians, may be only seasonal and also considerably
less because of the admixture of warmer, southern waters. 2) It has been
suggested that Laysans avoid waters of low salinity, as found at least off
Oregon (for example, Sanger, 1970). 3) Prevailing winds and water currents
are not as advantageous for movement to and from this area as to the waters
off Japan, and the distances are greater. 4) Another possibility about which
we known little is that Laysan Albatrosses breeding on different islands may
go to different parts of the ocean. Tickell found some indication of this segre-
gation in young D. melanophris (1967) and in D. exulans and D. epomophora
(1968). Our data indicate that Midway birds are for the most part (90 per
cent) recaptured west of 180°. However, nearly half of all known oceanic
records of Laysans (117 of 276 ) are east of the date line. This could be an
indication that Laysan Albatrosses breeding in the western end of the Ha-
waiian Chain move northwest to sea and the Japanese or Aleutian concen-
trations and that albatrosses breeding farther to the east move into either the
Hawaiian or North American concentrations referred to earlier. However,
the picture is clouded by the fact that virtually all Laysans now breed east
of 180°. 5 ) There is still another explanation for the lesser number of re-
captures and sightings off the North American coast. At least 61, and perhaps
85 per cent since reporting techniques vary, of the recaptures were made by
fishermen. The Japanese tuna fishermen of the western and central Pacific
are predominantly surface fishermen of the open sea, and they recapture
albatrosses on their long-line sets of tuna hooks or in their surround nets.
Fishing in the far northeastern North Pacific, aside from a minor component
of surface trolling for sport fishes, is closer inshore and directed more toward
deeper dwelling fishes. Hence we should not expect as many albatross recap-
tures in these waters as in the Japanese area, even though the number of birds
and fishermen were the same as in the western Pacific.

Nevertheless, a significant number of Laysan Albatrosses have been re-
corded in the cool offshore waters of North America, waters formed by the
California Current or the lower limits of the Aleutian Current.

18

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Ten per cent of our Laysan records are from the fourth area, the vicinity
of the five large, easternmost islands of the Hawaiian Chain, all of which are
east and south of the primary sea range indicated earlier. Several factors,
some factors unique, some perhaps common to other concentrations, may in-
fluence the number of birds observed here. This concentration is no more than
800 miles from the breeding grounds, compared to 2,000 miles for the Japa-
nese concentration, 1,200 for the Aleutian area, and the nearly 3,000 miles
between the American concentration and the breeding grounds. There are
major water eddies, turbulence and subsequent rich waters in the lee of these
large Hawaiian islands (Manar, 1969), which may provide adequate feeding
grounds in the otherwise generally unproductive Hawaiian waters ( King and
Iversen, 1962). A large fleet of sportfishing boats and an active Audubon
Society probably increased greatly the number of sight records. But the
concentration of Laysan Albatrosses appears to he factual, and the primary
reason may be that the North Pacific Current, which turns southward at about
this longitude (Fig. 8), brings cooler, more productive water and Laysan
Albatrosses with it. And the prevailing northeast trade winds, moving essen-
tially parallel to this current, may further influence albatrosses to move south-
ward into this region.

Because of this Hawaiian concentration it is necessary to extend the primary
oceanic range of the Laysan south to 20° in the region of 155° W long.

Distribution by age. — Eighty-seven per cent of the 64 young birds were
recovered in and around the Oyashio-Kuroshio turbulence east of Japan. The
J3 per cent retaken outside this area are considered to be exceptions. Other
than the two occurrences west of Japan, the sites of recapture are ones to
which inexperienced birds may well have been transported by ocean currents
(Figs. 2, 6).

The offshore waters of Japan constitute a nursery area, at least for Midway
birds, in which the young remain until they begin their annual visits to the
breeding colonies (Fisher and Fisher, 1969). Tickell (1967) reported similar
concentrations of D. melanophris in their first 3 years of age. While adults
are commonly recaptured on both sides of the Atlantic, Falkland Islands
young go to the western Atlantic and South Georgia young move into the
eastern Atlantic. Within a few months of fledging. Fulmars from West Green-
land and St. Kilda go to the Newfoundland Banks (J. Fisher, 1952:325; J.
Fisher and Lockley, 1954:138) . And Robertson has suggested recently ( 1969)
that young Atlantic Sooty Terns {Sterna fuscata) may congregate in the Gulf
of Guinea in Africa while those of the Pacific assemble in the central Philip-
pines. It seems probable that as we learn more of the oceanic distribution of
seabirds of different ages we shall discover that many species exhibit at least
a partial segregation by age which reduces intraspecific competition.

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

19

Factors other than the richness of these Japanese waters are important in
attracting young Midway Laysans. The area is closer to Midway than is any
other known and abundant food source, and it is more easily reached by
inexperienced birds with relatively poor powers of flight. As the young bird
leaves Midway it is subjected to westward trending water currents (Fig. 6)
and generally consistent winds from the east-northeast sector (U.S. Naval
Oceanog. Office, 1966). As it rests or feeds on the water it is carried west
by south; its weak flight is greatly affected by the wind, and the bird in the
air also drifts southwest. Should it drift too far to the south, another factor
increases the rate of its westward trend — the westerly flow of the Equatorial
Current. One might compare this latter current to a drift fence along which
the young birds move until they reach the Kuroshio Current which then moves
them north to the nursery area. Conditions in these critical months of July-
September may be particularly advantageous to these birds. King and Hida
(1957) obtained their largest plankton catches then and reported that surface
catches at night were 1.5 times as large as in daytime. These data may mean
that not only are the squid attracted to the abundant food, they are attracted
presumably in greater numbers to the surface and at night. This, of course,
means greater accessibility for the initial foraging efforts of the young birds.
The abundant supply and greater availability of suitable food organisms to
inexperienced birds could be expected to hold the birds there until initial
sexual development stimulates them into migratory patterns.

The 23 juveniles were recaptured at sites more widespread than those of
young birds, but 72 per cent were taken in the rectangle described as the
nursery area. An additional 17 per cent were retaken nearby. Thus even
juveniles, most of which have already made one or more trips to the Midway
breeding colonies, return to the offshore waters of Japan.

The 22 adults were widely scattered at the time of recapture, but 68 per cent
were secured off Japan. One was recovered off California, one in the Hawaiian
area, and four in the Aleutians. Since 19 of these adults were known to have
bred on Midway, it is plausible to suggest that a majority of Midway’s breeders
return at times to feed in this area. It is unfortunate that we did not know the
current breeding status of each of these adults, for then we might know
whether they move between the breeding colony and this area during the
nesting season. Other studies in progress show that Midway adults feeding
chicks may fly east and north at least 1500 miles.

It is evident that Midway birds of all ages feed in the turbulent convergence
of currents east of Japan, that a high percentage remain there for the first
three years of life, that juveniles return there as they initiate j)eriodic visits
to the breeding colony between the ages of 3 and 7 years, and that many of
Midway’s breeding Laysan Albatrosses feed there at least from time to time.

20

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Fig. 7. Distribution of Laysan Albatrosses in the North Pacific Ocean by latitude,
longitude and month: mean locations of birds of all ages.

Seasonal distribution. — Figure 5 illustrates the occurrence of four periods
of longitudinal shift: eastward (into west longitude) in January and August
and westward in April and November. In Figure 3 three latitudinal shifts are
shown: northward in April-May and August-September and southward in
October— December. Figure 7 is an attempt to portray graphically the com-
bined results of the longitudinal and latitudinal shifts for birds of all ages.
We believe the directions of movement are accurately shown, but the extent
of the shifts is probably unduly influenced by the use of averages including
extreme records.

Starting in August, the first month of the year in which no Laysans are
involved with reproduction, there is a shift in concentration toward the north-
east along the North Pacific Current and perhaps into Pacific Subarctic Water.
This continues until October. The birds move from water near 70° F into
50-degree and presumably more productive water. In November the birds are
back in the central reaches of the North Pacific Current where the sea-surface
temperatures are now in the low 60s. In December and January the albatrosses
are near 30-35° N and 170° E where temperatures gradually climb into the
upper 60s. The birds then move eastward, with no change in latitude, to 165°
W where water temperatures are 60° or below. The birds are probably in
the same water as in December-January, water that has cooled as it moved
eastward in the southern fringe of the North Pacific Current. In April the move
is west and north to the 40-50° F waters east of Japan, waters brought to
this temperature by the cold waters of the Oyashio Current. The albatrosses
remain until late July. In all the above statements we are referring to “aver-
age moves,” not necessarily to movements of the entire populations.

It might be suggested that Figure 7 reflects at least in part the movements
to and from the breeding grounds. And one might justifiably speculate, on the

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

21

Fig. 8. Distribution of Laysan Albatrosses in the North Pacific Ocean: mean location
of birds 4 or fewer years of age.

I basis of this study and published information on the biology of the Laysan
Albatross, that: 1) virtually all of the birds less than 3 years of age are in
the May-July plotting; 2) the August to November roundtrip is made mostly
by breeders, along with some older juveniles; and 3) the December to May
I plotting consists primarily of breeders, with 3- to 7-year-olds contributing to
the March to May portion (Fisher and Fisher, 1969). It is perhaps equally
logical, with regard to the December-May period, to suggest that incubating
1 birds (November-January) with their longer periods of relief from nest duties
( 8-20 days, Fisher, 1971a ) can subsist in less productive areas. But when the
I food requirements of the chick are added to those of the foraging parents and
I when the total time for travel and foraging between chick feedings averages
j 2 days (February— April) the adults shift eastward to presumably better food
sources. Also during this time, nestling mortality has released additional
parents and the chicks are fed smaller amounts and less frequently, as evi-
denced by the fact that their weight declines after May (Fisher, 1967 ) . These
factors may permit failed or even current breeders to move northwest in April
and May.

[ However, we believe that the movements of breeding birds are not signifi-
cantly involved in the conclusions to be reached from study of Figure 7.
First, the Laysans four or fewer years of age show the same directional shifting
(Fig. 8), and most of these are not yet making their periodic visits to the
natal colonies. Second, only 37 per cent of the handed portion of the sample
is of an age to visit the colony or to breed. And third, Laysan Albatrosses in
short periods of time are capable of traversing distances greater than those
involved in the latitudinal shifts. Kenyon and Rice (1958), for example.

I showed that Laysans removed from eggs or young chicks home at the rate of
I nearly 200 miles ]>er day.

22

THE WILSON BULLETIN

March 1972
Vol. 81, No. 1

Furthermore, evidence from the literature, though scanty, tends to support
the concept of these movements and concentrations. King (1970:9) in record-
ing Laysan Albatrosses at sea east of the Hawaiian Islands and between 10
and 25° N and 148 and 150° W, gave their status as “Uncommon visitor
February-April, rare or absent May-January.” He also noted that the decline
in numbers in April was accompanied by . a contraction of range to the
northern end of the study area.”

Amerson (1969:293) wrote of the Laysan “Found at sea normally south to
15° N in the Central Pacific during the breeding seasons. . . [italics mine],
thus indicating his belief in a seasonal shift. However, his reasons were not
stated, and we now know that Laysans seldom penetrate this far south.

The northward movement of the albatrosses in summer may well be related
to the seasonal northward advection of southern water into the latitudes of
the Hawaiian Islands (Seckel and Yong, 1970). This advection brings warm
water of lower salinity into the southern part of the albatross range.

The observations of McHugh (1950), Holmes (1964 ), and Sanger (1970)
that Laysan Albatrosses were more abundant off the North American coast
“in winter” lends some strength to our view of eastward shifts in February
and March.

Hamilton’s observations (1958) during a June transit west to east and
between 35 and 48° N tend to substantiate the midsummer concentration
around the 40th parallel.

Austin and Kuroda (1954) believed that the Laysan was a regular visitor
off the Pacific coasts of Honshu and Hokkaido from early spring to late
autumn, and Kuroda (1957) said that it arrives off Japan in March. We
presume he meant greater numbers were present there at that time. It is
probable that this influx is of young birds which we think move north in
March (Fig. 4). He further wrote (p. 448) of a “post-breeding movement
northward in spring.” This may correspond to the April shift or perhaps
the greater occurrence off Japan in July. He indicated this was a movement
with the northward trend of the warm Bonin Island Air Mass. We regard it
as a seasonal movement away from the increasingly warm waters of the
Kuroshio Current. The average water temperatures in July drop from 81° F
at 30° N to 53° F at 45° N in these longitudes, and Kuroda had earlier ( 1955)
stated that the Laysan “. . . seems to avoid water above 13° C.” In 1960 he
indicated that the Laysans congregated off the Kuriles in June and July at
sea temperatures slightly above 40° F, which is in basic agreement with the
data in Figure 3. He did not find many Laysans in either the colder or
warmer waters of this region. Szijj (1967) noted that albatrosses in southern
seas were most numerous at water temperatures between 6 and 13° C.

The implication is that Laysans seek out these temperatures, for one reason

Fisher and
Fislier

DISTRIBUTION OF LAYSAN ALBATROSS

23

or another, probably food. It is probable that the Laysan adult, like the
Fulmar (J. Fisher, 1952:325; Brown, 1970; and Salomonsen, 1965 ), regularly
moves to a food source that is adequate, accessible and predictable on a time
and place basis. This seasonal phenomenon is also reported for the Wandering
Albatross (Tickell, 1968; Gibson and Sefton, 1959, 1960; and Jameson,
1961). Dixon Q933) and Tickell and Gibson (1968) believed that Wan-
derers, especially those of pre-breeding age, had a regular migratory path
between South Georgia and the sea off New South Wales. And Gibson ( 1963:
216) has said of the Wanderer: . . when free from breeding commitments

at their home islands, these birds returned regularly to an assured natural
food supply, contrary to the generally held conception of a free-ranging ocean
wanderer unbound by conventional migrations.” The Royal Albatross regu-
larly moves between Campbell Island and South America (Dixon, 1933;
Tickell, 1968). Falla (1963) noted that “several albatrosses” breeding in the
Subantarctic moved into colder waters in late summer, a shift perhaps com-
parable to the September-October move of Laysans.

Our data (Fig. 7) do not support Bourne’s view (1967) that seabirds tend
to move clockwise around anticyclonic stationaries in the middle latitudes of
. the Northern Hemisphere.

SUMMARY

All 276 oceanic records of Laysan Albatrosses are within the limits of 8 to 59° N and
132° E to 116° W in the North Pacific Ocean. The primary range, however, is between
^ 28 and 52° N and 140° E-120° W.

The northern boundary of their distribution is the Aleutian Islands and the relatively
non-productive waters of the Bering Sea. The Kurile and Japanese islands, along with
the warm Tsushima Current, constitute a western harrier. The North American continent
with its warm inshore Davidson Current forms the eastern limit. The southern border is
marked by warm equatorial waters of low salinity and low productivity.

Within these limits Laysan Albatrosses tend to congregate in four regions: 11 east of
Japan (35-40° N and 140-160° E) ; 2) south of the western Aleutians (50° N and 165°
E-175° W); 3) off the west coast of North America (30-50° N and 120-135° W);
and 4) near the large, eastern islands of Hawaii (20° N and 150 — 160° W).

The Japanese region serves as a nursery foraging area for birds fewer than 4 years of
age; seldom are they recaptured elsewhere. However, older juveniles and adults from
Midway also return there to feed.

j There is evidence of seasonal shifts in concentrations; the birds move east in JanuaiT
and August, west in April and November; they move north in April-May and in August-
: .September, south in October-December, In general these movements are associated with
j changes in surface water temperatures.

I Laysan Albatrosses tend to be associated with turbulent seas, eddies and currents;

^ the birds most frecpiently are in water tem|)eratures of 40 to 65° F. Such waters are
I generally most productive, and it is sugg(‘sted that food is the ])rimary deteiininanl of the
! Laysan’s distribution.

24

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

ACKNOWLEDGMENTS

It is impossible to thank individually the many persons who have so obviously con-
tributed to this study, but our appreciation is no less sincere. We do want to note partic-
ularly the contributions of the unknown men of the Japanese tuna fleet, for without their
cooperation in recapturing significant numbers of albatrosses at sea this study would
have been impossible.

Original financial support for the banding of nestling birds in 1961-63 came from the
Office of Naval Research (ONR 3479 (00)). Continuing support is being furnished by
the Office of Graduate Studies and Research, Southern Illinois University, Carbondale.

LITERATURE CITED

Amerson, a. B., Jr. 1969. Ornithology of the Marshall and Gilbert Islands. Atoll Res.
Bull. No. 127.

Arnold, L. W. 1948. Observations on populations of North Pacific pelagic birds. Auk,
65:553-558.

Austin, 0. L., Jr., and N. Kuroda. 1954. The birds of Japan, their status and distri-
bution. Bull. Mus. Comp. Zook, 109:277-637.

Bailey, R. S. 1968. The pelagic distribution of sea-birds in the western Indian Ocean.
Ibis, 110:493-519.

Baker, R. H. 1951. The avifauna of Micronesia, its origin, evolution, and distribution.
Univ. Kansas Publ. Mus. Nat. Hist., 3:1-359.

Brown, R. G. B. 1970. Fulmar distribution: a Canadian perspective. Ibis, 112:44-51.
Bourne, W. R. P. 1963. A review of oceanic studies of the biology of seabirds. Proc.

13th Internatl. Ornithol. Congr. Ithaca 1962, 2:831-854.

Bourne, W. R. P. 1967. Long-distance vagrancy in the petrels. Ibis, 109:141-167.
Clark, T. 0. 1946. Bird observations to San Francisco aboard a transport. Elepaio,

7:1-3.

Cogswell, H. L. 1946. Bird study aboard a transport to the Western Pacific. Elepaio,
6:46-48, 53-54, 62-63.

Dement’ev, G. P., R. N. Meklenburtsev, and A. M. Sudilovskaya. 1951. Birds of the
Soviet Union. Vol. 2.

Dixon, C. C. 1933. Some observations on the albatrosses and other birds of the southern
ocean. Trans. Roy. Canadian Inst., 19:117-139.

Dixon, K. L., and W. C. Starrett. 1952. Offshore observations of tropical seabirds in
the Western Pacific. Auk, 69:266-272.

Eastman, W., and K. Eastman. 1958. Bird study in the Hawaiian Islands is a stimu-
lating experience. Elepaio, 19:1-5.

Falla, R. A. 1963. Distribution patterns of birds in the Antarctic and high-latitude
Subantarctic. Biol. Antarctique, Prem. Symp., Sept. 2-8, Paris, 1962, pp. 367-376.
Fisher, H. I. 1948. Laysan Albatrosses nesting on Moku Manu Islet off Oahu, T. H.
Pacific Sci., 2:66.

Fisher, H. I. 1967. Body weights in Laysan Albatrosses, Diomedea immutabilis. Ibis,
109:373-382.

Fisher, H. I. 197U/. Incubation hatching, and associated behavior in the Laysan Alba-
tross, Diomedea immutabilis. The Living Bird, 10:19-78.

Fisher, H. I. 19716. Experiments on homing in Laysan Albatrosses, Diomedea im-
mutabilis. Condor, 73:389-400.

Fisher and
Fisher

DISTRIBUTION OF LAYSAN ALBATROSS

25

Fisher, H. L, and M. L. Fisher. 1969. The visits of Laysan Albatrosses to the breeding
colony. Micronesica, 5:173-221.

Fisher, J. 1952. The Fulmar. Collins, London.

Fisher, J., and R. M. Lockley. 1954. Sea-birds. Houghton Mifflin Co., Boston.
Fredrich, L. a. 1961. An occurrence of the Laysan Albatross on the northwestern
coast of Oregon. Condor, 63:506.

Gibson, J. D. 1963. Third report of the New South Wales albatross study group (1962)
summarizing activities to date. Emu, 63:215-223.

Gibson, J. D., and A. R. Sefton. 1959. First report of the New South Wales albatross
study group. Emu, 59:73-82.

Gibson, J. D., and A. R. Sefton. 1960. Notes on some albatrosses of coastal New
South Wales. Emu, 60:128-130.

Hamilton, W. J. HI. 1958. Pelagic birds observed on a North Pacific crossing. Condor,
60:159-164.

Hanson, C. 1959. [Field notes]. Elepaio, 19:67.

Holmes, R. T. 1964. Notes on the occurrence of the Laysan Albatross near the Cali-
fornia Coast. Condor, 66:302-303.

Ingham, S. B. 1959. Banding of Giant Petrels by the Australian National Antarctic
Research Expeditions, 1955-58. Emu, 59:189-200.

Jameson, W. 1961. The Wandering Albatross. Rev. ed.. Doubleday and Co., New York.
Jensen, S. 1949. Field notes: from Johnston Island. Elepaio, 9:66.

Kaeding, H. B. 1905. Birds from the west coast of Lower California and adjacent
islands. Condor, 7:105-111.

Kenyon, K. W. 1950. Distribution of albatrosses in the North Pacific and adjacent
waters. Condor, 52:97-103.

Kenyon, K. W. 1961. Birds of Amchitka Island, Alaska. Auk, 78:305-326.

Kenyon, K. W., and D. W. Rice. 1958. Homing of Laysan Albatrosses. Condor, 60:3-6.
King, J. E., and T. S. Hida. 1957. Zooplankton abundance in the Central Pacific, Part
II. Fish. Bull., 57:365-395.

King, J. E., and R. T. B. Iversen. 1962. Midwater trawling for forage organisms in the
Central Pacific 1951-1956. Fish Bull., 210:271-321.

King, W. B. 1970. The trade wind zone oceanography pilot study. Part VII: Obser-
vations of sea birds March 1964 to June 1965. U.S. Fish and Wildl. Serv. Spec. Sci.
Rept. Fish. No. 586.

Koblentz-Mishke, 0. J. 1965. [The magnitude of primary production of the Pacific
Ocean]. Oceanography (Russian), 5:325-337.

Kurochkin, E. N. 1963. [Distribution of some seabirds in the North Pacific.! Zool.
Zhur., 42:1223-1231.

I Kuroda, N. 1955. Observations on pelagic birds of the northwest Pacific. Condor, 57:
290-300.

' Kuroda, N. 1957. A brief note on the pelagic migration of the Tuhinares. YamashinaY

I Inst. Ornithol. and Zool. Misc. Rept. No. 11:436-439.

I Kuroda, N. 1960. Analysis of sea bird distribution in the Northwest Pacific Ocean.

; Pacific Sci., 14:55-67.

j Larrance, j. D. 1971. Primary production in the mid-subarctic Pacific region, l%6-68.

I Fishery Bull., 69:595-613.

^ Love, C. M. 1958. Preliminary report: Brown Bear Cruise 188 off tlie coasts of \\ asli-
j ington and Vancouver Island, 19-28 February 1958. IJniv. Washington Dept. Oceanog.

I Ref. 58-16. (ditto).

26

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Macdonald, J. D., and P. A. Lawford. 1954. Sight records of birds in the Pacific:
compiled from the bird log kept during the recent cruise of H.M.S. Challenger. Emu,
54:7-28.

Manar. T. a. 1969. Progress in 1967-68 at the Bureau of Commercial Fisheries Biologi-

cal Laboratory, Honolulu. Bur. Comm. Fish. Circ. 321.

McHugh, J. L. 1950. Increasing abundance of albatrosses off the coast of California.
Condor, 52:153-156.

Marr, j. W. S. 1956. Euphausia superba and the Antarctic surface currents. Norsk.
Hvalfangst-Tid., 45:127-134.

IMunro. G. C. 1945. The Laysan Albatross on Kauai. Elepaio, 5:70.

Munro, G. C. 1946. [Field notes.] Elepaio, 6:79.

Murie. 0. J. 1959. Fauna of the Aleutian Islands and Alaska Peninsula. N. Amer.

Fauna No. 61.

Nakamura. E. L. 1965. Food and feeding habits of skipjack tuna, Katsuwonus pelamis,
from the Marquesas and Tuamotu Islands. Trans. Amer. Fish. Soc., 94:236-242.

Ommanney, F. D. 1963. The Fishes. Time Inc., New York.

Rice. D. W.. and K. W. Kenyon. 1962. Breeding distribution, history and populations
of North Pacific albatrosses. Auk, 79:365-386.

Robertson. W. B., Jr. 1969. Transatlantic migration of juvenile Sooty Terns. Nature,
223:632-634.

Salomonsen. F. 1965. The geographical variations of the Fulmar (Fulmarus glacialis)
and the zones of marine environment in the North Atlantic. Auk, 82:327-355.

Sanger, G. A. 1965. Observations of wildlife off the coast of Washington and Oregon
in 1963, with notes on the Laysan Albatross {Diomedea immutabilis) in this area.
Murrelet, 46:1-6.

Sanger, G. A. 1970. The seasonal distribution of some seabirds off Washington and
Oregon, with notes on their ecology and behavior. Condor, 72:339-357.

Seckel, G. R. 1970. The trade wind zone oceanography pilot study. Part VHI: Sea-
level meteorological properties and heat exchange processes July 1963 to June 1965.
U.S. Fish and Wildl. Serv. Spec. Sci. Rept. Fish. No. 612.

Seckel, G. R., and M. Y. Y. Yong. 1970. Harmonic functions for sea-surface tempera-
tures and salinities, Koko Head, Oahu, 1956-69, and sea-surface temperatures,
Christmas Island, 195T-69. Fish. Bull., 69:181-214.

Sorokin, U. L, and 0. J. Koblentz-Misciike. 1958. The primary production of the
Sea of Japan and the part of the Pacific adjoining Japan, during spring 1957. Papers
Acad. Sci. U.S.S.R., Moscow, 122:1018-1020.

Sverdrup, H. U., M. W. Johnson, and R. H. Fleming. 1942. The Oceans. Prentice-
Hall, New York.

Stager. K. E. 1958. A record of the Laysan Albatross from Southern California. Condor,
60:404^405.

Szijj, L. 1967. Notes on the winter distribution of birds in the western antarctic and
adjacent Pacific waters. Auk, 84:366-378.

Thompson. D. Q. 1951. Notes on distribution of North Pacific albatrosses. Auk, 68:
227-235.

Tickell. W. L. N. 1%7. Movements of Black-browed and Grey-headed Albatrosses in
the South Atlantic. Emu, 66:357-367.

Tickell. W. L. N. 1968. The biology of the great albatrosses, Diomedea exu/ans and
Diomedea epomophora. Antarctic Res. Ser., 12:1-55.

Fisher and
Fislier

DISTRIBUTION OF LAYSAN ALBATROSS

27

Tickell, W. L. N., and J. D. Gibson. 1968. Movements of Wandering Albatrosses.
Emu, 68:7-20.

Tickell, W. L. N., and C. D. Scotland. 1961. Recoveries of ringed Giant Petrels,
Macronectes giganteus. Ibis, 103:260-266.

United States Navy. 1966. Pilot chart of the North Pacific Ocean, No. 1401, July
1966. U.S. Naval Oceanog. Office, Wash., D.C.

Waldron, K. D., and J. E. King. 1963. Food of skipjack in the Central Pacific. Proc.

World Sci. Meet. Biol. Tunas and Related Species, FAO Fish. Rept. No. 6:1431-1457.
WiLiiOFT, D. C. 1961. Birds observed during two crossings of the Pacific Ocean. Con-
dor, 63:257-262.

WiLLET, G. 1913. Pelagic wanderers. Condor, 15:158.

Wyrtki, K. 1967. The spectrum of ocean turbulence over distances between 40 and
1000 kilometers. Deut. Hydrog. Z., 20:176-186.

Yocom, C. F. 1947. Observations on bird life in the Pacific Ocean off the North
American shores. Condor, 49:204-208.

Voous, K. H. 1965. Antarctic birds. Monogr. Biol., The Hague, 15:649-689.

Unfortunately, we did not know of the significant report by V. P. Shuntov (Zook
Zhurnal, 47:1054-1064, 1968) until after our paper was in press. His study of the distri-
bution of the Laysan Albatross, based on approximately 800 records obtained at sea over
a 10-year period, is in nearly complete agreement with ours in relation to basic distri-
bution and its correlation with land masses, oceanic currents and primary productivity,
to major areas of concentration, to temperature preferences, and to seasonal movements.
The major difference is that Shuntov found a summer and fall penetration of the western
and southern parts of the Bering Sea by significant numbers of Laysans and lesser num-
bers throughout the Sea of Okhotsk in these seasons. We thank Dr. Isaac Shechmeister of
Southern Illinois University for translating this article for us.

DEPARTMENT OF ZOOLOGY AND SCHOOL OF MEDICINE, SOUTHERN ILLINOIS UNI-
VERSITY, CARBONDALE, ILLINOIS 62901, 9 JUNE 1971.

HABITS OF THE CRIMSON-CRESTED
WOODPECKER IN PANAMA

Lawrence Kilham

I studied the Crimson-crested Woodpeckers {Campephilus [Phloeoceastes]
melanoleucos) in the Panama Canal Zone in February 1965 and from
November 1970 to February 1971, a period which included the end of the
rainy season when nesting began and the onset of the dry season when young
were fledged. The behavior of this species resembles that described by Tanner
(1942) for the Ivory-billed Woodpecker {Campephilus principalis) and has
not hitherto been the subject of any detailed reports, with exception of notes
by Short (19706), as far as I am aware. In Short’s opinion (1970a),
Phloeoceastes should be merged in Campephilus and I have adopted this
terminology.

While the aim of present studies was to learn as much as possible about the
total behavior of C. melanoleucos, the problems raised by its similarity in size
and coloration to the sympatric Lineated Woodpecker (Dryocopus lineatus)
were kept in mind, thanks to the ideas of Cody (1969 ) on why this parallelism
exists. Actual field observations, however, failed to support his interesting
theories, which are dealt with in greater length in a final discussion.

STUDY AREAS

I studied Crimson-crested Woodpeckers in five localities of which three, Madden Forest
Reserve, Limbo Hunt Club, and Barro Colorado Island (BCI), were, for the most part,
mature forests. Of the other two areas, one was of second growth forest 10 to 20 m in
height at Cardenas Village where I lived and the other at Frijoles, an area under partial
cultivation opposite Barro Colorado Island. The Crimson-crested and Lineated Wood-
peckers were sympatric in all five of these localities, as indeed they are in much of South
America.

METHODS OF COMMUNICATION
Instrumental Expressions

Drumming. — Drumming is typically a strong blow followed by short, weak,
vibratory roll, “DA-drrr.” Such bursts usually come at a rate of one to two
per minute, three per minute being a fast rate. This drumming serves a num-
ber of functions. Single “DA-drrs,” given occasionally throughout the day,
enable members of a pair to keep in touch as they travel through woods
together; duets of them continuing for periods of up to 20 minutes may occur
at the height of courtship and just prior to copulation; while louder drumming,
delivered against a resonating stub, is usually related to territorial disputes
and assertions of dominance. This abbreviated drumming of C. melanoleucos.

28

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

29

Fig, 1. Female Crimson-crested Woodpecker drum-taps at rim of recently completed
j nest hole as mate approaches.

which at times can be no more than a single “DA,” appears to be the same as
that described by Tanner (1942) for the Ivory-billed and by Short (1970a and
b) for the Magellanic (C. magellanicus) and other Campephilus woodpeckers
! in South America. Although both sexes of C. melanoleucos drum, males drum
i far more than females during the nesting season.

Pileated Woodpeckers (D. pileatus) (Kilham, 1959) strike a sharp rap with
I their bills against any surface they happen to be on when nervous or excited.
According to Bock (1963), the genus Campephilus is an offshoot, phylogeneti-
cally, of Dryocopus and one might wonder whether the single drumming of
Campephilus is not derived from the rapping of the latter genus. An observa-
tion of Tanner (1942) on the Ivory-billed Woodpecker is of interest here,
I for he noted that “The adults always were disturbed and excited whenever I
I first found a nest.” In addition to giving calls they “often double-rapped or
pounded on stubs or limbs of the nest tree and nearby trees.” Thus, the
drumming was done in the same context as the rapping would l>e done for
j D. pileatus.

' Drum-tapping. — As discussed in a preceding report (Kilham, 1959), most

j woodpeckers tap at a regular and countable rate at the time of excavation of
I a nest hole. Pileated Woodpeckers, on the other hand, have a more rapid

30

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Fig. 2. Female Crimson-crested Woodpecker backs down from nest hole to touch hills
with her mate who reaches up toward her.

roll taking the place of tapping, which I have called “drum-tapping.” Crimson-
crested Woodpeckers drum-tap in the same manner as Lineated and Pileated
Woodpeckers, both at the rim of the nest hole at time of excavation ( Fig. 1),
but also down inside the nest at time of relief at the nest, a habit also described
by Sielmann (1958) for the European Black Woodpecker {D. martins).

Wing noises. — Crimson-crested Woodpeckers can fly silently. They often,
however, make a heavy sound, even in flying short distances, that doubtless
keeps each member of a pair informed when the other moves and in what
direction. Heavy wing noises are a feature of conflicts.

Displays

Bill-touching. — At times of most active courtship, the woodpeckers of a
pair may come close to one another, crests raised and even curled forward,
then fence gently, making contact for roughly half the length of their bills.
This interest in bills at time of courtship may be related to the way a male
pecks down at the bill of the female while copulating. Ivory-billed Wood-
peckers touch bills in courtship according to Tanner (1942) and Allen and
Kellogg (1937) wrote that as a female climbed up a pine toward her mate
“he bent his head downward and clasped bills with her.” Although I noted a

Lawrence

Killiam

CRIMSON-CRESTED WOODPECKER

31

NEST NOV. 1970
NEST JAN. 1971

® KNOLL (Courtship)

® CONFLICTS WITH RIVAL MALE
JAN. 1971

NEST EXCAVATION D.LINEATUS

Fig. 3. Territory of Pair A of Crimson-crested Woodpeckers at Cardenas Village.

I similar bending down on several occasions, as illustrated in Figure 2, I never
I: observed bill clasping with C. melanoleucos.

Vocalizations

Alarm notes. — Notes of moderate disturbance made, for example, when one
f comes too close to a nest excavation are ca and ca-wa-rr-r often repeated. A
sharp, high-pitched ca given alone was the only vocalization heard in several
conflicts between males. Shrill, piping put put puttas given by both males and
females are expressive of high excitement. These may be kept up for minutes
on end. On the whole, however. Crimson-crested Woodpeckers are relatively
silent birds, giving way to alarm notes with far less frequency than the related
Lineated Woodpeckers.

Intimate notes. — These low notes are expressive of closeness of pair bonds,
, being given just prior to coition and at times when one partner relieves the
other at excavating. Variations include ivuk ivuk, ivrr wrr. wun ivun. and uh
I uh among others.

I Main breeding:^ call. — A tree-frog-like kwirr kwirr-ah or squeer squeer-ah-
' hah.

'' Comparisons to other species. — Short (19706) records a three-noted call
j wink-at-chew for C. melanoleucos in Argentina. Vocalizations of C. magellani-
I CHS (Short, 19706) are given in more detail and here the double-noted calls,
j ivieeer and kee-argh (harsher, more drawn out) appear somewhat similar to
I the kwirr-ah and ca-wa-rr-r notes described above for C. melanoleucos.

32

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

COURTSHIP AND COPULATION

The following activities of Crimson-crested Woodpeckers, as well as the
excavation of nest holes, with exception of Pair E, took place in the rainy
season.

Pair A. — The woodpeckers of Pair A frequently came to a knoll IFig. 3) at the edge
of woods by Cardenas Village for early morning courtship and preening, the male (MA)
always to a special place on his tree and the female (FA) to hers. These trees were
about 14 m tall and 10 m apart. Here the two began a duet of drumming at 06:10 on
22 November 1970. After 15 minutes of low bursts, one or two per minute from each,
MA flew to FA’s tree and I heard low notes then as well as five minutes later when FA
moved out onto a horizontal limb. Here she crouched low in a crosswise position as MA
approached. He mounted in full coition, pecking gently down at her bill four or five
times as he gradually fell to the left in establishing cloacal contact.

This copulation suggested that the pair must have a nest nearing completion and on
26 November I was led to it at 16:00 by the sound of FA excavating. She took alarm
and flew out, then drummed on nearby trees as if disturbed. 1 returned again in the late
afternoon. The woodpeckers were feeding in trees close-by when, at 17:20, FA flew to
the hole and clung to its lower rim. When MA alighted a meter below, she drum-tapped
on the rim of the hole (Fig. 1) and as he hitched upward, she moved down to meet him,
bending over to fence bills (Fig. 2) as he stretched upward. All now looked well for
actual nesting. The way a pair of Collared Aragaris ( Pteroglossus torquatus) dispossessed
the woodpeckers of their completed hole 20 minutes later is described beyond.

Five days later, on 2 December, the two Woodpeckers, now without a nest, had returned
to the knoll (Fig. 3). MA drummed at an uneven rate of 11 times in 10 minutes at 06:23,
but FA, on her tree, did not respond. When he flew to her, however, the two fenced
lightly with their bills. FA moved on a less horizontal part of the trunk and crouched low,
but MA, taking no apparent interest in this invitation to coition, flew away. On the fol-
lowing morning MA drummed again, with only one burst in reply from FA. The two
preened in leisurely fashion for 35 minutes, then left. It thus appeared on succeeding days
that, with loss of their nest, the woodpeckers gradually lost interest in courtship.

I now felt there would be little to observe further with this pair when on 15 December
I heard kwirr-kwirra notes by the knoll when MA alighted on the trunk of a slender tree,
to be joined almost immediately by FA, both being at the same level as they bent heads
together to touch bills. The crests of the two were raised to the full and curled forward.
They returned to their original positions, only to bend heads together on the other side
of the trunk to fence again. Both now flew to the knoll and drummed a brief duet before
a longer period of leisurely preening. Had the woodpeckers found a new nesting site as
the renewal of courtship activities suggested? 1 had no further indication of this until 1
January when at the comparatively late hour of 18:45 1 saw the pair on a bare tree near
the knoll in full copulation. From here, after feeding for five minutes, they flew east.
With this direction as a clue I was able to find their nest, in which they were to hatch
young, a few days later.

Pair B. — At 06:10 on 26 November drumming led me to find a male Crimson-crested
Woodpecker on the limb of a dead tree above Madden Forest. A female Lineated Wood-
pecker alighted briefly on the same limb but after she had left, the female Crimson-crested,
whom I could not see, drummed five or six times, then flew to her mate. I heard low
notes, then witnessed full coition lasting possibly 10 seconds. Afterwards the two birds

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

33

preened in leisurely fashion for 10 minutes, then flew to feed in the forest. At 07:00 the
female gave a single kwirr-a. After a pause, the male flew to her, there were more low
notes, and a second copulation, not well seen, followed. This was 35 minutes after the
first one.

EXCAVATION OF NEST HOLES

Trial nest stub. — Not all pairs of Crimson-crested Woodpeckers were able to
find suitable nest stubs. Pair C, for example, had already tried to excavate one
stub when, at 09:25 on 24 December, I found the male carving an entrance in
a second one. His mate remained nearby making querulous wer wer and wiik
wuk notes until she took over the excavating at 09:40. Her interest, however,
waned after five minutes and she circled up the stub, pecking here and there
as if to test the nature of the underlying wood, which was probably too hard
to excavate, before flying away. She thus appeared more critical of the stub
as a nesting site than her mate. Little further progress was ever made with
entranceway and by early Eebruary Pair C had still failed to find a place to
nest. From such observations I came to believe that suitable stubs in this and
other parts of Barro Colorado Island, as well as other localities, were generally
in short supply.

Successful nest stubs. — Both males and females excavated and their greet-
ings at times of changing over were expressive of attachment to the nest hole
as well as to each other. At 10:45 on 26 December, for example, the male at
Nest D drum-tapped when inside the hole with head still visible, made low
notes, then drum-tapped again when his mate flew over to take his place. She
tossed some sawdust from the entrance but spent most of her time looking out.
When Male D returned in 15 minutes, she immediately disappeared to drum-
tap at the bottom of the cavity. He peered in at her several times before sbe
squeezed out by him to fly away. MD then tossed out sawdust. As with ED,
however, he was soon looking out idly and I believed from this and subse-
quent behavior that the nest was ready for egg laying.

The woodpeckers of Pair E were late in excavating in comparison with Pair
D, for they did not begin until late in January. Their hesitancy to use the stub
finally chosen was probably due to the mass of epiphytes at the top, together
with the lianas that might have encouraged arboreal mammals or other un-
wanted neighbors. Tbe pair had, however, carved an entrance by 22 January.
The female did most of the excavating at this nest and change-overs, when
they did occur, were much the same as for Pair I) with one exception. Jliis
was on 31 January. Male E had been excavating when his mate flew to the
hole making low notes. Instead of dropping out of sight to drum-ta|). ME
remained by the hole to meet his mate directly and the two touched bills a
number of times before be flew away.

34

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

NESTING

Greeting ceremonies in the first few days of incubation were much the
same as in the previous period in regard to drum-tapping, but changes soon
became evident when the birds became silent, increasingly undemonstrative,
and no longer looked out from entrances. When MD came to his nest hole at
16:00 on 8 January, his mate swung out of the hole in silence, the two wood-
peckers resting side-by-side below the hole momentarily without other cere-
monies before she flew away.

Times between change overs are long for C. melanoleucos. In waits of one
and a half hours or more I never saw a woodpecker return after leaving.
Skutch (1969), however, in waiting for extended periods at a nest of the
closely related Pale-billed Woodpecker [ C. guatemalensis ) , noted the female
as spending four and a half hours on the eggs and her mate as remaining on
them from 12:15 until dark without being relieved.

Nestling period. — The behavior of the woodpeckers at Nest D changed with
the hatching of the eggs, their greater restlessness being exemplified by the
following observations: On 15 January MD, after looking out from the hole
for five minutes, flew out at 13:45 to preen for a few minutes on an adjacent
tree, then re-entered to brood the nestlings. The longest time he spent away
from the nest in the course of two and a half hours was 10 minutes.

On 22 January ED had been brooding for a half hour when she flew out,
leaving the young unattended for 45 minutes before MD arrived and entered.
ED returned almost immediately, replacing him within a few minutes. Her
attention to the nest was closer than that of her mate on this and succeeding
days, as she would generally stay near the nest when not in it, whereas MD
might, at times, be away for more than three hours.

Other events of special interest at Nest D during the nestling period can be
summarized as follows:

1) Neither parent ever brought visible prey to feed their young. It is con-
ceivable, however, that they might have done so had the young survived
longer, for Tanner (1942) describes Ivory-billed Woodpeckers as carrying
large grubs to well-grown nestlings.

2) ED and MD were both together in the nest on two occasions. Thus, on
30 January MD entered while his mate was inside, only to leave a few minutes
later and on the following day, under similar circumstances, he remained
inside with her for five minutes.

3) MD became increasingly apprehensive as the nesting period progressed,
delaying each entry by much looking about and bowing into the hole, only to
withdraw. Whether the predator that finally destroyed the nest (if predation
was the cause) was in the vicinity I did not know, but on nearly every visit

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

35

to Nest D I did see a pair of Spectacled Owls [Pulsatrix perspicillata) almost
within sight of it.

I found Nest D devoid of activity when I came to it on 7 February. The
entrance was undamaged and I could find no clue as to why the nest had
failed. In looking about in woods nearby I was able to locate the parents and
to follow them for one and a half hours. Their behavior was now much as in
the pre-nesting season, with no sign that they any longer had young to feed.

Tanner (1942) speaks of three nests of Ivory-billed Woodpeckers from
which the young disappeared mysteriously and the nest of the Pale-billed
Woodpecker observed by Skutch (1969) also failed. He noted a large black
snake in the vicinity. It would seem that snakes may be likely predators of
such woodpeckers when entrances are undamaged.

YOUNG AFTER LEAVING NEST

I was watching a male Crimson-crested Woodpecker digging out grubs from
I a well-rotted stub on 22 January on Barro Colorado Island when a second wood-
pecker in adult female plumage alighted 25 cm away. She made no effort to
feed herself but preened lightly, making k-da k-da begging notes much of the
time. The male paid no seeming attention until, on encountering a huge larva
, (4 cm long and 1^4 cm in breadth), he leaned over and fed it to her. Mean-

while, a second female, I believed the mate of the male, joined the other two.
This second female, unlike the first one, dug out her own food. The two
; females got along peacefully although later on I had evidence of a brief con-
flict between them.

The male did not feed the begging female again in the course of the hour
that I followed them. She foraged for herself occasionally but much of the
time she followed him so closely that she was almost at the tip of his tail,
whether he was feeding along the under or top side of a limb. It seemed possi-
ble that she was a young of the year before and while this may seem a long
time for a young one to stay with parents, it does fit a situation described by
Short (19706) for C. melanoleucos in Argentina as well as by Tanner (1942)
who wrote of C. principalis as follows:

“The young birds usually leave or are driven away by the following nesting season,
but the single male that was raised by the John’s Bayou birds in 1938 stayed in that
I territory through the following spring. The female of the pair frequently tried to drive
him away, but he would only dodge, sulk, and return. The old male paid little or no
: attention to his yearling son.”

: The first juvenile I encountered on Barro Colorado was on 51 January

when continued k-arr k-arr disturbed notes attracted me to one at the edge of
a gap in the forest. Its mother in the same clearing gave her k-wirr k-wirr-a
I notes, then flew off. The young one followed and later I found it close beside

36

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

her as she dug for grubs in a dead stub. The only other encounter with
juveniles was on 19 Eebruary 1965 when, as described below, one adult female,
attended by two juveniles, had a confict with a second female.

TERRITORIAL AND AGONISTIC BEHAVIOR

Female vs female. — Two females alighted low on a series of trees on the
morning of 19 February 1965, shifting around trunks as one tried to strike
the other, or made a display of doing so for over 15 minutes. The presence
of several juveniles indicated that the conflict, possibly a territorial one, had
come at the end of the nesting season.

Male vs male. — Sounds of much drumming had come from Territory E on
the morning of 27 December. When I followed these into the woods at 13:00,
I found two males, one pursuing the other in short, heavy-sounding flights
from one to another of four trees centering on a tall stub, to which they often
returned. The stub, although unsuitable in a number of aspects, was large
enough for nesting. When the woodpeckers came to rest, I noted two types of
more direct conflicts: In one that lasted five minutes, one male clung almost
upside down below a large limb, while the other, perched on top, half-opened
his wings each time the first one tried to come around from below. When
the two flew, it was to continue with an even milder type of encounter on a
tree trunk nearby. Here one backed down as the other retreated backward.
Finally both flew in opposite directions with the territory owner going to a
large dead limb where he drummed in slow but resounding fashion for six
minutes. He then attacked the intruder again. All of the fighting was silent
except for two sharp ca notes. The males were still engaged when I left 50
minutes later.

A somewhat different and even milder conflict between males took place on
12 January at Cardenas Village, where Female A was probably incubating
eggs. MA was preening and occasionally drumming at “the knoll” ( Fig. 3 )
on what was usually FA’s drumming tree when, at 07 :0o, a second male ar-
rived on MA’s usual drum tree 10 m away. MA did not appear disturbed. He
continued to preen and drum as before, giving about five bursts to every
single one given by the intruder. The latter clung almost immobile the whole
time. Possibly, being well within the territory of MA, he was intimidated.
This was suggested when he suddenly flew toward MA, then changed his mind
in mid-air, and returned to his original position. Five minutes later he again
flew, but this time in an opposite direction.

The intruder again returned some minutes later to a tree close by MA.
The conflict ended at the knoll when MA left soon afterward, followed in a
minute or two by the second male. This was possibly the first of a series of
encounters taking place on subsequent mornings between the two males.

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

37

The above encounters were all mild in nature. There were no accompanying
vocalizations, no bill-wavings, or for the most part any threat displays, and no
direct clashes such as one can observe among temperate zone species such as
the Pileated Woodpecker (Kilham, 1959). It may be that tropical species,
being under more pressure from predators, cannot afford to attract attention
to themselves when engaged in conflicts. Short ( 1970b ) , however, gives a
description of a more conspicuous conflict between two males of C. robustus.

INTERACTIONS WITH OTHER SPECIES

Collared Aragaris. — The mildness and seeming lack of aggressiveness of
Crimson-crested Woodpeckers was exemplified, in a different context, when
several Collared Aragaris took over the just completed nest hole of Pair A on
26 November. After drum-tapping and bill-touching by the hole, these wood-
peckers had appeared comfortably on the way to nesting when MA entered
the hole to roost for the night at 17:33. He was soon looking out, however,
as if nervous. Seven minutes later he slipped out and moved around to the
rear of the stub, being joined by his mate as a toucan flew to the hole and put
its bill in several times. The woodpeckers made a few low krr notes but gave
no sign of resistance. They simply flew off and as far as I know they never
returned. A feature of this performance was that the toucans did not appear
too confident. They did not roost in the hole on the 26th and when I returned
to the nest stub at 17:25 four evenings later, I found them still chary about
entering, for they rested nearby for 20 minutes as if looking the situation over
before doing so. A few nights later, on the contrary, they arrived at dusk
and entered directly. They had thus won the hole without any show of
aggressiveness.

Reaction to a marmoset. — On 24 February 1965 I watched a male Crimson-
crested Woodpecker feeding in a mass of vines at the top of a tall stub in
company with two marmosets (Oedepomidas ^eojfreyi) . A marmoset came
down a vertical liana on which a woodpecker was working. Neither species
])aid any attention to the other, even though they passed within 5 to 7 cm
of each other on either side of the vine. Crimson-crested Woodpeckers
did, however, become much excited by monkeys on one occasion. This
was when the members of Pair E were excavating a nest not far from a
cage of Cebus monkeys on Barro Colorado on 26 January. Loud screaming
from the cage upset both birds to the extent that they made almost continuous
put-put-piitta notes for 10 minutes.

On the whole, however, I found Crimson-crested Woodpeckers relatively
unexcitable as compared with Lineated Woodpeckers. I heir tameness in fact
was of great aid in observing them. It would seem that J'anrier ( 19 12 I had
a similar exj)erience in noting that Ivory-billed Woodpeckers became used

38

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

to people so rapidly that “in a day or so (they) would pay little or no attention
to one a moderate distance away.”

FEEDING BEHAVIOR

Methods of Foraging. — The feeding behavior of Crimson-crested Wood-
peckers was separable into the following categories:

Pecking. — The uncovering of prey with relatively few blows against bark of super-
ficial layers of wood.

Percussion. — While a woodpecker may deliver many blows per minute in pecking,
not all of these are to uncover prey. Some appear to be exploratory, given here and
there without digging into the wood, either to cause a wood-boring larva to move within
its tunnel and thus reveal its location or to sound out difference in resonance between
a hollow tunnel and solid wood.

Scaling. — When working on limbs that have been dead for some time. Crimson-crested
Woodpeckers may combine pecking with sidewise, glancing blows that dislodge sizeable
pieces of loose bark and other debris that may shower to the ground as the woodpecker
moves along. On the other hand, almost nothing may fall when a woodpecker is working
on the closely adherent bark of a dying limb; the powerful, rapid, occasionally prying
blows involved in its straightforward pecking being sufficient to uncover prey.

Probing. — Putting the bill into natural cavities or clumps of epiphytes, etc., presum-
ably to explore their interstices with their tongues, although these are seldom visible.

Digging. — When working on well rotted stubs for deeper lying prey. Crimson-crested
Woodpeckers may dig cavities 10 cm or more deep, seizing and tossing larger slivers
of rotten wood to the ground as they do so. The sizes of such cavities are usually no
larger than those made by Hairy Woodpeckers (Dendrocopos viUosus) and never as
large as the deep troughs dug by Pileated Woodpeckers in North America. This doubt-
less reflects the fact that conditions of decay and location of insects are different in
tropical climates.

The listing of these categories of feeding and foraging does not provide a
full picture. As pointed out lucidly by Bock and Miller ( 1959 I the Campephi-
lus group of woodpeckers have remarkable adaptations not only in the for-
ward direction of all their toes, but particularly in having legs directed away
from the center of the body in such fashion that the full tarsus can be pressed
against trunks and branches. The result is that such a species as C. melano-
leucos, in whatever position it is working, whether on the underside of a limb,
on the smooth bole of a large tree, or out on smaller branches, appears to be
solidly stabilized for delivering powerful blows.

Feeding of non-breeding pairs in dry season. — Observations on a pair with-
out attendant young, followed for 140 minutes on 24 February 1965 on Barro
Colorado Island, brought out some aspects of feeding when the woods were
relatively free of leaves. The two birds were usually within 15 m and often
much less of each other as they moved through the mature forest feeding at
heights varying from 6 to 25 m, the latter height bringing them close up under

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

39

the canopy of larger trees. Most of their feeding, however, was at intermediate
levels. An almost constant feature with this pair was the greater activity of
the female, for she was not only the first to fly on the six occasions when the
woodpeckers flew from one part of the woods to another, but she also moved
along a greater extent of limbs and tree trunks in feeding than the male. At
one time, for example, both woodpeckers flew to a dead limb 4 m long. During
the next 10 minutes she progressed nearly the whole length of the limb in
knocking off bark and debris while he moved only a fifth as far as he probed
thoroughly in a limited area, which he continued to do after she had left.
His inclination to work one place thoroughly was again exemplified later in
the morning. This time he was on a tree with a relatively smooth bole where
he found large numbers of grubs under a strip of discolored bark and fed on
them for 15 minutes. When any fell, he would press his belly against the bark
to recover them.

Foraging in the rainy season. — The dry season arrived late in Panama in
1971 so that essentially all observations made from November into the latter
part of January were made in the rainy season. They were divisible into two
categories of which the first was in the second-growth woods at Cardenas
Village. Here at 16:40 on 4 January, when Female A was presumably incu-
bating, I found MA working alone on a small semi-dead tree, 3 to 4 m above
the ground and at the level of my eye as I stood on a slope above. At times
he moved out onto branches of 2.5 cm in diameter. Clinging securely by
grasping small branchlets, two of his forward-directed toes on one side and
two on the other, he pecked steadily on the still adherent bark, as if finding

I considerable amounts of prey. At one time, for example, I saw him extract a
larva grub about 3 cm long. At another time he clung to the underside of a
slightly larger branch, his forward directed toes serving well for hanging in
this position. It is likely that insect larva are particularly abundant on the
! underside of limbs and branches where moisture collects and persists longer
than on the uppersides. The male also worked on a limb of 10 cm in diameter.
Here I could see that he delivered three or four powerful pecks in one place,
. then moved along to another, pecking rapidly and nowhere penetrating deeply
into the wood. With a background of watching woodpeckers in the temperate
I zone, I would have thought the branches more suitable for a Hairy or even a
Downy {D. pubescens) Woodpecker, than for a large species such as C.
melanoleucos. Short (1970a) noted C. magellanicns feeding on small branches
I in a similar manner.

Crimson-crested Woodj)eckers are versatile feeders whether in second-
I growth woods, such as those in Cardenas Village, or on Barro Colorado where
I the mature forest contained many large stubs and branches. Methods of
I feeding in these habitats are illustrated in the following examples. 1 ) Feeding

40

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

directly under bark. MA delivered hard blows on the firmly adherent bark
of a dead stub near Cardenas Village and as bits of bark came loose. I
could see tunnels of wood-boring larvae directly below. The woodpecker’s
blows were straight on, followed by a few at slight angles, together with prying
motions. 2) Excavations into wood. A pair of Crimson-crested Woodpeckers
on BCI dug holes 3 to 5 cm deep in a large stub finding not only small grubs,
but also several large ones measuring approximately V2 by 4 cm. 3 ) Tree with
smooth bark. A female fed under strips of loose bark on the unusually smooth
bole of a large tree by splaying her legs well out to the side. 4 ) Possible
feeding on termites. A lone female fed for 40 minutes on a dead stub arising
from a small, understory tree. She dug so industriously into its basal portion
that the upper part broke off and fell to the ground. Later examination of this
portion revealed that it contained many termites along with a few tunnels, all
old, of large larvae.

The foraging habits of Crimson-crested Woodpeckers were easy to observe
for several reasons. First, the woodpeckers would often move from one tree
to the next, finding plenty to look for without taking long flights from one
good tree to another as is often the case with other woodpeckers, such as the
Pileated or Hairy in northern woods; and second, when feeding high up on
dead limbs, they would often move along the underside where one still had a
good view of their activities.

COMPARATIVE FEEDING BEHAVIOR AND INTERACTIONS WITH D. LINEATUS

Crimson-crested and Lineated Woodpeckers fed in the same locations and
occasionally on the same trees on Barro Colorado Island without signs of
hostility or indeed special reactions of any kind.

I heard, for example, vocalizations of both species, then found the four woodpeckers of
two pairs intermixed as they fed among a small group of trees on 24 December. When
the Crimson-cresteds left, the Lineated Woodpeckers moved into the tree where they had
been. Here the male probed into holes and crevices of a dead limb, then moved out onto
a dead branch 2.4 cm in thickness that one would have thought suitable only for a
smaller species. I had noticed a female Lineated Woodpecker doing much probing a short
while before and an impression that this method of foraging was a characteristic habit of
D. lineatiis, more so than of C. melanoleucos, was re-enforced by further observations on
5 February. Thus, at 09:00 I heard both the kwirr-as of Crimson-crested and the wer-wer-
wer notes of Lineated W'oodpeckers coming from close by a trail. Sounds of digging then
led me to a male Lineated. He pecked only briefly, then began probing a spot on the
upper side of a large limb, 15 cm below a decaying branch stub. This was probably a
ramifying area of decay, for the male turned and twisted his head for the next five
minutes, as though reaching into deep tunnels or interstices wdth his tongue, the whole
performance being identical with what I have witnessed with Pileated Woodpeckers on
many occasions. It seemed probable, therefore, that the Lineated Woodpecker was for-
aging on ants and their larvae.

At 09:10 a male Crimson-crested suddenly alighted only a meter below the male

Lawrence

Killiam

CRIMSON-CRESTED WOODPECKER

41

Lineated Woodpecker, As the Crimson-crested Woodpecker hitched upward, neither he
nor the Lineated Woodpecker raised their crests in even mild excitement. When the
two were within 30 cm, the Lineated flew to a limh a meter away, remaining there quietly
while the slightly larger Crimson-crested Woodpecker took over his feeding place. The
latter gave only a few pecks, as though finding nothing of interest, then moved on to
drum once on the broken branch stub, preen briefly, and leave. The Lineated now
returned to continue at his feeding spot for another 10 minutes.

j A number of aspects of this episode were noteworthy. First, the Crimson-
crested Woodpecker had not replaced the Lineated in a supplanting attack,
for there was no sign of hostility, the situation appearing to be one of simple
dominance at a food situation. The Crimson-crested was the larger wood-
pecker and this, plus having a longer, heavier bill, may have explained his
dominance.

A second feature of the episode was that whereas the Lineated Woodpecker
had started making put-air notes when I had arrived, he stopped making these
I notes when the larger woodpecker replaced him, appearing thus, if anything,
to have become calmer, rather than more excited. What was the most signifi-
cant feature of the encounter, however, was the light it threw on the feeding
habits of the two species. The Lineated obviously found much to feed upon in
the one spot, for he was able to feed there actively for a total of 15 minutes,

I quite possibly on ants and their larvae. On the other hand, the tree itself
provided feeding places of a different kind, such as decaying dead limbs,
attracting C. melanoleucos, for I had watched the male and female feeding
here a few weeks before. These observations suggested the two species of
i woodpecker, instead of having the similar “ecologies” needed to support
, Cody’s ( 1969 ) theory, can forage on the same trees for quite different sorts
of prey. While they do undoubtedly overlap in some of their feeding habits,

' as indeed Tanner (1942) showed for Pileateds and Ivory-bills, this is not of
sufficient degree to interfere with their being sympatric.

That the Lineated Woodpecker is specialized is seen most clearly, as is well
discussed by Skutch ( 1969 ) , in its attacks on Cecropias and the colonies of
Azteca ants harbored in their hollow trunks and branches. These trees grow
in abundance nearly everywhere and their prevalence at edges of woods may
explain why Lineated Woodpeckers come to these situations. On 9 January,
for example, I found a male digging into a Cecropia at the edge of the lahora-
I tory clearing at Barro Colorado Island. He worked first on the trunk where
I it was 7 cm in diameter, then on a limb of half that thickness. Although I had
j many more observations on C. melanoleiicos than on I). lineatus. I never saw
I it even alight on one of these fast growing trees which, in general, hear little
dead wood.

) I found it more difficult to observe the feeding habits of D. lineatus than
! those of C. melanoleucos for three reasons, namely that I). lineatus was more

42

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

easily disturbed, often starting put-air notes on seeing me; that it was more
thinly distributed, being only one-third as numerous as C. melanoleucos on
Barro Colorado Island; and finally that, whereas C. melanoleucos usually
foraged from one tree to another close by, D. lineatus, after spending some
time on one tree, might take a long flight to another and was hence easily
lost to further observation. The last two situations suggested that D. lineatus
requires larger feeding territories than C. melanoleucos. Whatever the dif-
ferences between the two species, it was striking that they thrive together
whether in old and mature woods such as at Madden Forest, Limbo, and Barro
Colorado, or the second growth ones at Cardenas Village and Frijoles. It is of
interest here, finally, that Slud (1964) found D. lineatus less common than
C. guatemalensis in Costa Rica.

COMPARATIVE BREEDING BEHAVIOR OF LINEATED WOODPECKERS
AND INTERACTIONS WITH C. MELANOLEUCOS

Skutch (1969) has provided a general account of the Lineated Woodpecker.
Additional aspects based on recent observation are given below to bring out
mainly how it is that D. lineatus and C. melanoleucos can live in sympatry
without undue competition or overlap in any aspects of their lives. Reproduc-
tive isolation is, of course, complete. Not only are patterns of plumage colors
about tbe head different, but also, and this may be of special importance, C.
melanoleucos bas a bright yellow iris while the iris of D. lineatus is strikingly
white. This situation is depicted in color for D. lineatus and C. guatemalensis
by Sutton (1951) . The latter woodpecker forms a superspecies with C. melano-
leucos and is also similar in plumage to D. lineatus with which it is sympatric.
Short ( 1970b ) noted that the eyes of an immature female of C. melanoleucos
were white.

The drummings and vocalizations of C. melanoleucos and D. lineatus are
also different. Thus, in C. melanoleucos the main call is a kwirr-a while in D.
lineatus it is, according to Skutch (1969), a flicker-like wic ivic wic. I have
found, however, that this latter is actually part of a spectrum, becoming at
high intensity a wuk wuk wuk of about 17 notes, falling off at the end, that
one recognizes at once as being similar to the high call of the Pileated Wood-
pecker (Kilham, 1959), while at low intensities the notes become a wer iver
wer that one might never consider as coming from a woodpecker. The drum-
mings differ to an equal degree. Thus, much of the communication between
members of a pair as well as between rivals in C. melanoleucos is by their
peculiar drumming, vocalizations being infrequent. Comparable communica-
tions of D. lineatus.) on the other hand, are more by vocalizations, while the
long rolling drum, again like that of D. pileatus, is used less frequently.

Nest excavation. — Crimson-crested and Lineated Woodpeckers are further

I

Lawrence

Killiam

CRIMSON-CRESTED WOODPECKER

43

Table 1

Simplified Outline of Differences in Breeding and Other Habits of Crimson-crested
AND Lineated Woodpeckers that Permit Sympatry Without Undue Competition*

Differences

C. melanoleucos

D. lineatus

Main breeding season

Last of rainy season and
first of dry season
(Nov.-Jan.)

Last of dry season
(March-April)

Relative size of
territories

Small

Large

Type of stub used

Large (45-50 cm diam.) ;

Stubs or tops of stubs

for nesting (optimal)

substantial

small in diam. (18-23 cm) ;
more risk

Food *

*Larvae of wood-boring
beetles primarily and
possibly termites

Azteca and other ant larvae,
overlaps with C. melanoleucos
otherwise in feeding on
beetle larvae

Temperament

Relatively tame

Easily alarmed

* It should be emphasized that this outline is based on observations of relatively few individuals.

** Special adaptations of feet and legs (Bock and Miller, 1959) make C. melanoleucos especially
efficient at extracting this type of prey. ( See text. )

isolated reproductively by the timing of their nestings, that of C. melanoleucos
I coming at the end of the rainy season and that of D. lineatus toward the end

j of the dry season (Table 1). W. John Smith (pers. comm.), for example,

found a pair of P. melanoleucos nesting at Frijoles on 27 January 1967 not
I far from where a pair of D. lineatus had nested in May 1966, and Chapman
( 1929 ) mentions the young of a pair of C. melanoleucos as leaving their nest
on Barro Colorado in February. Skutch (1969) stresses that the closely re-
lated C. guatemalensis, which replaces C. melanoleucos northward of Panama
and is also sympatric with D. lineatus^ is an unusually early nester. Although
Lineated Woodpeckers nest later than Crimson-crested, they may, in some
cases, start trial nest excavations early in January, as indicated by the fol-
lowing observations: On 2 January I found a pair of Lineated Woodpeckers
excavating a hole in the dead top (Fig. 1) of a living tree, one of the Bom-
I bacaceae. The cavity was already deep but the two birds continued to toss
out sawdust from the entrance until 4 January, when the excavation afipeared
I to have been completed. Yet with exception of a brief view on 5 January 1
} never saw the pair by the hole again. Strong winds came with the beginning

I of the dry season later in the month and on 1 February I found that the top of

j the tree had broken off where the cavity of the woodjieckers had weakened it
' (Fig. 4).

44

THE WILSON BULLETIN

March l‘J72
Vol. 8;, No. 1

c 21cm
D. lineatus

'

"c 45cm

C. melanoleucos

Fig, 4. Contrasting sites of nest excavations of Lineated and Crimson-crested Wood-
peckers. (The entrance hole of the Lineated’s nest having been under the curving arch
of the limb above, is shown as seen from below, looking up.)

On 8 January on BCI a pair of Lineated Woodpeckers were excavating a
hole they had pirated from a pair of the smaller Black-cheeked Woodpeckers
( Melanerpes pucherani) . The hole was in an arching limb 18 cm in diameter
at the top of a tall dead stub. Both members of the pair of larger woodpeckers
could enter their excavation completely by 9 January. The male was still
excavating a week later but on 17 January the entire stub crashed to the
ground.

In summary of these and other observations it would seem that D. lineatus
differs from C. melanoleucos in the locations as well as in the timings of its
nest excavations. Thus, while C. melanoleucos is particular about finding a
large stub ( Eig. 1 ) that will be a secure place to nest and appears wary about
even attempting to nest otherwise, D. lineatus is attracted to inherently more
risky situations, whether in stubs or in dead tops of trees so narrow that the
nest cavity is barely accommodated. Its walls, therefore, are necessarily thin,
offering too little support in case of wind or storm. Advantages of using such
situations, however, must outweigh disadvantages. They may include such
things as freedom from competition with the sympatric C. melanoleucos for

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

45

nest stubs, locations so high above ground as to be less within reach of usual
climbing predators, and in being less attractive in their fragile nature to nest
hole competitors of various species such as Collared Aragari.

Finally it should be noted that this habit of making nest excavation in places
that would seem too narrow and too risky is not confined to D. lineatus. As
previously described (Kilham, 1959) the same situation holds for Pileated
Woodpeckers in central Florida where, in absence of any large trees, they
may nest in narrow pole-like dead pines where a full nest cavity may be sup-
ported by little more than outer bark, Truslow (1967), who happened to be
present at the dramatic moment, has recently photographed the breaking up
of one such nest under only a light wind.

DISCUSSION

The Crimson-crested and Lineated Woodpeckers, whose breeding and feed-
ing habits have now been compared, are a remarkable pair of species in being
alike in size and general coloration, yet sympatric within the same monsoon-
rain forest habitat. Thanks to Cody’s article ( 1969 ) , I became interested in
studying these species concomitantly. If it were true, as Cody claimed, that
these two are so alike in habits that they can coexist sympatrically only by
means of an interspecific territoriality promoted by convergence in size and
plumage patterns, then here was a remarkable biologic phenomenon. Unfortu-
nately, I could find no evidence supporting Cody’s ideas, for I was struck, as
also was Karr (1971), that the two species are mutually tolerant. Every time
I encountered Lineated Woodpeckers on Barro Colorado Island, for example,
they were within the territories of one or another of pairs of Crimson-crested
Woodpeckers under study. At no time did I observe conflicts such as might
arise from mutually exclusive territoriality. The general peacefulness between
the two species was notable not only when pairs happened to be feeding on
adjacent trees, but also on one occasion when a male Crimson-crested, coming
close to a male Lineated Woodpecker, temporarily displaced it from a feeding
spot without show of hostility on the part of either the dominant or of the
submissive species.

Having concluded early that interspecific territoriality did not exist, 1
wondered whether Cody’s theory might not be modified to apply to spacing
out in relation to nest sites. This hypothesis, however, likewise became unten-
able in the light of experience. The two species are divergent in such impor-
tant aspects of their lives as the time of their breeding, the nature of nesting
sites they look for, as well as in their feeding habits, as summarized in Table
1. Such a situation is, of course, the usual outcome of natural selection. Wbat
is unusual, if not very rare, would seem to be interspecific territoriality based
on any long term evolutionary process.

46

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

An interesting example of limited interspecific territoriality among very
closely related woodpeckers is given by Selander and Giller (1959). They
found that, seemingly due to man’s interference with natural ecologic barriers,
morphologically similar members of the same superspecies, Centurus carolinus
and C. aurijrons, met in Austin, Texas, and, in a limited area of sympatry, held
mutually exclusive territories. This situation would appear different from
what must be the historically long sympatry that has existed between C.
melanoleucos and D. lineatus.

From one point of view an instructive example of a species pair comparable
in some ways to the Crimson-crested and Lineated Woodpeckers, and even
more alike in plumage although dissimilar in size, are the Hairy and Downy
Woodpeckers. I have found (Kilham, MS ) that in spite of wide differences in
prey and feeding habits, in type of nesting sites, as well as in the time of onsets
of breeding behavior, these species must still be acted upon by many selection
pressures in common, such as predation, survival over winter months when
trees are bare of leaves, and many others, in relation to which their plumages
represent one of many optimal compromises for survival. While the selection
pressure may differ from tropical rain forest to north temperate woodlands,
the principles of why certain birds are similar in plumage would seem to be
the same.

SUMMARY AND CONCLUSIONS

Reproductive and feeding habits of Crimson-crested Woodpeckers were followed in
mature as well as in second-growth woods of the Panama Canal Zone.

The double drum DA-drrr, characteristic of Campephilus woodpeckers, was a main
method of communication, whether used to express mild alarm, territorial dominance, or
in duets between members of a pair at time of courtship.

Copulations and excavations were seen in November but most pairs had difficulty
finding suitable nest stubs and either began nesting in December or January or, in some
cases, failed to nest.

Territorial conflicts between rival males were marked in January, the intrusions being
largely by males of pairs that were failing to establish nest holes.

Both sexes excavate and the bird excavating drum-taps on the inside or outside of the
cavity on the arrival of its mate. This drum-tapping ceremony is identical in Campephilus
and Dryocopus.

Bill-touching or fencing between members of a pair takes place at the nest excavation
or elsewhere at the height of courtship.

Crimson-crested Woodpeckers become silent and difficult to observe in the incubation
period, sitting on their eggs for prolonged periods without looking out from nest holes.

After hatching, either sex may look out and in the first few days when brooding young,
drum-tap on the arrival of a mate. Prey was never visible in the bills of parents coming
to feed young in the first three weeks.

A bird in adult female plumage, seeming by her begging behavior to be a young one
of the year before, was seen accompanying a pair of Crimson-crested Woodpeckers
in January. The male fed her a large grub on one occasion. Juveniles of recent nestings
were first seen late in January and in February.

Lawrence

Kilham

CRIMSON-CRESTED WOODPECKER

47

Crimson-crested Woodpeckers have remarkable adaptations of legs and toes which
I enable them to cling securely when feeding in such difficult situations as the undersides

I of limbs, small branches, or on boles of large trees. Larvae of wood-boring insects appear

to be their chief prey.

Crimson-crested Woodpeckers live in the same woods and even feed in the same trees
I with Lineated Woodpeckers, which appear remarkably like them in size and general
I coloration. The two species differ in feeding habits, in time of onset of nesting, and in
types of nest sites chosen. No signs of interspecific hostility or territoriality were observed.

I ACKNOWLEDGMENTS

I am much obliged to Lester L. Short for going over my preliminary manuscript and
I also to my wife, Jane Kilham, who greatly aided these studies in finding nests of Crimson-
erested Woodpeckers and helping to watch them, as well as in re-drawing the field
sketches shown in Figures 1 and 2.

I LITERATURE CITED

I Allen, A. A., and P. P. Kellogg. 1937. Recent observations on the Ivory-hilled Wood-
I pecker. Auk, 54:164-184.

' Bock, W. J. 1963. Evolution and phylogeny in morphologically uniform groups. Amer.

I Naturalist., 97:265-285.

I Bock, W. J., and W. D. Miller. 1959. The scansorial foot of woodpeckers with com-
j ments on the evolution of perching and climbing feet in birds. Amer. Mus. Novitates,

no. 1931:1-95.

Chapman, F. M. 1929. My tropical air castle. Appleton, New York.

Cody, M. L. 1969. Convergent characteristies in sympatrie species: A possible relation
to interspecific competition and aggression. Condor, 71 :222-239.

Karr, J. R. 1971. Ecological, behavioral, and distributional notes on some Central
Panama birds. Condor, 73:107-111.

’ Kilham, L. 1959. Behavior and methods of communication of Pileated Woodpeckers.
Condor, 61:377-387.

Selander, R. K., and D. R. Giller. 1959. Interspecific relations of woodpeckers in
Texas. Wilson Bull., 71:107-124.

SiELMANN, H. 1958. Das jahr mit den spechten. Verlag Ullstein, Berlin.

Short, L. L. 1970a. The habits and relationships of the Magellanic Woodpecker.
Wilson Bull., 82:113-240.

Short, L. L. 19706. Notes on the habits of some Argentine and Peruvian woodpeckers
lAves, Picidae). Amer. Mus. Novitates, no. 2413:1-37.

Skutch, a. F. 1969. Life histories of Central American liirds III. Pacific Coast
Avifauna, no. 35:1-580.

Slud, P. 1964. The birds of Costa Rica. Bull. Amer. Mus. Nat. Hist., 128:189.
j Sutton, G. M. 1951. Mexican birds. Univ. Oklahoma Press, Norman.

Tanner, J. T. 1942. The Ivory-hilled Woodpecker. Res. Rept. No. 1, Natl. Audubon
I Soc., New York.

j Truslow, F. K. 1967. Egg-carrying l>y the Pileated Woodpecker. Living Bird. 6:227-
I 236.

I DEPARTMENT OF MICROBIOLOGY, DARTMOUTH MEDICAL SCHOOL, HANOVER. NEW
J HAMPSHIRE. 17 MAY 1971.

TERRITORIAL BEHAVIOR IN SAVANNAH SPARROWS
IN SOUTHEASTERN MICHIGAN

Peter E. Potter

The Savannah Sparrow {Passerculus sandivichensis) is a bird of open
grasslands, bogs, coastal marshes, and tundra. In southeastern Michigan
its thin insect-like song is heard wherever farming has produced pastures
and fallow fields. It migrates south in late summer and fall and returns in
April and early May. For three successive breeding seasons (1965—67) I
observed the territorial behavior in Savannah Sparrows in a field five miles
west of Ann Arbor, Washtenaw County, Michigan. The population ranged
from about 18 pairs in 1965 to 12 pairs in 1967.

METHODS

The study area was measured off in a grid, with tape markers placed along border fences
and metal ground markers at the grid intersections in the field. Song perches were
marked with colored pipe cleaners, some with colored foam plastic balls attached. Adult
birds were netted and marked with aluminum and color-coded plastic bands. Sex was
determined by behavior since there is no discernible difference in appearance. Nestlings
were marked only with aluminum bands. ( Only one bird banded as a nestling later
returned to the study field to breed.) Fifty- two adults were banded in 1965, 12 in 1966,
and 6 in 1967, a total of 70. Seventy-five young were banded in 1965, 29 in 1966, and
26 in 1967, a total of 130. ( Banding in 1966 and 1967 was more selective, aimed at birds
evidently linked to a territory. In several instances, females on their nests were flushed
into nets posted near them. Only one non-resident Savannah Sparrow was caught in each
of those years, contrasted to 19 in 1965. )

I observed the birds mostly on Fridays and Sundays from 06:00 to 12:00. Occasionally,
I made evening visits. In all, I spent 490 hours in observation.

Because Savannah Sparrows spend so much of their time on the ground, it was im-
possible to determine their territorial boundaries where vegetation was dense. “Walking”
the birds around their territories was not feasible since they would leave their territories
when pressed. Neither did many territories touch others, where the males might have
clashed and revealed the borders. It was necessary, therefore, to fall back on the device
of marking the males’ singing perches to provide an approximation of the territorial areas.
When singing was done on the ground, usually during pauses in foraging among the
hummocks of grass, adjacent grass clumps or weed stalks were marked.

Gradually the accumulation of markers described areas the edges of which appeared
to be defended consistently. Furthermore, the birds did not appear to go much beyond
these markers to defend their territories. Thus, the variation between the edges of those
areas described by markers and the actual territorial boundaries seemed slight enough
to make the location of the territories clear and the measurement valid.

STUDY AREA

The study field contained 4.74 hectares (11.72 acres) and was essentially level and
poorly drained. It was bounded on the south by a gravel road and a brushy field, to the
north by cropland, and on either side by wet pastures.

48

Peter E.
Potter

SAVANNAH SPARROW TERRITORIES

49

I

Most of the study field was covered by bluegrass (Poa pratensis) fallen over or blown
down in successive layers to form hummocks 30 to 50 centimeters in diameter and up to
I 30 centimeters high. The bluegrass and interspersed timothy (Phleum pratensis) grew up
to 45 centimeters tall by mid-June. In widely separated locations were slowly-spreading
I circles of sedge (Carex stipata) ; chickweed iStellaria grarninea) was also prevalent.

I The northern half of the field was free of woody plants except for a small copse of
willows iSalix sp.) up to 4.5 meters tall at one place along the northern fence. The
southern half contained scattered clumps of willow iSalix petiolaris) from one-half to
I two meters tall. The field had occasionally been used as pasture for cattle in previous
j years, including the year immediately preceding the study period, but no cattle were
! there during the study period itself. In those three years there was an increase in the
I amount of thistle (Cirsium sp.) , goldenrod (Soli dago sp.), spirea (Spirea sp.) and asters
(Aster sp.) .

ARRIVAL DATES

The earliest recorded dates of the birds’ spring arrival at the field during
the study period were 9 April in 1965 and 1967, and 15 April in 1966. Males
were singing on those dates.

Twenty-two males color-banded in 1965 were first observed in 1966 from
15 April to 13 May, and 17 color-banded males in 1967 from 9 April to 7
May. A color-banded male first seen as late as 21 May 1967 was not seen
again.

In both years most of the returning males ( 20 out of 22 in 1966 and 16 out
of 18 in 1967) arrived within a ten-day period in April (9-18 April 1966 and
15-24 April 1967. )

In 1966 and 1967, the first color-banded females were seen on 1 May and
30 April respectively. The earliest estimated start for nesting in any year
was 30 April 1967. Returning color-banded females were first seen in 1966
as late as 14 June and in 1967 up to 27 May. Usually inconspicuous unless
alarmed by the observer’s proximity to a nest or fledgling, some females could
have been in the field several weeks before being seen for the first time.

TERRITORIAL DEFENSE

Singling. — Males began singing on arrival in their territories or shortly
thereafter. In all three years of the study some singing, however limited, had
begun by 15 April. In two of those years the field was full of song on that
date. In the third year ( 1965 ) full song came on 23 April.

Singing did not appear to be done by other than territorial males. I never
heard a female sing or make any other sound other than a chip of alarm and a
buzz when rejecting the advances of a male.

Songs differed from one bird to another and in one bird’s repertoire, but
I have no detailed notes on this. I did time one singing individual and
recorded 25 songs in four minutes — an average of one song every 9.6 seconds.

I

50

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Borror (1961) found that individual Savannah Sparrow songs last two to
three seconds.

Several birds were usually singing by 06:00 in April. They ceased as late
as 19:40 in late April, and as late as 20:20 by the end of June. Singing tapered
off after 09:00 and the birds were usually still after 12:00. Singing in the
evening was less than in the morning but occurred regularly. It was also less
or absent in strong wind or rain.

Song was sometimes distorted by wind, making the birds difficult to hear
or locate, especially when they sang from behind hummocks on the ground
during pauses in foraging.

Singing decreased by mid- June, since the male stopped singing during the
incubation period and did not resume until the fledglings were on their own.
(He also used the perches less frequently and was less frequently seen. ) When
a nest was lost through predation, the male soon resumed singing.

Singing occurred mostly from perches in thistle, goldenrod and willow, and
on the barbed wire fence around the field. Certain perches were used more
than others.

Fighting. — The ultimate defense of Savannah Sparrow territory is a fight
between males, but fights were infrequent. (No female was seen in a fight or
any other defense of a territory. ) Typically, the two birds rose straight up
about a meter above ground and went back down, breast to breast and
clawing all the way. The fights were of short duration — I never saw a rise
repeated — and the birds quickly went their separate ways. I heard no sound
during the fights.

Chases. — Chases by territorial males were more common than fights, espe-
cially early in the season when the territories were first established. They
ceased with molt.

In all chases in which I was able to identify the pursuer, the chase was
made by the territorial defender and ended at the border or shortly past it.
The pursuer usually made a buzzing noise during the chase. In one instance
the defender rose almost straight up about 6 meters to intercept and chase a
Savannah Sparrow flying over its territory.

The pursuer often ended the chase by flying to a perch in his territory and
making a chipping noise or singing. One pursuer, apparently agitated by the
chase, flew from a grass clump out in his territory to a fence at the border,
then back and forth two more times, singing constantly.

If the chased bird flew through more than one territory, the chase some-
times became a relay event, the first defender stopping at his border and the
neighboring defender taking up the pursuit.

On three occasions a week apart in April, 1967, I saw gang chases involving
as many as five or six male Savannah Sparrows. The first incident began with

Peter E.
Potter

SAVANNAH SPARROW TERRITORIES

51

a two-bird chase, the rest converging and all going down into the grass. The
birds started scattering before I arrived, but I was able to identify four from
their color bands. The second chase involved four birds, only one identifiable.
The third incident involved five or six birds, one or two flying in from as far
away as 15 meters. It broke up quickly but not before a fight occurred.

The location in all three incidents was the same “no-man’s-land” between
several territories. The birds identified were all territorial residents in that
area. I was unable to determine if they were ganging up on a bird from outside
the area — a transient, perhaps, or a new arrival — or whether a single chase
between two area residents excited others into general aggression.

Border-crossings did not always end in chases, perhaps because even Savan-
nah Sparrows have difficulty finding each other in tall grass.

On 15 May 1966, for example, a territorial male flew onto a grass tuft and,
his crown feathers raised, looked around quickly in many directions but
started no chase. Another Savannah Sparrow soon flushed from the base of
of a nearby fence post and flew off, whereupon the first bird, his crest now
down, perched quietly on the fence and no longer looked around so rapidly.

Generally, however. Savannah Sparrows stayed within their territories
throughout the breeding season except when the momentum of chasing an
intruder carried a male into an adjoining territory or when a parent accom-
panied a wandering fledgling across boundaries.

Other defenses, — Most adjustment of borders between the few territories
that touched occurred without either fights or chases. Instead, the opposing
males sang on either side of the line, about a meter apart, silently crowded
each other back and forth across the line, or walked along the line side by
side, a few centimeters apart. There were also combinations of these.

Examples:

1) M-44 was challenged at his border hy another male, M-39. The birds ran side by
side, occasionally buzzing and fighting. At times they were only 30 cm apart and both
singing.

2) I flushed M-64, and he flew to a grassy area at his boundary. He was instantly
met there by M-38 of the adjoining territor>’. Both then walked side hy side, sometimes
only centimeters apart, along their border. At one point M-64 stopped and M-38 walked
on, whereupon M-64 crossed the “line.” M-38 immediately rushed hack at M-64 and
buzzed; M-64 returned to his side and the side-hy-side walking resumed. M-64 occasionally

I sang as he walked. After a few minutes I moved away and M-38 flew to a perch in the
center of his territory and sang, ending the confrontation.

3) M-53 resisted intrusions hy M-40, who had part of M-.53’s territory' as his own the
1 previous year. On one occasion M-40 sang from the ground in M-53*s territory hut was
! escorted hack across the border. That is, M-.53 flew to the ground about 30 cm
, from M-40 and followed M-40 as the latter walked hack into his own territory. There was

no audible sound.

' .Among encounters on fences bordering adjacent territories, one observed 12 May 1%7

52

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

was typical. M-29 and M-33 approached each other, facing first one way, then another
as they perched crosswise on the barbed wire. They fluttered their wings slightly, fanned
their tails, raised their body feathers as if swelling, teetered forward with their heads
lower than their tails, and opened their bills. At times they were only 30 cm apart.

One would hack up after depressing his body feathers, while the other advanced. Then
the action would be reversed. The birds see-sawed a distance of not greater than 1.5 m,
more often within a one-half-to-one-meter span. All was done silently except for a few very
soft buzzes.

The confrontation ended when M-33 hopped up onto a fence post a little farther away
and sang. M-39 hopped down into the grass a short distance in the opposite direction
and began foraging.

Other encounters on fences lacked the buzzing, wing movements and feather-raising,
but the see-sawing and teetering were the same. None of the encounters resulted in fights.

Immunity from defense. — Parent birds apparently could follow their fledg-
lings anywhere without being attacked by territorial defenders. The parents
were very excitable at this stage, both birds (but particularly the male)
perching closer to the observer than usual and chipping rapidly and loudly.

In June, 1966, female F-69 from an adjacent territory, possibly foraging
for her nestlings, perched and chipped in M-64’s territory without being chased
out. But when her mate, M-18, also intruded, M-64 approached him and
buzzed and M-18 retreated to his own territory.

Six days later, however, the situation changed. The nestlings had left the
nest and were being tended by M-18 and E-69. The parent birds again moved
into M-64’s territory. Although I was unable to see whether they were fol-
lowing their fledglings, this time neither bird was bothered by M-64. On the
contrary, M-18 approached M-64 and buzzed.

Interspecific aggression. — Aggression toward birds of other species was ob-
served in only a few instances.

A territorial male was seen chasing a Field Sparrow (Spizella pusilla)
which shifted only a meter or two at each rush but eventually left the territory.

A Savannah Sparrow landed beside a Song Sparrow ( Melospiza melodia )
and buzzed until the latter flew away, but in another case a Savannah Sparrow
flew when approached by a Song Sparrow. In all other encounters, these two
species appeared to ignore each other.

Goldfinches iSpinus tristis) and Bobolinks (Dolichonyx oryzivorus) nested
in the field without being approached. On the contrary, I once saw a Bobolink
chasing a Savannah Sparrow.

I saw no cases of Savannah Sparrows being aggressive toward other animals
except in pursuit of insects for food.

Cessation of defense. — Nesting activity tapered off in late July, accompanied
by lessening and cessation of territorial defense. The females left the study
area, none being seen despite repeated inspection walks throughout all terri-

Peter E.
Potter

SAVANNAH SPARROW TERRITORIES

53

tories. The males went into molt, stopped singing and skulked through the
brush. When flushed, they flew only a short distance and disappeared into the
brush again. Any chipping was low in volume and not persistent. Eventually
the males also left the field.

The earliest date on which molt was noticed during the study period — that
is, when the males first looked ragged — was 17 July. For some males it was
noticed 30 July. In all cases molt was accompanied by a cessation of territorial
activity. In no case was molt seen as long as the male was still tending
fledglings.

I was never able to observe molt in a female. Quite often a female would
appear to be in sleek plumage while her mate looked ragged. Generally the
females left earlier and may have molted during this dispersal.

The cessation of territorial defense throughout the field seemed to occur
within a week’s time except for a few birds still busy with nestlings or fledg-
lings. In each of the three years there came a particular day when I noted
that territorial behavior seemed to have ended. Twice it was on 25 July and
once on 31 July.

DEPARTURE

The females usually left the study area within two weeks after the end of
their last nest, whether the end was from predation or fledging and although
both males and females tended fledglings. While they no longer defended their
territories, the males stayed on as long as a month and a half, the average
being about a month. By 31 July, most had gone, but a few stayed on until
mid-August. One was seen as late as 10 September in 1965.

The last resident birds of 1966 were seen on 14 August. Observations in
1967 ended on 31 July, with four males and three females remaining, repre-
senting only 22 per cent of the full adult population that season. The seven
birds included three pairs with late broods.

In general, the females left gradually through June and July, while most of
the males left the last two weeks in July.

NATURE OF TERRITORIES

Shape. — The territories varied considerably in shape from almost square
to long and rectangular and roughly triangular, with no apparent correlation
between territory shape and success in attracting a mate.

Although the fields adjacent east and west were breeding areas, the
I Savannah Sparrows I observed generally adopted the barbed wire fences not
only as much-used singing perches, but also as territorial boundaries. J he
birds did not cross the fences except when ap})roached by me or for a short
I distance in pursuit of an intruding Savannah Sparrow. 1 also recorded one

54

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

instance in which a female apparently followed her fledglings into the adjacent
field.

One of the two exceptions to adoption of the fences as boundaries was a
Savannah Sparrow which frequently sang from a small sapling about two m
beyond the fence, although the bulk of his territory was in the study field.
Another bird clearly had territories which straddled the fence line in 1965
and 1967.

The fences were observed as boundaries even when they merely separated
open grassland rather than being paralleled on one side by something dif-
ferent, such as a road, a ditch or a thicket.

Nest location. — Nests occurred anywhere in a territory, even at the border.
In 1965 I discovered two nests only 2.2 m apart in adjacent territories. Both
nests were successful.

Size. — Eifty-eight per cent of 62 territories marked during the three years
ranged from 601 to 1200 m“ — about one-sixth to one-third of an acre. Fifteen
per cent were smaller, 27 per cent larger.

The average for the 62 territories was 1,068 m“ (0.26 acre). For the 27
territories in which no nest was found, the average size was 845 m-; for the
35 in which nests were found it was 1,239 m“.

The literature on the size of sparrow territories is limited. What there is
indicates the Savannah Sparrows I observed had territories considerably
smaller than the other species noted. I found reports of territory sizes for
ten species in addition to my own figures for the Savannah Sparrow.

A comparative list follows, all figures translated into square meters:

Savannah Sparrow (Passerculus sandwichensis) — From 120 to 2,920 m", averaging
1,068 nF (0.26 acre). Present study.

Grasshopper Sparrow ( Ammodramus savannarum) — 4,850 to 13,330 m", averaging
8,200 nr ( 2.03 acres) . Smith, 1963.

Baird’s Sparrow i Ammodramus bairdii) — 4,730 m“ (1.17 acre). Cartwright, et ah, 1937.

LeConte's Sparrow (Passerherbulus caudacutus) — 1,020 to 6,300 nr, averaging 3,320
m~ ( 0.82 acre) . Calculated from maps by Murray, 1967.

Henslow’s Sparrow (Passerherbulus henslowii) —Average of 3,238 nP (0.80 acre).
Robins, 1971,

Sharp-tailed Sparrow (Ammospiza caudacuta)- — Female less than 4,047 m" (1 acre),
males not territorial. Woolfenden, 1956.

Seaside Sparrow (Ammospiza maritima) — Nesting area, 5,830 m“; shoreline feeding
area, 4,170 nr ; total, 10,000 m‘ (2.47 acres). Woolfenden, 1956.

Tree Sparrow (Spizella arborea) — 5,580 to 39,100 m^ (1.38 to 9.66 acres). Heydweiller,
1935.

Chipping Sparrow (Spizella passerina) — 4,047 to 6,070 m“ (1 to 1.5 acre). Walkinshaw,
1944.

Field Sparrow (Spizella pusilla) — Less than 3,640 to 8,094 m“ (“less than 0.9 acre”
to 2 acres). Walkinshaw, 1945.

Song Sparrow iMelospiza melodia) — For mainland, 2,000 to 6,000 nr (0.5 to 1.5 acre),

Peter E.
Potter

SAVANNAH SPARROW TERRITORIES

55

Distribution of Territories

Table 1
According to

Size and Presence of Nests

Size (m2)

Territories

without

nests

Territories

with

nests

Total no.
of territories in
size range

% of all
territories

Nests

found

% of territories
in size range
with nests

0-600

8

1

9

15

1

11

601-1200

16

20

36

58

27

56

1201-1800

1

8

9

15

12

89

1801-2400

1

4

5

8

5

80

2401-3000

1

2

3

5

2

67

Totals

27

35

62

101

47

ij Nice, 1937; for lakeshore, 1,250 to 2,750 (0.31 to 0.68 acre), Suthers, 1960; for island,

160 (0.04 acre). Beer, et al., 1956.

Nest occurrence. — Eifty-four Savannah Sparrow nests were found. Behavior
by adult birds indicated the probable existence of 15 more nests, for a total
of 69. Thus the nests found represented about 80 per cent of those believed
to have been in the field.

A breakdown of territories by size and known presence of nests is presented
in Table 1. Only 47 of the 54 nests found are included. The other seven were
in five territories also not included because of inadequate marking or because
the nests were discovered too late to map the territories. Figure 1 shows the
territories for the three years of the study.

As might be expected, most of the nests were found in the size range which
also included a majority of the territories — 601 to 1,200 m“. But a comparison
of the percentages of nest occurrence in the several size ranges revealed a
roughly similar distribution (56 to 89 per cent) except where territories were
smaller than 601 m“. Only one of the nine territories in that range had a nest,
a distribution of only 11 per cent.

I F emale occurrence. — The same pattern of distribution could he applied to

! the presence of female Savannah Sparrows in the territories. This was so
■ because in only nine out of 45 territories in which adult females were known
I to be present were there no nests found, and even in eight of those nine hehav-
i ior of the adult birds indicated the probable existence of nests.

It appeared, therefore, that the size of the territory had some influence on
; the attraction of a female, with territories larger than 600 m- being more
I attractive.

Territorial compression. — Two males experienced severe territorial com-
pression.

In 1965, M-21 attracted a mate, F-23, to a territory originally 890 m- in

56

THE WILSON BULLETIN

March 1972
Vol. 81, No. 1

Fig. 1. Savannah Sparrow territories in field near Ann Arbor, Michigan, 1965-67.
Numbers = identified males. U’s i= unidentified males. Dots = nests. Broken circles
surround nests found too late to map territories. Broken territory at bottom, 1967— Male
38, is estimated from partial sightings.

Peter E.
Potter

SAVANNAH SPARROW TERRITORIES

57

I

I size. Much of this was later used by another male as part of his own territory,
, and M-24’s area shrank to 200 m“. M-24 and F-23 apparently nested once but
I abandoned the field after 26 June. The following year, M-24 returned to the
same spot, established a territory only 360 m^ in size and did not mate.

The other male, M-40, first established (in 1965) a 970 m“ territory, and
F-35 became his mate. Encroachments by other males establishing adjacent
territories compressed M-40’s area first to 360 m“ and then to only 200. Never-
theless, there was at least one nest and probably two. In 1966, however, M-40
returned to the same spot, established a territory only 120 m“ in size and did
not mate. He was surrounded by five other territories, the males all aggressive.

I Neither M-24 nor M-40 returned to the field in 1967.

(The original sizes of their territories in 1965, before compression, are used
in Table 1, since these sizes existed when the females were attracted to the areas
and began nesting.)

! Territorial expansion. — With the exceptions just discussed, early-arriving
[| Savannah Sparrows did not seem consistently to claim large areas that were
! later scaled down by population pressure, although there sometimes was con-
I siderable border adjustment at the beginning. On the contrary, there seemed
to be room between most territories for the small expansion the male frequently
I indulged in at the onset of a second nest.

However, 1 was not able to determine whether part of the old territory was
i abandoned so that the total area remained the same size. This was because
! once his territory was established, each male favored only certain perches.

I Late arrivals (there were attempts to establish new territories even in July)
i would sometimes choose unclaimed areas between territories and attempt to
: crowd their way in, expanding to either side and reducing the sizes of the
[ adjacent territories. If the unclaimed spaces were small to begin with and the
1 attempts at expansion failed, the late arrivals were often gone the next day
hut sometimes stayed as long as two weeks.

Abandonment of territories. — Abandonment by one mate or the other is
impossible to prove except when a missing bird shows up elsewhere. Otherwise,

, predation is assumed to be the cause of disappearance. During this study no
males were proven to have abandoned well-established territories, although
three disappeared, all in 1967. One of them had a mate, which disappeared
nine days before the male and long before the usual departure time.

After having successfully reared a brood in 1966, F-69 followed her fledg-
lings into the adjacent territory of M-6 1 and remained there to mate with him
for a second, successful nest. Deserted M-lo spent the rest of the season singing
in his own territory hut did not accjuire another mate. A similar occurrence
was noted among Field Sparrows by Walkinshaw ( 1915).

I Another female, F-20, disappeared after her first nest in both 1965 and 1966

58

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

with the same male, M-21, although the male remained each time. Oddly
enough, after M-2Us first mate of 1967 (not E-20) disappeared after laying
four eggs, F-20 reappeared to mate with him again for the second nest, which
was successful.

SUMMARY

Territorial behavior of Savannah Sparrows in a field in southeastern Michigan was ob-
served for three successive breeding seasons.

Most males arrived within a 10-day period in mid-April. Females arrived over a one-
month period starting at the end of April. The males established territories immediately,
often returning to the same area of the field claimed in previous years.

Males defended their territories by singing from border perches, chasing intruders,
walking side-by-side along the boundaries with males of adjoining territories or by as-
suming threatening postures face-to-face at the borders.

Birds seldom left their territories except under stress, but adults accompanying fledg-
lings could cross boundaries with impunity.

Fifty-eight per cent of the territories ranged in size from 601 to 1,200 m^ Fifteen per
cent were smaller, 27 per cent larger. There was some enlargement between nestings.

The Savannah Sparrow territories observed were considerably smaller than those of 10
other species of sparrows reported in the literature.

The success of attracting a mate was apparently linked to territorial size, with a better
chance in territories larger than 600 nr.

Nesting activity tapered off in late July, territorial defense ended and the males molted.
The females left the study area usually within two weeks after their last nests were
emptied, through June and July. The males usually remained about a month after the
last nests were emptied, most of them departing the last two weeks in July.

ACKNOWLEDGMENTS

My thanks go to Harrison B. Tordoff for his guidance and encouragement in this study.
In addition, he read the manuscript, as did Harold Mayfield, and both have my gratitude.
Robert S. Butsch made helpful suggestions about mapping the study area. Edwin G. Voss
and Rogers McVaugh assisted with identification of vegetation. James Baird provided
many references, including his own manuscript on the Savannah Sparrow, at the beginning
of my study. Library assistance was provided by Norman Ford and Sheldon Miller of the
Josselyn Van Tyne Library at the Lfniversity of Michigan Museum of Zoology. I am also
indebted to Edwin Aprill, who permitted the use of his field for this study.

LITERATURE CITED

Beer, J. R., L. D. Frezel, and N. Hansen. 1956. Minimum space requirements of some
nesting passerine birds. Wilson Bulk, 68:200-209.

Borror, D. J. 1961. Songs of finches (Fringillidae) of eastern North America. Ohio
Journ. Sci., 61:172.

Cartwright, B. W., T. M. Shortt, and R. D. Harris. 1937. Baird’s Sparrow. Trans.
Roy. Canadian Inst., 21: Part 2:163-197.

Heydweiller, a. M. 1935. A comparison of winter and summer territories and seasonal
variations of the Tree Sparrow. Bird-Banding, 6:1-11.

i

I KiL'r'' SAVANNAH SPARROW TERRITORIES 59

1 Murray, B. G., Jr. 1967. A comparative study of the LeConte’s and Sharp-tailed Spar-
rows with comments on the ecology of sympatric species. Unpubl. Ph.D. thesis, Univ.
j Michigan, Ann Arhor.

' Nice, M. M. 1943. Studies in the life history of the Song Sparrow. II. Trans. Linnaean
Soc. New York, 6:152.

Robins, J. D. 1971. A study of Henslow’s Sparrow in Michigan. Wilson Bull., 83:42-48.
Smith, R. L. 1963. Some ecological notes on the Grasshopper Sparrow. Wilson Bull.,
75:159-165.

! SuTiiERS, R. A. 1960. Measurement of some lake-shore territories of the Song Sparrow.
Wilson Bull., 72:232-237.

Walkinshaw, L. W. 1944. The Eastern Chipping Sparrow in Michigan. Wilson Bull.,
56:193-205.

Walkinshaw, L. W. 1945. Field Sparrow 39-54015. Bird-Banding, 16:1-12.
WooLFENDEN, G. 1956. Comparative breeding behavior of Ammospiza caudacuta and
i A. maritima. Univ. Kansas Puhl. Mus. Nat. Hist., 10:45-75.

2518 E. HAMPTON ST., TUCSON, ARIZONA 85716, 1 MARCH 1971 (ORIGINALLY RE-
CEIVED 6 OCTOBER 1969) .

FLOCKING ASSOCIATES OF THE PINON JAY

Rl ssell P. Balda, Gary C. Bateman, and Gene F. Foster

h-|^HE Pinon Jay [ Gymnorhinus cyanocephalus ) is a noisy, restless bird that
normally forms large flocks. Our investigations of the annual flocking
cycle of this corvid (Baida and Bateman, 1971) showed that several other
species regularly joined and foraged with flocks of Pinon Jays.

In most interspecific flocks of the North Temperate Region reported on
to date (Odum, 1942; Wing, 1941; Austin and Smith, in press; and the exten-
sive review hy Morse. 1970 ( the species involved are mainly insectivorous,
flocks form primarily in the fall or winter, and the “flock leaders” or “nuclear
species” are not present in overwhelming densities compared to the associate
species. By contrast, this report deals with five associate species that join
relatively large flocks of Pinon Jays: Hairy Woodpecker { Dendrocopos

villosus). Downy Woodpecker {Dendrocopos pubescens ) . Red-shafted Flicker
iColaptes cafer) . Clark’s Nutcracker { Nucifraga columbiana ) , and Starling
iSturnus vulgaris). The Pinon Jay flock is maintained in a number of forms
throughout the year, thus permitting interspecific association the year around.
The main foods of the Pinon Jay during the fall and winter months when
attendant species are most numerous are seeds of ponderosa {Finns ponder-
osa) and pinon ( P. edulis) pine, and occasional arthropods ( pers. observ. I .

The efficient procurement of food has often been used as at least a partial
explanation for flocking (Miller, 1921; Rand. 1954; Short, 1961; Morse.
1970). Our observations were made on two Pinon Jay flocks, one on its un-
disturbed home range and the other when it visited a local feeding station
where food was diverse and super-abundant. Comparisons were made of the
foraging and agonistic behavior of the jays and associates in both situations.

STUDY AREAS AND PROCEDURES

We studied intensively a flock of about 250 Pinon Jays on a home range of eight square
miles located 10 miles NE of Flagstaff, Arizona for over 480 hours from February 1968
through January 1971. Movements, foraging sites (ground, trunk or branch, tip of foli-
age), and intra- and inter-specific social interaction were recorded. At periodic intervals
foraging sites were recorded hy counting all birds foraging at each site. Six hundred and
forty-nine counts of the entire flock were made in this way. Aggressive encounters, either
“supplantings” (overt chases) or “displacings" (retreats) were recorded (after Willis.
1966). We also noted reactions to potential predators and stuffed Great Horned Owls
( Bubo virginianus) .

The third author has a 0.25-acre feeding station which was visited almost daily by a
flock of about 70 Pinon Jays for the past five years. On some fall and winter days the
flock visited the station up to four times daily; during spring and summer groups of
young and adults often spent hours at the station. A number of different foods including

60

Baida, Bateman
and Foster

pinon jay flocking associates

61

Table 1

Foraging Locations of Members of the Large Pinon Jay Flock

Year (in per cent)

Throughout the

Foraging

Location

Jan., Feb.,
March

April, May,
June

July, Aug.,
Sept.

Oct., Nov.,
Dec.

Ground

40.0

59.4

48.9

39.7

Foliage

31.8

23.3

42.1

35.6

Crevices

29.1

12.8

4.1

24.7

Hawking In Air

0.0

4.4

4.9

0.0

Total Number

of Counts Made

213

172

116

148

mealworms, sunflower seeds, Spanish peanuts, commercial pigeon grain, bacon grease-
bread crumb-popcorn mix, white millet, pinon pine seeds, raisins, and suet were always
available at the feeding station. Qualitative notes were kept concerning the behavior
and aggressive interactions of the Pinon Jays and four of the associates. The Clark’s
Nutcracker did not visit the feeding station.

FLOCKING CYCLE OF THE PINON JAY

Descriptions of interspecific flocks often include a designation of one or
more species as nuclear species without adequately describing the movements
and behavior patterns of these important species in mixed flocks. We have
described the flocking cycle of the Pinon Jay elsewhere (Baida and Bateman.
1971). Here we will only summarize and enlarge on behavior patterns essen-
tial to understanding the role of Pinon Jays as a nuclear species in mixed
flocks.

Fall and early winter. — During this period blue adults and gray first-year
birds formed a loosely organized flock which foraged primarily in ponderosa
pine forest. During early morning feeding the flock moved at an average rate
of about one mile per hour. Short flights below tree-top level advanced the
birds in either leapfrog fashion or as a broad front with all members simul-
taneously moving in one direction. Longer flights taken over large meadows
often consisted of rolling and swirling movements and were accompanied by
loud calling of the flock members. Flocks moved up to 13 miles })er day while
foraging. In the forest some of the flock walked on the ground, either
probing for insects and/or pine seeds or caching pine seeds, while other mem-
bers of the flock foraged off the ground. Some of these gleaned in the foliage,
hammered open pine cones to extract seeds or tore out the tender new growth
at the tips of the branches. I he rest of the birds j)icked food items out of
crevices on the trunks and branches, or hammered vijiorouslv to flake bark to

62

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Table 2

Number of Individuals and Frequency of Occurrence

THE PiNON Jay Flock

of Attendant

Species with

Jan., Feb.,

April, May, J

lily, Aug.,

Oct., Nov.,

March

June

Sept.

Dec.

n = 49*

n = 77

n = 29

n = 64

Hairy Woodpecker

Average Number

(when present)

5(2-7)=*=*

1(1)

0

4(1-7)

Frequency of

Association (%)

100***

14

0

88

Downy Woodpecker

Average Number

2(1-3)

1(1)

0

1(1-2)

Frequency of

Association

80

6

0

42

Red-shafted

Flicker

Average Number

6(4-9)

5(3-7)

2(1-4)

5(3-9)

Frequency of

Association

100

71

62

81

Clark’s Nutcracker

Average Number

1(1-2)

2(1-3)

9(6-15)

7(4-12)

Frequency of

Association

12

16

45

67

Starling

Average Number

7(3-14)

9(5-16)

0

4(2-7)

Frequency of

Association

39

74

0

28

* Number of visits.

** Range.

*** Per cent of visits when associates were present.

extract food (Table 1) . All five associate species foraged with the large Pihon
Jay flock at this time (Table 2) .

During this period, the feeding station was visited from one to four times
daily by a flock of 70 Pihon Jays. While at the station the birds fed on pihon
seeds, bacon grease-bread crumb-popcorn mix, peanuts, sunflower seeds, suet,
and mixed small grains in that order of preference.

Winter and early spring. — During courtship which commenced in mid-
December adult blue birds radiated out in pairs from the feeding flock leaving
the gray first-year birds plus a few blue birds to forage as a unit. The foraging
flock varied in size from 35 to 70 birds. The foraging birds spent about equal

Baida, Bateman
and Foster

pinon jay flocking associates

63

time on the ground and in the foliage. The birds feeding at arboreal sites
divided their activities almost equally between foliage gleaning and cone
feeding, and crevice picking and bark flaking. The entire flock reassembled
periodically and moved to a new feeding location at a loud rapidly repeated
krawing signal given by most individuals in the feeding flock. The resultant
din could be heard for over three-quarters of a mile. During the nest building
period the flock fed as a unit in the morning and evening. However, small
groups of 4^12 birds often formed autonomous feeding units. Throughout
the incubation period the main flock was divided into incubating females, a
flock of adult males seeking and bringing food to the females and a flock of
gray yearling birds. This latter subunit foraged quietly and moved rather long
distances per flight.

When nest building began the visits of the smaller flock to the feeding sta-
tion diminished to one each morning and evening. Small groups of jays,
however, visited the station throughout the day. Later, males visited the
feeding station regularly.

Late spring and summer. — After the young fledged, family groups of adults
and juveniles foraged together as a unit. Adults failing in their first nesting
attempt formed smaller nesting colonies and subsequent family-group feeding
flocks. By late July the single winter flock was divided into a flock of year-
old birds that did not breed, and five or six independent feeding groups. In
late July or early August these flocks moved into the pihon-juniper woodland,
where the birds opened pinon pine cones, extracted seeds and carried them
into the ponderosa pine forest where they were cached. From this time on the
birds remained together as a large flock.

ANTI-PREDATOR BEHAVIOR

Protection from predators is often described as a benefit of inter- and intra-
specific flocking (see Morse, 1970 for discussion). Pinon Jays have two be-
havioral mechanisms which can be termed anti-predator behavior. 4 hese are
in addition to the protection afforded the birds by their mere presence in a
flock ( Allee, 1938; Tinbergen, 1953).

Sentinels. — Throughout the year each subflock (feeding grou}); gray year-
ling flock) and the entire flock when assembled was commonly surrounded
by sentries as reported by Cary (1901). The number of sentries was rather
constant around feeding aggregates and the yearling flock (3-5 birds) hut
varied greatly (3-12 birds) around the large feeding flock that existed during
the non-reproductive period. Sentinels were positioned at high vantage j)oints.
either exposed or concealed in foliage. At the a|)proach of an aerial or terres-
trial intruder the sentinel(s) gave a loud rhythmic krawk-krau-krawk which
was often repeated. On occasion, a ground-feeding bird also gave this warning

1

64

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

call. This call was often sufficient to cause an immediate cessation of feeding
and flight of all individuals up into the trees. During these rapid ascents, birds
flew in all directions and it would seemingly be difficult for a predator to focus
on and capture an individual. If the warning call was not repeated the flock
resumed feeding. Individuals foraging in the trees when a warning call was
given simply stopped feeding and remained still. The associate species re-
sponded to the warning calls in the same manner. Even though Steller’s Jays
did not participate in the activities of the mixed flock they responded to the
warning calls. Pihon Jays in turn responded to the shook call (Brown, 1964 I
given by the Steller’s Jay at hawks or owls.

Mobbing,. — After the rhythmic warning call was given a number of birds
(3-15) including the sentinel! s) often approached the intruder, circling it
if it was perched or on the ground. If flying or running the intruder was chased.
During this performance the mobbing Pihon Jays called loudly, often at-
tracting numerous other birds including Steller’s Jays, Red-shafted Flickers,
Grace’s Warblers, Chipping Sparrows, Acorn Woodpeckers, and j uncos.
Hawks and owls that flew off in response to this harassment were always
chased by the Pihon Jays. The Sharp-shinned Hawk {Accipiter striatus) and
Cooper’s Hawk {Accipiter cooperii) often evaded the jays by flying an
erratic but rapid course then landing and sitting quietly in a camouflaged
location. Red-tailed Hawks {Buteo jamaicensis) and Rough-legged Hawks
(Buteo lagopus) usually left the area by gaining elevation rapidly and then
moving off. Great Horned Owls, however, seldom flew long distances and
could not evade the jays. Consequently, Pihon Jays often mobbed them for
up to 45 minutes.

FLOCKING ASSOCIATES

The following accounts are only for the five attendant species ( Moynihan,
1962) which regularly occur with the Pihon Jay (passive nuclear species, cf.
Moynihan, 1962 ) flock at least for a portion of the year but are not important
for the maintenance of the flock.

Hairy Woodpecker. — One to seven individuals of this species were constant
members of the jay flock from late October through early March (Table 2).
An occasional individual accompanied the non-breeding flock during the
spring and early summer. During this woodpecker’s nesting period it did not
associate with the flock. Nesting alone, however, cannot explain its seasonal
appearance, as it left the flock before it began courtship and did not enter the
flock until well after all its nesting duties were completed. During the period
of association, however, the foraging pattern of the Pihon Jay was similar to
that of the Hairy Woodpecker.

During fall and winter the jays spent considerable time searching the deep

Baida, Bateman
and Foster

pinon jay flocking associates

65

crevices of the ponderosa pine trunks, hammering and flaking bark to extract
food from old dead branches and stumps, and extracting seeds from ponderosa
pine cones. Whether foraging alone or with the jay flock. Hairy Woodpeckers
used these same sites. Stallcup (1969 ) reported Hairy Woodpeckers spending
64.5 per cent of their time extracting seeds from ponderosa pine cones in
Colorado. Stallcup’s figures indicate that Hairy Woodpeckers spent about 83
per cent of their time foraging in the three sites listed above for the Pinon
Jay. He noted that feeding on cones occurred mainly from mid-December
through February, the very time these woodpeckers associate with the Pinon
Jay flock in central Arizona. He reported as did Morse (1970) that the Hairy
Woodpecker foraged throughout the winter in mixed flocks. Short ( 1961 )
reported the Hairy Woodpecker as a member of mixed flocks in Oaxaca,
Mexico.

Hairy Woodpeckers were seen with the jay flock from sunrise to sunset
and remained within the flock as it moved about in the forest and woodland.
Interaction at foraging sites was minimal except at pine cones, where the jays
successfully drove off the woodpeckers. Of 29 aggressive interactions ob-
served, single jays or groups of jays were able to supplant the Hairy Wood-
peckers 20 times. Nineteen of these encounters occurred at pine cones. Hairy
Woodpeckers supplanted jays on 9 occasions. At other feeding sites wood-
peckers of this species were always displaced by groups of seven or more jays.

During the short movements of the jay flock, the Hairy Woodpeckers
always followed the Pinon Jays. The woodpeckers did not follow the flock
when it made longer flights across fields, but remained in the trees at the edge
of the field, calling loudly as the flock departed. Once, after the flock crossed
a field one-quarter mile in width, three Hairy Woodpeckers rapidly flew
around the edges of this small field to rejoin the jays. We have followed
individual woodpeckers that spent four consecutive hours and traveled at
least five miles with the flock.

At the feeding station, resident Hairy Woodpeckers fed alongside the Pinon
Jays until the jays became too numerous at one location. Then displacement
occurred and the woodpeckers perched silently in the trees until the jays left
the station. The jays clearly dominated the woodpeckers; on one occasion an
adult Pinon Jay took eleven peanuts, consecutively, from the hill of a Hairy
Woodpecker. The woodpeckers did not come to the feeding station with the
jays nor did they leave with them.

Downy Woodpecker. — This species associated with the jay flock during
roughly the same months as did the Hairy Wood|)ecker (Jahle 2). Its for-
aging mode was somewhat different, however, as it spent most of its time on
the trunks and branches of the ponderosa pines and on the dead trt‘es. where
it gleaned and flaked hark in search of food. Often it picked through piru‘

66

THE WILSON BULLETIN

March 1972
Vol. 81, No. 1

cones on the ground, but it seldom worked on cones up in the foliage. Downy
Woodpeckers occur in low densities in this area; consequently, more than three
individuals were never seen with the jay flock at one time. Of 14 interactions
between jays and this woodpecker, the latter was displaced 12 times and sup-
planted twice. Seven of these interactions occurred while this woodpecker
fed on some object either on the ground or a short distance from it. Most
direct conflicts were avoided because the Downy Woodpecker managed to
stay away from Pihon Jays when they fed close together in groups. In other
respects this species acted similarly to the Hairy Woodpecker. The calls of
both species evoked no noticeable reactions from the jays.

At the feeding station the Downy Woodpecker did not feed at its usual sites
when jays were present. It always left the area when the jays entered the
station and returned when the jays left.

Red-shafted Flicker. — Flickers were the most regular associates of the Pihon
Jay flock. Even during their breeding season a few flickers were almost always
with the non-breeding gray bird flock ( Table 2 ) . During fall, winter, and
spring as many as nine individuals were in constant association with the jay
flock. One individual that was specifically followed spent seven hours with
the jay flock and moved about nine miles with it.

The Red-shafted Flickers spent most of their time foraging on the ground
among the jays. Their soil-probing activities greatly resembled those of the
Pihon Jay. During slow movements through the forest and woodland the
flickers flew with the group and were never segregated at the periphery or
rear of the flock. During the winter months. Red-shafted Flickers spent con-
siderable time probing into decaying logs for immature insects. This activity
strongly resembled that of the Pihon Jay when caching food in these sites.
Aggressive encounters were observed when jays and flickers foraged on the
ground; groups of jays were observed driving flickers from cache sites in
decaying logs. The jays either pointed their bills at the flickers or flew up at
them. When a single jay came in contact with a flicker (n = 48 ) Pihon Jays
were displaced or supplanted 46 per cent of the time, while jays dominated
flickers 54 per cent of the time. When the jay flock moved over large fields
some flickers often accompanied them, but others stayed behind, calling loudly
as the flock departed. When sentry jays along the edges of the feeding flock
gave their rhythmic kratvk-kraw-krawk, signaling the approach of a potential
predator, the flickers responded immediately by flying up into the trees in
the same manner as the Pihon Jays. When the warning calls subsided, the
Red-shafted Flickers returned to foraging on the ground with the jay flock.
Thus, their movements between feeding sites, as well as their movements within
the flock when it was stationary, were carried out in synchrony with the Pihon
Jays and in a similar fashion.

Baida, Bateman
and Foster

pinon jay flocking associates

67

During the non-breeding season the Red-shafted Flickers appeared to be
paired, a male and a female often foraging near one another. On one occasion
in May, a feeding group of jays moved through an area where a pair of flickers
was excavating a hole. The birds stopped working, flew into the aggregate,
and foraged with them for at least the next hour.

At the feeding station Red-shafted Flickers fed near the jays but did not
enter or leave with them. The flicker used bill pointing and thrusting to sup-
plant Pinon Jays when it was not badly outnumbered, however a flicker
always retreated from groups of 11 or more jays.

Red-shafted Flickers are strongly attracted to Pinon Jay flocks (Table 2),
and during the non-breeding season it was rare to find a solitary flicker or
pair of flickers far from the jay flock. J. D. Ligon (in litt.) observed the
same phenomenon in New Mexico. Short (1961) described the Red-shafted
Flicker as an irregular attendant of mixed flocks in Oaxaca, Mexico. Its be-
havior in the vicinity of Pinon Jays appears to be quite different.

Clark’’ s Nutcracker. — Nutcrackers descended the slopes of the San Francisco
Peaks in late August to collect pinon seeds and carry them up the mountains
to about 10,500 ft, where they were cached. During this period of seed col-
lecting the nutcracker opened the green cones in such a manner that in poor
light it was impossible for us to distinguish nutcrackers from Pinon Jays. The
jays and nutcrackers worked on the pinon cones in close association, yet no
aggressive interactions were noted. Johnson (1902) commented on such an
association in central Utah. On one occasion a yearling Pinon Jay watched
from a distance of about one meter as a Clark’s Nutcracker opened a cone.
At intervals spanning seven minutes the young jay fluttered its wings and
begged softly while facing the nutcracker. The latter did not react to this
begging. As the jay flock moved between feeding sites up to 15 nutcrackers
moved with the flock. They responded to the danger krawks of the Pinon Jay
by dropping the cones they were extracting seeds from and flying up to the
tops of trees. They returned to seed collecting when the jays did. Twice the
jay flock left the woodland and flew more than two miles to a watering hole,
with eight Clark’s Nutcrackers accompanying them. During these flights,
the low throaty calls of the nutcrackers could be distinguished from the krawks
given by the jays. The nutcrackers were always in the rear half of the flock
during these flights.

During the spring and summer of 1969 from one to three nutcrackers were
often with the yearling flock and also with feeding groups. I he usual raucous
calls given by nutcrackers during foraging and flight were not heard from
these individuals. While foraging on the ground, thev j)erformed |)robing.
insect capturing, and seed opening much as did the Pinon javs.

Starling. — Beidleman and Enderson (1961) first described tlu‘ associalioti

68

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

of Starlings with a flock of Pihon Jays in Colorado. In central Arizona, from
3 to 16 Starlings were associated with the jay flock during March, April, and
May, and again during October and early November. Most Starlings left the
jay flock during the nesting period and again in early winter when they be-
came rare in rural central Arizona and conversely very common in the cities.
Throughout the spring and summer months Starlings nested within the home
range of the Pihon Jay flock but did not associate with it.

In late winter of 1968 the Starlings were first observed with the Pihon Jay
flock when the male jays were roosting as a group and the females were incu-
bating. During this period the Starlings roosted in holes, and on three morn-
ings they stayed in their holes until the male jays called loudly and moved
out of the forest to feed for the first time. The Starlings’ initial response to
these calls was to look out of the holes, squawk loudly, and fly directly to the
flock of feeding jays.

Late in the winter of 1969 Starlings were first noted in the Pihon Jay flock
at the time courtship activities had commenced. After feeding in a very
deliberate fashion with the jays on the ground for an hour in the morning,
the Starlings began courting. Pairs segregated from the jay flock and courted
high in the foliage and examined old woodpecker holes. The Starlings’ initi-
ation of courtship agreed closely with the beginning of the daily courtship
of Pihon Jay pairs. Courting activities were noted for six to ten Starlings
each morning, and indicate not only a strong attraction to the jay flock, but
also a close synchronization of daily events. The synchrony may be coinci-
dence but also suggests the Darling effect ( Darling, 1938 ) .

During foraging the Starlings walked slowly and probed for seeds and
insects in the same manner as the jays. Not only was their gait similar to that
of the Pihon Jay, but in short flights made between feeding sites the Starlings
displayed a very similar pattern of flight. At take off, both species beat their
wings rapidly, but during sustained flight strong wing beats alternate with
gliding. Neither of these species undulates in flight as do most woodpeckers,
as the wings are partly outstretched during the glide phase of the flight. Jen-
sen (1926) and Wetmore (1920) have pointed out these behavioral similar-
ities. Under cloudy conditions, or when the jays and Starlings moved through
heavy foliage, it was difficult to tell them apart.

Aggressive encounters between Pihon Jays and Starlings were not common
as a Starling was not easily displaced by the mere presence of a Pihon Jay.
Of 51 aggressive encounters observed, the Pihon Jay supplanted or displaced
the Starling 57 per cent of the time; at least five other encounters resulted in
both individuals leaving the area.

At the feeding station Starlings associated with the jays from November
through mid-April. During the early winter. Starlings commonly entered

Baida, Bateman
and Foster

pinon jay flocking associates

69

Solitary Species Occurring

Table 3

IN THE Habitats used by Pinon Jays

Species

Mean Weights (g)

Selasphorus platycercus

3.4**

*Colaptes cafer

110.9

Sphryapicus varius

50.7

*Dendrocopos villosus

64.3

*Dendrocopos pubescens

27.8

Tyrannus vociferans

47.0

Contopus sordid ulus

13.7

Tachycineta thalassina

10.6

Cyanocitta stelleri

113.0

Purus gambeli

28.2

Sitta carolinensis

18.1

Certhia familiar is

7.8

Regulus calendula

6.5

Lanius ludovicianus

47.0

Dendroica auduboni

12.6

Dendroica graciae

7.8

Vireo solitarius

17.0

Piranga ludoviciana

29.7

Piranga jlava

37.6

Chondestes grammacus

26.1

Spizella passerina

13.2

Total Number of Species = 21

Number of Associates r= 3

* Indicates associates of Pinon Jay flocks.

** Sources for weights in this table are Baldwin and Kendeigh (1938), Hartman and Brownell
(1961), Miller (1955), Poole (1938), Salt (1957), Hubbard and Ligon (in litt.). Whenever
possible weights were obtained from specimens in the Museum of Northern Arizona and the
Northern Arizona University Museum of Vertebrates.

and departed from the station with the jay flock. However, in late winter and
early spring Starlings were much more prone to stay at the station. Early
on winter mornings Starlings gathered just outside of the station but would
not enter until the jay flock entered. If the jays did not appear by 09:30
the Starlings left without feeding at the station. When feeding at the station,
Starlings mingled with even the largest groups of Pinon Jays and were not
displaced.

On two occasions during the winter of 1969, groups of Pinon Jays were
seen associating with an urban flock of Starlings. On both occasions, the
flocks contained about 55 Starlings and eight to ten yearling Pinon jays. I he
flocks moved silently through a forested area.

70

THE WILSON BULLETIN

March 1972
Vol. 84, i\o. 1

Table 4

Gregarious Species Occurring in the Habitats used by Pinon Jays

Species

Mean Weights ( g )

Zenaidura mucroura

122.8**

Melanerpes jormicivorus

66.0

Eremophila alpestris

43.0

Corvus corax

969.0

Conus brachyrhynchos

479.0

*Nucifraga Columbiana

142.2

Psaltriparus minimus

5.8

Sitta pygmea

9.9

T Urdus migratorius

80.7

Si alia mexicana

24.6

Sialia currucoides

34.7

Bombycilla cedrorum

32.9

*S turn us vulgaris

81.9

Sturnella magna

145.0

Molothrus ater

50.5

Euphagus cyanocephalus

64.8

Hesperiphona vesper tina

53.6

Carpodacus cassinii

27.5

Spinus pinus

12.2

Spinus psaltria

10.4

Junco hyemalis

21.0

Junco oreganus

17.4

Junco caniceps

19.7

Total Number of Species = 23

Number of Associates = 2

* Indicates associates of Pinon Jay flocks.
** Same as Table 3.

DISCUSSION

Of the five species that associated with the jay flock, three are usually
solitary, whereas the other two are often found in intraspecific associations
(pers. observ.; Tables 3 and 4). Some of the species listed as solitary in
Table 3 form intraspecific flocks at times of the year when not in the vicinity
of Pinon Jays. Moynihan (1960) suggests that “many but not all species”
that tend to form intraspecific flocks may also form interspecific flocks. Our
data show, however, that 14 per cent of the solitary species and 9 per cent of
the gregarious species that come in contact with the jay flock do associate
with it. Innate social attraction cannot be used to explain interspecific flock-
ing with Pinon Jays.

Balila, Bateman
and Foster

pinon jay flocking associates

71

The ability of associate species to mingle and remain with the Pinon Jay
flock is probably enhanced by the lack of intraspecific aggression among
Pinon Jays. At any one time, less than 5 per cent of the jay flock was
involved in intraspecific hostile behavior. Pinon Jays displayed similar ag-
gressive behavioral patterns both intra- and interspecifically. These entailed
crouching slightly, pointing the bill at the agressee and lunging, or flying up
at an approaching intruder with legs extended and calling loudly. A direct
thrust with the bill is also used to supplant other birds. These patterns could
be easily learned and adjustments readily made. The Red-shafted Flicker and
Starling used these same general agonistic behavior patterns to displace
Pinon Jays. If the aggressive behaviors are easily learned or already in the
behavioral repertoire of the species, actual combat that can result in injury
and/or exhaustion is reduced or avoided (Moynihan, 1962). Once an inter-
specific association is established, the Pinon Jays tolerate the associate
species and act with the same low level of aggressiveness towards them as to
conspecifics. Therefore the associate species can efficiently reap what benefits
are available without expending undue energy. In this regard, the Starling
which arrived in northern Arizona in the early 1960’s (pers. observ., G. F.
Foster) has had only 10 years to learn and adjust to the behavior patterns of
the Pinon Jay. Yet in many respects the Starling has the highest degree of
behavioral compatibility with the jay flock. This must be due to the behavioral
plasticity or preadaptation of this species.

The numerically superior Pinon Jay is also the socially dominant species
in mixed flocks, in part because with superior numbers it can displace those
associates individual Pinon Jays could not dominate. The associate species
rank in an interspecific hierarchy ( based partly on compatibility and tenacity
when faced with large numbers of jays) as follows: Red-shafted Flicker,
Starling, Clark’s Nutcracker, Hairy Woodpecker, and Downy Woodpecker.
The more abundant associates tend to bave higher ranks.

Although the Pinon Jay is largely passive in its behavioral relations with
the five associate species, it does possess many of the traits discussed by
Moynihan (1960, 1962 ) which promote both intra- and interspecific gregari-
ousness. The general noisiness and restlessness of the jay flock tend to focus
attention on it. The neutral, rather drab blue coloration of the Pinon Jay
may act as an attractant to species that are normally repulsed by a shar})ly
contrasting plumage. The dorsal blue or blue-gray coloration is similar to
that found in species that form mixed flocks in the Andes and Bolivia
(Moynihan, 1968). The associate sj>ecies show some of these same traits
and others, including striking flash patterns on either wings, rump, or tail.

In our opinion the most important characteristics promoting this association
are similarities of foraging strategies and similarities in size. Lsing the

72

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Table 5

Indices of Specialization (J') of Foraging by Pinon Jays and
Sum Frequency of Association

Jan., Feb.,
March

April, May,
June

July, Aug.,
Sept.

Oct., Nov.,
Dec.

J'

0.992

0.757

0.716

0.983

Sum*

Frequency

3.31

1.81

1.07

3.06

* From Table 2;

Average number of

species to be seen

with the flock

during this period.

suggestions of Pielou (1966) we calculated the foraging diversities (H'j and
indices of specialization (J') (after Willson, 1970) of the Pinon Jay flock for
four different periods of the year (Table 5). The higher the Y the less
specialized and consequently more diverse the foraging pattern. J' was then
compared to the sum frequency (see Table 2; expected number of associate
species to be found with the Pinon Jay flock) and a very high positive corre-
lation results. That is, when Pinon Jays are most diverse in their foraging
sites, the number of associates is highest.

Numerous workers have pointed out the similarities in body size and
weight of members of interspecific flocks. Tables 3 and 4 list weights for
the species that occur in the home range of the Pinon Jay at least a portion
of the year. The average weights of the associates range from a low of 28 g
for the Downy Woodpecker to a high of 142 g for the Clark’s Nutcracker.
If we eliminate the Downy Woodpecker from this comparison because of its
low numbers and obviously low social status, as indicated by the outcomes
of interspecific hostile interactions, the weight range for the other four species
is 64-142 g. The average weight of 27 adult Pinon Jays is 108 g, almost
exactly intermediate to the weight of the associates. This range includes five
potential associates. Mourning Dove, Acorn Woodpecker, Steller’s Jay, Robin,
and Brewer’s Blackbird that do not associate. The Steller’s Jay is found in
high numbers year round, but appears to maintain definite winter home
ranges. The other four species are either present in very low numbers through-
out the year or are present only during the nesting season when they show
strong affinities for nests or territories. Rather than join the flock, these
birds all show signs of alarm when the jay flock comes into proximity with
them. The typical response was to scold loudly and leave the area. During
the warm winter of 1970-71 flocks of Robins occasionally mingled with the
jays at watering or feeding sites but did not follow them. Thus, size must be
only a secondary factor in determining flocking associates.

Bahia, Bateman
and Foster

pinon jay flocking associates

73

Flocking of the five species with Pihon Jays is probably due to their join-
ing the jay flock when food is scattered widely throughout the habitat. The
associates are then assured a share of the food. When food is super-abundant,
as at the feeding station, attraction to the jay flock is not as evident. This
assurance is best demonstrated in those cases of a species associating with
the jays when they performed a specific type of foraging. The woodpeckers
are most closely associated with the flock during the winter when many
jays forage off the ground by flaking bark, probing crevices and opening
ponderosa pine cones. The flicker associates most of the year, and there is
always a portion of the jay flock feeding on the ground. The nutcracker
shows a bond with the jay flock during the time both species are caching
pihon pine seeds. Austin and Smith (in press) have shown that some flocking
species increase their foraging diversity in winter. This is true in the Pihon
Jay. Morse (1970) demonstrated that the associates modify their area of
foraging in the presence of socially dominant species whereas Austin and
Smith (in press) believe the numerically dominant species may alter their
foraging pattern to accommodate the associates. We believe the Pihon Jay
increases its foraging diversity during the more demanding winter months
in order to obtain an ample supply of food. This, in turn, attracts the associ-
ate species. The Pihon Jay is probably more diverse in its foraging patterns
than the associate species. This relationship between nuclear and associate
species was also shown by Morse (1970) and Austin and Smith (in press).

The tendency of the associates to form mixed flocks is probably a species-
specific trait, or set of traits expressed when advantageous, but not necessary
for survival except under special conditions imposed by the local ecological
situation. Harvesting of vast quantities of food by Pihon Jays may make it
advantageous for other species to join them. At the feeding station, only
Starlings actively joined the flock. Here food was constantly renewed and
the woodpeckers and flickers did not move with the flock when it left the
station but stayed to harvest the replenished food items.

Comparing the behavior of the associates at the feeding station to that of
the flock in a more natural habitat, suggests that participation in the flock by
the associates is directly related to the density and obviousness of the food
items. When food is abundant, obvious, and easily obtained the tendency to
form mixed flocks decreases. This has also been suggested for insectivorous
flocks by Gibbs (1960) and Hinde (1952) .

The advantages to be obtained from the association herein described are
in all probability food and protection gained by mechanisms similar to those
described and reviewed by Morse (1970), for insectivorous flocks. J he above
author rarely, if ever, observed ra])tors near or attempting to enter mixed
flocks. In contrast, we observed raptors being scolded or mobbed on 12 per

I

74

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

cent of the observation periods, and observed potential predators on 84 per
cent of our visits to the home range of the Pihon Jay flock.

When sentries gave the rhythmic danger call, associates responded by flying
up into concealing foliage and remaining still. This action was spontaneous
and took less than five seconds to complete. The associates never lagged
behind the jays in this movement and appeared to recognize the danger call
as quickly as did the Pihon Jays. Although Pihon Jays were quick to mob
potential predators, only the Red-shafted Flicker and Clark’s Nutcracker par-
ticipated in this behavior. Their participation in scolding and mobbing poten-
tial predators was meager as they joined the jays on less than 20 per cent of
the scolding and mobbing performances. Thus, the associates gained appreci-
able protection from the actions of the Pihon Jays.

Associate species and also species that did not associate with the Pihon Jay
flock were often, if not always, stimulated by social induction or facilitation
(Rand, 1954) to feed when the jays were present. On numerous occasions
Steller’s Jays and j uncos were observed to feed intently with the jays as they
passed but these non-associates did not follow the flock when it departed, or
only followed a short distance. Westcott (1969) made similar observations
on Steller’s Jays following a Pihon Jay flock in southern Arizona. Feeding
activities of these non-associates ceased when the flock departed. This behavior
suggests that all birds may derive some protection from the well organized
sentinel system of the Pihon Jay flock. Not only are other species induced to
feed in the presence of the jay flock, but they can do so intently because the
predator warning system established by the jays allows these species to con-
centrate solely on feeding. One would suppose that this concentration would
increase feeding efficiency. Thus, it is difficult to separate the benefits of
associating with the jay flock into protection and feeding efficiency, as both
appear to be important but not clearly distinguishable from each other (see
Lack, 1968).

SUMMARY

The Hairy and Downy Woodpeckers, Red-shafted Flicker, Clark’s Nutcracker, and
Starling were observed to form interspecific flocks with the highly gregarious Pihon
Jay. The general noisiness and restlessness of the jay flock, plus the drab coloration
of its members probably acted to attract the associate species. The Pihon Jay flock was
intact throughout the year, although in a number of different forms, thus offering attend-
ant species an opportunity to participate in mixed flocking year round. The frequency
of occurrence and numbers of associates varied with season and foraging site diversity
of the Pihon Jay flock. A strong positive correlation exists between foraging site diversity
of the jays and frequency of the associates.

The ability of the associates to remain in the Pihon Jay flock is enhanced by the lack
of intraspecific aggression among the jays.

Baida, Bateman
and Foster

pinon jay flocking associates

75

The important characteristics promoting this association are similarities of foraging
strategies and secondarily similarities in size.

The benefits derived by associate species as a result of interspecific flocking are prob-
ably more effective utilization of the total food resources, indirectly resulting from effi-
cient protection from predators while feeding and directly as a result of the greater
ability of numerous individuals to locate scattered, but locally abundant, sources of food.

ACKNOWLEDGMENTS

S. Vander Wall is thanked for his valuable field assistance and J. Hubbard for supplying
some of the bird weights. Earlier drafts of this paper were read and criticized by F. A.
Pitelka, J. L. Brown, J. D. Ligon, and T. A. Vaughan. We thank these reviewers for
their valuable suggestions and comments.

LITERATURE CITED

Allee, W. C. 1938. The social life of animals. Norton & Co., New York.

Austin, G. T., and E. L. Smith. 1972. Winter foraging ecology of mixed insectivorous
bird flocks in oak woodland in southern Arizona. Condor, 74:17-24.

Balda, R. P., and G. C. Bateman. 1971. Flocking and annual cycle of the Pinon Jay
(Gymnorhinus cyanocephalus) . Condor, 73:287-302.

Baldwin, S. P., and S. C. Kendeigh. 1938. Variations in the weight of birds. Auk,
55:415-467.

Beidleman, R. B., and J. H. Enderson. 1964. Starling-Pinon Jay associations in
southern Colorado. Condor, 66:437.

Brown, J. L. 1964. The integration of agonistic behavior in the Steller’s Jay Cyanocitta
stelleri (Gmelin). Univ. California Publ. Zook, 60:223-328.

Cary, M. 1901. Birds of the Black Hills. Auk, 18:231-238.

Darling, F. F. 1938. Bird flocks and the breeding cycle. Cambridge Univ. Press.

Gibbs, J. A. 1960. Populations of tits and Goldcrests and their food supply in pine
plantations. Ibis, 102:163-208.

Hartman, F. A., and K. A. Brownell. 1961. Adrenal and thyroid weights in birds.
Auk, 78:397^22.

Hinde, R. a. 1952. The behavior of the Great Tit {Pams major) and some other re-
lated species. Behaviour Suppl., 2:1-201.

Jensen, J. K. 1926. The Pinon Jay {Cyanocephalus cyanocephalus). The Oologists’
Record, 6:41-43.

Johnson, H. C. 1902. The Pinyon Jay. Condor, 4:14.

Lack, I). 1968. Ecological adaptations for breeding in birds. Methuen & (^o. Ltd.,

London.

Miller, A. H. 1955. The avifauna of the Sierra del Carmen of Coaluiila, Mexico.
Condor, 57:154^178.

IVIiLLER, R. C. 1921. The flock behavior of the Coast Bush-tit. (Condor, 23:121-127.
Morse, 1). H. 1970. Ecological aspects of some mixed-species foraging flocks of birds.
Ecol. Monogr., 40:119-168.

Moyniiian, M. 1960. Some adaptations which help to i)romote gregariousness. Proc.
XII Internatl. Ornithol. Congr. : 523-541.

Moyniiian, M. 1962. The organization and jirobable evolution of some mixed species
flocks of neotropical birds. Smithsonian Mise. 0)11., 143:1-140.

76

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Moynihan, M. 1968. Social mimicry; character convergence versus character displace-
ment. Evolution, 22:315-331.

Odum, E. P, 1942. Annual cycle of the Black-capped Chickadee. Auk, 59:499-531.

PiELOU, E. C. 1966. The measurement of diversity in different types of biological col-
lections. J. Theoret. Biol. 13:131-144.

Poole, E. L. 1938. Weights and wing areas in North American birds. Auk, 55:511-517.

Rand, A. L. 1954. Social feeding behavior of birds. Fieldiana Zook, 36:1-71,

Salt, G. W. 1957. An analysis of avifaunas in the Teton Mountains and Jackson Hole,
Wyoming. Condor, 59:373-393.

Short, L. L., Jr. 1961. Interspecific flocking of birds of montane forest in Oaxaca,
Mexico. Wilson Bull., 73:341-347.

Stallcup, P. L. 1969. Hairy Woodpeckers feeding on pine seeds. Auk, 86:134-135.

Tinbergen, N. 1953. Social behavior in animals. Methuen & Co., London.

Westcott, P. W. 1969, Relationships among three species of jays wintering in south-
eastern Arizona. Condor, 71:353-359,

Wetmore, a. 1920, Observations on the habits of birds at Lake Burford, New Mexico.
Auk, 37:221-247; 393-412.

Willis, E. 0. 1966. The role of migrant birds at swarms of army ants. Living Bird,

5:187-231.

Willson, M. F. 1970. Foraging behavior of some winter birds of deciduous woods.
Condor, 72:169-174.

Wing, L. 1941. Size of bird flocks in winter. Auk, 58:188-194.

DEPARTMENT OF BIOLOGICAL SCIENCES, NORTHERN ARIZONA UNIVERSITY, FLAG-
STAFF, ARIZONA 86001. ADDRESS OF THIRD AUTHOR: 420 W. OAK AVE.,

FLAGSTAFF, ARIZONA 86001, 17 MAY 1971.

ON THE EVOLUTION OF SOCIALITY, WITH
PARTICULAR REFERENCE TO TIARIS OLIVACEA

Ronald Pulliam, Barrie Gilbert, Peter Klopfer, Dennis McDonald,
Linda McDonald, and George Millikan

The behavior of the Yellow-faced Grassquit [Tiaris olivacea) apparently
ranges from social and nonaggressive on the Central American mainland
to territorial and very aggressive on the island of Jamaica (Pulliam, 1970).
Why these differences?

This paper reports observations on the population size, habitat distribution,
and social behavior of the Yellow-faced Grassquit on the island of Cayman
Brae, West Indies, and speculations on factors influencing social behavior.
Cayman Brae is a very small island (20 square miles) and this population of
grassquits is extremely isolated from other populations, the nearest being
found on Grand Cayman (80 miles southwest) and on Jamaica (190 miles
southeast) . The third of the Cayman Islands, Little Cayman Island, is about
ten miles west of Cayman Brae, but grassquits are very rare or absent there
perhaps because of a lack of suitable habitat.

The observations reported here are based primarily on a two-week field
study beginning 27 November, 1969. Additional observations must be made
at other times of year for confirmation of our findings. However, the social
organization of the species has been noted by one author (Pulliam) to be
stable throughout the year in Jamaica and Skutch (1954) indicates that Costa
Rican grassquits can be found in flocks during all seasons of the year.

THE EVOLUTION OF SELFISH BEHAVIOR

Hamilton (1964) has demonstrated that kinship selection can limit the
expression of behavior which decreases the fitness of a neighbor more than it
increases the fitness of the actor (i.e., selfish behavior). Kinship selection
encompasses the notion that an individual’s overall fitness includes not only
the effects of his genotype on his own ability to leave descendants hut also the
effects of his genotype on the fitness of relatives who carry some proportion
of genes identical by descent to his own. Although Hamilton’s model is
formally correct, it is applicable only if the selfish behavior of a population is
determined by the gene frequencies at one locus. We contend that aggression
or selfish behavior is not coded at a single chromosomal locus (see Klopfer.
1969) but that the degree of aggression in an individual must he thouglit of
as resulting from the interaction of the animal’s environment with the epislatic
effect of a large number of genes at very many loci. Thus, in an almost

77

78

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

homozygous population, selfish behavior might be selected against because it
decreases one’s own inclusive fitness.

In this paper we argue that some forms of aggressive and territorial behav-
ior constitute “selfish behavior” and, thus, their occurrence in natural popula-
tions must be restricted to relatively heterozygous populations.

An aggressive territory holder can decrease the fitness of a nonaggressive
bird by excluding it from optimal habitat. It is less obvious that the decrease
in fitness of the nonaggressive bird is greater than the increase in fitness of
the aggressor. However, the territorial bird does lose some of the advantages
of social behavior (whatever they are) and must spend considerable time
defending bis territory, time which might otherwise be applied towards main-
tenance and reproduction. The amount of time which the average aggressive
individual spends defending his territory must necessarily increase as the
proportion of the bird population which is territorial increases. Hence, the
question: why are some grassquits territorial?

Suppose territorial individuals do have a lower reproductive capacity than
social individuals would have in the absence of the former. This would result
in a territorial population maintaining lower numbers than a social population
even though the territorial individuals were superior in competition with the
social individuals! If, for a given bird species, the social populations were
shown to maintain a significantly higher population density than the territorial
populations, we would have evidence that territoriality is a selfish behavior
for that species.

Pulliam (1970) censused, during the breeding season, 11 similar habitats
that appeared suitable for Yellow-faced Grassquits in both Jamaica and Costa
Rica. Each habitat was visited twice. In Costa Rica, on a total of 25.9 acres,
an average of 20.5 grassquits were seen. In Jamaica, on a total of 18.0 acres,
an average of only 6.9 grassquits were seen. In both Costa Rica and Jamaica
there were grassquits in four of the eleven habitats visited. The number of
grassquits per acre in those sites containing some grassquits was 2.9 in Costa
Rica, as compared to 0.7 in Jamaica. The increase in the density of the Costa
Rican grassquits is especially surprising since there were many more individ-
uals and species sharing sites with grassquits in Costa Rica than there were in
Jamaica. Thus, it appears that the social grassquits of Costa Rica are able to
maintain a population density two to three times as great as that of the terri-
torial Jamaican grassquits. This accords with our supposition.

Very little is known about the degree of heterozygosity in natural popula-
tions of birds and we are not yet able to predict the degree of heterozygosity
that might permit selfish traits to evolve. However, we do know that both
isolation and population size exert considerable influence on the degree of
genetic diversity of natural populations. In very small populations, random

I’ulliam
et al.

SOCIALITY IN GRASSQUIT

79

drift can lead to fixation or loss of genetic variability. This decay of genetic
variation is counter-balanced by the forces of mutation and immigration.
Soule (1971) presents arguments and evidence that for lizards large popula-
tion size and migration between adjacent populations is necessary for the
maintenance of genetic diversity. Soule showed that lizards from small, iso-
lated island populations showed less variation in electrophoretically detectable
isozymes than lizards from large island populations. The decrease in enzyme
variation was correlated with a deerease in morphological variance. This
result indicates that isolation and small population size result in a decrease
in genetic diversity and could, therefore, limit the expression of selfish be-
havior traits.

Tiaris olivacea is an abundant inhabitant of the subtropical plateau region
of Costa Rica (Slud, 1969). However, the grassquit is a bird of secondary
growth habitats, never found in the dense forest, and is therefore restricted
in distribution to areas near human habitation and agriculture. The human
population of Costa Rica is largely limited to areas in close proximity to roads
or rail lines. Thus, habitat suitable for grassquits is discontinuously distri-
buted along the few roads and railroads in eastern Costa Rica. In May of
1969 Pulliam searched for grassquits along the road from San Jose to Tur-
rialba and along the railroad between San Jose and La Lola Farms, which
is about 30 miles west of Port Limon on the Gulf of Mexico. This journey
made an east-west transect across almost the entire range of Tiaris in Costa
Rica. Grassquits were first noted along the roadsides about 5 miles east of
Cartego. From Cartego to Turrialba, grassquits were frequently recorded in
suitable habitats but these habitats were distributed in patches. Along the
railroad, grassquits were noted from Turrialba to La Lola Farms, where they
were common. Suitable habitat along the railroad was distributed in discrete
patches and often interrupted by many miles of forest habitat. In addition to
the patchwork character of suitable habitat, the presence of a dozen or more
sympatric seed-eating finches may further limit the distribution of grassquits.
This combination of a patchwork habitat and many competitor species would
tend to result in Tiaris being found in isolated groups of small size in Costa
Rica. We expect their social behavior to be related to a high degree of genetic
I homozygosity maintained because of the patchiness of their distribution.

Tiaris olivacea is found in all parts of Jamaica with the possible exception
I of the very dry Southeast. Throughout the range of grassquits in Jamaica
there are numerous roads and, therefore, much more habitat suitable for
Tiaris than in Costa Rica. This suitable habitat is virtually continuous over
the entire island except in the high mountains which are s})arsely settled by
I humans. Also, in Jamaica there is only one other sj)ecies of finch which feeds
exclusively on grass seeds. The two factors combine to })roduce a continuous

80

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

and therefore very large grassquit population. We expect such a population
to be genetically more diverse than the discretely distributed Costa Rican
population and, thus, to permit the occurrence of selfish behavior. In fact,
the Jamaican birds, in contrast to those of Costa Rica, are territorial, as noted
above.

These arguments are conjectural and were largely developed ex post facto,
after our studies in Jamaica and Costa Rica. If, however, the argument
is correct we would expect to find that any isolated, small populations of
grassquits would exhibit social rather than selfish behavior, and be more
similar in their social structure to the Costa Rican population than to the
Jamaican population. With this idea in mind, we attempted to ascertain the
population size and social structure of the isolated grassquit population on
Cayman Brae Island.

ESTIMATE OF GRASSQUIT POPULATION SIZE ON CAYMAN BRAG

Data for population size estimates were collected by locating and then, only
once, walking slowly through suitable habitats and recording all birds heard
or seen. “Suitable habitat” was defined as those areas where trees and shrubs
covered less than 80 per cent of the ground and where there was some grass
growing. This definition of suitable habitat was consistent with our observa-
tions in Costa Rica and Jamaica that grassquits were found only in grassland
and old-field habitats and the observations of Skutch (1954) in Costa Rica
and Wetmore (1927) in Puerto Rico that the diet of grassquits consisted
almost entirely of grass seeds. However, on Cayman Brae we often found male
grassquits singing from the upper branches of trees and shrubs near the edges
of fields. Figure 1 illustrates that the grassquits in trees were always very
close to a grassy field. The data for Figure 1 were collected by pacing along
a path which ran all the way across the island from North to South. The loca-
tion of the bird is plotted as the location at which the bird was estimated to be
at right angles to the path. Thus, those birds which appear, in the figure,
to be in the fields may actually have been singing from trees and shrubs on
the east or west sides of the fields. At any rate, the data presented in Figure
1 are consistent with our belief that the grassquits are found only in or near
field habitats. Since the maintenance of such habitats on Cayman Brae de-
pends entirely on their being accessible to people (due to the rapidity of suc-
cessional growth), we felt confident that most such habitats could be found by
traversing all roads and paths on the island.

One of the assumptions of the model (presented in the Appendix) used to
estimate population size is that the probability of a call in any interval of time
is constant throughout the time of observation. It is well known, however,
that many birds show a pronounced decrease in singing in the middle of the

Pulliam
et al.

SOCIALITY IN GRASSQUIT

81

cCCG ^£!brCCp

^hcCbcO

ciArrO-

575

150

t ^ 1725

Crr^r^Q--Q~(}-i(\

CxX)cC>rCf^£lit^

^ 2300

G

2875

<iss^?cm) cctpteoQ ,, n

^ ^ T t 3450

G G G G

Oi

4025

^ 4200
G

Fig. 1. Observations on the location of birds along a transect across Cayman Brae
Island. The symbol G indicates the position of grassquits along the transect and the
numbers on tbe right indicate the distance from the start of the transect, (irassy fields
are indicated by the clear areas and forests and garden are indicated diagrammaticalK .

(lay. Thus, the probability of recording a bird in the middle of the da\ might
be lower than, say, in the early morning. Table 1 shows the number of songs
per thirty-minute interval for seven individual grassquits sampled at difftMcnt
times of the day. It appears from this sample of singing arti\it\ that th(*re

82

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Table 1

The Number of Bird Songs in Thirty-minute Intervals for Seven Individual
Grassquits Watched at Different Times of Day.

The times on the left indicate the beginning of each thirty minute interval.

1 2 3 4 5 6 7 Average

7:00

60

20

40

7:30

38

18

28

8:00

48

20

34

8:30

118

3

61

60

9:00

23

17

80

40

9:30

0

82

41

10:00

85

36

60

10:30

17

17

11:00

1

1

11:30

46

46

12:00

3

3

12:30

40

40

13:00

57

57

13:30 40 40

14:00 76 76

14:30

28

28

15:00

18

18

15:30

21

21

16:00

4

43

23

16:30

9

56

32

17:00

51

51

may be a slight decrease in singing rate in the middle of the day. Since the
sample size is so small, particularly for the mid-day period, this is not certain.
Even if there is a decrease in singing rate at mid-day we believe it does not
seriously effect our results, since the decrease appears to be small and less
than 10 per cent of our censuses were taken in the mid-day period ( between
10:00 and 14:00).

Lor three of the seven birds for which data are given in Table 1, we were
able to record the occurrence of each song to the nearest second. Erom these
data we could assess the reliability of our census technique (see the Appendix) .
Figure 2 indicates that the probability of recording a bird does not differ
significantly from one time of day to the next.

For the total census we recorded 190 male and 24 female grassquits. Of the
190 males, 161 were heard singing and 29 were only seen. If we assume the
sex ratio to be equal and that there must have been some suitable habitat which
we did not locate, then we must conclude that there were at least 400 grassquits
on the island. However, this is undoubtedly an underestimate since many

Pulliam
et al.

SOCIALITY IN GRASSQUIT

83

TIME (MINUTES)

Fig. 2. The probability of recording a bird as singing as a function of the length of
time that an observer is within hearing range of the bird. See Appendix for estimation
procedures.

birds must not have been recorded even though we located the fields in which
they resided. From the estimates of the probability of recording a bird in
Figure 2 we can get some idea as to how accurate our census was. A singing
male grassquit can be heard from 75 to 100 feet away. If we assume that our
walking speed through the fields was between one and two feet per second, it
follows that an observer was within hearing range of each bird for from one
to three minutes if the field where the bird resided was actually located.

; Taking a very liberal estimate of the population size we assume that each

I bird was in hearing range for only one minute and thus, from the lowest esti-
mated probability of recording a bird when it is within hear-range for one
minute (From Bird No. 3, Fig. 2), we estimate that only 55 per cent of the
male birds were recorded by being heard. Thus, a liberal estimate of popula-
tion size is about 300 male birds (or approximately 600 birds, total). Ibis
estimate may still be too low since there may have been first-year male birds
which were not singing. Assuming there may he as many as one non-singing
male for each singing male we can boost the total estimated population size
to about 1,200. Finally, there were the birds in the fields that we did not
locate and assuming that we may have not found as much as 20-25 per cent of

84

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

the suitable habitat, we reach a figure of 1,500 birds. It should be realized
that in arriving at this estimate of population size we took the extremes of
all estimation parameters so as to give an absolute upper limit. At the other
end of the scale we could assume that we observed all of the male grassquits
on the island. Taking the two extremes we can state fairly confidently that
there were between 400 and 1,500 Yellow-faced Grassquits on the island at
the time of our census.

SOCIAL BEHAVIOR OF THE YELLOW-FACED GRASSQUIT

In Jamaica, the Yellow-faced Grassquit is strictly territorial. Nine terri-
tories in optimal habitat measured in June-July, 1968, near Treasure Beach,
Jamaica, averaged only 0.25 acres each and aggressive encounters between
males on adjacent territories were frequent. Although Jamaican grassquits
never occur in flocks, individuals of both sexes are known to aggregate
occasionally at artificial feeding stations and when this happens males seem
to spend more time fighting than feeding.

Skutch (1954) describes the Yellow-faced Grassquit in Costa Rica as
lacking “that pugnacious jealousy so prominent and characteristic in many
members of the finch family” and as “a most pacific bird. I have never noted
any fighting or discord among them.” However, males do defend a small area
in the immediate vicinity of the nest from which other males of the same
species are expelled. Skutch describes this defense as follows: “all the terri-
torial male does is fly mildly in the direction of the intruder who retreats
without necessity of conflict.” Grassquits which are not nesting are normally
found in large feeding flocks which often contain thirty to forty individuals,
with both sexes represented. Pulliam (1970) noticed no signs of aggression
within flocks but did note occasional conflicts between grassquits and other
seed-eating finch species during a three-week field study during the breeding
season in 1969 near Turrialba, Gosta Rica.

The contrast between the highly social behavior of Costa Rican grassquits
and the strictly territorial behavior of the Jamaican grassquits is typical of
the differences in social behavior of a number of passerine bird species from
Costa Rica and Jamaica. Pulliam (1970) compared tbe social behavior of all
resident bird species of the families Fringillidae, Thraupidae, and Icteridae for
which data could be found for Jamaica and Costa Rica. He found that 18 of
the 26 Costa Rican species showed some form of social tolerance (family
groups or flocking) compared to only two of the 11 Jamaican species. [The
definition of “no social tolerance” is that at all times of the year individuals
are either alone or in the company of a single adult of the opposite sex and/or
juvenile birds up until a short time after fledging.] This is consistent with
the supposition that continuously distributed species are more likely to be

NUMBER OF BIRDS IN EACH CLASSIFICATION

Pulliam
et al.

Fig. 3

SOCIALITY IN GRASSQUIT 85

GROUP SIZE

. The sizes of groups of grassquits observed for three different populations.

86

THE WILSON BULLETIN

Marcli 1972
Vol. 84, No. 1

genetically polymorphic, and thus aggressive, since Jamaican birds seem to
he more continuous in their distributions than Costa Rican birds.

The social behavior observed for grassquits on Cayman Brae can best be
described as intermediate between the social behavior of Jamaican and Costa
Rican grassquits. Adult males were typically seen singing from trees and
shrubs on the edges of grassy fields. The frequency of singing appeared to in-
crease in the presence of other adult male birds and dueting between birds
on adjacent territories was frequently observed. However, chases between
adult male grassquits were observed only on two occasions, whereas they
were very frequent in Jamaican grassquits (Pulliam, 1970). On several occa-
sions adult male birds were seen to sit on the same limb within a few inches or
feet of each other and sing without any subsequent displacement. On at least
two such occasions the birds flew together to the ground where they fed in
close proximity to one another.

Figure 3 shows the group sizes observed for Cayman Brae grassquits as
compared to group sizes observed by Pulliam (1970) in Jamaica and on the
Central American mainland. In each case all observations during a two-week
study period are recorded. However, the Cayman Brae data were collected
in November-December, 1969 while the Jamaican and Costa Rican data were
collected in April-May, 1968. The possibility that the observed differences
are due to seasonal change will be discussed later. A total of ten groups in
the category of three to ten birds (Fig. 2) were observed on Cayman Brae.
These groups ranged in size from three to six and, therefore, some could be
family groups. In some of these groups, one or more of the birds was identi-
fied as an immature. The category 2S indicates that two males were seen
together and that there was a subsequent chase and displacement. While this
was the most frequent category in Jamaica (perhaps because of conspicuous-
ness ) , no such interactions were observed in Costa Rica and only two were
observed on Cayman Brae.

HABITAT UTILIZATION

Slud (1961) describes the habitat of the Yellow-faced Grassquit in Costa
Rica as follows: “it inhabits fields, plantations, pastures, clearings, roadsides,
an deforested areas in general.” According to Wetmore (1927) and Wetmore
and Swales (1931), the grassquit in Puerto Rico is found entirely in open
pastures, cultivated fields, hedges, or scanty growth of bushes. In Jamaica,
grassquits are commonly found in pastures, gardens, roadsides, and planta-
tions ( Pulliam, 1970 ). The common denominators of grassquit habitats seem
to be incomplete canopy cover and the presence of grasses.

The grassquits on Cayman Brae were found mainly along roadsides and in
or near grassy fields. There were no grassquits recorded in the coconut palm

Pulliam
et al.

SOCIALITY IN GRASSQUIT

87

plantations on the north side of the island where there were very few grasses.
However, there were grassquits in the smaller coconut palm plantations on the
south side of the island where there were abundant grasses.

A large number of grassquits were found in trees and shrubs in or near
grassy fields (see Fig. 1). Grassquits observed in trees were almost without
exception males and only in a few instances appeared to be feeding. When the
grassquits did feed in the trees they seemed to be gleaning much in the manner
of a wood warbler. Skutch (1954) and Slud (1964) report the same behavior
occurs in Costa Rican grassquits when food is scarce even though the normal
diet consists only of the seeds of grasses.

DISCUSSION

We have argued that the maintenance of the social behavior of Costa Rican
grassquits is dependent on the patchiness of their distribution which limits
both effective population size and gene flow between populations and thus
reduces the genetic diversity within subpopulations. If this interpretation is
correct, we would expect that populations of grassquits on small isolated
islands would, like the mainland grassquits, exhibit decreased heterozygosity,
which would, in turn, limit the expression of selfish traits. Our census of the
grassquits of Cayman Brae, indicates that there are between 400 and 1,500
grassquits on the island. A population of this size should be sufficiently large
to prevent the loss of genetic diversity through random drift as might occur
in smaller populations (see Crow and Kimura, 1970) .

Our observations on the sociality of the Cayman Brae grassquits indicates
that they are intermediate between the highly territorial Jamaican grassquits
and the very social Costa Rican grassquits. However, the observations on the
Cayman Brae birds were restricted to a short period in the autumn of 1969
as compared to extensive observations of the Jamaican and Costa Rican birds
during all months of the year. Thus, the behavior of the Cayman Brae birds
may only reflect a seasonal lull in territoriality at the end of the breeding
season. However, the tolerance occasionally observed between adult male
birds has not been reported from Jamaica. In Jamaica the birds breed in all
months of the year, so some post-breeding males should always be in evidence.

It is clear that three further steps need to be taken to substantiate our pre-
pared explanation: (1.) The Cayman Brae population should be studied at

other times of the year to assure there are no seasonal variations in the social
organization of the population; (2.) A general survey of the frequency of
various forms of social organization in birds as a function of island size and
isolation should be conducted; and (3.) Data specifically relating the degree
of genetic variability in birds to the size and isolation of islands should l)e
gathered.

88

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

SUMMARY

The Yellow-faced Grassquit (Tiaris olivacea) is discontinuously distributed and highly
social in Costa Rica. In Jamaica its distribution is continuous and it is aggressively
territorial. On Cayman Brae we estimate that grassquit population consists of 400-1,500
individuals which seem intermediate between Costa Rican and Jamaican grassquits in
their social organization. We speculate that aggressive behavior of the sort we have char-
acterized as “selfish” cannot arise except under conditions of considerable genetic vari-
ability.

ACKNOWLEDGMENTS

This work was supported by grants-in-aid from Sigma Xi, the Chapman Fund of the
American Museum of Natural History, and NIMH 04453. We thank Kathy Gilbert, Marye
Haskins and Erika, Gretchen, Lisa, and Martha Klopfer for their assistance in the field.

APPENDIX

We estimate the probability of recording the given bird as a function of the length
of time ( m ) that an observer is within hearing distance of the bird. First, consider the
probability of recording a bird given that the observer arrived within hearing distance
during an interval for which the bird was silent for exactly L seconds, where L > m. If
the obsen'er arrives in the first L-m seconds of the interval then the bird will not be
recorded. However, if the observer arrives in the last m seconds of the interval, he will
record the bird. Thus the probability of not recording the bird, given that the observer
arrived during an interval for which the bird was silent for L seconds (L^m) is
(L-m)/L. Of course, if the observer arrives within hearing distance of the bird during
an interval for which the bird is silent for a period of time less than m seconds, then the
observer will always record the bird.

The estimated probability that a bird will be silent for exactly L seconds is given by
(riL‘L)/T, where jil is the number of times that the bird is observed to be silent for
exactly L and T is the total length of time for which the birds’ songs are recorded. Thus,
the probability that a bird will not be recorded is the product of the probability that the
observer arrives during a period for which the bird is silent for exactly L seconds (which
is (ul'L/T) and the probability that the bird will not be recorded given that the observer
arrived during such a period (which is {L-m) /L) summed over all observed values of
L greater than m, which reduces to

L^m

{L-m) .

1)

These values were calculated for the three birds for which data were available. The
values plotted in Figure 1 are for the probability of recording a bird as a function of the
length of time that an observer is within hearing distance of the bird. The values for the
probability of recording the bird are, of course, simply one minus the probability of not
recording the bird which is calculated with Formula 1. Notice that the values are very
similar for the three birds indicating rather little variance in the probability of recording
a bird. This probability does not approach one until after about nine or ten minutes but
after one minute is already about 0.65. Bird No. 4, which was watched in mid-day, does
not indicate a lower probability of being recorded despite the lower average number of

Pulliam
et al.

SOCIALITY IN GRASSQUIT

89

calls per half-hour period in the mid-day (as shown in Table 1.). Though there were
fewer calls, they were more evenly spaced in time than was the case for the other two
birds.

LITERATURE CITED

Crow, J. F., and M. Kimura. 1970. An introduction to population genetics. Harper
and Row, New York.

Hamilton, W. 0. 1964. The genetical evolution of social behavior. J. Theoret. Biol.,

7:1-16.

Klopfer, P. H. 1969. Instincts and chromosomes: what is an innate act? Amer.

Naturalist, 103:556-560.

Pulliam, H. R. 1970. Comparative feeding ecology of a tropical grassland finch
[Tiaris olivacea) . Ph.D. dissertation, Duke University, Durham, N. C. Ecology, in
press.

Skutch, a. F. 1954. Life Histories of Central American Birds. Pacific Coast Avifauna,
31.

Slud, P. 1964. The Birds of Costa Rica: Ecology and Distribution. Bull. Amer. Mus.
Nat. Hist., 128.

Soule, M. 1971. The gene flow-variation hypothesis. Taxon, in press.

Wetmore, a. 1927. The birds of Puerto Rico and Virgin Islands. Scientific Survey
of Porto Rico and the Virgin Islands, 9:245-406.

Wetmore, A., and B. H. Swales. 1931. The birds of Haiti and the Dominican Republic.
U.S. Natl. Mus. Bull., 155:1-483.

ZOOLOGY DEPARTMENT, DUKE UNIVERSITY, DURHAM, NORTH CAROLINA 27706,

(present address of senior author, department of biological sci-
ences, UNIVERSITY OF ARIZONA, TUCSON, ARIZONA 85721), 7 MAY 1971.

GENERAL NOTES

Further notes on the Pinnated Bittern in Mexico and Central America.—

Since the description of the Mexican form of the Pinnated Bittern, Botaurus pinnotus
curibaeus (Dickerman, Wilson Bull., 73:333-335, 1%1), 17 additional specimens have
been collected in Mexico and Central America that substantiate the color characters
used to describe caribaeus and add to our knowledge of the species’ range. One of these
from Costa Rica was previously reported by Slud (Bull. Amer. Mus. Nat. Hist., 128:43-44,
1964). Slud (p. 44) questioned the validity of the Mexican form caribaeus, but apparently
misunderstood the characters of the latter race. Wing and tail length, stressed by Slud,
were not utilized as characters, and the bill of the Costa Rican bird matches South
American pinnatus, as it should. Slud’s statement that his bird “approaches the descrip-
tion of caribaeus in general appearance” may be discounted, as he saw no specimens
of that form. Actually, in coloration, the specimen is typical of the nominate race. Some
of the 11 recent Mexican specimens are worn and faded; however, fresh-plumaged
Mexican birds are definitely paler, less ochraceous than fresh-plumaged Central or South
American specimens (see list of specimens examined below). This is most dramatic
in the color of the auriculars, which are sandy buff in caribaeus in contrast to ochraceous
buff in pinnatus. In series, ventrally, caribaeus is whiter, less buffy. The auriculars of
the juvenile caribaeus from Tabasco (Dickerman, ibid.:334) are richer than are those
of adults, and thus approximate the color of the auriculars in the nominate form. A
second juvenile caribaeus beginning the first prebasic molt was taken 14 August near
Lerdo de Tejada, Veracruz.

Tlie exposed culmen of caribaeus averages sliglitly longer than the exposed culmen of
pinnatus. The measurements are: seven female caribaeus 84-91 mean (87.4) ; nine
female pinnatus 78-87 (82.9) ; ten male caribaeus 87-96 ( 91.9) ; thirteen male pinnatus
82-104 (89.5).

Additional Specimens Examined. — Botaurus pinnatus caribaeus: Veracruz: 2 mi. W.
Tecolutla (3); 2 mi. E, 2 mi. S Tlacotalpan (2); Ingenio San Cristobal [=near
Cosamaloapan] (1); Lerdo de Tejada (5). Tabasco: 14 mi. S. Villahermosa (1) ;

Yucatan: 2 mi. S Progreso (1).

Botaurus pinnatus pinnatus: Costa Rica: Finca Taboga, Departmento de Guanacaste
(1) ; Nicaragua: 11 mi. S San Carlos, Departmento de Rio San Juan (1) ; El Salvador:
Laguna Jocotal, Departmento de San Miguel (1).

The specimens from Yucatan and El Salvador are the first record of the species from
those areas.

I wish to thank Dr. Thomas R. Howell, University of California, Los Angeles and
Dr. George H. Lowery, Jr., Louisiana State University, for permission to examine reeently
taken specimens in those respective colleetions. Scientific collecting permits were
provided by the Departmento de Conservacion de la Fauna Silvestre, Secretaria de
Agricultura y Ganaderia of the Mexican Government. — Robert W. Dickerman, De-
partment of Microbiology, Cornell University Medical School, New York, New York,
18 May 1971.

Chronology of hatching by laying sequence in Canada Geese. — Prince, et al.
< Auk, 86:762-763, 1969) found a high correlation between the sequence of laying and
the order of hatching in artificially incubated Mallard (Anas platyrhynchos) eggs. There
is no evidence of this same correlation in the Canada Goose {Branta canadensis) . During

90

March 1972
Vol. 84, No. 1

GENERAL NOTES

91

Table 1

Correlation of Laying, Pipping, and Emergence Sequence

Comparison

Number

of

Eggs

Correlation

Coefficient(r)

Percent

Variation

Explained(R)

Laying Sequence vs. Pipping

no

0.32**

10

Laying Sequence vs. Emergence

109

0.20

4

Pipping vs. Emergence

80

0.69**

47

(** p ^0.01)

a nesting study of Canada Geese conducted in the spring of 1971 on Marshy Point near
Clarkleigh, Manitoba, Canada, we made observations on the order of pipping and order
of emergence compared to the order of laying.

Nest searches were made during the egg-laying period in April. Nests containing one
egg were visited every other day and each new egg marked with a soft-lead pencil. After
the completion of the clutch, these nests were periodically revisted to check for destruction.
Hatching time was predicted by using a 28-day incubation period (Brakhage, J. Wildl.
Mgmt., 29:761, 1965).

We visited nests two days prior to the predicted hatching day and subsequent checks
were conducted every 12 hours to determine hatching progress. When emergence was
imminent, nests were inspected every four to six hours. Only those nests in which the
exact pipping and emergence sequence was known, those which contained a minimum
clutch of four eggs, and those in which at least 70 per cent of the original clutch hatched
successfully were included in the analysis.

A significant simple correlation coefficient was found between the pipping sequence
and the emergence of the goslings and between laying sequence and pipping sequence.
No significant correlation was found between laying sequence and emergence (Table 1).

Prince (op. cit.) found that 80 per cent of the variation in hatching sequence was ex-
plained by laying sequence; only four per cent of the variation in gosling emergence
was explained by laying sequence. The results of the two studies suggest possible species
differences and/or possible differences between natural and artificial incubation environ-
ments.

The average time required for a gosling to emerge once an egg was pipped was about
24 hours, agreeing with Collias and Jahn (Auk, 76:494, 1959), Brakhage (op. cit.:762).
and Macinnes (J. Wildl. Mgmt., 26:251, 1%2). The elapsed time between pipping and
emergence (range of 15-30 hrs.) was less than the 8 to 36 hour range reported by Kossack
(Amer. Midland Naturalist, 43:645, 1950).

If the last egg hatched l)etween daylight and early afternoon, the female left the nest
with the l)rood the following morning. However, if the last egg hatched in the late
afternoon or during the night, the female remained on the nest with the l)iood tlie
following day and did not lead them away until the morning of the second day. The
only variation in this behavior occurred when three females were frightened by us and
the dry goslings followed. The gander was never observed brooding dry goslings off of
the nest while the female was still incubating the remainder of the clutch as reported by
Kossack (il)id.).

The hatchahility of the eggs was 89 per cent; well within the normal range found for
Canada Cieese (Brakhage, op. cit.:767). One dead gosling was found in a n«*sl after

92

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

brood departure, and there were no desertions. The air temperature during the 15 day
period that the Iiatching checks were made averaged 48.2° F and ranged from a minimum
of 26° to a maximum of 70°. No precipitation fell during the hatching period and we
believe the study had no measurable effect on nesting success, hatching, or gosling
mortality.

This is a contribution of the Massachusetts Cooperative Wildlife Research Unit (sup-
ported by the U.S. Bureau of Sport Fisheries and Wildlife, the Massachusetts Division
of Fisheries and Game, the University of Massachusetts, and the Wildlife Management
Institute), the Massachusetts Agricultural Experiment Station and the Delta Waterfowl
Research Station. Thanks are due the owners of East Meadows Ranch for facilities
provided. — James A. Cooper and Jon R. Hickin, Department of Forestry and Wildlife
Management, University of Massachusetts, Amherst, Massachusetts 01002, 6 July 1971.

Spring migration of Swainson’s Hawk and Turkey Vulture through Veracruz,
Mexico. — At 15:40 hours, 22 March 1970, on Highway 180, 9 km west of Cardel, Veracruz
we observed a massive migration of Swainson’s Hawks (Buteo swainsoni) and Turkey
Vultures (Cathartes aura) heading generally north-northwest. The hawTs, apparently
all in typical adult plumage, were in loosely formed flocks of 75 to 200 birds flying
approximately 50 to 300 m above the ground. In 30 minutes we conservatively estimated
that 1,600 hawks passed overhead.

An approximately equal number of Turkey Vultures were migrating at the same time;
they tended to segregate into homogeneous flocks traveling at lower altitudes and wheeling
and turning more than did the Swainson’s Hawks. At 16:10 we continued south toward
Veracruz and obser\^ed flocks of migrating birds along the coastal plain to 28 km south
of Tamarindo. The weather was warm and overcast.

On 23 March, another overcast day, we encountered along the same route hundreds
of migrating birds 14 km south of Tamarindo. Again the Swainson’s Hawks tended to
be higher than the vultures, although the vultures outnumbered the hawTs. As soon as
we started up the mountains west of Tamarindo into heavy clouds, we no longer saw
migrating flocks.

On 26 March which was mainly overcast with a few short breaks of sunlight and a
strong wind off the Gulf of Mexico, we encountered migrating birds on Highway 180
12 km north of Vega de Alatorre at about noon. From there to Tecolutla we observed
thousands of vultures. Often they were just above the tops of the palms and other
trees bordering the Gulf, but we saw none over the water itself. Hawks were few,
although about 27 were over Puente Nautla at 12:13. The stratification of species
was still evident. Our northernmost observation was 32 km south of Poza Rica at 15:00.

The spectacular migration of both species through Central America has been noted
by many authors. In Veracruz Swainson’s Hawk migrations have been reported by
Loetscher (Auk, 72:14-54, 1955) near Las Vigas and Jalapa. SuttoP and Pettingill
(Auk, 59:1-34, 1942) witnessed migrating Swainson’s Hawks near Gomez Farias,
Tamaulipas, in April. Turkey Vulture spring migration in Veracruz was reported by
Wetmore (Proc. U. S. Natl. Mus., 93:215-340, 1943) and Bussjaeger et al. (Condor.
69:425-426, 1%7). Heretofore the extensive occurrence of both species migrating to-
gether this far north has not been reported. Monroe (Ornithol. Monogr. No. 7:1-458,
1%8) reported the two species together in Honduras. Dickey and van Rossem (Field
Mus. Nat. Hist., Zool. Ser. No. 23:1-609, 1938) noted migrating flocks of Turkey
Vultures and Swainson’s Hawks in El Salvador in the fall. They stated that hawks and

March 1972
Vol. 84, No. 1

GENERAL NOTES

93

vultures were “migrating as an integral part of the flight,” but they did not indicate
whether the species were stratified by altitude.

Swainson’s Hawk normally migrates at great heights (Monroe, ibid.; Skutch, North-
west Sci., 19:80-89, 1945), however, on overcast days they are forced to fly much lower
(Skutch, ibid.). The overcast weather coupled with the jutting mountains could have
funneled the hawks we observed toward the coastline. This idea is supported by
Loetscher’s observations of migrating Swainson’s Hawks in the vicinity of Jalapa and
Las Vigas on 5 April 1939. The weather at that time (4 and 5 April 1939) was mostly
fair and clear in the mountains (Loetscher, pers. comm.) and on the coastal plain at
Tejeria, west of the city of Veracruz (U. S. Weather Bureau records).

On 23 March 1970 the coastal plain was overcast; at Jalapa (elevation 1,400 m) we
were in the midst of the clouds, and at Las Vigas (2,450 m) we were above the clouds.
Since we observed migrating birds only on the coastal plain, this observation apparently
was an example of local weather conditions and topographic features affecting the
migration of these birds. — James R. Purdue, Charles C. Carpenter, Dale L. Marcellini,
University of Oklahoma, Norman, Oklahoma, and Robert F. Clarke, Kansas State
Teachers College, Emporia, Kansas, 16 June 1971.

An unusual nest of the Sandhill Crane. — On 7 May 1969 while conducting re-
search on Sandhill Cranes {Grus canadensis tabida) at Malheur National Wildlife Refuge,
Harney County, Oregon I discovered an unusual crane nest. The nest consisted of two
mounds of vegetation with an egg on each mound. One had the appearance of a normal
nest, while the other consisted of a small accumulation of broad-fruited bur-reed
(Sparganium eurycarpum) . The second mound was situated 73 centimeters south of
the normal structure.

The larger mound had the following measurements: basal diameter 110 X 138 cm;
crown diameter 69 X 50 cm; bowl diameter 22 X 25 cm; bowl depth 2.9 cm and nest
height above water 11.9 cm. The nest was in 17.8 cm of water and the egg which
measured 102.8 X 61.1 mm, was being incubated. The small mound had no definable
crown or bowl. It was 3.5 cm above water level in 10.5 cm of water. The egg measured
99.6 X 60.9 mm and had not been incubated.

When I disturbed the incubating bird it showed little interest in the nests; however,
a crane was observed incubating on 8 May. Re-examination of the nest in early June
revealed both eggs had been destroyed by a raccoon (Procyon lotor) .

Of 394 Sandhill Crane nests I have inspected on Malheur NWR, this is the first nest
observed where the eggs were not deposited on a single mound. I have seen several sites
where two mounds had been constructed, but only one was ever utilized. — Carroll 1).
Littlefield, Department of Biological Sciences, University of Arizona, Tucson, Arizona
85721, 16 August 1971.

Variability of tail molt in the Burrowing Owl. — Mayr and Mayr (Auk, 71:
172-178, 1954) described simultaneous tail molt in one museum specimen of the Burrow-
ing Owl iSpeotyto cunicularia hypugaea) as well as in other small owls. However,
Thomsen (Condor, 73:177-192, 1971) in her study of a population of 5. c. hypugaea
in California found simultaneous tail molt to he “not apparent.” Coulomhe (Condor,
73:162-176, 1971) did not study tail molt. This note documents the occurrence of
simultaneous or nearly simultaneous tail molt in a captive Burrowing Owl (5. c. jloridana)
and in a natural population of this subspecies.

94

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Fig. 1. Burrowing Owl in nearly simultaneous tail molt (dorsal view).

The captive, an adult female, was kept in a behavioral observation room at the Uni-
versity of South Florida. The bird was under a light-dark cycle set one month ahead of
the light cycle outside (i.e. the owl was subjected to March’s day length in February,
etc;). Between 27 March and 9 May, 1970, the captive was viewed through the ob-
servation room window and was not handled. When viewed on 9 May, the owl appeared
to have a normal tail but by 11 May, all rectrices had been lost. Examination (Fig. 1)
revealed 12 new tail feathers, 3 still in sheath and the remainder partially unsheathed.
Judging from the length of the central rectrices, molt must have been in progress before
9 May. On 2 June, no sheathing was seen near the base of the feathers and growth was
completed. Wing molt had commenced on 15 March and two primaries were in molt on
11 May. Based on the size relationships of the tail feathers (Fig. 1), the nearly
simultaneous molt had a centrifugal order of replacement. The right six rectrices were
slightly irregular in order with rectrix 2 being the longest, followed in order by rectrix
1, 3, 4, 6 and 5.

Tlie advanced light-dark cycle of the captive owl and the lack of a mate might explain
its early molt compared to molt in a natural population of 37 Burrowing Owls in the
vicinity of the University. Most owls in the natural population were observed at least
twice a week. Eight of these birds were observed to undergo a simultaneous tail molt.
Four owls were seen with all new rectrices in sheath and equally long, while the other
four were seen with new rectrices partially unsheathed but appearing to be of equal
length (unlike Fig. 1). By 6 August, the new tails were between one-third and one-
half developed. At the start of simultaneous molt, the eight birds (4 females, 3 males,
and one unsexed) either had no young or had flying young at least 11 weeks old. Each

March 1972
Vol. 84, No. 1

GENERAL NOTES

95

bird had begun wing molt before the onset of tail molt. The flight of owls lacking
functional tails seemed unimpaired except for the takeoffs which were slow and wobbly
when compared to takeoffs with normal length rectrices. The effect of simultaneous
tail molt on aerial foraging was not observed.

The other 29 owls did not undergo a simultaneous tail molt during the summer of
1970. Some of them were known to have undergone a gradual tail molt. Two were seen
to begin gradual tail molt by loss of the central rectrices first when their young were 30
days old. It is interesting to note that the simultaneous tail molt in the field occurred
after the young had reached some measure of independence and that a majority of the
wild, breeding population did not undergo a simultaneous or nearly simultaneous tail
molt.

These results supplement Mayr and Mayr’s (loc. cit.) finding of a simultaneous tail
molt in a museum specimen of S. cunicularia. Burrowing Owls can successfully secure
insects on the ground without flying. If these owls can capture a sufficient number of
prey on the ground, then the short period of complete tail loss may only represent a slight
hindrance to foraging activities of the species.

The Department of Zoology, University of South Florida provided support for the work.
Noel Snyder and Andrew J. Meyerriecks provided helpful comments on the manuscript. —
William D. Courser, Department of Zoology, University of South Florida, Tampa,
Florida 33620, 9 June 1971.

Another record of a short incubation period for the Robin. — Taft’s note
(Audubon Field Notes, 24:652, 1970) on the possible 7- or 8-day incubation period for a
Robin iTurdus migratorius) prompts me to add a verifying observation made by one
of my students, Ruth Ellen Sands, in 1956 in Athens, Ohio. She found a nest with 2
eggs on 20 April. On 22 April there were three eggs, the third having been laid between
noon of 21 April and noon of 22 April. The three eggs hatched during the day on
30 April, from 8 to 8h^ days after the laying of the last egg. All three young left the
nest on 16 May, 2 in the morning and one around supper time. — Henri C. Seibert,
Department of Zoology, Ohio University, Athens, Ohio 45701, 10 June 1971.

Discovery of the nest of the Kauai Akepa. — The Hawaiian Islands are inhabited
by a unique family of birds — the Hawaiian Honeycreepers (family Drepanididae) . Of
the twenty-two full species of drepanidids, eight are already extinct and eight others
currently considered to be in danger of extinction (Fisher, Simon, and Vincent,
Wildlife in danger. New York, 1969). The six remaining species have at least one race
each in danger of extinction.

The Akepa (Loxops coccinea) has distinct subspecies on four of Hawaii’s main
islands: Loxops coccinea caeruleirostris on Kauai; L. c. rufa on Oahu; L. c. ochracea on
Maui; and L. c. coccinea on Hawaii. The species is fairly common only in the Alakai
Swamp region of Kauai, less common at Kokee State Park on Kauai; it is extinct on
Oahu, and rare on both Maui and Hawaii.

The nest, eggs, and nestlings have not been described previously for any of the sub-
species of Akepa. Perkins lAves. in Fauna Hawaiiensis 1 (4) :3f)5-466, PX)3) wrott*:

“On one occasion I saw a pair of the Maui species building their nest high up in a
tall ohia, near the extremity of a liori/.ontal brancli. Both sexes k<*pt coming to the
ground for material and were carrying off the wooly down or ‘pidu’ of sonn* stunt(Ml tree-
ferns, probably as a lining for the nest. This was so well concealed that even with glasses

96

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Fig. 1. The exterior of an Akepa nest to show method of nest attachment.

I was unable to make out the details of structure with any certainty, and the eggs and
unfledged young I have not seen.” I have found no other references to the nests of
any subspecies of Akepa.

I discovered the first Kauai Akepa nest in Kokee State Park on 9 March 1969, while
conducting a study of the breeding biology of four more common species of drepanidids
(Amakihi {L. virens) , Anianiau (L. parva) , Apapane ( Himatione san guinea) , and liwi
(Vestaria coccinea)). The Akepa is not common in the Kokee area but I have seen as
many as five in one day of field work there. The nest was in the terminal crown of a
non-blooming ohia tree (Metrosideros) , 30.5 feet above the ground. The top of the tree
was too thin to support my weight but I was able to see into the nest by using a mirror
attached to the end of a six-foot pole. The nest was empty and appeared incomplete in
that one side was still thin. After checking the nest I concealed myself in the underbrush
beneath the tree. I then saw one bird fly to the nest, hop in and remain for two or three
seconds, after which it flew down to within 15 feet of me. I could plainly see that it
was an Akepa. It gave repeated call notes and then flew back to the nest.

I watched both the male and female Akepa adding material to the nest. Between
8:30 and 10:30 on 11 March, each added material eight times. The male often sang
from a tall neighboring ohia tree as the female was adding to the nest. His song was
a high trill, higher in pitch and shorter in duration than the song of the Anianiau. The
male also uttered a variety of whisper songs, similar to those of the Amakihi.

I observed courtship feeding on several occasions, usually on a branch a short distance
from the nest but once on a branch only three feet from the ground. The female
solicited feeding by crouching slightly, depressing and quivering her wings, and giving
a vocalization similar to that of a fledgling begging for food.

A pair of Apapane were building in a neighboring ohia tree 40 feet from the Akepa
nest. On several occasions the Apapane flew to the Akepa nest, pulled loose nesting
material, and added it to their own nest. This stealing was usually done during the
absence of the Akepa but on 14 March an Apapane flew to the nest while the Akepa
were present. The male Akepa gave the alarm call and chased the Apapane from the nest

March 1972
Vol. 84, No. 1

GENERAL NOTES

97

Fig. 2. The Akepa nest is lined with soft bark fragments.

and through several nearby trees, but in less than 15 minutes the Apapane returned and,
in the absence of the Akepa, again took material from the nest. The Akepa were still
adding material on 18 March. On 27 March I found half of an egg shell on a branch
about a foot below the nest. The shell fragment looked very much like the eggs of the
other drepanidids — white with irregularly shaped brown markings. The lining had
been torn out of the nest and neither adult was near. I continued to observe the nest
until 4 April but never saw the Akepa near it again.

The construction of the Akepa nest differs from that of the Apapane in that fewer
twigs and coarse materials are employed, the Akepa nest being composed largely of
mosses. Construction is less compact so that from the ground the nest appears quite
large. Measurements were as follows: rim thickness, % to IV2 inches; outside diameter,
314 to 4fV2 inches; measurement from the top rim to the bottom of the nest, 414 inches;
inside diameter of the nest cup, 1% to 214 inches; depth of the nest cup, 1% inches.

In 1970 I found two inaccessible Akepa nests, the first on 26 March and the second
on 11 April. I estimated their heights to be approximately 40 feet above the ground.
Both were in the terminal crowns of non-blooming ohia trees. The first nest was under
construction when I found it and I observed courtship feeding in this pair. The second
probably contained eggs because the female spent periods of 15 to 20 minutes in the
nest.

On 29 March 1970 I found an accessible Akepa nest 37.5 feet above the ground in die
terminal crown of a non-blooming ohia tree. The nest appeared to lie complete wluui
I found it. The first egg was laid in this nest on 2 April, the second on 3 April. The
eggs measured 16.6 X 13.3 mm and 16.6 X 13.1 mm. They had a whitish background
with irregularly shaped dark brown markings scattered over the entire surface, but more
concentrated at the large end of the egg. On 4 March the nest lining had been pulled
up, burying the two eggs. I observed the nest until 6 April when it was apparent diat
it had been deserted. I broke one of the eggs to see the yolk. It was yellow, as in
the eggs of the Amakihi and Anianiau, as opposed to orange as in Apapane and liwi
eggs.

Travel funds for this study were provided in part ky grants from the Chapman
Memorial Fund, the Eastern Bird-Banding Association, and by National Science lounda-
tion Grant GB-5612, awarded to Andrew J. Berger. — C. Komkht Eddingkh, Department
of Zoology, University of Hawaii, Honolulu, Hawaii 96822, 6 May 1971 .

98

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Mobbing of a Fish Crow by passerines. — Mobbing of hawks, crows, and other large
birds by passerines is a common behavior seen during the breeding period. Often the
factors evoking this aggressiveness are difficult to determine, and there are few published
papers relative to the effectiveness of mobbing by small passerines. The following account
regarding a Fish Crow {Corvus ossijragus) and several passerines gives information on
cause and effectiveness of this incident of mobbing behavior. The observations were
made at Winter Park, Seminole County, Florida.

In late afternoon of 15 May 1971, a cloudy day, loud distress calls of Mockingbirds
iMimus polyglottos) and Red-winged Blackbirds (Agelaius phoeniceus) attracted my
attention. About 250 feet away in a pine-palmetto habitat bordered by a drainage ditch,
three Mockingbirds and at least three Red-winged Blackbirds were vigorously mobbing
an unmarked Fish Crow. The passerines directed their beaks at the crow’s body, and
the most frequent area hit was the back. After about three minutes the crow flew to and
perched in one of four closely-spaced pine trees located about 25 feet from the mobbing
area. The passerines then perched in the pines but continuously gave raucous calls. In
less than two minutes the crow, followed by the passerines, flew from the trees and
returned to the area. The mobbing resumed. A calling Blue Jay {Cyanocitta cristata)
flew to the scene and participated with the Mockingbirds and Red-winged Blackbirds.
Again the birds returned to the pines; the crow was panting. Initially I had the impres-
sion that the crow accidently came in contact with the passerines and was trying to
escape. During the second mobbing incident it seemed clear the crow was not trying to
escape since it kept returning to the same area. After two more similar mobbing bouts,
the crow, while hovering somewhat, succeeded in its efforts and took a squealing, well-
feathered bird from a nest. The distress calls of the passerines became louder. The
crow immediately flew away with the young bird dangling from its beak. One Mocking-
bird continued to chase the crow as both birds flew out of sight beyond a distance of
1000 feet in an area of several large pine trees. The Mockingbird shortly returned to
the mobbing area. I am not sure if the nestling was a Mockingbird or Red-winged
Blackbird. Active nests of both species were found in the mobbing area. After about
five minutes later, much to my surprise, a crow, presumably tbe same bird since it came
from the direction where the other crow made its exit, returned to the area and the
mobbing behavior resumed. This crow began hovering in the same area as before as
the calling passerines mobbed the intruder. The crow was undoubtedly after another
nestling. During these hovering movements a sudden heavy rain began. The crow
flew away and the passerines dispersed. — -Walter Kingsley Taylor, Department of
Biology, Florida Technological University, Orlando, Florida 32816, 24 May 1971.

Vesper Sparrow nests abandoned after snow. — During the period 8-10 June 1970,
three Vesper Sparrow (Pooecetes gramineus) nests, each with four eggs, were found on
a small watershed study site 14 miles west of Saratoga, Wyoming. The nests were
located under partially dead sagebrush plants on an upland sagebrush site at about
7,850 feet elevation. On 11-12 June 1970, an unseasonable snowstorm, preceded by a
one-half-inch rain, deposited 4 to 6 inches of snow on the nesting area. Accompanying
this storm was a cold air mass that substantially lowered both daytime and nighttime
air temperatures. Temperature extremes for the 10 successive days before, during, and
after this storm were: 6 June, 40°-60° F. ; 7 June, 40°-65°; 8 June, 44°-68° ; 9 June
44°-56°; 10 June, 35°^°; 11 June, 31°-36°; 12 June, 31°-46°; 13 June, 33°-h9°;
14 June, 39°-58° ; and 15 June, 44°-58°. The nests were visited again on 22 June, and
all were found abandoned. Upon examination, tbe now spoiled but still intact eggs

March 1972
Vol. 84, No. 1

GENERAL NOTES

99

were found to have been fertile, with absorption of the yolk sacs well advanced. Since
the adult birds continued to incubate, both during and after previous visits to their nests,
I believe that abandonment was caused by the accumulated snow at the nest sites.
Frequent visits to the nesting area in the following weeks did not reveal any attempts
to reuse the abandoned nests. — Max H. Sciiroeder, Bureau of Sport Fisheries and Wild-
life, Denver Wildlife Research Center, Denver, Colorado, 9 April 1971.

Records of the Scarlet Ibis and Red-breasted Rlackbird in Ecuador. — In

their book. The Species of Birds of South America (Acad. Nat. Sci., Livingston Publ. Co.,
1966), Meyer-de Schauensee and Eisenmann did not include Ecuador in the stated range
of the Scarlet Ibis {Eudocimus ruber) or the Red-breasted Blackbird (Leistes militaris) .
This fact leads me to place on record my observations of these species made in 1964
at Limon Cocha (Oriente Province), Ecuador, near the junction of the Rio Napo and Rio
Jivino:

Scarlet Ibis. — One seen on 7 May at less than 50 feet in trees at the edge of the lake.
Palmer (Handbook of North American Birds, Vol. 1, Yale Univ. Press, p. 530, 1962)
stated that the plumage sequence in this ibis is “almost entirely unknown.” The bird I
saw was a mosaic of gray and scarlet patches, the arrangement reminiscent of that in
some blue-and-white immature Little Blue Herons {Florida caerulea) .

Red-breasted Blackbird. — Small numbers were seen in a pasture from 25 April into
early May. Of 5 specimens collected, 2 are now in the Museum of Zoology at Louisiana
State University, the others at Florida State University. — Henry M. Stevenson, Depart-
ment of Biological Sciences, Florida State University, Tallahassee, Fla., 32306, 26 July
1971.

publication notes and notices

Die V5gel des Bodenseegebietes. By H. Jacoby, G. Kndtsch, and S. Schuster.

Schweizerische Gesellschaft fiir Vogelkunde und Vogelschutz, Wintertlmr, Switzerland,

1970: 6 x 9 in., 260 pp., 26 photos, plus graphs, maps. Swiss Francs 18.50.

“The Birds of the Lake Constance Region” summarizes many years of ornithological
research around that large lake on the border of northern Switzerland and southern
Germany. This report was compiled by three workers with the cooperation of many
other individuals, and the whole was sponsored by the Swiss Society for Bird Study
and Bird Protection. It provides an excellent example of how intensive bird study in one
small region can he summarized, and it pictures the birds in another continent but one
with similar vegetation, agriculture, and human uses of the landscape to that found in
eastern North America. — James T. Tanner.

ORNITHOLOGICAL NEWS

The Chairman of the Program Committee for the Annual Meeting is Dr. Elden W.
Martin, Department of Biology, Bowling Green State University, Bowling Green, Ohio
43402. Members and others who desire to present papers at the meeting may contact
Dr. Martin at any time even though the official call for papers has not appeared.

At each Annual Meeting a Committee on Resolutions is appointed, and certain resolu-
tions are adopted by the membership. Frequently this Committee is handicapped by a
lack of information about matters on which it would be appropriate that the Society
take a formal stand. Any member, whether intending to be at the Meeting or not. who
knows of a conservation matter upon which he thinks a formal resolution of the
Society would be helpful, should send particulars to the .Secretary in advance of the
Meeting.

Two new Patrons of the Society are Olin Sewall Pettingill, Jr. and Paul A. Stewart.

E. Alexander Bergstrom has retired as editor of Bird-Banding after 21 years at the
post. The new editor is David W. Johnston of the University of Florida.

Ralph J. Raitt has retired as editor of The Condor. The new editor is Francis S. L.
Williamson of the Chesapeake Bay Center for Environmental Studies.

The annual meeting of The Eastern Bird Banding Association will be held at Ithaca,
New York, 21-23 April 1972. The annual meeting of the Western Bird Banding Associa-
tion will be held at Sunriver, Oregon on 10-11 June 1972.

The Terra Alta Biological Station of West Virginia University announces a special
early session. May 15 to 9 June. Courses in ornithology, herpetology, and plant taxonomy
will be offered. The early dates are to coincide with the height of seasonal activity in the
fields concerned. Inquiries should be directed to Robert L. Birch, Department of Biology,
West Virginia University, Morgantown, West Virginia 26506.

100

CONSERVATION SECTION

BIRD DAMAGE TO CORN IN THE UNITED STATES IN 1970

Charles P. Stone, Donald F. Mott, Jerome F. Besser
AND John W. De Grazio

Accurate assessments of agricultural losses to birds are difficult to obtain, but are
fundamental in evaluating the necessity for, and effectiveness of, damage control. Some
estimates of statewide losses have been made, but most extensive surveys to date have
had little empirical basis, cannot be compared statistically, and were subject to many
biases.

The results of the first nationwide survey of bird damage to corn are reported in this

Table 1

Damage Patterns in 24 Major Corn-producing States in 1970

Com
acreage
( thousands )

Counties

Fields

Com

ears

State

Number % with
surveyed damage

Number

surveyed

% with
damage

Number

examined

% with
damage

Alabama

545

36

16.67

61

9.84

1,152

1.04

Florida

322

19

0.00

79

0.00

1,365

0.00

Georgia

1,426

61

4.92

105

2.86

2,641

0.57

Illinois

10,066

78

15.38

188

7.44

6,848

0.45

Indiana

5,027

79

16.46

147

10.88

5,277

1.06

Iowa

9,990

89

1.12

197

1.02

6,897

0.03

Kansas

1,285

38

7.89

112

3.57

3,267

0.15

Kentucky

988

56

33.93

110

18.18

3,043

2.50

Maryland

484

19

57.89

92

19.57

2,538

3.55

Michigan

1,444

37

45.95

116

25.00

3,891

4.81

Minnesota

4,594

49

20.41

158

8.86

7,623

1.08

Mississippi

248

43

37.21

73

28.77

1,305

5.21

Missouri

2,837

63

6.35

150

3.33

4,100

0.27

Nebraska

4,897

60

5.00

169

1.78

5,374

0.13

New’ York

279

29

62.07

75

41.33

2,698

6.92

North Carolina

1,345

61

11.48

143

4.90

4,709

0.28

Ohio

3,014

60

31.67

133

19.55

4,684

2.82

Pennsylvania

943

37

64.86

121

34.71

3,844

8.32

South Carolina

402

27

40.74

95

16.84

2,262

2.17

South Dakota

2,496

39

33.33

105

18.10

2,606

1.42

Tennessee

569

38

34.21

91

19.78

2,246

1.60

Texas

531

35

8.57

128

4.69

3,070

0.68

Virginia

458

46

21.74

73

12.33

2,294

2.53

Wisconsin

1,794

46

32.61

133

15.04

4,8%

2.45

Totals and

means

55,984

1,145

21.92

2,854

15.60

88,630

1.82

101

]02

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

Wise.

_|_ TEXAS

I TENN.

I S. DAKOTA
I S. CAROLINA

I OHIO

I N. CAROLINA

NEBR.

MO.

I MISS.

MINN.

_ MICH.

PA.

NEW YORK

I KANS.

lA .

j IND.

I ILL.

I GA.

I ALA.

' OJ a2 o3 04 05 06 07 08 09 l!o LI L2 L3 L4 Ts L6 L7 L8

BU/ACRE LOSS

Fig. 1. State corn losses to birds in 1970 (mean bu/acre loss and 95 per cent confidence
limits) .

paper. The data were collected in a similar manner in each state, and a statistical ap-
proach permitted establishment of confidence limits on damage estimates. Valid com-
parisons of data from the various states are thus possible for the first time. The approach
also permitted the mapping of damage according to presence or absence in the counties
surveyed. For the states with which we are most familiar, the pattern appears realistic,
and for other states it is revealing, but merits further study.

METHODS

The 1970 bird damage survey was conducted under an interagency agreement between
the Bureau of Sport Fisheries and Wildlife and the Statistical Reporting Service (SRS)
of the U.S. Department of Agriculture. Enumerators employed by the USDA to conduct
the annual Objective Yield Survey for corn, were introduced to bird damage in different
stages of corn maturity through a slide series and handouts prepared by the authors.

The sampling frame employed by the SRS during their final pre-harvest survey was
used to estimate bird damage. Enumerators were asked to complete an additional form
relating to bird damage for the fields normally surveyed. Fields were randomly chosen
and two 15-foot units of two rows each were randomly established in each field. Enumer-
ators recorded the number of ears of corn with kernels in the first row in each unit.
They also measured the average length of damaged and undamaged kernel rows to the
nearest 0.1 inch for each damaged ear in the first row of each unit. Bureau personnel

March 1972
Vol. 84, No. 1

CONSERVATION SECTION

103

Estimated State

Table 2

Corn Loss to Birds in 1970

Mean bu/acre

Mean bushel

Mean dollar

State

loss ± S.E. (too)

loss ± S.E. ( t05)

loss!

Alabama

0.0774 ± 0.1132

42,183 ± 61,694

$ 63,275

Florida

0.0000 ± 0.0000

—

—

Georgia

0.1296 ± 0.2351

184,810 ± 335,253

277,215

Illinois

0.0540 ± 0.0363

543,564 ± 365,396

815,346

Indiana

0.1716 ± 0.1607

862,633 ± 807,839

1,293,950

Iowa

0.0018 ± 0.0027

17,982 ± 26,973

26,973

Kansas

0.0811 ± 0.0969

104,214 ± 124,517

156,321

Kentucky

0.2651 ± 0.1941

261,919 ± 191,771

392,879

Maryland

0.2542 ± 0.1492

123,033 ± 72,213

184,550

Michigan

0.3356 ± 0.2400

484,606 ± 346,560

726,909

Minnesota

0.08% ± 0.0678

411,622 ± 311,473

617,433

Mississippi

0.4253 ± 0.2584

105,474 ± 64,083

158,211

Missouri

0.0114 ± 0.0141

32,342 ± 40,002

48,513

Nebraska

0.0140 ± 0.0165

68,558 ± 80,801

102,837

New York

1.1791 ± 0.6761

328,%9 ± 188,632

493,454

North Carolina

0.0426 ± 0.0386

57,297 ± 51,917

85,946

Ohio

0.2180 ± 0.1373

657,052 ± 413,822

985,578

Pennsylvania

0.8957 ± 0.4732

844,645 ± 446,228

1,266,968

South Carolina

0.0750 ± 0.0577

30,150 ± 23,195

45,225

South Dakota

0.0812 ± 0.0606

202,675 ± 151,258

304,013

Tennessee

0.1271 ± 0.0868

72,320 ± 49,389

108,450

Texas

0.0257 ± 0.0255

13,647 ± 13,541

20,471

Virginia

0.2983 ± 0.3559

136,621 ± 163,002

204,932

Wisconsin

0.2861 ± 0.2086

513,263 ± 374,228

769,895

1 At $ 1.50/bushel.

converted tlie length data to weight of corn lost (in grams) through use of the mathemati-
cally generated table developed by De Grazio et al. (J. Wildl. Mgmt., 33:988-994, 1969).
It is possible that the table underestimates damage somewhat, and this is being checked
at present. Confidence limits were established at the 95 per cent level for husliel-per-acre
losses in each state and for total bushel losses for the 24 states surveyed. The data for
each state were weighted according to corn acreage grown in order to calculate the
overall mean and confidence interval (Cochran, Sampling Techniques, 1953). The 24
states surveyed accounted for 98 per cent of the acreage harvested and for 97.5 per cent of
the corn produced in the United States in 1970, according to the SRS.

RESULTS AND DISCUSSION

The estimated mean of the direct corn loss to birds in the 24 states was 0.1112 ±
0.1880 hu/acre, or 6,225,421 ± 10,524,992 hu (95 per cent confidence limits). At S1.50/hu,
the dollar loss amounted to $9,338,132 ± 15,787,488. Based on USDA i)roduction figures,
birds accounted for 0.16 ± 0.26 per cent of the total corn crop in the 24 states in 19<0.

Corn damage according to numbers of counties and fields surveyed and ears damaged

104

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

in each state is summarized in Table 1. Kentucky, Maryland, Michigan, Mississippi, New
York, Ohio, Pennsylvania, and South Carolina showed higher than average damage by
all three analyses. These states also suffered relatively high bushel-per-acre losses, although
the confidence intervals overlapped considerably with those of other states (Fig. 1). It
is evident, however, that bushel-per-acre losses were particularly high in New York and
Pennsylvania and comparatively low in Texas, North Carolina, Nebraska, Missouri, Iowa,
and Illinois.

The greatest economic losses, determined by a combination of considerable acreages of
corn and relatively high bushel-per-acre losses, occurred in Illinois, Indiana, Michigan,
Minnesota, Ohio, Pennsylvania, and Wisconsin (Table 2). However, high bushel-per-acre
losses in states with relatively low acreages of corn (such as New York) are of obvious
importance to the growers involved. The low bushel-per-acre losses in Iowa and Illinois,
which together accounted for 35.8 per cent of the corn acreage in the 24 states, are
noteworthy.

Counties that contained at least one survey field, and those in which at least some bird
damage occurred in 1970, are shown in Figure 2. Probably damage in 1970 was lessened
by the rapid corn maturation and early harvest, which resulted in part from an infestation
of southern leaf blight.

March 1972
Vol. 84, No. 1

CONSERVATION SECTION

105

SUMMARY

The first nationwide survey of bird damage to corn was conducted in 1970; 24 states
producing over 97 per cent of the U.S. corn crop were sampled. The total direct loss to
birds was estimated to be 6,225,421 bushels ± 10,524,992 bushels (95 per cent confidence
limits) . New York and Pennsylvania suffered the high losses per acre, and Indiana,
Illinois, Wisconsin, Ohio, Pennsylvania, Michigan, and Minnesota showed high total losses.

ACKNOWLEDGMENTS

We wish to thank John L. Oldemeyer of this Center for statistical advice, and Ann H.
Jones, also of this Center, for editorial comments.

BUREAU OF SPORT FISHERIES AND WILDLIFE, DENVER WILDLIFE RESEARCH CENTER, DENVER,

COLORADO 80225, 22 October 1971.

PUBLICATION NOTES AND NOTICES

A Natural History of New York City. Revised and abridged edition. By John Kieran.
Published for The American Museum of Natural History by The Natural History
Press, Garden City, New York, 1971: 4^2 X 714 in., paper covered, viii 308 pp. $2.95.

This is a revised and updated edition of the original book published in 1959 ( and
favorably reviewed in The Wilson Bulletin, 72:298, 1960). Mr. Kieran tells not only a
great deal about the natural history of his city, but also how to see often inconspicuous
plants and animals. His enthusiasm for his subject should arouse many New \orkers to
seek it for themselves. They will be amazed to find how much wildlife remains in spite of
environmental decay. The illustrations that graced the original edition have unfortu-
nately been deleted from this one.- — P. S.

Ecology of Colorado Mountains to Arizona Deserts. By Helen Moenke. Museum
Pictorial No. 20, Denver Museum of Natural History, Denver, Colorado, 1971 : 6 X 9 in.,
paper covered, % pp., many col. and hi. and wh. photos. $2.50.

This booklet is accurately self-described as “An interpretive study of the ecology of
plants and animals exhibited in life zone habitat groups in the Walter C. Mead Ecological
Hall of the Denver Museum of Natural History.” Based on these exhibits, the tt'xt
discusses ecological relationships in seijuence from the alpine tops of (Colorado's Rocky
Mountains down through the life zones to the Sonoran deserts of Arizona. Photogi ■aphs
of these superlative exhibits and of plants and animals in nature are included. 4 he
booklet is edited by Alfred M. Bailey, and therefore is up to the high standards of
previous Museum Pictorials. It will help travelers in (Colorado to see behind the
scenery. — P. S.

ORITHOLOGICAL LITERATURE

An Approach to the Study of Ecological Relationships Among Grassland Birds.

By John A. Wiens. American Ornithologists’ Union Ornithological Monographs, No. 8,
1969: 6% X 10 in., 93 pp., 30 figs., 17 tables. $2.50.

The urge to quantify has recently made its way to one of the last strongholds of de-
scriptive ornithology, the study of breeding biology. This monograph presents three
years of quantitative data on the ecology of seven species regularly breeding in Wisconsin
grasslands: Bobolink, Eastern Meadowlark, Western Meadlowlark, Savannah Sparrow,
Grasshopper Sparrow, Henslow’s Sparrow, and Vesper Sparrow.

As Wiens states his goals, they “. . . were to develop and test a method for describing
and analyzing habitats which would be useful in elucidating ecological relationships
among grassland birds.” His methodology consists of habitat description — using vegeta-
tion type, coverage and height, vertical light penetration, substrate and topographic
descriptions; vegetation sampling via the point method; demarkation of the territories of
birds present; and recording habitat utilization by continuous tape recorded observations
of the birds present.

In addition to the development of an efficient and adequate means of habitat analysis,
several important relationships among the inhabitants are delineated. Their territories
varied throughout the season as well as yearly, but only the Eastern and Western Meadow-
larks had mutually exclusive territories. While the territories of all species had many
physiognomic aspects in common, the territory of each species was somehow distinctive.
Bobolinks preferred dense tall vegetation with its associated deep litter and low light
penetration, while Vesper Sparrows preferred short, sparse vegetation with little litter
and high light penetration. Differences among the species also appeared in the
frequencies and sites of performance for daily activities. Wiens found evidence of a
dominance relationship among the species in the study which, together with their
ecological differences, tended to reduce direct competition sufficiently to allow co-
occupancy of this relatively homogeneous environment.

This is an excellent paper for the novice ecologist to peruse. It clearly presents
methodology in detail and its application in daily field work is easily followed. More
than most modern field studies, this monograph also pauses to theorize a bit. What were
the theoretical considerations which prompted Wiens to undertake this study? What were
the problems in the development of his methodology and the consequent changes they
wrought from 1964 to 1966? The graphic representations throughout are clear and easily
understood. Such inclusions make this monograph particularly exemplary to the conduct
of scientific research.

Alternatively, these same inclusions engender much of the criticism I might make of
this paper. Of ter Wiens is less than concise in the presentation of his ideas. In the de-
velopment of his methodology, I found myself wishing he would simply state exactly
what he did, and stop. Yet the comparison between sampling methods and their relative
value and efficiency is instructive. Several of his points on theoretical ecological considera-
tions are well taken, but often overly verbose. On pages one and two, Wiens theorizes
that his bird species chose this grassland habitat on the basis of specific features of the
habitat rather than on the presence of ultimate limiting factors imposed on them there;
and regardless of the species, it remains constant in selecting the physiognomy of this
habitat. The point is well taken, but supported by an excess of examples. On page five,
he overstates the point, though a good one, that ecologists in their use of arbitrary

106

March 1972
Vol. 84, No. 1

ORNITHOLOGICAL LITERATURE

107

categorization of a community for ease of analysis, often neglect to put the whole baek
together again.

Again in paragraphs two, three, and four on page 12, Wiens makes several good
points, but is unnecessarily complex in their statement. I had the feeling here that he
was holding up his side of an argument against imagined opposition. This is more the tone
of a dissertation than of a monograph.

Yet in following the format of an instructional monograph, Wiens occasionally assumes
too much knowledge on the part of his reader. In such a “standard operating procedure”
for grassland habitat description with regard to birds, more references (see pages 17
and 18) might have been included, particularly basic ones. So long as diversity values
are discussed on page 81, a brief inclusion of the parameters included in this index
would be more instructive and meaningful: how large were the survey units; how were
they selected; are the diversity values based on unit area?

Of lesser import are occasional lapses in organization or presentation. The last para-
graph on page five would have adhered to the paper better had a topic sentence intro-
duced the ideal approach to the study of animal habitats — through the animal itself.
The map symbols used on page 32 are not explained until page 48; although readers
are referred to page 48 for explanation, this arrangement is inconvenient. The brief
comments on range ineluded species by species on pages 34 to 41, as well as information
on site preference, might better have been included in the discussion beginning on page
81 where Wiens discusses these subjects in detail. On page 37, much of paragraph one
seems of historical import but irrelevant to the present paper, as do the brief behavioral
comments later on that page.

From time to time I encountered seeming omissions in the full development of an idea.
On page 44, the Western Meadowlark is listed as one of the species that arrives early
on territory, yet in Table 7 on page 46, the species isn’t included until 15-25 May.

I would have found useful a comparison of Tables 11 and 13. And I would have
found interesting further development of the idea that “The utilization of a habitat by a
species is to a large degree dependent upon the relative frequencies of various activities
in the total activity repertoire of the species.” These frequencies determine the utilization
import or dominance, but which utilizations dictate a preference for the habitat selected?
The most dominant utilization need not be the most determining one.

I found the greatest strength of this monograph to be in its tlieoretieal approach to
the description of vertebrate habitats as is well stated on page 13, and the subsequent
parameters of habitat measurement as outlined in Table 2. The description and com-
parison of territory characteristics, given between pages 44 and 64, are very well done
and constitute the life force of this paper. — D. Jean Tate.

Birds of Isla Grande (Tierra del Fuego). By Philip S. Humphrey, David Bridge,

Percival W. Reynolds, and Roger Tory Peterson. Preliminary Smithsonian Manual.

Published and distributed for the Smithsonian Institution by the University of Kansas

Museum of Natural History, 1970: 8Y2 X H in., viii + 411 pp., 8 maps, 21 pis. by Jack
R. Schroeder. $7.00.

The southernmost part of South America, formed by the Straits of Magellan and Tierra
del Fuego together with adjacent archipelagos and islands, has long been sul)ject to
ornithological observations. Scattered reports have been published since 1830 but there
has not been any complete work on the avifauna of this region. The present l)ook, which
deals with the northern part of the Fuegian region (the “Isla Grande”), has been
written in order to help overcome this lack. It is unfortunate that the archipelagos and

108

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

islands off Isla Grande were left out, because it would have been logical to treat the
whole Fuegian region in one volume. On the other hand, knowledge of the distribution
of birds on the many southern islands is so sparse that the authors were justified in
omitting them. Wisely they were modest, avoiding guesses and hypothetical statements.

The hook is meant to facilitate field identification and to he a reference for data
on seasonal and geographic distribution and on ecology. Providing this much information
has created a hook that weighs about two pounds; while it is excellent at the desk, it is
most uncomfortable in the field. It would have been better to publish this work in
two parts — one on distribution and species accounts, and the other a guide to the species,
with field marks, habits, and habitats for each. As it is, one wonders if anyone would
not hesitate to carry this book in the field. It would be lamentable not to take the book,
because it is really full of information.

The authors have included almost everything that has been published about the birds
of Isla Grande, an immense task. The unpublished manuscript of the late Percival W.
Reynolds was an important source of information, and for this reason Reynolds is listed
as a co-author. The work is divided into several sections — “History of Ornithological
Exploration,” “Geography and Environments,” “Avifauna of Isla Grande,” “Species
Accounts,” and “Field Identification.” The most important section is that of the species
accounts, each of which has subsections on distribution and status, habits, reproduction,
vocalization, general notes, description, weight, and specimens known to have been
collected. The maps show details of different parts of the island and the plates show
most of the birds found in Fuegia.

I found no errors worth mentioning in the species accounts, but I would like to offer
some comments. The term “nonbreeding resident” does not fit species which actually
breed in Fuegia, such as Eudyptes crestatus, Diomedea melanophrys, D. chrysostoma, and
Macronectes giganteus, but species which do not breed in the region, such as Daption
capensis and Fulmarus gJacialis. Subspecies are not mentioned, but in certain cases
it would have been well to call attention to little known forms, such as Milvago chimango
fuegensis ( Johnson and Behn, Supl. Aves. de Chile, p. 353, 1957). Gallinago stricklandi
breeds in bushy or wooded damp areas, not marshes, like the habitat of G. media, Philohela,
and Scolopax; during migration, however, the species appears in grasslands. In regard
to certain species of terns, I think it would be sensible not to accept any sight records.
There are several similar species along the coast of Argentina, such as Sterna hirundinacea
(both southern and Brazilian populations, with different breeding cycles), S. hirundo
(in the southern summer appearing in great numbers as far as Santa Cruz), S. vittata
(wintering in Buenos Aires and Uruguay), perhaps S. paradisea, in addition to which
both S. forsteri and S dougallii can be expected; the different plumages of these birds
are apt to be confusing. Species which certainly appear or can be expected to occur
in the area of Isla Grande are, for example, Phoebetria fusca (recorded off Cape Horn),
Pachyptila tartar (breeds on Beauchene Islets, southwest of the Falkland Islands),
Phalacrocorax boagainvillii (breeds in Chubut, Argentina, and has been reported from
the Straits of Magellan), and Laras belcheri (breeds in southernmost Buenos Aires,
occurs regularly as far as Santa Cruz, and has been recorded from Yellow Island, east
of Hoste Island, Tierra del Fuego). Bartramia longicaada, which has been reported as
far south as the South Shetland Islands, can also be expected in the Fuegian region,
as can some other North American migrants, such as Aphriza virgata and Laras pipixcan.

In the section on field identification, the description and field marks of each species
are placed opposite the illustration. The passerines are not in systematic order but are
grouped according to habits and habitat. Plate 17, for example, shows “Ground-dwelling

March 1972
Vol. 84, No. 1

ORNITHOLOGICAL LITERATURE

109

Furnariidae,” Plate 18 shows “Flycatchers. Forest zone species” and “Open ground or
ground species,” Plate 19 shows “Open country birds,” Plate 20 “Forest birds,” and
Plate 21 “Finches.” This arrangement is somewhat confusing and ought to have been
checked. Ceryle torquata and Curaeus curaeus are not exactly forest birds, T achycineta
leucopyga is a tree swallow, Sicalis lebruni and Melanodera melanodera ought to have
been placed with the ground birds, and Troglodytes aedon placed with the forest birds.
Confusion of another kind exists in the plates where Turdus falklandii and Scytalopus
magellanicus (“forest birds”) are shown amid grass on the ground, true ground-dwellers
such as Sicalis lebruni and Phrygihis unicolor are on branches, and Zonotrichia capends,
a typical “brush-bird,” on the ground.

These negative remarks are insignificant in comparison with the great value of this
manual. Certainly the book will encourage the collecting of more data on the natural
history of Fuegian birds. It is to be hoped that the authors will complete this work
with a volume on the remaining parts of the region. — Claes C. Olrog.

The Coturnix Quail; Anatomy and Histology. By Theodore C. Fitzgerald. Iowa State

University Press, Ames, 1970: 10% X 7 in., xix -|- 306 pp., 157 text-figs. |7.95.

At present, books presenting detailed information on the anatomy of a bird are so
scarce and so necessary that any such book could be a major contribution. Where the
subject of such a text is a species used in genetic and physiological investigations, the
potential value is enhanced. Regrettably, this text does not achieve this potential. Dr.
Fitzgerald made a “valiant fight to finish the manuscript” despite his ill health;
that he did so is a tribute to the man and the scientist. Undoubtedly, had he lived to
shepherd the book through all of the prepublication stages, many of the errors and de-
I ficiencies which mark the text might have been corrected. However, the non-textual
portion of the work was prepared by his colleagues and, as frequently happens in such
! cases, they could not provide the expertise, knowledge, or personal attention and care
' which the author would undoubtedly have exercised, regardless of their intentions or their
competence in their own fields of interest.

The book is attractive; the format and type are exceptionally easy to read. The
absence of typographical errors is gratifying as is the intention to aid the reader by in-
! eluding large numbers of illustrations. The organization, with a few exceptions, follows a
traditional pattern. I do question the logic of a chapter sequence which runs:
“Osteology” — “Arthrology” — ’'''Angiology'’ — “Myology” (italics mine) ; Angiology seems
to fit closer to the chapter on “Splanchnology.” Also questionable is the placement of
the chapter on “Integument” as the final rather than as the first chapter.

A strong feature of the book is the detailed section on arthrology; nowhere else to
my knowledge is so much information available on the joints of birds. The promised,

I hut essentially absent, comparisons between the Coturnix, mammals, and other birds
|; used in research could have been most useful had they been included. While there is an
I extensive Bililiography there is a paucity of literature citations in the text; the resultant
absence of any significant documentation of many factual statements is disturbing
[especially in a text oriented toward researchers. The various organ systems are unevenly
1 emphasized. Extensive coverage is given to osteology, myology, angiology, and, to some
degree, neurology, hut only five pages are given over to the endocrine system, and four
I to the integument. The text also promises, by title, to cover “histology”; with compara-
[ | lively few exceptions, it does not, leaving a significant void in coverage of functionally
‘<1 important histological aspects of many organs and tissues.

110

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

While much of the information presented is accurate, there are some disturbing
and notable exceptions, some hut certainly not all of which are discussed below.

Illustrations, while numerous, are quite inadequate and thus the reader must care-
fully study the labels to compensate for deficiencies in the legends. Sometimes the
same view is labeled differently in different figures (e.g. Figs. 3.1 and 3.5), or major
structures are left unidentified (e.g. several illustrations in chapters 2-5). There are
instances where structures are discussed in detail in the text (e.g. middle cardiac vein,
p. 63) but are nowhere illustrated. Finally, there are structures illustrated which in no
way correspond to the text description (e.g. Mm. quadratus femoris, ischiofemoralis,
biceps femoris and some instances of M. gracilis) ; in other instances illustrations are
cited as supportive of text descriptions when other, uncited, illustrations depict more
clearly, if still inadequately, the described structure (e.g., M. caudofemoralis) . Many
illustrations appear to be a cross between diagrammatic representations and a faithful
reproduction without being identified as either; Figs. 3.26 and 3.27, which depict the
renal portal system, appear to be faithful reproductions, but are instead, diagrammatic.
If the reader accepts these figures as an accurate representation, he could construct a
completely inaccurate pattern of possibilities of blood flow within this system. The
renal portal valve in Figs. 3.26 and 3.27 is oriented backwards and a vein labeled
“internal iliac” in Fig. 3.25 is, in Fig. 3.27, identified as “afferent renal”; Akester (J.
Anat., 98:865-876, 1964) identifies this vein as the caudal renal portal.

The section on arthrology contains inconsistencies in identification of the “types”
of joints described; compare the classification of the humeroscapulo-coracoid, coxofemoral,
and costosternal articulations. The vertebral intercentral articulation (rightfully limited
to the cervical vertebrae) is classed as an amphiarthrosis (p. 39) despite the stated
presence of a joint capsule composed of “fibrous and synovial layers” (pp. 39-40).
Further, to refer to the action at these intercentral articulations as “hinge and gliding,”
while possibly descriptive, is to me an improper and misleading use of terms which
have a more precise and restricted arthrological applieation. Also questionable is the
statement that the nasofrontal articulation produces a “gliding movement.” Tlie generally
accepted action at this articulation is that of a “hinge” (Fisher, H. L, Wilson Bull. 67:
175-188, 1955; Bock, W. J., J. Morphol. 114:1-42, 1964).

Perhaps the most disconcerting aspect of this work arises from the nomenclature
employed by the author. The problem of anatomical nomenclature is not new and
nowhere is it more acute than in avian anatomy. Unfortunately, while birds are verte-
brates, and thus conform to a basic vertebrate body plan in which many structures are
unquestionably homologous, the question of homology is in no way firmly established
between many similar structures of birds and mammals. Birds are not mammals, they
have not evolved from mammals, and the only relationship they have to mammals is
that both had a reptile-like ancestor. They have evolved independently for more than
150 million years. To expect that the morphology of two such divergent organisms would
be amenable to an identical system of nomenclature universally denies the unique
character of birds. Yet, repeatedly the author — unintentionally, 1 am sure — does so,
and I felt that this was an anatomical treatise on that most aberrant of creatures, “The
Feathered Mammal.” In those instances where there was no possibility of equivalence
of terminology, the author, as did Chamberlain whose work (1943, Mich. State Coll.
Agr. Exp. Sta.) served as Fitzgerald’s authority for nomenelature of avian limb muscula-
ture, ignored completely the body of literature on avian morphology which has
established a de facto even if not a de jure nomenclature. The resultant effeet is one
that can only lead to utter confusion for those who unwittingly accept most of the

March 1972
Vol. 84, No. 1

ORNITHOLOGICAL LITERATURE

111

terminology in this text as authoritative and thus follow it in their publications, or who
attempt to compare information presented here with that available on other avian species.
In many cases they will find that they do not speak the same language. It is my opinion
that this text provides the strongest argument available for formulation and promulgation,
at the earliest possible time, of a Nomina Anatomica Avium. The following selected ex-
amples illustrate this viewpoint.

One may find some argument for the use of the term “stifle joint” to designate the
femori-tibiotarsal (— knee) joint of birds; one could for sake of convenience overlook
the term “Ossa faciei” (misspelled in the text as “Ossa faciei”) though the presence of
a “face” is questionable in birds. Perhaps one might accept use of the term “diaphragm”
so long as it were pointed out that this term implies something less in function and
structure than a similarly named structure in mammals. However, completely unacceptable
to me is the term “hock” to refer to the tibiotarsal-metatarsal joint in birds. While the
hock of mammals and its analogue in birds are both “inter-tarsal” joints, structurally,
here the comparison ends. Similarly, it does not seem accurate to employ terms such as
“jejeunum,” “ileum,” and especially “descending colon,” nor to use mammalian names
for vessels supplying structures of the avian intestinal tract. Disturbing also are
osteological references such as “lumbosacral bone” for the synsacrum; the author does
give “synsacrum” as a synonym but he uses the term “lumbosacral bone.” Also un-
desirable is use of the term “urostyle” for “pygostyle” even if used interchangeably as
was done in the text.

There is a wealth of literature on avian anatomy to which one can refer for “names.”
While admittedly there are two sets of myological terminologies extant, (Hudson, Amer.
Midi. Nat. 18:1-108, 1937 and Fisher, Amer. Midi. Nat. 35:545-727, 1946), most
American workers select one and include a synonymy with the other in their work. These
terminologies have been established over a long period of time as the result of the classical
works of Gadow, Fiirbringer, Garrod, Shufeldt, Forbes, and more recently, Hudson
et ah, Fisher, Berger, Bock, etc. Fitzgerald, however, chose as a basis for his muscle
names, the work of Chamberlain (op. cit.) without either researching works on avian-
mammalian homologies or investigating the question himself. Far preferable, it would
seem to me, would have been a short comment indicating familiarity with the body
of literature on avian terminologies, including citations, and a short statement of
reasons for rejecting these studies. In this manner, the reader would then have been
forewarned that major variations in nomenclature exist which require “translation” or
reference hack to the “classics.” As it stands, however, the resultant confusion to the
researcher because of the terminological differences suggests that extreme caution should
be exercised in accepting the data on the myology. A few examples of the problems
which can arise because of these terminological differences are cited below.

There are serious inconsistencies and inaccuracies in descriptions, terminology, and
illustration of a large number of the muscles in the hind limb. The muscles identified
by Fitzgerald as Mm. biceps femoris, semimembranosus, and semitendinosus are not the
I same muscles given these names in the ornithological literature. M. semitendinosus

of Fitzgerald is M. biceps femoris of Hudson, M. semimembranosus is M. semitendinosus
' of Hudson and M. gracilis of Fitzgerald is M. semimembranosus of Hudson. The muscle

I identified as M. biceps femoris by Fitzgerald is apparently the caudal portion of M.

I tensor fascia lata although Fig. 4.10 is the only place it is illustrated; in all other

, illustrations the muscle is simply referred to as M. tensor fascia lata. Ecpial confusion

' results in the identification of other muscles fe.g. M. (juadratus femoris, compare de-

' scription on p. 158 with illustration on I4g. 4.21). M. (juadratus femoris is supposedly

I

112

THE WILSON BULLETIN

March 1972
Vol. 84, No. 1

M. ischiofemoralis of Hudson but it appears more probable that it is, in reality, pars
iliofemoralis of M. piriformis. I cannot overlook the fact that Fitzgerald uses tlie name
“M. pectineus” for “M. ambiens”; this muscle has long been recognized to be without any
apparent homologue in mammals.

The digital flexor muscles of the hind limb of the bird are unique in their arrangement
and differ from those of the mammal. It is thus a gross oversimplification to simply
arrange these muscles into a group of superficial and a group of deep digital flexors.
Neither is there any justification for departing from the universally accepted nomenclature
for the five major digital flexors by introducing completely new names for them. Finally,
virtually no attention is paid to the frequently functionally important tarsometatarsal
muscles. The names given to, and the general descriptions provided for, the few such
muscles described are insufficient to he of any value at all.

Undoubtedly there is information of value in the text, but it is obvious that if other
sections are as disturbing as those reviewed in detail, a great deal of care must be used
in relying on this hook as an authoritative reference. Perhaps, in company with a broad
knowledge of the literature of avian anatomy, the text can be useful. It might serve
as a possible point of departure for the most general information on the anatomy of
the Common Coturnix; hut it is neither an accurate or a reliable compendium for use
by an investigator. The text is the only one available on the Coturnix, and for that reason
one might wish to purchase it. I suggest extreme caution in reliance upon it as an
authoritative text. — Robert D. Klemm.

A Field Guide to Australian Birds. Non-passerines. By Peter Slater and others.

Livingston Publishing Co., Wynnewood, Pennsylvania, 1970 : 5% X 7^4 in., xxxii -f-

428 pp., 43 col. and 21 hi. and wh. pis., 47 figs. $10.00.

Although the name of Peter Slater figures prominently on the first page of this book,
he is responsible only for the illustrations and for the text for one order, the Falconiformes.
The text for the remaining 18 orders has been written by seven bird experts, six of whom
are professional ornithologists employed by the Wildlife Section of the Commonwealth
Scientific and Industrial Research Organization (CSIRO).

This book, which is the first of a two part issue, is designed to help in identifying
any non-passerine bird that may occur in the Australian region. It contains a visual index
for quick identification, a so-called check list, and a section of 131 pages which includes
the plates, on which are shown every non-passerine found within the stipulated area,
together with the name and the key markings of each species. The second section of
282 pages contains the notes on each species and distribution maps, with appropriate
cross references to the illustrations in the first section. The final pages contain indexes
of common and scientific names.

This is one of the most comprehensive field guides ever to be prepared on Australian
avifauna. It incorporates most of the features that have appeared in other modern guides,
and with such a galaxy of talent the text should be nearly perfect. In general, the type-
setting and printing are good, but some letters are faint or even missing, and the black and
white illustration of the Giant Petrel on Plate 3 is badly spotted.

The colored plates are somewhat garish, possibly owing to heavy inking in the printing.
The Gang-gang Cockatoos on Plate 53 are almost as black as the black cockatoos.
Although printing on blue paper outlines the white parts of the plumages, it is not
conducive to clarity. It is stated that the “illustrations are intended to be an aid to
identification, not works of art,” and this aim has been achieved, helped by the large
size of the image of each bird depicted.

March 1972
Vol. 84, No. 1

ORNITHOLOGICAL LITERATURE

113

Some of the plates, however, can be misleading. On Plate 2, the albatross heads, while
not being drawn to scale, show variation in size. The bill of the Wandering Albatross is
almost 20 per cent larger instead of being that much smaller than that of the Royal
Albatross; the Sooty Albatross and the Light-mantled Albatross are similar to the other
species instead of being much smaller. The identification key on Figures 15 and 16
shows the opposite sizes to the plates and gives the correct comparison of these species.

The only other group that 1 checked was the genus Pachyptila, which is identified
almost solely by the size and shape of the bills. On figure 21 there are two drawings
of the bill of the Dove Prion, and although the range of width of the bill of this species
is said (p. 165) to be 11 to 14 mm., the drawings are 14 and 19 mm.

The paintings of the Cattle Egret in breeding plumage on Plates 13 to 15 show con-
siderable variation in the same plumage state. The adult Swamp Harrier, on Plate 22,
does not show the white patch on the rump, which is diagnostic; this field mark is not
even mentioned in the accompanying key although it is referred to in the text on page
250. The black and white drawing of the Malleefowl on Plate 28 is described as “upper-
parts attractively patterned,” with no mention of color. On Plate 59, the title is given
as Horsfield Brown Cuckoo, which is corrected on page 384 to Horsfield Bronze Cuckoo.

This book clearly reflects the chaotic state of the nomenclature of Australian birds, due
to the laek of an accepted check-list. From the taxonomy used, including vernaculars,
it would appear that the ornithologists within the CSIRO Wildlife Section do not accept
the “CSIRO Index of Bird Names” which was prepared by one of their members. It is
stated that the “text is arranged in systematic order, following the CSIRO Index — we have
taken the liberty of departing from the order in a few places.” The first liberty taken is
to alter the sequence of one of the orders. The order of grebes — Podicipediformes — was
placed in the Index after Proeellariiformes and Pelecaniformes. Instead of now placing
it before these two orders, to follow modern taxonomy, in the book it is plaeed between
them. Many liberties have been taken in switching the sequence in which genera and
species were placed. Even the sequence of families has been changed, and in one in-
stance a new family, Arenariidae, has been introduced.

It is at the species level, however, that most changes have taken plaee. The Oriental
Dotterel, Charadrius veredus, becomes a subspecies of Caspian Plover, C. asiaticus
veredus; the Spur-winged Plover, Vanellus novaehollandiae, is lumped with the Masked
Plover, V. miles novaehollandiae; the White-tailed Black Cockatoo, Calyptorhynchus
baadini, becomes Yellow-tailed Black Cockatoo, C. funerens baudinii; the Red-sided
Parrot, Eclectus pectoralis, is changed to Eclectus Parrot, E. roratus; the Cattle Egret,
Bubulcns ibis, becomes Ardeola ibis; the Golden Bronze Cuckoo, Chrysococcyx plogosiis,
is made a subspecies of Shining Bronze Cuekoo, C. lucidus plagosus, and there are many
other changes. Each author has acted as his own taxonomist.

The vernacular names have been altered to an even greater extent. This particularly
applies to the Psittaciformes, Falconiformes, and Proeellariiformes. No alternative names
are shown, and the only clue to other works is through the scientific names, many of
which are altered. This hook is stated to he for beginners as well as for serious
students, and it is essential that they he aide to refer to other works on birds. This
particularly applies to the current record-selling hook, “What Bird is 4 hat,” which has
been on the market since 1931, and brought up to date with each edition.

This guide could become a popular hook on Australian birds. Unfortunately, the
number of pages in the two parts, some 800-900, will make it very bulky for a field guide. —
Roy P. Cooper.

114 THE WILSON BULLETIN voL'sfN^i

Evolution of Diving Adaptations in the Stifftail Ducks. By Robert J. Raikow.

University of California Publications in Zoology, vol. 94, Berkeley, 1970: lOV-t X 6% in.,
vi + 52 pp., 32 figs., 16 tables. $2.50.

This study is mainly a functional-anatomical comparison of the tails and hind limbs
of four species of duck. Three of these — the Black-headed Duck, Ruddy Duck, and Musk
Duck — belong to the stifftail tribe, Oxyurini. The fourth species, the Mallard, is used
as a representative of the ancestral surface feeding stock from which the Oxyurini pre-
sumably evolved. These species (each representing a different genus) were selected
because of their availability and supposed approximation to an evolutionary sequence
in which increasing efficiency in underwater swimming is achieved at die expense of
terrestrial locomotion.

After an introduction and a materials and methods section, four pages are devoted
to a summary of locomotor habits. Unfortunately almost all of this information seems
to have been taken from the literature and is lacking in details and preciseness.

The next section compares the tails of the four species. Tail vertebrae counts and
measurements are given and the tail muscles are described. For both the tail skeleton and
its muscles, ratios are used for interspecific comparisons (different tail lengths are
expressed as a per cent of “trunk length” while the separate muscle weights are expressed
as a per cent of total caudal muscle weight) .

In the section on the hind limb, the approach is similar to that employed for the tail.
Relative proportions of the pelves and hind limbs are presented. Interesting differences
in the knee joints are noted. Finally the hind limb muscles are described and their
mechanical advantages and relative weights used in functional comparisons.

The data collected are employed to formulate both systematic and functional con-
clusions. The new anatomical evidence substantiates the earlier presumption that the
three stifftails represent an evolutionary sequence. At the beginning of this sequence, the
Black-headed Duck serves as a connecting link between the surface feeders and the
more advanced stifftails. Raikow summarizes the functional modifications in the sequence
as follows: “Various modifications of the osteology and myology of the hind limb and
tail have occurred which improve the efficiency of an adducted leg posture in diving, and
the use of the tail as an underwater rudder. These include lengthening of the tail and
enlargement of the caudal levator muscles, narrowing of the pelvis and elongation of the
postacetabular portion, enlargement of the area of origin of leg muscles from the knee
area, reduction of the size of thigh muscles and increase in shank muscles correlated with
the change from walking to swimming. Changes in the line of action of certain thigh
muscles improve their effectiveness as fixators of the thigh during diving. An increase
in the mechanical advantage of many muscles may be associated with the need for
strength of action rather than speed, in swimming as compared to walking.”

Raikow’s approach is traditional and follows the general philosophy and techniques
pioneered in avian anatomy by Alden Miller (1937) in his study of the Hawaiian Goose.
Recently some of these techniques have been seriously questioned. Walter Bock has
been particularily vigorous in exposing errors. For instance, muscle weights, volumes
or ratios derived therefrom are not necessarily accurate indices of the force producing
capabilities of muscles. Rather other parameters, particularly those involving fiber
length and arrangement, must be considered. Likewise, the use of mechanical advantages
to differentiate between muscles which generate force at the expense of speed versus
muscles which produce speed at the expense of force is probably incorrect. Rather,
Bock advocates the use of “free-body diagrams” (1%8). Raikow’s functional interpreta-

March 1972
Vol. 84, No. 1

ORNITHOLOGICAL LITERATURE

115

tions unfortunately place heavy reliance on both the mechanical advantages and relative
weights of muscles.

If Walter Bock’s recommendations are followed, many of the widely accepted “ground
rules” of avian functional anatomy will have to be modified. Regrettably, there is still
no study of a scope comparable to Raikow’s which attempts to incorporate the new
theoretical aspects of functional anatomy into an operational framework. Hopefully such
a study will appear in the near future.

As it stands, Raikow’s study contains a wealth of interesting information. His efforts
should be commended even if his functional conclusions must be viewed with some
skepticism. — Lowell Spring.

Portraits of Tropical Birds. By John S. Dunning. Livingston Publ. Co., Wynnewood,

Penna., 1970: 8% X 11% in., xx + 153 pp., 72 color pis., $20.00.

Beautiful color photographs of 72 species of the most striking neotropical birds dominate
this book. The photographer-author has commented on each species and family in a
single short paragraph, usually to identify the habitat and something of the bird’s be-
havior. It is a handsome book and will stimulate enthusiasm for tropical birds in most
readers.

Dunning describes how he captured wild birds in nets and even includes plans for
constructing the portable enclosure in which he photographed them in the field with
electronic flash. The enclosure is supplied with vegetation and perches appropriate to
the bird’s habitat, the bird is introduced to the cage, photographed in what appears to
be a natural setting, and then released. One-third of the plates are of tanagers, and an
eighth are of antbirds; the remaining plates illustrate representatives of 21 other families.
Even the colors of unfeathered areas are sometimes striking; e.g., eleven species have
vivid red eyes! — Stephen M. Russell.

The Pine Barrens. A Preliminary Ecological Inventory. By Jack McCormick.
Research Report No. 2, New Jersey State Museum, Trenton, New Jersey, 1970: 6 x9
in., 103 pp., 9 maps, one table, 23 halftones. $2.75.

The New Jersey Pine Barrens constitute the most extensive (approximately 2000 scjuare
miles) wildland tract on the Atlantic seaboard. Although close to the densely populated
metropolitan areas of Philadelphia and Camden, it is sparsely settled and has no major
industries. Due to its infertile and droughty soil, it is, with the exception of its blueberry
and cranberry culture, unattractive to agriculture. Mostly forested, it is interlaced with
slow meandering streams and spotted with bogs. Its geological history is complex, but
its most interesting feature is its flora, which has, in addition to common plants, a con-
I siderable number of rare ones. Tire Barrens are the northern limit of many southern

species and the southern limit of some northern ones. Twenty-four species of plants,

j including two found only here, have been originally described from the Pine Barrens.

Bird life here is relatively poor compared with other areas in the state.

The New Jersey Audubon Society, the Pine Barrens Conservationists, and other citizens'
I groups became concerned about threats to the preser\ation of the Pine Barrens. They
! enlisted the cooperation of the National Park Service in an endeavor to have the Barrens

I designated a National Landmark, thereby putting a brake on tlie threats of real estate

I developments, possible expansion of the blueberry and cranberry growing, and tin*

I establishment of a jet airport which would gobble up 51 s(iuarc miles at one fell swoop.

I

116

THE WILSOxX BULLETIN

March 1972
Vol. 84, No. 1

The National Park Senice made a grant to the Academy of Natural Sciences of Phila-
delphia for a study of the natural resources of the area. Jack McCormick of the Academy
staff made the survey, and his report, entitled “A Study of the Significance of the Pine
Barrens of New Jersey” was issued in January, 1%8. The present publication is a
summary of that report.

It concisely summarizes the past industrial background of the region, and lists its
plants and animals. Two areas in the region which have varied habitats are studied
in considerable detail. The value of the area, not only for the preservation of its native
wildlife, open space conservation, recreation, hunting and fishing, and water supply,
but also as a scientific laboratory for the study of its unique ecosystem is stressed.
The Pine Barrens have generated much scientific debate, and this work points out that
there is much yet to be learned. It is refreshing to have the challenges to our under-
standing so well delineated. An excellent bibliography will help all who wish to learn
more about this fascinating region. — Ernest A, Choate.

PUBLICATION NOTES AND NOTICES

Check-list of Birds of the World, Volume XIII. By Raymond A. Paynter, Jr. and
Robert W. Storer. Museum of Comparative Zoology, Harvard University. Cambridge.
Mass., 1970: 6^2 X 9% in., xiv -(- 443 pp. S15.00.

This volume treats the buntings and American sparrows. Plush-capped Finch, cardinal-
grosbeaks, tanagers, and the Swallow-Tanager, all united under the family Emberizidae.
These birds have been separated from the carduelines and Fringilla by the wood warblers.
Hawaiian honeycreepers, vireos, and icterids (already treated in Check-list, Vol. 14). Of
the fifteen volumes in this indispensable series, volumes 8 and 11 remain to be pub-
lished.—P. S.

This issue of The W ilson Bulletin was published on 29 March 1972

Editor of The Wilson Bulletin
GEORGE A. HALL
Department of Chemistry
West Virginia University
Morgantown, West Virginia 26506

Editorial Advisory Board

William C. Dilger
Douglas A. James
William A. Lunk
Andrew J. Meyerriecks

Helmut C. Mueller
Robert W. Nero
Kenneth C. Parkes
Glen E. Woolfenden

Ornithological Literature Editor
Peter Stettenheim

Box 79, Plainfield, New Hampshire 03781

Suggestions to Authors

Manuscripts intended for publication in The Wilson Bulletin should be neatly type-
written, double-spaced, with at least one inch margins, and on one side only of good quality
white paper. Tables should be typed on separate sheets, and should be designed to fit
the normal page width, i.e., narrow and deep rather than wide and shallow. Before pre-
paring these, carefully consider whether the material is best presented in tabular form.
Follow the AOU Check-list (Fifth Edition, 1957) insofar as scientific names of United
States and Canadian birds are concerned unless a satisfactory explanation is offered for
doing otherwise. Use species names (binomials) unless specimens have actually been
I handled and subsequently identified. Summaries of major papers should be brief but
I quotable. Where fewer than five papers are cited, the citations may be included in the text.
’ All citations in “General Notes” should be included in the text. Follow carefully the style
used in this issue in listing the literature cited; otherwise, follow the “Style Manual
for Biological Journals” (1964. AIBS). Photographs for illustrations should be sharp,
have good contrast, and be on gloss paper. Submit prints unmounted and attach to
each a brief but adequate legend. Do not write heavily on the backs of photographs.
Diagrams and line drawings should be in black ink and their lettering large enough to
permit reduction. Authors are requested to return proof promptly. Extensive alterations
in copy after the type has been set must be charged to the author.

Notice of Change of Address

If your address changes, notify the Society immediately. Send your complete new
address to the Treasurer, William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.
He will notify the printer.

The permanent mailing address of the Wilson Ornithological Society is: c/o The
MUSEUM of Zoology, The University of Michigan, Ann Arbor, Michigan 48104. Persons
having business with any of the officers may address them at their various addresses
given on the back of the front cover, and all matters pertaining to the Bulletin should be
sent directly to the Editor.

PLAN TO ATTEND THE 1972 ANNUAL MEETING

The 1972 meeting of the Wilson Ornithological Society will be at Cape May,
New Jersey from Thursday, 15 June to Sunday, 18 June 1972. The meeting
is being sponsored jointly by the Academy of Natural Sciences of Philadelphia,
the Delaware Valley Ornithological Club, the New Jersey Audubon Society
and the Urner Ornithological Club of New Jersey. The chairman of the local
committee for arrangements is Dr. Ernest A. Choate, Cape May Point, New
Jersey 08212. Information concerning accommodations, transportation, and a
call for papers will be sent to all members with advance registration forms.
Cape May, being a summer resort, has a large number and variety of res-
taurants and lodging accommodations. Headquarters will be at the Colonial
Hotel and Motor Lodge, Central Beach Front, Cape May.

The Cape May region has been a center of ornithological interest since the
time of Alexander Wilson and John James Audubon. The list of birds recorded
here began with them and is still growing. The last new bird was a Skua
sighted about five miles off shore on 16 June 1969 bringing Cape May’s cumu-
lative list up to 354. A special feature of the area is the Stone Harbor Heronry,
one of the largest breeding colonies in the United States of Common, Snowy,
and Cattle Egrets, Louisiana, Little Blue, Black-crowned Night, and Yellow-
crowned Night Herons as well as thousands of Glossy Ibis. The largest breed-
ing colony of Laughing Gulls on the continent is on a nearby salt marsh.
Close by on the sand flats breed Black Skimmers, Common and Least Terns
interspersed with an occasional Gull-billed Tern. Off shore the sight of a
Sooty Shearwater, Cory’s Shearwater, Wilson’s Petrel, or a jaeger is a possi-
bility. A walk in the woods may turn up a Black and White Warbler, Redstart,
Kentucky, Prothonotory, or Hooded Warbler. Near the Cape May Point
Lighthouse the notes of the Chuck-wills-widow and the Whip-poor-will are
occasionally accompanied by the call of a rail and the hoot of the Great
Horned Owl.

TfieWlsonBulletin

PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY
WEST VIRGINIA U. • MORGANTOWN, W. VA.

VOL. 84, NO. 2 JUNE 1972 PAGES 117-228

MUS. COMP. ZOCL-

t O

The Wilson Ornithological Society
Founded December 3, 1888

Named after ALEXANDER WILSON, the first American Ornithologist.

President — Pershing B. Hofslund, Dept, of Biology, University of Minnesota Duluth,
Duluth, Minnesota 55812.

First Vice-President — Kenneth C. Parkes, Carnegie Museum, Pittsburgh, Pennsylvania
15213.

Second Vice-President — Andrew J. Berger, Dept, of Zoology, University of Hawaii,
Honolulu, Hawaii 96822.

Secretary — James Tate, Jr., Laboratory of Ornithology, Cornell University, Ithaca, New
York 14850.

Treasurer — William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.

Elected Council Members — Ernest P. Edwards (term expires 1972) ; Elden W. Martin
(term expires 1973); Robert D. Burns (term expires 1974).

Membership dues per calendar year are: Active, $8.00; Sustaining, $15.00;

Life memberships, $200 (payable in four installments).

The Wilson Bulletin is sent to all members not in arrears for dues.

The Josselyn Van Tyne Memorial Library
The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed
in the University of Michigan Museum of Zoology, was established in concurrence with
the University of Michigan in 1930. Until 1947 the Library was maintained entirely
by gifts and bequests of books, reprints, and ornithological magazines from members
and friends of the Society. Now two members have generously established a fund for
the purchase of new books; members and friends are invited to maintain the fund by
regular contribution, thus making available to all Society members the more important
new books on ornithology and related subjects. The fund will be administered by the
Library Committee, which will be happy to receive suggestions on the choice of new books
to be added to the Library. William A. Lunk, University Museums, University of Michi-
gan, is Chairman of the Committee. The Library currently receives 104 periodicals as gifts
and in exchange for The Wilson Bulletin. With the usual exception of rare books, any
item in the Library may be borrowed by members of the Society and will be sent prepaid
(by the University of Michigan) to any address in the United States, its possessions, or
Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers,
as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to
“The Josselyn Va.> Tyne Memorial Library, University of Michigan Museum of Zoology,
Ann Arbor, Michigan.” Contributions to the New Book Fund should be sent to the
Treasurer (small sums in stamps are acceptable). A complete index of the Library’s
holdings was printed in the September 1952 issue of The Wilson Bulletin and newly
acquired books are listed periodically.

The Wilson Bulletin

The official organ of the Wilson Ornithological Society, published quarterly, in March, June, September,
and December, at Morgantown, West Virginia. The subscription price, both in the United States and elsewhere,
is $10.00 per year. Single copies, $2.50. Subscriptions, changes of address and claims for undelivered
copies should be sent to the Treasurer. Most back issues of the Bulletin are available (at $2.50
each) and may be ordered from the Treasurer. Special prices will be quoted for quantity orders.

All articles and communications for publications, books and publications for reviews should be addressed to
the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology,
Ann Arbor, Michigan.

Second class postage at Lawrence, Kansas, U.S.A. 66044

Allen Press, Inc., Lawrence, Kansas 66044

THE WILSON BULLETIN

A QUARTERLY MAGAZINE OF ORNITHOLOGY

Published by The Wilson Ornithological Society

VoL. 84, No. 2

June 1972

Pages 117-228

CONTENTS

Studies of the Brown Pelican

Ralph W . Schreiber and Robert W. Risebrough 119

Behavioral Responses of Migrating Birds to Daylight and Dark-
ness: A Radar and Direct Visual Study

Sidney A. Gauthreaux, Jr. 136

Orientation Behavior of Night-migrating Birds ( European Robins)
DURING Late Afternoon and Early Morning Hours

Wolfgang Wiltschko and Hiltrud Hock 149

Diurnal and Seasonal Activities of a Post-breeding Population

OF Gulls in Southeastern Ontario F. Cooke and R. K. Ross 164

Variations in Songs of Vesper Sparrows in Oregon

Donald E. Kroodsma 173

Factors Influencing Pellet Egestion and Gastric pH in the Barn

Owl Charles R. Smith and Milo E. Richmond 179

Analysis of Measurements, Weights, and Composition of Common

AND Roseate Tern Eggs Charles T. Collins and Mary LeCroy 187

The Role of Avian Rictal Bristles Roger J. Lederer 193

General Notes

PROBABLE bulwer’s PETREL OFF KEY WEST, FLORIDA Joseph W . Tuylor 198

SPRING MIGRATION OF THE GANNET IN f’LORIDA WATERS Terry C. Moxwe/l 198

AERIAL FEEDING IN THE SNOWY EGRET - - Jomes A. Kushlon 199

OBSERVATIONS ON THE STATUS, ECOLOGY, AND BEHAVIOR OF SORAS WINTERING

IN TRINIDAD, WEST INDIES - Michael Gochjeld 200

YOUNG COMMON AND ROSEATE TERNS LEARNING TO FISH Mary LeCroy 201

LEK BEHAVIOR IN THE BROAD-TAILED HUMMINGBIRD David P. liarash 202

EVIDENCE OF TWO TREE SWALLOW FEMALES SHARING THE SAME NEST BOX

Han ey Farber 201

STELLER’s jays FREY ON GRAY-HEADED JUNCOS AND A PYGMY NUTHATCH DURING
PERIODS OF HEAVY SNOW

Steven W . Carothers, N. Joseph Sharber, and Russell P. Baida 204
ADULT CAROLINA CHICKADEE CARRIES YOUNG

John W. Goertz and Kim Rather jord 205

HABITAT DIFFERENCES OF SWAINSON’s AND HERMIT THRUSHES

Douglass H. Morse 206

BREEDING STATUS OF THE PURPLE GALI.INULE, BROWN CREEPER, AND SWAINSON’s

WARBLER IN ILLINOIS William G. George 208

Ornithological News 211

Hawaiian Birds 1972, A Conservation Committee Report

Andrew J . Berger 212

Ornithological Literature 223

Canadian Wildlife Service, Studies of Bird Hazards to Aircraft, reviewed by
Richard R. Graber; Peter L. Ames, The Morphology of the Syrinx in Passerine
Birds, reviewed by Mildred Miskimen; Douglas L. Gilbert, Natural Resources
and Public Relations, reviewed by Keith A. Arnold; Clive Roots, Soft-billed
Birds, reviewed by William G. Conway; Kees Vermeer, Breeding Biology of
California and Ring-billed Gulls: A Study of Ecological Adaptation to the
Inland Habitat, reviewed by James P. Ludwig; Niko Tinbergen and Hugh
Falkus, Signals for Survival, reviewed by Sally Laughlin.

Publication Notes and Notices

172, 178, 197

STUDIES OF THE BROWN PELICAN

Ralph W. Schreiber and Robert W. Risebrough

I. STATUS OF BROWN PELICAN POPULATIONS IN THE
UNITED STATES.

The American Ornithologists’ Union Check-list of North American Birds
(1957: 29) records the following distribution for Pelecanus occidentalism
the Brown Pelican:

“From southern British Columbia south along the Paeific coast to Chiloe Island,
southern Chile, casually to Tierra del Fuego, including the Pearl Islands, in the
Gulf of Panama, and the Galapagos Islands, and from North Carolina and the
Gulf coast of the United States southward through the West Indies including the
Netherlands West Indies, to British Guiana, casually to extreme northern Brasil.”

Since the mid-1950’s the Brown Pelican population has declined in much of
its northern range. In Louisiana no pelicans bred between 1961 and 1970;
in 1971 several semi-captive birds introduced from Florida to Grand Terre
Island, Louisiana nested there successfully (Evenden, 1968, 1969; Joanen
and Neal, 1971 ) . In Texas the breeding population is reduced to a few pairs
(H. Hildebrand, in litt. ) ; in California and northwestern Baja California.
Mexico, a sizable population persists but breeding has been largely un-
successful since 1968 (Schreiber and DeLong, 1969; Jehl, 1969; Cress, 1970;
Risebrough, Sibley, and Kirven, 1971 ) .

This paper briefly discusses the past and present status of the Brown
Pelican in the United States. It must be emphasized that there are few data
concerning the status of the species throughout the country at any time in
this century. Documentation of population declines is therefore difficult.
The available information, however, provides a useful background for inter-
pretation of the present status of the species and for formulation of a con-
servation policy.

There is now considerable evidence linking reproductive failures of fish-
eating birds to chemical pollutants in the environment. As yet no monitoring
programs have been devised to measure the rates of accumulation of the
known persistent pollutants in coastal waters, or to determine whether stead\
state concentrations have been established, with iri|)ut from all sources
balanced by degradation and deposition in sediments, (hinlinued accumula-
tion would clearly pose a threat to the remaining pojiulations of Brown Peli-
cans; moreover, the long term effects of current levels of |)olhition are un-
known.

120

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

NORTH CAROLINA

In North Carolina the first nesting record of Brown Pelicans was in 1929,
when Birsch found 14 pairs breeding on Royal Shoal ( Wray and Davis, 1959 ) .
Wind and tide destroyed the shoal the next year and North Carolina nesting
was not reported again until 1947 when Wolff found 30 nests and 33 young
on Shell Castle Island, Ocracoke Inlet (Wray and Davis, op. cit. ) . This is
the northernmost breeding record for the Brown Pelican on the East coast.
The maximum number of young recorded at Shell Castle Island was in 1959,
when H. T. Davis banded 116 nestlings. Between 1960 and 1967 the number
of young banded fluctuated between 11 in 1966 and 100 in 1965 (Davis,
pers. comm.). No detailed observations were made in 1968 and 1969, but
R. H. Steiner visited the island in July 1970 and counted 31 nestlings and 9
nests with eggs (Steiner, in litt. ) . No young remained on the island on 19
August and fewer than 30 young may have fledged in 1970 (Steiner, in litt.).

SOUTH CAROLINA

In South Carolina, there are few data and those available are in need of
close scrutiny. Apparently, three colonies have existed in recent years. In
the 1940’s, a small colony was present on Egg Bank, Beaufort County (Mason,
1945 ) ; the other colonies are in the Cape Remain National Wildlife Refuge
and on Deveaux Bank south of Charleston.

At the Cape Remain National Wildlife Refuge information on Brown Peli-
cans has varied with the assigned priorities and individual interests of refuge
managers. The available data are therefore not sufficient to determine popula-
tion trends. Mr. Travis McDanial, Refuge Manager at Cape Remain NWR
from 1968 through 1970, has kindly provided us with the following informa-
tion: since the establishment of the refuge in 1932 the pelican colony has
been on at least five different islands, including Bird Bank, Bulls Bay, noted
as an egg collection site in Anderson and Hickey ( 1970: 26 ) . Exact numbers
are not available, but distinct yearly fluctuations in productivity are indicated.
In 1949 to 1953, 500 to 900 young fledged each year. In 1954-56 only 250 to
500 young fledged per year. In 1957-60 the breeding population increased
and from 1,200 to 1,500 young fledged each year. The estimated population
remained stable in 1961 but productivity was higher and 1,800 young fledged.
In 1962 the population declined and only 500 young fledged that year and in
1963. In 1964, 800 young fledged; production reached its highest level on
record in 1965 when 2,000 young fledged. Approximately 500 young fledged
in 1966 and 1967.

Accurate records are available for 1968-70. McDanial estimated that 500
young fledged in 1968. In April 1969 he counted 1,016 nests. After periodic
visits to the colony through the summer he estimated that 900 young fledged.

Schreiber and
Risebrough

BROWN PELICAN STUDIES

121

In May 1970, McDanial counted 627 nests and estimated that 500 to 600 young
fledged (McDanial, pers. comm.). Although total production was lower in
1970 than in 1969, it is essentially the same as that reported for 1962-1964
and 1966-1968. Since historical population fluctuations are apparent at Cape
Remain, it would seem worthwhile documenting future population trends in
detail.

On the Deveaux Bank, T. A. Beckett III believes that the breeding popula-
tion has undergone an apparent 90 per cent decline in the last decade. Beckett
(1966: 94) reported 5,000 breeding pairs in unspecified “former years”
and in the early 1960’s 7,000 to 10,000 young fledged per year (1966: 99).
In 1964 Beckett (op. cit.) noted high nestling mortality and in 1965 estimated
only 600 breeding pairs. In 1970 Beckett counted 485 nests (in litt.). The
reasons for the decline are not documented but Beckett notes (pers. comm.)
that almost three-fourths of the Deveaux Bank has washed away in the last
10 years.

GEORGIA

Although in 1898 T. D. Perry collected pelican eggs “on beach” in Chatham
Co., Georgia, Burleigh (1958) states that Brown Pelicans are not known to
have nested in the state. Explanation of this apparent discrepancy at this
time is impossible.

GULF STATES

In 1918 T. Gilbert Pearson (1918) estimated the adult pelican population
between Corpus Christi, Texas and Key West, Florida as 65,000 birds. This
same region in 1971 has fewer than 5,500 nests and probably not more than
12,000 birds (Hildebrand, in litt.; Joanen and Neal, 1971; Fogarty, in litt.).

In Alabama, Imhoff (1962 ) noted that Brown Pelicans possibly bred prior
to 1900 but none have done so there since. He listed the species as “abundant
throughout the year” but notes that in 1956-57 the local non-breeding popula-
tion declined sharply. No recovery has occurred to date (Imhoff, pers. comm.) .

LOUISIANA

The state bird of Louisiana is the Brown Pelican, yet no wild birds have
bred there since 1961. Bailey and Wright (1981) indicate that thousands
of birds nested on the mud lump islands at the mouth of the Mississippi River
and in 1918 Bailey (in Bailey and Wright, op. cit.) estimated 1.200 pairs nest-
ing on Grand Gosier Island. Oherholser (1988) listed Brown Pelicans as an
abundant permanent resident in Louisiana, and during a surve\ of the coast
in June 1988 estimated at least 5,500 nests with young and a j)oj)idati()n of at
least 1 1,000 adults. He found no breeding on Grand (iosier Island in 1088

122

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

(p. 35). Mclhenny (1943) did not mention Brown Pelicans in a paper on
major changes in the bird life of southern Louisiana. Lowery (1960) makes
no mention of a decrease in numbers of pelicans in the state and notes that
he “once” found approximately 5,000 adults with eggs and young on East
Timbalier Island (p. 113), where Oberholser found none in 1933. These
shifts of breeding locations exemplify the problems encountered in document-
ing an historical account of pelican nesting populations.

Brown Pelicans were not mentioned in the nesting season reports from the
Central Southern Region of Audubon Field Notes between 1950 and 1955.
However, in 1956 several observers noted large numbers of dead adults
washed up on beaches and Imhoff believed a severe mid- June storm may have
caused high mortality among young birds in the large colony on North Island
of the Chandeleurs (Newman, 1956). On 27 June 1957, Hurricane Audrey
had disastrous effects on many nesting species of birds in Louisiana, but no
mention was made of Brown Pelicans (Newman, 1957). In 1957-1958
wintering Brown Pelicans were “alarmingly” scarce along the entire northern
Gulf, and were entirely absent in many areas (Newman, 1958a). On 7 July
1958 “thousands” of adults and young of all ages were present on North
Island ( Newman, 19585 ) . Again, few birds were seen during the fall and
winter, and the first speculation as to what happened to the species appeared
in Audubon Field Notes ( Newman, 1959a, 19595). Between 1956 and 1960
the total coastal Christmas Bird Count estimates of Brown Pelicans decreased
from 995 to 366, to 11, to 14, to four individuals. On North Island in 1960
only about 200 pairs were reported nesting ( Imhoff, 1960) . On 21 June 1961,
van Tets (1965; in litt. ) observed ca. 200 pairs and 100 chicks with white
down and developing primaries on North Island. In June 1962 no nests were
present on the island and during a survey of the area only six adults were
observed (Stewart, 1962).

A propagation program was begun in the state in 1968 and over 170 nest-
lings were imported from Florida during 1968, 1969, and 1970. In March
1971 some of the 1968 imports nested on a shell island in Barataria Bay
near Grand Terre (Joanen and Neal, 1971)- Few wild pelicans occur else-
where in Louisiana or the northern Gulf region.

TEXAS

In Texas fewer than ten pairs of Brown Pelicans nested in 1969 or 1970
(Hildebrand, in litt.). Pearson (1921) estimated the total Texas Brown
Pelican population at approximately 5,000 birds. Little information is
available about the dramatic decline in nesting, but reports in Audubon Field
Notes for the South Texas Region between 1950 and 1963 reveal some interest-
ing observations. “Brown Pelicans that had a somewhat-below-normal nest-

Schreiber and
Risebrough

BROWN PELICAN STUDIES

123

ing season last year had a repeat this year with hundreds of adults having
been killed by the freeze” of 29 January-3 February, 1951 (Goldman, 1951).
In 1952 “Brown Pelicans which decreased in numbers at the time of the
freeze early in 1951, had a much improved season this year” ( Goldman and
Watson, 1952). Between 1953 and 1959 pelicans are not mentioned, but in
1960 pelicans “made a comeback at Galveston” (Webster, 1960). This last
comment apparently refers to the effects of Hurricane Audrey in June 1957, or
to other unidentified factors. For 1961 and 1962 no mention appears of
Brown Pelicans, but in 1963 only 18 young were produced in Texas ( Webster,
1963).

In 1967 four pairs are known to have produced four young in Corpus Christi
Bay and Hildebrand believes a few pairs bred in Texas each year from 1964-
1966 as well (Hildebrand, in litt. ) . In 1968, four young fledged from two
nests on Carroll Island in the Second-chain of Islands. In 1969 the only
observed nesting was reported on an unnamed spoil island on Long Reef in
Aransas Bay, five nests produced seven young ( Hildebrand, in litt. ) .

In 1970 Emily Payne recorded observations on the few remaining pelicans
in Texas and Hildebrand supplied the following information ( in litt. ) : one or
two birds overwintered along the coast and numbers increased in March to a
peak in mid-June of 105 Brown Pelicans concentrating in Corpus Christi
Bay. Only eight “subadults” were seen. Three pairs and at least ten eggs
were noted on Carroll Island but the birds abandoned the site between 3 April
and the end of the month. The cause of the desertion was apparently not human
molestation. Several pairs nested in May on “Pelican Island” in Corpus
Christi Bay (the same island used in 1969) and in early July four nests con-
tained 9 healthy young.

The status of the Brown Pelican in eastern Mexico, the Caribbean, or
Central America, past or present, is essentially unrecorded. Pelicans are re-
ported to have nested and apparently still nest in scattered colonies in the
Mexican states of Veracruz, Yucatan, and Quintana Roo; nesting also occurs
in Panama, British Honduras, Colombia, Venezuela, Trinidad, Tobago, the
Lesser and Greater Antilles, and the Bahamas ( A.O.U., 1957; Murphy, 1936:
Wetmore, 1945, 1965; Hildebrand, pers. comm.). Probably none of the
colonies contain more than a few hundred pairs. The precise locations of
most colonies is unknown and the ranges of the subspecies are uncertain
I Palmer, 1962; Voous, 1957). The need for more information on the Brown
Pelicans in these areas is obvious.

CALIKOUMA

Historic breeding records for Brown Pelicans in (’alifornia were summarized
by Schreiber and DeEong ( 1969) who noted that no nesting occurred in the

124

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

State in 1968, except on Anacapa Island, where sites active in early April had
heen abandoned by mid-May. In the early 1900’s, colonies of up to a few
hundred pairs existed in at least five locations and several thousand pairs
were present on Los Coronados, Baja California, Mexico, and on Anacapa
Island. In 1958, large numbers were still present on Los Coronados. On
Anacapa in 1964 perhaps 1,000 pairs bred successfully. In 1969 Anacapa was
visited by Risebrough et al. (1971) who summarized the nesting attempts
for the summer and noted that a minimum of 1,272 nests were built, more
than 75 per cent received eggs, and no more than four young fledged. Cress
(1970) working on Anacapa Island in 1970 found from over 500 nests con-
structed, only one young fledged. Schreiber and Cress (unpubl. observ.) noted
aberrant nesting behavior in the Anacapa pelicans in 1970 and Risebrough
et al. (in prep.) present data on shell thickness and chemical residue anal-
yses.

The status of the Brown Pelican in the Gulf of California of western Mexico
is poorly understood but the Section of Pesticide-Wildlife Ecology, Bureau of
Sport Fisheries and Wildlife, Denver, Colorado is presently carrying on ex-
tensive investigations of the biology of the pelicans in the Gulf. Information
on the pelicans in Peru is available but is beyond the scope of this discussion.

FLORIDA

In Florida the available historical information on the Brown Pelican
status was summarized by Howell ( 1932 ) . Little accurate information on
the total population is available, but the species has been abundant in the
state since the first bird observations were recorded. Williams and Martin
(1968; 1970) present data based on aerial surveys and visits to colonies in
1968, 1969, and 1970 indicating that the Florida breeding population has
remained essentially stable with 6,705, 6,133, and 7,690 nests counted in those
years respectively. The conclusion by Blus ( 1970 ) that the Florida east
coast population was declining based on data supplied in 1969 by Williams
(pers. comm, to Blus) appears to have been premature in light of the 1970
survey by Williams and Martin ( 1970 ) .

II. STUDIES OF THE BROWN PELICAN IN FLORIDA.

In summarizing the available information on the natural history of Brown
Pelicans, Palmer (1962 ) indicates the dearth of knowledge about their biology.
One of us (R.W.S. ) began a detailed study of Brown Pelicans in Florida in
January 1969 with efforts being concentrated in the largest colony in the state,
on Tarpon Key in Boca Ciega Bay, St. Petersburg, at the mouth of Tampa
Bay.

The pelicans nest on Tarpon Key from two to 25 feet above the high tide

Schreiber and
Risebrough

BROWN PELICAN STUDIES

125

Brown Pelican

Hatching

Table 1

Success, Tarpon Key, Boca
Florida, 1969 and 1970

CiEGA Bay,

St. Petersburg,

1969

1970

Nests

Nests

Nests

Nests

checked

checked more

checked

checked more

weekly

frequently

weekly

frequently

No. Nests Observed

13

63

25

37

Eggs Laid

37

142

64

77

Eggs/Nest

2.85

2.25

2.56

2.08

Eggs Hatched

no.

31

80

45

22

%

84

56

70

29

Eggs Destroyed

no.

3

45

8

50

%

8

32

13

65

Eggs Addled

no.

3

17

10

2

%

8

12

16

3

Eggs Crushed

no.

0

0

1

3

%

2

4

line in black mangrove {Avicennia nitida) primarily surrounding the central
lagoon of the key. The colony is subdivided into distinct areas relatively
isolated from each other and one “subcolony” could be surveyed without dis-
turbing others. In 1969 13 nests were checked weekly and 63 nests were
checked more frequently, as often as thrice weekly in March, April, and May.

In 1970, over 100 nests were selected for study. However, while Schreiber
was on Anacapa Island in California during the last week of April, the colony
was disturbed at least once. We are unable to explain otherwise the egg loss
from certain areas of the colony and thus have limited analysis to 25 nests
checked weekly and 37 nests checked more frequently from 19 March till
mid-August. Nest building and laying began in early March and continued
through mid-May in both years and nest checks began when the first nest was
found. Most nests were found and marked before egg deposition began and
were checked periodically thereafter.

CLUTCH SIZE

In 1969 the 13 nests checked only weekly contained slightly larger clutches
than the 63 more frequently checked nests; in 1970, the same pattern emerged
(Table 1). The lowered clutch size in the nests which were more frecpienth
checked may reflect reduced laying by disturbed birds. On 30 April 1969
Schreiber surveyed 250 nests which had never been disturbed and counted
728 eggs and/or small nestlings, or 2.91 eggs per nest. A similar sur\e\
of 193 nests on 6 May 1970 showed 537 eggs and/or small nestlings, or 2. <•)

126

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

e^gs per nest. Three eggs per clutch was the maximum found. Bent (1922:
297 ) states that three or often two eggs constitute a full clutch of the Brown
Pelican. He also found four or five eggs in a set but believed these were from
two different females. Anderson and Hickey (1970) analyzed 236 sets in
oological collections and found the mean clutch size was 2.95 eggs.

HATCHING SUCCESS

Hatching success in both years was higher in nests checked less frequently
(Table 1). Total hatching success was lower in 1970 than in 1969 (Table 1).
In nests checked weekly, 84 and 70 per cent of the eggs laid hatched in 1969
and 1970 respectively. In nests checked more frequently, 56 and 29 per cent
of the eggs laid hatched in 1969 and 1970 respectively.

Causes for failure to hatch were assigned to three categories: 1) “addled” —
eggs remaining in nests after other eggs of the clutch had hatched. These
either were infertile or contained a dead embryo. In 1969, 20 of 179 eggs laid
(11 per cent) were addled; in 1970, 12 of 141 eggs laid (9 per cent) were
found addled. 2 ) “destroyed” — eggs noted as laid but missing on subsequent
nest checks. Some of these eggs were found broken below nests; others just
disappeared between visits. In both years the more frequently disturbed
nests suffered distinctly higher egg loss and many more eggs were destroyed
in 1970 than in 1969 (Table 1). 3 ) “crushed”— eggs obviously thin shelled
and crushed in the nest. In 1969, no crushed eggs were found among the 179
eggs laid in marked nests. During 1970, 4 (3 per cent) of 141 eggs laid in
marked nests were crushed.

In both 1969 and 1970 the two major known causes of “destroyed” eggs
were egg breakage by flushing adult pelicans and egg breakage by predators.
Pelicans incubate with their totipalmate feet surrounding the clutch. When
its flight distance is “trespassed” by a human intruder an incubating adult
will flush and the force exerted to become airborne is often sufficient to
break the egg shell. To avoid this cause of egg destruction, nesting pelicans
must be approached slowly and in full view so they can step off the eggs before
flying.

Eish Crow (Corvus ossifragiis) predation was the most serious known cause
of egg loss. When undisturbed, one partner of a pair of pelicans remains on
the nest throughout incubation, and crows do not molest the nest. However,
when disturbed, pelicans leave their nests and either circle overhead or land
on the water nearby. During March, April, and May, as many as 50 Eish
Crows spend the daylight hours on Tarpon Key. Frequently within seconds
after pelicans were disturbed, crows would land on nests, peck holes in the
eggs, and eat the contents.

Because of the high level of mortality in pelican colonies accompanying

Schrciber and
Risebrough

BROWN PELICAN STUDIES

127

Table 2

Brown Pelican Eggshell Thickness from Florida in 1969 and 1970

Mean thickness ± 95%

confidence limit Per cent

Colony

Date

No.

range

change*

Tarpon Key
Boca Ciega Bay

St. Petersburg

1969

14

0.506 ± 0.022
(0.55-0.42)

9

Hemp Key

1970

21

0.509 ± 0.024
(0.58-0.39)

9

Charlotte Harbor
Hall Island

1970

20

0.518 ± 0.024
(0.61-0.43)

7

Cocoa Beach
Rio Del Mar

1970

22

0.501 ± 0.013
(0.56-0.46)

10

Vero Beach

1970

10

0.502 ± 0.018
(0.53-0.46)

10

All Florida

87

0.508 ± 0.009
(0.61-0.39)

9

* Pre-1943 Florida eggs:

0.557 ± 0.004

mm, n =

172 (Anderson and Hickey,

1970).

human visitation from accidental breakage of eggs, predation on eggs and
young by other birds, temperature stress on eggs and naked nestlings ( Bar-
tholomew and Dawson, 1954; Schreiber, unpubl. observ.), and possible dis-
ruption of adult nesting behavior, we strongly recommend that human visits
to pelican colonies be curtailed.

EGGSHELL THICKNESS AND CHEMICAL RESIDUE ANALYSES

In 1969 and 1970, R. W. S. collected eggs from four colonies in Florida for
chlorinated hydrocarbon residue analyses. From Tarpon Key in 1969, 17
eggs were collected: one egg each from 11 three-egg clutches in April and
May, one three-egg clutch on 15 April, and one three-egg clutch on 31 May.
In 1970, 20 eggs from this colony were collected: one egg each from 20 three-
egg clutehes, two on 30 March, 16 on 5 April, and 2 on 19 April. Fifty-three
eggs were collected from other colonies in 1970: ten from the Rio Mar Island
colony in Vero Beach on 27 March; twenty from Hemp Key, Charlotte Harbor
on 16 April; and two from the Fort Pierce colony and lo from the ("ocoa
Beach Colony on 21 April. All these eggs were one of three in a clutch and
almost all were fresh or in early stages of incubation.

To prevent contamination, eggs were wrapped with aluminum foil in the

128

THE WILSON BULLETIN

June 1972
Vol. 81, No. 2

Fig, 1. Relationship between concentration of DDE and PCB in eggs of Florida
Brown Pelicans obtained in 1969 and 1970 (r = 0.701, p < 0.01).

field and frozen within six hours after collection. Eggs remained frozen
during air shipment to the Laboratory of the Institute of Marine Resources,
University of California, Berkeley. The analytical techniques employed for
measuring chlorinated hydrocarbons, including the polychlorinated biphenyls,
have been described by Risebrough, Elorant, and Berger ( 1970) and Rise-
brough (in press). Eggshells were measured by D. W. Anderson as described
in Anderson and Hickey (1970) .

Eggshell thickness. — No statistical differences were apparent between the
thickness means for four colonies (Table 2) . The 87 eggs collected in Elorida
in 1969 and 1970 averaged 9 per cent thinner than 172 eggs collected prior
to 1943 (Anderson and Hickey, 1970). It must be pointed out that the thick-
ness data presented for 1970 from the Tarpon Key colony, and undoubtedly
from all colonies as well, represent a maximum thickness for the colony. Eggs
were collected from three-egg clutches, which evidently had not lost eggs due
to shell collapse. There is therefore a greater probability that one- and two-
egg clutches, which were not sampled, have lost eggs due to excessive thinning.

Schreiber and
Risebrough

BROWN PELICAN STUDIES

129

Table 3

DDT Compounds and Polychlorinated Biphenyls in Brown Pelican Eggs, Florida

1969 AND 1970.

Concentrations in ppm of the yolk lipid and wet weight contents. Mean values with 95%

confidence limits.

Tarpon Key
Boca Ciega Bay
St. Petersburg
1969 1970

Hemp Key
Charlotte Hbr.

1970

Hall Island
Cocoa Beach

1970

Rio Del Mar
Vero Beach

1970

All

Florida

Number of

eggs

14

21

20

22

10

87

p,p'-DDE

lipid

37.2±

26.4±

18.3±

27.8±

20.6 ±

26.0±

21.5

12.0

8.6

12.3

14.1

5.6

p.p'-DDD

lipid

12.8±

6.6±

4.5±

2.9±

4.0±

5.9it

7.4

3.0

2.1

1.3

2.9

1.3

p,p'-DDT

lipid

6.0±

3.2±

1.1±

1.4±

1.0±

2.5±

3.5

1.5

0.5

0.6

0.7

0.5

Total DDT

lipid

56.0±

36.2±

23.9±

32.1±

25.7±

34.3±

32.3

16.5

11.2

14.2

18.4

7.4

wet

2.90±

1.68±

1.19±

1.45 ±

1.42±

1.67±

0.83

0.38

0.35

0.24

0.42

0.22

PCB

lipid

120.0±

68.9±

44.6 ±

63.8±

77.4±

71.2±

69.3

31.4

20.9

28.3

55.4

15.3

wet

6.21±

3.69±

2.20±

2.88±

4.20 ±

3.61 ±

2.62

0.38

1.03

0.53

1.34

1.99

Remaining eggs in those clutches were more likely thinner shelled than the
average. On 16 May 1970 a shell-less egg composed of only membrane and
albumen was found. None of the four thin shelled and crushed eggs found
in the 62 nests on the Tarpon Key colony (see Table 1) were included in this
analysis. These results regarding eggshell thinning are essentially the same
as described by Blus (1970 ) .

Chlorinated Hydrocarbon Residues. — Concentrations of the 1)1)1 com-
pounds, p,p'-DDE, p,p'-DDl) (TDE), and p,p'-l)l)T, and of the })olychlorinated
biphenyls ( PCB ) in the 87 Florida Brown Pelican eggs are presented in liable
3. Pollutant concentrations in eggs may be expressed as parts per million
(ppm) of the wet weight, including the shell; as ppm of the wet weight of the
contents (consisting of the yolk, albumen, and embryo): or as ppm of the

130

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

yolk lipid. In Table 3 concentrations are expressed as both ppm of the wet
contents and of the yolk lipid. In order to compare wet weight concentrations
among eggs Avhich may have lost moisture it is necessary to apply correction
factors (Mulhern and Reichel, 1970) . As wet weight of the contents was deter-
mined by subtracting the weight of the dried shell from the weight of the
fresh egg measured at the time of collection, a correction factor was not
necessary.

Chlorinated hydrocarbons are associated with the lipids in the yolk rather
than with albumen or shell. The lipid content of the 87 Elorida Brown Pelican
eggs averages 4.4 g per egg or 5.0 per cent of the wet weight contents. The
percentage of lipid in eggs of the White Pelican ( Pelecanus erythrorhynchos)
and the Double-crested Cormorant {Phalacrocorax auritus) are on the order
of 4.2 and 4.4 per cent respectively (Anderson et al., 1969 ) and average 6.5 per
cent in the egg contents of American Kestrels [ Falco sparverius) (Wiemeyer
and Porter, 1970) . Fresh eggs of the Common Murre ( Vria aalge) from Cali-
fornia contained 13.7 per cent lipid (Cress et al., 1971). Concentrations of
chlorinated hydrocarbons expressed on a wet weight basis only might appear
to be higher in eggs of species such as the Common Murre, with greater
amounts of lipid than in eggs of other species with lower amounts of lipid.
Concentrations in tissue such as breast muscle and brain should always be
expressed as ppm of both wet weight and lipid weight.

Yolk materials laid down in ova are derived from lipids and other compo-
nents of the blood. Presumably chlorinated hydrocarbons codeposited with the
yolk lipid are in physiological equilibrium with the chlorinated hydrocarbons
associated with the blood lipids and these in turn are in physiological equilib-
rium with the chlorinated hydrocarbons at sites such as the membranes of the
shell gland where the egg shell is deposited. Although many different physio-
logical and biochemical factors can be expected to modify these relationships
somewhat, the model appears to represent adequately the sequence of events in
the deposition of chlorinated hydrocarbons in the egg. Therefore, we prefer
to relate parameters such as eggshell changes to chlorinated hydrocarbon
concentrations in the yolk lipid, rather than in whole yolk, albumen, or total
egg contents.

In the Florida Brown Pelican eggs, as in most environmental samples, p,p'-
DDE is the most abundant of the DDT compounds. PCB, a class of compounds
with varying chlorine content, is about twice as abundant as the DDT com-
pounds (Table 3). The eggs obtained in 1969 from Tarpon Key were also
analyzed for dieldrin and endrin. Mean concentrations of dieldrin in yolk
lipid was 4.17 ppm with a range from 8.1 to 0.38 ppm. Mean concentrations
of endrin in the yolk lipid was 0.12 ppm with a range from 0.37 to 0.02 ppm.

DDT concentrations in Florida pelican eggs, with an arithmetic mean of

Sclireiber and
Risebrough

BROWN PELICAN STUDIES

131

34 ppm in yolk lipid, are higher than those in pelican eggs from lamaica (x =
5.5, n = 4), Panama (x = 11.7, n = 6), Venezuela (x = 1.0, n = 4) and Peru
(x = 0.1, n = 5) ; but are much lower than in eggs of California Brown Peli-
cans. The arithmetic mean of DDT concentration in the yolk lipid of 65 eggs,
the majority of them thin shelled and crushed, from Anacapa Island, Cali-
fornia, was 1,223 ppm. The excessively high residues in California eggs are
believed to derive from the effluent of a DDT manufacturing plant in Los
Angeles ( Risebrough et al., in prep. ) .

PCB concentrations are also higher in Florida than in the Caribbean and
lower than in the coastal waters of California ( Risebrough et al., in prep. ) .

There is a highly significant linear correlation ( r = 0.701, p < 0.01 ) be-
tween the concentration of PCB and concentration of DDE in the yolk lipid
of the Florida eggs ( Figure 1 ) . Thus, birds with high PCB also tend to have
high DDE. A similar correlation exists between PCB and DDE in California
Brown Pelicans but in the west coast ecosystems DDE is more abundant than
is PCB. We interpret this to mean that these compounds move in similar ways
through marine food chains. The sources of DDT compounds in Florida
coastal waters include aerial fallout from global sources (Tarrant and Tatton,
1968; Risebrough et al., 1968), aerial fallout from local application, and local
runoff in water. The relative importance of each source has not been deter-
mined. A study of the effects upon south Florida wildlife of the “eradication
program” for the mosquito Aedes aegypti concluded that “there was little
reason to suspect immediate and widespread damage to wildlife” from the
DDT spraying. Although many songbirds were analyzed for DDT residues in
this study, possible accumulation in marine food webs was not considered
( Lehner et al., 1967 ) .

Since several pollutants may occur together in environmental samples, it is
frequently difficult to determine which is causing an effect such as a reduc-
tion in eggshell thickness. The correlation between DDE concentration and
shell thinning of the Florida Brown Pelicans is highly significant ( r = -0.579,
p < O.OI ) . However, as PCB is also highly correlated with DDE, the correla-
tion between thickness and PCB is also significant ( r = -0.499. p < 0.01 I .
Experimental studies have shown that DDE induces shell thinning in Mallard
Ducks (Anas plalyrhynchos) (Heath et al., 1969), American Kestrels (Wie-
meyer and Porter, 1970), Japanese Quail [Coturnix coturnix) ( Stickel and
Rhodes, 1970), and Ring Doves { Streptopelia risoria) ( Peakall. 19701. hut
PCB does not affect shell thickness in Mallard Ducks ( Heath et al.. in press).
Bohwhite Quail (Colinus virginianus) , and Ring Doves ( IVakall. 1971).

I he relative contributions of the various |)ollutants to shell thinning in the
Brown Pelican is further discussed by Risebrough et al. (in j)iej). ) .

Very low concentrations of DDE are correlated with significant thinning

132

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

of eggshells of the Brown Pelican and the relationship is linear from zero
concentrations of DDE ( Risebrough et ah, in prep.). Physiological mecha-
nisms proposed to explain the effect of DDE on egg shell thickness must take
this into account. Our data are inconsistent with the theory that inhibition of
soluble carbonic anhydrase in the shell gland is responsible for shell thinning.
In all systems examined thus far, carbonic anhydrase is present in excess of
physiological needs ( Dvorchik et ah, 1971). Inhibition of a small fraction
of the soluble enzyme by low concentrations of DDE would not be expected
to produce a physiological effect, whereas our observations indicate that
small amounts of DDE are associated with a reduction of shell thickness.

Our data are consistent with a theory that postulates inhibition of a finite
number of sites in the shell gland membrane associated with transport of
calcium ions or diffusion of bicarbonate ions. The enzyme inhibited could be
an ATP-ase associated with calcium transport or a membrane-bound carbonic
anhydrase (Risebrough, Davis, and Anderson, 1970 ).

Thinning of Brown Pelican eggshells below about 0.45 mm (20 per cent
reduction) usually causes them to break during incubation ( Risebrough et al.,
in prep.). The mean reduction of 9 per cent in the Florida eggs has not yet
been observed to have an effect on population stability. Moreover, there is
no clear evidence to indicate that thinning of this magnitude interferes with
water retention or gas exchange. It may, however, increase the probability
of accidental breakage. The data in Table 1 show that a substantial number
of eggs are lost during incubation. Mysterious disappearance of eggs of the
Peregrine Falcon {Falco peregrinus) (Ratcliffe, 1970) and of American
Kestrels (Porter and Wiemeyer, 1969) coincided with shell thinning in
those species. In evolutionary terms, any significant deviation from normality
might be considered a selective disadvantage lowering the reproductive ca-
pacity and affecting the long term population stability. In areas such as
California and perhaps also Louisiana and Texas where levels of environmental
pollution are higher than in Florida, effects on Brown Pelican productivity
have been both rapid and dramatic. The species, however, is long-lived and
exhibits deferred maturity ; effects on the reproductive capacity associated with
the present level of shell thinning in Florida will not be evident for many
years.

SUMMARY

This paper summarizes the historical status of the Brown Pelican in the United States
through 1970; presents data on the effects of human disturbance on clutch size and
hatching success for a colony on Tarpon Key, St. Petersburg, Florida in 1969 and 1970;
and presents data on eggshell thickness and chlorinated hydrocarbon residues, including
polychlorinated biphenyls, for 87 eggs collected from four colonies in Florida in 1%9
and 1970. Methods of reporting pollutant residues are reviewed and the relationship

Schreiber ami
Risebrough

BROWN PELICAN STUDIES

133

between PCB’s and DDE in samples is noted. The significance of these levels of con-
tamination and attendant eggshell thinning to the Florida Brown Pelican population is
discussed.

ACKNOWLEDGMENTS

Compilation of data contained in this paper was possible only through the free ex-
change of personal observations of T. A. Beckett III, H. T. Davis, H. Hildebrand, T. Mc-
Danial, and R. H. Steiner. Charlotte Smith of the Massachusetts Audubon Society com-
piled observations of Brown Pelicans from Audubon Field Notes and offered us her
summary. G. E. Woolfenden is judiciously guiding Schreibers’ dissertation research. He,
D. W. Anderson, B. A. Harrington, F. E. Lohrer, W. B. Robertson, Jr., Susan C. White,
and L. E. Williams, Jr. read versions of the manuscript.

We thank Patricia K. Schmidt, T. Schmidt, and P. Reiche for assistance in the labora-
tory.

G. E. Watson of the Smithsonian Institution provided Schreiber with boat and motor
necessary for his field work. The Frank M. Chapman Memorial Fund of the American
Museum of Natural History, a Grant-in- Aid of Research from the Society of the Sigma
Xi, and a grant from the International Council for Bird Preservation supported field work
in Florida. The National Audubon Society provided funds for both field work and
chemical analysis; we thank Roland Clement for his assistance. The National Science
Foundation, Grant GB-II649, to the Institute of Marine Resources, University of Cali-
fornia, H. S. Olcott, Principal Investigator, supported field and laboratory studies.

LITERATURE CITED

American Ornithologists’ Union. 1957. Check-list of North American Birds. 5th
ed. Amer. Ornithologists’ Union.

Anderson, D. W., and J. J. Hickey. 1970. Oological data on egg and breeding char-
acteristics of Brown Pelicans. Wilson Bull., 82:14-28.

Anderson, D. W., J. J. Hickey, R. W. Risebrough, D. F. Hughes, and R. E. Christen-
sen. 1969. Significance of chlorinated hydrocarbon residues to breeding pelicans
and cormorants. Canadian Field-Naturalist, 83:93-112.

Bailey, A. M., and E. G. Wright. 1931. Birds of southern Louisiana. Wilson Bull., 43:
114^142.

Bartholomew, G. A., Jr., and W. R. Dawson. 1954. Temperature regulation in young
pelicans, herons, and gulls. Ecology, 35:466-472.

Beckett, T. A., HI. 1%6. Deveaux Bank — 1%4 and 1965. Chat, 30:93-100.

Bent, A. C. 1922. Life histories of North American petrels and pelicans and their
allies. U. S. Natl. Mus. Bull,, 121.

Blus, L. j, 1970. Measurements of Brown Pelican eggshells from Florida and South
Carolina. BioScience, 20:867-869.

Burleigh, T. 1). 1958. Georgia birds. Univ. Oklahoma Press, Norman. Oklahoma.

Dvorchik, B. H., M. IsTiN, AND T. H. Maren. 1971. Do(‘s DDT irdiibit earbonie
anhydrase? Science, 172:728-729.

Evenden, F. G. 1968. Report of committee on conservation. 1968. Auk. 85:669 677.

Evenden, F. G. 1%9. Report of committee on conservation, 1969. Auk, 8f>:738 744.

Goldman, L. C. 1951. South Texas Region. Audubon Field Notes, 5:298 300.

Goldman, L. C., and F. (L Watson. 1952. South 'Fexas Region. Audubon Field
Notes, 6:289-291.

134

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Gress, F. 1970, Reproductive status of the California Brown Pelican in 1970, with
notes on breeding and natural history. California Dept. Fish and Game, Wildlife
Management Admin. Report 70-6.

Gress, F., R. W. Risebrougii, and F. C. Sibley. 1971. Shell thinning in eggs of
Common Murres Uria aalge from the Farallon Islands, California. Condor, 73:368-
369.

Heath, R. G., J. W. Spann, and J. F. Kreitzer. 1969. Marked DDE impairment of
Mallard reproduction in controlled studies. Nature, 224:47-48.

Heath, R. G., J. W. Spann, J. F. Kreitzer, and C. Vance. In press. Effects of poly-
chlorinated biphenyls on birds. Proc. XV Internatl. Ornithol. Congress, The Hague.

Howell, A. H. 1932. Florida bird life. Florida Dept. Game and Fresh Water Fish,
Tallahassee, Florida.

Imhoff, T. a. 1960. Central Southern Region. Audubon Field Notes, 14:454-456,

Imhoff, T. a. 1962. Alabama birds. Univ. Alabama Press, University, Alabama.

Jehl, j. R., Jr. 1969. A wonderful bird was the pelican. Oceans, 2:11-19.

JoANEN, T., AND D, A. Neal. 1971. The return of the Brown Pelican. Louisiana Con-
servationist, May, June: 10-13,

Lehner, P. N., T. 0. Boswell, and F. Copeland. 1967. An evaluation of the effects
of the Aedes aegypti eradication program on wildlife in South Florida. Pesticides
Monitoring Journ., 1:29-34.

Lowery, G. H., Jr. 1960. Louisiana birds. 2nd ed. Louisiana State University Press,
Baton Rouge, Louisiana.

McIlhenny, E. a, 1943. Major changes in the bird life of southern Louisiana during
sixty years. Auk, 60:541-549.

Mason, C. R. 1945. Pelican travels. Bird-Banding, 16:134-143.

Mulhern, B. M., and W. L, Reichel. 1970. The effect of putrefaction of eggs upon
residue analysis of DDT and metabolites. Bull. Environ. Contam. Toxicol.,
5:222-225.

Murphy, R. C. 1936. Oceanic birds of South America. Vol. 2. Amer. Mus. Nat. Hist.,
New York,

Newman, R. J, 1956. Central Southern Region. Audubon Field Notes, 10:387-390.

Newman, R. J. 1957. Central Southern Region. Audubon Field Notes, 11:409-413.

Newman, R. J, 1958«. Central Southern Region. Audubon Field Notes, 12:284-287.

Newman, R. J. 19586. Central Southern Region. Audubon Field Notes, 12:417-421.

Newman, R. J. 1959a. The Changing Seasons. Audubon Field Notes, 13:4-10,

Newman, R. J. 19596. Central Southern Region. Audubon Field Notes, 13:298-302.

Oberholser, H. C. 1938. The bird life of Louisiana. Dept, of Conservation, New Or-
leans.

Palmer, R. W. 1962. Handbook of North American birds. Vol. 1. Yale University
Press, New Haven.

Peakall, D. B. 1970. p,p'-DDT: Effect on calcium metabolism and concentration of
estradiol in the blood. Science, 168:592-594.

Peakall, D. B. 1971. Effects of polychlorinated biphenyls (PCB’s) on the eggshells
of Ring Doves. Bull. Environ. Contam. Toxicol., 6:100-101.

Pearson, T. G. 1918. Report of T. Gilbert Pearson, Secretary , Bird-Lore, 20:455.

Pearson, T. G. 1921. Notes on the bird-life of southeastern Texas. Auk, 38:513-523.

Porter, R. D., and S. N. Wiemeyer. 1969. Dieldrin and DDT : Effects on Sparrow
Hawk eggshells and reproduction. Science, 165:199-200.

Schreiber and
Risebrough

BROWN PELICAN STUDIES

135

Ratcliffe, D. a. 1970. Changes attributable to pesticides in egg breakage frequency
and eggshell thickness in some British birds. J. Appl. Ecol., 7:67-115.

Risebrough, R. W. In press. Determination of polychlorinated biphenyls in environ-
mental samples. Proc. of the Symposium on the identification and measurement
of environmental pollutants. Ottawa. 1971.

Risebrough, R. W., R. J. Huggett, J. J. Griffin, and E. D. Goldberg. 1968. Pesti-
cides: Translantic movements in the northeast trades. Science, 159:1233-1236.

Risebrough, R. W., J. D. Davis, and D. W. Anderson. 1970. Effect of various chlori-
nated hydrocarbons. In Gillett, J. W. (Ed.). The biological impact of pesticides in
the environment. Environmental Health Series 1, Oregon State Univ., Corvallis,
Oregon.

Risebrough, R. W., G. I. Florant, and D. D. Berger. 1970. Organochlorine pollutants
in Peregrines and Merlins migrating through Wisconsin. Canadian Field-Naturalist,
84:247-253.

Risebrough, R. W., F. C. Sibley, and M. N. Kirven. 1971. Reproductive failure of
the Brown Pelican on Anacapa Island in 1969. Amer. Birds, 25:8-9.

Schreiber, R. W., and R. L. DeLong. 1969. Brown Pelican status in California. Audu-
bon Field Notes, 23:57-59.

Stewart, J., Jr. 1962. Central Southern Region. Audubon Field Notes, 16:480-481,
485^86.

Stickel, L. F., and L. I. Rhodes. 1970. The thin eggshell problem. In Gillett, J. W.
(Ed.). The biological impact of pesticides in the environment. Environmental Health
Series 1, Oregon State University, Corvallis, Oregon.

Tarrant, K. R., and J. O’G. Tatton. 1968. Organochlorine pesticides in rainwater
in the British Isles. Nature, 219:725-726.

VAN Tets, G. F. 1965. A comparative study of some communication patterns in the
Pelecaniformes. Ornithol. Monogr. No. 2, American Ornithologists’ Union.

Voous, K. H. 1957. The birds of Aruba, Curacao, and Bonaire. Studies on the fauna
of Curacao and other Caribbean Islands, No. 29.

Webster, F. S., Jr. 1960. South Texas Region. Audubon Field Notes, 14:460-465.

Webster, F. S., Jr. 1963. South Texas Region. Audubon Field Notes, 17:469-471.

Wetmore, a. 1945. A review of the forms of the Brown Pelican. Auk, 62:577-586.

Wetmore, a. 1965. The birds of the Republic of Panama. Smithsonian Misc. Coll.,
No. 150.

WiEMEYER, S. N., AND R. D. PoRTER. 1970. DDE thins eggshells of captive American
Kestrels. Nature, 227:737-738.

Williams, L. E., Jr., and L. Martin. 1968. Nesting status of the Brown Pelican in
Florida in 1968. Quart. J. Florida Acad. Sci., 31: 130-140.

Williams, L. E., Jr., and L. Martin. 1970. Nesting populations of Brown Pelicans in
Florida. Proc. 24th Annual Conf. S. E. Assoc. Game and Fish Comm.

Wray, D. L., and H. T. Davis. 1959. Birds of North Carolina. North Carolina Dept,
of Agriculture, Raleigh, North Carolina.

DEPARTMENT OF BIOLOGY, UNIVERSITY OF SOUTH FLORIDA, TAMPA, FLORIDA
33620 AND BODEGA MARINE LABORATORY, P.O. BOX 217, BODEGA BAY. CALI-
FORNIA 94923, 14 JUNE 1971.

BEHAVIORAL RESPONSES OF MIGRATING BIRDS TO
DAYLIGHT AND DARKNESS: A RADAR AND DIREGT
VISUAL STUDY

Sidnp:y a. Gauthreaux, Jr.

IN spring nearly all the passerine migrants that enter southern Louisiana do
so after completing a migration across the Gulf of Mexico, and although
most of the birds are considered nocturnal migrants and embark on their
crossing at night (Lowery, 1951), they usually arrive on the northern Gulf
coast during the daytime (Lowery, 1955; Newman, 1957). The migrants
that arrive during the day alight shortly after reaching land and usually
initiate another migration the same night, but occasionally the trans-Gulf
flights continue to arrive after nightfall (Gauthreaux, 1968, 1971). Because
of the timing of these movements, I have been able to examine the landing
behavior and the altitudinal and spatial distribution of the same population
of migrants aloft during the day and at night.

MATERIALS AND METHODS

This paper is l)ased on radar, direct visual, and acoustic methods which are essentially
the same as those given in earlier papers (Gauthreaux, 1969, 1970, 1971). I gathered
data from the WSR-57 radar and made telescopic watches at Lake Charles and New
Orleans, Louisiana, during spring migration from 1965 to 1967 and accumulated infor-
mation on the landing behavior of the trans-Gulf migrants on the Louisiana coast from
1958 to 1968 (see Newman, 1958; Newman and Lowery, 1959). Call-notes from migrants
aloft were counted during daytime and nighttime telescopic watches throughout the
study.

DAYTIME FLOCKING

The data I collected with a telescope and binoculars indicate that the
majority of passerines arriving from over the Gulf during the daytime were
in compact flocks. Although isolated passerines were frequently recorded,
the total number of birds in flocks exceeded the total number of single birds
by a factor of three. The aggregations of small and medium sized passerines
ranged from two or three individuals to more than 100; the average was 20.
The largest flock I saw with the telescope was 175 birds, and the largest flock
I recorded with binoculars was 300 birds.

The migrants were in four basic flight formations. About 70 per cent of
the flocks were nearly circular or slightly oval in shape. About 30 per cent
were in a line formation; in 20 per cent the line was perpendicular to the
flight direction, and in the remaining 10 per cent it was parallel to the flight
direction. On two occasions the migrants appeared to be randomly spaced.

136

Sidney A.
Gauthreaux

BEHAVIORAL RESPONSES OF MIGRATING BIRDS

137

Fig. 1. Photographs of the radar screen at Lake Charles, Diuisiana, during spring
of 1965. A, C, and E are exposures for a single revolution of the antenna; B, 1), and I
are five-minute time exposures. A and H — 19 March. 23:28 to 23:33 CST. 4° antenna
elevation, no migration. C and D — 15 May, 20:11 to 20:16 (iST, 3° ant, elev.. nocturnal
migration. E and F— 15 May, 18:46 to 18:51 C.ST, 3° ant. elev., daytime migration.

hut this could have resulted from several large flocks joining togelher, I he
following example illustrates the comjiactness of the flocks. On the afternoon
of 7 May 1965 two flocks of 50+ and 15+ jiasserines passed throtigh the
field of the vertical telescope when a partial moon was located in the field

138

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

of view. From each flock 12 and seven birds, respectively, were over the
lunar background at the same time.

Figures lA and IB show the radar screen ( PPI ) of the WSR-57 at Lake
Charles, Louisiana, when there was no migration. The permanent echoes
in the middle of the radar screen are from ground objects in the vicinity
of the radar installation and are present in the other radar photographs. The
echoes on the PPI from arriving trans-Gulf migrants were coarse bright dots
( Figures IE and IF ) . They were strong and persistent and could be tracked
for distances of two to six nautical miles. Finer echoes were often distributed
among the larger ones, and frequently several coarse echoes coalesced on
the radar screen. Although the density of the dot echoes occasionally caused
saturation of the PPI (large areas of solid echo coverage), the concentrations
were usually such that separate echoes were distinguished and counted.

By employing the radar’s attenuation circuits and reducing signal strength,
I estimated the relative abundance of different flock sizes. Forty-five per cent
contained 12 birds or fewer; 55 per cent contained 13 to 200+ birds, and
the median flock size was 19 birds. The earliest that I saw radar echoes from
trans-Gulf migrants offshore was 41 minutes before sunrise, and the echo pat-
tern suggested that the birds were already flocked.

LANDING BEHAVIOR

In favorable weather (clear to partly cloudy skies and southerly winds),
most flocks of trans-Gulf migrants passed over the first coastal woodlands
with only a few birds dropping out and alighting; the majority continued
farther inland to the first extensive forests. When rain and adverse winds
were present over the Gulf, or the Louisiana coast, or both, many more in-
dividuals landed in coastal woodlands. Under these conditions entire flocks
often plummeted from great heights into the trees. When viewed through
binoculars from one end of a wooded ridge, the migrants looked like large,
dark hailstones falling into the trees.

The following sequence of events characterizes the landing behavior of
the migrants as diagramed in Figure 2. As a flock high aloft moved over a
coastal woodland some of the individuals hesitated, hovered, or flew in broad,
shallow spirals while the remaining flock members continued farther inland.
The individuals that left the flock then closed their wings and dove nearly
straight down. Diving at great speed the migrants occasionally braked their
descent by quickly flitting their wings, and just above the trees they abruptly
pulled out of the dive producing a distinct whizzing sound. The birds then
continued flying rapidly for 10 to 50 feet and landed with a quick flutter of
their wings. After alighting the birds often remained motionless for two or
three minutes, and then preened for two or three additional minutes. The

Sidney A.
Gauthreaux

BEHAVIORAL RESPONSES OF MIGRATING BIRDS

139

N

S

Fig. 2. Daytime landing sequences of trans-Gulf migrants in a coastal woodland. The
bird postures figured on the right side are adopted during the landing behavior.

grounded migrants then started to feed, and many of the birds while moving
from tree to tree continued in the direction of their migration.

When observed through the vertical telescope certain of the flocks aloft
appeared to be aggregations of a single species, and I verified this on those
occasions when entire flocks dove into the trees. I recorded the following
species in homogeneous species flocks: Eastern Kingbird {Tyranmis tyran-
nus ) , Catbird { Dumetella carolinensis ) , Wood Thrush ( Hylocichla mustelina) .
Red-eyed Vireo iVireo olivaceus } , Tennessee Warbler ( V ermivora pere^rina) .
I Yellow Warbler iOendroica petechia). Bay-breasted Warbler { Dendroica
castanea). Bobolink { Dolichonyx oryzivorus) , Orchard Oriole [Icterus
' spurius), Baltimore Oriole {Icterus ^alhula) , Scarlet Tanager [Piranha
i olhvacea ) , Summer Tanager ( Piran{Z,a rubra ) , Rose-breasted Grosbeak ( Pheuc-
ticus ludovicianus ) , Blue Grosbeak [Guiraca caeridea). Indigo Bunting [Ibis-
1 serina cyanea), Painted Bunting iPasserina ciris) . and Dickcissel [Sjnza
' arnericana) , In addition, some flocks contained ordy one sex (e.g.. Baltimore

I

140

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Table 1

Altitude of Daytime Migration at Lake Charles and New Orleans
(Expressed as percentage of total number of dot echoes aloft)

Antenna elevation Altitudinal zones in feet

2.5°

796-1,859

1,592-3,718

2,388-5,577

3,184- 7,437

3,980- 9,296

(N = 4)

X 8

11

30

36

15

S.D. 7

3

10

3

14

3.0°

1,061-2,125

2,123-4,251

3,184-6,377

4,246- 8,503

5,307-10,629

o

ro

II

X 5

10

29

38

18

S.D. 6

5

10

11

12

o

O

1,593-2,659

3,186-5,319

4,779-7,979

6,373-10,638

7,966-13,298

(N = 9)

X 5

15

35

35

10

S.D. 3

8

13

16

10

Oriole. Scarlet Tanager. Rose-breasted Grosbeak, Blue Grosbeak, Indigo
Bunting, and Painted Bunting I . It was often difficult to detect homogeneous
species flocks once the birds landed and fed together in the trees. I did notice
frequently that certain species were more abundant in certain portions of a
particular woodland and that the relative abundance of a particular species
differed markedly among different coastal woodlands. Two species of herons,
the Green Heron ( Butorides virescens ) and the Yellow-crowned Night Heron
(Nyctanassa violacea). showed the same landing behavior as the landbirds,
and both of these species were commonlv found resting in trees after com-
pleting a trans-Gulf migration.

ALTITUDE OF DAYTIME AND NIGHTTIME FLIGHTS

Table 1 gives the altitudinal distribution of the trans-Gulf migrants during
their daytime arrival at the latitude of the Lake Charles and New Orleans
radar stations ( 30°N ) . I gathered the data by counting dot echoes on the
radar screen in a 5 X 5 nautical mile area centered at 5, 10, 15, 20, and 25
nautical mile range. The numbers of dot echoes were averaged for each alti-
tudinal stratum and were corrected for increasing beam size and loss of power
that follows the fourth power rule ( see Eastwood, 1967) .

On Lake Charles radar the altitude of the daytime movements averaged
approximately 500 feet higher over land than over the Gulf, and flights were
frequently 1,000 feet higher over New Orleans than over Lake Charles. The
reason is probably that the migrants rather consistently flew above the con-
vective cumulus clouds that formed near the coastline and piled higher as
thev moved inland with southerlv winds. The cumulus over New Orleans

Sidney A.
Gauthreaux

BEHAVIORAL RESPONSES OF MIGRATING BIRDS

141

Table 2

Altitude
( Expressed

OF Nighttime Migration at New Orleans
as percentage of total number of birds aloft)

Antenna elevation

Altitudinal zones

in feet

2.5°

796-3,718

1,592-5,577

2,388-7,437

3,184-9,296

(N = 34)

X

70

20

8

4

S.D.

19

13

10

8

796-1,592

1,592-2,388

2,388-3,184

3,184-3,980

(N = 30)

X

74

18

1

2

S.D.

17

14

8

3

were better developed than those over Lake Charles because the former city
is farther inland than the latter, and the cloud formations had more time to
build up, inducing the birds to fly higher. Whenever cumulus development
exceeded 7,000 feet the migrants lowered their altitude. The distribution of
the daytime flights was frequently the same as the altitude of the inversion
layer aloft, but cumulus rarely develop above the altitude of an inversion.
The air just above an inversion is quite stable and flows smoothly, and Raynor
(1956) has suggested that migrants might prefer to fly in this zone.

Excluding cirrus overcast, solid overcast covered southern Louisiana on 11
days when trans-Gulf flights arrived. On nine of these days the mean alti-
tude of the overcast base was 2,540 feet ( s.D. = 1,160 feet; range = 1,300 to
5,000 feet), and 80 to 95 per cent of the migrants displayed on radar were
above the overcast. Only on two days when the base of the overcast was at
7,500 feet and 10,000 feet did most of the migrants fly below the cloud layer.
On 30 April 1967 cumulus cloud tops (/io coverage) extended up to 3,100
feet and the base of a higher cloud layer (%o coverage) was at 10,000 feet.
On this afternoon 83 per cent of the migrants passing over the radar station
flew between 4,000 and 6,000 feet between the cloud layers. On certain occa-
sions some migrants appeared to be flying in clouds. Three times with
binoculars I saw flocks of migrants so close to the base of a cloud that some
individuals in the flocks momentarily disappeared into the cloud,
i Whenever migrants continued to arrive from over the Gulf and pass over
the radar stations near nightfall, their height lowered markedly. The average
change from the daytime altitudinal distribution to the nighttime one was
! approximately 3,0(K) feet. Table 2 gives the quantity of nocturnal migration
per altitudinal stratum expressed as the percentage of the total number of birds
j aloft. These data are from New Orleans during the spring of 1967. and I
I gathered them by using the attentuation techni(jue ( (iauthreaux. 1970). I he

1

142

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

data were corrected in the same manner as the daytime data, but they refer
to densities of individual birds and not flocks. Seventy per cent of the
migrants at night were most frequently between 796 feet and 3,718 feet.
Within this zone approximately 75 per cent were between 796 feet and 1,592
feet.

Excluding cirrus overcast, solid overcast over southern Louisiana occurred
on 5 nights of migration. The altitudes of the solid cloud layers on three of
the nights were 2,800; 8,000; and 9,000 feet, respectively, and the migrants
were below the overcast. On the remaining two nights the overcast was at
1,000 and 900 feet, and the migrants were in and above the cloud layer. Call-
notes from the migrants on the latter two nights were quite numerous ( 50 to
100 per minute ) .

I recorded nocturnal flights at altitudes much higher than usual on 2 May
and 4 May 1967. On 2 May, 42 per cent of the migrants were between 5,580
and 7,440 feet; on 4 May, 41 per cent were between 3,720 and 5,580 feet.
When these altitudes were compared with the winds aloft (radiosonde-radar
tracked balloon) for these nights, the migrants were found to be flying with
favorable winds in warmer air above shallow cold fronts and northerly winds
that had moved into the area.

CHANGE IN FLOCKING BEHAVIOR AT NIGHTFALL

As the altitude of migration lowered near nightfall another feature of the
migration also changed — the flocks characteristic of daytime migration dis-
banded. On 11 occasions during full moon periods, I observed by moon-
watching the breakup of flocks as trans-Gulf migrants continued to arrive
over the Louisiana coast near sunset and later. The moon rises before sunset
on the days preceding the full moon and it rises at the time of sunset on the
date of the full moon. I began the watches while it was still daylight, and
the passerine migrants that crossed the moon were still in tight aggregations
with up to 10 birds against the moon at one time. As the watches continued
and darkness approached the aggregations became looser, and shortly after
dark only single birds passed before the lunar background. On five of these
occasions thin cirrus cloud veiled the moon and the entire field of the tele-
scope could be used to see the silhouettes of the migrants. Even with the added
field of view only single landbirds were seen once it was night. After dark the
ducks and shorebirds that passed before the moon were clearly grouped into
tight flocks.

On the radar screen from the time of sunset to the time of darkness the large
dot echoes characteristic of daytime migration changed to a finely stippled
echo pattern. The fine dust-like echoes on the PPI of the WSR-57 are typical
of nocturnal migration when passerine birds are flying singly in the night

cSre'aux BEHAVIORAL RESPONSES OF MIGRATING BIRDS 143

Fig. 3. Scatter diagram showing the time of the breakup of daytime flocks. Upper
and lower dashed lines represent the end of nautical and civil twilight, respectively. The
solid line is the computed line that best fits the points. The solid circles are points for
New Orleans and the crossed circles are points for Lake Charles.

sky (Figs. 1C and ID). The flock echoes on radar started to disliand about
26 to 46 minutes after sunset. The mean time of the start of flock hreaku})
based on 22 cases is 35 minutes after sunset with a standard deviation of 5
minutes. Most of the dot echoes were completely fragmented about 15 minutes
later, or after the end of civil twilight and the beginning of nautical twi-
light. The duration of civil twilight during spring migration at 30°\ is 21

144

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

to 25 minutes, and it is followed by nautical twilight which lasts for 52 to 59
minutes from 19 March to 19 May. Eigure 3 is a scatter diagram showing
the time of flock breakup in relation to the time of sunset and the beginning
of nautical twilight. The breakup of passerine flocks aloft occurs about the
same time as the exodus of grounded trans-Gulf migrants from the woodlands
of southern Louisiana (Gauthreaux, 1971), and both events are clearly dis-
tinguishable on the radar screen.

CALLING BY MIGRANTS ALOFT

If trans-Gulf migrants flying high overhead during the day called, I did
not hear them. However, when migrants were alighting in coastal woodlands
during the day, they often gave call-notes. Passerine migrants called in-
frequently even when flocks aloft were disbanding and migrants were de-
parting from woodlands during the first part of the night under fair skies. In
contrast, I counted many call-notes from songbirds early in the evening on
overcast nights and when trans-Gulf migrants were arriving after dark and
landing. The greatest amount of calling from passerines usually occurred
when the radar showed the density of migration to be falling rapidly. Shore-
birds and waterfowl normally called frequently after dark and throughout
the first half of the night.

DISCUSSION

Lowery ( 1951 ) established that nocturnal passerine migrants cross the
moon individually as they initiate their trans-Gulf migration from areas
south of the Gulf of Mexico. In this paper I have emphasized that these
nocturnal migrants arrive from over the Gulf on the northern coast during
the daytime in flocks. How single birds over the Gulf manage to congregate
into homogeneous, single-species flocks is an intriguing question that is not
easily answered. The radar findings of Gehring 1 1963 I on davtime autumn
migration in northern Switzerland suggest that the grouping possibly takes
place at dawn. He found that the initial phases of diurnal migration occurred
about half an hour before sunrise and at that time the radar echoes from the
migrants were small and diffuse — an echo pattern characteristic of nocturnal
migrants flying indvidually. As the light intensity increased the echoes be-
came larger probably due to a tendency of the birds to form larger flocks.
It is possible that nocturnal passerine migrants when forced to continue
migrating in daylight over the Gulf of Mexico show the same flocking be-
havior exhibited by typical diurnal migrants at dawn. The two types of
migrants show additional similar behaviors.

Gehring (1963) discovered that the altitude of migration over northern
Switzerland decreased until half an hour before sunrise when it increased
sharply. He attributed the lowering phase to nocturnal migrants ending their

GauSre'aux BEHAVIORAL RESPONSES OE MIGRATING BIRDS 145

migration and the sharp increase to diurnal migrants. Myres (1964) re-
corded a late-night descent of nocturnal migrants flying over the southern
part of the Norwegian Sea and the northern part of the North Sea, but near
dawn the migrants gained altitude quickly. Although my evidence is cir-
cumstantial, nocturnal migrants probably show a gain in altitude at dawn
over the northern Gulf, for the altitude of daytime migration from over the
Gulf is approximately 3,000 feet higher than that typical for nighttime
migration in the same area. Unfortunately, at the critical time when the
ascent behavior occurs most of the migrants are too far offshore to be de-
tected by coastal radar.

Lowery (1951) and Lowery and Newman (1955) found that most pas-
serines aloft at night migrate singly and are randomly spaced. Nisbet ( 1963a)
concluded that . . migration in small groups is a habit widespread in at
least three North American families, Parulidae, Turdidae and Emberizidae,
as well as in non-passerines.” He pointed out that it would be valuable to
seek direct visual evidence for the shape and size of groups by observing
either when the moon is very low, or when haze or thin clouds cover the
moon and a relatively large area of the sky can be examined with a low-
power binocular. My telescopic and binocular observations under the latter
conditions do not support Nisbet’s conclusions. I found that daytime flocks
of passerines disband at dusk; shorebirds and waterfowl remain in flocks.
The change in echo pattern on the radar screen of the WSR-57 further sup-
ports the conclusion that most nocturnal passerine migrants fly individually
in the night sky. According to the evidence presented by Eastwood and
Rider ( 1966 ) some of the echoes on radar at long ranges are probably true
groups of nocturnal migrants similar to those found by day: others, and
perhaps the majority, are pseudo-groups which are a consequence of the
pulse-volume effect (poor radar resolution) particularly with 23- and 10-cm
radars. Schaefer ( 1968) also found by careful analysis of radar signals from
migrating birds that the majority of nocturnal migrants over central England
fly singly. Furthermore, when passerine migrants initiate their flight from
woodlands at the beginning of the night they do so individually and not in
groups ( Hebrard, 1971 ) .

The altitude of migration lowered during twilight whenever trans-Gulf
migrants continued to arrive from over the Gulf near nightfall. Bellrose and
Sieh (1960) described a similar phenomenon in flocks of migrating ducks.
They recorded a gradual descent of birds from 2,0(K) or more feet to 500 feet
as darkness approached on an overcast afternoon and believed that the ducks
were attempting to remain in visual contact with the ground. I his beha\ ior
should be looked for at other locations where nocturnal migrants are re-
(juired to fly over 21 hours without landing. Ihe lowering of the altitude

146

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

at nightfall does not appear to be related to landing, for the number of mi-
grants aloft usually increased after the descent as grounded migrants started
their migration. The average altitude of nocturnal migration that I recorded
from southern Louisiana is lower than that reported by certain workers (e.g.,
Lack, 1960; Nisbet, 19636; Bellrose and Graber, 1963), but it is very close
to other published figures (e.g., Eastwood and Rider, 1965; Able, 1970;
Bellrose, 1971).

During the day the altitude of migration gradually increased as migrants
crossed the coastline and moved inland. Similar altitudinal differences over
land and sea have been reported by Bergman and Donner (1964) and East-
wood and Rider (1965). The propensity of trans-Gulf migrants to gradually
gain altitude after crossing the coast is probably a response to stay above the
building cumulus over land. Despite the increase in altitude, most birds
landed when they reached the first inland forests. Although my data are few,
it appears that migrants fly above overcast during the day when the cloud
layer is under 7,000 feet. At night when solid cloud cover is above 3,000 feet,
most migrants are below it, but when the overcast is lower most migrants
fly in or above the cloud.

Graber ( 1968 ) reported that nocturnal migrants normally call more
frequently later in the night reaching a peak in the pre-dawn hours. He
also found that cloud cover causes a sharp increase in the number of call-
notes. In southern Louisiana during the first part of the night, flight calls
from passerine migrants aloft were scarce unless the birds were landing or it
was overcast. When my radar and telescopic observations revealed that the
density of nocturnal migration was declining rapidly, calling by the migrants
was greatest. Hebrard (1971) found that nocturnal migrants did not call
when they initiated their flights from woodlands in coastal Louisiana. Simi-
larly, I did not hear flight calls when the daytime flocks disbanded at night-
fall. Waterfowl and shorebirds called frequently at the beginning of the
night even under clear skies. That calling serves some function in flock
maintenance cannot be disputed, but it also seems plausible that calling by
passerine migrants at night functions in some manner in the landing process.
Exactly what that function is will require further investigation.

SUMMARY

I studied the behavior of migrating birds aloft by means of telescopic and binocular
observations during the day (open sky overhead) and at night (ceilometer and moon-
watching) and with WSR-57 radars in southern Louisiana. Spring passerine migrations
across the Gulf of Mexico usually arrived on the northern Gulf coast during the day-
light hours, and most of the birds were in tight flocks that averaged about 20 birds.
On radar the flocks produced coherent dot echoes, and most occurred at an altitude of
4,(XK) to 5,(KX) feet (1,220 to 1,524 meters). When landing the migrants dove nearly

Sidney A. BEHAVIORAL RESPONSES OF MIGRATING BIRDS

147

straight down from these altitudes and produced a whizzing sound as they pulled out
of the dive just above the trees.

The daytime flocks of passerines disbanded about 30 to 45 minutes after sunset,
and the altitude of the migration lowered approximately 3,000 feet (915 meters). At
night individual passerines produced fine, dust-like echoes on the radar screen while
flocks of waterfowl and shorebirds contributed the scattered dot echoes. Most noc-
turnal migration occurred between 800 and 1,600 feet (244 to 488 meters). Flight calls
from migrants were heard during the day when the birds were landing. Passerine calling
at the beginning of the night was primarily associated with landing and overcast. Water-
fowl and shorebirds called regularly during the first part of the night even under clear
skies. Calling by migrants aloft probably serves to keep individuals of a flock together
and functions in the landing of songbird migrants at night.

ACKNOWLEDGMENTS

A portion of this work was included in my Ph.D. dissertation submitted to the Graduate
School of Louisiana State University. I am particularly indebted to Drs. George H.
Lowery, Jr., and Robert J. Newman for their assistance during the preparation of the
dissertation. This paper was presented in abbreviated form at the Symposium on Bird
Migration in the Region of the Gulf of Mexico held during the 1971 annual meeting of
the Wilson Ornithological Society at Dauphin Island, Alabama. The manuscript was
brought into final form while I held a grant (71-1974) from the Air Force Office of
Scientific Research.

LITERATURE CITED

Able, K. P. 1970. A radar study of the altitude of nocturnal passerine migration.
Bird-Banding, 41:282-290.

Bellrose, F. C. 1971. The distribution of nocturnal migrants in the air space. Auk,
88:397-424.

Bellrose, F. C., and R. R. Graber. 1963. A radar study of the flight direction of
nocturnal migrants. Proc. XIII Internatl. Ornithol. Congr. :362-389.

Bellrose, F. C., and J. G. Sieh. 1960. Massed waterfowl flights in the Mississippi
Flyway, 1956 and 1957. Wilson Bull., 72:29-59.

Bergman, G., and K. O. Donner. 1%4. An analysis of the spring migration of the
Common Scoter and the Long-tailed Duck in southern Finland. Acta Zool. Fennica.
105:3-59.

Eastwood, E. 1967. Radar ornithology. Methuen, London.

Eastwood, E., and G. C. Rider. 1965. Some radar measurements of tlie altitude of
bird flight. Brit. Birds, 58:393-426.

Eastwood, E., and G. C. Rider. 1%6. Grouping of nocturnal migrants. Nature, 211:
1143-1146.

Gautiireaux, S. a., Jr. 1968. A (juantitative study by radar and telescope of the
vernal migration of birds in coastal Louisiana. lln{)ubl. IMi.D. diss(*rtation, Louisiana
State Univ. Baton Rouge. (IJniv. Microfilms, Ann Arbor, Michigan. Diss. Absir.,
29:3538-B).

Gautiireaux, S. A., Jr. 1969. A portable ceilometer tccbni(|ue for stmlying low-le\cl
nocturnal migration. Bird-Banding, 40:309-320.

Gautiireaux, S. A., Jr. 1970. Weather radar <|uantificalion (>f bird migration, llio-
Science, 20:17-20.

148

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Gautiiheaux, S. a., Jr. 1971. A radar and direct visual study of passerine spring mi-
gration in southern Louisiana. Auk, 88:343-365.

Geiiring, W. 1963. Radar- und Feldbeobachtungen iiber den Verlauf des Vogelzuges
im Schweizerischen Mittelland : Der tagzug im Herbst. Ornithol. Beob., 60:35-68.

Graber, R, R. 1%8. Nocturnal migration in Illinois — different points of view. Wilson
Bull., 80:36-71.

Hebrard, J. J. 1971. The nightly initiation of passerine migration in spring: A direct
visual study. Ibis, 113:8-18.

Lack, D. 1960. The height of bird migration. Brit. Birds, 53:5-10.

Lowery, G. H., Jr. 1951. A quantitative study of the nocturnal migration of birds.
Univ. Kansas Publ. Mus. Nat. Hist., 3:361-472.

Lowery, G. H., Jr. 1955. Louisiana birds. Louisiana State Univ. Press, Baton Rouge.

Lowery, G. H., Jr., and R. J. Newman. 1955. Direct studies of nocturnal bird migra-
tion. In A. Wolfson (Ed.), Recent studies in avian biology. Univ. Illinois Press,
Urbana.

Myres, M. T. 1964. Dawn ascent and reorientation of Scandinavian thrushes iTurdus
spp.) migrating at night over the northeastern Atlantic Ocean in autumn. Ibis,
106:7-51.

Newman, R. J. 1957. Spring migration — Central Southern Region. Audubon Field
Notes, 11:350-357.

Newman, R. J. 1958. Spring migration — Central Southern Region. Audubon Field
Notes, 12:358-359.

Newman, R. J., and G. H. Lowery, Jr. 1959. The changing seasons — A summary of
the 1959 spring migration and its geographic background. Audubon Field Notes,
13:346-352.

Nisbet, I. C. T. 1%3«. Quantitative study of migration with 23-centimetre radar.
Ibis, 105:435-460.

Nisbet, I. C. T. 1%36. Measurements with radar of the height of nocturnal migration
over Cape Cod, Massachusetts. Bird-Banding, 34:57-67.

Raynor, G. S. 1956. Meteorological variables and the northward movement of noc-
turnal land bird migrants. Auk, 73:153-175.

Schaefer, G. W. 1968. Bird recognition by radar. A study in quantitative radar
ornithology. In, The problems of birds as pests. Academic Press, London.

DEPARTMENT OF ZOOLOGY, CLEMSON UNIVERSITY, CLEMSON, SOUTH CAROLINA

29631, 29 AUGUST 1971.

ORIENTATION BEHAVIOR OF NIGHT-MIGRATING
BIRDS (EUROPEAN ROBINS) DURING LATE
AFTERNOON AND EARLY MORNING HOURS

Wolfgang Wiltschko and Hiltrud Hock

IT has been shown previously that European Robins (Erithacus ruhecula)
will orient their nocturnal locomotor activity in Kramer cages in their
natural migratory direction when exposed outdoors to the natural night sky;
and that these directional preferences can be essentially changed by change of
the direction of the magnetic field (Wiltschko, Hock, and Merkel, 1971) . Dur-
ing these experiments the birds’ activity was recorded also during late after-
noon and early morning hours. An analysis of this daytime activity, which
differs in several respects from orientation during darkness, will be presented
in this report. These data are of interest with respect to questions of variation
of directional preference between night and day and with respect to the devel-
opment and deterioration of directional preference before and after nocturnal
migratory activity.

MATERIAL AND METHODS

We used the methods previously described by Wiltschko (1968). The orientation cage
was octagonal, 1 m in diameter and 35 cm high. It contained 8 radially-positioned perches.
Every hop of an experimental bird closed a micro-switch, and caused a signal to be
punched into a paper tape which was processed later by a computer. Food and water were
offered in the center of the cage.

We installed two of these cages in the open air and covered them with plexiglass. With
a pair of Helmholtz coils we made a magnetic field in which the north direction deviated
from geographic north by 115° to ESE, although the intensity and inclination remained
the same as in the earth’s magnetic field (0.47 Gauss, niN = 115°, Inch 68°) (Fig. 1).
We used the earth’s magnetic field (0.47 Gauss, niN =360°, Inch 68°) as a control.

A grey plastic curtain between the Helmholtz coils and the cage prevented the birds
from seeing the coils and the surrounding landmarks. From the center of the cage the
birds had a 53° view of the sky, but when the birds moved to the sides of the cage they
could actually see a 102° sector of the sky. The test installation was located in the Khdn
Mountains, 110 km northeast of Frankfurt a.M.

In both cages the directional preference of European Robins were recorded alternately
in the natural magnetic field (Control) and with the direction of the magnetic field
artificially turned (Test). We used two different groups of robins, 16 as Test birds and
15 as Controls, in order to avoid the possible transfer of effects from lest to Control
conditions.

During the recording period the operator classified sky conditions as ■‘clear” when
there was a cloudless sky; as “{)artly coverc'd” when the sky was partly ohscure'd by cloud>
or when fog came up during a clear period, and as "overcast” when the sk> was compl<‘tel>
covered with clouds or when the sun was invisible because of fog during the entire te^t
period.

149

150

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Fig. 1. Ground plan of the test arrangement: N = geographic north; mN =: magnetic
north when current is switched on; He = Helmholtz coils; ws windscreen.

The tests were made during spring migratory period of 1969, with registration between
dusk and 10:00 of the following day, and in autumn 1969 and spring 1970, with registration
between 16:00 and 10:00 of the following day. The computer provided for a distinction
between evening, night, and morning activity. The directional tendencies (calculated by
computer) of the birds in each period are indicated by the mean direction, a,n, and by
the concentration term, am. The statistical significance of am was examined by the
Rayleigh Test for directional preference, and differences in mean direction were examined
by the Watson and Williams Test (Batschelet, 1965). In the figures the mean directions
for single evenings and mornings are represented by triangles on a circle, and the mean
direction, am, of the test series is shown as a vector originating from the center. The
length of this vector represents the concentration am, and the two inner circles are the
5 per cent (dotted) and the 1 per cent significance borders of the Rayleigh Test.

RESULTS

The data for night activity, which are reported in detail by Wiltschko et al. (1971),
are summarized here briefly as an essential basis for interpreting the records for morning
and afternoon activity in the same birds:

In spring 1969 and 1970 the robins under Control conditions showed a significant
directional preference (p < 0.01) towards 26°, i.e. NNE, whereas the birds under Test
conditions showed a significant preference (p < 0.01) towards 142°, which is geographic
SE, but experimental NNE. In autumn 1969 the Controls showed a mean direction towards
175°, i.e. S, but this direction is not significant (p > 0.05). The birds under Test condi-
tions show a significant directional preference (p<0.01) towards 321°, which is experi-
mental SSW. So in spring as well as in autumn the birds during nighttime selected their
migratory direction according to the direction of the magnetic field.

Activity recorded during late afternoon and evening. — In spring 1969 and
1970, the mean direction of 16 values under Control conditions (i.e. birds

Wiltschko
and Hock

ORIENTATION BEHAVIOR OF NIGHT MIGRANTS

151

s

a

N

b

Fig. 2. Mean directions of activity recorded during late afternoon in spring 1969 and
1970: a. Control; b. Test conditions, mN == 115°.

were tested under the natural sky and the earth’s magnetic field) pointed
towards 360° = N (Fig. 2a) , but this direction was not significant (p > 0.05) .
Under Test conditions (birds were tested under natural sky, but had the
magnetic field turned by 115° to ESE ) the birds showed in 25 evening periods
a significant directional preference (0.05 > p > 0.01) at 337° which is
geographic NNW, but experimental SW (Fig. 2b) .

In autumn 1969 the Control experiments showed again a mean direction of
21 values at NNW at 347° (Fig. 3a), but again this directional tendency was
not significant (p > 0.05) ; whereas under Test conditions we found for 33
values a significant directional preference (p<0.01) at 331° = geographic
NNW = experimental SW (Fig. 3b) .

a b

Fig. 3. Mean directions of activity recorded during late aft<*rnoon in autumn 1969:
a. Control; b. Test conditions, mN = 115°.

152

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Table

The Effect of Weather Conditions on
During Evening

1

Directions

Activity

Preferred by

Robins

Control

Test

n am p

n

ftni

p

clear:

spring:

3

29°

—

3

274°

—

autumn:

9

15°

—

16

320°

(p<0.01)

spring and autumn:

12

18°

( p > 0.05)

19

313°

(p<0.01)

partly covered:

spring:

7

320°

—

13

5°

(0.05 >p> 0.01)

autumn:

7

10°

—

10

334°

( p < 0.01 )

spring and autumn:

14

360°

(p > 0.05)

23

349°

(p < 0.01)

overcast:

spring:

6

357°

—

9

298°

—

autumn:

5

265°

—

7

353°

—

spring and autumn:

11

305°

( p > 0.05)

16

330°

(p>0.05)

The foregoing data show that the mean direction of orientation in robins
in evening points towards the geographic NNW sector in both spring and
autumn and in either Test or Control conditions. We do not find any statisti-
cally significant differences (Watson and Williams Test) in directional pref-
erences between spring and autumn for either Test or Control conditions. We
are therefore justified in combining data for spring and autumn, in which
case we find a significant directional preference ( p <0.01 1 towards 333° for
Test and a significant directional preference I 0.05 > p > 0.01 ) towards 352°
for Control.

On the other hand the Watson and Williams Test does not allow us to as-
sume that the mean directions of Test and Control experiments originate from
different statistical populations; the only difference is that under Test condi-
tions the directional preference is in both seasons more concentrated than
under Control conditions.

We may next examine the effect of different weather conditions on direc-
tions preferred by the robins, with results summarized in Table 1. Here again
we cannot find significant differences between the mean directions for any
weather conditions, nor can we, for any weather condition, find a difference
between Test and Control.

If we classify the test values of evening activity according to whether the
birds showed migratory activity (Zugunruhe) during the following night,
we obtain the results shown in Table 2. We again cannot find any significant
differences.

ORIENTATION BEHAVIOR OF NIGHT MIGRANTS 153

Table 2

Directions Preferred by Robins During Evening Activity

Control

Test

n

(Vni

p

n

tt'm

V

followed by migratory activity:

spring;

13

10°

(p > 0.05)

13

314°

(0.05 >p> 0.01)

autumn:

16

347°

(p > 0.05)

18

319°

(p<0.01)

spring and autumn:

29

360°

( p > 0.05)

31

317°

(p<0.01)

not followed by migratory activity:

spring;

3

323°

—

12

20°

(p>0.05)

autumn:

5

346°

—

15

348°

ip <0.0l)

spring and autumn:

8

342°

(0.05 > p >0.01)

27

357°

(p < 0.01)

Activity recorded during the morning hours. — ^In spring we found a mean
direction of 44° = NE for 36 Control values and one of 56° = geographic NE
= experimental WNW for 42 Test values. The directional preference was
significant for Control (p<0.01), but not significant for Test (p>0.05).
In autumn the mean direction of 20 Control values pointed towards 307° =
NW, the mean direction of 32 Tests towards 311° = geographic NW = experi-
mental SSW. This time the birds’ behavior produced a significant directional
preference (p<0.01) under Test conditions, whereas for Control we got
random movements (p > 0.05 ) .

But if we now classify these values according to whether the birds had shown
migratory activity during the night before, we obtain the results shown in
Table 3. It is obvious that the mean direction of morning activity following

Table 3

Directions Preferred by Robins During Morning Activity

Control

Test

n fVni

P

n

(Ym

P

following migratory activity:

spring:

30 34°

( p < 0.01 )

25

128°

{ p > 0.05)

autumn :

15 232°

(p > 0.05)

16

295°

(0.05 > p > 0.01 »

spring +

(autumn + 180° ) :

45 34°

(p <0.01 )

11

120°

(0.05 > p > 0.0 1 I

not following migratory activity:

spring:

6 1 34°

—

17

22°

(p <0.01)

autumn :

5 320°

—

16

.342°

( p > 0.05)

154

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

▲ Spring
A Autumn +180®

Fig, 4. Mean directions of morning activity -when the birds had shown migratory- rest-
lessness the night before: dark triangles: data of spring 1969 and 1970; light triangles:
data of autumn 1969 turned to the opposite side by adding 180°. a. Control; b. Test
conditions, mN 115°.

nocturnal activity correspond to the mean directions of this nocturnal activity,
although the dispersion of data is larger than at night. The Watson and
Williams Test does not show a difference between the direction of night activ-
ity and morning activity for any set of values. If we assume that the birds re-
turn in spring using about the same route they used in autumn and that there-
fore the migratory directions in spring and autumn lie opposite, we can combine
the data of both seasons by turning the autumn data to the opposite side by
adding 180°. We now find significant mean directions at 34° = NNE for Con-

s

a

A Spring
A Autumn

Fig. 5. Mean directions of morning activity not preceded by nocturnal acti\ity : dark
triangles: data of spring 1969 and 1970; light triangles: data of autumn 1969. a. Control;
b. Test conditions, mN = 115°.

wiitschko ORIENTATION BEHAVIOR OE NIGHT MIGRANTS 155

and Hock

Table 4

Effect of Weather Conditions on Directions Preferred by Robins on
Mornings after Nighttime Zugunruhe

Control

Test

n

rvm

V

n

Om

P

clear and partly covered.
spring:

15

49°

(0.05 > p >0.01)

8

147°

autumn:

7

65°

—

4

239°

—

spring -f-

(autumn + 180°) :

22

47°

(p>0.05)

12

91°

(p>0.05)

overcast:

spring:

15

19°

(0.05>p >0.01)

17

120°

(p > 0.05)

autumn :

8

238°

—

12

312°

(0.05 >p >0.01)

spring +

(autumn -f- 180° ) :

23

24°

(0.05 >p> 0.01)

29

127°

(0.05 >p> 0.01)

trol (Fig. 4a) (p<0.01) and at 120° = geographic ESE = experimental N
for Test (Fig. 4b) (0.05 > p > 0.01). The fact that these mean directions in
Test and Control originate from different statistical populations is significant
with p < 0.01.

On the other hand the data of morning activity not preceded by migratory
activity show no relation to the directions the same birds selected when they
showed migratory restlessness (Fig. 5) .

Different weather conditions did not cause significant differences in birds’
directional behavior recorded during mornings after Zugunruhe (Table 4).

The mean directions of evening, night, and morning activity of single regis-
tration periods are given in Tables in the Appendix.

DISCUSSION

When we started to register daytime activity we wanted to find out whether
in the migratory season night-migrating birds have a tendency to move in
their migratory direction also during the daytime periods before and after
darkness. The direction selected during early morning hours corresponds
with the migratory direction, hut only when the birds were actually restless
the night before. The concentration of these directional preferences is lower
than the concentration found during nighttime. This may result from both llic
shorter registration time (3-5 hours, compared with D-1 1 hours during
nights) and a weaker motivation to keep the migratory course. I hese findings
correspond with those of Mewaldt et al. (1961). who found that pre-dawn
migratory restlessness may persist into the post-dawn period. Mewaldt et al.

156

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

found these tendencies with Zonotrichia only in autumn, whereas our robins
showed this behavior also in spring. This may be merely an interspecific
difference.

We cannot state exactly whether the directional preference during morning
hours depends on the directional preference during night. The fact that in
more than 50 per cent of all experiments the birds selected during morning
hours a direction deviating more than 45° from the one they had selected the
night before indicates that the birds might select their migratory direction
anew. This is also supported by the observation that in most experiments
there is a period of low activity or no activity between the night activity and
the morning activity peak.

The experiments in our Test arrangement give evidence that the selection
of the migratory direction is dependent on the magnetic field also during
daylight hours. Most data for Test conditions were obtained during “overcast”
morning periods when the sun was not visible; but on “partly covered” morn-
ings the birds’ orientation behavior might have been influenced by the sun
compass. The robins were unable to see the sun itself because of the plastic
curtain that concealed the Helmholtz coils and surrounding landmarks, but
they may have got information of the sun’s position by lighted clouds or
lighter parts of the sky. Unfortunately we have only very few values for
“partly covered” Test mornings: the seven values obtained in spring cannot
be interpreted as evidence for the use of a sun compass, since their mean
direction (statistically nonsignificant) corresponds to the migratory direction
according to the magnetic field. In autumn the mean direction points towards
SW as expected for sun compass orientation, but it is based on only four
values. So we need more data to decide under which conditions the birds use
the sun compass, and how they select their migratory direction when sun com-
pass and magnetic compass give conflicting information.

The orientation of morning activity following nights without nocturnal
restlessness seems to have no relation to the migratory direction.

The activity recorded during late afternoon and evening shows an orienta-
tion towards the NNW sector, which seems similar to the “nonsense” orienta-
tion of released non-migrating Mallards, described by Matthews ( 1961) . This
orientation in robins does not depend on the direction of the magnetic field,
does not alter between spring and autumn, and shows no relation to the migra-
tory direction (except in Test in autumn, where by chance this “nonsense”
direction and the migratory direction coincide ) . But this “nonsense” orienta-
tion, unlike the one described by Matthews (1963) is independent of the
weather condition and seems to persist under total overcast. We do not think
that this direction is caused by phototaxis from the setting sun, since (1) the
mean is too far north from the sunset point, (2) it persists under total over-

ORIENTATION BEHAVIOR OF NIGHT MIGRANTS 157

cast, and (3) the morning activity not preceded by nocturnal activity shows
no corresponding eastward direction. A simple explanation could be that the
door of the windscreen was in the SE, and so the birds were released from this
side into the cage (Fig. 1). NNW is the direction where they try to escape
from the operator, and hence may be temporarily fixed in the behavior pat-
tern. In spring as well as in autumn this “nonsense’' orientation is much more
concentrated under Test conditions. The reason may be that under Test condi-
tions the birds’ motivation to prefer this direction is intensified by the fact
that it coincides with the axial migratory direction. It is not surprising that
the direction opposite to the migratory direction (situation in spring experi-
ments) has a certain prominence for a bird, since we know from the magnetic
compass that in the first step the bird perceives only the axial direction of the
magnetic field lines (Wiltschko 1971).

Maybe we can interpret the data of morning activity not preceded by noc-
turnal activity (except for the four values of Control in spring ) as an expres-
sion of a similar “nonsense” tendency. This tendency is much weaker than in
the evening, as might be expected, since the birds had 13-15 hours to forget
the procedure of being caught and brought into the registration cage.

SUMMARY

1. The birds’ activity during early morning hours is concentrated in migratory direction,
but only when the birds showed migratory activity in the night before.

2. When the magnetic field was artificially changed (magnetic north at 115° in ESE),
the birds during morning hours selected their migratory direction according to the
direction of the magnetic field.

3. The birds’ behavior during late afternoon and evening shows a “nonsense orientation'’
towards the geographic NNW sector in Test (magnetic north in ESE) and Control
(earth’s magnetic field) in spring as well as in autumn.

4. This “nonsense orientation” seems to persist under clear, partly covered and overcast
skies, and might be explained as a temporarily fixed part in the birds’ behavior
pattern caused by carrying the birds into the cage from the opposite side.

ACKNOW^LEDGMENTS

The work was supported by the Deutsche Forschungsgemeinschaft. We gratefully
acknowledge the help of Dr. W. Schuckmann and Mr. K. 1). Klein for the computer
program and of Prof. J. R. King for critically reading the manuscript. Special thanks to
Mr. and Mrs. Henkel, Ufhausen, Rhdn mountains, who permitted us to use their garden
for installing our test arrangement, and to Prof. F. W. Merkel for many useful dis-
cussions.

APPENDIX (TABLES 5 10)

The tables give the mean direction of afternoon and evening-, night-, and morning
activity for the single registration periods between 10:00 and 10:00 the following da>.

158

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

^ e evaluated every afternoon- and morning activity period in which the bird did more
than 50 hops and every night activity period with more than 70 hops.

During spring 1969 afternoon and evening activity w^as not registered, registration time
started at dusk. In a few cases when the entire activity of that night (more than 70 hops)
occurred during the first hour, it is considered as evening activity rather than night activity
and given as “afternoon” activity in the tables. Also in spring 1969 the morning activity
had to be registered separately and could not be registered regularly. The mornings,
when no morning activity was registered, are marked as “not reg.” in the tables. “Techn.
defect” means that the bird showed activity, but this activity could not be evaluated
because of a defect in the recording system. The letters refer to weather conditions:
cl = clear; pc partly covered; ov nr overcast.

Table 5

Spring 1%9, Control

Date

Bird

Afternoon

Night

Morning

5 April

R 3

—

cl 360°

not reg.

6 April

R 3

—

cl 131°

not reg.

9 April

R 3

—

cl 200°

not reg.

11 April

R 3

—

ov 338°

cl 1°

12 April

R 7

—

pc 18°

—

13 April

R 6

—

—

pc 22°

14 April

R 3

pc 105°

—

pc 160°

17 April

R 12

—

ov 358°

—

18 April

R 3

—

—

ov 154°

19 April

R 9

cl 293°

—

cl 193°

20 April

R 12

—

pc 233°

pc 227°

23 April

R 9

—

ov 34R°

—

24 April

R 12

—

ov 139°

—

25 April

R 8

—

pc 125°

pc 42°

26 April

R 4

—

ov 326°

pc 23°

27 April

R 10

—

pc 21°

ov 5°

1 May

R 9

—

ov 66°

not reg.

3 May

R 12

—

pc 234°

ov 5°

4 May

R 9

—

ov 38°

pc 56°

6 May

R 12

—

ov 359°

ov 23°

7 May

R 9

—

ov 17°

ov 305°

9 May

R 12

—

pc 235°

ov 87°

10 May

R 9

—

pc 315°

—

11 May

R 12

—

cl 301°

cl 75°

12 May

R 21

—

cl 26°

pc 40°

14 May-

R 12

—

ov 267°

pc 256°

16 May-

R 12

—

pc 352°

not reg.

20 May-

R 12

—

ov 35°

not reg.

21 May

R 15

—

ov 19°

not reg.

wiitschko ORIENTATION BEHAVIOR OF NIGHT MIGRANTS 159

and Hock '

Table 6
Spring 1969, Test

Date

Bird

Afternoon

Night

Morning

4

April

R

2

—

—

cl

218°

5

April

R

2

cl 200°

—

cl

117°

8

April

R

4

—

cl 180°

not

reg.

10

April

R

4

—

—

ov

301°

12

April

R

8

—

—

pc

57°

13

April

R

4

pc 357°

—

pc

355°

14

April

R

2

—

pc 116°

16

April

R

4

—

—

ov

37°

20

April

R

10

—

cl 171°

pc

205°

21

April

R

8

—

ov 159°

ov

172°

22

April

R

2

—

ov 229°

ov

77°

23

April

R

4

—

ov 186°

ov

153°

24

April

R

10

—

ov 166°

not

reg.

25

April

R

7

—

pc 215°

26

April

R

9

—

ov 359°

27

April

R

12

—

ov 153°

ov

130°

28

April

R

8

—

ov 109°

ov

192°

29

April

R

4

—

ov 102°

ov

282°

30

April

R

10

—

ov 70°

ov

110°

3

May

R

10

—

pc 207°

ov

329°

4

May

R

4

—

ov 215°

pc

151°

5

May

R

19

—

pc 239°

—

6

May

R

10

—

ov 41°

ov

112°

7

May

R

4

—

ov 78°

ov

80°

8

May

R

19

—

ov 194°

—

10

May

R

4

—

pc 71°

ov

95°

12

May

R

4

—

pc 252°

pc

261°

13

May

R

13

—

cl 17°

pc

91°

14

May

R

10

—

pc 7°

—

16

May

R

10

—

pc 39°

not

reg.

18

May

R

13

—

pc 89°

not

reg.

19

May

R

18

pc 248°

—

ov

31°

21

May

R

13

—

pc 155°

not

; reg.

Table 7

Autumn 1%9, Control

Date

Bird

Afternoon

Night

Morning

13 September

R 27

cl 64°

cl 181°

pc 75°

14 September

R 22

cl 308°

—

pc 315°

16 September

R 27

ov 265°

ov 218'

ov 249°

160

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

TABLE 7
Continued

Date

Bird

Afternoon

Night

Morning

19 September

R 27

cl 53°

pc 20°

pc 349°

20 September

R 22

cl 11°

cl 195°

pc 37°

22 September

R 27

pc 161°

pc 17°

pc 64°

23 September

R 22

cl 225°

techn. defect

techn. defect

24 September

R 27

cl 108°

pc 122°

ov 231°

25 September

R 32

pc 29°

—

ov 335°

27 September

R 22

pc 360°

pc 279°

ov 161°

30 September

R 22

pc 67°

ov 130°

ov 33°

1 October

R 27

pc 273°

pc M7°

ov 310°

2 October

R 32

ov 325°

—

ov 338°

4 October

R 22

cl 327°

pc 194°

ov 49°

7 October

R 22

pc 8°

—

ov 267°

9 October

R 27

cl 37°

pc 30°

ov 259°

11 October

R 32

cl 342°

—

pc 329°

16 October

R 27

ov 284°

ov 118°

pc 235°

23 October

R 27

ov 173°

ov 175°

ov 142°

26 October

R 27

ov 255°

pc 282°

pc 228°

4 November

R 27

pc 342°

ov 186°

pc 190°

Table 8

Autumn 1969, Test

Date

Bird

Afternoon

Night

Morning

13 September

R 28

cl 286°

—

pc 108°

15 September

R 26

ov 19°

—

—

16 September

R 28

ov 47°

—

ov 236°

17 September

R 23

-

—

ov 326°

18 September

R 26

cl 34°

—

cl 107°

19 September

R 28

cl 242°

techn. defect

techn. defect

21 September

R 23

—

—

ov 298°

22 September

R 28

pc 19°

pc 257°

pc 237°

23 September

R 26

cl 326°

pc 341°

ov 308°

24 September

R 28

cl 12°

pc 24°

ov 273°

25 September

R 29

pc 328°

ov 328°

ov 311°

28 September

R 28

cl 335°

cl 305°

pc 327°

29 September

R 29

ov 81°

—

ov 81°

30 September

R 26

pc 6°

ov 2°

ov 7°

1 October

R 28

pc 360°

—

ov 12°

2 October

R 29

ov 322°

—

ov 307°

5 October

R 28

cl 5°

pc 16°

ov 23°

6 October

R 29

pc 15°

—

ov 339°

Wiitschko ORIENTATION BEHAVIOR OF NIGHT MIGRANTS

161

TABLE 8
Continued

Date

Bird

Afternoon

Night

Morning

9 October

R 28

cl 189°

pc 193°

OV 225°

11 October

R 29

cl 230°

—

pc 171°

13 October

R 28

cl 345°

—

ov 9°

15 October

R 34

cl 301°

—

ov 298°

16 October

R 28

ov 350°

—

ov 47°

17 October

R 29

cl 24°

—

ov 169°

19 October

R 28

cl 348°

pc 350°

ov 60°

20 October

R 29

cl 285°

cl 254°

cl 237°

21 October

R 34

cl 283°

pc 343°

ov 275°

22 October

R 28

pc 344°

pc 299°

techn. defect

23 October

R 29

ov 294°

ov 335°

ov 236°

28 October

R 29

pc 283°

pc 240°

pc 169°

29 October

R 28

pc 296°

—

ov 288°

30 October

R 34

pc 297°

ov 278°

ov 294°

1 November

R 28

cl 324°

cl 62°

—

2 November

R 34

—

pc 213°

ov 14°

3 November

R 29

ov 294°

ov 31°

ov 310°

4 November

R 28

pc 312°

—

pc 334°

Table 9

Spring 1970, Control

Date Bird Afternoon Night Morning

16

April

R

49

—

—

pc

39-

17

April

R

46

pc 263°

pc

47°

pc

237'

18

April

R

43

ov 210°

ov

126°

ov

110'

20

April

R

46

pc 83°

pc

17°

pc

46'

21

April

R

43

pc 14°

ov

46°

ov

69'

22

April

R

49

—

ov

338°

—

23

April

R

46

ov 356°

pc

227°

ov

82'

24

April

R

43

—

pc

100°

ov

21'

26

April

R

46

ov 87°

ov

295°

ov

272'

27

April

R

43

pc 351°

pc

U°

pc

46)'

28

April

R

49

—

pc

IT

—

29

April

R

46

pc 254°

pc

3,32°

ov

331'

30

April

R

43

ov 316°

ov

150'

1

May

R

49

—

pc

70°

—

2

May-

R

46

—

ov

26°

ov

47'

3

May

R

43

ov 341°

ov

60°

ov

276'

4

May

R

49

—

ov

327°

5

May

R

46

pc 222°

pc

71°

pc

71'

162

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

TABLE 9
Continued

Date

Bird

Afternoon

Night

Morning

6 May

R 43

—

pc 76°

pc 57°

7 May

R 46

cl 93°

pc 106°

pc 118°

9 May

R 53

cl 35°

pc 183°

pc 53°

10 May

R 43

ov 31°

ov 33°

ov 322°

11 May

R A6

—

pc 116°

ov 66°

Table 10
Spring 1970, Test

Date

Bird

Afternoon

Night

Morning

17 April

R 44

pc 42°

pc 324°

pc 271°

18 April

R 41

pc 17°

—

ov 26°

19 April

R 40

ov 61°

—

ov 66°

20 April

R 44

pc 1°

pc 101°

pc 113°

21 April

R 41

ov 314°

ov 50°

ov 315°

22 April

R 40

ov 307°

ov 257°

—

23 April

R 44

ov 294°

pc 322°

ov 48°

24 April

R 41

pc 338°

pc 199°

—

25 April

R 40

pc 99°

—

ov 18°

26 April

R 44

ov 214°

ov 176°

ov 326°

27 April

R 41

pc 16°

pc 150°

—

28 April

R 40

pc 7°

—

pc 335°

29 April

R 44

pc 96°

pc 96°

ov 117°

30 April

R 41

ov 293°

—

ov 318°

1 May

R 40

pc 32°

pc 53°

2 May

R 44

pc 269°

ov 150°

ov 270°

3 May

R 41

ov 265°

ov 123°

ov 192°

4 May

R 40

cl 336°

—

pc 271°

5 May

R 44

pc 299°

pc 260°

pc 348°

6 May

R 41

—

—

pc 10°

7 May

R 44

—

pc 101°

pc 81°

9 May

R 40

cl 284°

pc 133°

—

11 May

R 44

ov 46°

—

ov 51°

12 May

R 40

ov 148°

—

ov 77°

LITERATURE CITED

Batschelet, E. 1965. Statistical methods for the analysis of problems in animal orienta-
tion and certain biological rhythms. A.I.B.S., Washington, D.C.

Matthews, G. V. T. 1961. “Nonsense” orientation in Mallard (Anas platyrhynchos)
and its relation to experiments on bird navigation. Ibis, 103a:211-230.

Wiitschko ORIENTATION BEHAVIOR OE NIGHT MIGRANTS 163

Matthews, G. V. T. 1963. The astronomical basis of “nonsense” orientation. Proc.
13th Intematl. Ornithol. Cong.: 415-429.

Mewaldt, L. R., M. L. Morton, and I, L. Brown. 1964. Orientation of migratory rest-
lessness in Zonotrichia. Condor, 66:377-417.

WiLTSCHKO, W. 1968. tiber den EinfluB statischer Magnetfelder auf die Zugorientierung
der Rotkehlchen (Erithacus rubecula) . Z. Tierpsychol. 25:537-558.

WiLTSCHKO, W. 1971. The influence of magnetic total intensity and inclination on
directions preferred by migrating European Robins i Erithacus rubecula). Proc. of
the A.I.B.S. Symposium on Animal Orientation and Navigation. Wallop’s Island,
Virginia 1970. In press.

WiLTSCHKO, W., H. Hock, and F. W. Merkel. 1971. Outdoor experiments with mi-
grating robins (Erithacus rubecula) in artificial magnetic fields. Z. Tierpsychol. 29:
409-415.

ZOOLOGISCHES INSTITUT DER UNIVERSITAT, 6 FRANKFURT AM MAIN, GERMANY,

2 JUNE 1971.

NEW LIFE MEMBER

A recent addition to the roster of Life
Members of the Wilson Society is Robert
L. Haines, of Moorestown, New Jersey. Mr.
Haines, who has retired from a family paint
and glass business, now spends his time in
pursuing his ornithological interests, and
is active in several organizations concerned
with the welfare of the American Indians.
He is in fact an adopted member of the
Seneca tribe. A graduate of Haverford
College, Mr. Haines has carried out serious
studies of birds and has published several
papers. He has been a member of the
Society for 25 years, and is also a member
of the AOU, the Cooper Society, The
National and New Jersey Audubon Society,
and the Delaware Valley Ornithological
Club, having served as president of the
latter in 1950. He is married and lias two
children and two grandchildren.

DIURNAL AND SEASONAL ACTIVITIES OF A
POST-BREEDING POPULATION OF GULLS IN
SOUTHEASTERN ONTARIO

F. Cooke and R. K. Ross

Although the breeding biology of the Herring Gull has been extensively
studied, the post-breeding activities are less well understood. The
Herring Gull undertakes an explosive post-breeding dispersal with direction
influenced to some extent by prevailing winds and by the tendency of the
birds to follow waterways or coasts. Gross (1940) noted that few of the
gulls banded at Kent Island, New Brunswick moved inland and most moved
southward. Poor (1943) reported similar findings from colonies in the Gulf
of St. Lawrence. Banding data from gulls breeding around Lake Michigan in-
dicated a predominantly easterly post-breeding movement along the Great
Lakes-St. Lawrence system which was attributed to the prevailing winds
(Smith, 1959). Young birds tended to disperse more widely than adults.
Kadlec and Drury (1968 ) reported extensive data on the distribution of winter
banding recoveries of Herring Gulls in relationship to the areas in which the
birds were banded.

Schreiber (1968) carried out a study of gull numbers at Bangor, 35 miles
northwest of the Maine coastline. He was able to correlate numbers of birds
with cloud cover. Clear days were associated with northwest winds which
were thought to drive the gulls towards the coast, while the overcast days
usually with little wind allowed numbers to increase as the gulls returned.

In the present study we made daily observations on a flock of gulls which
congregate daily on the Kingston (Ontario) City Dump during the fall and
early winter. Usually around 95 per cent of this fall flock consisted of Herring
Gulls (Larus argentatus) . During September, however. Ring-billed Gulls
(Larus delawarensis) comprised up to 40 per cent of the flock but after
September, only very small numbers of this species were present. The Great
Black-backed Gull {Larus marinus) ^ the Glaucous Gull {Larus hyperboreus) ,
and the Iceland Gull {Larus glaucoides) also occur in extremely small num-
bers, the last two only late in the fall.

The primary aim of this project was to investigate the factors responsible
for the daily fluctuations in flock size and for the eventual disappearance of
the flock from the Kingston area in early winter. A study in the Kingston
area (see Fig. 1 ), lying midway between tbe other major areas where Herring
Gulls had been studied, would add to an understanding of the continental
dispersion pattern of this species.

164

Cooke and
Ross

GULL POST-BREEDING ACTIVITIES

165

METHODS

We made observations from 22 September 1968 to 22 December 1%8 and from 22
September 1969 to 10 December 1969. Less regular observations were made in January
1969. In the first season of study we made daily observations at gull concentration areas
in the Kingston area. The major area studied was the Kingston City Dump which is the
principal feeding site for the gull population. Numbers at this site remained essentially
constant between 10:00 and 14:00 each day and we made daily gull counts during this
time interval throughout both seas..ns. With larger flocks, estimates were made.

Weather records were obtained from the Kingston Weather Office, which is located
seven miles southwest of the main study area. Weather conditions at 08:00 were used
in the tables. The location of the actual roosts in Lake Ontario were found by spotting
from the shore and by aerial survey in the late afternoon.

DAILY MOVEMENTS AND BEHAVIOR

The morning feeding flight. — The first of the gulls’ daily movements was
the flight from the roosting area on Lake Ontario and the islands to the
feeding area, i.e. the Kingston City Dumj) (see FTg. 1). I his started just
before sunrise and continued over a period of three to four hours. Incoming
birds were constantly visible throughout this period, coming in singly or in

]66

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

P7u:quency of

Table 1

Feeding in Samples of Two Age Groups of Herring Gulls

Date

Time

Loafing;

Feeding

1st & 2nd

3rd & Adult

1st & 2nd

3rd

& Adult

18 November 1969

13:00

40

245

47

80

16 September 1970

13:00

16

188

18

15

17 September 1970

11:30

11

78

6

12

20 October 1970

13:30

32

453

33

67

Total

99

964

104

174

small groups. During the peak movements which occurred in the middle of
the period, these groups increased in size ( up to 30-40 ) . The groups were
not very cohesive and splitting often occurred. The method of flight de-
pended on wind direction and speed although in all cases it was fairly direct
with little circling and chasing of one another. Major directions of flight are
shown in Figure 1. The easterly route between the Simcoe Island roost and
the City Dump was the most used.

Arrival in the feeding area. — On arrival in the dump vicinity, the gulls
initially congregated south of the feeding area. They were active at this time.
After a build-up in numbers to several hundred, the birds began moving onto
the actual dumping area. The first sorties often involved a simple circling
of the area and a return to the south bay. This was soon followed by actual
landing in the dumping area.

Feeding. — Feeding activity varied throughout the day from a complete
cessation to a frenzy of hundreds of birds swirling around the garbage piles.
Periods of feeding activity could last for up to half an hour after which most
of the birds returned to the loafing areas. There was a tendency to move to
water after these sessions and drinking was observed. Schreiber ( 1967 1
noted a definite requirement for a supply of fresh water near the feeding
area.

The age classes of the Herring Gulls were determined following Dwight
(1925). On each of four sample counts it was found that there were a sig-
nificantly higher proportion of first and second year birds in the feeding
groups than were found in the loafing groups (see Table 1). A Chi square
value of 534.9 ( P < 0.001 ) was obtained. The presence of larger numbers
of younger birds on the garbage pile suggests that they spend more time
feeding than do older birds. This could be due to lack of dominance and
youthful inexperience in food procuring. Drury and Smith ( 1968 1 found
a definite dominance of adults over younger birds. Immature Herring Gulls

Cooke and
Ross

GULL POST-BREEDING ACTIVITIES

167

were never observed chasing adults with food although the converse was
frequently seen. It seems likely that immature birds would have to remain
longer on the garbage pits to meet their nutritional requirements and so would
tend to be concentrated in this area.

Loafing. — The birds spend much of the time loafing while in the general
area of the dump. Loafing gulls stood or sat in groups. Very little preening
activity was observed. Regular commuting between feeding and loafing areas
occurred. In the early fall loafing groups could be found in the water of the
south bay, along its shores, and on the flat open land around the dump. Gulls
rarely loafed on the weedy water of the north bay. Later in the year, how-
ever, this section was the first frozen and the north bay became the preferred
loafing area. Birds loafed both on the ice and in the water near the ice.

Swarm circling. — A flock of gulls often would rise in a compact swarm,
circling presumably on a thermal upcurrent. The birds would go almost out
of sight (around 3000 feet) and then return very quickly in a steep glide,
approaching a dive. This is thought to be a defensive mechanism ( Tinbergen,
1953) which might confuse or even intimidate an attacking predator. The
passage of a low flying helicopter, the explosive launching of a cannon net
and appearance of a Rough-legged Hawk all appeared, on occasion, to trigger
the circling. At other times, however, the behavior was observed with no
visible fright stimulus associated with it.

The roosting flight. — Roughly three hours before sunset, a large flock
developed beside the dump, usually on water, and feeding activity decreased.
After a period of “nervousness” involving chasing, preening, and quick
circling, also noted by Schreiber (1967), the birds left singly or in small
groups, retracing the morning route to the roosts.

Most birds roosted on the sheltered water northeast of Simcoe Island al-
though some also roosted on Salmon Island. As the estimates of roosting
gull numbers were consistently less than the total daily numbers, it is pre-
sumed that other roosts existed.

DAILY NUMBERS OF GULLS AND ENVIRONMENTAL CONDITIONS

Food supply. — The Kingston Gity Dump is operated as a sanitary landfill
operation, with food refuse being covered with earth soon after it is dumped.
Dumping is carried out daily from Monday to Saturday with no significant
variations in amounts trucked in from day to day. On Sundays, however,
there is no dumping and little edible material remains on the surface from
the previous day, and considerably fewer birds visit the feeding area. The
average of 19 Sunday counts was 678 and for 137 week-day counts was
1382. The Sunday average is 19 jhu- cent of the week-day average. 1lie

168

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Possoge of worm front

A- NOVEMBER 26 -DECEMBER 10,1968 |

{ Possoge of cold front

Fig. 2. Relationship between weather fronts and daily number of gulls.

counts were made around noon. On Sundays, the birds arrived as normal
in the morning but left the feeding area, some to the loafing areas and others
away from the vicinity of the dump altogether. We suspect that the whole
flock initially came but dispersed on finding no food.

Weather conditions. — During the week, when there was adequate food on
the dump, the numbers still fluctuated. A decrease in temperature and an in-
crease in barometric pressure both tended to signal a decrease in gull numbers.

Cooke and
Ross

GULL POST-BREEDING ACTIVITIES

169

Table 2

Relationship between Gull Numbers

AND Weather Fronts

Final Day

of

Final Day of

Warm Front I:

nterval

Cold Front Interval

Date

Count

Date

Count

1968

26 September

715

27 September

640

8 October

1010

10 October

1352

18 October

1643

21 October

1081

23 October

2011

26 October

1439

28 October

1266

1 November

1177

2 November

1606

4 November

1640

15 November

2325

16 November

2150

22 November

3784

26 November

1658

28 November

2395

30 November

1950

5 December

3429

10 December

1321

12 December

2710

16 December

324

18 December

2296

20 December

35

1969

18 October

2030

21 October

1146

24 October

2674

29 October

1183

31 October

2338

4 November

2370

6 November

1495

12 November

800

18 November

1945

20 November

1222

22 November

2320

26 November

1865

28 November

1915

1 December

700

3 December

1400

5 December

1350

and so an attempt was made to correlate the numbers and the passage of warm
and cold fronts. Figure 2 provides examples of two sample periods. Generally
the numbers increased during the period between the passage of a warm front
and the arrival of the associated cold front ( hereafter, warm front interval ) .
Conversely, numbers decreased after the cold front and before the next warm
front (hereafter, cold front interval). Table 2 presents the counts on the
final day of both the warm and cold front intervals throughout the two
seasons of observation. The final-day counts were chosen as they demonstrated
the maximum effect of that weather interval. Using the Wilcoxon matched-
pairs signed ranks test (Siegel, 1956), we found that the decrease of gull
numbers at the end of the cold front interval as compared to the previous
warm front interval count was significant at the 0.02 level. Sunday counts
were omitted.

Although trends of changes in ])opulation size are evident, the absolute
numbers of gulls cannot be accurately predicted from this knowledge* of
weather conditions. The actual effect of these conditions on the gulls is still

170

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Table

3

Mean

Weekly Counts of Gulls in 1968 and

1969

1968

1969

Week Ending

Mean Count

Week Ending

Mean Count

28 September

496

27 September

542

5 October

1320

4 October

402

12 October

971

11 October

592

19 October

1210

18 October

1059

26 October

1377

25 October

1632

2 November

1354

1 November

1741

9 November

1457

8 November

1439

16 November

1919

15 November

1099

23 November

2844

22 November

1608

30 November

1809

29 November

1834

7 December

2399

6 December

1060

14 December

2154

13 December

210

21 December

823

28 December

155

unexplained. Associated with those periods after warm fronts are increased
temperatures, decreased barometric pressure and a veering of the wind to the
southwest. After a cold front comes decreased temperature, increased pres-
sure and a wind change to the north. All these parameters not only correlate
with the gull numbers but also correlate with one another and so it is im-
possible to analyze which, if any, of the individual factors affects the birds.
It seems likely, however, that wind direction and speed play a major role.
Southwest winds reach Kingston from Lake Ontario and might aid flight
of birds to Kingston from other urban areas around the lake.

Fright stimulus. — A cannon net was discharged within a large loafing flock
on 30 September 1969 catching 65 gulls. Although 1000 gulls were present
on that day, only 190 were seen the next day and not until eight days later
were numbers back to their previous level. Since the passage of weather
systems was not involved, it is felt that the fright stimulus of the trapping
activities was sufficiently strong to deter many birds from returning for some
time.

WEEKLY AND SEASONAL VARIATION IN FLOCK SIZE

There was a progressive rise in numbers as the season proceeeded (Table
3). The initial rise was found highly significant in both years iP — 0.00011
in 1968 and P — 0.0046 in 1969, Kendall rank correlation test). In both
years, the rise ended in late November or early December. Numbers then

Cooke and
Ross

GULL POST-BREEDING AGTIVITIES

171

decreased and great fluctuations occurred. As Lake Ontario began to freeze
around Kingston, gulls were no longer seen daily on the dump and only
periodical appearances, correlated with the passage of warm fronts, were made.
Freeze-up took place during the first week of January in the two years, and
by the middle of the month, gulls were seen only sporadically in very small
numbers. This relative absence of gulls may have been caused by the lack
of drinking water in the vicinity of the garbage dump. The nearest open
water area was miles from the feeding area.

The initial, gradual rise of numbers in the fall can be explained if the
general Herring Gull population of Lake Ontario increased during that time.
This could be due to Herring Gulls moving east from the western Great Lakes
as reported by Smith (1959) and Hofslund (1959 ). In the fall of 1968, J. B.
Steeves (pers. comm.) also found an increase in Herring Gull numbers in
Montreal which peaked a week after the counts in Kingston. This may indicate
that gulls, after initially increasing in numbers in eastern Lake Ontario, move
down the St. Lawrence River to Montreal. Gross (1940) found little post
breeding movement up the St. Lawrence River. Similarly, Poor (1943)
showed that Herring Gulls breeding in the Gulf of St. Lawrence almost never
moved towards Montreal, and instead dispersed to the Atlantic. This, there-
fore, leaves the Great Lakes and Upper St. Lawrence region with its large gull
population as the most likely contributor of gulls to the Montreal flock.

SUMMARY

The activities of a flock of gulls, which congregated daily to feed on the Kingston
City Dump were studied in order to investigate the factors leading to the daily and seasonal
fluctuations in flock size.

The daily numbers of gulls on the dump were found to be influenced by food supply,
severe fright stimulus, availability of water, and weather. The period after a warm front
was associated with an increase in numbers while that after a cold front was usually
associated with a decrease.

First and second year gulls were found to spend considerable more time feeding than
the adult and third year birds.

Tbe mean weekly numbers were found to increase gradually to a peak in late November
or early December. This is thought to be due to the influx of Herring Gulls from the
western Great Lakes. The final disappearance of gulls from the Kingston area came just
after the local freezing of Lake Ontario and it is postulated that the lack of drinking water
near the dump triggered the departure.

ACKNOWLEDGMENTS

This study was performed under contract for the Canadian Wildlife .Service. \^'e would
j like to thank members of the Kingston Field Naturalists for their assistance in field
' work, and Dr. IL N. .Smallman, who piloted us for the acuial surveys. Finally, we
would like to thank mend)ers of the Kingston (aty W'orks Department for their kind
cooperation in allowing access to the city dumi).

172

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

LITERATURE CITED

Drury, W. H., Jr., and W. J. Smith. 1968. Defense of feeding areas by adult Herring
Gulls and intrusion by young. Evolution, 22:193-201.

Dwight, J. 1925. The gulls (Laridae) of the world; their plumages, moults, varia-
tions, relationships and distribution. Bull. Amer. Mus. Nat. Hist., 52:63-402.

Gross, A. 0. 1940. The migration of Kent Island Herring Gulls. Bird-Banding, 11:

129-155.

Hofslund, P. B. 1959. Fall migration of Herring Gulls from Knife Island, Minnesota.
Bird-Banding, 30:104-113.

Kadlec, J. A. and W. H. Drury, Jr. 1968. Structure of the New England Herring
Gull population. Ecology 99:644-675.

Poor, H. H. 1943. Color-banded immature Herring Gulls in the New York region.
Bird-Banding, 14:101-115.

ScHREiBER, R. W. 1967. Roosting behavior of the Herring Gulls in central Maine.
Wilson Bull., 79:421-443.

ScHREiBER, R. W. 1%8. Seasonal population fluctuations of Herring Gulls in central
Maine. Bird-Banding, 39:81-106.

Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill
Book Co., New York.

Smith, W. J. 1959. Movements of Michigan Herring Gulls. Bird-Banding, 30:69-104.
Tinbergen, N. 1953. The Herring Gull’s world. Collins, London.

DEPARTMENT OF BIOLOGY, QUEEN’s UNIVERSITY, KINGSTON, ONTARIO, 8 DECEM-
BER 1970.

PUBLICATION NOTES AND NOTICES

Rare or Endangered Fish and Wildlife of New Jersey. Edited by Donald S.
Heintzelman. Science Notes No. 4, New Jersey State Museum, Trenton, N.J., 1971:
8% X 11 in-, paper covered, mimeographed, 23 pp. Free. Request from the Science
Bureau, New Jersey State Museum, 205 West State Street, Trenton, N.J. 08625.

The last natural history survey in New Jersey was conducted more than 60 years ago.
Since then, enormous environmental changes have taken place, resulting in declines of
many species of vertebrates. The present report lists animals which are considered
rare or endangered, or whose status is unknown. It is sobering to find that there are
37 rare species (including 14 birds), 18 endangered species (6 birds), and 22 species
(6 birds) of undetermined status. The modest format of this report helies its im-
portance as a conservation document. The report calls attention to the urgent need
for surveys of the current status of wildlife resources in New Jersey, and for measures to
protect vanishing animals. — P.S.

VARIATIONS IN SONGS OF VESPER SPARROWS
IN OREGON

Donald E. Kroodsma

The Vesper Sparrow [Pooecetes gramineus) is an abundant breeding bird
throughout much of its range, yet little is known about the behavior of
this species. During the summers 1969-1971 I have listened to and recorded
many Vesper Sparrow songs in the Willamette Valley of Oregon. Here 1 de-
scribe and discuss: 1) the song in the individual male, 2) noticeable dialect pat-
terns in the songs, and 3) an apparent example of mimicry of a Bewick’s
Wren (Thryomanes hewickii) .

I recorded songs at a tape speed of 7.5 ips on a Uher 4000 Report-L tape recorder
using a MD405S Cardioid microphone in a 60 cm diameter parabolic reflector. The Kay
Sonagraph with the wide (300 Hz) bandpass filter was used to prepare the sonagrams.

DESCRIPTION OF THE SONG

The songs of the Vesper Sparrow in Oregon are similar to those of the
eastern subspecies described by Borror (1961). The song is a series of trills,
and consists of two-four syllables of relatively long whistled notes followed
by as many as seven trills (mean = 4.8, n = 507) of more rapidly repeated
syllables (for terminology see Mulligan, 1966). A typical song from
the William L. Finley National Wildlife Refuge (Fig. lA ) consists of three
introductory syllables followed by five trills. The last trill is frequently ab-
breviated to a single syllable.

The introductory pattern in the songs of a given bird differ primarily in the
number of syllables; when stimulated (e.g., by playback) fewer syllables are
used with the more rapid singing rate. The remainder of the song is highly
variable; in 400 songs from one individual I found 43 different trill types.
Ten of the 43 different trills (often a single syllable) were used relatively
infrequently (a total of 48 times) and only on the end of the song. No trill
type was used exclusively following the introductory whistles, though two
trill types were used here in 363 of the 400 songs (90.8 per cent). I found
218 different trill sequences in the 400 songs; the maximum number of con-
secutive songs with identical sequences was eight, hut 175 of the 218 se-
quences were used only once. Some commonly used |)atterns involving two-
three trills were apparent within the song, hut the highly variable nature of
the song is evident. Analyses of recordings from other males did rev(‘al
comparable variability.

1 73

174

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

l»*/u

®' ■ 9-

- B - mm

3- mam mam

Ki C

lamm mam

—

4MB

mam mmm

; 0 V \i _ J,

AI Bl Cl A2

,T

DZ A3 E3

A4 F4 AS 6S H5 A6

;'v u

16 JB A7 K7

1 i 1 ^ , 1

' ' 2 3 4 ^5

■\m\\\\^) 1 1' |i |i ii

- > N > > >

\U

N A ^ ^

Donald E.
Kroodsma

VESPER SPARROW SONGS

175

DIALECTS

For the eastern subspecies Borror (1961:170) describes the notes of the
introductory pattern as being of ‘‘2 types, the first one or two being weaker
and lower pitched than the rest.” Peterson (1947, 1961, 1963) in his three
field guides to the United States uses the same description. These are attempts
to characterize the introductory phrases over large geographical areas, but a
closer examination reveals apparent dialect patterns. At the Finley Refuge,
Vesper Sparrows sing an introductory pattern as shown in Figure lA and IB;
the syllables consist of two relatively pure frequency notes, the first higher
pitched than the second. Only 5 km to the northwest, the introductory pat-
terns are quite different, and consist of two-four notes of the same frequency
(Fig. 1C). Approximately 8 km to the northeast from the Finley Refuge
I heard still another introductory pattern from several males; it consisted
of four notes, the first two of a higher frequency than the last two. This pat-
tern of geographical variation in the introductory phrase is similar to the
pattern found in the songs of some passerines where juvenile males learn their
adult songs (e.g., Marler, 1967) .

Of 60 trill types recorded from other Vesper Sparrows on the Finley
Refuge, 10 (16.7 per cent) were identical to those in the repertoire of the
single individual discussed above (Fig. ID). Only one of 16 (6.2 per cent)
trill types recorded from the location 5 km distant were identical. The sample
size is insufficient as proof, but is suggestive that inter-locality differences may
occur, probably as a result of song learning.

One prerequisite for maintenance of local dialects is that birds show a high
degree of site tenacity to the locality where songs are learned. Adults do
generally return to previous breeding sites (George, 1952), but no data are
available for the young.

APPARENT INTERSPECIFIC MIMICRY

Further evidence suggesting that juvenile male Vesper Sparrows might
learn their songs lies in the apparent mimicry of a Bewick’s Wren song by
a Vesper Sparrow (Fig. IE). Vesper Sparrows are highly variable songsters,

<-

Fig. 1. A, a typical Vesper Sparrow song from tlie Finley Wildlife Refuge. B,
introductory patterns from songs of four different individuals at the Finley Refuge. C!,
I introductory patterns from songs of four different individuals 5 km northwest of the
I Finley Refuge. 1), seven syllable types of the well studied male <A) compared with
j syllable types of other males (B-K) on the Finley Refug<*. Syllable tyjx's 1. 5. and h
were found in 2 neighbors of Bird A. E, an atypical Vesper Sparrow song (top) and
I portions of two Bewick’s Wren songs believed to he mimicked (below). I'lie time markers
I indicate VI' sec, and the vertical scale is marked in kHz.

176

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Table 1.

Analysis of 604 songs from atypically singing Vesper Sparrow

Trill Sequence

Number of songs

Per cent

1-2-3-4-5

330

54.6

1_2-3-4-5-6

58

9.6

1_2-3-4^6

69

11.4

1_2-3-4-6-7

147

24.3

Z = 604

V

= 99.9

and Armstrong (1963:73) rightly warns that “Very loquacious birds are apt
to utter calls fortuitously resembling those of other species just as a silly
person who talks incessantly will occasionally say something sensible.” How-
ever, several facts do suggest the bird was indeed mimicking a Bewick’s Wren.
The introductory portion is very unlike that of any Vesper Sparrow; the
average frequency is higher than that of any other trill encountered in this
study, but is very similar to the high frequency notes which often precede the
song of a highly stimulated Bewick’s Wren. Syllable types 2-4 ( Fig. IE )
are almost identical to those found in a single song type of most Bewick’s
Wrens at the Finley Refuge, and syllable type 5 is like that found in another
song type shared by many of the wrens. I found no simple buzzes like syllable
type 3 inserted into normal Vesper Sparrow songs. I studied 604 songs from
this individual; all began with syllable types 1-4, but one or two other trills
(numbers 6 and 7, not illustrated), both typically Vesper Sparrow, were also
used (see Table 1). This relative lack of variability in number (only seven)
and sequences (only four) of trill types is very atypical for Vesper Sparrows
(see above), but the rigid sequence is like that found in the song types of the
Bewick’s Wren.

Spectrographic analysis revealed the apparent mimicry, but the reactions
of three neighboring, territorial male wrens indicated that even the wrens mis-
took the identity of this bird. The Vesper Sparrow usually sang from several
trees in a small clearing which was bordered on two sides by dense riparian
vegetation. Early in the spring when the sparrow approached the riverbottom,
the wrens responded with the pit or chit notes used nearly exclusively in
territorial encounters ( Miller, 1941, and pers. observ. ) . In addition, the wrens
frequently countersang with the song type in their repertoire which resembled
the song of the Vesper Sparrow. Later in the season it appeared as if the
wrens had habituated to the song, for they responded less aggressively.

Thus, the evidence indicates that Vesper Sparrows may learn part or per-
haps all of their songs. Normal song development in many species requires

Donald E.
Kroodsnia

VESPER SPARROW SONGS

177

hearing conspecific males. Wild birds of these species may incorporate into
their subsong the calls or songs of other species, but the adult song is usually
free of such mimicry. If juvenile males are isolated in captivity and tutored
with the songs of other species, they do occasionally learn that species’ song.
The Chaffinch {Fringilla coelebs) and the Western Meadowlark (Sturnella
neglecta) are two examples (Thorpe, 1961 and Lanyon, 1960, respectively).
Non-captive Indian Hill Mynahs (Gracula religiosa) learn their call notes
from conspecifics, and do not normally mimic other species; captive Mynahs,
on the contrary, are renowned for their imitative abilities (Bertram, 1970).

Varying degrees of isolation in the field could also prevent sufficient ex-
posure to songs of conspecifics. A bird raised by an isolated pair and which
subsequently wanders through marginal habitats could be insufficiently
exposed. Since Vesper Sparrows normally migrate to southern California and
if young males are normally receptive in the fall, a bird of a very late summer
brood might be exposed to few songs prior to migration. Occasionally a few
birds do over-winter in the Willamette Valley. A non-migratory bird would
very likely be totally isolated from birds of its own species. In a migratory
species it is unlikely that a critical period for song learning occurs during
the winter season when most males are silent. However, if young males are
usually receptive in the spring, the onset of territorial behavior and perhaps
the critical period for song learning in an over-wintering juvenile male could
occur prior to the return of conspecifics. As in the laboratory, a secondary
preference for the songs of other species might then be expressed. Exposure
to wren songs is no difficulty, for wrens are abundant and remain territorial
and sing throughout the year.

The very reduced repertoire of this atypically singing Vesper Sparrow per-
haps also suggests some isolation from singing conspecifics. One intuitively
expects, within limits of course, that if songs are learned or developed through
listening to adults, the greater the exposure the more will be learned. Thus,
juvenile male Bewick’s Wrens learn their songs from adult males during their
first summer, and those hatched early in the breeding season develop more
syllable types and song types than those hatched later when the singing in-
tensity of adults is reduced ( Kroodsma, in prep. ) .

SUMMARY

I The song of the Vesper Sparrow in Oregon consists of a whistled introducton j)hrase
followed hy as many as seven different trills. One well-studied individual had a repertoire
of 43 different trill types, and sang 218 different trill secpienees in 400 songs. 'Flu* simi-
I larities of the trills among neighboring males and the consistent inter-locality differences
i in the introductory whistled notes suggest that Vesj)er Sparrows h*arn at least portions of
their songs from adult conspecifics. Otu* male had a reduced song r«‘pertoire and sang
I like a Bewick’s Wren; insufficient exposure to songs of adult conspecifics may cau"e
I interspecific learning.

I

I

178

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

ACKNOWLEDGMENTS

Personnel of the William Finley Refuge were most helpful throughout the study. Donald
J. Borror offered helpful suggestions for improving the manuscript. Financial aid was
provided by an NDEA Title IV predoctoral fellowship.

LITERATURE CITED

Armstrong, E. A. 1963. A study of bird song. Oxford Univ. Press, London.

Bertram, B. 1970. The vocal behavior of the Indian Hill Mynah, Gracula religiosa.
Anim. Behav. Monogr., 3:79-192.

Borror, D. J. 1951, Songs of finches ( Fringillidae) of Eastern North America. Ohio J.
Sci., 61:161-174.

George, J. L. 1952. The birds on a southern Michigan farm. Unpubl. Ph.D. Thesis,
University of Michigan, Ann Arbor. (Cited in: Berger, A. J. 1968. Eastern Vesper
Sparrow. In: 0. L. Austin, Jr. (Ed.) Life histories of North American cardinals,
grosbeaks, buntings, towhees, finches, sparrows, and allies. U. S. Natl. Mus., Bull.
237:868-882.)

Lanyon, W. E. 1960. The ontogeny of vocalizations in birds, p. 321-347. In: W. E.
Lanyon and W. N. Tavolga (Eds.). Animal sounds and communications. A.I.B.S.,
Washington, D. C,

Marler, P. 1967. Acoustical influences in birdsong development. Rockefeller Univ.
Review, Sept.-Oct. :8-13.

Miller, E. V. 1941. Behavior of the Bewick Wren. Condor, 43:81-99.

Mulligan, J. A. 1966. Singing behavior and its development in the Song Sparrow,
Melospiza melodia. Univ. California Publ. Zool., 81:1-76.

Peterson, R. T. 1947. A field guide to the birds. Houghton Mifflin Co., Boston.
Peterson, R. T. 1961. A field guide to western birds. Houghton Mifflin Co., Boston.
Peterson, R. T. 1963. A field guide to the birds of Texas and adjacent states. Houghton
Mifflin Co., Boston.

Thorpe, W. H. 1961. Bird song: The biology of vocal communication and expression
in birds. Cambridge Univ. Press, Cambridge,

DEP.\RTMENT OF ZOOLOGY, OREGON STATE UNIVERSITY, CORVALLIS, OREGON,

97331, 12 OCTOBER 1971.

PUBLICATION NOTES AND NOTICES

Pesticides and Wildlife. [By J. A. Keith and R. W. Fyfe.l Canadian Wildlife Service,
Ottawa, 1971: 6)4 X 9 in., paper covered, 24 pp., photographs. No price given.

A collection of four articles about research, chiefly in Canada, on the side effects on
various wildlife species of the use of agricultural and industrial chemicals. The authors
are biologists in the Canadian Wildlife Service. The articles repeat each other to some
extent and the story is no longer new; nevertheless the message is well set forth in non-
technical language. To quote Fyfe: “If I have been attacking anything, it is all untested
and unjustified use. together with the continued defense of widespread applications, of
the broad spectrum persistent biocides which are affecting this environment: our en-
vironment and that of our children.” — P.S.

FACTORS INFLUENCING PELLET EGESTION AND
GASTRIC pH IN THE BARN OWL

Charles R. Smith and Milo E. Richmond

The volume of literature considering the food habits of owls approaches
prodigious proportions (see Earhart and Johnson, 1970). Much of this
information has been derived from analysis of the pellets of non-digestible
matter which these raptors egest periodically. A number of authors have re-
viewed this technique and its applications (Craighead and Craighead, 1956;
Errington, 1930, 1932; Fisher, 1893, 1896; Glading, Tillotson and Selleck,
1943; Moon, 1940). In spite of the widespread interest in raptor-pellet anal-
ysis and application of this procedure for estimating food intake of these birds
in the wild, very little information is available on the factors relative to the
processes of pellet formation and egestion in birds of prey (Earner, 1960).

The Great Horned Owl [Bubo virginianus) is the only owl for which pellet
formation has been studied (Reed and Reed, 1928). Other papers consider-
ing pellet “formation” in owls have been concerned largely with the intervals
between feeding and pellet egestion and have not dealt directly with the di-
gestive processes involved in pellet formation or the factors which determine
pellet egestion (Chitty, 1938; Howard, 1958; Sensenig, 1945). Two extensive
life history studies of the Barn Owl [Tyto alba) by Guerin (1928) and Wal-
lace (1948) offer some information relative to pellet formation and egestion
in that species. It is the intent of this paper to present further information
relative to the processes involved in pellet formation and egestion in the Barn
Owl.

MATERIALS AND METHODS

The Barn Owl used in this investigation was obtained near Johnson City, Tennessee,
at the age of approximately 20 days, as determined by plumage description (Bent, 1938;
Roberts, 1955) . The bird was kept in captivity and fed small mammals and birds ( both
alive and dead), beef liver, and a commercial liquid vitamin supplement (“ABDEC”)
until it was about 8 weeks old. At the age of 8 weeks, the bird was moved from its
outdoor cage into a laboratory at East Tennessee State University and tests wbicli re-
quired regular handling were begun. The owl adapted readily to laboratory conditions
and required no special bousing or handling technique. A laboratory colony of prairie
voles (Microtus ochrogaster) provided the primary food source for the owl. At first,
the voles were fed to the owl dead; later, the owl learned to take and kill live* voles
which were either released into the cage or placed on the floor of the lab.

To determine the pH of the gastric contents, a stomach sample was obtained by insert-
ing a lO-mm pipette e(|uipped with suction bulb into the esophagus of the bird until
it reached the region of the gizzard. By this method samph's of volume from 0.5 to 1
ml could he withdrawn from the region of the gizzard and from the prov<‘ntrieuhis.
The bird showed no adverse effects from this procedure which was sometimes eonduet(‘d

179

180

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

2 4 6 8

After feeding and before egestion

0 1
HOURS

2 4 6 8

After egestion and before feeding

Fig. 1. Changes in gastric pH of the Barn Owl before and after feeding (curAe fitted
by inspection).

at hourly intersals for a 12-hour period. The pH of the samples was determined by
using a Corning ‘’Model Six" portable pH meter. The presence or absence of free HCl in
stomach samples was detected with standard Topfer's solution, but the sample size was
insufficient for accurate titration of the quantity of free HCl. The pH of extracts
squeezed manually from newly egested pellets was also determined with the pH meter.

RESULTS AND DISCUSSION

Gastric acidity. — A total of 58 stomach samples, taken both before and
after the bird had eaten, provided data for the cumulative graph of gastric
acidity in Eigure 1. The data show that the pH gradually rises after feeding
and continues to increase until pellet egestion. ithin an hour after pellet
egestion. there is a precipitous drop, followed by another rise until the pH
values stabilize in the vicinity of 4.0. Earner (I960), reported a gastric pH
range of 3.53-4.90 for the Barn Owl. Our data ( Fig. 1) show a much wider
range of pH extending from 1.9 to 6.2. The low pH values immediately
following egestion indicate a gastric state especially conducive to high peptic
activity and proteolysis since the optimum state for these activities is in the
vicinity of pH 2.0 l Earner. 1960 I .

Figure 2 shows the results of two separate days of pH recordings at hourly
intervals under different conditions. Equal amounts of food were given at

Smith and
Richmond

BARN OWL PELLET EGESTION

181

HOURS AFTER FEEDING

Fig. 2. Hourly changes in the pH of the gastric juice of the Barn Owl with (solid
line) and without (dashed line) water available.

the same time on each day; however, in one case drinking water was avail-
ahle and in the other it was not. Excess food was not available in either case.
With water available, the increase in pH during hours 1 and 6 and the gen-
erally higher pH values prior to pellet egestion followed known water con-
sumption. Clearly, the water consumed reduced the acidity of gastric contents.
The graph of gastric acidity obtained in the absence of water closely resembles
the graph of Figure 1, which also was made in the absence of drinking water.
The pH values of extracts from freshly egested pellets were very similar
to the pH values of stomach samples taken within an hour before pellet eges-
tion. Contrary to the observations of Reed and Reed ( 1928 1 on the Great
Horned Owd, free HCl was found in stomach samples from the Barn Owl on
six separate occasions when pH values ranged from 1.9 to 3.1. Free HCl was
present most often immediately after pellet egestion or soon after the owl had
been shown a live vole.

Classically, there are three phases to the secretion of gastric juice: the

cephalic, the gastric, and the intestinal ( Houssay. 1955). I he cephalic jihase
involves the stimulus of gastric secretion as a result of external factors, such
as the sight or smell of food, mediated through the cerebral cortex. I he

]82

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

mechanisms involved form the basis for classical Pavlovian conditioning.
According to Earner (1960), a true cephalic phase of gastric secretion is
lacking in the domestic fowl. Walter (1939), however, reported gastric
juice secretion in ducks in the response to auditory stimuli. Our results
would indicate that a cephalic phase of gastric secretion is present in the Barn
Owl. We learned, for example, that the pH of gastric contents decreased
markedly within one-half hour after we entered the room in which the owl
was kept. This decreased pH, indicative of increased HCl secretion in antici-
pation of food, was observed numerous times when live voles were placed in
view of the owl but outside its cage. Eree HCl was also present in stomach
samples taken after the owl had been shown a live vole, and the same marked
drop in gastric pH was observed in the bird after it had been fasted and then
was allowed to observe live prey.

Pellet formation. — There is some disagreement in the literature as to where
in the digestive tract pellet formation occurs. Welty (1963 ) suggests that
the pellet is formed in the gizzard. Wallace (1955) states that pellet forma-
tion occurs in the proventriculus. Guerin (1928 ) felt that the gizzard played
a significant role in pellet formation because of its highly muscular qualities.
He also reported that dissection revealed pellet material in both the pro-
ventriculus and gizzard at different times, but he did not relate its place of
occurrence to either times of feeding or pellet egestion.

Probing with the pipette while taking gastric samples indicated the pres-
ence of pellet material in both the proventriculus and the gizzard at different
times. However, probing immediately before egestion indicated that the pellet
was located in the proventriculus and not in the gizzard.

Reed and Reed (1928) reported that the “stomach” musculature in the
Great Horned Owl is weak and not capable of exerting a great deal of force.
These authors apparently were referring to the glandular stomach (proven-
triculus ) since the gizzard is noted for its muscular structure. The muscular
ability of the proventriculus of the Barn Owl closely resembles that of the
Great Horned Owl. This seems to argue against the proventriculus playing
any major role in the process of pellet formation. However, it is possible
that the proventriculus could function as a repository for a freshly formed
pellet prior to egestion. It is our contention, then, that the pellet is formed
by the muscular action of the gizzard during digestion. At some stage after
the completion of digestion, the freshly formed pellet passes out of the giz-
zard into the proventriculus where it remains until the proper stimulus for
egestion is received.

Pellet egestion. — Initial observations suggested that the time of feeding
had some influence on the time of subsequent egestion. To test this possibility,
food was offered at various times of the day and night. All feedings between

Smith and
Richmond

BARN OWL PELLET EGESTION

183

Fig. 3. The effects of feeding time, prey weight and visible prey on pellet egestion
in the Barn Owl.

06:00 and 14:00 were arbitrarily grouped as “day feedings,” while feedings
from 16:00 until 24:00 were considered “night feedings.” Figure 3 illustrates
the effects of both time of feeding and food weight on the subsequent egestion
of a pellet. The Y intercepts of the two lines ( day = 7.08, night = 9.98 ) are
different, showing that time between feeding and pellet egestion is longer
at nigbt than during the day. The calculated slopes from day and night
feedings are significantly different from zero (P^O.05) but not different
from each other, pointing out that increasing prey weight delayed pellet
egestion in the experimental owl regardless of time of feeding. Similar obser-
vations have been reported for the Short-eared Owl {Asia flarnnieus) (Chitty,
1938).

The Great Horned Owl (Reed, 1925) and the Tawny and Short-eared Owls
(Chitty, 1938) have been observed to egest a jiellet when presented with
j another food item. Guerin (1928) reported a similar phenomenon in the
I Barn Owl in Europe, and Reed (1897) observed a similar reaction in Ameri-
I can Barn Owls. Our Barn Owl could be induced to egest a jiellet simply by
' allowing it to see a live vole after a sufficient time bad elapsed since the last

184

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

In order to examine the degree of influence of excess available prey on the
normal pattern of pellet egestion, the bird was fed a prey item of known weight
after which a wire cage containing additional live prey was placed in view
of the bird. The owl could be observed from outside the room and as soon
as the pellet was egested, the bird was given another weighed meal. This was
continued with different size prey during both day and night periods until
the owl killed and stored the prey instead of eating it. A total of 16 food-
induced pellets, obtained in this manner, provided the data for the bottom
line in Figure 3 which indicates that no difference in time until pellet eges-
tion exists between day and night feedings when the owl is aware of the
possibility of a subsequent meal. In addition, the slope from the pooled
day-night feedings does not differ from zero even though prey weight varied
from 10 to 81 grams. Since the stimulation provided by live prey was present
during both day and night feedings, and since the prey consumed varied in
weight from 10 to 81 grams, it is obvious that neither quantity consumed nor
time of feeding delayed pellet egestion when a potential meal was in view.

The minimum time elapsing before the owl could be induced to egest a
pellet by additional prey was about 6.5 hours (Y = 6.42 hours). A few pel-
lets have been recovered under unusual circumstances in less time but the
normal pattern for the bird is to continue eating prey when available prior
to the 6.5-hour critical period and then form one large pellet which is egested
long after the first meal was taken. Guerin ( 1928 ) also showed that subse-
quent feeding delayed pellet egestion in the Barn Owl. Few of our data relate
to this, but the indication is that mice swallowed at intervals of less than 6
hours act to delay pellet egestion until the last prey item is digested. Obviously,
this delaying effect has limits governed by the bird’s capacity, but on sev-
eral occasions two, three, and four mice have been consumed over an 8-hour
period and all have been incorporated into a single pellet. Likewise, it is not
unusual to find four, five, and even six Microtus skulls in a single Barn Owl
pellet collected at a roost. Such instances are probably the result of continuous
food intake with the intervals between successive meals never exceeding the
critical 6.5-hour period after which a pellet would be formed and could be
egested in response to the detection of a potential prey item.

Since pellet egestion can be prey-induced but is normally delayed when
capture intervals are short, a bird completing a successful night of hunting
would require the daylight hours to digest the mass of food it had collected.
In the case of either a successful night of hunting or a poor night during which
no mice were caught late enough to stimulate pellet egestion, the pellet formed
and egested at the day roost would contain remains of everything the bird
had consumed. The factors which determine the length of time that a pellet
will be retained are (1) the length of time since the last food was consumed.

Smitli and
Richmond

BARN OWL PELLET EGESTION

185

which in this study was at least 6.5 hours, and (2) the detection or capture
of a prey item by the bird. Chitty ( 1938 ) suggested that hunger determines
the length of time that a pellet is retained in the digestive tract before eges-
tion. Hunger, however, would be a direct consequence of the bird not having
prey available. In the absence of prey the pellet would be retained, not as a
result of hunger, but as a result of a lack of the proper stimulus ( available
prey) for pellet egestion. This does not mean that egestion cannot occur in
the absence of a stimulus but clearly it is delayed in such instances.

It is reasonable to assume, then, that most of the pellets collected at the
roost site of a wild Barn Owl represent one successful night of hunting for
each pellet. The possible exception to this would be those pellets egested on
the feeding ground on a night of hunting during which only two or three mice
were caught, with a period of 7 to 8 hours between any two successive cap-
tures ( e.g., during a long winter night ) . In such a situation, a pellet would
probably be egested away from the roost site, as suggested by Craighead and
Craighead ( 1956 ) and reported by Cuerin ( 1928 ) . The egestion of such a
pellet would be triggered by the last mouse caught. The pellet egested the
next day, however, would still represent as much as half of the previous
night’s catch. One could judge the possibility of such an occurrence by
determining the owl’s hunting success as indicated by the number of prey items
in each of the pellets collected at the roost. Small pellets containing only one
prey item would be indicative of egestion away from the roost site and detract
from the reliability of making judgments about food consumption from roost
pellet collections.

SUMMARY

The factors influencing rates of pellet formation and egestion were studied in a Barn
Owl kept in captivity for 6 months. The pH of the gastric contents changes according
to a regular pattern from feeding until pellet egestion, hut it could not he implicated
definitely as a mechanism that triggers actual egestion. Data on gastric pH demonstrate
the presence of a cephalic phase of digestion. The pellet is formed in the gizzard within
6 hours after ingesting a meal, and is passed into the proventriculus where it is held until
egestion. Pellets are not egested at a fixed interval after taking a meal; the interval
is dependent in part upon quantity of food consumed, time of feeding and availability of
a suhsecjuent meal. Increased prey weight and night feedings prolong the time to egestion
hut have no effect when a suhseciuent meal is available.

LITERATURE CITED

Bknt, a. C. 19.H8. Life histories of North American birds of prey. Ik .S. Natl. Mus.
Bulk, 170.

Chitty, I). 1988. A laboratory study of pellet formation in the Short-eared Owl

(Asia flanuneus) . Proc. Zool. .Soc. London, .Ser. A, 108:267-287.

(iKAKHiKAi), .1. .L, AND F. (k ( AIG 1 1 K Ai), Jr. 19.86. Hawks, owls, and wildlife. Stack-
poh‘ Co., Harrisburg, Pennsylvania.

186

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Earhart, C. M., and N. K. Johnson. 1970. Size dimorphism and food habits of North
American owls. Condor, 72:251-264.

Errington, P. L. 1930. The pellet analysis method of raptor food habits study. Condor,
32:292-296.

Errington, P. L. 1932. Technique of raptor food habits study. Condor, 34:75-86.

Earner, D. S. 1%0. Digestion and the digestive system. In A. J. Marshall (Ed.),
Biology and comparative physiology of birds, Vol. 1, Academic Press, New Tork,
pp. 411-467.

Fisher, A. K. 1893. The hawks and owls of the United States in their relation to
agriculture. L . S. Dept. Agric., Div. of Ornithol. and Mammal., Bull. 3.

Fisher, A. K. 18%. Food of the Barn Owl. Science, 3:623-624.

Glading, B., D. F. Tillotson, and D. M. Selleck. 1943. Raptor pellets as indicators
of food habits. California Fish and Game, 29:92-121.

Guerin, G. 1928. La vie des Cihouettes. Regime et Croissance de I'Effraye commune
Tyto alba alba (L) en vendee. P. Lechevalier, Paris.

Houssay, B. a. 1955. Human physiology. McGraw Hill, New \ ork.

Howard, W. E. 1958. Food intake and pellet formation of a Horned Owl. Wilson Bull.,
70:145-150.

Moon, E. L. 1940. Notes on hawk and owl pellet formation and identification. Trans.
Kansas Acad. Sci., 43:457-466.

Reed, B. P. 1925. Growth, development, and reactions of young Great Horned Owls.
Auk. 42:14^31.

Reed, C. L, and B. P. Reed. 1928. The mechanism of pellet formation in the Great
Horned Owl ^ Bubo virginianus ) . Science. 68 : 359-360.

Reed, J. H. 1897. Notes on the American Bam Owl in eastern Pennsylvania. Auk, 14:
374^383.

Roberts, T. S. 1955. A manual for the identification of the birds of Minnesota and
neighboring states. Univ. of Minnesota Press, Minneapolis.

Sensenig, E. C. 1945. The formation of pellets by the Barred Owl. Vi’ilson Bull., 57:
132.

Wallace. G. J. 1948. The Barn Owl in Michigan. Tech. Bull. 208, Michigan State
College Agric. Expt. Sta., East Lansing. Michigan.

Wallace. G. J. 1955. An introduction to ornithology. Macmillan Co., New York.

Walter. W. G. 1939. Bedingte Magensaftsekretion hie der Ente. Acta Brevia Neerl..
9:56.

\^’elty. j. C. 1%3. The life of birds. Alfred A. Knopf, New York.

DEPARTMENT OF BIOLOGY. EAST TENNESSEE STATE UNIVERSITY, JOHNSON CITY,
TENNESSEE I PRESENT ADDRESS: NEW YORK COOPERATIVE WILDLIFE RESEARCH
UNIT. CORNELL UNIVERSITY, ITHACA. NEW YORK 14850 I AND BUREAU OF
SPORT FISHERIES AND WILDLIFE, CORNELL UNIVERSITY, ITHACA, NEW YORK

14850. 24 JULY 1971.

ANALYSIS OF MEASUREMENTS, WEIGHTS, AND
COMPOSITION OF COMMON AND ROSEATE TERN EGGS

Charles T. Collins and Mary LeCroy

An abundance of data has been presented on various aspects of the eggs
_of birds. Most studies have been concerned with intraclutch, intra-
specific, and interspecific variations in egg color and dimensions (Coulson,
1963; Preston, 1953, 1957; Preston and Preston, 1953; and others) with
little information being given on egg weights and almost none on the pro-
portions of the various egg components. Data of all sorts are particularly
incomplete for semiprecocial species as skuas, gulls, and terns. In this light
it seemed worthwhile to gather information on this aspect of the annual
cycle of the Common Tern {Sterna hirundo) and Roseate Tern {Sterna
dougallii) as a part of a wider study of the reproductive biology of these
species nesting on Great Gull Island, Suffolk County, New York. Further
information on this colony and the growth and development of chicks of
both tern species is presented elsewhere (Cooper, Hays, and Pessino, 1970;
Hays, 1970; LeCroy and Collins, 1972).

METHODS

For this analysis 20 freshly laid eggs of each species were collected at random on
Great Gull Island in early June 1967, at which time egg laying was just beginning. To
insure freshness, eggs were only taken from areas which were checked daily for new
nests and from nests containing but a single egg. In most cases this would be the first
egg of a multi-egg clutch but some cases may have represented single egg clutches. It
was expected that removal of eggs this early in the reproductive cycle would result
in renesting by the pair and thus minimize any losses to the colony. A larger sample
size was not considered necessary and might in fact have interfered with other studies
being conducted in the colony. Weights were taken to the nearest tenth of a gram
on a triple beam balance. Linear measurements were made to the nearest tenth of a
millimeter by means of dial calipers. The data collected in this study are presented as
a mean lx) accompanied by the range and ± twice the standard error of the mean ( Sx )
which for large samples closely approximates the 95 per cent confidence intenal. \'ihen
these intervals are nearly ecjual in length and nonoverlapping, the difference between the
samples can he considered significant at the 5 per cent level (.Sim{)son, Roe. and la'wontin.
1%0:3.53).

EGG SIZE

ITe data on the size of Common and Roseate Fern eggs are jtresenled in
Table 1. Roseate eggs were significantly narrower than those of (.ommon
Terns, leading to an also significantly lower shape index. Ibis difference
in shape did not, however, apjtreciahly affect the overall weight of the eggs,
which was similar in both species ( lahle 1.). It should he rememhert'd that

187

188

THE WILSON BULLETIN

June 1972
Vol. 81, No. 2

Table 1

Size of Common and Roseate Tern Eggs

Mean

(x)

Twice

Standard

Error

(±2S,)

( Range )

Common Tern (N = 20)

Length (mm)

42.94

±0.642

(40.4^45.9)

Width (mm)

30.49

±0.316

(29.2-31.9)

Shape Index“

72.91

±1.378

(67.3-78.4)

Weight (g)

21.01

±0.540

(18.7-23.8)

Roseate Tern (N = 20)

Length (mm)

43.90

±0.890

(40.5-48.5)

Width (mm)

29.90

±0.272

(28.8-31.0)

Shape Index®

69.82

±1.470

(64.5-76.8)

Weight (g)

20.56

±0.540

(19.2-23.7)

® 100 X width/length.

these samples represented only the first egg of multi-egg clutches or in some
cases single egg clutches. As there is a great deal of intraclutch variation in
linear measurements ( Gemperle and Preston, 1955; LeCroy, unpubl. ) these
apparent specific differences may not hold true when the full scope of egg
sizes in the colony are considered. Such interspecific differences were not
found for the remaining data collected on the eggs of these terns. Thus it is
unlikely that the conclusions based on these data would be altered by larger
sample sizes or analysis of intraclutch variation.

EGG SIZE RELATIVE TO BODY WEIGHT

No body weights for adult Common and Roseate Terns are available for a
period when eggs were being laid or when eggs used in this study were col-
lected. Adult body weights for both species for the period 29 June-2 July
1968 are as follows: Common Tern (N = 56) 116.1 ± 1.646 g (range, 103-
129 g) ; Roseate Tern (N = 46) 107.7 ± 1.898 g (range, 92-125 g). Using
these values, the eggs of Common and Roseate Terns are respectively 18.1
per cent and 19.3 per cent of adult body weight. Such high values seem
typical of many terns and other semiprecocial birds while those for most
altricial species are appreciably lower, frequently less than 10 per cent ( Lack,
1968 ). The larger bird species in nearly all taxa show a pronounced decrease
in the egg weight/body weight ratio which is independent of developmental
pattern ( Lack, op. cit.).

Collins and
LeCroy

COMMON AND ROSEATE TERN EGGS

189

Table 2

Composition of Common and Roseate Tern Eggs

Shell

Albumen

Yolk

Common Tern

2.22 ± 0.094“^

12.87 ± 0.422

5.94 ± 0.256

(N = 20)

(10.6%)

(61.2%)

(28.2%)

Roseate Tern

2.21 ± 0.086

12.26 ± 0.416

6.10 ± 0.248

(N = 20)

(10.7%)

(59.6%)

(29.7%)

“ Mean weight in grams ± 2 standard errors of the mean.

COMPOSITION OF THE EGG

The composition by weight and on a per cent basis are highly similar in
both species as shown in Table 2. The egg contents were poured from one
half-shell to the other until the albumen had been separated from the yolk.
The weight of the remaining shell and yolk was subtracted from the whole
egg weight to determine the weight of albumen removed. The shell ( in-
cluding shell membrane) was then weighed separately and the yolk weight
determined by subtraction. As the weighing was done in the field at the
colony no attempt was made to determine dry weights for any of these com-
ponents as has been done by some other workers ( Reid, 1965 ) .

DISCUSSION

Newly hatched young birds have long been assigned to one or the other of
two categories by their degree of maturity at hatching, e.g., precocial or
altricial. Analysis of egg sizes associated with these categories has shown
that species producing precocial young tend to lay large eggs relative to their
body weight, and ones in which the yolk makes up 30 to 40 per cent of the
total egg weight. On the other hand, those species producing altricial young
tend to produce smaller eggs relative to their body weight and ones containing
only 15 to 25 per cent yolk. As noted earlier, the eggs of larger birds in most
taxa are smaller, relative to body weight, and they also tend to contain rela-
tively less yolk than those of closely related but smaller species.

I The wide variation in developmental regimes makes the separation into hut
I two categories extremely difficult and misleading. The expanded classifica-
tion of Nice (1962:18) recognizes eight categories of maturity at hatching
based on the manner of getting food, amount of down, activity, and develop-
I ment of sight at hatching. In addition to making it possible to categorize
jl newly hatched young in a more realistic manner, this classification se(pience
j'l serves to point out the existence of a gradual transition in developmental
I patterns from that of the highly precocial s])ecies which are nearly indepen-

190

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Table 3

CO.MI’ARISON OF Fx(. CHARACTERISTICS IX PrECOCIAL, SeM IPRECOCIAI., AM) .AlIRICIAL

Species

Egg Components ( percentage by weight )

Yolk Albumen

Shell Albumen Yolk Index

Precocial Birds

Average of 10 species®

11.9

52.9

35.2

.665

Average of 5 species’*

10.5

56.4

33.1

.586

Semiprecocial Birds

Common Tern

10.6

61.2

28.2

.470

Roseate Tern

10.7

59.6

29.7

.506

South Polar Skua'

8.6

65.2

26.2

.409

Altricial Species

Average of 10 species®

7.0

73.2

19.8

.276

Average of 4 species’*

7.7

70.9

21.4

.305

® From: Romanoff and Romanoff, 1949.
**From: Asmundson, Baker, and Emlen, 1943.
^ From: Reid, unpublished, in Reid, 1965.

dent at hatching to that of the extremely helpless altricials requiring great
amounts of parental care at the other. Semiprecocial birds, as skuas, gulls, and
terns, fall near the middle of this sequence in that at hatching they are down
covered, their eyes are open, yet they stay in or near the nest and are fed by
the adults for several weeks.

The available information suggests that there has also been a gradual shift
in the relative amount of the components of bird eggs which goes along with
this transition in developmental pattern. The species with the more precocial
young tend to produce larger eggs with relatively more yolk. The extremely
precocial species of megapodes have eggs containing in excess of 60 per
cent yolk, while the eggs of most precocial species have 30-40 per cent and
most altricials 15-25 per cent yolk (Nice, 1962 :25j. Our data for Common
and Roseate Terns and that of Reid (1965 1 for the South Polar Skua
[Catharacta maccormicki) along with that previously available for other
species (Nice, 1962:25 ) indicate that the intermediacy of semiprecocial species
extends to the component characteristics of their eggs as well (Table 3).
Eggs of semiprecocial species usually contain between 25-30 per cent yolk
which is more than is found for the altricial and semialtricial groups but
less than for the eggs of precocial species. Table 3 also shows that the relative
amount of albumen increases during the transition from the precocial to altricial
mode of development. Shell weight is believed to be more a product of the
size of the bird and the incubation regime to which it is subjected (Welty,

Collins and
LeCroy

COMMON AND ROSEATE TERN EGGS

191

1962). The yolk/albumen index (Table 3) incorporates the relative changes
of both of these components with the different levels of maturity at hatching
and thus may be more helpful in indicating the changes in the components of
eggs associated with the several developmental patterns utilized by birds.
Further study is needed before the relative role of these components can be
determined for the different developmental patterns. Laboratory analysis of
the chemical composition of these components in species with different de-
velopmental patterns would also seem a fruitful area for further work.

SUMMARY

Eggs of Common {Sterna hirundo) and Roseate (Sterna dougallii) Terns, were col-
lected on Great Gull Island in June 1967. Roseate Tern eggs were significantly narrower
than those of Common Terns and had a significantly lower shape index. Such specific
differences were only found for the linear measurements and even these differences may
not be consistent when the full range of interclutch and intraclutch variation is con-
sidered. Egg weight of Common and Roseate Terns was 18.1 per cent and 19.3 per cent
respectively of adult weight, which is typical of values recorded for other species of terns.
The weights of egg shell, yolk and albumen were highly similar for both species with
yolk making up 28-30 per cent. This is appreciably higher than in the eggs of altricial
species and less than for precocials. These data point out the correlation between the
changes in egg component proportions and the several developmental patterns of birds.

ACKNOWLEDGMENTS

We would like to thank all of the investigators who have been working in the tern
colony on Great Gull Island, whose work has helped and complemented ours. Gary and
Mary Sue Schnell very kindly allowed us to use their unpublished weights of adult terns.
Great Gull Island research was supported by the Mae P. Smith Gull Fund, the Anne S.
Richardson Fund, and by the Linnaean Society of New York. Preparation of the manu-
script for publication was supported by a grant from tbe United States Atomic Energy
Commission at (38-) -310 to the University of Georgia.

LITERATURE CITED

Asmundson, V. S., E. A. Baker, and J. T. Emlen. 1943. Certain relations between
the parts of birds’ eggs. Auk, 60:34-44.

Cooper, D., H. Hays, and C. Pessino. 1970. Breeding of the Common and Roseate
Terns on Great Gull Island. Proc. Linnaean Soc. New York, 71:83-104.

CouLSON, J. C. 1963. Egg size and shape in the Kittiwake ^Rissa tridactyla) and their
use in estimating age composition of populations. Proc. Zool. Soc., London, 140:
211-227.

Gemperle, AI. E., and F. W. Preston. 19.55. Variation in sha})e in eggs of the Common
Tern in the clutch sequence. Auk, 72:184—197.

Hays, H. 1970. Great Gull Island report on nesting species 1%7-1968. Proc. Linnaean
Soc. New York, 71:105-119.

Lack, D. 1%8. Ecological adaptations for l)reeding in l)irds. Methuen and Co. Ltd..
D)ndon.

LeCroy, M., and C. T. Collins. 1972. Growth and survival of Roseate and Clommon
Tern chicks. Auk, 89: In Press.

192

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Nice, M. M. 1962. Development of liehavior in precocial l)irds. Trans. Linnaean Soc.
New York, 8:1-211.

Preston, F. W. 1953. The shapes of liircls’ eggs. Auk, 70:160-182.

Preston, F. W. 1957. Pigmentation of eggs: Variation in the clutch sequence. Auk,
74:28-41.

Preston, F. W., and E. J, Preston. 1953. Variation of the shapes of birds eggs within
the clutch. Ann. Carnegie Mus., Pittsburgh, 33:129-139.

Reid, B. 1965. The Adelie Penguin iPygoscelis udeliae) egg. New Zealand J. Sci.,
8:503-514.

Romanoff, A, L., and A. .1, Romanoff. 1949. The avian egg. John Wiley and Sons,
New York.

Simpson, G. G., A. Roe, and R. C. Lewontin. 1960. (Quantitative zoology. Harcourt,
Brace & World, Inc., New York.

Welty, j. C. 1962. The life of birds. A. A. Knopf, New York.

DEPARTMENT OF ORNITHOLOGY, AMERICAN MUSEUM OF NATURAL HISTORY,
NEW YORK, NEW YORK 10024. (PRESENT ADDRESS: ( C.T.C. ) DEPARTMENT

OF BIOLOGY, CALIFORNIA STATE COLLEGE, LONG BEACH, CALIFORNIA 90801),
16 JULY 1971.

NEW LIEE MEMBER

A new Life Member of the Wilson
Society is Dr. Ronald A. Ryder, Professor
of Wildlife Biology at Colorado State
University, Ft. Collins, Colorado. Dr. Ryder
holds two degrees from Colorado State and
has his doctorate from Utah State Uni-
versity. He is the author or co-author of
more than 60 scientific papers on a wide
variety of subjects. His professional in-
terests have centered on waterfowl, raptors,
and grassland birds. He is an Elective
Member of the AOU, and a member of
the Cooper Society, Western Bird-Banding
Association (Past President), The Wildlife
Society, Sigma Xi, Society of American
Mammalogists, and several other conser-
vation societies. Dr. Ryder is married and
has two children, and as is typical of most
of the professional members of the Society,
his hobbies also center around wildlife and
other outdoor activities. Many members of
the Society will remember Dr. Ryder as the
efficient Chairman of the Local Committee
for the 1970 joint meeting with the Cooper
Society at Et. Collins.

THE ROLE OF AVIAN RICTAL BRISTLES

Roger J. Lederer

IT has long been assumed by many workers that rictal bristles are char-
acteristic of insectivorous birds and are employed as accessory food-
capturing structures (Welty, 1962; Van Tyne and Berger, 1965). Others have
said that the bristles serve a tactile function (Kiister, 1905; Chandler, 1914;
Stresemann, 1934; Wallace, 1955; Pettingill, 1970). No convincing evi-
dence has been gathered to date to demonstrate the actual function of these
bristles but it appears that their use as an insect scoop is negligible or non-
existent.

Facial bristles are modified hairlike feathers which may run along the rictal
region as rictal bristles in many diverse groups of birds such as the Apterygi-
dae, Caprimulgidae, Aegothelidae, Mimidae, Accipitridae, and Tyrannidae.
They may also encircle the eyes as eyelashes and lie over the top of the bill
as loral bristles in numerous species. Facial bristles are fairly stiff, tapering
to a point at the end and there may be barbs present on the rachis ( Fig. 1 ) .
Filoplumes are hairlike also, but the shaft is weak and naked except for the
tip which has a few barbs. The distribution, length, and number of bristles
vary widely among species.

One function proposed for these structures is sensory, analogous to vibrissae
in mammals. Kiister (1905) reported finding avian lamellar corpuscles at the
base of the rictal bristles in some owls. Kiister suggested that the bristles
may react to sound waves and that they are similar to mammalian tactile hairs.
Schildmacher (1931) reported finding pressure-sensitive corpuscles at the
base of many feather-types.

Chandler (1914 ) proposed that rictal, as well as other facial bristles, cover
the face where ordinary feathers would be subject to excessive wear and tear.

Seemingly the most obvious application of rictal bristles is as an aid to
in-flight feeding by facilitating prey capture. Theoretically, a bird which
captures insects in flight would be benefited by stiff hairlike structures posi-
tioned about the bill in such a way as to form a funnel and thus giving the
bird a larger effective gape, providing a more efficient capturing mechanism.
It seems that the bird would only have to make some minor head movements to
implement the device. However, this appears not to be the case.

A cursory examination of a number of bird families indicates that there is
little or no relation between the })resence, dimensions, or number of facial
bristles and a tendency towards aerial feeding or insectivorous habits. The
Tyrannidae, Parulidae, and Ca|)rimulgidae. for example, capture flying
insects and j)ossess well developed rictal bristles. But the Mimidae. 3'iirdidae,

19B

194

THE WILSON BULLETIN

June 1972
Vol. 84, No.

Fig. 1. Cluster of rictal bristles of the Alder Flycatcher ( Empidonax traillii) . Seven
millimeters in length.

Icteridae, Corvidae, and Apterygidae (Kiwi), which are somewhat insectiv
orous, yet rarely, if ever (the Kiwi, never), feeding in flight, also possess
well developed bristles.

Figures 2 and 3 are examples of bristle arrangement in two species with

Dorsal

Fig. 2. Dorsal and lateral views of the head of E. traillii, showing the number and
arrangements of facial bristles. Length of skull is 31 mm, width at widest point is 22 mm.

Rojier J.
Lederer

ROLE OF RICTAL BRISTLES

195

%

Fig. 3. Dorsal and lateral views of the head of the Brown Thrasher (Toxostoma
rufum) , showing the number and arrangement of facial bristles. Length of skull is 61
mm, width at widest point is 36 mm.

different feeding habits. The Alder Flycatcher (Empidonax traillii) forages
I! by sitting erect on a low perch, watching for an insect to fly by, occasionally
! flying out to capture one, and returning to the same perch or one nearby
' (Bent, 1942; personal observation). The Brown Thrasher {Toxostoma
rufum) forages in the ground litter by poking with its bill for insects, seeds,
and berries; frequently the bill is thrust into the ground in search of prey
(Engels, 1940). If there is any relation between the arrangement and/or
number of rictal bristles and feeding behavior in these two species, it is not
apparent.

I have direct evidence that, at least in several tyrant flycatchers, rictal
bristles perform no function associated with prey capture. With the use of a
high-speed motion picture camera, I photographed mid-air captures of flesh
r flies iSarcopha^a bullata) by the Crested Flycatcher [Myiarchus crinitus) .

I Eastern Phoebe {Sayornis phoebe). Eastern Wood Pewee {Contopiis virens) ,

I and some Empidonax species which could not be identified in the film. The
I films were taken while the birds were confined in a large glass-fronted cage
j into which the flies were introduced. Photographs were taken at the rate
I of 375 frames per second and analyzed on a stop-action jirojector. Over 30
sequences of prey capture were recorded and in every instance in which a
I capture or near-capture was made, the insect was caught between the tips of
' the mandibles.

Phe prey are captured in the hill tips, rather than farther hack in the mouth

i

196

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

as would be the case if rictal bristles were utilized. Observation indicates that
flycatchers normally seize their prey with a rapid closure of the bill, fre-
quently resulting in an audible “snap."’ The upper mandible of these birds also
forms a distinct downward hook at its anterior end (Fig. 2). It appears that
this hook is an aid to seizing and holding prey. My observations in the field
and laboratory both indicate that mid-air captures of insects by flycatchers
occur as follows: a ) The bird approaches the insect with jaws agape; b) when
the tips of the mandibles are in close proximity to the prey, the jaws begin
to close; c ) the jaws close rapidly, trapping the prey in the bill tips.

I suggest that flycatchers and probably other birds with similarly shaped
bills that catch insects in flight, do not use their rictal bristles in the process.
Non-aerial feeders probably do not use their bristles in feeding, at least not
for prey capture. Some birds which are aerial feeders but have very different
bills, such as goatsuckers, swallows, and swifts, have a large gape. They
probably do not use bristles in prey capture, although I would not exclude
this possibility.

It appears as if the use of rictal bristles as an aid to aerial prey capture
by arthropod-eating birds has been casually accepted without definitive evi-
dence.

The most logical explanation for the presence of rictal bristles is that
they perform some sort of sensory function. Further investigation is obviously
warranted.

SUMMARY

Proposed explanations for rictal bristles are tliat they perform tactile functions, serve
as an insect scoop, or protect other facial feathers. In the Tyrannidae, at least, motion
pictures indicate that they do not play a part in prey capture.

ACKNOWLEDGMENTS

I would like to thank Drs. T. H. Frazzetta, S. C. Kendeigh, M. F. Willson, and Mr. D.
Schemske for their helpful comments on the manuscript. The Zoology Department at
the University of Illinois provided funds for photographic equipment and supplies. Miss
A. Boatwright kindly rendered the drawings.

LITERATURE CITED

Bent, A. C. 1942. Life histories of North American flycatchers, larks, swallows, and
their allies. U. S. Natl. Mus. Bull., 179.

Chandler, A. 1914. Modifications and adaptations to function in feathers of Circus
hudsonius. Univ. California Publ. Zook, 11:329-3%.

Engels, W. L. 1940. Structural adaptations in the thrashers with comments on inter-
specific relationships. Univ. California Publ. Zook, 42:341-400.

Kuster, E. 1905. Die Innervation und Entwicklung der Tastfeder. Alorphok Jahrb.,
34:126-148.

Roger J.
Lederer

ROLE OF RICTAL BRISTLES

197

Pettingill, 0. S., Jr. 1970. Ornithology in laboratory and field. Fourth ed. Burgess
Publishing Co., Minneapolis.

ScHiLDMACHER, H. 1931. Untersuchungen iiber die Funktion der Herbstschen Kdr-
perchen. J. OrnithoL, 79:374-415.

Stresemann, E. 1927-1934. Aves. In Kiikenthal u. Krumbach, Handbuch der Zoologie.
Volume 7, Part 2. Walter de Gruyter, Berlin.

Van Tyne, J., and A. J. Berger. 1959. Fundamentals of ornithology. John Wiley and
Sons, Inc. New York.

Wallace, G. J. 1955. An introduction to ornithology. Macmillan Co., New York.
Welty, j. C. 1962. The life of birds. W. B. Saunders Co., Philadelphia.

DEPARTMENT OF ZOOLOGY, UNIVERSITY OF ILLINOIS, URBANA, ILLINOIS 61801,

9 JUNE 1971.

PUBLICATION NOTES AND NOTICES

Families of Birds. By Oliver L. Austin, Jr. Illustrated by Arthur Singer. Golden
Press, New York City, 1971: 4x6 in., 200 pp. Many illustrations in color. Paper
' cover $1.95, hard cover $5.95.

An attractive reference book that provides thumbnail sketches of all known orders
I and families of birds, both living and fossil. A surprising amount of information is
contained in a small space. The illustrations, generous in supply, depict species that are
i typical of their families; they are nicely executed and well printed, and are real aids
in characterizing the families. This guide “is designed for those who have familiarity
with birds and who would like to known more about their relationships to one another.”
Distribution, characteristics, and habits are adequately summarized within the limits
j of the book, but very little is said about relationships. Nevertheless this guide can serve
I well as a handy reference tool for ornithologists. — P.S.

Native Birds of Mt. Desert Island and Acadia National Park. By James Bond. The
Academy of Natural Sciences of Philadelphia, 1971: 5x7 in., paper covered, v + 28
pp. $1.50.

This is the second revised edition of an annotated list of the 138 species of birds that
are known to breed or to have l)red on Mt. Desert Island and adjacent islands, Maine,
during the past 40 years. It is primarily a guide to bird finding in this ornithologically
' well known area but also gives remarks on tbe historical status of species. — P..S.

I Native and Winter Resident Birds of Tobago. By James Bond. The Academy of
' Natural Sciences of Philadelphia, 1970: 4 x 7 in., paper covered, v + 30 pp. $1.50.

An annotated list of the nearly 200 species of birds reported from Tobago. 'Fliis island
on the continental shelf of South America has a much richer avifauna than any of
\ the other Antilles of comparable size. Six excursions for finding birds are suggest(“d.
j The booklet gives aid for identification of indigenous and South American spt'cies but
! it is intended to be used with a field guide. Ih.S.

I

I

GENERAL NOTES

Probable Bulwer’s Petrel off Key West, Florida. — I observed a small, all dark
petrel with a long wedge-shaped tail that I identified as a Bulwer’s Petrel (Bulweria
bulwerii) off the Florida Keys, about 15 miles east-southeast of Rebecca Light on 14
May 1969. Rebecca Light is west of Key West, approximately two-thirds of the distance
to the Dry Tortugas, from which islands we were returning at the time.

One of a group of three petrels flew in to within 50 feet of our boat and stayed along-
side for almost a minute. It was a uniform brownish-black with a somewhat lighter
brownish band across tlie upper surface if its wings. Its flight was more like a shear-
water than a storm petrel. It did not have the latter’s fluttering flight, but rather had
a gliding flight and used its wings only sparingly and then only in short bursts. In
size, this bird was much smaller than Audubon’s Shearwater (Puffinus Iherminieri) ,
several of which we had seen only a few minutes before, and larger than the storm petrels,
even than the Black Petrel ( Loomelania melania) . While I realize that size comparisons
based on non-contemporaneous sight records are open to some question, I had seen
Black Petrels less than three weeks earlier when three of them followed our ship from
the Gulf of Panama toward the Galapagos for two days.

Dr. George E. Watson of the Smithsonian Institution, who concurs with my identifi-
cation, adds “In the Atlantic Ocean the Bulwer’s Petrel breeds only on Madeira and
the Cape Verde Islands but regularly, it seems, migrates south and west toward the
Americas. It has been recorded in the Caribbean and may even be a regular migrant
in the southeast Caribbean and near Trinidad. Many more observations are needed from
that part of the Caribbean to establish any regular pattern of occurrence (if indeed a
pattern exists). Your observations near the Tortugas, however, may only be regarded as
extraordinary vagrants.”

The 1957 edition of the A.O.U. Check-list in its Hypothetical List contains an old
and uncertain record of the Bulwer’s Petrel from Greenland. Until such time as a
specimen or photograph of this bird can be obtained for North America, it must remain
as a hypothetical. — Joseph W. Taylor, 20 Parish Road, Honeoye Falls, New York 14472,
19 November 1971.

Spring migration of the Gannet in Florida waters. — The Gannet {Moms bas-
sanus) is a regular winter visitor to Florida waters (Sprunt, Florida bird life, Coward-
McCann, New York, 1954, p. 17), but little is known of its spring migration. Palmer
(Handbook of North American Birds, 1:308, 1962) reports that spring migration begins in
March with the majority of birds gone from Florida waters by about mid-April. The
earliest dates of migration for Florida are 3 March off the east coast at Cocoa (Steven-
son, Audubon Field Notes, 12:273, 1958) and 15 March off the Gulf coast at Alligator
Point, near Panacea (Stevenson, Audubon Field Notes, 9:252, 1955) but these birds
may not have been migrants. The latest dates are 2 June at Alligator Point (Cunningham,
Audubon Field Notes, 20:497, 1966) and 27 June about 12 miles northwest of Key West
(Sprunt, Auk, 65:315, 1948).

Palmer (op. cit. :308) states that for the first three years Gannets stay at sea all year.
Thomson (Brit. Birds, 32:286, 1943) reports that some young, non-breeding British
Gannets remain in African waters, the winter range of the population, throughout the
breeding season. I know of no records of Gannets of any age in Florida waters for
July and August. Several observers have described a correlation between the age of
Gannets and the time of migration. Cruickshank (Birds around New York City, Amer.

198

June 1972
Vol. 84, No. 2

GENERAL NOTES

199

Mus. Nat. Hist., 1942) notes that in the New York area the majority of the early migrants
are in adult plumage, and the majority of the later migrants are younger. Wodzicki and
Stein (Emu, 58:296, 1958) note the same correlation for New Zealand Gannets. Steven-
son (Audubon Field Notes, 12:273, 1958; 13:286, 1959) reports that adult-plumaged
birds outnumbered younger birds in migration on two occasions in March off the east
coast of Florida.

During the spring of 1971 I recorded Gannet movements and plumages in the Straits
of Florida about 5 miles southeast of Marathon, Key Vaca, where on three occasions
small, compact flocks were seen flying steadily northeast low over the water. No fishing
or other activities were noted. The 70 Gannets I observed flew over water 75 to 100 feet
deep near a reef parallel to the Florida Keys. Water depth increases rapidly seaward
of the reef into the Straits of Florida. On 28 February 44 adult-plumaged Gannets were
seen moving northeast in flocks of two to seven at the rate of nine birds per hour.
On 4 April 23 Gannets, 18 adult-plumaged and five subadult and immature-plumaged,
were seen moving northeast at the same rate. The largest flock was five. On 10 May
three Gannets, one subadult and two immature-plumaged, were seen flying northeast at
the rate of two birds per hour. No Gannets were seen during three subsequent trips on
17 and 31 May and 7 June.

These observations indicate that Gannet migration off Florida has begun by late
February, which is earlier than previously supposed, and terminates in May. Further-
more, my observations indicate that adult-plumaged birds begin migration at an earlier
date than subadults and immatures, with a mixing of age classes in April. That the
Gannets followed the reef edge and avoided deep water suggests they are offshore and
not pelagic birds. This may explain the lack of records of the species in the West
Indies (Bond, Check-list of birds of the West Indies, 1940 and supplements) even though
they occur annually in the southern Straits of Florida. This offshore habit is characteristic
of other Gannet populations (Thomson, op. cit.: 283-284 ) , although New Zealand Gannets
are known to migrate over sea from New Zealand to Australia by crossing the Tasman
Sea and to Indian Ocean pelagic waters (Wodzicki and Stein, op. cit. :289).I wish to
thank Dr. William B. Robertson, Jr. of the U. S. National Park Service and Dr. Glen E.
Woolfenden of the University of South Florida for helpful suggestions on improving
this manuscript. — Terry C. Maxwell, CMR Box 7248, Homestead AFB, Florida 33030
(Present Address: 1025 Cactus Lane, San Angelo, Texas 76901), 10 July 1971.

Aerial feeding in the Snowy Egret. — The Snowy Egret (Leucophoyx thula) is
well known for its diversified feeding behavior. Catching aquatic prey while in flight
has been noted by several authors. Bond (Auk, 51:500-502, 1934), Sprunt (Auk, 53:203,
1936), Grimes (Auk, 53:439, 1936) and Meyerriecks (Wilson Bull., 71:153-158, 1959)
described a feeding behavior which Meyerriecks (op. cit.: 154) called “hovering-stirring.”
An egret so engaged hovers near the water and with one or both feet agitates the water
or stirs vegetation or del)ris beneath it. I have observed Snowy Egrets using hovering-
stirring on several occasions in southern Florida. I have also witnessed a different method
of aerial feeding which may he called “foot-dragging.” Employing this techni(iue, an egret
flies just above the water with legs dangling beneath. It drags the toes of both feet
through the water and takes prey from the water while in direct flight without hov(*ring.
I have only seen small organisms taken during such behavior and these were swallowed
while the bird was in flight. A third type of aerial feeding has been not(>d hy Dickinson
(Auk, 64:306-307, 1947) and Jenni (Ecol. Monogr., 39:258, 1969) who n'ported Snowy
Egrets feeding in direct flight hut without dragging their feet.

200

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

I first observed foot-dragging on 22 March 1969 at a pond in the Big Cypress Swamp
of southern Florida. Additional observations were made at Mrazek Pond in Everglades
National Park on 10 December 1970. Certain conditions prevalent during the first
series of observations are pertinent in accounting for the use of such active feeding tech-
niques.

The pond, 0.25 hectares in area, is composed of two vegetation zones — a peripheral area
of emergent grass ( Paspalium spp.) and a central area which during periods of high
water is filled with submerged naiad {Najas flexilis) . During intervals of low rainfall,
the water level in the Big Cypress Swamp drops. Fish and other aquatic organisms
become concentrated within the pond from the surrounding swamp and marshlands.
If low water levels occur at the proper time, these organisms provide a highly con-
centrated food source for numerous herons, storks and ibises which then frequent the pond.
The feeding aggregation of wading birds and other aspects of the ecology of this pond
were described by Kushlan ( An ecological study of an alligator pond in the Big Cypress
Swamp of southern Florida. M.S. Thesis, University of Miami, Coral Gables, Florida.
1972, 197 pp.). On 22 March 1969 herons began to arrive at the pond at 06:10 just
after first light. Snowy Egrets first flew into the pond at 06:17 and began to feed im-
mediately; by 06:45, 450 Snowy Egrets were feeding there. These birds were dispersed
throughout the shallow emergent zone where they stood upon the trampled grass and
used stand and wait feeding behavior exclusively. By 07:00 many herons including
several hundred Snowy Egrets had left the pond. At 07:15 one Snowy Egret began
feeding using foot-dragging behavior while flying from one side of the pond to the
other. On each pass it flew low over the grass and upon reaching the open water of the
central area it began to drag its feet in the water continuing this for the length of the
pond — a distance of approximately 30 meters. Four other Snowy Egrets joined the
first and these birds fed in this manner for 10 minutes. Meanwhile other Snowy Egrets
continued to stand in the grass and although some successfully captured prey most did
not attempt to feed.

In this instance stand and wait behavior was used early in the morning when the
oxygen concentration of the water is lowest and fish are concentrated near the surface of
the pond (Kushlan, op. cit.). Snowy Egrets began to use tbe more active technique
when fish were less available and, from qualitative observation, success using stand
and wait behavior was limited. These observations support the contention of Meyerriecks
(Nat. Hist., 71:57, 1962) that such active feeding methods are resorted to when other
methods fail or when other areas of habitat are not productive. Further evidence is
derived from observations of Louisiana Herons ( Hydranassa tricolor) at the pond.
Few were present in 1%9 during the period when the wading bird aggregation actively
utilized the pond. However several fed in the pond on 30 March 1969 after the activities
of wading birds had reduced fish density (Kushlan, op cit.). At that time Louisiana
Herons along with Snowy Egrets fed by hovering-stirring almost exclusively. — James A.
Kushlan, Department of Biology, University of Miami, Coral Gables, Florida 33214, 4
October 1971.

Observations on the status, ecology, and behavior of Soras wintering in Trini-
dad, West Indies. — Tbe Sora (Porzana Carolina) winters from the southern United
States to northern South America, but it has been considered rare on Trinidad, West
Indies (Leotaud, Oiseaux de I’lsle de la Trinidad, 1866, p. 495; Herklots, The birds of
Trinidad and Tobago, Collins, London, 1%1, p. 74). Belcher and Smooker (Ibis, 1935:
279-297, 1935), who found most of the other species of rails known from the Island,

June 1972
Vol. 81, No. 2

GENERAL NOTES

201

never eollected the Sora, although they did attribute to this species a nest, on which
basis they hypothesized the existence of a local breeding race. Although the egg measure-
ments they list do fall within the size range reported for the Sora by Bent (U.S. Natl. Mus.
Bull., 135:305, 1926) no such race has been discovered, and the measurements also
match those given by the same authors (op. cit.) for Laterallus exilis.

From February to May 1965, I studied the ecology of a freshwater impoundment on the
northeastern edge of the Caroni Swamp in Trinidad, and during this time I saw and
heard many Soras. My observations were made only during the dry season. 1 first
observed Soras foraging on exposed mudflats among the extensive beds of rushes
{Cypressus articulatus and Eleocharis mutata) , and later flushed them from these
rushes wherever there was standing water. I occasionally flushed Soras from the dense
stands of the emergent arum iMontrachardia arborescens) on the banks of the Caroni
River itself, but I did not find them among the lower emergent vegetation such as water
hyacinth (Eichornia crassipes) and a “morning glory” {Ipomea aquatica) which were
frequented by the smaller Yellow-breasted Crake iPorzana flaviventer) . This latter
species, only recently reported from Trinidad, (ffrench and ffrench, Wilson Bull.,
78:5-11, 1966), was also common in the marsh.

As the dry season progressed, more and more of the marsh was left without standing
water, and the Soras moved into the remaining wet areas with taller vegetation (up to
1.2 meters) which they had previously shunned. The same shift in habitat was noted for
the Common Gallinule (Gallinula chi or opus) , Wattled Jacana ijacana jacana) , and
Stripe-backed Bittern (Ixobrychiis involucris) , hut not for the Spotted Rail (Rallus
maculatus) nor Yellow-breasted Crake which are perhaps more tolerant of drier condi-
tions.

Several authors (Bond, Birds of the West Indies, Houghton Mifflin Co., Boston, 1961;
Slud, Bull. Amer. Mus. Nat. Hist., 128:84, 1964; and Wetmore, Smithsonian Misc. Coll.,
150:350, 1965) have indicated that the Sora is not very vocal on its wintering grounds, and
Soras which I observed elsewhere in the West Indies were, indeed, silent. On Trinidad,
however, I often heard spontaneous calls which I attributed to Soras. Two notes, a brief
nasal ka and a more plaintive peeyanh ending with a rising inflection were similar to
call notes I have heard from Soras on their breeding grounds. Once in April I heard
the typical “whinny” call. The size of the wintering Sora population was estimated
from the number of birds flushed while walking transects through the marsh, from the
number of spontaneous calls, and from calls elicited by exploding firecrackers. I
estimated that no fewer than 40 and perhaps 50 to 80 Soras were present in 26 hectares
of marsh. Of the birds seen well two-thirds were in immature plumage. Soras were
encountered on all 15 visits from 25 February to 24 April, but despite careful coverage
none were found on 4 visits from 30 April to 6 May. The maximum daily count was
30 birds on 20 March, hut this probably reflects unusually extensive coverage rather than
an influx of northbound migrants from South America. No birds were collected so
information on stomach contents is not available, hut on one occasion a Sora was ol)-
served apparently feeding on small gastropods adhering to the emergent vegetation.—
Michael Gociifeld, Department of Ornithology, American Museum of Natural History,
New York, New York 10024, 16 March 1971.

Young Common and Roseate Terns learning to fish. — TIh'k* is very little in-
formation in the literature on young terns learning to fish for themselv(*s. Palmer ( Proc.
Boston Soc. Nat. Hist., 41:93, 1941 J ohserv('d the young birds following the adults in

202

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

flight and returning to shore to l)e fed, but he was unable to observe the changeover
to self-feeding. Tomkins (Wilson Bull., 71:320, 1959) noted that in the Least Tern
flying young accompany the adult, who catches a fish and alights on the water to give
it to the young. In view of the scarcity of information on this critical period, observations
I made on Great Gull Island, Suffolk County, New York, may be of interest.

On 29 September 1%9, in the mouth of the Thames River at New London, Connecticut,
about 7 miles north of Great Gull Island, many terns were resting on the exposed rocks
and old pilings near shore. One juvenile Common Tern (Sterna hirundo) was begging
with head directed upward, apparently toward an adult overhead. The young bird flew
suddenly upward, circled once and landed on the water. The adult landed in front of
the chick and put its bill into the water. The young bird, very close in front of the adult,
put its bill into the water, then raised it and swallowed a fish. The adult had apparently
passed a fish to the young under water.

On 26 September 1970, after most of tbe terns had left Great Gull Island, I noticed
four Common Terns fishing near the western end of the island. There were two adult-
juvenile pairs, as Tomkins (loc. cit.) reported for the Least Tern. For approximately 10
minutes I observed the adults skimming, diving, flying just above the surface and cir-
cling the area; they were closely followed in these maneuvers by the young. Fish must have
been abundant and near the surface as both adults caught fish easily. After about 10
minutes the original four birds were joined by another adult — young pair of Common Terns
and by an adult — young pair of Roseate Terns (S. dougallii) . These eight birds continued
the follow-the-leader actions described above for another 20 minutes before leaving the
vicinity of the island.

During the 30 minutes of observations the young terns were never seen to actually
enter the water, always halting their dives abruptly just short of the surface, nor were
they seen to catch a fish. Once an adult caught a fish and flew up with it until it was
in front of the young, dropped it and caught it again before it had fallen more than a
few feet. While adult terns do occasionally drop fish and catch them in this manner, it
seemed significant that the adult flew to the young before dropping the fish.

A Common and a Roseate Tern caught as downy chicks and offered live killifish
regularly for several weeks in captivity, watched the live fish from a distance but never
ate one, although both learned to eat cut up fish from a bowl. This behavior and the
observations reported above lead me to believe that the young tern must learn to
respond to living fish as an item of food and must then learn and perfect the technique
for catching them. Presumably the learning period is lengthy. Hays and Donaldson in a
study of post-breeding dispersal (in prep.) report a young Common Tern nine weeks of
age being fed by an adult. Partial dependence on the parents may extend even to the
wintering quarters (Ashmole and Tovar S., Auk, 85:90-100, 1%8) especially for chicks
hatching late in the season.

I would like to thank Dean Amadon and Helen Hays for comments on the manuscript.
— Mary LeCroy, Department of Ornithology, The American Museum of Natural
History, New York, N. Y. 10024, 26 July 1971.

Lek behavior in the Broad-tailed Hummingbird. — I recently observed behavior
in the Broad-tailed Hummingbird (Selasphorus platycercus) which I interpret as com-
munal male displays, or lek behavior. These observations were made daily from 11-14
June 1971 at Moraine Park in Rocky Mountain National Park, Colorado, at an elevation
of about 8,000 feet. I observed three male Broad-tailed Hummingbirds performing their

June 1972
Vol. 81, No. 2

GENERAL NOTES

203

characteristic U-shaped climbing and diving display flights along a steep, semi-wooded
hillside of ponderosa pine. The three birds were separated from each other by about
7 meters and while I was unable to recognize individuals, identical locations were oc-
cupied on each of the four consecutive days. During these four days, I observed the
display performance for a total of seven hours, during which time a single female ap-
proached to within about 2 meters of one of the end males on the second day (12 June).
She remained quietly on a branch for 55 seconds and remained within sight of the
display area, with occasional brief departures, for 39 minutes. At no time did she asso-
ciate directly with any of the males, beyond her initial, brief approach.

The appearance of the female resulted in an increase in the frequency of courtship
flights by each of the three males: I obtained a group mean of 4.8 seconds per complete
display circuit per individual (n r= 18, s.d. = 0.8) from arbitrarily-chosen samples
during a ten-minute period beginning 15 minutes after the female’s departure and a group
mean of 3.5 seconds per display (n = 11, s.d. =: 0.6) while the female was in the im-
mediate area. The differences were significant (p<0.01, f-test) . An equivalent increase
in display “intensity” upon arrival of females has been reported for the gallinaceous lek
species.

I observed seven aggressive incidents among the three displaying males. Six of these
were obviously initiated by the arrival of one male in the immediate vicinity of another.
In all these cases, the intruding male retreated to his own display area following a brief
confrontation in which the victorious proprietary male flew quickly at the intruder and
then hovered immediately in front of him. In two cases, this was followed by a brief,
mid-air scuffle lasting less than 3 seconds, while in the remaining four incidents, the
intruder retreated immediately following this mid-air encounter. The seventh aggressive
incident occurred in apparently “neutral” territory, following which both participants
returned to their display areas with no obvious victor.

Isolated male-female courtships may still be the rule in the Broad-tailed Hummingbird.
Thus, I observed four other examples of male courtship displays in which there was a
female nearby and no other males were apparent. The frequency of display at this time ap-
peared to be greater than in the lek with the female absent but lower than in the lek with
the female present. It may also be significant that I never observed isolated males display-
ing in the absence of a female, while the three lek males described above displayed steadily
with no female present.

I believe this to be the first report of lek behavior in a North American hummingbird.
Possible selective advantages of lek behavior include providing greater stimulation to

the female and hence increasing the probability of a successful mating by one of the

participating males, possible stimulatory effects on the males themselves — hence result-
ing in a greater probability of a successful mating than if each were courting indepen-
I dently, greater range of selection for the female with a minimum of energy expenditure

. and/or facilitating location and recognition of males. Balanced against this would be

the possible disadvantages of attracting greater numbers of predators to a commonly-
used display area and the evolutionary disadvantage to individual males which may be
consistently discriminated against in favor of a possible “master” within each lek.

These observations were made while conducting research supported by the Kesearch
Foundation of the State University of New York, the Theodore Roosevelt Memorial
Fund of the American Museum of Natural History and The Society of the Sigma Xi. —
David P. Barash, Biology Department, State University College, Oneonta, New York-
13820, 8 October 1971.

204

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Evitleiice of two Tree Swallow females sharing the same nest hox. — On 13 June
1971, I observed eight eggs in a Tree Swallow (Iridoprocne bicolor) box, located in John
F. Kennedy Memorial Wildlife Refuge, 6 miles south of Massapequa, Nassau County,
New York. As I opened the hox, I was able to capture and hand a bird believed to he
a female as it had a well developed brood-patch. A few hours later, I checked the hox
again and captured a different bird with an equally well developed hrood-patch, incu-
bating the eight eggs. I also handed this bird.

On 14 June there were five eggs and three young in the hox; on 16 June, as well as
on the following day, there were four eggs and four young; on 18 June, two eggs and
six young; and on 19 June there were eight young. On all these days three birds staunchly
defended the hox. On numerous occasions, I waited until one of the three birds entered
the nesting hox and then I walked over and trapped the bird inside. Each time it was
one of the two handed females. Once or twice the other two birds would alight on the
nesting hox when the third bird was inside.

The third bird was mist-netted and handed on 19 June, and had no evidence of an
incubation patch. Because the bird had had no incubation patch, and because it never
entered the hox I believed it to he a male. According to ( Kuerzi, Proc. Linnaean Soc.,
52-53:27, 1941) and (Low, Bird-Banding 3:2, 1932) under normal conditions the female
Tree Swallow incubates the eggs, and the male usually perches outside.

On 26 June all the young were found to he partially feathered, but on 5 July no young
were found in the box although the nest was intact.

The young did not seem to he hindered by the extremely crowded conditions in the
hox and the three adults (two females and one male) were always observed near the
hox. Although adjacent boxes were also occupied and were as close as 50 feet only at
this hox were there three birds defending the nest. In four years of Tree Swallow
study in this area, this was the first occurrence of more than six eggs (Schaeffer, EBBA
News, 34:216-222, 1971). There is mention of four seven egg clutches (Paynter, Bird-
Banding, 25:35-58; 102-110; 136-148, 1954). Yunick (Kingbird, 21:47-56, 1971) men-
tions two cases of eight egg clutches and in one of the cases there were two different egg
shapes, pointing to a suspicion of two separate layings. Bent ( Life histories of North Amer-
ican flycatchers, larks, swallows, and their allies, 1942) , mentions two males and one female
using the same hox hut makes no mention of two females and one male. It is possible that
this is a case of two females sharing a nest because all the other boxes in this general area
were taken; however, it is also possible that this is an isolated case of polygny, hut other
than the above I cannot offer solid evidence. I did not observe copulation between the
male and any other bird because no visits were made to the Refuge during the appropriate
time period. — Harvey Farber, 112-50 78th Avenue, Forest Hills, New York 11375, 22
September 1971.

Steller’s Jays prey on Gray-headed Juncos and a Pygmy Nuthatch during
periods of heavy snow. — Members of the family Corvidae are typically omnivorous in
their feeding habits, their diet consisting primarily if fruits, grains, berries, insects and oc-
casionally eggs and nestlings of various small birds. There are also several reports in the
literature of the unexpectedly high frequency of Blue Jay ( Cyanocitta cristata) preda-
tion on red hats (Lasiurus borealis) (see D. F. Hoffmeister and W. L. Downes, South-
western Naturalist, 9:102, 1964). Roth (Condor, 73:113, 1971) has recently reported
an account of the Mexican Jay ( Aphelocoma ultramarina) attacking and killing a small
sparrow under conditions of heavy snow in southeastern Arizona.

Observations at feeding stations in Flagstaff, Coconino Co., Arizona, inhabited through-

June 1972
Vol. 84, No. 2

GENERAL NOTES

205

out the winter by juncos and Steller’s Jays (Cyanocitta stelleri) have been made for
several years. During periods of mild weather, jays and juncos show no antagonistic
behavior toward each other, but during periods of extended cold weather and/or snow the
presence of jays at the feeders is sufficient to keep juncos out of the immediate area.

In late December of 1970 Dr. and Mrs. Edwin H. Colbert observed a Steller’s Jay
capture and partially consume an adult Pygmy Nuthatch (Sitta pygmaea) . A large flock
of nuthatches had been attracted to a suet feeder near the Colbert house. An individ-
ual nuthatch flew into an open area in a large stand of pine (Pinus ponderosa) and
was about 10 ft off the ground when a jay that had been perched on a branch in a
nearby tree, swooped down on the nuthatch catching it in mid-air with its feet. The
jay then flew hack to its perch and as Dr. Colbert observed through binoculars, the
jay used its beak to pluck and kill the nuthatch, holding it down with one foot while
grasping the perch with the other. When the jay was approached it flew off into a
deeper portion of the woods still clutching the dead nuthatch in its feet.

Another incident of Steller’s Jay predation occurred on 20 February 1971, when
during a heavy snowfall a jay was observed (Baida) attacking an adult Gray-headed
Junco ijunco caniceps) . The jay dove down to a platform feeder and caught the junco
with its feet; it then flew about 40 ft to a perch in a pine where it proceeded to pluck
and eat portions of the smaller bird. When the jay was approached it dropped the
partially eaten carcass under the tree. Two days later when the snow began to melt, two
other dismembered and partially eaten carcasses of Gray-headed Juncos were discovered.
We believe these birds met their demise in the same manner as described above.

The weather preceding both of these incidents had been cold; the mean daily tem-
perature for December 1970 was 4°C, with -11°C being the mean low for this month.
Snow had fallen intermittently from 14 to 22 December, reaching a maximum depth of
53.3 cm by 22 December. The mean daily temperature for February 1971 was 7.3° C and
the mean low was -8.3°C. Snow had begun falling on 17 February reaching a maxi-
mum depth of 30.5 cm by 21 February ( U. S. Weather Bureau Records, 1970 and 1971,
Flagstaff, Arizona).

Although jays are known to hold food objects with their feet while tearing them apart
with their beak, we know of no other observation wherein a jay has been reported to
capture prey with its feet during flight. Whether or not Steller’s Jays make a habit
of consuming other bird species as a food source during times of limited food availability
is unknown. It is probable that during particularly harsh portions of the winter, lack of
suitable vegetable material and insects force the jays to exploit alternate food sources.
The facility with which the jays reported herein captured their unusual prey indicates
that this food source may he exploited by jays to a greater extent than was previously
thought. — Stevkn W. Carotheks, N. Joseph Shahber, Museum of Northern Arizona, Flag-
staff, Arizona 86001 and Russell P. Balua, Department of Biological Sciences, Northern
I Arizona University, Flagstaff, Arizona 86001, 1 October 1971.

Adult Carolina Chickadee carries young. — On rare occasions when nests are
i| disturbed certain species of l)irds have been known to pick up and move their eggs to
Ij different locations (Truslow, Natl. Geogr. Mag., 130:882-884, 1%6; Pettingill, Ornithol-
I ogy in laboratory and field, Burgess Puhl. Co., Minneapolis, 1970, p. 357). In addition,
Welty (The life of birds, Alfred A. Knopf, New York, 1962, p. 336) and Ih'ttingill
(op. cit.:392) consider at least 10 known instanc(‘s of non-passerine young Ix'ing picked
|| up and carried by tlndr parents. This type of IxJiavior is considered to he except i(>nal.

206

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

During the morning of 11 April 1971 we were examining a nest of a Carolina Chickadee
(Parus carolinensis) which was located 10 m from shore in a small excavated cavity of a
one meter-high post over the water of Cross Lake, near the western boundary of Shreve-
port, Louisiana. Due to a brisk wind the lake water was choppy so that some difficulty
was had in maintaining the boat against or near the post in order to see into the nest.
Because of the action of the waves, the post was jarred several times over a period of
several minutes. There were four newly-hatched chickadees in the nest. After leaving
the nest site, we saw an adult chickadee enter the nest and leave with something that
was pink in color. It carried the object over the shoreline and disappeared into a
grove of trees 50 m from the post. Shortly thereafter, the adult returned with what
appeared to be food and entered the nest. With the aid of binoculars we now saw the
adult leave the nest carrying a young bird. The bird flew in the same direction as the
first time, holding the young bird in the beak, which was positioned around the body
of the young bird. The additional two young were removed in the same manner. The
entire removal took place in about 30 minutes. When observed again, the nest was
empty of young and over a period of time the adult or adults did not reappear. Not
more than one adult was seen at any one time. The shore area, where the adult dis-
appeared with the young was searched but the new nest, if any, was not located.

In our observations of over 5,000 different nests that contained eggs or young, includ-
ing the nests of 125 Carolina Chickadees, in northern Louisiana since 1963, we have
never seen a parent bird carrying either its eggs or young, up to this time. — John W.
Goertz and Kim Rutherford, Department of Zoology, Louisiana Tech University,
Ruston, Louisiana 71270, 27 September 1971.

Habitat differences of Swainson’s and Hermit Thrushes. — Most Swainson’s
Thrushes {Hylocichla ustulata) along the coast of Maine nest in spruce forests; as a
result, they seldom if ever overlap with Wood Thrushes iH. mustelina) or Veeries IH.
fuscescens) in their breeding habits (see Morse, Wilson Bulk, 83:57-65, 1971). How-
ever, potential overlap does occur with Hermit Thrushes (H. guttata), and here I report
spatial relationships of these two species.

I censused populations of thrushes in spruce forests and mixed coniferous-deciduous
forests on islands in Muscongus Bay (Lincoln and Knox Counties), and the adjacent
mainland (Table 1). Techniques followed those prescribed in Audubon Field Notes for
l)reeding bird censuses.

In the absence of congeners the Swainson’s Thrush occupies a wider range of habitats
than it does in their presence, as demonstrated by its presence on small islands (par-
ticularly on Wreck and Haddock Islands) (Table 1). Further, while Swainson’s
Thrushes were absent from certain islands some years, no Hermit Thrushes used them
at these times (Table 1). Wreck and Haddock Islands support mixed forests of mountain
and striped maples (Acer spicatum and A. pennsylvanicum) , yellow birch (Betula lutea) ,
white spruee iPicea glauca) , and balsam fir (Abies balsamea) . They have been damaged
heavily by storms in some areas (described fully in Morse, Ecology, in press). Similar
areas on the adjacent mainland are occupied by other species of Hylocichla (Morse,
Wilson Bulk, 83:57-65, 1971). In spruce forests on large islands and the mainland,
Swainson’s Thrushes usually appear in denser growth than does the Hermit Thrush.
The spruce forests on Loud’s, Harbor, and Marsh Islands (Table 1) have smaller trees
(mean heights = 13-17 m) and denser growth than the mainland forests censused
here, in Morse (op. cit.), and the forest on Hog Island (Morse, Ecology, 49:779-784,

June 1972
Vol. 84, No. 2

GENERAL NOTES

207

Table 1

Distribution and Numbers of Breeding Thrushes, 1%7-1971.
Dash(-) indicates that area was not censused during a given year.

Study area

Size of forest %

( ha ) censused

Coniferous

Foliage

Pairs of
Hermit
Thrushes

00 o O
CD CD l>
Gi a Gi

1971

Pairs of
Swainson’s
Thrushes

t- 00 o o

CD CD CD !>
G^ G> Gi Gi

o

Sample study areas

in large forests (25 ha-\-)

Mainland

4.20

99

-

2

2

1

-

-

1 0

0

Hog Is.

4.50

99

-

-

1

1

1

-

-

1 0

0

Loud’s Is.

4.50

99

-

-

-

1

0

-

-

- 4

3

Harbor Is.

4.50

99

-

-

-

-

0

-

-

- -

5

Marsh Is.

2.40

99

-

-

-

0

0

-

-

- 2

1

Small forests {entire island censused)

Wreck Is.

3.86

55

0

0

0

0

0

2

2

1 2

1

Haddock Is.

1.86

61

0

0

0

0

0

1

0

0 1

0

Thief Is.

1.50

99

0

0

0

0

0

1

2

2 2

1

Indian Is.

0.69

85

0

0

0

0

0

1

0

0 0

0

Crane Is.

0.53

99

0

0

0

0

0

0

0

0 0

0

Jim’s Is.

0.49

90

0

0

0

0

0

0

1

0 0

1

Ram Is.

0.39

90

-

0

0

0

0

-

0

0 0

0

Crow Is.

0.35

60

0

0

0

0

0

0

0

0 0

0

Crotch Is.

0.16

98

0

0

0

0

0

0

0

0 0

0

Byer’s Ship Ledge

0.11

96

0

0

0

0

0

0

0

0 0

0

1%8) (mean heights = 19-21 m). Palmer (Bull. Mus. Comp. Zool., 102:1-656, 1949)
also reported that Swainson’s Thrushes frequented dense forests.

The expansion of Swainson’s Thrushes on small islands into habitats similar to those
occupied elsewhere by other Hylocichlas, combined with their absence in a wide variety
of habitats adjacent to the spruce forests in this area (see Morse, Wilson Bull., 83:
57-65, 1971), suggest strongly that they usually are excluded from these areas by con-
geners. The absence of Hermit Thrushes on the small islands, even during years when
several islands had no Swainson’s Thrushes, is consistent with the argument that Swain-
son’s Thrushes were not limiting the presence of Hermit Thrushes or other species on
these islands.

While Swainson’s and Hermit Thrushes use habitats somewhat differently, with
the former being a more arboreal forager than the latter (Dilger, Wilson Bull., 68:
171-199, 1956), considerable spatial relief appears necessary (either vertically as in
a tall forest, or horizontally as in the nature of blowdowns) for their coexistence.
Dilger considers the Hermit Thrush to be a bird of forest-edge situations, and the
Swainson’s Thrush to be a bird of forest interiors. In spruce forests of this area, wind
damage often produces a marked edge effect. Perhaps the largely undisturbed old-
growth spruce forests are open enough to provide these characteristics as well.

208

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

The basis for the absence of Hermit Thrushes from the outer islands is not clear,
hut it parallels the absence of certain warblers characteristic of spruce forests ( Morse,
Ecology, 52:216-228, 1971). In that case, however, forest-edge species occur on the
smallest islands supporting warblers ( Myrtle, Dendroica coronata, and Parula, Parula
americana. Warblers) ; in the case of thrushes the species typical of forest interiors
(Swainson’s) is the one present. The warblers found on the smallest islands are socially
subordinate species. Inadequate data exist upon social interactions of Hermit and
Swainson’s Thrushes to establish clearly the existence of a hierarchy. I have seen only
two encounters between these two species; in both cases Hermit Thrushes supplanted
Swainson’s Thrushes. Dilger (Auk, 73:313-353, 1956) does not report any interactions
between them. However, the habitat relationships of the two species are similar to those
of Wood Thrushes and Hermit Thrushes and Wood Thrushes and Veeries, where clear
social hierarchies exist (Morse, Wilson Bull., 83:57-65, 1971). These observations sug-
gest that Swainson’s Thrush is socially subordinate to the Hermit Thrush. The informa-
tion thus supports the argument that interspecific social relationships may be a major
determinant in deciding what species will occur in any given habitat. This interpreta-
tion is consistent with predictions made elsewhere (Morse, Annu. Rev. Ecol. Syst., 2:
177-200, 1971) that socially subordinate species will generally exhibit greater plasticity
than social dominants.

These observations were made while conducting research sponsored by the National
Science Foundation (GB-6071). — Douglass H. Morse, Department of Zoology, Uni-
versity of Maryland, College Park, Maryland 20742, 18 November 1971.

Breeding Status of the Purple Gallinule, Brown Creeper, and Swainson’s Warb-
ler in Illinois. — In view of the program to revise the American Ornithologists’ Union’s
1957 Check-list of North American Birds, the following comments on several species
in Illinois seem pertinent.

Purple Gallinule (Porphyrula martinica) . — In 1963 this species nested and raised
young at Lake Mermet, Massac County (Waldbauer and Hayes, Auk, 81:227, 1964) —
the first known instance of breeding Purple Gallinules in Illinois. However, in com-
pliance with the demands of boaters and fishermen, the water plants that made Lake
Mermet a suitable nesting locality for gallinules were removed during early spring of
1964. Gallinules reappeared at the lake soon after this occurred (John Schwegman,
pers. comm.) but departed without attempting to nest. Purple Gallinules are not
known to have nested in Illinois since.

Brown Creeper (Certhia familiaris) . — The 1957 A.O.U. Check-list does not mention
this species as a breeding bird in Illinois, which in the central and southern portions
of the state it undoubtedly is. Kendeigh (Audubon Bull., 153:19, 1970) cites various
bird watchers who report recent summering creepers from Piatt County southward to
the Ohio River-Mississippi River confluence near Cairo; one such report refers to a
nest with young.

I collected (W.G.G. No. 2254) a heavily molting juvenile female in a hemlock grove
near Cobden, Union County, on 20 August 1968. The bird exhibited a nearly wholly
unossified skull and no conspicuous fat deposits. Since the molt of young creepers is
completed prior to the fall migration and the migrants do not arrive in Union County
before the first week of October, the August juvenile strongly indicated the presence
of a local breeding population. Not surprisingly, then, a bird-banding project at Crab Or-
chard Lake Wildlife Refuge, Williamson County, which is close to Union County, yielded a
creeper with a brood patch in 1970 and another in 1971 (Kleen and Bush, Amer. Birds,

June 1972
Vol. 8-1, No. 2

GENERAL NOTES

209

25:750-753, 1971), while on 28 May 1971, I observed paired creepers near Pine Hills
Field Station, Union County.

Creepers probably colonized southern Illinois long ago, as indicated by Otto Widman’s
discovery (fide Pickering, Migrant, 8:49-50, 1937) of several nesting specimens in the
cypress swamps of southeastern Missouri in 1894 and 1898 ( records not heeded in the
1957 AOU Check-list) . Our Illinois birds seem adherents of the Missouri pattern,
being a handful of birds scattered widely about in the floodplain forest and cypress-
tupelo swamps.

However, it should be noted that in the eastern United States, the Brown Creeper ap-
pears at present to he expanding its nesting range southward and downslope in moun-
tainous regions (Hall, Redstart, 36:98-103, 1969) ; hence all or a proportion of our
Illinois birds may be participants in this phenomenon.

Swainson’s Warbler (Limnothylpis swainsonii) . — Of the various accounts of summer
occurrences of Swainson’s Warbler in Illinois ( Ridgway, Bull. Nuttall Ornithol. Club,
4:163, 1878; Howell, Auk, 27:216, 1910; Gross, Auk, 25:225, 1908; Hardy, Wilson
Bull., 67:60, 1955; Brewer, Audubon Bull., 106:9-11, 1958), none provides unequivocal
evidence of breeding. An adult female that I obtained accidently in a tree-shaded
canehrake along Cave Creek in the Shawnee National Forest near Pomona, Jackson
County, on 8 August 1966, is such evidence, the bird exhibiting a brood patch; and
more recently even nests have been found and young observed (see below).

The Cave Creek birds exist at the northern limits of the range of their own species
and of the cane (Arundinaria) with which the distribution and nesting of Swainson’s
Warbler appear closely correlated, except in the Appalachian Mountains (see Meanley,
Natural History of Swainson’s Warbler. N. Amer. Fauna 69, 1971, for a fine discussion
of this and related data).

John William Hardy (op. cit.) who with Richard Brewer first detected singing males
at Cave Creek in 1951 and revisited the site often during the early fifties, described
the canehrake as “extensive,” a statement no longer accurate because of reduction of
some cane stands and elimination of others. When Hardy introduced me to the area
in 1966, the canehrake was more or less as he remembered it, though a logging opera-
tion threatened the forest canopy along the creek. The logging largely has ceased; hut
during the past five years almost all large canes have been cut down by men col-
lecting cheap fishing poles and beanstalk supports. Today the two largest stands of
cane include fewer than 300 sq meters of ground each and contain almost no canes
greater than 1.5 cm in diameter at the base or 2.5 meters in height. One dense cane
thicket through which Hardy and I forced our way with some difficulty consists now
of only scattered thin-stemmed plants. Fortunately, an agreement to rescue this cane-
hrake from further dismemberment has been worked out between the property owner
(U. S. Forest Service) and the Department of Zoology at Southern Illinois University.

The Swainson’s Warbler population at Cave Creek varies in size from a single pair
in some years (see Hardy, op. cit.; Brewer, op. cit.) to two or at most three pairs. They
arrive in early May and I have seen bob-tailed fledglings in late June and large fledg-
lings still being fed by adults in early August. In 1971 I found two nests; each was
located in cane; one, abandoned prior to egg deposition, has been added (along with
the skin of the female warbler mentioned earlier) to the collections of the Museum of
Zoology at Southern Illinois University. This nest agrees in its measurements and
construction with several of those described by Meanley, and is very similar in appearance
to the photographed example shown in Mean ley’s figure 25.

The closest avian associates of Swainson’s Warbler at Cave Creek include not only

210

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

all the species listed as associates by Meanley hut also the Indigo Bunting (Passerina
cyanea) , a few of which nest in cane at Cave Creek and hence perhaps compete with
Swainson’s Warbler for nesting sites.

As Meanley does not mention the response of Swai'nson’s Warbler to its taped voice,
I think it may he useful to know that, at times at least, both males and females are
strongly attracted by the recorded notes of the characteristic male song. For example,
during May, 1971, Charles T. Clark, playing the Pennsylvania-taped [= Maryland. — Ed.]
song from the Peterson Field Guide Record Series, repeatedly succeeded in drawing a
pair of these warblers into clear view at Cave Creek.

I thank the Pine Hills Field Station and the Department of Zoology of Southern Illinois
University for financial support in 1971. — William G. George, Department of Zoology,
Southern Illinois University, Carbondale, Illinois 62901, 15 November 1971.

LIFE MEMBER

Lovett B. Williams, Jr. of Gainesville,
Florida has recently become a Life Member
of the Wilson Society. Mr. Williams, who
is a wildlife biologist for the Florida Game
and Freshwater Fish Commission, is a
graduate of Florida State University and
holds a Master’s degree from Auburn Uni-
versity. His work with the Commission has
involved mostly the study of the biology
and management of the wild Turkey, but
he has also been concerned with studies
on the Sandhill Crane and the Brown
Pelican. He has published a number of
technical papers on the Turkey as well as
several general ornithological papers, and
some popular conservation articles. Mr.
Williams is currently President of the
Southeastern Section of the Wildlife Soci-
ety, as well as being a member of the AOU,
the AAAS, the Ecological Society of Amer-
ica, and several other conservation organi-
zations. He is married and has one child.

ORNITHOLOGICAL NEWS

Alfred S. Romer, Alexander Agassiz Professor Emeritus of Harvard University
delivered the first annual George Mikseh Sutton Lecture at the University of Oklahoma
on 29 March 1972. These lectures, which will bring distinguished lecturers on ornithology
and related fields to the University campus each year were endowed by a gift by Dr.
Sutton to the University, who then named the series for the donor.

The name of Clarence S. Jung was inadvertently omitted from the list of members
who had completed 50 years of activity in the Society which was printed in the December
1971 issue.

The formal dedication of the Delaware Museum of Natural History building at Green-
ville, Delaware took place on 13 May 1972.

Request for information. — Information about breeding records and other records of birds
on Barro Colorado Island is needed for a revision of the list published in 1952 by E.
Eisenmann. Contact Edwin 0. Willis, Department of Biology, Princeton University,
Princeton, New Jersey 08540.

The Smithsonian Institution has received word from the Bombay Natural History
Society of Bombay, India, that the Society would be pleased to provide facilitative services
to advanced pre- or post-doctoral students in ornithology who wish to pursue field re-
search projects in India and who would be willing to demonstrate to Indian graduate
students up-to-date ornithological research techniques, particularly in quantitative
studies in eeology, population dynamics, food and feeding habits, migration and similar
areas.

The Bombay Natural History Society can offer its own study facilities, reference
collections and library and caU provide the Indian institutional base necessary for
foreign research projects in India, but cannot offer financial support.

Interested ornithologists are invited to seek support, for their travel, maintenance
and research expenses in India from the Smithsonian Special Foreign Currency Program.
Under this program, the Smithsonian makes grants in PL-480 foreign currencies,
including Indian rupees, to support the basic research activities of American institutions
in a number of disciplines including the natural sciences. These grants are awarded
on a competitive basis after review by leading senior scientists in the discipline concerned.
Other countries where these excess currencies are available include Poland, ugoslavia,
Egypt, Tunisia and Pakistan.

Incjuiries about the Smithsonian Foreign ('urrency Program should he addressed to
the Director, Smithsonian Foreign (Currency Program, Smithsonian Institution, Washing-
ton, 1). C. 20560.

21 1

HAWAIIAN BIRDS 1972*

Andrew J. Berger

More kinds (species and subspecies) of birds bave become extinct in Hawaii than on
all continents of the world combined. These endemic Hawaiian birds have become ex-
tinct since 1840, and most of them have succumbed since the 1890s. Table 1 lists the
endemic Hawaiian birds which are presumed to be extinct.

Moreover, Hawaiian birds account for nearly one-half of the birds in the U. S. Bureau
of Sport Fisheries and Wildlife’s Red Book of rare and endangered species. The follow-
ing list contains 16 of the rare and endangered Hawaiian birds: Newell’s Manx Shear-
water (Puffinus puffinus neivelli) , Hawaiian Dark-rumped Petrel iPterodroma phaeo-
pygia sandwich ensi s) , Harcourt’s Storm Petrel {Oceanodroma castro cryptoleucura) ,
Neue or Hawaiian Goose (Branta sandvicensis) , Koloa or Hawaiian Duck (Anas
wyvilliana) , Laysan Duck (Anas laysanensis) , Hawaiian Hawk iButeo solitarius) ,
Hawaiian Gallinule (Gallinula chloropus sandvicensis), Hawaiian Coot (Fulica ameri-
cana alai) , Hawaiian Black-necked Stilt (Himantopus himantopus knudseni) , Hawaiian
Crow (Corvus tropicus). Large Kauai Thrush {Phaeornis obscurus myadestina) , Molo-
kai Thrush (Phaeornis o. rutha) , Small Kauai Thrush (Phaeornis palmeri) , Nihoa
Millerbird (Acrocephalus familiaris kingi) , and the Kauai Oo (Moho braccatus) . To
this list may he added the non-migratory Hawaiian population of the Black-crowned
Night Heron (Nycticorax n. hoactli) .

But, there are even more endangered Hawaiian birds! Because of their special
interest to ornithologists, I include a second table (Table 2) to cover Hawaii’s only en-
demic bird family, the Hawaiian honeycreepers or Drepanididae. What this table means in
terms of the 22 species and 24 subspecies of honeycreepers that were delineated by
Amadon (1950) is that there is not a single species, whose range once included more
than one of the Main islands, that does not have populations that either are already
extinct or have endangered populations on one or more islands!

The honeycreepers that currently are considered non-endangered are found primarily
on the islands of Kauai, Maui, or Hawaii, although the Amakihi and Apapane on Oahu
are not classified as endangered. Tlie Anianiau (Loxops parva) is endemic to Kauai
only. Only the Kauai race of the Akepa (Loxops coccinea caeruleirostris) , and only the
Kauai (Loxops maculata bairdi) and Maui (L. m. newtoni) races of the Creeper are
thought not to be endangered. The Apapane, Amakihi, and liwi are still common in
suitable habitat on Kauai, Maui, and Hawaii. This is a pitiful remnant of a family of
birds that demonstrated the results of adaptive radiation to a far more striking degree
than even the Galapagos Finches.

In view of this depauperization of Hawaii’s unique avifauna, what can one say about
the prospects for preserving the dwindling populations that exist in 1972? Unfortunately,
one must say that the prospects are poor, indeed. Unfortunately, too, this essay probably
will serve only two functions: to document what has been, and still is, happening, and to
give me a writing exercise. I am but one in a long series of people who have decried the
rape of the Hawaiian hiota.

Scott Wilson, an English ornithologist, called attention to some of the problems as

* The Conservation Committee of the Wilson Ornithological Society, recognizing that bird con-
servation problems in the Pacific islands have unusual urgency, decided to concentrate its efforts
for 1971—72 upon them. This report by Dr. Berger is the first portion of the Committee’s report
for the year. Gustav A. Swanson, Chairman.

212

Andrew j. CONSERVATION SECTION— HAWAIIAN BIRDS 1972 213

Rerffpr ^ j.

Table 1

Extinct Hawaiian Birds

Full Species Subspecies

Laysan Rail, Porzanula palmeri
Hawaiian Rail, Pennula sandwichensis
Oahu Oo, Moho apicalis
Molokai Oo, Moho bishopi
Black Mamo, Drepanis funerea (Molokai)
Kioea, Chaetoptila angustipluma (Hawaii)
Hawaii Oo, Moho nobilis
Greater Amakihi, Loxops sagittirostris
(Hawaii)

Greater Koa Finch, Psittirostra palmeri
(Hawaii)

Lesser Koa Finch, Psittirostra flaviceps
(Hawaii)

Grosbeak Finch, Psittirostra kona (Hawaii)
Ula-Ai-Hawane, Ciridops anna (Hawaii)
Mamo, Drepanis pacifica (Hawaii)

Akialoa, Hemignathus obscurus

(all three subspecies are extinct:
Oahu, Lanai, and Hawaii)

Laysan Millerbird, Acrocephalus /.
familiaris

Laysan Honey creeper, Himatione sanguinea
freethii

Oahu Thrush, Phaeornis obscurus oahensis
Oahu Akepa, Loxops coccinea rufa
Oahu Nukupuu, Hemignathus 1. lucid us
Lanai Thrush, Phaeornis obscurus
lanaiensis

Lanai Creeper, Loxops maculata montana

Extinct Populations of Surviving Species

liwi, V estiaria coccinea, on Lanai
Ou, Psittirostra psittacea, on Oahu,
Molokai, and Lanai
Crested Honeycreeper, Palmeria dolei,
on Molokai

Table 2

Rare and Endangered Honeycreepers

Kauai Nukupuu, Hemignathus lucidus
hanepepe

Kauai Akialoa, Hemignathus procerus
’^Kauai Ou, Psittirostra psittacea
Oahu Creeper, Loxops m. maculata
Oahu liwi, V estiaria coccinea
^Molokai Creeper, Loxops maculata jlammea
Molokai liwi, V estiaria coccinea
Lanai Apapane, Himatione s. sanguinea
Lanai Amakihi, Loxops virens wilsoni
Maui Akepa, Loxops coccinea ochracea
Maui Nukupuu, Hemignathus lucidus afjinis

Maui Crested Honeycreeper, Palmeria
dolei

Maui Parrothill, Pseudonestor
xanthophrys

“Maui Ou, Psittirostra psittacea
Hawaii Ou, Psittirostra psittacea
Hawaii Creeper, Loxops maculata maria
Hawaii Akepa, Loxops c. coccinea
Akiapolaau, Hemignathus wilsoni
Balila, Psittirostra bailleui
Laysan Finch, Psittirostra c. cantans
Nihoa Finch, Psittirostra c. ultima

^A single species once inhal)itecl Kauai, Oahu, Molokai, Lanai, Maui, and Hawaii; all popula-
tions are either extinct or endangered.

^ May be extinct.

214

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

long ago as 1890; H. W. Henshaw and R. C. L. Perkins wrote of others in 1902 and
1903; William A. Bryan, J. F. Rock, George C. Munro, Harvey I. Fisher, Frank Richard-
son, Richard E. Warner, and others made pleas for protection of the birds and their
habitat during the long period between 1912 and 1964. All wrote in vain.

One has a choice, of course: to remain silent and he liked, or to speak out and be
disliked. Obviously, I agree with Hawaiian environmentalist Tony Hodges, who re-
marked that “the people in the ecology movement are in it to survive, not to make
friends.”

Unless there is, in the immediate future, a drastic change in the attitudes of State and
Federal officials toward the native Hawaiian ecosystems, Scott Wilson’s prediction of
1890 surely will come true — “it would not be rash to say that ere another century has
elapsed but few native species will remain.”

In Hawaii, as elsewhere, the greed and bureaucratic policies of men lie at the root of
the problem. Following are the major subjects that need immediate attention.

I, INTRODUCED HERBIVORES

Cattle, horses, goats, sheep, and English pigs were first given their freedom on the
Hawaiian Islands between 1778 and 1803. Game mammals were introduced later:
axis deer, 1868; mouflon sheep, 1954; pronghorn, 1959; mule or blacktail deer, 1961.
Feral horses apparently were exterminated in the 1930s, hut all of the other grazing
and rooting mammals continue to devastate the vegetation today. What is being done to
correct the problem?

A. In an attempt to pave the way for increasing substantially the size of Volcanoes
National Park, the National Park Service published in 1970 a glossy, multicolor brochure
entitled “Tire Island of Hawaii.” Among the totally misleading statements that belie
the Service’s past performance, we find that enlargement of the Park will make it possible
to “preserve the resources,” that is, to “reestablish native ecosystems where practical;
control, and where possible, eliminate nonnative species to protect the native biota.”

In 1971 Park rangers estimated the goat population in Volcanoes National Park to
number 14,000 animals! The Park Service announced that an effort finally would he
made to exterminate the goats. However, the very small, but vociferous, group of local
goat hunters appealed to their Congressional representatives, after which instructions
to “lay off the goats” reached Hawaii from Mr. George B. Hartzog, Jr., Director of the
National Park Service. Details of this story were discussed by Mr. Anthony Wayne
Smith in the June, August, and November 1971 issues of The National Parks and Con-
servation Magazine.

The Hawaii Chapter of The Wildlife Society, the Hawaii Audubon Society, and other
conservation groups have published “position papers” calling for the eradication of
feral goats from Volcanoes National Park and Haleakala National Park on Maui. The
Park Service, however, has taken only token measures to reduce the number of goats.

No meaningful action has been taken by the National Park Service to reduce the
feral pigs in either of the parks, although the superintendents have given wide publicity
to their plans to declare the newly acquired Kipahulu Valley segment of Haleakala
National Park a “wilderness area.” They propose to maintain Kipahulu Valley in a
wilderness state, not by reducing or eliminating the pigs, goats, and exotic plants, but
by making it virtually impossible for scientists and hikers to enter the area — because
they might carry some weed seeds in their pant cuffs!

I propose that NATAPROBU (the National Association of Professional Bureaucrats)
award the 1972 “Order of the Bird” to Mr. Hartzog and the National Park Service.

Andrew j. CONSERVATION SECTION— HAWAIIAN BIRDS 1972 215

Berger

B. The only remaining, extensive mamani (Sophora chrysophylla) and naio (Myo-
poruni sandwicense) ecosystem is found on Manna Kea on the island of Hawaii. This
endemic ecosystem provides the only known habitat for the endangered Palila, and it
is the only habitat in which the even rarer Akiapolaau has been seen fairly regularly in
recent years.

The mamani-naio forest is part of some 82,000 acres on Mauna Kea that are owned
by the State of Hawaii. Of the total acreage, only about 30,000 acres are now forested,
however; scattered tropical subalpine and alpine plants are found above the tree line,
but the highest part of the mountain consists primarily of barren lava and cinder. Clas-
sified as a forest reserve for about 50 years, this land was turned over to the Division of
Fish and Game in the early 1950s and was redesignated the Mauna Kea Forest Reserve
and Game Management Area. Late in 1971, the Division of Forestry erected a large
sign, announcing anew that this was the Mauna Kea Forest Reserve; it still is a game
management area, as well. What actual value has been placed on this unique ecosystem by
the Divisions of Forestry and Fish and Game?

1. The Division of Forestry has never conducted any significant research on either
mamani or naio. Mamani seeds form a large part of the diet of the Palila.

2. Tree line of this dying forest once extended to about 10,000 feet. It now is found
much lower, and continues to recede because of the overpopulation of both sheep and
pigs. Except within exclosures, regeneration of mamani is virtually nonexistent be-
cause the seedlings are eaten by the sheep and rooted out by the pigs. Hunters in Hawaii
have so much political power, however, that on several occasions they have forced
the Division of Fish and Game to close or shorten the sheep-hunting season in order
to allow the population to increase even more (Kramer, 1968). Consequently, no effort
is being made to eradicate the feral sheep or even to reduce the herd to a reasonable size —
carrying capacity of the range is a concept not considered in Hawaii. At the same
time, great pressures are constantly being exerted to introduce the axis deer to this
habitat. The influence of hunters upon these decisions seems remarkable in view of their
small number, only 10,134 licensed hunters in Hawaii in 1970, according to a recent
report by the Wildlife Management Institute.

3. The Kaohe Game Management Area (contiguous with the Mauna Kea Game Man-
agement Area) is open for archery hunting only, even though it contains a great over-
population of both pigs and sheep. State personnel estimate that a fluctuating population
between 500 and 1,000 sheep occupy this fenced area of approximately 6,500 acres. One
would have to search far, indeed, to find more stark examples of “browse lines”
than on trees in this dying forest. Moreover, more than 150,000 acres are open only to
archery hunters on the island of Hawaii.

Richard E. Warner (1960) called attention to some of these problems more than a
decade ago.

II. IF YOU HAVE SEEN ONE ENDEMIC TREE, YOu’VE SEEN THEM ALu!

The ohia ( Metrosideros co/lina ssp. polymorpha) is the dominant tree in most of the
Hawaiian rain forests, and tree ferns (Cibotium spp.) are the most conspicuous element
in the understory. The ohia-tree fern ecosystem is the most important habitat for the
majority of the surviving endemic forest birds. Koa i Acacia koa), a valuable endemic
tree, was important for certain species of boneycrei'pers in the past, but tberc are
few, if any, virgin koa ecosystems remaining. Sandalwood (Sant'i/um spp.) was once
a valuable native tree, but tbe commercial supply became exhausted in the 1830s.

216

THE WILSON BULLETIN

June 1972
Vol. 81, No. 2

The importance to certain endemic birds of the unique mamani-naio ecosystem was
mentioned earlier.

How do State and Federal employees view these endemic ecosystems?

A, C. S. Judd, then the Superintendent of Forestry for the Territory of Hawaii, wrote
in 1918 that “the destruction of the Hawaiian forest in the past was deplorable, but that
it should continue in the present . . . seems inexcusable,” He added that the prime
value of Hawaiian forests was “in their ability to serve as a protection to watersheds,”
and, therefore, that foresters should be “chiefly concerned with forest protection.” In
1927 he wrote that it was time to conduct research on “some of the ecological problems”
in Hawaii. Unfortunately, Mr. Judd’s successors did not follow his recommendations.

In 1957 the State Division of Forestry initiated a cooperative agreement with the
U. S. Forestry Service to conduct a forest survey and the necessary research aimed at
developing a timber industry in Hawaii. Since that time, the Institute of Pacific Islands
Forestry, Pacific Southwest Forest and Range Experiment Station, Forest Service,
U.S.D.A., in Honolulu has given guidance to the State foresters. The board-feet-oriented
Federal foresters repeatedly refer to the endemic Hawaiian ecosystems as “decadent
forests” and as consisting of “unproductive forest land,” and they have developed an
“effective and efficient technique for eliminating cull” ohia trees — by “injecting un-
diluted herbicides into tree trunks.”

More than 46,000 acres have been cleared and planted with exotic trees, most of
which do not have even a potential commercial value. More importantly, much of the
planting effort has been concentrated on already-forested land. This has caused the
utter destruction of near-virgin native forests: for example, along the Kulani Prison

road on Hawaii. More than 1,500 acres were “reforested” within so-called forest reserves
during fiscal year 1969-1970.

U. S. Forestry personnel in Hawaii finally decided in late 1970 that some research
on koa should be considered, and in 1971, they voiced concern about ohia. There can
be little doubt but that this belated interest in some of the endemic trees resulted partly
because of the constant prodding of conservationists in Hawaii, although another event
undoubtedly was important. On 13 May 1970, Norman Carlson, the highly respected
manager of the Bernice P. Bishop Estate agricultural and forest lands, addressed a
forestry conference on Maui. Carlson recommended that the foresters de-emphasize
exotic tree species and concentrate on the endemic koa and ohia. He said: “I know
now that I should have studied koa when I first got involved in forest management.
It is a native tree, adapted to our soils, and valuable as wood. So is ohia. . . . We had
basic data on exotics — growth rates, survival, soil types and tests [on wood properties]
by Madison [Wisconsin 1. From these we thought we knew the answer to our forest
renewal [in Hawaii]. . . . Koa is a beautiful wood, distinctive and native to Hawaii.
... It has evolved over the years and should be better adapted to Hawaii than any of the
exotics. Ohia is another native we have casually dismissed, and someday we will rue
this. . . . Now that we are beginning to value koa, we must work toward the problems
of koa forest management.” He then gave a list of questions about koa for which the
State and Federal foresters did not have answers.

Nevertheless, the 1972-1976, 5-year Forest Planting Plan of the State Division of
Forestry does not mention koa, ohia, mamani, naio, sandalwood, or tree fern, but calls for
the planting of 6,092 acres of public lands with 17 species of exotic trees at a cost of 1.3
millions of dollars. This despite Carlson’s recommendations and despite the fact that

CONSERVATION SECTION^HAWAIIAN BIRDS 1972 2 1 7

there is not a viable timber industry in Hawaii, and some scientists believe that there never
will be, nor should be.

George B. Harpole stated in bis “Opportunities for Marketing Hawaii Timber Products”
that “the introduction of plywood production, and the expansion of lumber production
in Hawaii are presently technically and logistically feasible. Fiberboard or particleboard
production could also be started. Mill residues may not provide a sufficient supply of
wood chips, but additional volumes of raw materials could be developed from non-
commercial stands of Hawaii’s present timber supply, and from the State’s other
agricultural resources.”

Harpole included maps of eight of the Hawaiian Islands to show the “major forest
types in Hawaii.” The areas classified as suitable for commercial forestry include vir-
tually all of the remaining ohia-koa-tree fern forests on the windward slopes of both
Mauna Kea and Maiuia Loa and on the Kona slope of Mauna Loa. This view of the
native ecosystems presumably is justified because “native forests in Hawaii are essen-
tially static in terms of annual increases. In the unmanaged native forests, trees must fall
from the damage of termites or rot, be blown over, or be harvested before new growth
can appear.”

Harpole’s study was published in 1970 as U.S.D.A. Forest Service Research Paper
PSW-61. This is an excellent example of the kind of “leadership” given by Federal
foresters in Hawaii, and it demonstrates why conservationists have such a difficult time
in their efforts to preserve what little remains of the endemic ecosystems.

Despite Harpole’s statement about plywood production, “a plywood plant with a 5
million square foot capacity sits idle on the Big Island. Locally-produced craftwood
is less and less able to compete with imports. More Christmas trees may soon be pro-
duced in Hawaii than can be sold. [In fact, this happened in December 1971, when
high-priced locally grown trees did not sell well.] We must determine the standards
which Hawaii’s products must meet to compete in the marketplace, locally or as exports
to Pacific Basin outlets. And the market potential of several timber species now being
planted should be evaluated before they reach merchantable size” (“Forest Conserva-
tion Research Plan for the Seventies,” Department of Land and Natural Resources,
Honolulu, 1971) .

According to the “Honolulu Advertiser” of 2 April 1971, Senator Hiram L. Fong
reported that he and R. Keith Arnold, deputy chief of research of the U. S. Forest
Service, would request the U. S. Congress to allocate $250,000 to Hawaii in order to
start a southern pine timber industry. Congress was sympathetic, and actually allocated
$414,000 to State and Federal foresters in Hawaii. To be sure, not all of these monies will
be used for planting pine trees, nor, we have been assured locally, for destroying native
ecosystems.

One of the “nice” things about Federal funds is that they are “free” to the states!
It seems a little late in history, however, for one branch of the Federal Government to
provide monies to destroy native ecosystems while at the same time another branch is
providing funds for the acquisition of lands to preserve flora and fauna and to conduct
research on rare and endangered species. Two Federal biologists of the rare and en-
dangered species program are assigned to full-time study in Hawaii.

B. The Division of Forestry is not making any concerted effort to eradicate any of
several introduced plant weed-species, some of which present a real threat to near-
virgin forest areas, including the Alakai .Swamp region of Kauai, which is the habitat
for more endemic forest birds than can he found on any other island.

To he sure, the Division finally has become concerned about the serious infestation of

218

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

banana poka U^assiflora mixta) on the Hamakua Coast of Hawaii. The Division’s present
solutions, however, appear to he either to cut down the forest or to open it to cattle graz-
ing!

C. Conservationists in Hawaii were elated when the Governor finally appointed
the Commissioners for a newly created Natural Areas Reserve System. During its first
year, however, the State Division of Forestry effectively blocked all significant action by
the Commission.

D. During 1969 and 1970, the Division of Fish and Game bulldozed (or, as they
say, “selectively treated”) some 400 acres of prime mamani-naio forest in order to
“open it up” in the hopes that it would serve as better habitat for exotic pheasants.
Further “habitat improvement*' is planned for the future.

E. The State Department of Land and Natural Resources has established a very high
standard for coining euphemisms. The Department announced in 1971 that it had
“approved the experimental harvesting of ohia and koa trees on 500 acres zoned for con-
servation at Laupahoehoe on the Big Island.” When translated, this means that the
Department agreed to let a private individual destroy 500 acres of the Laupahoehoe
Forest Reserve in order to get more wood to make howds and other souvenirs for tourists!
Actually, it was time by 1971 to approve this “experimental harvest”: the wood-carving
company began bulldozing the road through the forest reserve to the harvest area in
1969!

The Laupahoehoe Forest Reserve consists of some of the finest near-virgin ohia-koa-tree
fern forests on the island of Hawaii, and there are very few such forests remaining in
Hawaii. Such continuing rape and destruction of the little that remains of Hawaii’s
unique ecosystems demonstrate clearly the true value placed on those ecosystems by
State and Federal personnel who manage the Hawaiian biota.

F. During 1971, the Bernice P. Bishop Estate applied for permission to harvest tree
ferns from 3,000 acres of the Kilauea Forest Reserve, which is not only a conservation
district hut also is equal to the Laupahoehoe Forest Reserve as a remnant of this rain
forest ecosystem. The tree fern logs, or hapuu, are harvested by bulldozers, which com-
pletely destroy the understory and. eventually, the forest. Nursery owners need hapuu
logs as the substrate for growing orchids and other flowers! Perhaps some day, the
Division of Forestry will investigate the feasil)ility of growing tree ferns in nurseries,
rather than destroying endemic ecosystems to ol)tain the ferns.

III. STATE QUARANTINE LAWS

Rabies does not exist in Hawaii, and justified strict regulations are designed to
prevent that fatal disease from reaching the islands. Similarly, every conceivable effort
is made to prevent the introduction of any insect or bird species that might harm sugar
or pineapple. Beyond these precautions, however, Hawaii’s quarantine laws are a farce.

Except for psittacine and gallinaceous birds from foreign countries, pet store birds are
not subjected to any quarantine regulations at all. More than 20 species of cage
birds f primarily weaverfinches) have been released accidentally or intentionally in the
Honolulu area since 1965. What new parasites or diseases these birds may have carried
is unknown.

In 1970, a doctoral student at the University of Hawaii reported the first diagnosis for
the Hawaiian Islands of a Leucocytozoon infestation of pigeons and two species of intro-
duced doves, as well as four previously unreported species of Plasmodium, the proto-
zoan parasite that produces bird malaria.

Excluding the Jungle Fowl, at least 78 kinds (species and subspecies) of potential

it'rlr ^ CONSERVATION SECTION— HAWAIIAN BIRDS 1972 219

game birds had been released in Hawaii as of 1967 (Walker, 1967), No thorough
follow-up study by State personnel has been conducted on any of these. Lewin and
Holmes (1971), however, reported that 13 of 33 game bird species that had been intro-
duced on the Puuwaawaa Ranch on Hawaii had Ijecome established as breeding birds.
Among 115 birds examined, the authors found 11 different species of worm parasites;
they reported 13 new host records for these parasites and four species of parasites were
recorded for the first time in Hawaii.

It must be admitted that we do not know what effect these parasites have on the
birds, even though the early introduction of bird diseases to the Hawaiian Islands pro-
vided a “most logical” explanation for the extinction of so many endemic species and
for the great reduction in numbers of others. However, as of 1972, there are no reliable,
published data to substantiate this oft-repeated assertion. No careful, intensive studies
have ever been conducted! Nevertheless, the accidental introduction of new ecto-
parasites and blood and other internal parasites would seem to he ample reason for
initiating thorough studies of bird diseases, as well as for improving the quarantine
laws. The State has taken no action in either direction. In fact, before passing “A
Bill for an Act Relating to the Protection of Indigenous Fish, Bird, Animal, and
Vegetable Life” in Hawaii, a legislative conference committee wrote on 28 April
1970 that the “conference committee would like to also allay the fears of pet shop
owners by making it perfectly clear that this bill only applies to animals, birds, etc.,
introduced by the State and does not intend to affect pet shop owPers who bring pets in
for sale to the public.” Moreover, the final bill was completely emasculated.

IV. A QUESTION OF PRIORITIES

During the past decade, the State Department of Land and Natural Resources spent
millions of dollars (State and Federal monies) to destroy native forests and to import
exotic plants and animals, but only a negligible amount was expended on endemic
plants and animals.

A. The Coot, Gallinule, Stilt, and Black-crowned Night Heron are considered to be
endangered species in Hawaii. The drastic reduction in population size of these birds
is presumed to be due to the destruction of essential wetland habitat during the past 30
years. Despite this, no research has been conducted by personnel of the State Division
of Fish and Game or of the U. S. Bureau of Sport Fisheries and Wildlife into the
breeding biology, parasites, predator relationships, or food habits of any of these species.
Nor has any study been made of potential chemical poisoning of the few wetland areas
still extant, even though the Chairman of the State Department of Agriculture stated
in a public lecture in 1969 ( Forty-fifth annual meeting of the Hawaiian Academy of
Science, 11 December 1969) that Hawaiian agriculturists apply 10 times the amount per
square mile of chemical pesticides and herbicides than is used on the Mainland U.S.A.,
and that “local exterminators use 500 to 1000 times the amount of poison used in Main-
land applications.”

B. No intensive field study of introduced game l)irds has been conducted since
Charles and Elizabeth Schwartz worked in Hawaii during 1946 and 1947 (a project that
was financed by the Federal Aid to Wildlife program). Nevertheless, the State Division
of Fish and Game reijuested $20,000 for the period 1971-1973 for “brush thinning”
( that is, bulldozing tbe mamani-naio forest ) on Mauna Kea in order to increase the
“productivity of this area for providing game birds,” and they recpiested an additional
$5,000 to construct water tanks for game birds.

C. Tbe Nene was considered close to (*xtinction in 1949 (Scbwartz and Scbwartz, 1949).

220

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Tlie State Division of Fish and Game has carried on a very successful artificial rearing
program at Pohakuloa on the island of Hawaii in recent years, and the Nene has been
named the State bird. This work, however, has been supported almost exclusively by
Federal funds ($15,000 per year from 1958 through 1967, and $25,000 per year since
that time) .

The role of Mr. H. C. Shipman of Hilo, Hawaii, and of the Wildfowl Trust in
Slimbridge, England in the rearing of Nene in captivity deserves recognition, because
their efforts contributed much toward saving the species from extinction, even though it
is true that a large proportion of the several hundred Nene alive today are in captivity,
or semi-captivity. As a private hobby Mr. Shipman had for years reared Nene in semi-
captivity on his ranch on Hawaii so he was able to contribute two pairs of the birds to
the State of Hawaii in 1949 for its artificial propagation efforts.

Then in the spring of 1950 Peter Scott, Director of the Wildfowl Trust, arranged for
Mr. John Yealland, curator of the Trust and an acknowledged expert among experts
in the rearing of waterfowl, to spend several weeks in Hawaii assisting the State in its
propagation efforts. When Mr. Yealland returned to England, Mr. Shipman sent with
him two female Nene, thought to he a pair, and later in the year shipped to the Trust
a gander; from this breeding start of 3 birds the Wildfowl Trust has, through 1970,
successfully reared more than 300 birds, of which 198 have been returned to Hawaii to
be released in the wild by the State in its efforts to reestablish the species; the
remainder have been placed in several collections of living waterfowl in England and
on the Continent, to encourage the species’ prospects of survival. These efforts at
artificial propagation of the Nene are described by Smith (1952), and in the Annual
Reports of the Wildfowl Trust from 1951-1952 (the Fifth) through 1971 (the 22nd).
Beginning with the report numbered 19, appearing in 1968, the publication carries the
title simply “Wildfowl.” Nene also have been raised by S. Dillon Ripley II in Connecti-
cut.

Almost 500 pen-reared Nene were released in the native habitat on Hawaii between
1960 and 1969. Unfortunately, very little has been learned about the annual cycle of
the Nene in the wild. The State Division of Fish and Game has admitted that it does
not have any cojnpetently trained people assigned to the job! Consequently, little more
is known about the biology and status of wild populations than was known in 1958,
and that was virtually nothing (Elder and Woodside, 1958).

Although it is uncertain that the Nene was ever a breeding species on the island of
Maui (Baldwin 1945), 242 pen-reared birds were released in Haleakala Crater between
1962 and 1969. More than half of these birds were raised in England and Connecticut.
Nesting is known to have occurred, hut not a single young bird was known to have
been raised to independence as of 1970; three “near-mature goslings” were observed in
1971, but their ultimate fate was not determined. No thorough study of the Maui popula-
tion has ever been conducted.

Extramural funds are not limited to the $25,000 received annually for the Nene propa-
gation program by the Division of Fish and Game. For example, there is an annual
appropriation (on a 3:1 matching basis) of Pittman-Robertson Aid in Wildlife Restora-
tion funds from the Federal Government. This varies from about $130,000 to $170,000
per annum. The Division uses this money to support “all wildlife development projects,”
and these include bulldozing the mamani-naio forest on Mauna Kea in the hopes that
more pheasants will inhabit the area. Some of these funds are used for Koloa propaga-
tion, but the State also has received additional monies from the World Wildlife Fund
for this program. (In addition to the funds received for wildlife, the Division of Fish

Bete7 ^ CONSERVATION SECTION— HAWAIIAN BIRDS 1972 221

and Game also is a beneficiary of the Federal Aid in Sport Fish Restoration Act, the
Dingell-Johnson Act.)

The picture is clear, therefore: Nene and Koloa will he reared in captivity as long as
non-State funds are available, but no meaningful effort will be made to study the biology
of any endemic species in the native habitat, particularly with State funds. In fact, a
grand total of $16,508 of State general funds was expended for “Wildlife Research and
Management” for fiscal 1968-1969. Apparently none of this money was actually used
for wildlife research or management (it was used for a non-game bird biologist posi-
tion), but the phrase “wildlife research and management” looks better in official reports.

State money is available for other purposes, however. In 1971, the Division of Fish
and Game awarded a contract for $45,(X)0 to a California consultant to prepare “a
comprehensive long-range fish and wildlife plan to serve as a guide for the orderly and
rational development of its fish and wildlife resources to meet the future recreational,
economic, scientific, aesthetic and educational demands that will be made on these
resources.” Nowhere in the resolution of the House of Representatives (dated 20 May

1969) , which requested this study, nor in the contract for the consultant services

is there mention of any endemic species of animal. The entire emphasis is on “recrea-
tional fishing and game hunting.”

My critics may assert that the function of a State Division of Fish and Game is to
provide fish and game for the citizens of that state, and, in general, I would agree. I

do not agree, however, that that should be the sole function in the island State of

Hawaii, in part because only about one per cent of the citizens purchase hunting licenses
(1969-1970 Report to the Governor, Department of Land and Natural Resources, Hono-
lulu, January 1971). I assert that the unique Hawaiian forests and their animal life
belong to all of the people, not only of Hawaii but also of the entire United States, and,
indeed, of the world.

D. A revealing document is the “Forest Conservation Research Plan for the Seventies,”
which was published by the Department of Land and Natural Resources in 1971. This
potpourri contains overt and veiled reference to nearly all of the criticisms leveled at the
Department during the past 10 or 15 years. It even uses such words and phrases as
“ecology,” “unique ecosystem,” and “plant interactions and distribution dynamics.” It
is obvious to anyone knowledgeable about the Hawaii Department of Land and Natural
Resources, however, that the Department has little or no intention of changing past
policies of destroying native ecosystems, planting exotic tree species, and introducing
more game animals.

Although all state positions are “frozen,” the glossy publication recommends a
“research program for the 70’s equivalent to nearly 74 scientist-man-years of annual ef-
fort,” even though “after 10 years [the 1960sl research devoted to forest conservation
problems [which, in fact, meant, bulldozing endemic forests and planting exoticsl totals
about 40 scientists per year.” Moreover, the elal)orate table that compares the ostensible
scientist-man-years per year expended during the 1960s and the recommended figure for
the 1970s does not actually contain a single reference to any endemic ecosystem.

At the same time, I was interested to read the items listed in the recommended research
projects on “Wildlife and Fish Habitat,” partly because it includes the title of my
research program (“Life history and functional anatomy of tin* Hawaiian honey-
creepers”), which was funded originally by the National Science Foundation in 1966!

I At least 16 other research projects in the brochure were taken directly from Technical

! Report No. 1 (December 1970) of the Hawaii Isl and Ecosystems .Stability and Evolution

Subprogram of the United .States International Biological Program.

222

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

The Division of Fish and Game also intends, during the 1970s, “to determine the
effect of forest clearing on endemic birds.” In other words, the Division of Forestry will
destroy native ecosystems, after which the Division of Fish and Game can report that
the endemic birds no longer inhabit those areas!

E. At the 1968 convention of the International Association of Game, Fish, and Con-
servation Commissioners, a committee presented a fine report on rare and endangered
species, which included an appendix: “Suggested model state legislation for rare and
endangered species.” The committee stressed that “public awareness and support is a
prerequisite to the success of the preservation program.” The Chairman of the committee
was the Director of the Hawaii Division of Fish and Game.

The Director of the Hawaii Division of Fish and Game has never presented the model
law to the legislature; Hawaii is perhaps the only state in which the Division of Fish
and Game has no budgeted funds for information and education of the public; and,
except for propagation programs for the Nene and Koloa (conducted with non-State
funds) , there has been no effort to implement any of the philosophy expressed in the
report of 1968.

The future of Hawaii’s unique birds is bleak, indeed.

LITERATURE CITED

Amadon, Dean. 1950. The Hawaiian honeycreepers (Aves, Drepaniidae) . Bull. Amer.
Mus. Nat. Hist., 95:151-262.

Baldwin, P. H. 1945. The Hawaiian Goose, its distribution and reduction in numbers.
Condor, 47 :27-37.

Elder, W. H., and D. H. Woodside. 1958. Biology and management of the Hawaiian
Goose. Trans. 23rd North Amer. Wildlife Conference 1958:198-215.

Kramer, Ray. 1968. We’re botching conservation! Honolulu, July 1968:20-21, 43-47.
Lewin, V., AND J. C. Holmes. 1971. Helminths from the exotic game birds of the
Puuwaawaa Ranch, Hawaii. Pacific Sci., 25:372-381.

Schwartz, C. W., and E. R. Schwartz. 1949. A reconnaissance of the game birds in
Hawaii. Board of Commissioners of Agriculture and Forestry, Honolulu.

Smith, J. Donald. 1952. The Hawaiian Goose (Nene) Restoration Program. J.
Wildl. Mgmt., 16: 1-9.

Walker, R. L. 1967. A brief history of exotic game bird and mammal introductions
into Hawaii — with a look to the future. Conference Western Assoc. State Game and
Fish Commissioners, Honolulu, July 19, 1%7:1-13.

Warner, R. E. 1960. A forest dies on Mauiia Kea. Pacific Discovery, 13:6-14.
Wilson, Scott. 1890. On some of the birds of the Sandwich Islands. Ibis, 1890:
170-196.

DEPARTMENT OF ZOOLOGY, UNIVERSITY OF HAWAII, HONOLULU, HAWAII 96822.

ORNITHOLOGICAL LITERATURE

Studies of Bird Hazards to Aircraft. Canadian Wildlife Service Report Series — No.

14. Dept, of Indian Affairs and Northern Development, Ottawa, 1971: X H in.,

105 pp. paperback. $1.25.

Aviation was still in its infancy in 1910, when a bird-airplane collision claimed a
human life for the first time. Thereafter the problem probably increased with the
number of aircraft, especially as faster planes were developed, but there was relatively
little public concern until 1960 when more than 60 airline passengers were killed as
a result of a bird strike. Suddenly, governments showed increased interest in supporting
studies of bird migration, and well they should have. As Gunn and Solman predict in
this report (p. 22), bird strikes are likely to he even more disastrous in the immediate
future, as bigger, faster planes with bigger engines ( to scoop up more and/or larger
birds) carry ever more passengers.

In 1963 the National Research Council of Canada undertook, or encouraged intensive
as well as broad investigations of the problem of birds and aircraft, and this book
presents some of the results of those studies. The hook consists of seven technical papers,
which deal with one aspect or another of the subject of bird migration. Most of the
observations were made in Canada, but the papers are fairly strong on literature review,
which in effect, gives them wider geographic coverage. Specific direct information on
bird strikes or birds as hazards to aircraft is presented in the first two papers only.

There are few illustrations, but they make forceful comment on the problem of air-
craft collisions with birds (and vice versa). A photograph (p. 18) showing part of the
inner workings of an airplane engine heavily matted with gull feathers is a sight to
give any pilot (or airline passenger) a twinge of fear, and a picture of a cloud of
gulls is at once esthetically appealing and insidiously fearsome in company with text that
tells us of nine F-104 Starfighters and two other possibles (at 1.5 million dollars each)
being downed by birds, plus a statement that even a small bird can cause serious

engine damage and loss of power. For civil flights, about three-fourths of the bird
strikes occur near airports. Plane damage from such strikes at Canadian airports has
already been reduced by applying knowledge gained from bird studies. The bird-
aircraft collisions that occur while a plane is enroute between airports represent a more
difficult set of problems.

It is suggested in this hook (p. 22) that all major airports need bird-warning systems,
i.e., staff and equipment to forecast bird flights, and that ports lacking such systems
are guilty of negligence. The cost of a warning system is not actually estimated, hut
; Solman (p. 11) hints that it would more than pay for itself in reduced aircraft damage
and reduced insurance claims, not to mention the less calculable value of human life.

Through radar and field studies one such bird-warning system (at Cold Lake, Alberta)
was tested for accuracy in forecasting the peaks of bird flights by 1-2 hours, and up to
1 24 hours. The forecasts were considered .50 per cent accurate in spring, hut only 35
per cent accurate in fall. (By comparison, meteorologists claim about 85 per cent

I accuracy on 6-hour weather forecasts.) Even an accurate pn'diction of relative numbers
1 of birds flying is no guarantee of aircraft safety. Snow Cheese felled one .‘^tarfighter

I at Cold Lake at the very hour when forecasters had accnratrly predicted low flight

I densities. The forecasts are based to a large (*xt(mt on radar observations, hut low
' flight densities on any scale may still nu'an hundreds of birds m“ar tli(‘ airport, and it

223

224

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

only takes one to drop a plane. Bird warning systems still have a very long way to go
to become effective safeguards. Ultimately such systems are dependent upon detailed
knowledge of the movements of hundreds, even thousands, of populations of birds, and
toward this goal we are only well started. An excellent example of the kind of informa-
tion needed comes from the nicely dove-tailed field and radar studies by Myres and
Cannings (p. 23) on the flight of a Canada Goose population through British Columbia.
The birds flew a narrow corridor at altitudes of 8,000 to 15,000 feet. This is im-
portant information for any pilot who flies in the area, and more so if the goose flights
are predictable. That’s fine as far as it goes, but when you realize that we do not even
know the number of other populations that utilize that airspace, you get some measure
of the complexity of forecasting bird flights.

The book deals at some length with the benefits and deficiencies of using radar in
migration studies, and provides a good comparison between radar and lunar observa-
tions. We are repeatedly reminded that ornithological studies using radar are hampered
because radar stations are operated primarily for meteorological work, and only incidently
for bird surveillance.

The best feature of the work is the wealth of information on migration in Canada,
especially near the Alberta-Saskatchewan line, a strategic location for comparison with
the two other areas (Illinois and New England) where major radar studies of migration
have been made. Thus, for example, the dominant spring flight direction of night
migrants is northeast in New England and Blinois, but northwest in Alberta. The
Canada studies also provide the best year-around coverage of flight densities and direc-
tions available for the continent, plus good discussions of migration and weather. Migra-
tion was most consistently correlated with following winds, not with temperature, and
not consistently with pressure change. There were also instances of reverse migration
and an example of Canada Geese apparently compensating for wind drift. Clearly this
is an important reference for all students of migration.

The make-up of the book is extravagant of paper. Tliere was an apparent effort to
stretch the work into a book-sized publication. Several pages are actually or virtually
blank, and many more are only one-half to two-thirds filled. This is a minor fault,
however, beside the fact that one-third or more of the material presented has already
been published elsewhere in essentially the same form by the same authors. One of the
papers is an acknowledged duplication of a chapter in a 1%8 symposium on the prob-
lems of birds as pests. In the history of science such wasteful duplication has never
been acceptable, but at a time when many libraries are crowded with publications almost
to the bursting point, and bibliographers are hard pressed to see even original works, such
duplication is an extravagance that none of us should afford. — Richard R. Graber.

The Morphology of the Syrinx in Passerine Birds. By Peter L. Ames. Bulletin 37,

Peabody Museum of Natural History, Yale University, New Haven, Conn., 1971;

7 X 10 in., paper covered, 194 pp., 21 pis. of pen and ink drawings. Price not given.

The literature of anatomy contains many descriptions of the syrinx in various species
of birds, but almost nothing that goes beyond the descriptive stage of investigation.
“The Morphology of the Syrinx in Passerine Birds” goes far beyond previous studies
of this organ. In this study Dr. Ames describes details of muscle and cartilage struc-
ture in suboscine families and genera for which no previous descriptions are on record,
and gives extensive references to earlier descriptions of these and other groups. He
then uses these descriptions as bases for taxonomic and evolutionary interpretations.

June 1972
Vol. 84, No. 2

ORNITHOLOGICAL LITERATURE

225

In the first section of the book the author compares and relates the passerine taxa, a
task involving a great amount of labor. Those who have worked with the syringeal
morphology of this group of birds will appreciate the meticulous work and keen in-
sight Dr. Ames used in bringing a large degree of order to passerine classification, based
on his own findings in comparison with those of Garrod, Muller, Gadow, Ridgway,
Peters, Wetmore, and others. He supports these authors in their use of the syrinx as a
basis for passerine classification, and suggests certain shifts in taxonomic positions. He
concludes (p. 153) that “Taken in conjunction with other anatomical characters,
syringeal morphology suggests that the Passeriformes be divided into five suborders:
Eurylaimi, Furnarii, Tyranni, Menurae, and Passeres (Oscines).”

While Dr. Ames provides logical reasons for assigning positions to various families
and genera, he points out possible errors due to the complete lack of fossil evidence,
and the very meager understanding of the actual functioning of the syringeal muscles,
cartilages, nerves, and other tissues. Almost nothing is known of interactions among
morphology, behavior, and evolution of the syrinx. His discussion points to several areas
in which research is lacking.

The book includes excellent line drawings illustrating muscles and cartilages of the
syringes of 76 suboscine species in nine families, and one drawing of Corvus, illustrat-
ing the oscine suborder. Drawings of cartilage details illustrate 23 other suboscine spe-
cies. There is a comprehensive list of references and a record of specimen sources.

This book is an extensive, but not an exhaustive, study of passerine classification. It
will be a valuable asset to students of passerine morphology and taxonomy, and the
sections on evolution and development will also be of interest to persons interested in
these topics. Dr. Ames is to be congratulated on his presentation. — Mildred Miskimen.

Natural Resources and Public Relations. By Douglas L. Gilbert. The Wildlife
Society, Washington, D.C., 1971: X 9^A in., xxiv + 320 pp., numerous text figures.

16.50.

There presently exist two schools of thought among scientists as to the duty of the
scientist in reporting his (her) findings to the public. If you believe, as I do, that a
researcher is morally obligated to report any findings which bear upon the general
welfare of the public to that public, then this volume will be most welcome. For in re-
porting to a non-scientific public there is a definite need for a background in public
f relations. Dr. Gilbert is attempting to provide just this type of background for workers
i, in the field of natural resources.

The philosophy for the public relations approach is well stated by Dr. Gilbert (p.

' 162) :

(

J “Most research done in natural resources management is reported only for scientific

consumption, if at all. Publication should be the last step of every research project.
Publication in a popular or semi-popular magazine is as eijually important to the
professional and to the research worker as is publication in a scientific journal.
Many scientific findings are made known to non-professional publics ordy when the
resultant management methods are used or an attempt is made to use them.’’

i

1 1 Further, Gilbert writes (p. 163) :

“...For example, most wildlife stories available today are the “how I got a full
bag limit” type, or the “vicious killer meets death” kind. 'Ihesc* should be minimized

226

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

and replaced by the good sportsman, the good management or the good research
project kind. This problem is not the fault of the magazine publishers. The blame
is the natural resource managers for not writing the stories.”

As stated in the Forward, this book is specifically designed for the workers in natural
resources. It has been my experience that students in this general area definitely have
a need for such background material. Dr. Gilbert touches on all aspects of communica-
tion in public relations, and presents in logical fashion the manner in which these
various media should be handled; he also very candidly demonstrates how not to
proceed. The 18 appendices provide a number of “tools” for use in public relations, al-
though several are rather specialized and limited in value.

Although I welcome this needed volume, it is, unfortunately, full of printers’ errors,
and in my opinion somewhat excessive in certain respects. Citations are given for some
rather commonplace statements (e.g. p. 84, line 13), resulting in a long section of litera-
ture cited. Also, it seems to me that too many illustrations have been included; many
appear to detract from the text rather than clarify it. This despite Gilbert’s statement
( p. 115) that “Too many visual aids can complicate and confuse rather than clarify,
and may be worse than none at all. Only those wdiich are necessary and which will
help the presentation should be used.” I would like to see a revised edition published
which would set higher standards of quality, and which would then be adopted by a
wdder segment of all scientists, including those involved in the natural resource area. —
Keith A. Arnold.

SoFTBiLLED BiRDS. By CHve Roots. Arco Publishing Co., Inc., New Tork, 1970: 8^ X
'0V2 in., 158 pp., 36 col. pis. by Robin Browm, 30 text figs. $5.95.

The preface of “Softbilled Birds” tells us that its object is “. . . to provide information
upon the practical aspects of maintaining softbills” in captivity. Many ornithologists and
all zoo curators would be grateful for a serious contribution to the literature of aviculture
but Softbilled Birds is disappointing.

The book opens with a discussion of the term “softbilled,” nevertheless we are left
confused about which species it is intended to include. In fact, the author divides “soft-
bills” into five dietary aggregations; nectivorous. frugivorous, omnivorous, insectivorous,
and carnivorous. Most medium to large sized birds are excluded, whatever their
tastes in foods, and so are parrots and finches. Although the book is largely concerned
with tropical species, English common names alone are used throughout. Where an
attempt has been made to utilize the scientific nomenclature of families or genera, it
has often ended badly.

Softbilled Birds is organized into twm parts, the first dealing with the acquisition
and care of softbills, and the second with the five dietary groups noted above. Two
extremely brief appendices offer interesting analyses of rations for softbills in captivity,
and recipes for mixtures which Mr. Roots has found adequate. The book is illustrated
with numerous line drawings of varying quality, and 36 birds are shown in color photo-
graphs. The photographs and their color reproduction are poor and do not add to the
reader’s understanding of the captive maintenance of wild birds.

Unfortunately, the text makes little attempt to bring together the now considerable
body of avicultural observation or to relate it to ornithology generally. Although
subject coverage is superficial, sensible counsel is presented on several aspects of bird-
keeping suitable for hobbyists. — William G. Conway.

June 1972
Vol. 81, No. 2

ORNITHOLOGICAL LITERATURE

227

Breeding Biology of California and Ring-billed Gulls: A Study of Ecological
Adaptation to the Inland Habitat. By Kees Vermeer. Canadian Wildlife Service
Report No. 12, Dept, of Indian Affairs and Northern Development, Ottawa, 1970:
SV2 X 11 in., paper covered, 52 pp., maps, charts, and photos. $1.25. Catalog Number
R65-8/12.

American sociologists and Canadians are aware of a rising tide of Canadian nationalism,
identity, and independence; often the effects of these changing attitudes are directed at
and felt by Americans. Canadians take pride in their work and products; often Ameri-
cans are criticized for lack of common sense and a sense of aesthetics. The Canadian
Wildlife Service can be proud of this report. Compared with American publications
and monographs, it is tastefully packaged, skillfully edited, and lavishly illustrated.
Where American studies tend to dull one’s mind just because of the format, design,
and details of presentation, this study is so well presented as to be exciting just because
of the methods of design which were used. American editors could learn a good deal
from examining the careful use of varying type styles, line drawings, and column
placement of this publication. I have long wondered why so many of our American
journals and monographs are so dully presented; this publication makes it clear that
such pedantry is false and unnecessary. It is also remarkably free of detracting typo-
graphical and editorial errors. The graphic presentations are pertinent and easy to
understand.

Voluminous data are presented. This research, which was performed pursuant to a
doctorate at the University of Alberta, was apparently designed to fill the many gaps
in our knowledge about breeding of these gull species in prairie colonies. As with many
of us who research areas where we do not know enough to generate firm hypotheses
before the field work, Vermeer used the “shot gun” approach — he collected data on
all aspects that might be important. The result is information on many aspects of the
biology of these gull species. Some data bear on the central question of adaptation to
the prairie-lake habitat; some data do not.

From a technical viewpoint, I wonder about the appropriateness of several of Vermeer’s
implicit assumptions and choices of ways to deal with data. For example, to my knowl-
edge, few if any investigators have used insecticide analyses of uropygial glands to
indicate potential involvement of birds with pesticide poisoning. It is questionable
whether uropygial fat (lipid) is ever used by birds as an energy source. Probably, most
investigators interested in levels of pesticides will not be able to relate Vermeer’s data to
existing information on levels of body fat. For example, the data (Table 18) comparing
levels of residues in brains and uropygial glands of eight Ring-billed Gulls suggest that
the glands are a poor choice of tissues to estimate loads of residues in lipids. Usually
there is a 10 to 20-fold higher level of residues in body fat than in brain tissues; these
data suggest a 2:3 ratio of tissue residues in brain: uropygial gland. The significance
is obscure.

There are some surprising oversights in literature citations on Ring-hilled Gulls.
Valuable comparative data were available to Vermeer on Ringhills in writings of Belknap,
Bent, Kutz, F. E. Ludwig, J. P. Ludwig, Ryder, Southern, and probably others. Ver-
meer’s comparison of the California and Ring-billed Gull populations he studied with
other species of Laridae is excellent and insight-filled, but his comparison with other
Ringbill populations and colonies is almost non-existemt. As an exanij)le, Vernu'er f)inits
comparison of dates of first egg-laying from his study with the date's available in Ih'iitV
monograph (U. S. Natl. Mus. Bull., 113, 1921). My own data on food samples for

228

THE WILSON BULLETIN

June 1972
Vol. 84, No. 2

Ringbills were not referred to (Ludwig, Great Lakes Research Div., Univ. of Michigan,
Puh. 15, 1966) . Other comparative data are omitted as well.

My fundamental criticism of Vermeer’s interpretation is that I do not accept his im-
plicit assumption that “gulls” in general do not have adaptations to the inland habitat
where California and Ring-hilled Gulls nest. To he sure, most “gulls” nest on marine
coasts and coastal islands. One can assume thereby that “gulls” in general are not
adapted to the inland habitat, hut this is an assumption. Vermeer moves from this
assumption to comparison of largely marine gull species with the gulls he studied in
Alberta, concluding that Ring-hilled Gulls and California Gulls do not show many adapta-
tions to the inland habitat. This is apparently true when these species are compared to
other gulls. Because I dispute the assumption, I cannot fully accept Vermeer’s con-
clusion. I am also disturbed by the apparent assumption that adaptation to the habitat
of Alberta will be reflected in morphological or behavioral attributes of the species.
I think a better argument can be made that almost all gull species are adapted to sur-
vival in the face of regular castastrophe. Except for a very few species, gulls have very
higli potential reproductive rates (three eggs per year) and very low adult death rates
(8-13 per cent annual mortalities). Thus the catastrophic loss of an age class or two
is insignificant to almost all gulls. Gulls are adjusted to catastrophe. In this light, both
California and Ring-billed Gulls are pre-adapted to conditions of a capricious, often
hostile prairie habitat. Thus, Vermeer’s conclusion that California and Ring-billed Gulls
show few specific adaptations to the prairie habitat may be correct. His implication
that these species are not well adapted to the prairie habitat is most surely incorrect.

For the serious student of gulls, this is an important report. It provides abundant
data. It is valuable for other workers who will wish to compare their larid studies
with other studies. Vermeer’s treatment of the adaptation problem is particularly valuable
when he compares other species to those he studied. In summary — a tastefully presented
valuable piece of work, subject only to criticism of detail and interpretation. — James P.
Ludwig.

Signals for Survival. By Niko Tinbergen and Hugh Falkus; drawings by Eric

Ennion. Clarendon Press, Oxford, 1971: 8% X H14 in., 80 pp. $8.00.

This fascinating and informative book, liberally illustrated by photographs and draw-
ings, deals with communications among Lesser Black-backed Gulls. The authors explain
the intricate language of these birds, “a system of signalling, comprising posture, move-
ment, sound and color,” as they describe it. A gull colony on Walney Island off the
coast of Lancashire is the location for the book. The life of this seemingly chaotic
colony is shown to be very ordered, with the island divided into territories maintained
by the male birds’ unmistakable (to others of their species) calls and actions: loud

trumpeting calls, much aggressive strutting, and fighting. The story of the gulls’ be-
havior starts with these territorial border disputes and proceeds to the male’s attraction
of a female, their adjustment to each other, choice of a nest site, egg-laying, and hatching
(illustrated by wonderful photographs of a chick breaking its way out of an egg). The
account continues with the raising and protection of the young, the chick’s recognition
of its parents voice, food preferences of individual gulls, and finally the young birds’
learning to fly and departure for Africa. All this is described and explained by a well
written text and excellent illustrations. The hook makes its information accessible to
young readers and non-biologically oriented adults as well as to those who are already
interested in animal communications. — Sally Laughlin.

This issue of The Wilson Bulletin was published on 30 May 1972

Editor of The Wilson Bulletin
GEORGE A. HALL
Department of Chemistry
West Virginia University
Morgantown, West Virginia 26506

Editorial Advisory Board

William C. Dilger
Douglas A. James
William A. Lunk
Andrew J, Meyerriecks

Helmut C. Mueller
Robert W. Nero
Kenneth C. Parkes
Glen E. Woolfenden

Ornithological Literature Editor
Peter Stettenheim

Box 79, Plainfield, New Hampshire 03781

Suggestions to Authors

Manuscripts intended for publication in The Wilson Bulletin should be neatly type-
written, double-spaced, with at least one inch margins, and on one side only of good quality
white paper. Tables should be typed on separate sheets, and should be designed to fit
the normal page width, i.e., narrow and deep rather than wide and shallow. Before pre-
paring these, carefully consider whether the material is best presented in tabular form.
Follow the AOU Check-list (Fifth Edition, 1957) insofar as scientific names of United
States and Canadian birds are concerned unless a satisfactory explanation is offered for
doing otherwise. Use species names (binomials) unless specimens have actually been
handled and subsequently identified. Summaries of major papers should be brief but
quotable. Where fewer than five papers are cited, the citations may be included in the text.

■ All citations in “General Notes” should be included in the text. Follow carefully the style
^ used in this issue in listing the literature cited; otherwise, follow the “Style Manual
IJ for Biological Journals” (1964. AIBS). Photographs for illustrations should be sharp,
have good contrast, and be on gloss paper. Submit prints unmounted and attach to
j, each a brief but adequate legend. Do not write heavily on the backs of photographs.
Diagrams and line drawings should be in black ink and their lettering large enough to
permit reduction. Authors are requested to return proof promptly. Extensive alterations
in copy after the type has been set must be charged to the author.

Notice of Change of Address

If your address changes, notify the Society immediately. Send your complete new
address to the Treasurer, William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.
He will notify the printer.

The permanent mailing address of the Wilson Ornithological Society is: c/o The
MUSEUM of Zoology, The University of Michigan, Ann Arbor, Michigan 48104. Persons
having business with any of the officers may address them at their various addresses
given on the back of the front cover, and all matters pertaining to the Bulletin should be
sent directly to the Editor.

WILSON ORNITHOLOGICAL SOCIETY
ANNUAL MEETINGS

1st 1914 Chicago, Illinois
2nd 1914 Chicago, Illinois
3rd 1915 Columbus, Ohio
4th 1916 Chicago, Illinois
5th 1917 Pittsburgh, Pennsylvania
6th 1919 St. Louis, Missouri
7th 1920 Chicago, Illinois
8th 1921 Chicago, Illinois
9th 1922 Chicago, Illinois
10th 1923 Cincinnati, Ohio
11th 1924 Nashville, Tennessee
12th 1925 Kansas City, Missouri
13th 1926 Chicago, Illinois
14th 1927 Nashville, Tennessee
15th 1928 Ann Arbor, Michigan
16th 1929 Des Moines, Iowa
17th 1930 Cleveland, Ohio
18th 1931 New Orleans, Louisiana
19th 1932 Columbus, Ohio
20th 1934 Pittsburgh, Pennsylvania
21st 1935 St. Louis, Missouri
22nd 1936 Chicago, Illinois
23rd 1937 Indianapolis, Indiana
24th 1938 Ann Arbor, Michigan
25th 1939 Louisville, Kentucky
26th 1940 Minneapolis, Minnesota
27th 1941 Urbana, Illinois

28th 1946 Omaha, Nebraska

29th 1947 Columbus, Ohio

30th 1949 Madison, Wisconsin

31st 1950 Jackson’s Mill, West Virginia

32nd 1951 Davenport, Iowa

33rd 1952 Gatlinburg, Tennessee

34th 1953 Cheboygan, Michigan

35th 1954 Cape May, New Jersey

36th 1955 Stillwater, Oklahoma

37th 1956 Buffalo, New York

38th 1957 Duluth, Minnesota

39th 1958 Wheeling, West Virginia

40th 1959 Rockland, Maine

41st 1960 Gatlinburg, Tennessee

42nd 1961 Huntsville, Ontario, Canada

43rd 1962 Lafayette, Indiana

44th 1963 Charleston, South Carolina

45th 1964 Kalamazoo, Michigan

46th 1965 Sylvan Lake, South Dakota

47th 1966 University Park, Pennsylvania

48th 1967 Crawford Notch, N. Hampshire

49th 1968 Carbondale, Illinois

50th 1969 Williamsburg, Virginia

51st 1970 Fort Collins, Colorado

52nd 1971 Dauphin Island, Alabama

53rd 1972 Cape May, New Jersey

\Af

TIieWlsonBulletin

PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY
WEST VIRGINIA U. • MORGANTOWN, W. VA.

VOL. 84, NO. 3 SEPTEMBER 1972 PAGES 229-372

I

\i

The Wilson Ornithological Society
Founded December 3, 1888

Named after ALEXANDER WILSON, the first American Ornithologist.

President — Pershing B. Hofslund, Dept, of Biology, University of Minnesota Duluth,
Duluth, Minnesota 55812.

First Vice-President — Kenneth C. Parkes, Carnegie Museum, Pittsburgh, Pennsylvania
15213.

Second Vice-President — Andrew J. Berger, Dept, of Zoology, University of Hawaii,
Honolulu, Hawaii 96822.

Secretary — James Tate, Jr., Laboratory of Ornithology, Cornell University, Ithaca, New
York 14850.

Treasurer — William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.

Elected Council Members — Elden W. Martin (term expires 1973) ; Robert D. Burns (term
expires 1974) ; Harvey I. Fisher (term expires 1975) .

Membership dues per calendar year are: Active, $8.00; Sustaining, $15.00;

Life memberships, $200 (payable in four installments).

The Wilson Bulletin is sent to all members not in arrears for dues.

The Josselyn Van Tyne Memorial Library
The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed
in the University of Michigan Museum of Zoology, was established in concurrence with
the University of Michigan in 1930. Until 1947 the Library was maintained entirely
by gifts and bequests of books, reprints, and ornithological magazines from members
and friends of the Society. Now two members have generously established a fund for
the purchase of new books; members and friends are invited to maintain the fund by
regular contribution, thus making available to all Society members the more important
new books on ornithology and related subjects. The fund will be administered by the
Library Committee, which will be happy to receive suggestions on the choice of new books
to be added to the Library. William A. Lunk, University Museums, University of Michi-
gan, is Chairman of the Committee. The Library currently receives 104 periodicals as gifts
and in exchange for The Wilson Bulletin. With the usual exception of rare hooks, any
item in the Library may be borrowed by members of the Society and will be sent prepaid
(by the University of Michigan) to any address in the United States, its possessions, or
Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers,
as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to
“The Josselyn Van Tyne Memorial Library, University of Michigan Museum of Zoology,
Ann Arbor, Michigan.” Contributions to the New Book Fund should be sent to the
Treasurer (small sums in stamps are acceptable). A complete index of the Library’s
holdings was printed in the September 1952 issue of The Wilson Bulletin and newly
acquired books are listed periodically.

The Wilson Bulletin

The official organ of the Wilson Ornithological Society, published quarterly, in March, June, September,
and December, at Morgantown, West Virginia. The subscription price, both in the United States and elsewhere,
is $10.00 per year. Single copies, $2.50. Subscriptions, changes of address and claims for undelivered
copies should be sent to the Treasurer. Most back issues of the Bulletin are available (at $2.50
each) and may be ordered from the Treasurer. Special prices will be quoted for quantity orders.

All articles and communications for publications, books and publications for reviews should be addressed to
the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology,
Ann Arbor, Michigan.

Second class postage at Lawrence, Kansas, U.S.A. 66044

Allen Press, Inc., Lawrence, Kansas 66044

THE WILSON BULLETIN

A QUARTERLY MAGAZINE OF ORNITHOLOGY

Published by The Wilson Ornithological Society

VoL. 84, No. 3 September 1972 Pages 229-372

CONTENTS

Fall Migration in Coastal Louisiana and the Evolution of Migra-
tion Patterns in the Gulf Region Kenneth P. Able 231

Recognition of Nest, Eggs, Nest Site, and Young in Female Red-
winged Blackbirds

Frank W. Peek, Edwin Franks, and Dennis Case 243

Communal Wintering of a Sandhill Crane with Japanese Cranes

IN Hokkaido, Japan Hiroyuki Masatomi 250

An Evaluation of Winter Bird Population Studies .. Richard Brewer 261

Activity Patterns of Canada Geese During Winter

Dennis G. Raveling, Wendell E. Crews, and W. D. Klimstra 278

Reproductive Behavior of the Common Loon

Sverre Sjolander and Greta Agren 296

Responses of Adelie Penguins to Colored Eggs

Leigh H. Fredrickson and Milton W. Weller 309

Variation in the Posterior Border of the Sternum in Some Tree-

Trunk Foraging Birds Alan Feduccia 315

I Cranial Pneumatization Patterns and Bursa of Fabricius in North

American Shorebirds Raymond McNeil and Jean Burton 329

I

i General Notes

i

SPECTACULAR HAWK FLIGHT AT CAPE MAY POINT, NEW JERSEY ON 16 OCTOBER

1970 - - Ernest A. Choate 340

OSPREY CARRYING A MAMMAL

William W. Tait, //. Malcolm Johnson, and William 1). Courser 341

THE MIGRATION OF THE HUFF-BREASTED SANDPIPER THROUGH SURINAM

E. llaverschrnidt 341

I

CONGENITAL FOOT ABNORMALITY IN THE RING-BILLED GULL

John P. Ryder and David J. Chamberlain 342

SWALLOW-LIKE BEHAVIOR IN THE RUSTY-MARGINED FLYCATCHER, MYIOZETETES

CAYANENSIS, IN COLOMBIA Michael Kent Rylander 344

THE RECENT HISTORY OF bachman’s WARBLER Henry M. Stevenson 344

WINTER HABITAT OF kirtland’s WARBLER Harold F. Mayfield 347

STABILITY OF A POPULATION OF MALE RED-WINGED BLACKBIRDS

David E. Davis and Frank Peek 349

Ornithological News 351

Ornithological Literature 352

David Lack, Ecological Isolation in Birds, reviewed by Richard T. Holmes;

Ernst Schiiz, Grundriss der V ogelzugskunde, reviewed by E. G. Franz Sauer;
Brooke Meanley, Natural History of the Swainsons Warbler, reviewed by
Maurice Brooks; Warren B. King, The Trade Wind Zone Oceanography Pilot
Study. Part VII. Observations of Seabirds, March 1964 to June 1965, reviewed
by Nagahisa Kuroda; Alexander F. Skutch, A Naturalist in Costa Rica, re-
viewed by P. Slud; Robert Arbib and Tony Soper, The Hungry Bird Book,
reviewed by Nancy Ellison; John Sparks and Tony Soper, Owls. Their Natural
and Unnatural History, reviewed by J. David Ligon; Alfred M. Bailey, Gala-
pagos Islands, reviewed by Peter Stettenheini.

Publication Notes and Notices 277, 361

Proceedings of the Fifty-third Annual Meeting

James Tate, Jr., Secretary 362

Announcements and Study Projects

295, 328, 339

FALL MIGRATION IN COASTAL LOUISIANA AND
THE EVOLUTION OF MIGRATION PATTERNS IN
THE GULE REGION

Kenneth P. Able

Many passerine birds make long overwater flights during the course of
their seasonal migrations; it is obvious that natural selection has fa-
vored these flights in spite of the risks and energetic demands involved. The
Gulf of Mexico is one region where the arrival and departure of overwater
migrations can be observed to advantage.

Even at the height of the exchange between Lowery (1945 ) and Williams
(1945) concerning the occurrence of spring trans-Gulf migration, it was gen-
erally assumed that autumn migrants regularly cross the Gulf in large num-
bers (e.g., Williams, 1947). In the years following the controversy, spring
migration in the Gulf region has been extensively studied, but there have been
few concentrated investigations of fall migration. More or less anecdotal ob-
servations of birds crossing the Gulf in fall were made by Griscom (1945),
Paynter (1951, 1953) and Siebenaler (1954). Buskirk (1968) studied the
arrival of migrants on the north coast of Yucatan.

The extensive investigations of vernal trans-Gulf migration have shown
that the pattern of air flow around the Bermuda high-pressure system char-
acteristic of that season is conducive to overwater flights (Lowery, 1951;
Gauthreaux, 1971 ) . Indeed, Gauthreaux has shown that trans-Gulf migra-
tions early in spring, when the Bermuda high is not a consistent feature, occur
in spurts which are dependent upon the establishment of southerly air flow
over the Gulf. After the beginning of April, moist tropical air moves north-
ward across the Gulf, interrupted only by the infrequent penetration of power-
ful cold fronts. The consistency of this favorable flow pattern has probably
been a strong selective force in the evolution of vernal trans-Gulf migration.
If this is true, one would predict the development of a different pattern in fall
because wind patterns are not favorable for regular, large-scale Gulf crossings.

During the fall of 1969 I obtained data on the direction and magnitude of
: bird flow in southwestern Louisiana while I was conducting field studies on
the orientation of nocturnal migrants. These observations shed light on three
(juestions: What is the general flow pattern of autumn migration on the

northwestern Gulf coast?; How is this pattern related to major weather sys-
tems? ; and What evolutionary strategy has led to the broad-front migration
I patterns we see today?

231

232

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

METHODS

I conducted this study on 34 nights in August, September, and October at Lake Charles,
Louisiana, about 23 nautical miles north of the Gulf coast. The nights were not selected
in any way, except that no data were used from nights with several hours of rain. I used
the WSR-57 radar at the U. S. Weather Bureau station to determine the traffic rates
(in birds per mile of front per hour) of nocturnal passerine migration as described by
Gauthreaux (1970). I determined the direction of passerine movement (tracks) on the
same nights using two portable ceilometers and a 20 X 60 telescope (see Gauthreaux,
1969) .

For comparative purposes in the following discussion, I have used the maximum hourly
traffic rate recorded on each night as the magnitude of migration on that night. The
flight direction parameters of the birds observed with the portable ceilometer (half-hour
samples taken 19:00-20:00 or 20:00-21:00 CSTl were determined according to Batschelet
(1965).

GULF WEATHER PATTERNS IN AUTUMN

The typical low-altitude air flow across the Gulf of Mexico in fall is similar
to that in late spring and summer. The southeasterly flow characteristic of
these seasons is produced by the clockwise circulation of air around the
strong Atlantic subtropical high-pressure system (Bermuda high) and the
cyclonic circulation around a low-pressure area over the Mexican Plateau.
As autumn progresses, the Gulf area comes under the increasing influence of
a continental high-pressure system over central North America. This cold
air mass is separated from the Atlantic high by a cold front. Wind condi-
tions over the Gulf in autumn depend upon the juxtaposition of these two
pressure systems and the polar front ( Petterssen, 1958 ) . When the front
passes into the Gulf, as it does infrequently in fall, northerly winds conducive
to trans-Gulf flights occur. These conditions occur most regularly later in
fall, after the bulk of passerine migrants has passed. During the longer pe-
riods between invasions by the continental high, the predominantly south-
easterly winds are generally opposed to direct flights from the northern Gulf
coast to Yucatan.

The prevailing weather situations during autumn, 1969, were typical for
the region and fall rather neatly into five categories as follows:

I. This condition is dominated by the continental high pressure system
when it is situated in the central or eastern United States. Figure 1 shows
this pattern, which occurs after the passage of a cold front into the south-
eastern states. The degree of penetration of the front and the exact position
of the high-pressure area will determine the orientation of isobars and winds,
but the air flow is generally from the northeast or east. This was the most
frequent of the five weather conditions, occurring on 11 (35.5 per cent)
days during the study (9-10, 10-11, 11-12, 12-13, 18-19, 19-20, 20-21, 21-
22 September, 8-9, 22-23, 23-24 October ) .

Kenneth p. FALL MIGRATION IN COASTAL LOUISIANA 233

Fig. 1. The flight directions of birds in Weather Pattern I. The vector diagram is
plotted so that the radius equals the greatest number of birds in any 7.5° sector. The
arrowhead denotes the mean flight direction. See text for a discussion of the weather
patterns. The weather map shown is that for 12 September 1969.

II. High pressure over the southeastern United States generates south-
easterly winds over most of the Gulf. This condition occurred on 8 ( 25.8 per
cent) days during my study and was particularly characteristic in August.
A typical example is shown in Figure 2. (5-6, 6-7, 7-8, 25-26, 26-27, 27-
28, 28-29 August, 3-4 October).

III. This pattern is characterized by a well-developed southerly air flow
on the back side of a high-pressure system just ahead of a cold front. Winds
tend to be strong and thundershowers are frequent. This weather pattern
occurred on 5 ( 16.1 per cent) days during my observations and is shown in
Figure 3 (17-18, 22-23 September, 10-11, 11-12, 12-13 October).

IV. Pattern IV is more or less intermediate between II and III. It is
1 dominated by southerly winds in the central and western Gulf produced by

the northward flow of moist tropical air in the warm sector of a high-pressure
ridge over the eastern United States. This condition usually occurs as a cold
j front approaches from the west, but the air is more stable than that closer to
the front. This pattern occurred on 4 (12.9 jier cent ) days and is illustrated
in Figure 4 (1-2, 2-3, 4-5, 9-10 October).

234

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 2. The flight directions of birds in Weather Pattern II, plotted as in Figure 1.
The weather map shown is that for 28 August 1969.

Fig. 3. The flight directions of birds in Weather Pattern III, plotted as in Figure I.
The weather map shown is that for II October 1969.

Kenneth P.
Able

FALL MIGRATION IN COASTAL LOUISIANA

235

Fig. 4. The flight directions of birds in Weather Pattern IV, plotted as in Figure 1.
The weather map shown is that for 10 October 1969.

V. Conditions most conducive to autumnal trans-Gulf flights occur shortly
after the passage of a massive cold front which penetrates far into the
Gulf. The anticyclonic circulation around the continental high generates
northerly winds, the persistence of which depends largely upon the strength
of the frontal system. Only three cold fronts passed Lake Charles during
fall, 1969, and Pattern V characterized 3 (9.7 per cent) days during this
study. It was thus the most infrequent weather condition. A typical example
of this pattern is shown in Figure 5. (7-8, 13-14, 14-15 October).

The five weather patterns encompass all but three days during the study.
(30 September — 1 October, 20-21, 21-22 October). These three days were
each dominated by inconsistent, complex weather situations with low-pres-
sure centers in the Gulf of Mexico. Migrations on each of the three nights
were of low magnitude.

RESULTS

Flight directions of birds and weather patterns. — To obtain an overall
I view of the flow of autumn migration on the northern Gulf coast, I constructed
a vector diagram of the direction and magnitude of nocturnal passerine mi-

1

236

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 5. The flight directions of birds in Weather Pattern V, plotted as in Figure 1.
The weather map shown is that for 14 October 1969.

gration on all 34 nights of the study. For each night, the mean flight direc-
tion of landbirds was weighted by the logic maximum traffic rate recorded
during that night. The resulting distribution is shown in Figure 6a. The
mean flight direction, and thus the net flow of birds, was toward the west
(274°), but considerable dispersion in flight directions is indicated by the
large angular deviation (s) of 55.7° and the resultant vector length (r ) of
0.53. In Figure 66 are plotted the directions of surface winds on the 34 nights
of the study. There is a remarkable similarity between the distribution of
wind vectors and bird vectors and the mean wind direction (269°) and dis-
persion (s = 54.9°) do not differ significantly from the same parameters
of the bird distribution (parametric two-sample F-test; Batschelet, 1965).
If this relationship has sufficient generality, seasonal migration patterns in
other geographic regions could be predicted from long-term wind direction
data.

It is more instructive to examine the flight directions of the birds under
each of the five weather patterns. These data are plotted in Figures 1-5.

Pattern I is one of two ( with Pattern V ) weather situations which is gen-
erally favorable to fall migration, i.e., winds usually have a southward com-

Kenneth P.
Able

FALL MIGRATION IN COASTAL LOUISIANA

237

Fig. 6. A. Vector diagram of the mean flight directions of the birds (half-hour sam-
ples taken 19:00-20:00 or 20:00-21:00 CST) weighted by the logic maximum traffic rate
during the same night. B. Vector plot of the directions of surface winds, taken at the
times of ceilometer samples, on the 34 nights of the study. The vectors are plotted as
in Figure 1.

ponent. In general, air flow in this system parallels the Louisiana-Texas
coast and large movements of birds were observed flying in this west-south-
westerly direction. Under this general weather condition the mean flight
direction was 255° and the relatively small amount of dispersion about the
mean (s = 28.8°) shows that the flight directions of the birds are fairly con-
sistent from night to night, reflecting the relative constancy of winds in this
pattern.

Patterns II, III, and IV are characterized by winds blowing from the south,
generally counter to the expected flow of autumn migration. One of these
three patterns occurred on 54.8 per cent of the nights during this study.
Migrations of landbirds occurred under all three conditions and in each case
flight directions were toward the north. The mean flight direction under
Pattern II was 300° (s = 41.5°; r = 0.84) as shown in Figure 2. The flight
directions of passerines under Pattern III are shown in Figure 3. Here the
mean flight direction was 47° (s = 41.5°; r = 0.741. Northward flights
I with a mean direction of 7° (s = 28.3°; r = 0.88) occurred in weather typi-

j cal of Pattern IV. These data are plotted in Figure 4.

The optimum conditions for direct bird flow from the northern Gulf coast
I to the tropics occur when Pattern V prevails, i.e., following the jiassage of a

I cold front far into the Gulf. On the three nights when these conditions oc-

I _ ^ _

i curred, overwater flights departed from the Louisiana coast. Indeed, trans-
I Gulf departures took place only under these conditions. I he flight directions

I

i

238

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 7. The magnitude of migration under each of the five weather patterns. The
dots and vertical lines show the mean nightly maximum traffic rate and its standard
error under each condition.

of birds on these nights are plotted in Figure 5 where the mean direction is
207° (s = 19.2°; r = 0.94).

The relative magnitude of migration in diflerent directions. — Among the
diverse weather patterns which characterize the northern Gulf coast in fall,
some are obviously more favorable for a direct movement to the wintering
ground than others. We would expect, a priori, that passerine migrants would
have evolved the ability to select optimum weather conditions in which to
undertake long migrations. Most birds initiating a migratory flight from
southwestern Louisiana in the fall will move in one of three general direc-
tions: 1) southwest on a circum-Gulf flight parallel to the coast; 2) south-
ward directly across the Gulf to Yucatan; or 3) some direction generally
counter to the normal flow of autumnal migration. The foregoing results
and other data (Gauthreaux and Able, 1970, 1971; Able, 1971 and in prep.)
show that passerine nocturnal migrants fly downwind even when this be-
havior carries them in apparent “nonsense” directions. It is, therefore, of
considerable interest to know if migrations in seasonally appropriate direc-
tions are of disproportionately larger size.

The volume of migration under the five weather patterns is shown in
Figure 7. The graph shows the mean maximum traffic rate recorded under
each weather pattern. The means under Patterns II, III, and IV (those with

Kenneth P.
Able

FALL MIGRATION IN COASTAL LOUISIANA

239

Fig. 8. The proportion of migration occurring under each of the five weather patterns.
Open bars show the frequency of each weather pattern as a per cent of the total nights
sampled. Hatched bars represent the per cent of the total migration volume (total
nightly maximum traffic rates) observed under each condition.

generally southerly winds and “reverse” migrations) were significantly
smaller than those under Patterns I and V (those generally favorable to fall
migration) (^29 = 14.42; P< 0.001; two-tailed test). The histograms (Fig.
8) show the frequency of occurrence of each weather pattern and the propor-
tion of the total migration volume (based on nightly maximum traffic rates)
that took place under that Pattern. Only under Patterns I and V did more
migration occur than would be expected on the basis of the frequency of
occurrence of the condition. However, the differences were not great enough
to yield a significant value of Chi Square. The volume of migration immedi-
ately following the passage of cold fronts (Pattern V) is surprisingly small,

, as this might be considered the optimum condition for migration. At least
I part of the reason for this anomaly is that the three cold fronts occurred late in
' the migration season after the bulk of birds had passed. Traffic rates in all
weather conditions were considerably smaller toward the end of migration.

I In addition, October migrations contain a higher ratio of arriving winter
residents to passage migrants than earlier flights and thus fewer birds would
be likely to embark on trans-Gulf flights during post-frontal weather.

240

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

DISCUSSION

Trans-Gulf flights of considerable magnitude take place in fall, but in con-
trast to the spring migratory picture in the Gulf region, they are of irregular
occurrence. The results of this study show that the direction of autumn
passerine migration on the Louisiana coast conforms to the patterns of air
flow in major weather systems. This was predicted by our finding that passer-
ines at night fly downwind regardless of wind direction or speed ( Gauthreaux
and Able, 1970, 1971; Able, 1971). The correspondence of migratory flow
to broad-scale weather patterns results in a fairly large net movement of birds
on a circum-Gulf path.

Few other data are available with which my results may be compared.
Lowery and Newman (1966) analyzed data from moon-watching on four
consecutive nights. Trans-Gulf flights of considerable magnitude departed
on two nights immediately following the passage of a cold front into the Gulf.
Circum-Gulf flight directions were noticeable on the other two nights and at
the eastern and western ends of the northern Gulf coast. Their data are thus
in general agreement with mine.

On the north coast of Yucatan, Buskirk (1968) recorded at least small
incoming flights of passerine migrants almost daily in fall. Heavy flights
occurred only following the penetration of cold fronts into the Gulf. My
observations at Lake Charles cannot account for the regular arrival of mi-
grants in Yucatan in fall. However, predominant weather patterns often are
favorable for flights from Florida or Cuba.

The major broad-front migration patterns can be explained on the basis of
prevailing weather systems and the behavior of the birds. Large-scale wind
patterns are probably strong selective forces in the evolution of passerine
migration patterns, at least when these involve long overwater flights. The
pattern of selective downwind flight described here assures that small land-
birds will not embark on a hazardous overwater flight in unfavorable winds.
On the other hand, the same behavior allows them to be opportunistic in
taking advantage of northerly post-frontal winds when they occur in fall. In
the Gulf region, birds embark on a water crossing in both spring and fall
whenever winds are favorable. The major differences in the resultant sea-
sonal patterns are due to the fact that the wind flow^ across the Gulf is roughly
south to north during both seasons, while the main direction of bird flow is
reversed. But, although southerly winds blow on a majority of days during
the fall migratory period, a fairly strong net flow of birds in a southward
direction results from downwind flight coupled with some behavioral selec-
tion of favorable synoptic weather situations.

All the data from the Gulf region show that passerine migrants wdll not

Kenneth P.
Able

FALL MIGRATION IN COASTAL LOUISIANA

241

depart on an overwater flight into head winds. However, the birds leaving
Yucatan in spring or the northern Gulf coast in fall presumably cannot pre-
dict the presence of a cold front somewhere in the Gulf. We do not know
specifically what happens when a mass of migrants flying in tail winds meets
the front and its opposing winds over the water. However, when birds meet
a cold front in the northern Gulf in spring, many abandon downwind flight
and fight the head winds northward toward the coast. Since autumn cold
fronts rarely reach Yucatan, the birds usually meet partially or completely
opposing winds somewhere during the water crossing. Paynter (1953 ) and
Buskirk (1968) observed birds arriving in head winds at Yucatan. On the
contrary, Gauthreaux (pers. comm. ) once observed the northward return of
i a fall migration which had departed from the Louisiana coast only to meet
' a retreating cold front not far offshore. These observations imply that the
|| birds are employing some navigational ability (“map sense” of Kramer,
* 1953) and are somehow aware of their position in space relative to the geog-

' raphy of the Gulf. Once they have proceeded most of the way across the

'' water barrier, they will abandon their customary downwind flight in order to
i; reach the nearest shore if opposing winds are encountered.

SUMMARY

Passerine nocturnal migration was observed with radar and portable ceilometer on
j 34 nights during fall, 1969, at Lake Charles in southwestern Louisiana. Weather patterns

over the Gulf in fall are generally similar to those of late spring and summer and are

> usually characterized by southerly winds. These conditions, which favor large-scale trans-

IGulf migrations in spring, are opposed to such flights in fall. The daily weather pat-
terns observed during this study were grouped into five basic types. Passerine migrants
at Lake Charles flew with the wind, regardless of its direction. Because of the frequency
I of southerly winds, “reverse” migrations were common. However, a strong net flow of
birds in a southwesterly direction resulted from prevailing northeasterly winds and the
jj occurrence of disproportionately large migrations when air flow was favorable for move-
il ment toward wintering areas. Downwind flight assures that small landbirds will not
I embark on long overwater flights in unfavorable winds, but at the same time allows
|i them to take advantage of northerly post-frontal winds when they occur.

j ACKNOWLEDGMENTS

j ^ I am greatly indebted to the personnel of the U.S. Weather Bureau at Lake Charles,
‘ ) Louisiana. Without their technical assistance and hospitality, this work would not have
- been possible. Sidney A. Gauthreaux gave invaluable assistance during all phases of

I my work. During the preparation of this paper I was supported by a grant (70-1879)

j from the Air Force Office of Scientific Research to Dr. Gauthreaux and by a fellowship

from the Institute of Ecology, University of Georgia. This paper was presented as a

part of the Symposium on Bird Migration in the Region of the (iulf of Mexico held
during the 1971 Meeting of the Wilson Ornithological Society under the chairmanship
of George H. Lowery, Jr.

242

THE WILSON BULLETIN

September 1972
Vol. 81, No. 3

LITERATURE CITED

Able, K. P. 1971. Environmental influences on the nocturnal orientation and migration
of birds. Ph.D. Thesis, Univ. Georgia. University Microfilms, Ann Arbor, Michigan.

Batschelet, E. 1965. Statistical methods for the analysis of problems in animal
orientation and certain biological rhythms. AIBS Monograph, Washington, D.C.

Buskirk, W. H. 1968. The arrival of trans-Gulf migrants on the northern coast of
Yucatan in fall. Unpuhl. MS Thesis, Louisiana State University, Baton Rouge.

Gauthreaux, S. a., Jr. 1969. A portable ceilometer technicpie for studying low-level
nocturnal migration. Bird-Banding, 40:309-320.

Gauthreaux, S. A., Jr. 1970. Weather radar quantification of bird migration. Bio-
Science, 20:17-20.

Gauthreaux, S. A., Jr. 1971. A radar and direct visual study of passerine spring
migration in southern Louisiana. Auk, 88:343-365.

Gauthreaux, S. A., Jr., and K. P. Able. 1970. Wind and the direction of nocturnal
songbird migration. Nature, 228:476-477.

Gauthreaux, S. A., Jr., and K. P. Able. 1971. Nocturnal songbird migration. Nature,
230:580.

Griscom, L. 1945. Modern bird study. Harvard Univ. Press, Cambridge.

Kramer, G. 1953. Wird die Sonnenhohe hei der Heimfindeorientierung ver wertet?
J. OrnithoL, 94:201-219.

Lowery, G. H., Jr. 1945. Trans-Gulf spring migration of birds and the coastal hiatus.
Wilson Bull., 57:92-121.

Lowery, G. H., Jr. 1951. A quantitative study of the nocturnal migration of birds.
Univ. Kansas Publ. Mus. Nat. Hist., 3:361-472.

Lowery, G. H., Jr., and R. J. Newman. 1966. A continent wide view of bird migration
on four nights in October. Auk, 83:547-586.

Paynter, R. a. 1951. Autumnal trans-Gulf migrants and a new record for the Yucatan
Peninsula. Auk, 68:113-114.

Paynter, R. A. 1953. Autumnal migrants on the Campeche Bank. Auk, 70:338-349.

Petterssen, S. 1958. Introduction to meteorology. McGraw-Hill, New York.

SlEBENALER, J. B. 1954. Notes on autumnal trans-Gulf migration of birds. Condor, 56:
43-48.

Williams, G. C. 1945. Do birds cross the Gulf of Mexico in spring? Auk, 62:98-111.

Williams, G. C. 1947. Lowery on trans-Gulf migration. Auk, 64:217-237.

DEPARTMENT OF ZOOLOGY AND INSTITUTE OF ECOLOGY, UNIVERSITY OF GEORGIA,
ATHENS, GEORGIA. (PRESENT ADDRESS: DEPARTMENT OF BIOLOGICAL SCI-
ENCES, STATE UNIVERSITY OF NEW YORK, ALBANY, NEW YORK 12203.) 1

NOVEMBER 1971.

RECOGNITION OF NEST, EGGS, NEST SITE, AND
YOUNG IN FEMALE RED-WINGED BLACKBIRDS

Frank W. Peek, Edwin Franks, and Dennis Case

IN general, birds which build nests recognize and respond to their nest sites
and later their young but show little evidence of being able to specifically
recognize their nests or eggs (see Nice, 1943; Tinbergen, 1953; Davies and
Garrick, 1962; and Beer, 1970 ). In species which do not build nests, such as
the Common Murre [Uria aalge)^ both the egg and the laying site are specifi-
cally recognized and responded to ( Johnson, 1941). In the Tricolored Black-
bird {Agelaius tricolor), which nests in dense colonies, the adults feed any
young Tricolor placed in their nests and thus do not specifically recognize
their own young (Emlen, 1941, and Lack and Emlen, 1939). In species in
which parents recognize their own young the speed with which recognition
develops appears to be faster the shorter the time the young spend in the nest
(Davies and Carrick, 1962). The majority of the studies cited above and
others in the literature were done with non-passerines and investigated only
one or two factors of the nesting situation at only one period of the breeding
cycle. The present study examines in a passerine, the Red-winged Blackbird
[Agelaius phoeniceus) , the responses of the female Redwing to the nest site,
nest, eggs, and young throughout the entire nesting cycle.

METHODS

Experiments were carried out during May and June, 1968 and 1969 on a small (16.5
acre) fresh-water marsh near State College, Pennsylvania, The marsh contained 27 Red-
wing nests in 1968 and 12 in 1969. Observations were made with the aid of 7 X 50
binoculars and a 25X spotting scope from concealed locations at considerable distances
from the nests. The data on nestling vocalizations were obtained from two Redwings
taken from different nests in a marsh near St. Paul, Minnesota in July, 1970. Vocaliza-
tions were recorded on magnetic tape at 7'^ ips using a Uher 4000 Report-L recorder
and a Uher omnidirectional microphone.

RESULTS

1 Response to the nest. — Six experiments were conducted in which a female’s
entire nest along with its supporting vegetation was dug up and replaced with
II another Redwing nest from the same marsh. All nest substitutions were made
while the female was off the marsh, and thus out of sight of her nest. All the
i original nests were constructed entirely of sedge iCarex sp.) and were situated
on the tops of sedge tussocks. In the first three experiments the substitute
i nests closely resembled the originals in that they were also constructed of sedge
I and were situated on sedge tussocks. Each of the females upon returning to
I

i

I

1

24B

244

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

the substitute nest settled upon it without hesitation. In the fourth experiment
the female also settled without hesitation upon a substitute nest which, though
built on a sedge tussock, was largely constructed of cattail [ Typha sp. ) . In
the fifth and sixth experiments the substitute nests differed strikingly from
the originals in that they were constructed entirely of cattail and were sup-
ported by cattails rather than sedge tussocks. Upon returning to these nests
the females were at first quite distressed; however, both accepted the strange
nests within 15 minutes. Holcomb (1971 ) has demonstrated that female Red-
wings tolerate considerable alteration of their nests without abandoning them.
These observations are also consistent with those reported for other species.
For example, Lashley (1915) found that Sooty Terns [Sterna juscata) re-
sponded positively to any nest at the chosen site.

Response to eggs. — In these experiments the entire clutch of a female was
replaced with eggs from another nest. Egg substitutions involved interchanging
clutches containing the same number of eggs as well as clutches with differ-
ent numbers of eggs and also with young. Birds readily accepted substitute
clutches of eggs even though they invariably differed slightly in color and
pattern from the original clutch. They also accepted both increases and de-
creases in clutch size (three eggs substituted for four, two for four, four for
three, and four for two) . These findings agree with those of Holcomb (1971)
who found that female Redwings readily accepted artificial eggs similar to
their own and tolerated both increases and decreases in clutch size. Females
of the closely related Tricolored Blackbird also accepted eggs of other Tricolors
and tolerated alterations in clutch size ( Emlen, 1941). Under the criteria
of these experiments the female Redwing does not discriminate between her
own eggs and those of other Redwings or similar artificial eggs. She does,
however, discriminate against eggs of the Brown-headed Cowbird (Molothrus
ater) . During the course of the present study, two Cowbird eggs were found
covered over with nesting material. Friedmann (1963) also reported instances
of Redwings building over Cowbird eggs.

Female Redwings clearly were aware of change when eggs were substituted
for a mixture of day-old young and eggs, and vice versa; however, little else
can be said on the basis of one observation of each manipulation.

As already mentioned, the ability to recognize eggs varies with the ecology
of the species. Johnson (1941) interchanged the eggs of three Common
Murres nesting near each other. When the birds returned, each went to its
own egg and rolled it back to the original site. Murres lay their eggs on bare
rock cliffs where they are likely to roll; hence individual recognition of eggs
has adaptive significance.

Response to the nest site. — In one set of experiments five nests containing
eggs were moved various distances (2, 3, 5, 7, and 10m) while the females

Peek, Franks,
ami Case

NEST RECOGNITION IN REDWINGS

245

were away. Each nesl was moved only once and all movements were within
the original territory. In all cases females returned to the original nest site
before locating their displaced nests. On as many as 15 subsequent trips
females returned to the original nest site before flying to the relocated nest.
The nest displaced a distance of 10 m was abandoned.

These results show that female Redwings have an attachment to the site and
return by “habit” to their own nest sites even when the nests have been re-
moved. This is undoubtedly important in their willingness to accept even very
dissimilar nests placed on the original nest site as discussed above. The cues
which the bird uses to locate its nest site were not investigated.

These results agree with an experiment reported by Nero and Emlen (1951 )
in which a Redwing nest and eggs were moved for a second time a distance
of 3 m while the female was absent. Upon returning she went first to the site
where the nest had last been located and then to the site from which it has been
moved the previous day. She finally located the nest on its new site and ac-
cepted it. Nero and Emlen also report a number of other experiments in which
Redwing nests containing eggs and/or young were moved 1.5 or 2 m while
the female watched. In these cases the females returned directly to their nests
I rather than to the former sites. In these experiments females even followed
I nests which were moved across territorial boundaries. In experiments with
j the Sooty Tern (Lashley, 1915) and House Sparrow {Passer domesticus)

I (Nice, 1943), however, birds returned to former nest sites rather than to nests
! displaced short distances.

i A second set of experiments was done with two females whose nests, each
Ij containing three eggs, were built in sedge tussocks. While each female was
I away, her nest and eggs were moved to a position 4 m from the original nest
, site (within the same territory) and replaced with another nest ( Gattail in
! both cases) also containing three eggs. The results were essentially the same
j for each bird. When the female returned to her nest site, she settled on the
ji new nest, got off and returned by the same route several times during the
S next 3 hours. One bird also flew over to her own nest at the new site but
i finally settled on the new nest at the old site and remained there for a normal
j incubation bout (30 min average duration). The original nest and eggs were
1 then moved back to within 0.5 m of the new nest. The female continued to
I return to the new nest on the original site for 2 hours despite the presence
1 of her own nest and eggs 0.5 m away. The new nest and original nest were
then interchanged; the original nest was now back on the original site. The
female returned without hesitation to the original nest and site. The two nests
were again interchanged after the female left and the female continued to re-
turn to the original nest site, now containing the new nest and eggs, for the
rest of the afternoon. On the following day, both females were returning to

246

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Response

Table 1

OF Female to Substitute Nestlings and

Displacement of Own Nestlings

Female

Age of Nestlings
Removed and Placed
in a Nearby Nest
( days )

Age of
Substitute
Nestlings
( days )

Response of
Female

1

1

2

settled on nest with no hesitation

2

2

1

/f

3

2

3

4

3

2

»

5

3

4

6

4

3

7

6

7

8

7

6

accepted but showed distress

3

10

11

followed young to new nest

4

11

10

//

5

10

11

6

11

10

99

9

10

none substituted

10

11

//

99

their original nests, which were 0.5 m from the original sites. The replace-
ment nests and eggs were still at the original sites. Both females eventually
fledged young from their original nests.

These results show that the female is more strongly attached to her nest
site than to her nest and eggs, but that she discriminates against a substitute
nest and eggs if her own are not far removed from the original site.

Response to young. — The female Redwing’s response to her young was in-
vestigated by replacing a female’s own young with an equal number of nest-
lings from another nest (in two cases a female’s young were moved and no
replacement was made). The substituted nestlings were within a day of being
the same age as the female’s own young. In all cases the female’s own young
were placed in a nest 3 to 6 m away within the same territory. The reaction
of the female depended upon the age of the nestlings at the time the manipula-
tion was made (Table 1). If the female’s own young were less than 7 days
old, the female settled upon the nest with no hesitation. The female whose
nestlings were 7 days old apparently had developed some degree of recogni-
tion of her own young and was disturbed by the interchange. By the time the

Peek, Franks,
and Case

NEST RECOGNITION IN REDWINGS

247

young were 10 days old, the female specifically recognized her own young
and followed them to their new location.

Females 5 and 6 (Table 1) were both nesting in the same male’s territory,
6 m apart. Over a period of 14 days their nests, then their eggs, and then
their young (at two ages) were interchanged. In agreement with results dis-
cussed above, interchanging nests and eggs had no measurable effect upon
the females; both females readily returned to their original nest sites which
contained either a different nest or different eggs. The first time the nestlings
were interchanged at ages 3 and 4 days, both females readily accepted the
foster nestlings. When the nestlings were again interchanged at ages 10 and
11 days, the females immediately switched nest sites, remaining with the nest-
lings they had cared for during the previous 7 days (these nestlings were not
the young they had hatched and initially brooded for 3 and 4 days, respec-
tively). The females thereafter stayed with the young they had followed to
the alien nest site until they fledged 1 or 2 days later. The females had, during
a 7-day period, formed a specific attachment to the 3 and 4 day-old foster nest-
lings. Females 3 and 4 (Table 1) were also nesting within one male’s territory
(4 m apart). Their young were successfully interchanged at 2 and 3 days of
age. When the young were again interchanged at 10 and 11 days of age, the
females switched nest sites, as did females 5 and 6, and remained with their
young until they fledged.

These results agree with those discussed by Davies and Garrick ( 1962 ) for
a number of gull species. The gulls learned to recognize their own young
before the young left the nest. Nice’s (1937) Song Sparrows (Melospiza
melodia) behaved similarly. She found that parents did not recognize their
own young under 7 days of age. Alley and Boyd (1950) found that parent
European Coots [Fulica atra) gradually learned to recognize their own young
over a period of 2 weeks after the young were able to swim and leave the nest.
The following species have been shown not to recognize their chicks, at least
in the nest: Kittiwake {Rissa tridactyla) (Cullen, 1957); Tricolored Black-
bird (Emlen, 1941) ; and Black Phoebe (Sayornis nigricans) (Kinsey, 1935).

Beer (1970) has pointed out that experiments in which young are inter-
changed provide inconclusive evidence that parental recognition has occurred.
The possibility exists in such experiments that the young might discriminate
I among adults or might react to being placed in a strange nest, with the result
j that their behavior ( rather than any individual characteristics ) marked them
. as foreign and caused the strange adults to reject them. However, specific
recognition of young is demonstrated in the present study when females fol-
ij lowed their own young to different nest sites.

The behavior of females which followed their young to new nest sites
I strongly suggested that they used the vocalizations of the young to find them.

i

I

248

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

After an interchange of young had been made, the females first hovered over
their own nests for a short time, then flew directly to the nest which contained
their own young, and eventually settled on it. Since the nests were situated
deep in sedge tussocks, the young were concealed except from directly over-
head, making it impossible for the female to see them until she was directly
over the nest.

Observations were also made on two captive Redwings taken from different
nests at age 10 days. In agreement with Nice (1950), these birds gave loud
location notes at approximately hourly intervals, and ceased calling when
fed. Tape recordings of their calls were made during their tenth and eleventh
days of age. Sonagrams show that the character of the calls varied little within
an individual but were distinctly different between individuals. The location
call presumably enables the parent to recognize and find its young even though
the latter are motionless and hidden in tall vegetation. The call may also
stimulate the parent bird to feed the young.

CONCLUSION

Tinbergen (1953) introduced the terms “specific recognition” and “non-
specific recognition” when referring to responses of parent birds to factors in
the nesting situation. Nonspecific recognition refers to those factors which
are innately recognized as belonging to the species. For example, a wide range
of Red-winged Blackbird eggs would be recognized nonspecifically by a female
Redwing and therefore would be appropriate for incubation. Thus, a moderate
range of eggs can satisfy her. Markedly differing eggs, such as those of cow-
birds, are not accepted.

In the present study, female Redwings were found to recognize the nest,
eggs, and young under 7 days of age nonspecifically. Replacements of any
of these by counterparts from another Redwing nesting situation were quickly
accepted.

Specific recognition of factors in the nesting situation must be learned. At
least one factor or aspect of the nesting situation must be specifically recog-
nized or parent birds would stop at the first conspecific nest encountered rather
than returning to their own nests. Female Redwings were found to recognize
specifically the nest site and young older than 7 days. Females returned to
their specific nest sites, and after the young were about 7 days old, learned
to recognize them or their calls specifically. At this time the female becomes
more strongly attracted to the young than to the nest site, for she will abandon
the site to follow the young. Since the female Redwing feeds her young after
they fledge, this transfer of attachment must occur prior to the time the young
leave the nest. The present study shows that this happens when the young are
about a week old.

Peek, Franks,
and Case

NEST RECOGNITION IN REDWINGS

249

SUMMARY

Responses of female Red-winged Blackbirds to substitute nests, eggs and young, and
to displacements of nests and young were investigated. Females show a strong attach-
ment to nest sites throughout the nesting period. They preferred to remain at the nest
site even though the nest, eggs, and young (under 7 days old) were replaced with counter-
parts from other Redwing nest situations. When young older than 10 days were displaced
from the nest site, females abandoned the site and followed the young. Female Redwings
therefore learn to recognize their young during the period they are in the nest. The
earliest females were found to show signs of recognizing their young was 7 days post-
hatching. This recognition is probably partly based upon the location call which is
given only by older young. Though the structure of the location call remained the same
from one utterance to the next for an individual, it differed markedly between individuals.

LITERATURE CITED

Alley, R., and H. Boyd. 1950. Parent-young recognition in the Coot Fulica atra. Ibis,
92:46-51.

Beer, C. G. 1970. Individual recognition of voice in the social behavior of birds. In

iLehrman, D. S., R. A. Hinde, and E. Shaw, eds.. Advances in the study of behavior,
3:27-74. Academic Press, New York.

Cullen, E. 1957. Adaptations in the Kittiwake to cliff-nesting. Ibis, 99:275-302.
Davies, S. J. J. F., and F. Carrick. 1962. On the ability of Crested Terns, Sterna bergii,
to recognize their own chicks. Australian J. Zook, 10:171-177.

Emlen, j. T., Jr. 1941. An experimental analysis of the breeding cycle of the Tricolored
Redwing. Condor, 43:209-219.

Friedmann, H. 1963. Host relations of the parasitic cowhirds. U. S. Natl. Mus. Bull.,
No. 233.

Holcomb, L. C. 1971. Nest building and egg laying by Redwinged Blackbirds in re-
il sponse to artificial manipulations. Auk, 88:30-34.

Johnson, R. A. 1941. Nesting behavior of the Atlantic Murre. Auk, 58:153-163.
Kinsey, E. C. 1935. Parental instincts in Black Phoehes. Condor, 37:277-278.

Lack, D., and J. T. Emlen, Jr. 1939. Observations on breeding behavior in Tricolored
Red-wings. Condor, 41:225-230.

Lashley, K. S. 1915. Notes on the nesting activities of the Noddy and Sooty Terns.
Carnegie Inst. Wash., 211:61-83.

Nero, R. W., and J. T. Emlen, Jr. 1951. An experimental study of territorial behavior
in breeding Red-winged Blackbirds. Condor, 53:105-116.

Nice, M. M. 1937. Studies in the life history of the Song Sparrow. I. A population
study of the Song Sparrow. Trans. Linnaean Soc. N. Y., 4:1-247.

Nice, M. M. 1943. Studies in the life history of the Song Sparrow. II. The behavior of
the Song Sparrow and other passerines. Trans. Linnaean. Soc. N. Y., 6:1-328.

1 Nice, M. M. 1950. Development of a Redwing (Agelaius phoeniceus) . Wilson Bull..
’ 62:87-93.

Tinbergen, N. 1953. The Herring Gull’s world. Collins, London.

DEPARTMENT OF ANIMAL SCIENCE, UNIVERSITY OF MINNESOTA, ST. PAUL, MINNE-
SOTA 55101, DEPARTMENT OF BIOLOGICAL SCIENCES, WESTERN ILLINOIS UNI-
VERSITY, MACOMB, ILLINOIS 61455, AND OFFICE WATER QUALITY PROGRAM,
3090 BROADWAY AVENUE, CLEVELAND, OHIO 14115, 15 OCTOBER 1971.

COMMUNAL WINTERING OF A SANDHILL CRANE
WITH JAPANESE CRANES IN HOKKAIDO, JAPAN

Hiroyuki Masatomi

IN the course of my ecological studies on the Japanese Crane, a Sandhill
Crane [Grus canadensis) was found 18 January 1970 at Shimo-setsuri,
Tsurui village, Kushiro district, Hokkaido, Japan, feeding with many Japanese
Cranes ( Grus japonensis ) in a field where food was scattered for the cranes.
This is the first record from Hokkaido, and the second for Japan, of this Ne-
arctic species. This paper deals with observations made on the behavior and
relationship of these two species, supplemented by additional records made by
the people who daily feed grain to the birds.

COLORATION OF THE INDIVIDUAL OBSERVED

The plumage coloration of this Sandhill Crane changed gradually during
the winter as follows:

The head was still feathered in February. The forehead and lores became slightly
bald in early April and more redness appeared in early May hut was definitely not as
pronounced as in adults. The chin and malar regions were more whitish than the sides
of the neck. In February the hack feathers had dark rachises, were gray, tipped with
tawny. In April they appeared to he neutral gray without the tawny tips. However,
most wing coverts retained tawny-colored tips up to early May. The abdomen was some-
what paler than the breast. The primaries were dark.

The coloration in early February generally was similar to that of a hand-reared bird
of about three months of age described by Walkinshaw (1949:16-20), but molting and
the acquisition of the red forehead appeared about six months later. The red generally
begins to appear during the first fall in some Sandhill Cranes hut may not develop until
spring with some others 1 Walkinshaw, pers. comm.). The redness or baldness of the
foreheads of the Japanese Crane often is variable even among synchronously hatched
individuals ( Masatomi, unpubl.) .

The exposed culmen was blacker than those of the Japanese Cranes, but the basal half
of the lower mandible was pale gray-olive. The entire bill and especially the lower man-
dible gradually became lighter colored. The legs were dark greenish-black or nearly
black. The eyes were hazel.

ROOSTING AND FEEDING RANGE

It is not certain just when this bird arrived. In late September or early
October 1969, one of the regular feeders of the Japanese Cranes noted a
strange smaller dark crane feeding with four Japanese Cranes at Naka-setsuri,
about 20 km north of Kushiro city (Figure 1,A). This was probably the
first observation. In late November this Sandhill moved to Shimo-setsuri, 7
to 8 km south of the first location. Here many Japanese Cranes, stay in small

250

HiToyirkV SANDHILL CRANE WINTERING IN JAPAN 251

Fig. 1. (Left) Feeding ranges of flocks of Japanese Cranes in January to March (solid
line) and in April (dotted one). X: roosting places used by the majority of Japanese
Cranes wintering in this area. (Right) Some of the feeding ranges of the Sandhill Crane.
Various lines show the Sandhill Crane’s flight routes on each day. Circular dots: roosting
points. Numbers given to each roosting point: change of settlements, 1. October, 2.
January, 3. February, 4-5. March, and 6. April.

(

groups during the colder part of winter ( Figure 1,B). After that the Sandhill
Crane fed at Watanabe’s feeding place at Shimo-setsuri, eating corn every
day, until 17 April 1970 when it suddenly appeared at Narukawa’s feeding
.place at Shimo-hororo, 3.5 km south of the second place (Figure 1,0. It
arrived at this place at least once daily from then until 6 May. A similar bird
seemed to be observed in May on the opposite side of the marsh, about 11

Table 1

First Arrival and Last Departure at Siiimo-Setsuri Feeding Place

252

THE WILSON BULLETIN

September 1972
Vol. 81, No. 3

O

o

o

o

o

o

o

o

X

3

1

O

LO^

8

§

o

s

8

§

§

1

1

U

1

1

co"

o<r

09

oC

1

Lo"

1

1

LO

r-

vO

o

ON

Q

1

1

1

t

„

(N

09

I

LO

1

1

Z

CC!

C/2

cA

Z

Z

Z

2U

y °

lO

CO

00

q

q

09

o

cq

£ §

I

1

i

csi

1

00

I

LO

1

1

H*'

>.

X

■5

no

L,!

no

Su

no

Lh

U

I

1

3

C3

Ti

3

rt

3

3

1

r3

1

1

rt

y

1

1

O

o;

03

03

o

03

1

<V

1

1

0

0

G

G

G

G

G

0

D.F.

1

1

w

w

C/2

c/2

w

w

w

1

1

1

1

"a

»

1 ^

1

1

to

1

O

1

CO

09

1

1

1

1

X?

1

1

lO

LO

1

1

CO

crj

1

1

1

1

z

1

1

O

O

09

CO

o

1

1

H— 1

1

I

CO

CO

09

09

1

1

y

C\

CO

CO

(M

o

CO

On

CO

CO

CO

CO

1

f.

Tf

LO

LO

q

C9

o

cC

8

O

o

o

LO

LO

LO

c/3

o

o

o

o

o

O

O

o

o

o

o

f.

o

LO

o

lO

o

o

(N

CO

LO

o

LO

LO

7|

1

1

00

Q

<^’

o\

ON

g

NO

NO

1

1

1

o

o

o

o

o

y

E

H

o

LO

CO

CO

o

09

h-

CO

q

CO

T

1

1

O'

O

Co’

o

C30

1

1

1

1

O

o

c

c

c

c

-a

«

S-i

3

i-l

3

Ul

Cu

Cl.

a,

a

<n

C3

*~-s

3

CO

1—:

<

<

<

<

CO

On

o

(M

,_i

(M

H

LO

LO

03

r-

%•

1

(M

CM

CS

09

09

09

3^ e i

<u 3 m

5 S

a S D

CS rt

<u Q

- "I

OJ T3
"c rt

I 5 ^

i &!

S 2

rt S ^

I
S -=^
-s

rt 5 .-

•- 1 w

t I

.2 -

2: -c ^

tS a;

’tr

H3 .2-
C tec
es C

C/5 •- uh

g ^ y

2°
MU •:
.5 Du
+3 o> ”

M I ^
2 « •

(S ^ ^

e« OJ
05 2 y

C ai *:

y y
y ■£
c £

^ .. £

y • y

PS

C _ M

y M-r
^ .£ X

£ P £

3 C I

Z £ £

of

y >.

1c
a y
y y
T3

■S? 2

6 2

-oU

^.5 y
c

.. >, rt

S ^ u

CS efl

C o M "C

c a y c

-a £ 5'^

« a.1

^ Bo

'C 2 y

'" to

IS"

^ ^ -S

« y ^

S gj

y a .

.2 '

’>

to ^

^ i ■£ ^

c« £ c
U c -E

C y
— y

y ^
H H

Hiroyuki SANDHILL CRANE WINTERING IN JAPAN 253

Masatomi

X

lC

lO

lO

o

o

LO

o

O

1

o

1

LO

3

lO

LO

ON

l-H

p-H

ON

1

o

1

Tf

H-I

l-H

l-H

co"

W.D.

1— 1

0^

(N

l-H

t— 1

o

•rj'

l-H

w

W

w

z;

w

z

(f)

U

?!

(n

z

(70

w

1

2u

OJ O

q

q

cq

q

CO

q

CM

o

00

CM

1

00

si

fO

LO

1

CO

CO

1

co’

r-'

1

CO

CO

'T

o

1

rf<’

H

u

3 ^

p£:

’TS

L-i

t-i

Li

T3

no

Li

'T2

Li

ca

3

ca

ea

ea

3

3

3

3

3

c3

0>

o

OJ

o

13

O

O

o

H

3

O

‘3

u

G

G

G

G

G

G

G

CTJ

CJ

G

OS

u

'TS

(U

W

CT)

1

.s

w

w

w

1

W

w

w

W

w

1

u

c

Q

W

(n

C/i

C/)

1

in

in

o

U

>-

3

u

O

a

DO

CO

VO

vO

vo

LO

t--

LO

00

CM

Da

<

Q S

ID

CO

LO

rf

CO

CO

CM

H

Z

<N

CO

CO

(N

VO

o

ON

o

1

o

p?

l-H

r?

CM

1

lO

VO

r-

O

O

CM

00

l-H

LO

LO

CO

rH

l-H

CM

O

q

CM

q

q

LO

lO

q

c

o

vo'

VO

VO

t^’

r^*

r-

r-

i>!

CO

s

c/a

l-H

rf

o

CO

O

CM

CO

O'

LO

VC

O':

lO

LO

?.

?!

1

l-H

q

1

O

1

1

VO

VO

o

VO

1

CO

CO

1

o

1

1

r-H

l-H

I-H

l-H

l-H

1— H

l-H

(D

' — '

' — '

' — '

' — '

' ^

w-

' — '

' '

' — '

' ^

' — '

S

H

r^

o

CO

CO

CO

o

VO

CO

o

o

cs

q

q

CO

CM

LO

rH

Tf<

1

q

CM

VO

VO

G

vo

r-

00

00

1

00

CO

l-H

l-H

c
ca
•— s

c

ca

c

ea

c

ea

-Q

tlH

-a

3

(Jh

Li

ra

l-l

ea

(h

3

S

Li

a,

<

U

a

<

a

<

Li

a.

<

00

Ov

o

CM

CM

rf<

lO

lO

00

■rt

CNJ

CM

CM

CM

rH

CM

CM

CM

254

THE WILSON BULLETIN

Septemlier 1972
Vol. 84, No. 3

km east of Shimo-hororo. Thus this Sandhill Crane wintered in marginal
regions of the Kushiro Marsh from early October 1969 until early May 1970,
changing feeding regions at least twice.

As it changed its feeding regions, it also roosted in several different points
along the Setsuri and Hororo rivers (Figure T) . Since the river never froze
in many places, it was possible for the bird to feed in the river during the
early mornings prior to its appearance at the feeding places. It also fed there
on some evenings after returning. This bird roosted apart from the communal
roosting region used by the majority of the Japanese Cranes, sometimes for
several weeks or more, but often a pair of Japanese Cranes with their young
will do the same. The Sandhill became affiliated with one of these groups and
remained apart from the main group.

Because of the unusually deep snow at Shimo-setsuri (about 60 cm on 21
February, compared with 30 cm during normal years ) the fields were snow-
covered until mid-April. But the Setsuri River, 2 to 3.5 m wide at the roosting
points did not freeze even in the coldest months (-20° C in February). The
river here is shallow, wide and has embankments. The food of the Sandhill
Crane was not known but some edible roots and rootlets as well as green
parsley (Oenanthe stolonijera) and sticklebacks {Pungitius pungitius) were
available in addition to the corn on the feeding stations.

DAILY ACTIVITIES AT FEEDING PLACES

Every morning at the night roost, the Sandhill searched for food or preened.
Then when its adopted “family” of two adult and two young Japanese Cranes
flew from the night roost, it joined them. Although it did not always go to
the feeding stations in the very early morning it appeared there at least once
daily during the winter. Records of earliest daily arrival and latest daily de-
parture at the feeding regions are given in Table 1. The chronological sequence
of its activities at Shimo-setsuri, on several different days are given in Figure
2.

On 25 March 1970 there had been a snowfall of 1 cm the previous night. The sky
was clear, temperature -11.4° C at 07:00. Two Japanese Cranes flew from the Ashibetsu
River to Shimo-setsuri feeding station at 06:50. Between then and 08:00, 32 Japanese
Cranes, including five young of the year, assembled there, one after another. The Sandhill
came from the east with its “family,” landed, and fed for awhile. When nine Japanese
Cranes came to the feeding place, the male of the “family,” showed a threatening posture
against them. The “family” gradually moved away 150 m eastward on foot. Sometimes
the Sandhill rested, preened, fed, yawned, stretched its wings and legs, fluffed its feathers
hut then remained inactive until 09:55. At 09:59 the “family” flew to the region near
the Setsuri River where they foraged. Heavy snow fell between 13:40 and 15:10. At
15:50 the birds came flying hack in the following order- male-female-young-Sandhill-young.

H iroyiiki
Masatomi

SANDHILL CRANE WINTERING IN JAPAN

255

0^(3 CLEAR CLOUDY ^ SLEET ^ SNOW

Fig. 2. Chronological sequence of the Sandhill Crane at Shimo-setsuri feeding place.
Horizontal hatching: stay at feeding place. Number at each weather mark is temperature
(°C). Histogram at right shows the total duration of stay at feeding place.

Approaching the feeding station, they landed then, walked the last short distance where
they fed on corn. Later they sauntered to the east end of the field, preened, and rested.
Later they joined other cranes and all began to dance, chasing each other, jumping high
into the air. The Sandhill did not dance, hut rested and watched nearby. At 16:55 all
birds went to the west side of the field where much corn had been scattered. The Sandhill
began feeding at 17:10, then rested, standing on one leg. Heavy snow fell again from
17:20 to 17:40. At 17:46 the male of the “family” group flew to the roosting ground,
followed by the three members of his family. The Sandhill was feeding so eagerly, that
it did not notice they had departed for a moment. But soon it took off after them.

The flight order was variable. Sometimes the Sandhill was in the center,
sometimes behind. Excluding several double trips to Naka-setsuri from the
Shimo-setsuri feeding place, its daily feeding ranged little as shown in Figure
1. Most of the Japanese Cranes gathered at the Shimo-setsuri feeding station,
flew southwest or west to drink or to rummage out food along the Ashihetsu
River, but the “family” seldom flew to the region. Therefore, the feeding
range of the Sandhill in Figure 1 is identical with that of the “family,” during
January, February, and March, and of the young when they were chased away
by their parents in early April.

256

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

At the earliest arrival each morning a photometer registered between 8,500
and 72,000 lx and at evening departure time registered under 190 Ixs. But
as spring approached, the Sandhill came earlier and remained later. The tem-
perature at departure time was between -3° C and -7° C between January
and March (Table 1 ) . The morning departure seemed later than that recorded
during the same months by Walkinshaw ( 1949:36-42) at Roswell, New Mex-
ico but this was probably because of lower temperatures at Shimo-setsuri.
Japanese Cranes tend to waste much time on the roosting place after sunrise
during severe cold mornings ( Masatomi, unpubl. ) . The time of evening arrival
on the roosting region in January varied little from Walkinshaw’s observa-
tions. The Sandhill usually joined the “family” directly on the roosting spot,
after sunset. ( The sun set 20 minutes earlier behind the west ridge than official
sunset.)

RELATIONS WITH JAPANESE CRANES

Relation with the ^^jamily'' members. — The Sandhill relationship with the
“family” members can best be described in three stages:

a) Lormation of interspecific association: How the Sandhill joined with
this family of G. japonensis consisting of a pair and their two young cannot
be explained. When it was first observed, it already was with the group at
Naka-setsuri, so it apparently joined them even in September or early October.
Unfortunately it was considered to be an undergrown young japonensis or a
Gray Heron iArdea cinerea) until I encountered it on 18 Januarv 1970.
Japanese Cranes are considered as residents in Hokkaido but there may be
a movement of some birds between Kushiro and Nemuro. It is thus not com-
pletely impossible that the Sandhill met the family while migrating westward in
Nemuro, but this is probably only conjecture.

b ) Maintenance of the relationship with a definite “family”: The Sandhill
associated with the “family” of the Japanese Crane in all activities-roosting,
feeding, flying, resting, etc. until 7 April. Nevertheless, it seemed that they,
especially the parents, did not treat the Sandhill as a genuine member or
young of the family, no matter how rarely they turned on it by a threatening
posture, by chasing or other hostile activities. If it was threatened or chased,
the same as their own young, the male responded by counterattacks against the
attacking bird. Some birds approached it with light threatening posture
and were immediately attacked by one of the “family” adults, but it was diffi-
cult to distinguish between these attacks and weak aggressions frequently ex-
pressed only to maintain interindividual distance or to defend a good feeding
spot.

The parents never flew without their youngsters until the new breeding sea-
son approached, but the Sandhill was sometimes tardy as described above.

Hiroyuki

Masatoini

SANDHILL CRANE WINTERING IN JAPAN

257

It also separated several times from the “family” during February and March.
At the Shimo-setsuri feeding station, the members, especially the male, of the
“family” occasionally approached the Sandhill with or without, light threaten-
ing postures, and the latter always withdrew. Such approach-avoidance, how-
ever, was not restricted for it was rather common between G. japonensis in
a feeding flock. Although generally G. canadensis avoided G. japonensis, one
young jumped aside two or three meters with half-spread wings when the
former approached it with light threatening posture on 22 February. The
male of the “family” approached in threatening posture toward the Sandhill
in late March. The Sandhill ran away with the first threat, but I never saw
the male attack the Sandhill as he did his own young when the breakdown of
family ties was made in late March and early April.

c) Relationship with the post-juveniles driven away by the parents: Accord-
ing to the feeders, the “family” came on 7 April to the Shimo-setsuri feeding
station at 11:00. Later, only the Sandhill, fed between 14:00 and 17:00. The
next day I found only two adults there and after 9 April, three young, ( i.e.
the Sandhill, and two Japanese Cranes. ) They came once or twice daily. Young
G. japonensis sometimes danced, facing each other on the feeding grounds
after March and the Sandhill joined in these dances, somewhat different from
the regular courtship display, in April. On 17 April, during the afternoon,
after two young Japanese Cranes had been dancing, the three young of the
“family” began dancing after they had eaten. They bowed, bounced up and
down, stabbed the ground, ran about flapping their wings, all in one section
of the feeding region which still was covered with patches of snow. The Sand-
hill danced very similarly to G. japonensis, either with the young birds or
alone. It stabbed the ground, at times picked up objects which it threw into
the air. After bowing once or more it bounced 30 to 50 cm into the air, but
not as high as described by Walkinshaw ( 1949:32-36), with legs held stiffly,
and wings flapping. When it danced with young Japanese Cranes, it bowed
repeatedly, tried to attack one of them, then they both jumped into the air
facing each other similar to comrades of japonensis.

At the third feeding station such a dance was observed until early May
when the three began separating. Often, each flew alone, so that it was im-
possible to differentiate the “family” young from others also abandoned by
their parents. All young of the year often assembled into a temporary flock
immediately after being abandoned. On 3 May the Sandhill took off with
two Japanese Cranes for the roosting site and four days later it disappeared.

Relations with other Cranes. — Japanese Cranes forming the winter flock
seemed to take no special interest in the Sandhill. They were not familiar
neighbors, nor were they strong op})onents. But when foraging over the feed-
ing grounds, during the colder months, the Sandhill usually avoided them.

258

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

especially when they approached him. In contrast, however, they often showed
decisive resistance against other neighbors who drew too near when they
were eating. The Sandhill stretched its neck forward, pointing it’s bill against
the other bird and called a shrill Bui-puy-puy-puy-puy-puy . It then raised its
body, stood in an upright position, and by this posture caused the other birds
to retreat hastily away. A similar behavior was observed the next day when
the bird stood in nearly erect posture, and called Gui-puy-puy-puy-puy-puy
toward a Japanese Crane which passed slowly alongside it. The japonensis
was startled slightly. A few approaches and more avoidances were observed
in April. The Sandhill became much more self-reliant at this time.

On 24 March the Sandhill leaped half-heartedly three times into the air as
if fleeing from two year-old opponents who began dancing in the flock. Oc-
casionally he danced with young japonensis at the third feeding ground, but
it was uncertain whether they were its former “family” mates or not.

DISCUSSION

Although a specimen of Grus canadensis^ without date and locality was de-
scribed from Japan by Temminck and Schlegel (1849:117-118) as la g;rue
commune a long bee (G. cinerea longirostris) , this record was not adopted
in any authoritative list of Japanese birds (such as Austin and Kuroda, 1953;
Ornithol. Soc. Japan, 1958) because of the poor data of the specimen (cf.
footnote in the latter paper ) .

There was no record of this species for over 100 years until Takano (1964)
unexpectedly found a Sandhill Crane wintering with White-naped Cranes ( Grus
vipio) and Hooded Cranes [G. monacha] at Arasaki, Kagoshima, Kyushu on
9 December 1963. This crane was an adult, but of unknown age. It remained
there from 10 November 1963 until 26 February 1964.

Although the present case is the first Hokkaido record, the bird may have
wandered in more often and was mistaken for a heron, a small Japanese Crane
or a Common Crane {G. grus).

Several color slides taken by me were examined by Walkinshaw. He wrote
“This bird from its size, very short bill and tarsi, must be a Lesser Sandhill
Crane [G. c. canadensis) . . .” The Kyushu bird was similar to the one in
Hokkaido but its subspecific identity was not determined.

According to Takano ( 1964) the Sandhill at Arasaki always moved in asso-
ciation with G. vipio, a larger species. But it often drove away G. monacha
which is much more like it in size and color, when they accidently approached
it. Moreover, even in flocks of G. vipio it was alone and often pecked at by
vipio (Ogasawara, 1970:7). On the other hand the 1970 Sandhill always
behaved as though it were a member of the “family” of japonensis and its
activities were synchronized with the movements of this family. It might be

Hiroy iiki
Masatonii

SANDHILL CRANE WINTERING IN JAPAN

259

in the category stated by Rand (1954) as “casual associations of no benefit,”
but the Sandhill probably received benefits from japonensis by joining them
on both roosting and feeding regions.

In appearance the “family” adopted the young Sandhill Crane as their
member but apparently, from their behavior, not as a genuine member. They
were indifferent to it but tolerated it and showed no definite hostility towards
it. Yet, in late March and early April they acted as though it was a stranger.
Leadership of the group was retained in all cases by G. japonensis, chiefly the
male. Hence the association must have been made and maintained by the
Sandhill from the tendency for intense gregariousness of the species. The
tendency of some birds to associate with, and be tolerated by birds larger
than they, in non-breeding flocks is not uncommon. For instance, several
sandpipers (Nichols, 1931), Bean Geese {Anser jahalis) with White-naped
Cranes (Shimomura, 1955 ), and a Sandhill Crane with White-naped Cranes
(Takano, op. cit. ) .

The Sandhill Crane that wandered into Kyushu did not associate with G.
vipio as intensely as did the bird in Hokkaido did with G, japonensis, but the
difference may have been because of the difference in ages. The bird in
Kyushu was not a bird of the year as was the one in Hokkaido. The Whooping
Crane ( G. americana ) , very similar in size to G. japonensis, does not tolerate
spoonbills, herons, or egrets within several hundred yards of the nest location
while these birds are tolerated in established territories in winter although
Sandhill Cranes are not (Allen, 1952:145, 188-191 ). However, at times Sand-
hill and Whooping Cranes gathered at fresh water on Aransas Refuge without
indications of fighting at all. On the other hand G. japonensis pays no marked
attention to other birds on either winter or summer territories, except birds
of prey. Eastern Gray Herons ( Ardea cinerea jouyi ) , Whooper Swans ( Cygnus
eygnus), and other birds forage or roost within the same territory of G.
japonensis (Masatomi, 1970). Emlen (1952) pointed out that the form char-
acteristics of homogeneous bird flocks were determined by the interplay of
positive and negative forces associated with gregariousness and intolerance.
Such tolerance (as described above) of the Japanese Cranes might be one of
the causes which made unusual association between two different species
possible.

The Sandhill Crane stayed longer in Hokkaido than did the one in Kyushu.
Possibly because Kushiro is 1,8(K) km northeast from Arasaki. Since this
Nearctic species breeds in northeastern Siberia, it was once recorded on 20
I May on Commander Islands and observed at Nizhne-Kamchatsk in Kamchatka
(l)ement’ev et al., 1969:133-131) indicating possible migration of Asiatic
' stragglers.

260

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

SUMMARY

A young-of-the-year Sandhill Crane {Grus canadensis probably canadensis) wintered
with a “family” of Japanese Cranes (G. japonensis) consisting of a pair and two young,
near Kushiro, Hokkaido, Japan. The group formed part of a wintering flock of the latter
species. This is the second record of this species for Japan, the first for Hokkaido.

The Sandhill and it’s associated “family” of Japanese Cranes changed their feeding
range twice or more during the winter, and correspondingly changed their roosting sites.

In the spring, when the family broke down, the Sandhill associated with the two young.
At times it danced lightly with them. Some behavioral associations between the family
and the Sandhill or its relationship with others in the flock are given and discussed
briefly. The attitude of the “family” and other cranes was generally indifferent to it.
Therefore, the formation and maintenance of this association depended on the Sandhill’s
positive attachment to the “family” and the general tolerance of G. japonensis to smaller
birds. But the actual process of attachment and time of arrival were not known,

ACKNOWLEDGMENTS

I am grateful to Dr. Lawrence H. Walkinshaw, who made helpful suggestions on the
identification of the species, and Dr. Shoichi Sakagami for their valuable advice on
the improvement of the manuscript. Dr. Sakae Tsunetnatsu, Dean of our College, in-
cessantly helped me in the course of the study. I also appreciate so much the support
given by Dr. Shoichiro Satsuki and his family in Kushiro.

LITERATURE CITED

Allen, R. P. 1952. The Whooping Crane. Natl. Audubon Soc. Res. Rept., 3:1-246,
Austin, 0. L., Jr., and N. Kuroda. 1953. The birds of Japan, their status and distri-
bution. Bull. Mus. Comp. Zook, 109:279-637.

Dement’ev, G. P., and N. A. Gladkov (Ed.). 1969. Birds of the Soviet Union, Vol.

2. Jerusalem, Israel Progr. Sci, Transl.

Emlen, J. T., Jr. 1952. Flocking behavior in birds. Auk, 69:160-170.

Masatomi, H. 1970. Tancho no seikatsu ni okeru sho-mondai 1. J. Bibai Agri. Engi-
neer. Coll., 1 :37-45.

Nichols, J. J. 1931. Notes on the flocking of shorebirds. Auk, 48:181-185.
Ogasawara, a. 1970. Yacho no shiki. Tokyo, Asahi Shinbun.

Ornithological Society of Japan. 1958. A Hand-list of the Japanese birds. Herald
Co., Tokyo.

Rand, A. L. 1954. Social feeding behavior of birds. Fieldiana, 36:1-71.

Shimomura, K. 1955. Bird report from Arasaki, Kagoshima, Kyushu. Tori, 14:33-36.
Takano, S. 1964. Arasaki ni kanada-zuru torai su. Yacho, 29:21.

Temminck, C. T., and H. Schlegel. 1849. Aves, in Siebold’s Fauna Japonica f photo
copy). Tokyo.

Walkinshaw, L. H. 1949. The Sandhill Cranes. Cranbrook Inst. Sci. Bull., 29. 1-202.

BIBAI AGRICULTURAL ENGINEERING COLLEGE, SENSHU UNIVERSITY, BIBAI, HOK-
KAIDO, JAPAN, 25 JANUARY 1971

AN EVALUATION OF WINTER BIRD POPULATION STUDIES

Richard Brewer

The only large body of data on population sizes of birds in winter is that
contained in the winter bird population studies published annually since
1948 in Audubon Field Notes (now American Birds). The method used in
these studies (Kolb, 1965) is that an observer traverses an area of known size
six or more times (hereafter termed “visits”) during the winter and records
all birds observed. After the last visit, the total number of individuals re-
corded is divided by the number of visits to give an average. This number
is then multiplied by the appropriate factor to express results in birds per
hundred acres. The same calculations may be made for individual species.

The method appears to have been developed more as a device to make
wintertime use of plots established for breeding bird censuses than for any
other reason; however, no discussion of the development of the method has
been published so far as I know. In the course of conducting such studies it
became clear that interpretation of the results was uncertain. This same con-
clusion has been reached by other workers and, in fact, the difficulty of analy-
sis and comparison has been a persistent theme in the comments by the editor
of the winter bird population studies (Kolb, 1961, 1962).

This paper reports results from a model devised to assess the meaning of
the figures resulting from the use of the Audubon Field Notes (hereafter
“AFN”) method of studying winter bird populations. I take as a starting
point the view that the most desirable datum is density, that is, the number
of birds per unit area. For any given area, density changes more or less
continually as birds enter the area or leave it. If we visualize a tract of 20
acres on which 10 birds occur but all of which have some portion of their home
range lying outside the boundaries of the tract, it is clear that the instantane-
ous density of the tract can vary between 0, when all of the birds are in those
portions of their home ranges off the tract, and 10 when all by chance happen
to be on the tract. These figures have some interest but a more valuable
figure is some appropriate average of the instantaneous densities. If the aver-
age fraction of the home range of the 10 birds included on the study tract
was 0.6, then the average density would be 6 birds per 20 acres (assuming
’ that a bird spends equal time in all areas of its home range ) . An accurate
estimate of density would be provided by the AFN method if each bird were
recorded on the fraction of visits corresponding to the fraction of its home
; range included on the tract.

Scientific names of birds mentioned in later sections are Ruffed Grouse,
1 Bonasa umbellus; Red-bellied Woodpecker, Centiirus carolinus: Hairy Wood-

261

262

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

pecker, Dendrocopos villosus; Downy Woodpecker, D. pubescens; Blue Jay,
Cyanocitta cristata; Black-capped Chickadee, Parus atricapillus ; Tufted
Titmouse, P. bicolor; White-breasted Nuthatch, Sitta carolinensis; Brown
Creeper, Certhia jamiliaris.

THE MODEL

The basic method used was this: a board was constructed on which were
drawn to scale a census tract of 23 acres and the home ranges of eight birds
with varying fractions of their home ranges included on the tract. The whole
board was the equivalent of about 275 acres and was covered by a grid with
coordinates the equivalent of 100 feet apart. The census tract was divided
into a grid by lines 200 feet apart (corresponding to every other 100-foot
coordinate in the section of the board occupied by the census tract) . A simu-
lated observer moved systematically over the tract following the 200-foot co-
ordinates at the same time that a simulated bird (represented by a transparent
plastic disk of known diameter) moved within its home range. If the plastic
disk touched or overlapped a point occupied by an observer, the bird was
considered to be observed and was counted.

Although some simplifications were necessary, the model was made as
realistic as possible. Because a primary aim was the eventual assessment of
studies conducted from 1966 to 1970 on five study tracts in oak and oak-pine
forests of Allegan County, Michigan, the features of the model were based
as far as possible on the biological features of the bird community of those
areas. On these areas, which varied in size from 9.6 to 18.4 acres, about 20
species of birds were observed on more than 150 visits between November
and March. Only 7 species were seen on all live tracts. Populations were
low, AEN estimates being in the range from about 5 to 8 birds per study tract
or about 30 to 55 birds per hundred acres. Black-capped Chickadee was the
most common species with an AEN estimate of about 20 birds per hundred
acres. White-breasted Nuthatch, Blue Jay, and Tufted Titmouse were the
next most common species.

Specific features of the model were as follows:

1. Home range sizes varied from 9 to 76 acres, with six between 22 and
38 acres (Table 1). These are reasonable sizes for home ranges of forest
birds based on our unpublished determinations and the literature (see, for
example. Butts, 1931; Fitch, 1958; Kilham, 1969; Robins and Raim, 1971).
The percentages of the simulated home ranges lying on the tract varied from
4 to 100 per cent.

2. The initial position of the observer at the beginning of a trial, or simu-
lated visit, was at the southeast corner of the tract. His movement was then
systematically across the tract. Systematic movement along coordinates was

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 263

Table 1

Results of the Model Evaluating AFN Winter Bird Study Methods.
Trials := 25 except as indicated.

Home

range

Percentage
on tract

Size
( acres )

Occurrence

(Percentage of trials recorded)

36' radius

75' radius

250' radius

Normal speed

J

4

34

0

7

12

A

14

37

4

22*

48

C

30

76

20

56*

92

G

45

38

32

56*

88

D

65

22

24

63*

96

E

65

35

36

64

84

H

100

8.6

24

89*

100

B

100

23

24

68

100

Half-normal speed

J

4

34

8

A

14

37

32

C

30

76

48

G

45

38

44

H

100

8.6

64

Twice-normal speed

J

4

34

12

21**

C

30

76

76

93**

G

45

38

88

100**

D

65

22

64

100**

E

65

35

88

100

H

100

8.6

60***

92

100**

* 27 trials
**14 trials
***20 trials

the method employed in the field by us and by many participants in the AFN
studies, but it is not a requirement of tbe method (Kolb, 1965).

3. The initial position of the bird was determined by the use of randomly
chosen numbers indicating a coordinate position on the board. The direction
of the bird’s first movement was determined randomly from among the eight
primary compass directions. After the first movement, the three opposing
directions were eliminated for subsequent movements. For example, if the
first movement was east, then west, northwest, and southwest were eliminated.
The possible actions for the bird on its second movement were six of equal
probability: north, northeast, east, southeast, south, and no movement. 3'ests
in the development of the model showed that if all eight directions were re-

264

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

tained the simulated bird tended to stay in a restricted area near its initial
position rather than to move over its home range in a manner corresponding
more closely to the actual movements of birds in the field.

Eventually movement of the simulated bird might bring it to the edge of
its home range. At this point all directions were again made available and
the no-movement possibility was eliminated. Certain movements, those which
would take the bird outside its home range, were impossible in this situation
and were rejected; other movements would move the bird along the edge of
its home range. The first move which took it away from the edge into its
home range was used as a new direction and the procedure of discarding the
three opposing points of the compass was again followed (and the no-move-
ment possibility re-instated).

The paths taken by the simulated birds under these procedures seemed
realistic when compared with our maps of actual paths taken by birds in
the field.

4. Three different speeds of movement of the bird relative to the speed of
the observer were used. These were approximately one-half the speed of the
observer (termed “normal speed”), one-fourth the speed of the observer
(half-normal speed), and the same as the speed of the observer (twice-normal
speed ) . In our censusing of oak forests, the actual speed of the observer
(median values) varied by area from about 56 to 69 feet per minute (fpm),
or about 0. 6-0.8 miles per hour (mph). In subsequent sections 67 fpm is
used as the speed of the observer. Although slightly faster than our actual
overall average, it is convenient as a rate taking exactly 3 minutes from one
stake to the next.

The actual movements on the board were as follows: Eor half and full
speeds the observer went from one grid intersection to the next (200 feet)
in two moves of 100 feet (that is, from one board coordinate to the next).
The bird took one move (normal speed) or two moves (twice-normal speed)
for each move of the observer. The moves of the bird were one-half square.
Going north, south, east, or west, one move of the bird was 50 feet; going
one of the four intermediate directions it was about 71 feet. Eor half-normal
speed the observer went from one grid intersection to the next (200 feet) in
a single move and at the same time the bird took one move.

At any time the possibilities for movement for the bird were 3 50-foot
moves, 2 71-foot moves, and no movement. Consequently, the average dis-
tance per move was about 49 feet. Twice-normal speed for the bird, accord-
ingly, was about 65 fpm, normal speed 33 fpm, and half-normal speed 16 fpm.

There is relatively little information in the literature on the rate of travel
of birds. Yapp (1956 ) commented that he had timed feeding winter tit flocks
at speeds from one-eighth to two mph (that is, about 10-175 fpm). Odum

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 265

Table 2

Rate of Movement of Three Species of Oak Forest Birds, Allegan County, Mich-
igan, February-March, 1969.

Species

Number of
observations

Total

minutes

Feet per minute

Range

Median

Downy Woodpecker

7

140

12-71

23

White-breasted Nuthatch

14

229

9-122

30

Black-capped Chickadee

9

149

15-64

42

(1942) reported rates of movement of Black-capped Chickadees, based on
all-day observation of flocks, from 18 to 40 fpm. He observed that speeds
varied by time of day and by weather conditions and commented that move-
ment was not uniform, periods of rapid movement (up to 350 fpm) alter-
nating with periods of little or no movement.

Our own observations made on one of our study areas at Allegan (the
Small Oak area) in February and March 1969 generally agree with these
findings. The observations were made (in connection with studies designed
to determine home range boundaries) by following birds for as long as pos-
sible and mapping the observations. Measurement of distance was along the
actual path followed and speed was calculated using the time elapsed from
the first to the last observation of the bird. Obtaining data on speed that are
unbiased is difficult. For example, the speed of birds which travel by moving
slowly through the forest and then taking a long flight to another area beyond
the range of observation will be generally underestimated because the long
flights will be omitted from the sample. Also it is important that short obser-
vations as well as lengthy ones be included, inasmuch as observations of
greater duration may be of birds traveling slowly enough that they can be
readily followed. I used a lower limit of four minutes for the practical reason
that estimates of speed based on shorter durations might be too inaccurate
owing to our recording times only to the nearest minute.

The data seem to indicate that birds may travel at speeds from less than
10 to more than 100 fpm and that variability is appreciable (Table 2l. They
indicate also that for the time and place they were gathered speeds of three
i important species of the forest are in the range between 20 and about 40 fpm.

5. Differences in conspicuousness were taken into account by using plastic
disks of three radii corresponding to 36, 75, and 250 feet. The circle of 36-
: foot radius represents a very inconspicuous species, the circle of 250-foot
radius, a very conspicuous one. If the disk touched or overlapped the jioint
occupied by the observer or his path in moving from one point to the next.

266

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

the bird was counted. This corresponds to a situation in which a bird is
totally observable up to a given distance from an observer and is never cen-
susable beyond that distance (curve 1 in Fig. 2 of Eberhardt, 1968) , an
obviously unrealistic situation. It also corresponds, however, to a situation
in which the radii represent median distance of observability (defined as
probability of observation). For example, the 75-foot circle represents a
situation in which the number of birds nearer than 75 feet that are missed is
the same as the number of more distant birds that are observed.

The relationship in the field between observability and distance from the
observer is difficult to approach directly. We may visualize the observer in
the center of a space that can be subdivided by circles drawn at equal dis-
tances going outward from him. The area of the concentric rings so produced
increases outward. For example, if 50-foot intervals are used, the ring from
50-100 feet away is larger than the circle from 0-50 feet and the ring from
100-150 feet is larger still. Assuming a homogeneous distribution of birds
in the space, the number of birds present in each ring will, accordingly, in-
crease going outward. The increase in area of the concentric rings is linear
and so, consequently, is the increase in number of birds present at given dis-
tances from the observer. Discussions germane to these ideas but developed
in connection with strip censuses are given by Anderson and Pospahala (1970)
and Emlen (1971).

If there were no decrease with distance in the ability of an observer to
detect birds, the number of birds seen at increasing distances would increase,
following curve A in Fig. 1. In fact, we expect observability to decline with
distance. Curve B represents a linear decline in observability from 100 per
cent at the point occupied by the observer. In this case, the number of birds
actually observed would be related to distance from the observer as shown
in curve C.

A linear decline in observability with distance is not an unreasonable as-
sumption but other reasonable relationships can be envisaged. I approached
the question indirectly in the following manner. During routine visits to the
oak forest study areas in the winter of 1968-9, the observer recorded the
distance from each stake on each plot at which any bird could be observed
by sight or sound. Estimating distances in the field is not easy but was
facilitated by the observers’ familiarity with the study areas, by the areas
being staked at 200-foot ( in some cases, 100-foot ) intervals, and by the use
of maps showing any prominent topographic and vegetational features. Data
deemed sufficient for analysis were obtained for the White-breasted Nuthatch
(Table 3) on one study area, the Black-capped Chickadee on three study
areas, and the Ruffed Grouse on one study area (Table 4).

Grouping of observations by distance (observations falling at a class

Richard EVALUATION OF WINTER POPULATION STUDIES 267

Brewer ‘

Fig. 1. Relationship between the number of birds present, their probability of being
observed (observability), and the number of birds aetually observed in ten concentric
zones centered on the observer. A linear decline of observability from 100 per cent at
distance 0 to 0 per cent at 500 feet is assumed.

boundary, as for example at 100 feet in Table 3, were counted as one-half
observation in each class) and plotting the result gives curves corresponding
to C in Figure 1. Making the assumption that observation is 100 per cent
efficient in the closest zone, the actual number of birds present in each zone
can be calculated as in Table 3 (cf. Anderson and Pospahala, 1970: 142-145,

Table 3

Relationship of Number of White-breasted Nuthatches Observed and Probability
OF Observation to Distance from Observer (Large Oak Area, Allegan Co., Mich-
igan, Winter 1968-9).

Number of birds estimated as actually present in each zone is calculated by deter-
I mining density for zone 1 (0.00077 per square foot in this case) and multiplying this
value by the area of the other zones.

Zone

( Distances
in feet)

Area of zone
( square feet )

No. of
observations

No. birds
calculated
as present

Probabibty

of

observation

1 (0-100)

31416

6

6

100

2 (100-200)

94248

5.5

18

31

3 (200-300)

157080

5

30

17

4 (300-400)

219912

2.5

42

6

5 (400-500)

282744

1

54

2

6 (500-600)

345576

0

66

0

7 (600-700)

408408

1

78

1

268

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Table 4

Relationship of Number of Black-capped Chickadees and Ruffed Grouse Observed
AND Probability of Observation to Distance, Allegan Co,, Michigan, Winter 1968-9.

Zone

( distances
in feet)

Black-capped Chickadee

Ruffed

grouse

Large

Oak

Small

Oak

Large Pine

Small

Pine

No.

Obs.

Prob.

No.

Obs.

Prob.

No.

Obs.

Prob.

No.

Obs.

Prob.

1 (0-40)

2

100

5

100

6.5

100

4

100

2 (40-80)

5

83

7

47

11.5

60

6

50

3 (80-120)

1

10

5

20

2.5

8

1.5

8

4 (120-160)

1

7

2

6

1.5

3

0.5

2

5 (160-200)

0

0

—

—

—

—

—

—

6 (200-240)

1

4

—

—

—

—

—

—

and Emlen, 1971: 329-333). If these figures were plotted they would corre-
spond to curve A of Fig. 1. Dividing the number of birds observed by the
number calculated to be present gives a curve relating probability of obser-
vation of distance (Table 3), corresponding to curve B of Figure 1. The
assumption of 100 per cent efficiency in zone 1 is probably erroneous (see,
for example, Enemar, 1959: 78-89, and Emlen, 1971), but this will not
affect the shape of the probability curve derived. The shape would be affected
if the distribution of birds were not homogeneous around the observer; bias
might be serious if the presence of the observer affected the distribution by
attracting birds or driving them away. My impression is that for winter
studies in oak forest this was not a serious problem in that any such move-
ments tended to be within zone 1 rather than between zones.

The results suggest that probability of observation declines rapidly at first
and then more slowly (Tables 3 and 4) . It is clear that a straight-line rela-
tionship does not hold over the whole distance from zero to the limits of
observation. A negative exponential relationship like that suggested by Gates
et al. (1968) for the flushing of Ruffed Grouse is a possibility, but it is also
possible that the relationship is a reversed sigmoid curve like curve in Fig.
2 of Eberhardt (1968), with a short upper limb hidden within zone 1.

I return now to the suggestion that the radius used for the plastic disk
simulating a bird should represent the median distance of observability. This
distance, at which the number of near birds missed is equal to tbe number
of far birds seen, shifts depending upon the observability curve. Calculation
of the median distance of observability appears to require a knowledge of
this curve, information which, as I have indicated, is not readily obtained.
One can, however, fairly readily obtain actual distances of observation in

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 269

Table 5

Data for Comparison of Median Distance of Observation and Median Distance
OF Observability, Using an Arbitrary Density of 0.0026 Birds Per Square Foot and
AN Arbitrary Reverse Sigmoid Relationship Between Probability of Observation
AND Distance from Observer.

Distance
from
observer
( feet )

Number
of birds
present

Probability

of

observation

Number
of birds
seen

Cumulative numbers

Birds

seen

Near

birds

missed

Far

birds

seen

0-50

2

0.99

2

2

0

27

50-100

6

0.95

6

8

0

25

100-150

10

0.75

7.5

15.5

2.5

19

150-200

14

0.30

4

19.5

12.5

11.5

200-250

18

0.15

3

22.5

27.5

7.5

250-300

22

0.07

1.5

24

48.0

4.5

300-350

26.5

0.05

1

25

73.5

3

350-400

31

0.03

1

26

103.5

2

400-450

35

0.02

1

27

137.5

1

450-500

39

0.01

0

27

176.5

0

Feet From Observer

' Fig. 2. Comparison of median distance of observation and median distance of observa-
bility for data in Table 5. Median distance of observation is tbe distance below wbicb
and above wbicb half of tbe birds were observed. A total of 27 birds was observed; con-
sequently, the median is the distance at wbicb tbe 14tb bird was seen, or about 140 feet.

I Median distance of observability is tbe distance at wbicb tbe number of near birds missed
is equal to the number of far birds observed, or about 181 feet.

270

THE WILSON BULLETIN

Septeinher 1972
Vol. 84, No. 3

some manner such as that described on page 266; from such data one can
calculate a median distance of observation. The median distance of observa-
tion is the distance below which and above which half of the actual observa-
tions lie. I have investigated the relationship between the median distance of
observation and the median distance of observability using models based on
various observability curves. Table 5 and Fig. 2 illustrate the method for an
arbitrary reverse sigmoid relationship between observability and distance.
Graphical solution (Fig. 2) indicates that the median distance of observation
is about 140 feet and tbe median distance of observability is about 181 feet.
All of the observability curves which I have tested, including most of the
biologically reasonable ones, yielded a similar relationship of the median
distance of observation lying within the median distance of observability;
the quantitative relationship between them, however, varied considerably de-
pending on the exact nature of the observability curve. For birds in oak
forests the median distance of observation lies between 40 and 200 feet and
several are clustered between 50 and 100 feet (Table 6; see also the appro-
priate species in Table 9 of Kendeigh, 1944. The latter figures apparently
are means rather than medians; because of the occasional bird observed at
a great distance, the mean will usually exceed the median for data of this
sort. ) Presumably these medians are all in some degree underestimations
of the median distance of observability. In sum, the oak forest data seem to
justify the radii of 36 feet as a very inconspicuous species, 250 feet as a very
conspicuous one, and 75 as a species of average conspicuousness.

6. As soon as a given simulated bird was tallied, the trial was discon-
tinued; this corresponds to a situation in which an observer can invariably
avoid counting the same bird more than once on a visit. This is undoubtedly
unrealistic, but I have no information on the frequency with which birds
are counted more than once, nor on how often birds are not counted in the
belief that they had already been recorded.

Fourteen to 27 (mostly 25) trials, or simulated visits, were used for each
home range under each set of radius/speed conditions. In all, 1000 simulated
visits were used (Table 1).

RESULTS

The relationship of basic importance is that between the percentage of
visits on which a bird is recorded (hereafter this percentage is called “occur-
rence”) and the percentage of the bird’s home range lying on the study tract.
For the AFN method to indicate accurately the contribution of a given indi-
vidual bird to the density of birds on the tract, the two values must agree.
This relationship is indicated by the diagonal line in Figs. 3 and 4.

For all conditions occurrence was positively related to the percentage of

Richard evaluation of winter population studies 271

Brewer ^

Fig. 3. Relationship between occurrence (percentage of simulated visits on which a
bird was counted) and percentage of the bird’s home range on the study tract (birds
moving at normal speed) for highly conspicuous birds (circle, 250-foot radius of obser-
vability), moderately conspicuous birds (squares, 75-foot radius), and inconspicuous
birds (dots, 36-foot radius). Lines were fitted by eye.

the home range on the tract. In no case, however, did the curve relating
occurrence to home range follow the required diagonal ( Figs. 3 and 4, Table
I I). Both conspicuousness of the bird and its speed relative to that of the
observer influenced occurrence. The closest approach to the diagonal and,
1 thus, the closest approach to an accurate reflection of density was given by
I the combination of a 75-foot median distance of observability and normal
' speed. All of the other combinations gave curves lying further from the

diagonal.

I

272

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 4. Relationship between occurrence (percentage of simulated visits on which a
bird was counted) and percentage of the bird’s home range on the study tract for birds
(moderate conspicuousness) moving at normal speed (squares), twice-normal speed
(circles), and half-normal speed (dots). Lines were fitted by eye.

For any conspicuousness: speed combination the basic curve relating oc-
currence to per cent home range on the tract showed a fairly sharp initial rise
and then tended to level off (Figs. 3 and 4, Table 1). The AFN method, ac-
cordingly, is relatively insensitive to changes in percentage of home range on
the tract from 30 or 40 to 100 per cent.

Occurrence increased with increased conspicuousness but the exact rela-
tionship was complex. The same increase, either actual or proportionate, in
median distance of observability was more effective in increasing occurrence
when the increase was in the range from 36 to 75 feet than when in the range

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 273

from 75 to 250 feet (Table 1). Also, the increase in occurrence was greater
for a given increase in median distance of observability for birds with large
percentages of their home range on the tract than for those with small
(Table 1).

Occurrence increased with increased speed of the bird relative to that of
the observer (Fig. 4, Table 1). Increasing to twice-normal the speed of birds
with a median distance of observability of 75 feet moved their curve far above
the diagonal into about the same position occupied by highly conspicuous
birds (250-foot radius) traveling at normal speed.

There was no consistent indication that size of home range had an effect
on occurrence (cf. home ranges D with E and H with B in Table 1).

DISCUSSION

It is clear that the AFN method fails in most situations to indicate accu-
rately the contribution of an individual bird to the avian population of a
study tract. To recapitulate, the relationship between occurrence and per-
centage of home range on the tract is non-linear, such that occurrence in-
creases only slightly for home ranges 100 per cent on the tract compared with
those 40 per cent on the tract. Occurrence is also affected by the conspicuous-
ness of the bird and the speed of the bird relative to that of the observer.

Other things being equal, the 75-foot radius of observability gave best re-
sults. I suspect that this is true because this value, among the three used,
most nearly approximates half the distance between census-plot coordinates.
With the 36-foot radius a bird may be within a square adjacent to the ob-
server and escape observation. With the 250-foot radius, a bird may be
beyond the adjoining coordinate and still be observed; consequently, if the
bird has any substantial part of its range on the tract, the probability of
tallying the bird at some time during the visit becomes very high, approaching
100 per cent once half or more of the home range is included on the tract
(Table 1, Fig. 3). It is a matter of some interest that, with the 75-foot radius,
even birds whose home ranges are wholly on the tract, whether contained
within it or coincident with it, were not invariably encountered on a visit
(Table 1). This was made possible by the movements of the bird producing
a path that avoided the observer.

Presumably a bird which remained stationary for the length of a visit and
which was of sufficient conspicuousness to be seen from one point on the
tract, if it were on the tract, would be recorded on tbe number of trials cor-
responding to its percentage of home range on the tract. Increasing the speed
of the bird increases its exposure to the observer, at least for home ranges
having a small j>ercentage of their area on the tract and, thus, results in these
birds being observed too often. Allowing birds with a very high percentage

274

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

of their home range on the tract to move, however, introduces the possibility
of their eluding the observer, as described above. It is unclear whether birds
moving at one-fourth the speed of the observer are censused much more
poorly than birds moving at one-half the speed of the observer (Table 1,
Fig. 4) ; it is, however, clear that birds moving at the same speed as the ob-
server are generally observed far too often.

The aim of the AFN method is to estimate abundance — ideally density — of
the total bird community and its constituent species. This is slightly different
from the question of how well the method assesses the contribution to density
of an individual bird and is worth examining directly. To begin with, very
conspicuous birds and birds having speeds equal to that of the observer will
almost invariably be overestimated. The Blue Jay is probably an example
of a species which will be overestimated. Very inconspicuous birds (the
Brown Creeper, perhaps) will invariably be underestimated, possibly ex-
cepting cases in which they are very fast moving.

Birds of medium conspicuousness and moving at speeds one-half to one-
fourth that of the observer will produce estimates that may be close to the
actual density on the tract. The occurrence curve for such birds cuts the
diagonal in such a way that birds having a small percentage of their home
range on the tract will be overestimated and birds having a large percentage
will be underestimated. If birds of both categories occur on the tract, the
errors will be in opposing directions. It would be too much to expect that
the errors would cancel one another but the tendency would be in this direc-
tion. Unfortunately, the extent and direction of the final error will be im-
possible to calculate.

Possibly some species of birds of the oak forests fit reasonably well the
conditions of conspicuousness and speed which allow fair estimates of density
(Tables 2 and 6). More information on conspicuousness and speed could be
used, however, before drawing such a conclusion. These topics are worth
some further research. Persons making AFN studies could contribute data
on conspicuousness and help to interpret their own figures by recording dis-
tances at which birds are observed. It is certain that variations in speed and
conspicuousness will affect estimates greatly; consequently, if a bird is fast
moving at one period of the year and slow at another, or if it is more con-
spicuous in one vegetation type than another, the figures derived in these
separate situations will not be comparable.

One important consideration in the winter study of populations not dealt
with directly in the model is the tendency of many species to occur in flocks.
If only mathematical considerations were involved, the effect would be sim-
ply to increase variability over the situation in which each bird moves inde-
pendently. This is undoubtedly one of the reasons for the visit-to-visit vari-

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 275

Table 6

Median Distance of Observation for Several Oak Forest Birds.
WERE Large Oak (LO), Small Oak (SO), Large Pine (LP),

AND Greenbrier (GB).

The Study Areas
Small Pine (SP),

No. of

Median dis-

Species (Study Area)

observations

tance ( feet )

Brown Creeper (LP)

3

40

Brown Creeper (SO)

3

90

Ruffed Grouse (SP)

12

50

Black-eapped Chickadee (LP)

22

60

Black-capped Chickadee (SO)

19

60

Black-capped Chickadee (LO)

10

50-75

Tufted Titmouse (GB)

5

70

Tufted Titmouse (LO)

9

100

White-breasted Nuthatch (GB)

7

70

White-breasted Nuthatch (LO)

21

200

Blue Jay (LO)

15

175

Red-bellied Woodpecker (LO)

9

200

ability in actual counts which, in my field experience, is substantial. In light
of this variability, the six visits minimally required by the AFN method may,
by chance, give very atypical results and will give a variance so large that
statistical demonstrations of any except enormous differences between years
or areas may be impossible. Other, biological, considerations may, however,
also be involved. Probably the presence of a bird in a flock increases its
likelihood of being seen. This is so because the flock tends to be more con-
spicuous than a single bird and once any member of a flock is detected, the
observer is likely to observe most or all of the other members. Individual
conspicuousness and flock conspicuousness may, then, be different things.
Values such as those given in Table 6 will, however, tend to reflect the con-
spicuousness of the usual unit (flocks for chickadees, individuals for creepers,
twosomes for nuthatches) so that we are led again to the conclusion that the
most important effect of conspecific flocking on AFN results will he to in-
crease variability.

' Because of the severe biasing effect of bird speeds that are high relative to

I the observer’s speed, I would recommend that in conducting AFN studies the
observer move at the most rapid pace compatible with his ability to detect
birds in his vicinity. Doubtless this pace will vary among habitats. It is per-

I haps worth emphasizing that this recommendation is designed to increase the
likelihood that AFN figures will approximate densities; if the aim is to in-

I elude as many as possible of the birds whose ranges touch the tract, an ex-

I

I

I

276

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

tremely slow pace would be best but the estimates derived will then be over-
estimates for all except the very inconspicuous species.

This discussion has emphasized the fact that AFN figures are full of
imponderables. It may be desirable to conclude with a point that, if not
optimistic, is at least moderately firm. In the special situation in which the
study tract is so isolated or circumscribed that all birds have their home
ranges entirely within it, all species except the most conspicuous ones will be
underestimated.

SUMMARY

A model was designed to evaluate estimates of bird numbers derived by methods em-
ployed in Audubon Field Notes winter bird population studies. Strictly accurate esti-
mates of density would result if the percentage of visits to a study tract on which a
bird was seen (called “occurrence”) was the same as the percentage of that bird’s home
range lying on the tract. This linear relationship was not found; instead occurrence
tended to level off at percentages above 40. Occurrence was also affected by the con-
spicuousness of the bird and by the speed of movement of the bird relative to that of
the observer.

It was concluded that in field situations fulfilling the conditions of the model very
conspicuous birds would be overestimated and very inconspicuous birds underestimated.
Estimates for species of medium conspicuousness might be fair approximations of actual
density, owing to the tendency of the method to underestimate the contribution to density
of birds with a high percentage of their home range on the tract and to overestimate
the contribution of birds with a low percentage. These conclusions hold for birds moving
slowly relative to the observer. Density of birds moving as fast as the observer will be
drastically overestimated, except for very inconspicuous species.

ACKNOWLEDGMENTS

For assistance in collecting some of the field data used in this paper, I am indebted
to James Faulkner, Michael M. Mills, Samuel Paskin, and especially Raymond J. Adams,
Jr. and Jerome D. Wenger. I profited from discussions on the censusing of birds from
the last two named as well as Arlo Raim. To Adams, Haven Kolb, and Murray M. Cooper
I am indebted for helpful comments on the manuscript. For assistance in the tedious job
of conducting the simulated visits, I thank particularly Rosemary Chrusciel and also
Lucy Sharp Brewer and Michael Campbell. A part of this work was supported by a
Western Michigan University Faculty Research Grant,

LITERATURE CITED

Anderson, D. R., and R. S. Pospahala. 1970. Correction of bias in belt transect
studies of immobile objects. J. Wildl. Mgmt., 34:141-146.

Butts, W. K, 1931. A study of the chickadee and White-breasted Nuthatch by means
of marked individuals. Parts II and III. Bird-Banding, 2:1-26, 59-76.

Eberhardt, L. L. 1968. A preliminary appraisal of line transects. J. Wildl. Mgmt.,
32:82-88.

Emlen, j. T. 1971. Population densities of birds derived from transect counts. Auk,
88:323-342.

Richard

Brewer

EVALUATION OF WINTER POPULATION STUDIES 277

Enemar, a. 1959. On the determination of the size and composition of a passerine
bird population during the breeding season. Var Fagelvarld, suppl. 2:1-114.

Fitch, H. S. 1958. Home ranges, territories, and seasonal movements of vertebrates
of the Natural History Reservation. Univ. Kansas Publ. Mus. Nat. Hist., 11:63-326.

Gates, C. E., W. H. Marshall, and D. P. Olson. 1968. Line transect method of esti-
mating grouse population densities. Biometrics, 24:135-145.

Kendeigh, S. C. 1944. Measurement of bird populations. Ecol. Monogr., 14:67-106.

Kilham, L. 1965. Differences in feeding behavior of male and female Hairy Wood-
peckers. Wilson Bull., 77:134-145.

Kolb, H., Jr. 1961. Winter bird-population study. Audubon Field Notes, 15:358-359.

Kolb, H., Jr. 1962. Winter bird-population study. Audubon Field Notes, 16:367.

Kolb, H., Jr. 1965. The Audubon winter bird-population study. Audubon Field Notes,
19:432-434.

Odum, E. P. 1942. Annual cycle of the Black-capped Chickadee — 3. Auk, 59:499-531.

Robins, J. D., and A. Raim. “1970” (1971). Late winter movements and social be-
havior of the Black-capped Chickadee. Jack-Pine Warbler, 48:66-72.

Yapp, W. B. 1956. The theory of line transects. Bird Study, 3:93-104.

DEPARTMENT OF BIOLOGY, WESTERN MICHIGAN UNIVERSITY, KALAMAZOO, MICH-
IGAN 49001. 26 JANUARY 1972.

PUBLICATION NOTES AND NOTICES

Observations on Duck Hunting in Eastern Canada in 1968 and 1969. By H. Boyd.
Occasional Paper No. 12, Canadian Wildlife Service, 1971 : 6% X 9 in., paper covered,
24 pp. No price given.

(From the author’s abstract) “Observations of hunter performance provide information
on specific differences in crippling losses and on factors governing the choice by hunters
of what ducks they shot at, how effectively they shot at different times during the season
and in various kinds of weather and what proportions of the ducks brought down were
retrieved and kept.” — G.A.H.

I

I

ACTIVITY PATTERNS OF CANADA GEESE
DURING WINTER

Dennis G. Raveling, Wendell E. Crews, and W. D. Klimstra

IT is common knowledge that activity patterns of wild geese are correlated
with weather conditions. Geese usually fly to feeding areas in the early
morning and late afternoons but undertake increased flight activity throughout
the day when it is stormy. In conjunction with a study of social behavior
and local movements of Canada Geese {Branta canadensis) during winter
(Raveling, 1969a-c; 1970) exact times of flight activities of a large wintering
flock were recorded almost daily for two seasons. Specific records of times
of flights were also available from radio-marked geese of known age, sex, and
social class (i.e., family, pair, single). This paper documents the activity
rhythms of a large winter flock of Canada Geese and of some specific indi-
viduals within that flock, and the environmental features associated with goose
activity. Such knowledge is necessary for understanding the ecological rela-
tionships associated with an animal’s activity and can usually be utilized in
management of exploited species.

METHODS

Observation of the times of flight and activities of the flock were made almost daily
from late September to mid-March in 1963-64 and 1964-65 at Crab Orchard National
Wildlife Refuge, Williamson County, Illinois. Approximately 40,000 Canada Geese {B.
c. interior; see Hanson and Smith, 1950:77) spent the major portion of the winter period
on and near this refuge. The inviolate portion of the refuge used by the geese included
2,600 acres of Crab Orchard Lake where the birds roosted, and 5,000 acres of cropland
(corn and soybeans) and 2,800 acres of pasture where the geese fed.

The geese roosted mainly at the lake (Raveling, 19696). Observers were usually in
the same locations each day and in position to note accurately the time at which the first
geese flew (either out from or back to the lake) and when flights were “heavy.” The
notation of heavy flight was relative to total numbers of geese in the area. This could
be as few as 10,000 in October or March and as many as 60,000 in January. The start
and ending of a period of heavy flight represented judgments of the time periods in
which many flocks were leaving or arriving from different areas at the same time. In
general, the period of heavy flight included movement of an estimated 75+ per cent of
the geese present.

During the two winters, 77 Canada Geese were color-marked and outfitted with miniature
radio transmitters. These included parts or all members of 10 families, 2 pairs, and 35
yearlings. Data recorded regularly from transmitter-marked geese included: lake loca-
tions before flight in the morning and afternoons, times of flight out from and back to
the lake and changes in feeding areas, and locations in fields. Flight times of radio-
marked geese were easily determined by continuous scanning of the frequency range
receiving their signals. The instant these birds flew, large increases in auditory signal

278

Raveling, Crews,
and Klimstra

WINTER ACTIVITY OF GEESE

279

0500
0530
0600 —
0630
0700
0730
0800 —I
0830
0900

[] COMPLETE OVERCAST SKIES

FIRST
^GOOSE
TO FLY

DURATION
OF HEAVY
FLIGHT

Fig. 1. Generalized average morning flight pattern of Canada Geese from the roost
lake under clear and complete overcast skies (civil twilight and sunrise from U. S.
Naval Observatory, 1961, 1962, 1963).

1

I strength occurred which then faded suddenly or disappeared at the termination of a
flight. Details on the techniques of radio-tracking and color-marking, and recognition
and permanency of families of geese and other social classes are provided in Raveling
(l%9a).

Temperature and humidity were recorded on a hygrothermograph at the refuge. Notes
were kept on cloud cover, wind direction, precipitation, and disturbances affecting the
movements and locations of geese. Cloud cover was recorded as none, partly ( < 50 per
cent), mostly (> 50 per cent), or complete.

MORNING FLIGHTS FROM THE LAKE

I Initiation. — At the latitude of Crab Orchard, civil twilight occurs within

26 to 29 minutes before sunrise and after sunset and the increase and decrease
of light intensity during these minutes is approximately eighty-fold (Kimball.
1916). With the exception of the coldest days in winter, morning goose activ-
ity began within this period of rapidly increasing light (Fig. 1 I.

In October and November under clear or partly cloudy skies, the first geese
to fly did so within 10 minutes after dawn civil twilight; from December into
March, when temperatures were above 20° F, the first flying geese were re-

280

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

(C.T.).

corded somewhat later, usually within 20 minutes after civil twilight (Fig.
2). Completely cloudy conditions usually delayed the time of first flight hy
approximately 10-15 minutes. Flight times were less predictable under cloudy
conditions. The delay of the first geese to fly during the darker, cloudy morn-
ings was more pronounced during periods when the first geese had been
leaving near the time of civil twilight rather than a few minutes later.

The time lag between the first geese to fly and the start of the heavy flight
was relatively constant regardless of variations in time of first flight and the
cloud cover (Fig. 3). Concentrated flights usually began between 10-30
minutes after the geese flew. When a dense fog occurred the heavy flight was
delayed up to 1.5 hours after the time the first geese flew. In general, the

281

Raveling, Crews,
and Klimstra

WINTER ACTIVITY OF GEESE

Fig. 3. Time lag between first geese to fly and the start of the heavy flight in the
mornings.

factors causing later initial flight also caused a corresponding time lag in the
flock as a whole. This suggests that the activities of the birds themselves were
also of importance in synchronization of flight times of the majority of the
flock.

Temperature. — The most striking factor influencing both the time and the
j magnitude of morning flights was temperature (Table 1). When temperatures
were below 15° F at sunrise there usually was no heavy flight. On the coldest
' days only a few or often no geese would fly out to feed. When temjieratures
I were between 16° and 20° F there occasionally was no heavy flight, hut more
i often a partial flight or a normal flight occurred. Above 20° F there almost
' always was a heavy flight of geese in the morning.

I

282

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Table 1

Effects of Temperature on the Magnitude of the Morning Flight of Canada Geese
IN Southern Illinois in the Winters of 1963-64 and 1964-65.

Sunrise
temperature
(° F)

Number of days
within each
temperature
range

Number of days
in which no
heavy morning
flight occurred

Number of days
in which morning
flight was
intermediate*

Number of days
in which morning
flight was
normal**

-5 to 5

12

12 (100%)

0

0

6 to 10

10

9 (90%)

1 (10%)

0

11 to 15

13

11 (85%)

1 (7.7%)

1 (7.7%)

16 to 20

23

5 (22%)

8 (35%)

10 (43%)

21 to 25

33

0

1 (3%)

32 (97%)

26 to 30

34

1 (3%)

1 (3%)

32 (94%)

* Many geese flew but many did not (40-60% flew or remained).
** Great majority of geese flew (>90%).

Temperatures between 16° and 20° F represent a relatively narrow threshold
at which these Canada geese did or did not fly in large numbers. Below 15° F
the geese spent a great amount of time apparently sleeping with the bill placed
under the scapular feathers and the feet and tarsi drawn into the flank feathers.
Activity was minimal and the tendency to flee from predators or other dis-
turbances was markedly reduced.

This notable response to environmental temperatures was rather precise
but is variable within the species as correlated with body size (Table 2).

Table 2

Relationship Between Environmental Temperatures at which Three Subspecies of
Canada Geese become Inactive and the Predicted Lowest Long-term Temperature
AT which the immature Female of Each Race could survive for extended Periods.

Subspecies

Temperature
at which
inactivity
begins (° F)

Source

Predicted
lowest long-
term existence
temperature ( ° F )

Source

maxima

o

to

o

o

o

Personal observa-
tions

+5°

Birkebak et al.
(1966a)

interior

15°

This paper

14°

This paper (follow-
ing methodology of
Birkebak, et al.,
19666)

parvipes

ca. 30°

L. A. Mehrhoff,
Jr.

(personal com-
munication)

32°

Birkebak et al.
(l%6a)

Raveling, Crews,
and Klimstra

WINTER ACTIVITY OF GEESE

283

NO. 82 SINGLE
ADULT MALE

20-1

10

0-

20-

10'

0

20-

w 10-

<

Q

u- 0-
o

o

2 20-

10 H
0

20

10-

0-

89 7.

NO. 171 FAMILY
OF 5

NO. 169 FAMILY
90 7o OF 4

f C ^

roJl Im

85 7.

NO. 178 SINGLE
YEARLING MALE

7 9 7o

NO. 15 SIBLING PAIR
YEARLING MALES

lo IoIq
ro cvi r

I v CJ ^ lO JO

o Q 6 6 o 6

CNJ ^ m (C

—AFTER

BEFORE

TIME (MIN.) IN RELATION TO START OF HEAVY FLIGHT

Fig. 4. Times of morning flights away from the roost lake of radio-marked Canada Geese
in relation to times of initiation of heavy flight of the entire flock.

Maxima is the largest race of Canada goose (Hanson, 1965:13-41) while
parvipes ( hutchinsii-parvipes complex of Macinnes, 1966) is one of the
smallest and interior is intermediate between the two (Hanson, 1951).

1 1 Flight Pattern oj Radio-marked Geese. — The fact that the flock as a whole
1 1 exhibited marked regularity in relation to civil twilight and sunrise in the
times of first flights and initiation of heavy flights suggested that individual
ll birds and families might initiate flight in a pattern of constancy with respect
I to light and the flight pattern of the entire flock. Comparison of flight times
1 1 of transmitter-geese with the patterns for the entire flock revealed that for
‘I certain periods (up to six consecutive days) some marked geese were pre-

I

284

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

dictable within 5 minutes as to when they would fly in relation to the initiation
of heavy flight. At other times the same birds were unpredictable and variable
in the times at which they flew. When radio-tracked over a period of weeks,
it was demonstrated that any individual or family might fly at almost any
time within the period of heavy flight of the flock as a whole (Fig. 4) .

Duration.- — During October and November the heavy flight usually lasted
from 20-40 minutes (Fig. 5). The duration of heavy morning flight in De-
cember and January was longer and more variable than at other times. This
may be a reflection of greater numbers of geese at the refuge and also colder
average temperatures which may delay or prolong activity. Heavy flights
in February and March usually lasted from 15-40 minutes. Cloud cover had
little, if any, effect in prolonging the morning flight once it was started even
though it may have initially delayed it. The last geese to depart from the lake

Raveling, Crews,
and Klinistra

WINTER ACTIVITY OF GEESE

285

Table 3

Length of Time (minutes) that Radio- and color-marked Canada Geese Remained in
Feeding Fields in the Mornings under Different Cloud Conditions and at Different
Periods of the Winter (1963-64 and 1964-65).

Sky Conditions

Time of year

Clear or partly cloudy

Mostly cloudy

Complete overcast

15-31 October

134 ± 8*

154 ± 11

192**

II

(N = 14)

(N= 4)

1-15 November

147 ± 6

152 ± 10

231 ± 14

CO

II

(N= 9)

(N = 15)

16-30 November

138 ± 17

164 ± 12

203 ± 7

(N = 14)

(N = 14)

(N = 18)

1-31 December

165**

142 ± 7

210 ± 20

(N= 5)

(N = 10)

(N = 10)

1-30 January

121 ± 11

169 ± 17

254 ± 16

(N = 16)

(N = 17)

(N = 33)

* Mean ± standard error.

** Variation about mean not calculated because of insufficient sample size.

in the morning usually did so from 10 to 30 minutes after the heavy flight
had ended.

MORNING FEEDING PERIOD AND MIDDAY ACTIVITY

When clear weather prevailed during October and November and almost
all the geese were feeding on the refuge near the lake, the flight pattern back
to the lake after feeding was almost as regular as the early morning departure.
The sight and sound of flying geese appeared to stimulate nearby geese on
the ground to fly also and this resulted in regular mass return flights to the
roost lake. The geese spent an average of just over 2 hours in the fields (Table
3). On completely cloudy days geese remained in fields over twice as long
as on clear days after their initial flight from the roost lake and then scattered
segments of the flock moved back and forth from the lake all day.

As the season progressed and available food at Crab Orchard Refuge was
exhausted (i.e., late December), the geese flew out farther (up to 10 miles
and occasionally more) and split into more widely separated suhf locks (see
Raveling, 19696). These subflocks usually returned to Crab Orchard at dif-
ferent times, especially if they were separated in their feed-field locations far
enough apart not to hear or see other subflocks returning to the lake. When
this pattern prevailed, it was impossible to record beginnings and endings of
a heavy flight that represented meaningful averages for the entire flock.

286

THE WILSON BULLETIN

September 1972 j
Vol. 84, No. 3

Table 4

Length of Time (minutes) that Radio- and color-marked Canada Geese remained
IN Feeding Fields in the Afternoon under Different Cloud Conditions and at Dif-
ferent Periods of the Winter (1963-64 and 1964-65).

Sky Conditions

Time of Year

Clear or partly cloudy

Mostly cloudy

Complete overcast

15-31 October

55 ± 5*

80**

(N = 19)

II

5

(N = 3)

1-15 November

77 ± 5

65 ± 6

—

(N = 32)

(N = ll)

16-30 November

74± 12

—

—

(N = 15)

1-31 December

64**

102**

92**

(N= 6)

(N= 3)

(N = 3)

1-15 January

70 ± 5

—

111**

(N = 30)

2

II

00

16-30 January

65 ± 7

81**

63**

(N = 20)

II

5

(Nr=4)

* Mean ± standard error.

** Variation about mean not calculated because of insufficient sample size.

Data on the length of morning feeding periods of the radio-marked indi-
viduals demonstrate that, under equal cloud conditions, geese did not remain
out for a longer time during the colder mid-winter or when they had to fly
farther to feed (Table 3).

AFTERNOON FLIGHTS AND FEEDING PERIODS

Afternoon flight times of the geese from the roost lake to feeding areas were
more variable than in the morning, especially on cloudy days. Even on clear
days, small groups of geese left the lake from 1 to 3 hours before the time
when the heavy flight occurred as the light level was fading. The correlation
of goose activity to light intensity was less prominent in the afternoon than
in the morning and this seems to be true for many birds (Armstrong, 1954) ;
but, there remained a predictable flight time for the majority of geese during
clear weather. As in the morning, the amount of time spent in feeding areas
in the afternoon under clear skies was relatively constant throughout the win-
ter and averaged about 1 hour (Table 4).

The evening flight from feeding areas to the roost lake varied widely (Fig.
6) . This variation was due largely to completely cloudy conditions. Data
on the start of the heavy flight on cloudy afternoons were often missing

Raveling, Crews,
and Klirnstra

WINTER ACTIVITY OF GEESE

287

/ i Fig. 6. Time period in which the heavy flight to the roost lake started in the afternoons
, in relation to sunset.

n

1 ' because the geese arrived over a longer time and often no definite peak flight
1 was observed. During clear weather the heavy flight usually began between
; sunset and civil twilight; times later than this usually represented evenings
r when a full or nearly full moon was visible at sunset. When cloudy, the

s ; evening flight to the lake almost always occurred before sunset.

Once flight back to the lake was initiated, it quickly became heavy and
lasted for 15 to 40 minutes when skies were clear ( Fig. 7) . As with the morn-
ing flight out (Fig. 5), duration of the evening flight hack was 5 to 10 minutes
3 longer in December — January than earlier or later in the winter. This proh-
, 1 ably represents the effects of greater numbers of geese.

I

i

i

288

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 7, Duration of the heavy evening flight.

The last geese to return to the lake usually did so within 5 to 20 minutes
after the heavy flight ceased. The last returning geese were often from 10 to
30 minutes or occasionally more after civil twilight. Evening feeding periods
were shorter and goose activity was more intense than during morning feeding
periods. The majority of geese stopped feeding and flew back to the lake in
in the evening at light levels lower than prevailed when they flew out in the
morning (compare relation of flight to civil twilight, Eigures 1 and 8). The
earlier evening flights during cloudy weather and the often later flights when
a moon was showing again demonstrated the rather critical responsiveness
of geese to prevailing light (Fig. 8).

Since temperature always increased above 15° or 20° F in midday, even

Raveling, Crews,
and Kliinstra

WINTER ACTIVITY OF GEESE

289

1500

1530

1600

1630

1700

I 730

1800 —

1830

1900 — '

m

I CLEAR SKIES
[] COMPLETE OVERCAST

-START OF HEAVY FLIGHT TO LAKE

-LAST GEESE TO LAKE

TAST GEESE WHEN FULL OR
NEARLY FULL MOON VISIBLE

Fig. 8. Generalized average flight pattern of Canada Geese to roost lake under clear
and complete overcast skies (sunset and civil twilight from U. S. Naval Observatory,
1%1, 1%2, 1963).

on the coldest days, temperature never caused a cessation of flight in the after-
noon as occurred in the morning.

As in the morning, some records of afternoon flight times of radio-marked
geese indicated short-term regularity of time of flight with respect to the initia-
tion of the heavy flight during clear weather. Most records, however, revealed
that the time of flight of an individual or family was not predictable within
the 30 to 40 minute time span in which the majority of geese flew back to the
lake.

NOCTURNAL ACTIVITY

Little time was spent by the investigators at Crab Orchard during the night.

I However, personnel residing at the refuge informed us when, on rare occa-
! sions, night flights and feeding activity occurred (excluding migration) . When
night activity occurred, effects were noticeable during the day because some
> i geese stayed out far beyond their regular time of return to the lake in the
:i i evening or were encountered in fields prior to dawn civil twilight. Extensive
, activity at night was encountered only during one jieriod in this study. 3 his
], I occurred when snow covered over 75 jier cent of the ground and at the time

I

290

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

of a full and nearly full moon from 13 to 19 February 1965. The reflection
of moonlight off the snow caused brighter than usual conditions and the
majority of geese remained out after 19:00 and continued feeding. The usual
daily patterns of flight and activity were noticeably changed.

In contrast to the rarity of night activity at Crab Orchard, it was relatively
common at Horseshoe Lake and Union County Refuges, also in southern
Illinois (refuge personnel, pers. comm.). Such activity seemed to be related
to heavy hunting pressure. Again, geese demonstrated their plasticity and
ability to change normal regular patterns when extreme conditions prevailed.
Markgren (1963:369) noted that Bean Geese (Anser fabalis) were normally
diurnal but could change to almost complete night activity when affected by
disturbance.

DISCUSSION

Initiation of Morning Flight. — Measurements of light levels were not per-
formed in this study but can be estimated from other data. Canada Geese
initiated morning flight in Saskatchewan when light intensity was 32 foot-
candles as measured with a light meter pointing east (or 11 foot-candles with
the meter pointing north) (A. Dzubin, Canadian Wildlife Service, in litt. ) .
These geese began flight 15 minutes before sunrise under clear skies, as did
the geese at Crab Orchard (Fig. 2).

Schreiber (1967) presented data on the rate of change of light intensity
under clear and cloudy skies. From this it can be estimated that it takes 15
minutes longer to reach 25 foot-candles intensity (overhead reading) under
cloudy skies than under clear skies. This delay in reaching the approximate
threshold reacted to by the geese as recorded by Dzubin equals the delay of
flight initiation observed under cloudy skies in this study. Beyond this low
threshold value, the length of time required to reach higher light intensities
shows wider differences between cloudy and clear sky conditions (Schreiber,
1967). Thus, the first geese to fly did so at approximately the same light
intensity regardless if it was cloudy or clear, but the majority of geese flew
under darker sky conditions on cloudy mornings than on clear mornings.
Therefore, light acted as a trigger but not as a graded controlling factor.

Birds awaken in a rhythm even in constant light (Palmgren, 1949). Light
is correlated with and probably influences the beginning, length of, and end-
ing of many activities. Dawn and dusk represent the times at which external
physical factors influencing synchronization of social flocks is probably easiest
(Wynne-Edwards, 1962:326). Several studies have demonstrated the sensi-
tivity of waterfowl to dawn or dusk light changes (Bossenmaier and Marshall,
1958; Winner, 1959; Martin and Haugen, 1960; Hein and Haugen, 1966).

No generalizations can be made as to the tendency of a particular single or
family to be constant in initiation of morning flight as they tended only to

Raveling, Crews,
and Klimstra

WINTER ACTIVITY OF GEESE

291

be predictable within the 30 to 40 minute time span in which the majority of
the flock flew. Many factors can influence the time at which geese fly; near-
ness to other birds taking off, presence or absence of disturbing factors (e.g.,
predators), synchronization of a pair or members of a family (Raveling,
1969c), and many unknowns (e.g., hunger, sleep, time since awakening, etc.).
Apparently, all these factors contribute to variability in flight initiation of
individuals and families.

Temperature. — Birkebak et al. (1966a) calculated the magnitude of heat
loss for varying temperatures for maxima and parvipes utilizing a methodol-
ogy verified by Birkebak et al. (19666). LeFebvre and Raveling (1967)
related these heat loss calculations to winter distribution of each race. The
data in Table 2 demonstrate that Canada Geese become inactive at tempera-
tures almost identical to those predicted to be the minimum at which they
could survive for extended periods (i.e., up to 15-20 days) while utilizing
almost all their energy metabolism for maintenance at a moderate work level
of metabolism (see LeFebvre and Raveling, 1967). These relations suggest
that inactivity is the most adaptive response to severe cold and functions to
conserve energy and is an important factor determining northern limits of
distribution in winter. Markgren (1963:325) noted comparable inactivity of
Bean Geese during the coldest days of winter.

Feeding Periods and Midday Activity. — Cold per se seemed to have little
or no influence on the length of the feeding period but instead caused a ces-
sation of activity. Canada Geese at Crab Orchard were in good physical con-
dition as judged by body weights during the winter of 196T-65 (Raveling,
1968) . If the geese were requiring more food during mid-winter, it appears
that ample time was afforded by the normal 2 to 2Mj hour morning feeding
period and the one hour evening feeding period to obtain that extra food.
Geese did not spend a majority of their feeding period actually feeding;
much time was also spent in alertness, loafing, and sometimes in aggression.
Increased cloudy weather in mid-winter rather than cold temperatures led to
geese remaining away from the lake for longer periods of time and provided
further opportunity for spending more time feeding.

Geese that returned to the roost lake on cloudy days often flew out again
within 1 or 2 hours. Geese apparently avoided the large lake during completely
cloudy weather and sought water during bright clear periods. When a strong
wind created noticeable waves or small “whitecaps,” geese moved into nearby
sheltered bays or flew from the lake in large numbers, even during clear
weather. Cloudy weather was often associated with stormy conditions, rain,
and wind. It appears that selection or conditioning or both have j)roduced
a state of fear in geese associated with such weather.

When the main roost lake( s) is small and })onds or other small water areas

292

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

are available in feeding areas, then large numbers of geese regularly day-roost
in the fields on or near these small water areas. This situation prevailed at
Union County and Horseshoe Lake Refuges. Markgren (1963:372) observed
a comparable pattern in Bean Geese.

We suggest that fear of predators by geese is an important factor influencing
habitual utilization of water areas during non-feeding periods in calm, clear
weather. When on water, geese are almost completely safe from mammalian
predators. Geese spent the night on the water, but very often loafed on the
bank during the day. Even on land, Canada Geese did not readily flee from
mammalian predators, but rather they “mobbed” them by walking parallel
to the predator while honking continuously. The near presence of a Golden
Eagle (Aquila chrysaetos) or a Bald Eagle {Haliaeetus leucocephalus) , how-
ever, occasioned rapid and somewhat disorganized flight back to the roost i
lake or nearest water if the geese were in fields. If an eagle approached them
on water, however, the geese resorted to diving and rapid movements on the I
surface of the water, but they usually did not fly back over land. We suggest
that this resort to water and diving in the presence of an eagle is adaptive
and prevents successful attack by an eagle. Thus, fear of predators influences
the geese to be on or near water during non-feeding periods of the day, whereas
fear of rough water and stormy conditions influences the geese to remain on
land.

Another important factor influencing length of time spent in fields during
cloudy weather is that the goose’s “sense of time” seems to be impaired. This
was most noticeable and revealing on days when the sun finally appeared
through the cloud cover at a time after which the geese would normally have
gone back to the lake if the sun had been visible all morning. Within 5 to 15 |
minutes after such a “sunflash,” thousands of geese that had still been feeding or |
were loafing began a mass flight back to the lake. Their cessation of feeding and ■
other activities was almost immediate and they began the alertness and char-
acteristic Head-tossing (Raveling, 1969c) that precedes flight. It seems that
the azimuth position of the sun as well as increasing and decreasing light
intensity at dawn and dusk, is an important factor regulating the onset, dura-
tion, and cessation of daily activities of Canada geese.

Several species of birds have been demonstrated to possess a sun orientation
mechanism of time sense (see reviews by Kramer, 1961; Scbmidt-Koenig,
1965).

Management Implications. — Knowledge of the usual rhythm of daily ac-
tivities of geese under a variety of conditions has been and will be useful in
manipulating shooting hours during the hunting season. For example, in the
area containing the refuges in southern Illinois, goose hunting is not legal
after 15:00. Thus, during clear weather, the heavy flight of geese in the after-

Kaveliiifj, Crows,
and Klimstra

WINTER ACTIVITY OF GEESE

293

noon is allowed to leave the refuge and be relatively unharrassed during their
feeding period. Although many goose hunters in southern Illinois believe that
the geese “learn that it is safe” to come out at 1500 hours, comparison of the
length of the evening feeding period (Table 4) to the time at which geese
return in the evening (Fig. 6) shows that this is the usual pattern of a rela-
tively undisturbed flock. There were relatively light effects of hunting pres-
sure at Crab Orchard as compared to other refuges because of the size of the
refuge and its relation to numbers of geese. However, where hunting pressure
is extreme, geese may become conditioned to time periods when they are not
pursued.

' Various other manipulations of shooting hours have been tried at other
p locations, e.g., no shooting before 09:00 or after 14:00 (cf. Hunt, et al. 1962 ) .

Such manipulations can achieve many effects, e.g., increased or decreased kill
I and wider dispersion of the harvest. Each situation should be studied as an
I individual case.

I SUMMARY

!|

ij Based on daily observation of the activities of a large wintering flock of Canada Geese
!j and specific records of radio-marked families and individuals, the times and nature of
j flight patterns of these geese are described along with the environmental variables asso-
j dated with these patterns. Characteristics of flight patterns were: regularity of onset
I i| of morning and evening flights in relation to light intensity under similar weather con-

Iditions; regularity of onset of the heavy flight with respect to the first geese which flew
and the prevailing light levels, usually at or just after sunrise in the mornings and be-
I tween sunset and civil twilight in the evenings; variability of individuals and families
within the regularity exhibited by the flock as a whole; delay of flight under completely
cloudy conditions; longer periods of time spent in feeding areas when cloudy, but not
when cold provided it was not too cold to prevent flight; considerable delay in flight
I time or usually cessation of flight when below 15° F. The motivation and probable
! adaptive nature of goose responses to roosting on or near water during clear weather or
in fields during stormy weather and their cessation of activity in cold periods are discussed.

^ ACKNOWLEDGMENTS

This investigation was financed mainly by the National Science Foundation (GB-623).
Additional support was provided by the Cooperative Wildlife Research Laboratory, Soutb-

II ern Illinois University, Carbondale, Dr. W. D. Klimstra, Director. Many agencies and
persons aided this study and are acknowledged in detail elsewhere (Raveling, 1969o).
^ We are grateful for the help of Messrs. W. W. Cochran, L. A. Mehrhoff, R. G. Bersonius,
j ' Drs. H. C. Hanson and 1). W. Warner. A. Dzul)in j)rovided helpful criticism of the
manuscript.

LITERATURE CITED

Armstrong, E. A. 1954. The behaviour of l)irds in continuous daylight. Ibis, 96:l-,30.
' Birkebak, R. C., E. a. LeFebvre, and 1). G. Raveling. 1966u. Estimated heat loss
from Canada Geese for varying environmental t(‘mperatur(‘s. Minnesota Mus. Nat.
r Hist. Tech. Rept., No. 11.

294

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Birkebak, R. C., C. J. Cremers, and E. A. LeFebvre. 19666. Thermal modeling applied
to animal systems. J. Heat Transfer, 88:125-130.

Bossenmaier, E. F., and W. H. Marshall. 1958. Field-feeding by waterfowl in south-
eastern Manitoba. Wildl. Monogr., 1.

Hanson, H. C. 1951. A morphometrical study of the Canada Goose, Branta canadensis
interior Todd. Auk, 68:164-173.

Hanson, H. C. 1965. The giant Canada goose. South Illinois Univ. Press. Carbondale.

Hanson, H. C., and R. H. Smith. 1950. Canada Geese of the Mississippi Fly way:
with special reference to an Illinois flock. Illinois Nat. Hist. Surv. Bull., 25:67-210.

Hein, D., and A. 0. Haugen. 1966. Illumination and wood duck roosting flights. Wil-
son Bull., 78:301-308.

Hunt, R. A., J. G. Bell, and L. R. Jahn. 1962. Managed goose hunting at Horicon
Marsh. N. Amer. Wildl. and Nat. Res. Conf. Trans., 27:91-106.

Kimball, H. H. 1916. The duration and intensity of twilight. Monthly Weather Rev.,
44:614-620.

Kramer, G. 1961. Long-distance orientation. Chap. 22 In Marshall, A. J., Ed., Biology
and comparative physiology of birds. Vol. 2. Academic Press, N. Y. pp 341-371.

LeFebvre, E. A., and D. G. Raveling. 1967. Distribution of Canada Geese in winter
as related to heat loss at varying environmental temperatures. J. Wildl. Mgmt., 31:
538-545.

Martin, E. M., and A. 0. Haugen. 1960. Seasonal changes in wood duck roosting
flight habits. Wilson Bull., 72:238-243.

MacInnes, C. D. 1%6. Population behavior of eastern arctic Canada Geese. J. Wildl.
Mgmt., 30:536-553.

Markgren, G. 1%3. Studies on wild geese in southernmost Sweden. Part 1. Acta
Vertebratica, 2:299-418.

Palmgren, P. 1949. On the diurnal rhythm of activity and rest in birds. Ibis, 91:
561-576.

Raveling, D. G. 1968. Weights of Branta canadensis interior during winter. J. Wildl.
Mgmt., 32:412-414.

Raveling, D. G. 1969a. Social classes of Canada Geese in winter. J. Wildl. Mgmt.,
33:304-318.

Raveling, D. G. 19696. Roost sites and flight patterns of Canada Geese in winter. J.
Wildl. Mgmt., 33:319-330.

Raveling, D. G. 1969c. Preflight and flight behavior of Canada Geese. Auk, 86:671-
681.

Raveling, D. G. 1970. Dominance relationships and agonistic behavior of Canada Geese
in winter. Behaviour, 37:291-319.

Schmidt-Koenig, K. 1%5. Current problems in bird orientation. In Lehrman, D. S.,
R. A. Hinde, and Evelyn Shaw, Eds., Advances in the study of behavior. Academic
Press, N. Y., pp 217-278.

ScHREiBER, R. W. 1967. Roosting behavior of the Herring Gull in central Maine.
Wilson Bull., 79:421-431.

United States Naval Observatory. 1961. The nautical almanac for the year 1%3.
U. S. Govt. Print. Off. Washington.

United States Naval Observatory. 1962. The nautical almanac for the year 1964.
U. S. Govt. Print. Off. Washington.

United States Naval Observatory. 1963. The nautical almanac for the year 1965.
U. S. Govt. Print. Off. Washington.

Kaveliiig, Crews,
and Kliinstia

WINTER ACTIVITY OF GEESE

295

Winner, R. W. 1959. Field feeding periodicity in Black and Mallard Ducks. J. Wildl.
Mgmt., 23:197-202.

Wynne-Edwards, V. C. 1962. Animal dispersion in relation to social behavior. Hafner
Co., New York.

COOPERATIVE WILDLIFE RESEARCH LABORATORY, SOUTHERN ILLINOIS UNIVERSITY,
CARBONDALE, ILLINOIS (PRESENT ADDRESSES: (RAVELING) DEPT. OF ANIMAL
PHYSIOLOGY, UNIVERSITY OF CALIFORNIA, DAVIS, DAVIS, CALIFORNIA, 95616;

(crews) u. s. fish and wildlife service, black water national wild-
life REFUGE, CAMBRIDGE, MARYLAND 21613). 3 NOVEMBER 1971.

THE NEOTROPICAL NEST REGISTRY

A Nest Registry system has been formed to record in a systematic fashion information
on the breeding biology and nesting of neotropical birds. A detailed discussion of the
rationale for and the difficulties associated with such a registry appears in American
Birds for February, 1972 (vol 26, pp. 18-20). Contributions from Mexico, Central and
South America, and the West Indies, are needed, and nest reports for primarily neotropic
species elsewhere would also be valuable. Contributions need not be in the form of a
standard nest record card, although entries typed on 4 X 6 index cards, one card per
species, would be desirable. Information to be published by the contributor will, of
course, be respected. In lieu of submitting detailed nest records, a statement of for what
species and in what countries, nest information exists, would help keep the Registry
file complete. Part of the Registry file will consist of a library of reprints containing
papers on life history studies or on specific aspects of reproductive biology of neotropical
birds. Send requests for information, or contributions of nest data or reprints to Michael
Gochfeld, Department of Ornithology, American Museum of Natural History, New York,
New York 10024.

REPRODUCTIVE BEHAVIOR OF THE COMMON LOON

SVERRE SjOLANDER AND GrETA AgREN

There is comparatively little known about the behavior of the loon family,
Gaviidae. The Common Loon [Gavia immer) is the species most ex-
tensively treated in the literature, especially in the comprehensive report by
Olson and Marshall (1952), but nevertheless several important behavioral
features still remain unknown, especially those pertaining to courtship and
mating. As a part of a more extensive comparative study on the behavior of
the Gaviidae the Common Loon was studied during the summer 1970 on
Iceland, where it was possible to obtain most of this missing information.

MATERIAL AND METHODS

Between 27 May and 5 September, a total of 391 hours of observation were recorded
on five pairs of G. immer in four different lakes. The lakes were: Selvatn on the Skagi
peninsula, Holmavatn by the town Bldnduos, Midfjadarvatn near the town Hvammstangi
and Holtavorduvatn in the mountain pass south of Hrutarfjdrdur. All these pairs were
followed from the arrival in spring until September. A number of additional observations
were also made, on several localities spread over the whole of Iceland.

In pairs where copulation was observed and the sexes thus could be determined, the
male was seen to be distinctly larger, with a heavier head and neck, and it was therefore
possible to distinguish and identify these birds during later stages of reproduction.

Table 1 shows the distribution of the observations regarding different types of be-
havior. All the types of behavior described here have been filmed unless stated other-
wise in the description, and sounds were tape-recorded using an Uher 4400 recorder.
Most observations were made from the car, a Land-rover, using binoculars or from blinds,

RESULTS

Arrival. — Most authors on the subject, e.g. Bent (1919), Yeates (1950)
and others, agree that G. immer arrives paired in spring as soon as the ice
on their nesting lakes has thawed. Our observations are in accordance, since
the pairs in all lakes arrived in this way, as far as could be ascertained. In
one case (Selvatn) the two pairs arrived on 30 May, when the ice had
left the shores, and the first egg was laid only 5 days later, on 4 June, a
remarkably short time but well in accordance with data on other loons
(Sj blander, 1968; Lehtonen, 1970).

Territorial behavior. — The fact that all loons are extremely territorial has
been noted by most authors, as well as the fact that the Gommon Loon chooses
a large oligotrophic lake as a nesting place. The fact that the territory is large
(up to 25 ha) might be explained by its use as the main source of food, and
this also leads to the well known sparse occurrence of loon pairs.

296

Sjolancler
and Agren

LOON REPRODUCTIVE BEHAVIOR

297

Table 1

The Number of Observations of some Behaviors and/or the

VOLVED IN THESE ACTIVITIES. BeHAVIORS OBSERVED MORE THAN

AS 100+.

Number of Pairs In-
100 Times are Given

Behavior

Number of

Number of

observed

observations

pairs

Raised neck

100-f

5

Bill-dipping

100+

5

Splash-dive

100+

5

Circle dance

24

5

Rush

21

2

Upright

15

1

Courtship

33

2

Copulation

6

2

Nest search

3

Nest choice

2

Nestbuilding

2

Incubating

3

Relieving

8

2

Feeding the young

100+

4

Riding on parent

30

2

Resting ashore

9

2

Perhaps the best known territorial behavior is the crying of the loon, as
described by e.g. Olson and Marshall (1952 ). The yodeling cry was the type
most clearly used as a territorial marking in all the birds we studied. It
was heard only from owners of territories and occurred most frequently dur-
ing the first phase of reproduction. The “wail” was observed in the same
situations as the “yodel,” and seemed a low-intensity form of this cry. The
“tremolo call” was the cry used in all situations of agitation, i.e. disturbances
by man, overflying birds, other loons directly intruding etc. S])ectrograms of
I these calls are shown in Figure 1.

When intrusion by other loons and in some instances other species oc-
curred, several types of defense reactions were shown. Hill-dipping, as illus-
Itrated in Figure 2 (15, 21, 38, etc) is the most common reaction in all situa-
tions where the birds are agitated, and might be regarded as a tyj)ical example
of a displacement activity (and thus not necessarily a defense reaction). A

298

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

0 seconds 0.5 1

repeoted 3'6 times

2

2.5

TREMOLO

■2kHi

Fig. 1. Spectrographs of some calls, of the Common Loon.

raised neck position was another very common reaction, where the neck and
hreast are raised. At higher intensities and in aggressive situations the front
plumage is lifted as well. This position is illustrated in Figure 3 (0) and in
Figure 2 (26, 85, 131, etc). It is very often accompanied hy the tremolo
call. A circle dance^ as illustrated in Figure 2, where the birds slowly circle
around another with raised necks, bill-dipping and diving, is a common oc-
currence in all confrontations, especially when several birds meet. These
behaviors mostly precede the splash-dive, where the bird gives a strong kick
upwards when diving, as in Figure 4 (8). At more intense stages of terri-
torial defense the bird raises to an upright position, when the body is held
almost or quite vertical, with the wings folded, (Fig. 3-8), or spread (Fig.
3-54). The bird may even jump clear out of the water. This reaction is
often preceded or followed by long rushes with flapping wings over the water
( Fig. 3-121 ) . This is not a pursuit but is mostly performed by a single bird.

Real fighting was not observed, except in one case where one bird of a
pair with young attacked a floating paper bag, spearing with the bill and
hitting with the folded wing, i.e. corresponding to the behavior in the vicious
and occasionally deadly fights known in G. arctica ( Sjolander, 1968). All
these reactions, with the exception of the raised neck, have been reported '
earlier hy different authors, e.g. Munro (1945), Yeates (1950), Olson and
Marshall (1952) and others, though not always in connection with terri-
toriality.

Courtship. — Since the territorial behavior of loons is so spectacular and
the behavior most likely to be seen by the observer, it is easily understandable

Sjfilandcr
and Agren

LOON REPRODUCTIVE BEHAVIOR

299

0

42

112

165

Fig. 2. Circle dance, performed by a territorial pair and an intruder. Numbers as
in Fig. 3. Drawing directly from a film.

300

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 3. Behavior towards an intruder in the territory of a pair with young. Defender
to the right in 0, 8, 16, later indistinguishable from intruder. The numbers indicate frames
of film at 18 frames per second, from an arbitrarily chosen zero, the drawing being made
directly from a film.

that it has been interpreted as courtship by many authors (e.g. Huxley, 1923
for G. stellata) . A number of authors, e.g. Munro (1945), Olson and Mar-
shall (1952), Niethammer (1966), and others have described behavior re-
garded as courtship in G. immer, but all these descriptions seem to refer to
territorial behavior. Our observations indicate, however, that there is very
little courtship in G. immer, if by courtship is meant a special behavior pre-
ceding and leading to copulation. This is easily explained since the very
probable life-long pairing in all loons makes the need for an elaborate court-
ship small. The only specialized behavior regarded as courtship in the pairs

Sjolanilcr
and Agrcn

LOON REPRODUCTIVE BEHAVIOR

301

A

B

I

ii

54

I

46

c

Fig. 4. Courtship, three different examples performed l>y the same pair. Numl)ers
indicate frames at 18 frames per second, counted l)ackwards from a zero cliosen at the
splash dive. Drawing directly from a film.

302

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 5. Copulation. Frame numbers as in Fig. 3. Drawing directly from a film.

we studied was a formalized bill-dipping followed by a mutual splash-dive, as
illustrated in Figure 4. This behavior only occurred as an immediate pre-
liminary to copulation, or copulation attempts, and was easily distinguished
from threat to intruders.

Copulation. — The copulation, which is not always preceded by any court-
ship, is initiated by the female who begins to seek a suitable place to go
ashore anywhere in the territory. During this search-swimming both birds
have very short necks. The male follows her closely. When she finds a place
where she can climb up on land she goes up and awaits and male. He was in
all cases very reluctant to follow, and especially in the days preceding egg-
laying very often did not follow at all. If he decides to join the female he
climbs up behind or next to her and immediately attempts to copulate. The
copulation takes place as illustrated in Figure 5, i.e. corresponding to the
same behavior in other loons.

Immediately after the copulation the male leaves the shore, whereas the
female usually waits some minutes before following. The duration of the
copulation is short, as can be gathered from Figure 5 ( about 20 seconds from
contacting the female to leaving her ) . Five of six copulations observed, as
well as 22 out of 33 courtship displays, took place between 03:00 and 09:00.

LOON REPRODUCTIVE BEHAVIOR

303

Sjolamler
anil Agren

The behavior, including attempts, was seen daily from the day of arrival
I until 2-4 days before egg-laying. The maximum number of copulations on
I one day was two.

Thus, the copulation closely resembles tbe same behavior in other loons
, as described by Huxley (1923) for G. stellata and Sj blander (1968) for G.
arctica, as might well be expected. There seems to be no published descrip-
tion of this behavior, apart from a single observation by Tate (1969) and
ji a report by Southern ( 1961 ) . The latter report, however, describes a be-
havior where one bird chased another and then climbed on top of it, on the
water, and thus in all probability refers to a territorial fight. It may also
j be noted that we found no evidence of the existence of a copulation platform,
as mentioned by Tate (1969 ) and Tate and Tate (1970) . Such platforms seem
not to be used by the other loons either.

Nest choice. — In the two cases where it could be ascertained, the male
,i chose the nest site. During the last 2 days preceding egg-laying he began
to go ashore and make nest-building movements on different locations in the
territory, soon settling for one of them. At the same time, the female in both
I pairs was still inviting; and on several occasions the two birds could be seen
1 ashore on different places, the female inviting, the male building on the
! future nest. The female joined the male in nest-building on the day preceding
egg-laying. In the two cases where the nest-building could be followed, the
ultimate nest site was decided and the building of tbe real nest started on the
day of the egg-laying (which as far as can be ascertained took place during
the dark hours).

Nest building. — Both birds took part in the nest-building, but as soon as
the female had accepted the male’s choice she stayed on the nest and thus
did the greater part of the building. The movements used were the same as
in comparable birds, i.e. pulling material over tbe shoulder, drawing it near
the body, scratching with the feet and wagging the body. In both observed
cases the nest was built in less than 20 minutes, though added to sporadically
during the incubating period. In one case these later additions combined
with egg-turning moved the whole nest a distance of 1.4 m away from the
first site, apparently since the place first chosen was unsatisfactory (reached
by waves in strong winds ) .

Incubating. — Despite some reports to the contrary, several authors have
noted the fact that both parents take part in the brooding, e.g. Bent (1919).
In all the pairs we studied, the female took the greater part in the incubating.
The periods between changing varied between less than one hour and 16
hours, with changes becoming less frequent towards the end of incubation.
Especially in the beginning, there was a competition between the parents to
incubate, where the incubating bird refused to leave its place to tbe other

304

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

parent, although the latter had already climbed up to the nest. When being
relieved, the leaving bird in the majority of cases started building, i.e. pick-
ing up material and drawing it in ( or making the building movements without
material) and continued this behavior while leaving the nest for several
minutes (in one case 42 min), even out on the water. The relieving bird
usually turned the eggs before laying down, and then made some building
movements after settling on the eggs. Apart from the turning of the eggs at
relief, the eggs were seldom turned, and during most sessions not at all.

Hatching. — The exact incubation time could only be determined in one
case, and was 28 days. In this case, the single young ( the other egg was not
developed ) stayed on the nest 20 hours before leaving it. It was fed on the
nest during this time, and made two short excursions to the water.

Parental behavior. — Altogether six pairs with young were observed of
which only one had two young. The survival of only one young seems to be
a very common, even normal, condition in all loons, which may at least for
G. stellata be explained by competition between the young for the food
brought by the parents, and the aggressiveness between the young ( von Braun,
Hessle, and Sj blander, 1968). Two of the six pairs were studied more closely,
and the main bulk of observations refers to these pairs.

Most of our observations coincide well with the reports by Olson and Mar-
shall (1952 ), Dunlop ( 1915), Wilson (1929), and others. It might be pointed
out, however, that the defense of the young is very difficult to distinguish
from the normal territorial defense, and so a special defense of the young
might not exist. When the birds are disturbed, the young normally leave the
parents and hide near the shore, while the parents show the normal behavior
towards the intruder, as described by e.g. Dunlop (1915 ). The young and
parents were thus separated for rather long times (maximum observed 85
minutes ) .

A behavior not previously reported in this species, but well known from
G. stellata (von Braun, Hessle, and Sj blander, 1968), is that the birds go
ashore to warm the young, not necessarily on the nest but using any suitable
place. This was observed nine and two times respectively in two pairs, the
time spent ashore being from 11 min to 3 hours. The initiative to go ashore
came from the young in one case, but in the others from the parent.

A difference noted between the description of the feeding behavior given
by Olson and Marshall ( 1952 ) and our observations was that the former au-
thors state that the parent dips the food into the water and splashes it around
before it is handed over to the young, but in the several hundred instances
we observed of feeding this was not seen. The young often miss the food and
drop it, and the parents then pick it up again, which might create an impres-
sion of splashing. Both parents fed the young in all observed pairs, and the

Sjolaiuler
anil Agren

LOON REPRODUCTIVE BEHAVIOR

305

behavior described in Palmer (1962), i.e. one parent handing the food over
to the other prior to feeding, was never observed.

The young were fed at approximately one hour intervals the longest pause
at night being 6 hours. The number of feedings during each bout varied
from one to 63, the duration of the bouts from less than one minute to 50
minutes. In practically all cases it was impossible to ascertain the type of
food given, but in a few instances fishes were clearly recognized.

The young spent a considerable time riding on the back of either of the
parents, up to 50 per cent of the time during the first 3-4 days, a notable
difference from other loons, where riding seems less frequent (von Braun,
Hessle, and Sj blander, 1968; Sj blander, 1968; Lehtonen, 1970). They were
also warmed under the wing of either parent while floating. No riding was
observed after the young were 16 days old.

Behavior of young. — Our observations of the behavior of the young are
well in accordance with e.g. the report by Beebe (1909). The first dives were
observed at four days of age, but the diving ability is not well developed
until an age of about two weeks. Consequently, the young are an easy prey
for such predators as the Great Black-backed Gull {Larus tnarinus) , espe-
cially when the young leaves the parents during disturbances. The young
bird moves easily on land, and might well be able to cover great distances in
case of need, as reported for G. stellata (von Braun, Hessle, and Sj blander,
1968), a valuable ability if the nesting lakes freeze early.

Our observations give no clues as to the onset of independence, since all
young stayed with their parents during our observation period, and were also
fed (the oldest being 101 days old).

DISCUSSION

Even if a definite proof is yet lacking there are many reasons to believe
that loons pair for life. The facts that they arrive in pairs immediately as
the ice on the lakes thaws; that the number of pairs in a lake and even the
nest sites remain the same throughout the years, as well as the lack of lengthy
and spectacular courtship and the short time between arrival and egg-laying,
all point to this conclusion.

We know practically nothing of the formation of these pairs, but the sparse
occurrence of lone, calling birds in spring ( observed in G. arctica ) would
point to the speculation that young males look for territories and then call
for unpaired females, in which case the territorial cry could also be attributed
a sexual significance. On the other hand, a pair formation in the sj)ring flocks
on the coasts might also be possible. Obviously, different loon species might
differ in the method used, but this seems improbable in view of the many
similarities in the reproductive behavior.

306

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

The courtship remains a disputable question. Very few authors on the sub-
ject have ever seen copulation, which has been described by Zedlitz (1913),
Huxley (1923), and Keith (1937) for G. stellata, by Sjolander (1968) for
G. arctica. There are no reports for the remaining two species except the previ-
ously mentioned report by Southern (1961) (obviously referring to a fight)
and the observation by Tate (1969). In the descriptions of what has been
regarded as courtship, there is therefore seldom if ever a connection stated
between the reported behavior and copulation. A closer study of the terri-
torial behavior of the loons leaves little doubt that the behavior described by
different authors as courtship is really territorial, and only indirectly, if at
all, connected with the mating.

The opinion given in this report, that the courtship consists of the rela-
tively simple movements described above, gains further support from a com-
parision with G. arctica and G. stellata which show the same type of behavior
preceding copulation, although there are notable differences in their terri-
torial behavior (and thus in the behavior described as courtship in earlier
reports) .

Even if the pairs and copulations observed here are comparatively few,
the fact that the behavior is about the same as in G. stellata and G. arctica
strongly suggests that the observed cases were representative. Further, a copu-
lation on the water as reported by Southern (1961) seems highly improbable
since tbe loons lack a pseudopenis.

The significance of the building movements shown at relief by G. immer,
in the same way as in G. arctica and G. stellata, remains uncertain, since it
is the relieved parent that shows the most building, which makes a signalling
interpretation difficult. A possible explanation might be that activity near
the nest by the other parent stimulates an otherwise suppressed building, since
inactivity on the nest is important to make the bird less conspicious, and thus
a concentration of different activities from the conspicuous but necessary re-
lieving might be advantageous.

Our observations on the behavior of parents and young do not differ from
the reports by other authors except on some minor points. The warming of
the young on the shore is probably a normal behavior, since it is well known
especially in G. stellata, but since it does not seem to occur very often the
fact that earlier observers have not seen it in G. immer is easily explained.
This is also true for the differences noted in the feeding behavior, where the
earlier observations are rather scanty.

On the whole, the observations in this report point to a strong similarity
between G. immer and especially G. arctica, since the territorial behavior,
courtship, copulation, nesting behavior, incubation, and parental behavior are
very much the same. The explanation of such similarities and differences

Sjolaniler
and Agren

LOON REPRODUCTIVE BEHAVIOR

307

can, however, only be had in the context of a study of the behavior of the
whole family Gaviidae, which is as yet incomplete.

SUMMARY

During the summer 1970, the authors studied a number of pairs of the Common Loon
{Gavia immer) with respect to the reproductive behavior, on Iceland. The birds were
studied from spring arrival till September, and the territorial behavior, courtship, copu-
lation, nest choice, nest-building, incubation, and parental behavior was observed and
filmed. The territorial behavior was observed and filmed rather extensively, and a de-
scription of the different movements is given. Of the several vocalizations the yodel is
regarded as a territorial call, the wail as a low-intensity form of the yodel, the tremolo as
a warning and agitation call.

The courtship observed was very much like the behavior in G. arctica and G. stellata,
but differs from earlier reports of G. immer. This seems to stem from the description
of territorial behavior as courtship by many authors. The copulation, which took place
ashore, was similar to the copulation of G. arctica and G. stellata, as might be expected.

The nest site was chosen by the male, the main nest-building done by the female.
Additional nest-building was observed when the parents relieved each other on the nest.
The incubation period was 28 days. The parental behavior was as described in earlier
reports, but differences noted in the feeding behavior (both parents feeding, no splashing
or dipping of the food). The young were sometimes warmed ashore. A number of com-
parisons with G. arctica and G. stellata are made.

ACKNOWLEDGMENTS

The field work was made possible through grants from the Hierta-Retzius Stipendiefond
and the C. F. Liljevalchs resestipendier, as well as H. Ax:son Johnsons Stiftelse. Our
thanks are also due to the Icelandic Museum of Natural History and other authorities,
for permits to work as well as advice. Last but not least we wish to thank Margareta and
Richard Mdller for assistance, as well as our many friends on Iceland, especially Benedikt
Jonsson on Hafnir and Palmi Hraundal on As, on whose grounds we worked.

LITERATURE CITED

Beebe, C. W. 1907. Notes on the early life of loon chicks. Auk, 24:34-4-1.

Bent, A. C. 1919. Life histories of North American diving birds. U.S. Natl. Mus.
Bull., 107:47-62.

Braun, C. von, A. Hessle, and S. S.iolander. 1968. Smalommens [Gavia stellata)
heteende under ungvardnadstiden. Zool. Revy, 30:3-4, 94^95.

Dunlop, E. B. 1915. Notes on the Great Northern Diver. Brit. Birds, 9:142-147.
Huxley, J. S. 1923. Courtship activities in the Red-Throated Diver, together with a
discussion of the evolution of courtship in birds. J. Linnaean Soc. Zook, 35:253-292.
Keith, D. B. 1937. The Red-Throated Diver in North East Land. Brit. Birds, 31:66 81.
Leiitonen, L. 1970. Zur Biologic des Prachttauchers [Gavia a. arctica L.). Ann. Zool.
Fennici, 7:2S-60.

Munro, j. a. 1945. Observations of the loon in the Caribou I’arklands, British Colum-
bia. Auk, 62:42-46.

Niethammer, G. 1966. Handhuch der VJigel Mittel(*uropas. Frankfurt am Main. 1:

I 61-69.

!

308

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Olson, S. T., and W. M. Marshall. 1952. The Common Loon in Minnesota. Occ.
Papers Minnesota Mus. Nat. Hist., 5:1-77.

Palmer, R. S. 1962. Handbook of North American birds. Yale Univ. Press, New
Haven & London. 1:9-10.

Sjolander, S. 1968. lakttagelser over storlommens {Gavia arctica L.) etologi. Zook
Revy, 3:89-93.

Southern, W. E. 1961 Copulatory behavior of the Common Loon. Wilson Bulk, 73:
280.

Tate, J. D. 1969. Mating of the Common Loon. Proc. Nebraska Acad. Sci., 79:50.
Tate, 1). J., and J. Tate. 1970. Mating behavior in the Common Loon. Auk, 87:125-130.
Wilson, F. N. 1929. The loon at close range. Bird-Lore, 31:95-103.

Yeates, G. K. 1950. Field notes on the nesting habits of the Great Northern Diver.
Brit. Birds, 63:5-8.

Zedlitz, 0. VON. 1913. Fin Beitrag zur Biologic von Polartauchers, Urinator arcticiis.
J. Ornithok, 61:179-188.

UNIVERSITETET I STOCKHOLM, ZOOLOGISKA INSTITUTIONEN, BOX 6801, 113 86
STOCKHOLM, SWEDEN, 30 AUGUST 1971.

NEW PATRON

The latest addition to the list of Patrons
of the Wilson Society is Dr. Paul A.
Stewart of Oxford, North Carolina. Dr.
Stewart, who is a research entomologist

with the U.S. Department of Agriculture,
holds three degrees from The Ohio State
University. He has published about 100
papers on birds, 20 on insects, and 2 on
mammals. One of his major pieces of re-
search has been a thorough study of the
life history of the Wood Duck, and his
other interests in ornithology extend to
the ecology of blackbird congregations, the
evolution of bird migration, and the role
of birds in the control of undesirable in-
sects. He is a member of the AOU, the
BOU, the Cooper Society, Ecological
Society of America, Northeastern Bird-
Banding Association, Inland Bird-Banding:
Association, and American Society of'
Mammalogists. Dr. Stewart is married and
has two sons.

RESPONSES OF ADELIE PENGUINS TO COLORED EGGS

Leigh H. Fredrickson and Milton W. Weller

A DELIE Penguins {Pygoscelis papua) normally lay one or two greenish-
_ white eggs. Males, less commonly females, occupy old nest depressions
from which they display and attract former or new mates (Sladen, 1958).
Nest sites usually are occupied for several weeks before the laying of the first
egg and either sex may sit in the incubating position on the nest bowl. Both
sexes incubate, but males start intensive incubation first when females leave
to feed after laying (Penney, 1968). The incubation drive is very strong, and
nest defense can be intense.

As part of a study involving measurement of variations in incubation
behavior, and recording temperatures of incubating birds, by means of

thermistors placed in artificial eggs, we wanted to determine : 1 ) the ability

of penguins to recognize their own eggs, 2) the likelihood of ejection of
unlike eggs, and 3) possible measures of incubation intensity. Field studies
of incubation behavior of Adelie Penguins provide an insight into how a
species can maintain itself in this adverse environment.

PROCEDURES

Weller experimented with 13 pairs of Adelie Penguins at Hallett Station, Antarctica,
during early November in 1969, and Fredrickson studied 23 pairs between 31 October
and 20 November 1970. Birds studied during 1969 were of unknown age except for one
female which had been banded as a breeding adult in 1959. Four birds banded in 1969
returned to the colony and were retested in 1970. The sexes of all pairs were deter-
mined in 1970, but only seven of 13 pairs were sexed in 1969. Sexed birds were color-

marked with paint for rapid determination of the individual on the nest.

Plastic, hollow “Easter eggs"' were used because of their availability, bright colors,
and the fact that ballast (sugar and salt were used) could be placed inside to duplicate
the weight and balance of real eggs. Plastic eggs of two sizes were used: 45 X 63 mm
in 1969, and 57 X 83 mm in 1970. One size was smaller and the other larger than real
Adelie Penguin eggs f56 X 70 mm for 126 eggs at Hallett, J. V/einrich, unpuhl. data).

In this study, eggs were introduced into the nest howl. This method is inferior to the
choice of two nests method used for Herring Gulls (Larus argentatus) by Tinbergen
(1961:151), hut the minimal nest spacing and aggressive behavior of colonial Adelie
Penguins would not permit such experimentation.

PRE-LAYING STAGE

In 1969 Pair 1 in the pre-laying stage was exposed to white, 1)1 ue, and
yellow plastic eggs for 2 minutes each. Each egg presented was accepted and
incubated in the nest with the exception of the blue egg which was found out
of the nest. Normally, penguins do not retrieve even their own eggs (Penney,

309

310

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Table 1

Number of Colored Plastic and Blown Penguin Eggs Ejected from Adelie Penguin
Nests prior to Laying. Hallett Station, Antarctica, 1970.

Days prior
to laying

Number of eggs ejected

Colored plastic eggs

Blown

eggs

By male

By female

By pair

By male

By pair

1

2/9*

0/9

0/9

0/2

0/2

2

2/3

0/3

0/3

0/3

0/3

3

0/8

0/8

1/8

0/2

0/2

4

0/12

0/12

0/12

0/2

0/2

5

2/6

0/6

0/6

0/3

0/3

6

1/4

1/4

0/4

1/3

1/3

7

1/8

0/8

1/8

1/2

0/2

8

5/9

1/9

0/9

1/3

0/3

9

0/3

0/3

0/3

0/1

0/1

10

1/1

0/1

0/1

0/0

0/0

11

0/2

0/2

1/2

0/0

0/0

13

0/2

0/2

2/2

0/1

1/1

15

0/1

0/1

0/1

0/0

0/0

Totals

14/68

2/68

5/68

3/22

2/22

26/90

* In 9 trials, 2 eggs were ejected by a male.

1968) . A pink plastic egg then was left for 20 minutes, and this time sub-
sequently was used for tests of all birds in the pre-laying stage. Three other
pairs in the pre-laying stage were tested with eggs of these four colors and
all accepted each egg and incubated for 20 minutes each. Eggs were presented
in different sequences of color.

Then, two highly aggressive pairs were used, including one banded female
estimated to be in excess of 13 years of age. In both cases, the female was
standing over the egg but the male pecked at the egg viciously until it was
ejected from the nest. In both nests, all four test eggs were pecked until
ejected from the nest bowl at which time they were ignored. This striking
difference in behavior suggests that physiological state and perhaps experi-
ence may influence acceptance of any egg in the nest bowl. In another experi-
ment, a blown, weighted Adelie Penguin egg was viciously pecked by both
members of another pair but was finally accepted and incubated for several
days.

In 1970, birds were tested from 1 to 15 days before laying with blue,
pink, yellow, and natural colored, blown and weighted Adelie Penguin eggs.
Eggs were pecked until ejected from the nests in 26 of 90 tests (Table
1). Males accounted for 17 of the ejections compared to only two ejections

Fredrickson
and Weller

PENGUIN BEHAVIOR

311

Fig. 1. Summary of responses to colored plastic eggs placed in nest bowls of Adelie
Penguins prior to, during, and after laying. Hallett Station, Antarctica, 1970.

by females. In seven tests, both members of the pair actively ejected eggs.
At no time did females eject blown, weighted Adelie eggs from the nest bowl.
Females ejected colored plastic eggs at 6 and 8 days before laying, but one
male ejected colored eggs the day before eggs appeared in the nest. In five of
22 tests, when blown and weighted Adelie Penguin eggs were ejected from
nests, all rejections were 6 or more days before laying.

In six tests made from 15 to 7 days before laying the penguins either peered
at the experimental eggs or ignored them, but the eggs were not incubated
during the 20-minute test period. Four of these six tests were with colored
eggs and two were with blown Adelie Penguin eggs.

Four penguins marked in 1969 were tested 12 times in 1970 during the
pre-laying stage. These birds accounted for eight of 26 tests in which eggs
were ejected from the nest. Six of these eight rejections were with colored
plastic eggs. In three other tests from 15 to 6 days before laying, these birds
failed to incubate eggs.

As laying nears, Adelie Penguins become increasingly broody (Fig. 1).
Of nine tests 1 day before laying, all hut one bird incubated at least 18
minutes. The mean incubation of 13.5 minutes shown in Figure 1 for a 20-
minute test on the day before laying resulted from one particularly aggressive
male, which ejected colored eggs during two tests the day before laying.

312

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

LAYING — INCUBATION STAGE

To test the responses of birds known to be broody in the laying or post-
laying stage in 1969, three nests were selected with two, one, and one eggs,
respectively. Pair 7 had two eggs and accepted a white plastic egg in place
of one of its own eggs. Then a pink egg was presented to test both a smaller
and strikingly different colored egg. It accepted the egg without hesitation
and incubated for 10 hours, at which time the original egg was replaced.

The two pairs with one egg each were given a yellow or a blue egg in place
of their own egg. In each case the egg was accepted as though it were its
own, and incubation of the plastic egg continued for 10 hours at which time
the original egg was replaced.

Briefer experiments of a similar nature were conducted on four pairs
which had two, one, one, and two eggs, respectively. In nests of two eggs,
one of the two was replaced by a plastic egg; real eggs were removed from
nests of one egg. All of the birds readily accepted the pink, blue, and yellow
substitutes even when in the nest bowl with a real egg. The behavior of
several individuals suggested recognition of the colored eggs by their hesi-
tancy and peering but the relative roles of color, sheen, size, and other factors
in recognition cannot be clearly evaluated. However, in most cases responses
other than incubation were masked by the external and internal stimuli that
cause birds to incubate their eggs.

On 11 November 1969 Pairs 5 and 6, which had refused to accept plastic
eggs, were tested again when they had two eggs. Each was given the one
pink plastic egg for 20 minutes in place of one of its own. The male of
Pair 5 was alone and was less aggressive but more broody than previously.
This male examined the one pink and one normal egg for 3 minutes and then
incubated for the 20-minute test period.

Pair 6, however, did not change in their response to the foreign eggs. The
female accepted the egg by standing over it but the male pecked it out of the
nest; thereafter, its second egg was returned.

In 1970, all pairs accepted the colored eggs and incubated them during
laying and 6 days post-laying. Of 48 tests during laying and 42 tests post-
laying (Fig. 1), one pair incubated a yellow egg 19 minutes instead of the
20 minutes observed in the other 89 tests.

DISCUSSION

Antarctic weather dictates the need for intensive incubation behavior if
eggs of Antarctic species are to develop properly in sub-freezing temperatures.
Because Adelie Penguins have strong attachments to nest sites before egg

Fredrickson
and Weller

PENGUIN BEHAVIOR

313

laying, the species provides unique opportunities for study of the external
and internal factors related to development of incubation behavior.

There seems to be no evidence that penguins lack color vision, and the
fact that several species have colored bills and feathers suggests strongly that
they can differentiate colors. Moreover, Levick (1915 ) did experiments with
colored rocks which suggested that Adelie Penguins preferred red. The ability
of several individuals to quickly perceive and eliminate colored eggs from
the nest supports the idea that color vision is present, but characteristics of
these test eggs such as sheen, size, or the crack in the egg were not properly
evaluated in these tests. There is little doubt, however, that the plastic eggs
were recognizable as unlike their own when in the same nest bowl with a
real egg.

It is well known that birds are not very selective in egg color or size
(Tinbergen, 1961:144-159), but some birds which are parasitized regularly
readily reject eggs unlike their own (Swynnerton, 1918). Ducks are more
likely to reject unlike experimental eggs during laying than during incubation,
presumably because the brooding drive is less strong (Weller, 1959:352).

Although the nest bowl is clearly important as a pair center for Adelie
Penguins, they must become physiologically ready to accept an egg when it
appears in the nest. Apparently there is no innate recognition of color or
size of the egg. We infer from these brief experiments that Adelie Penguins,
as in many other birds, incubate objects of any color which appear in the
nest. The rejection behavior of several highly aggressive males in 1969 and
1970 may reflect lack of development of the incubation drive in males at
this stage and longer experience in nesting. The external and internal factors
that cause the change from aggressive to incubation behavior remain unknown.

ACKNOWLEDGMENTS

The work was financed by NSF Grants GA 13827 and GA 23744 of the United States
Antarctic Research Program to Dr. John R. Baker of Iowa State University. We are
indebted to Dr. Baker, to Dr. George Llano, Program Director for the Antarctic Biology
Program, and to Navy Task Force 43 for making this work possible.

LITERATURE CITED

Levick, G. 1915. Natural bistory of the Adelie Penguin. British Antarctic “Terra
Nova” Expedition, 1910-1913. British Mus. Nat. Hist., London. Natural History
Rept. Zook, 1:55-88.

Penney, R. 1968. Territorial and social behavior in the Adelie Penguin. In Austin.
0. L., Jr. (Ed.), Antarctic bird studies. Aimuiean Geophysical Union, Washington,
I). C. Antarctic Research Series, 12:8.3-131.

Sladen, W. J. L. 1958. The Pygoscelid penguins. Falkland Islands Dependencies
Survey Sci. Rept., 17:1-97.

I

i

1

314

THE WILSON BULLETIN

Sei)lcinher 1972
Vol. 84, No. 3

SwYNNERTON, C. F. M. 1918, Rejections of birds of egg unlike their own with remarks
on some of the cuckoo’s problems. Ibis, 6:127-154.

Tinbergen, N. 1961. The Herring Gull’s world. Basic Books, Inc., New York.
Weller, M. W. 1959. Parasitic egg laying in the Redhead (Aythya americana) and
other North American Anatidae. Ecol. Monogr., 29:333-365.

GAYLORD MEMORIAL LABORATORY, UNIVERSITY OF MISSOURI, PUXICO, MISSOURI
63960 AND DEPARTMENT OF ZOOLOGY AND ENTOMOLOGY, IOWA STATE UNI-
VERSITY, AMES, IOWA 50010, 13 SEPTEMBER 1971.

NEW LIFE MEMBER

A recent addition to the list of Life
Members of the Wilson Society is Dr.
James A. Pittman. Dr. Pittman earned his
bachelor’s degree at Davidson College, and
his M.D. at Harvard Medical School and is
currently Head of the Office of Research and
Education, Veteran’s Administration as well
as Professor of Medicine at Georgetown
University. He is the author of over 150
papers in the medical and physiological
literature, particularly thyroid physiology.
His interests in ornithology also involve
avian endocrine physiology. Dr. Pittman
says that his interest in birds, in biology,
and in The Wilson Society were aroused
and stimulated by George Sutton and
Franklin McCamey in Orlando, Florida in
the latter days of World War II. Dr. Pitt-
man is married (Mrs. Pittman is also a
Professor of Medicine) and has two
children.

VARIATION IN THE POSTERIOR BORDER OF THE
STERNUM IN SOME TREE-TRUNK FORAGING BIRDS

Alan Feduccia

The posterior border of the avian sternum varies considerably in various
taxa but no one to date has been able to offer a convincing correlation
between form and function of this complex character. Those correlations of
sternal anatomy with functions which have been attempted and which have
some credence are summarized by Heimerdinger and Ames (1967), but all
are tenuous at best. This paper examines the form and possible function of
the posterior border of the sternum in several unrelated groups of birds which
are comprised both of forms which forage by creeping up vertical surfaces,
and those which forage from the normal perching fashion.

THE STERNUM IN OVENBIRDS AND WOODHEWERS

Woodhewers (Dendrocolaptidae) (tree-trunk foragers) and ovenbirds
(Furnariidae) (“normal foragers”) are very closely related, and therefore
offer the opportunity to discover specific adaptations associated with the
tree-trunk foraging habit.

The variation in the notches of the posterior border of the sternum in oscine
and suboscine passerine birds has been reported by Heimerdinger and Ames
(1967). They examined almost a thousand specimens and divided the sternal
types into six categories (see Fig. 1), grading from those with no notches
(type 1), to those with four complete notches (type 6). Heimerdinger and
Ames (op. cit.) discovered the greatest amount of variability within the Den-
drocolaptidae, and found that of 173 specimens in nine genera, the majority
possessed two-notched (type 3) sterna; types 2, 3, and 4 were sometimes
found in the same species, but no specimens were described as possessing
type 5 or 6. Woodhewers possess rather solid sterna, with one specimen of
Xiphocolaptes promeropirhynchus having a sternum devoid of any perfora-
tions (type 1) .

Ovenbirds typically possess a two-notched (type 3) sternum, but some
specimens exhibit the more perforate types. Heimerdinger and Ames (op.
cit.) discovered type 5 sterna (with a lateral notch and a large medial fenestra
on each side) in five of 199 specimens examined, including certain specimens
of Xenops rutilans, Pygarrhichas albogularis, Sclerurus rujigularis, and S.
guatamalensis.

I have attempted to show general trends in the sternum by condensing data
from Heimerdinger and Ames (1967) in tabular form (Table 1 ). When the
data are presented in such a manner certain things become apparent. 33ie

315

316

THE WILSON BULLETIN

Sef)teniher 1972
Vol. 84, No. 3

E F

Fig. 1. Photographs of the sternal notch types: A, Xiphocolaptes promeropirhynchus:
Dendrocolaptidae (type 1 approaching type 2) ; B, Xiphorhynchus guttatus: Dendro-

colaptidae (type 2) ; C, Automolus ochrolaemus: Furnariidae (type 3) ; Cinclodes fuscus:
Furnariidae (type 4 approaching type 5) ; E, Sclerurus guatemalensis: Furnariidae (type
5); F, Dendrocopiis villosus: Picidae (type 6). Photographs made to approximately

same scale.

Alan

Feduccia

STERNA OF TREE-TRUNK FORAGERS

317

Table 1

Distribution of Sternal Notch Types Found Within Ovenrirds and Woodhewers.
(Data primarily from Heimerdinger and Ames, 1967).

The numbers under each sternal type represent the number of specimens examined
within each genus. The species within each genus may be found in Heimerdinger and
Ames (op. cit.).

Sternal Notch Types

1

2 2-3 3

3-4

4 4-5 5

Geositta

5

1

2

U pucerthia

7

1

Ochetorhynchus

2

1

Eremobius

1

Cinclodes

7

3

4 1

Furnarius

15

Sylviothorhynchus

1

Aphrastura

4

2

Phleocryptes

1

1

Leptasthenura

6

Schizoeaca

1

Schoeniophylax

2

Synallaxis

34

1

Certhiaxis

2

Cranioleuca

5

Asthenes

11

Phacellodomus

3

Coryphistera

3

Anumbius

2

Margarornis

7

1

Premnoplex

2

1

2

Pseudocolaptes

3

Pseudoseisura

4

2

Hyloctistes

2

Syndactyla

3

Anabacerthia

8

1

Philydor

4

Automolus

12

1

Hylocryptus

2

Xenops

7

1

Pygarrhichas

2 1

Sclerurus

3

Lochmias

1

318

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Table 1

Continued

Sternal Notch Types

1

2 2-3 3 3-4 4

4-5 5

Dendrocincla

8

1

Deconychura

3

Sittasornus

18

1

Glyphorhynchus

10

Xiphocolaptes

1 3

1

5

Dendrocolaptes

1

1

8

3

1

Xiphorhynchus

10

4

37

5

3

Lepidocolaptes

7

1

34

2

Campy lor hamphus

4

Dendrexetastes

1

ovenbirds and woodhewers possess a basic sternal type, which is type 3.
These type 3 sterna tend to be more open (to the left-hand side of table 1),
or more closed (to the right-hand side of table 1), than typical type 3 sterna.
When they are more open they become types 3-4, 4, 4-5, and 5, and when
they are more closed they become types 2-3, 2, and 1. The ovenbirds tend to
have type 3 sterna, but with a considerable degree of opening; whereas, the
woodhewers are the only forms which show closure. In fact, the only genera
which show closure are Xiphocolaptes. Dendrocolaptes, Xiphorhynchus, and
Lepidocolaptes. These data indicated to me the possibility that closure of
the posterior border of the sternum might be associated with the tree-trunk
foraging habit.

It is of interest here to note that the four woodhewer genera which are
somewhat intermediate between the Furnariidae and Dendrocolaptidae in
many anatomical characters, Dendrocincla, Sittasornus, Deconychura, and
Glyphorhynchus, show the sternal pattern of the ovenbirds with no tendency
towards closure of the posterior border. Dendrocincla forages in a variety of
postures (including creeping), while Sittasornus, Deconychura, and Glypho-
rhynchus creep up tree trunks like other woodhewers. I have shown elsewhere
(Feduccia, 1969) that the above genera possess many primitive characters
within the woodhewer assemblage, and it is possible that some may represent
separate ovenbird offshoots which have reached the dendrocolaptid “grade”
of anatomical organization. Dendrocincla even possesses the hemoglobin
characteristic of the family Furnariidae. Thus, if sternal ossification is oc-
curring with tree-trunk foraging, the lack of sternal closure in the above
genera would not be surprising.

Alan

Feduccia

STERNA OF TREE-TRUNK FORAGERS

319

It should also be noted here that there are several ovenbirds which may
at times forage like the woodhewers by hitching up tree trunks; however, all
of these forms, which include Margarornis, Premnornis, Premnoplex^ Cranio-
leuca, Pseudocolaptes, Xenops, Automolus, and Pygarrhichas, forage in a
variety of manners, and hitch up tree trunks only as alternatives to other pos-
sible foraging postures. Oscines which creep up tree trunks show the same
sternal pattern as non-creeping forms. As Heimerdinger and Ames (1967)
have pointed out, “Oscines which have a specialized form of locomotion
such as creeping on vertical surfaces {Certhia, Sitta), or which are partially
terrestrial {Eremophila, Cinclus) , have exactly the same sternal characters
as the more typical oscines. It is also true, however, that many of these spe-
cialized species are migratory; the importance of certain regular, but short-
time, activities during the life span may override a tendency toward adapta-
tion for the daily type of locomotion.”

THE STERNUM IN THE PICIFORMES

If it is expected that closure of sternal notches occurs with the evolution of
tree-trunk foraging behavior, then one should be able to find a similar con-
dition in other climbing birds.

In order to test the hypothesis that closure in the posterior border of the
sternum is a result of selection pressures for stronger sterna associated with
tree-trunk foraging, I turned to the diverse order Piciformes. Unlike the
ovenbirds and woodhewers which possess diverse sternal types, making com-
parisons very difficult, all of the piciform birds that I examined possessed
type 6 sterna (four notches). Within the order Piciformes are found both
trunk-foragers and perching types. If trunk foraging is associated with sternal
closure then it should be obvious in piciform birds. In order to compare
various piciform birds with respect to sternal closure I have taken the ratio
i of depth of median notch of the sternum to the total sternal length. The
\ means and ranges from these data are shown in Figure 2. Small sample size
for most species prohibits elaborate statistical testing, but certain trends are
obvious within the diagram. The most important point is that the tree-trunk
foraging piciform birds (nos. 24-60) show, in general, more sternal closure
than the non-trunk foraging piciforms (nos. 1-23). However, when one views
the diagram in segments one finds many interesting points. The Galbulidae
(nos. 1-3) seem to form a cohesive group as do the Bucconidae (nos. 4—7).
However, the Capitonidae (nos. 8-12) are tremendously variable. Why
Capita niger (no. 8) should show great closure of the sternal border is an
enigma. The species of the Indicatoridae (nos. 13-14) seem to be very homog-
eneous. The Ramphastidae (nos. 15-20) are of great interest, for although
j they form a cohesive group, they clearly show more sternal notch closure

320

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

than the other perching piciform birds. The Jynginae (no. 21), and the
Picumninae (nos. 22-23), as expected from the hypothesis, have relatively
open sterna as compared to other members of the Picidae. The large wood-
peckers, Dryocopus pileatus and D. lirieatus (nos. 38-39), and Phloeoceastes
guatemalensis and P. rubicollis ( nos. 59-60 ) , are towards the bottom of the
woodpeckers with respect to sternal closure, but the medium-sized wood-
peckers, Piculus simplex and P. flavigula (nos. 29-30), and Meiglyptes tukki
(no. 37), show equally closed sterna.

If the trend towards closure of the posterior sternal border were truly invari-
able, then one might expect to see some trend in closure corresponding to the
relative amount of time that the forms spend on tree trunks. Thus, the series
might go from Colaptes to Asyndesmus to Melanerpes (see Burt, 1930; and
Spring, 1965). However, no such trend appears to be evident. Therefore, I
feel that the tendency towards closure (as was the case for the woodhewers)
should be stated as a general trend, not as a strict anatomical law. As in the
case of the woodhewers, there is a general trend towards closure of the poste-

->

Fig. 2. Means and ranges for the ratio of depth of medial notch of sternum to total
length of sternum for the following piciform birds: Family Galbulidae: no. 1, Galbula
ruficauda (4 specimens), no. 2, G. galbula (2), no. 3, G. dea (2) ; Family Bucconidae:
no. 4, Malacoptila panamensis (3), no. 5, Notharchus macrorhynchos (5), no. 6, Monasa
atra 12), no. 7, Chelidoptera lenebrosa (3) ; Family Capitonidae: no. 8, Capita niger
(2), no. 9, Semnornis rhamphastinus (3), no. 10, Tricholaema lachrymosum (2), no. 11,
T. diadematum (2), no. 12, Trachyphonus darnaudi (3) ; Family Indicatoridae no. 13,
Indicator variegatus (2), no. 14, /. indicator (3); Family Ramphastidae: no. 15,

Pteroglossus torquatus (5), no. 16, P. castanotis (8), no. 17, P. aracari (3), no. 18,
Ramphastos swainsonii (5), no. 19, R. toco (5), no. 20, R. sulfuratus (6); Family
Picidae: Subfamily Jynginae: no. 21, Jynx torquata (3) ; Subfamily Picumninae: no.
22, Picumnus temminckii (2), no. 23, P. minutissimus (4) ; Subfamily Picinae: no. 24,
Colaptes cafer (6), no. 25, C. auratus (11), no. 26, C. campestris (4), no. 27, C.
melanochloros 13), no. 28, C. punctigula (2), no. 29, Piculus simplex 13), no. 30, P.
flavigula 12), no. 31, Campethera nubica (3), no. 32, C. abingoni 12), no. 33, Celeus
elegans (2), no. 34, C. undatus (2), no. 35, C. jlavus 12), no. 36, Picus viridis (2), no.
37, Meiglyptes tukki 12), no. 38, Dryocopus pileatus (7), no. 39, D. lineatus (5), no. 40,
Asyndesmus lewis 12), no. 41, Melanerpes erythrocephalus (8), no. 42, M. formicivorus
15), no. 43, M. carolinus 15), no. 44, M. uropygialis 16), no. 45, M. aurifrons (9), no.
46, M. chrysogenys (3), no. 47, M. pucherani (4), no. 48, Leuconerpes Candidas (3), no.
49, Sphyrapicus varius (11), no. 50, V eniliornis fumigatus 13), no. 51, V. spilogaster (3),
no. 52, Dendrocopus major (3), no. 53, D. villosus 118), no. 54, D. pubescens HI), no.
55, D. borealis (6), no. 56, D. scalaris (6), no. 57, Picoides tridactylus (5), no. 58, P.
arcticus (5), no. 59, Phloeoceastes guatemalensis 13), no. 60, P. rubicollis (3). All of
the above piciform birds possess type 6 sterna with the exception of Celeus elegans,
which has the median notches open, but with one large perforation laterally on each side
of the sternum, Celeus undatus and C. jlavus both possess normal type 6 sterna.

Alan

Fecluccia

STERNA OF TREE-TRUNK FORAGERS

321

DEPTH MEDIAL NOTCH / STERNAL LENGTH

GALBULIDAE

BUCCONI DAE

CAPITON IDAE
INDICATORIDAE

RHAMPHASTIDAE!:;

JYNG INAE

PICUMNINAE
—

PICINAE

O,

322

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

rior border of the sternum, but closure may only occur where it does not
interfere with other sternal functions which may he necessary at sometime
during the life history of the organism, but which are under opposing selec-
tion forces.

Short’s (1971) paper on the evolution of terrestrial woodpeckers points
to the fact that though there are as many as twelve species of terrestrial or
semi-terrestrial woodpeckers, they tend to spend part of their life histories
on tree trunks or vertical surfaces. These forms might therefore be under se-
lection forces for maintaining adaptations associated with tree-trunk foraging.
Even the most terrestrial form, the Andean Flicker (Colaptes rupicola) , roosts
commonly in excavated holes in vertical surfaces (Short, op. cit.. Fig. 11).
As Short (op. cit., p. 15) also points out, “Arboreal woodpeckers . . . may
vary greatly in the use of their legs during climbing, and structural paral-
lelism may result between terrestrial and certain arboreal woodpeckers even
though their legs function differently in locomotion.” “The tail too is apt to
be utilized diversely in woodpeckers ... so that clear-cut differences between
ground woodpeckers and typically arboreal woodpeckers are not apparent.”
The foregoing might at least partially explain the lack of clear-cut differences
in sternal form between partially terrestrial woodpeckers (species of Colaptes;
nos. 24-28, and Picus viridis, no. 36, Fig. 2), and totally arboreal picine
species.

HOOPOES AND WOODHOOPOES

In an attempt to discover other groups in which there is a tendency to ossify
the posterior border of the sternum with the tree-trunk foraging habit, I
examined the hoopoes (Upupidae), which do not hitch up tree trunks, and
the woodhoopoes (Phoeniculidae) , which forage in a variety of postures, but
also by hitching up tree trunks (personal observation; and Clancy, 1964, and
McLachlan and Liversidge, 1957). Upupa epops (Upupidae), and Phoenic-
ulus purpurescens and Rhinopomastos cyanomelas (Phoeniculidae) possess
type 3 (two notched) sterna. The ratio of depth of sternal notch to total
sternal length is given in Figure 3, which graphically illustrates the more
open sternum of Upupa, as compared with Rhinopomastos and Plioeniculus.
Again, small sample size prohibits meaningful statistical testing, but at least
Upupa is clearly significantly different from Phoeniculus. Furthermore, one
specimen of Phoeniculus purpurescens possessed a type 2 sternum (with two
lateral fenestrae), showing even additional closure, much in the same manner
as the woodhewers. Therefore, in general, woodhoopoes appear to show the
same general tendency towards closure of the posterior border of the sternum
associated with tree-trunk foraging as observed in the woodhewers, and begin
with the same sternal ancestry, a type 3 sternum.

Alan

Feduccia

STERNA OF TREE-TRUNK FORAGERS

323

Fig. 3. Means and ranges for the ratio of depth of medial notch of sternum to total
length for Upupa epops (n = 7), Rhinopomastos cyanomelas (n = 3), and Phoeniculus
piirpurescens (n = 5).

POSSIBLE FUNCTION OF THE POSTERIOR BORDER

So far I have merely established a correlation between closure of the pos-
terior border of the sternum with the tree-trunk foraging habit, without elab-
orating on the possible functional reason for the closure.

The avian sternum provides attachment for two major sets of muscles.
Lindsay (1885) pointed out that the outline of the posterior border of the
sternum should in some way reflect the resultant of the forces of these two
jopposing sets of muscles. In the case of the birds under consideration in this
paper, the relative powers of flight would not appear to vary greatly from
one group to another, d hus, flight would not be an obvious place to look for

324

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Fig. 4. Diagram (from Stolpe, 1932) to show the forces acting on the climbing bird.
A downward and inward force, B, and an outward force, C, constitute the two components
of the gravitational pull, A.

functional correlates to explain the form of the posterior border of the ster-
num. However, if one considers the posture of a tree-trunk foraging bird
on the trunk (Fig. 4), with the forces acting on a climbing bird, then one
should be able to postulate the manners in which the bird could counteract
the gravitational forces which act to pull the bird downward. Figure 4 is
taken from Stolpe (1932), and was used by Bock and Miller (1959) to ex-
plain the functioning woodpecker foot. As Bock and Miller pointed out, the
gravitational force. A, is divided into two component forces, B, and C. They
further point out, “Force B, which is the larger of the two components, is
directed downward and inward along the axis of the tail. The tail and fore
toes (two and three) act together to counterbalance force B; the tail provides
the greatest support. The outward force C tends to pull the woodpecker away
from the tree trunk. This force is overcome by a combined action of the
fore toes and the laterally directed fourth toes, of which the latter are prob-
ably the most important.” However, while the fore toes and tail are of para-
mount importance in counteracting the gravitational forces, certain muscles
must also function in this capacity. The most obvious set of muscles which
might counteract the outward component force (C) are the abdominal mus-
cles, and indeed, it is this set of muscles which attaches to the posterior border
of the sternum. The main muscles involved are the M. obliquus externus
abdominis, M. rectus abdominis, and M. transversus abdominis, all of which
originate along the posterior border of the sternum (see Burt, 1930). I would
postulate that the outward component force C is additionally counteracted by
increasing the forces exerted by the abdominal muscles, thereby necessitating
an increase in the strength of the posterior border of the sternum. Although

Alan

Feduccia

STERNA OF TREE-TRUNK FORAGERS

325

I have not had the opportunity to examine the abdominal muscles of creeping
and non-creeping piciforms, I have examined these muscles in an ovenbird
and woodhewer of approximately the same size { Autumolus ochrolaemus and
Xiphorhynchus guttatus) . My qualitative observations clearly showed that
the woodhewer possesses much more mass in all of the abdominal muscles.
Quantification of these types of comparisons will be necessary to fully test
this hypothesis ; until then it may at least bear the name of a strong hypothesis.

Though I have attempted to outline a general functional anatomical reason
for an increase in sternal ossification in the posterior border of the sternum
in tree-trunk foraging birds, there may be other factors involved. Short
(1971) emphasizes what he calls the attribute of “toughness” of woodpeckers.
Such undefinable attributes associated with climbing and tree-trunk foraging
habits probably account for the fact that (Short, op. cit., p. 21), “. . . wood-
peckers are remarkably thick-skinned, tough birds that are tenacious of
life . . .” The same general attributes are assignable to woodhewers as well,
and may be assessed, though poorly understood, as having to do with tree-
trunk foraging adaptations.

PHYLOGENETIC ALTERNATIVES

Bock (1967:67) introduced the term paradaptation to apply to “Those
aspects of a feature that are dependent upon, resulting from, or under the
control of chance-based evolutionary mechanisms . . .” He used as his ex-
ample the evolution of perching feet in birds. Anisodactyl, syndactyl, zy-
godactyl, and heterodactyl feet have evolved in birds as multiple evolutionary
pathways for efficient perching mechanisms. As Bock (op. cit.) pointed out,
“. . . each represents a different adaptation to the selection force for a more
efficient perching foot because each is an adaptive advance for perching as
compared to the ancestral foot.” The perching foot types are therefore “par-
adaptive” because of their chance-based evolution, but are also adaptive in the
sense that each type has been accepted by selection as an efficient perching
foot.

A modified form of Bock’s concept of paradaption (see also Bock, 1969;
and previous emphasis of the role of accident in evolution by Mayr, 1962)
appears to me to be useful in renewed emphasis. However, I do not feel the
'necessity for the introduction of a new term, nor do I feel that the term
“mechanism” should be used in this context, as it carries a connotation of
mutationism or macroevolutionary mechanism. However, it is true that phy-
letic lines begin their evolution with different structural forms which when
placed under similar selection forces may result in different modifications to
achieve similar goals. Thus, I used the term “phylogenetic alternatives” in-
stead of j)aradaj)tation, emj)hasizing differences in phylogenetic background.

326

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Phylogenetic Alternatives

C CD
O <D

5m

O

O) o

c

a ^
^ a

-S

c

C CJ

o

CO

Type 6 Stern um
With Clos ure

Towards Sternal
Types 2 and 1

o

<D

a

HD

o

o

Type 6
Sternum

Type 3
Sternum

Ancestral Sternal Structure (perching birds)

Fig. 5. Schematic diagram (following Bock, 1967) to show multiple evolutionary
pathways of the sternal types of woodpeckers and woodhewers. The two ancestral sternal
types (6 and 3) were first under the same selection force for a more efficient sternal type
for perching, later under the same selection force for tree-trunk foraging. Vertical dif-
ferences are adaptive; horizontal differences are owing to the ancestral character state.

but not as a macroevolutionary mechanism; these are simply aspects of evo-
lutionary opportunism. In Figure 5, I have attempted to show how this con-
cept might apply to the posterior border of the sternum, following the diagram
given by Bock (1967) for the evolution or foot types in birds. In this case,

Alan

Feduccia

STERNA OF TREE-TRUNK FORAGERS

327

there are multiple pathways of evolution. Type 6 sterna evolve in early picines
and type 3 sterna in the ovenbird ancestors of woodhewers, both under similar
selection forces for a more efficient sternum for perching; but “evolutionary
background” provided each group with different, but perhaps equally effi-
cient, sternal types. When tree-trunk foraging groups evolve from each evo-
lutionary line, the selection force changes to produce an efficient sternum for
tree-trunk foraging. However, with the different evolutionary backgrounds
in each group, a slightly different solution to the problem is found in each
case. In the woodpeckers, the solution is apparently to increase closure of the
border of the sternum by ossification; in the woodhewers, the number of
notches becomes reduced.

SUMMARY

The evolution of the posterior border of the sternum in unrelated groups of tree-
trunk foraging birds may be characterized, in general, by a tendency to increase the
ossification of the border. In woodpeckers, which possess a four-notched sternum (type
6), there is an increase in the amount of closure of the notches. In woodhewers and
woodhoopoes, which possess basically a two-notched sternum (type 3), there is a tend-
ency to reduce the notches, resulting in some species in type 2 (with lateral fenestrae) ,
and even type 1 (with no notches) in one species. Increasing the ossification of the
posterior border of the sternum in the Dendrocolaptidae, Picidae, and Phoeniculidae is
probably associated with increasing the strength of the sternum for tree-trunk foraging.

ACKNOWLEDGMENTS

Dr. R. W. Storer of the University of Michigan encouraged this study. Specimens
examined were made available through the courtesy of R. W. Storer, University of Mich-
igan Museum of Zoology, R. L. Zusi, U. S. National Museum, and Pierce Brodkorb,
Collection of Pierce Brodkorb. My studies on suboscine birds were generously supported
by grants from the Frank M. Chapman Memorial Fund of the American Museum of
I Natural History and a Grant-in-Aid of Research from The Society of Sigma Xi. My
observations of hoopoes and woodhoopoes were made while in Africa on a trip sponsored
by the National Geographic Society. Peter L. Ames and Helmut C. Mueller kindly criti-
cized the manuscript and offered many helpful suggestions.

LITERATURE CITED

Bock, W. J. 1967. The use of adaptive characters in avian classification. Proc. XIV
Internatl. Ornithol. Congr. 1966:61-74.

Bock, W. J. 1969. Comparative morphology in systematics, p. 411 -448. In Systematic
Biology. Natl. Acad. Sci. Publ. No. 1692.

Bock, W. J., and W. I). Millkr. 1959. The scansorial foot of the woodpeckers, with
comments on the evolution of perching and climbing feet in birds. Aim-r. Mus. Novit..
No. 1931:1-44.

Burt, W. H. 1930. Adaptive modifications in tbe woodp(‘ckers. Univ. California Publ.
Zook, 32:4.5S-524.

328

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Clancy, P. A. 1964. The birds of Natal and Zululand. Oliver and Boyd, Edinburgh
and London.

Feduccia, J. a. 1969. Evolutionary trends in the avian families Furnariidae and Den-
drocolaptidae. Unpuhl. Ph.D. Diss., Univ. Michigan.

Heimerdinger, M, a., and P. L. Ames. 1967. Variation in the sternal notches of sub-
oscine passeriform birds. Yale Univ., Peabody Mus., Postilla, 105:1-44.

Lindsay, B. 1885. On the avian sternum. Zool. Soc. London 1885, Proc.:684-716.

Mayr, E. 1962. Accident or design, the paradox of evolution, p. 1-14. In The evolution
of living organisms (G. W. Leeper, Ed.), Melbourne Univ. Press, Victoria.

McLaciilan, G. R., and R. Liversidge. 1957. Roberts Birds of South Africa. Cape &
Transvaal Printers Ltd., Cape Tow^n.

Short, L. L. 1971. The evolution of terrestrial woodpeckers. Amer. Mus. Novitates,
no. 2467, pp. 1-23.

Spring, L. W. 1965. Climbing and pecking adaptations in some North American wood-
peckers. Condor, 67:457-488.

Stolpe, M. 1932. Physiologisch-anatomische Untersuchungen uber die hintere Ex-
tremitat der Vogel. J. Ornithol., 80:161-247.

DEPARTMENT OF ZOOLOGY, UNIVERSITY OF NORTH CAROLINA, CHAPEL HILL,
NORTH CAROLINA 27514. 20 AUGUST 1971.

ANNOUNCEMENT

The Proceedings of the First Conference on the Status of the North American Osprey
are expected to be available for distribution in late summer. This conference met in
February 1962 at the College of William and Mary, under the chairmanship of Mitchell
A. Byrd. Eighty persons attended the three-day affair. Copies of the Proceedings may
he obtained by writing Dr. Mitchell A. Byrd, Department of Biology, College of William
and Mary, Williamsburg, Virginia 23185. A hill will be sent at the time the order is
filled, and no money need accompany the order. The price is expected to he no more
than $2.

CRANIAL PNEUMATIZATION PATTERNS AND BURSA
OF FABRICIUS IN NORTH AMERICAN SHOREBIRDS

Raymond McNeil and Jean Burton

A study of age criteria in some species of North American shorebirds
brought us to consider two of the best known techniques of age deter-
mination in birds, the size of the bursa of Fabricius and the degrees and pat-
terns of skull pneumatization. The only attempt, known to us, to correlate
bursa of Fabricius and gonadal development with the ossification of the skull
is that of Davis ( 1947 ) .

The bursa of Fabricius is a lympho-epithelial organ lying dorsally above the
cloaca. At least in some species it has an opening in the cloaca. It reaches its
maximum size at 4-6 months and then begins involution (Davis, 1947). By
cloacal examination of the bursal pouch, it is possible to distinguish juvenile
from adult individuals of some taxa of birds especially Anseriformes and
Galliformes (Gower, 1939; Hochbaum, 1942; Linduska, 1943; Kirkpatrick,
1944). Unfortunately, in shorebird species, the bursa of Fabricius has no
cloacal opening and thus cannot be used as an age criterion of living birds.

The pneumatization of the skull has been used as a criterion for estimating
the age of birds by C. L. Brehm as far back as 1822 (Niethammer, 1968),
but it was not generally used until the turn of the century ( Serventy et ah,
1967). Miller (1946) describes the skull ossification process as follows:

“The skull of a passerine bird when it leaves the nest is made of a single layer of bone
in the area overlaying the brain ; at least, the covering appears single when viewed mac-
roscopically. Later the brain case becomes double-layered, the outer layer being separated
from the inner layer by an air space across which extend numerous small columns of
bone. . . . Externally the skull of an immature bird appears uniform and pinkish in live
or freshly killed specimens. The skull of the adult is whitish, due to the air space, and
also it is finely speckled as a result of the dense white bony columns between the layers.”

Nero (1951) and Serventy et al. (1967 ), in their respective studies of Passer
doinesticus and Taeniopygia castanotis, give examples of the pattern and rate
of cranial ossification, from the juvenile to the adult; through a series of
stadia ending with the complete pneumatization of the cranial roof in the adult
before it is one year of age. This general rule, applied to the Passerines, ad-
j mits some exceptions as mentioned by White (1948), Chapin ( 1949), (irant
(1966), McNeil and Martinez (1967), and Payne (1969). Chapin (1949)

, also reported that “swifts and small sandpipers retained a condition through-
I out life that suggested immaturity. In some other larger birds the pneumatiza-
' tion of the cranial vault seemed to proceed very rapidly.” Other workers like

I Chapin (1949), Verheyen (1953), Harrison (1958, 1961) were interested in

I

329

i

1

I

330

THE WILSON BULLETIN

September 1972
Vol. 84. No. 3

the evolutive and adaptive significance of the fully versus incompletely pneu-
matized skull in birds.

Although cognizant of the fact that adult shorebirds have incompletely
ossified cranial roofs, we undertook the present studies to ascertain whether
or not the rate of skull ossification can be used as an indication of age in
living and dead birds.

MATERIAL AND METHODS

Series of shorebirds representing 21 species were collected in the Kamouraska region,
Quebec, on the south shore of the St. Lawrence River in 1968 (spring, summer, and fall)
and 1969 (spring), and on Magdalen Islands, Quebec, in fall 1969. A few specimens
also were brought from Venezuela by the senior author in November 1968. These speci-
mens were all prepared as study skins to examine the age characteristics, but the skull
roofs were removed and kept separate for further examination of the unpneumatized
areas. These skull vaults were then held against a window allowing light to illuminate
the unpneumatized areas which were outlined.

The cloaca of each bird was excised and measurements (mm) were taken of the length
(A) and height (B) of the fresh bursa of Fabricius; both measurements were used in
the approximation of the size of the organ ( AB ) . All birds which had a bursa of Fabricius
were considered as immature. However, some birds which had a damaged cloaca were
considered as immature if they bore juvenile feathers, especially among the wing coverts.
In addition to the above mentioned specimens, we used measurements of the bursa taken
by Miss Frangoise Cadieux during another study.

RESULTS AND DISCUSSION

Bursa of Fabricius. — The bursa of Fabricius was absent in yearling speci-
mens taken in May and June. Thus the bursa is eliminated within the first
year of growth. Moreover, two specimens from Venezuela in November, a
Least Sandpiper { Erolia minutilla) and a Lesser Yellowlegs (Totanus flavipes),
had almost fully regressed bursae, though their basic I plumage (first winter)
still retained characteristic juvenal feathers. This suggests that, at least in
some individuals, the involution of the bursa of Fabricius is completed in less
than six months.

The measurements of the average size of the bursa ( AB), as shown in Table
1, indicate that the size of this structure diminishes from July to November.
The best examples are the Semipalmated Plover (Charadrius semipalmatus) ,
the Ruddy Turnstone {Arenaria interpres), the Greater Yellowlegs {Totanus
melanoleucus ) ^ Lesser Yellowlegs, and the Short-billed Dowitcher (Lirnno-
dromus griseus ) . The same general trend appears in most of the twelve re-
maining species, but less clearly because of too small sample sizes.

Cranial Ossification Patterns. — All adult as well as immature skulls were
characterized by the presence of unpneumatized “windows,” the size of which
shows great individual variations. Two different patterns of cranial pneumati-

McNeil
and Burton

AGE CRITERIA IN SHOREBIRDS

331

332

THE WILSON BULLETIN

September 1972
Vol. 81, No. 3

Fig. 1. Different stages of the type I of cranial pneumatization pattern in North Amer-
ican shorebirds. The clear areas represent the absence of pneumatization.

zation are found among the species of shorebirds belonging to the two families
that were investigated ( Charadriidae and Scolopacidae ) . The type I ( Fig.
1) occurs in the majority of the species of both families (Table 2). It was
divided into ten stages of degrees which do not clearly appear to be related
to age but may be progressive. Four species had a different pattern that we
are designating as type II (Fig. 2), in which we distinguished six consecutive
stages. These species were the Common Snipe iCapella gallinago), Knot
iCalidris canutus) ^ Short-billed Dowitcher, and American Woodcock {Philo-
hela minor) .

Cranial pneumaticity cannot be used as an indication of the age of shore-
birds. In fact, no clear correlation exists between the age of the birds and
the extent to which their skulls are ossified (Tables 2 and 3) ; some immature
(first year) birds have a skull roof as pneumatized as that of some adults.

McNeil
and Burton

AGE CRITERIA IN SHOREBIRDS

333

Fig. 2. Different stages of the type II of cranial pneumatization pattern in North Amer-
ican shorebirds. The clear areas represent the absence of pneumatization.

However, the different stages found in each type of cranial ossification are
probably time progressive. Categories 7 and 8 in Table 2 are found almost
exclusively in the adult age class, which suggests that there may he some age
significance.

The extent of skull ossification attained in the shorebird species following
the type I of cranial pneumatization (Table 2) varies between the genera and
species. It seems obvious that the genera of Charadriidae attain a higher
degree of cranial ossification than the genera of Scolopacidae. The stages or
I categories numbered 6, 7 and 8 are found almost exclusively in Charadrius,
Pluvialis, Squatarola, and Arenaria, while the stages numbered 1 and 2 are
I found almost exclusively in the genera of Scolopacidae, especially in Erolia,
I Ereunetes, Limosa, and Crocethia. The two Totanus species seem to he inter-
mediate between the two groups. It would he hazardous to draw conclusions
I about Numenius, Actitis. and Tringa because of the small sample sizes.

1

334

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

(0 3

bOf

rt

55

^ CO

O KD
CO \D

00

00 ^

. ,

CO

VO

1— 1

rH CO

(N

CO

CO

O

o

o to

O

o

to

d

d

d

(N

1— 1

o

Tf CO

1— 1

O

. — .

1—1

, ,

CO

(N

ON

CO

1— 1

ca

i-H

pH

(N

s,^

o

o

to

o

o

o

O

CO

d

(N

d

d

o

d

CO

(N

to

(N

CO

0^1

(M

•—1

p-H

o

CO

CO LO

i—i c^j

o o

I— I CO
rf rf
00 Tj<’

CO O

a\ o
to to

CO O

d d

(N CO

CO O O

CO »o d
CO (N to

o o o
odd

I— I LO to

o o
d to

t-H (M

cm CM CM CM CM Cm Cm <im cm

o

t.

e

e

a

Cr-

a

a

a

a

Or

CT)

<n

a

ca

o

a

->a

cx

Totanus melanoleucus A 22.5(16) 57.7(41) 14.1(10) 4.2(3) 1.4(1)

B 16.0(4) 72.0(18) 12.0(3)

Stages of cranial pneumatization

McNeil
and Burton

AGE CRITERIA IN SHOREBIRDS

335

CO CO

r-'

00

^ o
t-’ o

l-H CS

CSI o o o

CO LO CD O

O UO

r-H lO

VO lO

O CO

vd vd

CO CO

8

^ VO i— I

^ o
o

o

<M (M

CO lO

vd

(N (N

UO

O CO
I— I CO

CO

C'i ^

CO

VO CO

vd

(M Tf

00 o

o 2

CO

cm ccc cm cm <m cm cm cm

k)

The variation is expressed in percentage (and number of examined skulls) falling in each stage of cranial pneumatization.
A = Adult birds without bursa of Fabricius; B = First year birds with bursa of Fabricius.

336

THE WILSON BULLETIN

00

U

J

CQ

<

CO p
CO O
CO o

«

CO

lO CO

d

00 p

d

to

d oj

S s

p p

cd

(M CO

<u

cx

cc l-H
cd d
oa <N

CO cq
<oi o4

cq oq

CO (M

C CQ < P3 «

O

rt'D

•c

•Sf.

tDtiH

S C

■- rt

^■5

t/5 .t;

T3 ^

tr,

o

o3 52

gll

c ..

§e

art

.S i

<u ti

II

OJ ^

•-'i

g'5

rt'3

•Co3

«<

September 1972
Vol. 84, No. 3

McNeil
and Burton

AGE CRITERIA IN SHOREBIRDS

337

A few workers have attempted to find the evolutionary and/or adaptive
significance of the fully versus incompletely pneumatized skull vault in birds.
Chapin (1949) mentioned that “the skull-roof of most woodpeckers is com-
posed of single layer of bone, thicker and stiffer than that seen in the young
of Passeres.” He “considered this as a direct adaptation to their hammering
and the use of the beak as a chisel.” As far as Verheyen (1953) is concerned:

“les os dermiques pneumatiques presentent . . . I’avantage de mieux resister aux vibrations
et de mieux amortir les secousses que les lames epaisses qui manquent de souplesse. Aussi
la plupart des especes arboricoles (done celles qui, au cours de leurs evolutions aeriennes,
peuvent se cogner la tete contre divers obstacles) possedent-elles un crane pneumatique
tandis que celles qui vivent sur I’eau ou qui evitent les terrains boises ont un dermatocrane
incompletement pneumatise.”

On the other hand, according to Harrison (1958), the skull pneumaticity of
birds is related to their mode of life, depending upon whether they are swim-
ming or diving birds, hammering species, swift or slow fliers. Harrison (1964 )
believed that birds “showing diminished pneumatisation can be loosely classi-
fied as “swift fliers” and include such species as the gallinaceous birds (Galli-
formes) which accelerate rapidly, sandgrouse (Pteroclididae) , most of the
limicoline birds (Charadrii), and the swifts Apus apus and A. affinis. An
exception among the Charadrii is the slow-flying Jack Snipe Lymnocryptes
minimus, which develops complete pneumatization.” The present results indi-
cate that the Killdeer, American Woodcock, Common Snipe, Knot, and Short-
billed Dowitcher are the shorebird species that show less unpneumatized
skulls: some specimens of these species had almost fully ossified skulls, almost
as pneumatized as that of the Jack Snipe. One fact is against Harrison’s theory
of swift versus slow fliers. The Common Snipe, while performing its aerial
nuptial evolutions, dives to the ground from at least a hundred yards and then
suddenly, before swooping down upon the ground, turns back abruptly and
starts again the same aerobatics. The Killdeer, American Woodcock, Common
Snipe, Knot and, even the Jack Snipe (Bent, 1927, 1929), also perform aerial
evolutions at the time of breeding, although they are less spectacular. This
means that these species are subjected to a heavy acceleration followed by an
equal deceleration, and according to Harrison’s theory, a much less fully ossi-
fied skull would be advantageous.

On the other hand, we would be tempted to make a comparison between
1 the incompletely ossified skull of shorebirds and the ones of the woodpeckers.
According to Harrison (1964), “the partial absence of skull pneumatization
j in woodpeckers suggests that this type of skull may he relatively heavier and
I i therefore a more effective hammer.” Shorebirds, excluding plovers and turn-
^ stones, feed by prol)ing and making series of holes in sand and/or mud. so
I it may he that a heavier type of skull could possibly he of some advantage.

338

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

SUMMARY

The involution of the bursa of Fabricius begins in the autumn and is fully achieved
by the end of the winter in all studied species. The presence of this organ may be used
as an age criterion in shorebirds collected during fall migrations. The degree of cranial
ossification does not permit distinguishing young birds from adults, since large “windows”
persist generally in adult was well as in juvenile shorebirds. Two different patterns of
cranial ossification are found in shorebirds; one applies to most species while the other
one is found in the American Woodcock, Common Snipe, Knot, and Short-billed Dowitcher.
The genera of Charadriidae attain a higher degree of cranial ossification than the genera
of Scolopacidae. The authors also discuss the adaptive value of the skull pneumaticity.

ACKNOWLEDGMENTS

The study was undertaken as part of the M.Sc. research program of the junior author,
and was supported by a National Research Council of Canada research grant to the senior
author and a scholarship to the junior author. We are indebted to Miss Frangoise Cadieux
who provided some useful data and to W. Earl Godfrey who read the manuscript.

LITERATURE CITED

Bent, A. C. 1927. Life histories of North American shorebirds. U. S. Natl. Mus., Bull.
142.

Bent, A. C. 1929. Life histories of North American shorebirds. U. S. Natl. Mus., Bull.
146.

Chapin, J. P. 1949. Pneumatization of the skull in birds. Ibis, 91:691.

Davis, D. E. 1947. Size of bursa of Fabricius compared with ossification of skull and
maturity of gonads. J. Wildl. Mgmt., 11:244-251.

Gower, I. 0. 1939. The use of the bursa of Fabricius as an indication of age of game

birds. Trans. N. Amer. W'ildl. Conf., 4:426-430.

Grant, P. R. 1966. Retarded or arrested cranial development in a Mexican passerine,
Myiopagis viridicata (Vieillot). Amer. Midi. Nat., 75:142-149.

Harrison, J. G. 1958. Skull pneumaticity in wildfowl in relation to their mode of life.

The Wildfowl Trust Ninth Annual Report ( 1956-1957 ): 193-196.

Harrison, J. G. 1964. Pneumatisation of bone. In Thomson, A. L. (Ed.), New dic-
tionary of birds. McGraw Hill, New York, pp 649-650.

Hochbaum, H. a. 1942. Sex and age determination of waterfowl by cloacal examina-
tion. Trans. N. Amer. Wildl. Conf., 7:299-307.

Kirkpatrick, C. W. 1944. The bursa of Fabricius in Ring-necked Pheasants. J. Wildl.
Mgmt., 8:118-129.

Linduska, j. P. 1943. A gross study of the bursa of Fabricius and cock spurs as age
indicators in the Ring-necked Pheasant. Auk, 60:426-437.

McNeil, R., and A. Martinez. 1967. Retarded or arrested cranial development in
Myiornis ecaudatus. Wilson Bull., 79:343-344.

Miller, A. H. 1946. A method of determining the age of live passerine birds. Bird-
Banding, 17:33-35.

Nero, R. W. 1951. Pattern and rate of cranial “ossification” in the House Sparrow.
Wilson Bull., 63:84-88.

Nietiiammer, G. 1968. Pneumatization of the cranium as a criterion of age. Ihis, 110:
106.

McNeil
and Burton

AGE CRITERIA IN SHOREBIRDS

339

Payne, R. B. 1969. Unpneumatized skull condition in adult Scaly-fronted Weavers,
Sporopipes frontalis. Auk, 86:570.

Serventy, D. L., C. a. Nicholes, and D. S. Farner. 1967. Pneumatization of the
cranium of the Zebra Finch, Taeniopygia castanotis. Ibis, 109:570-578.

Verheyen, R. 1953. Contribution a I’etude de la structure pneumatique du crane chez
les oiseaux. Bull. Inst. Roy. Sci. Nat. Belg., 29:1-24.

White, C. M. N. 1948. Skull ossification in certain Passeriformes. Ibis, 90:329.

DEPARTEMENT DES SCIENCES BIOLOGIQUES, UNIVERSITE DE MONTREAL, C.P. 6128,
MONTREAL 101, QUEBEC, CANADA. 12 OCTOBER 1971.

REQUEST FOR INFORMATION: SANDERLING

For the past two years, the Long Point Bird Observatory has undertaken a study on
the relationship between fat deposition and fall migration in the Sanderling. In conjunc-
tion with this study, a large number of birds have been color-marked and sightings of
these marked birds away from Long Point have indicated that most of the birds fly
directly from the study area to the East Coast.

During 1972, the Observatory hopes to individually color-mark and color-code several
hundred Sanderling in order to further investigate this phenomenon.

Birds will be feather-dyed on the breast and abdomen with one of four colors: red,
yellow, green, or white (no color) ; according to the percentage of the bird’s total body
weight attributable to fat.

The birds will be wing-tagged on each wing with semi-permanent wing tags of the
following colors: black, blue, brown, green, red, orange, yellow, and white. The wing-
tagging will individually identify each bird.

Birds banded on the right leg will be adults and those banded on the left leg will he
immatures.

The Observatory would be pleased if anyone sighting these birds would report the
following information to us: Date of sighting; Location (including nearest city or town) ;
Color of feather-dye on the breast and abdomen; Color of the wing tag on the right wing;
Color of the wing tag on the left wing; Leg on which the bird is banded.

Co-operators will receive a short note explaining the project’s application to the preser-
vation of the Long Point peninsula in a natural state and the date on which the bird
was last seen on Long Point. Reports of marked birds should he sent to: Long Point
Bird Observatory, Long Point, Ontario, CANADA.

»| 1

1

GENERAL NOTES

Spectacular hawk flight at Cape May Point, New Jersey on 16 October 1970. —

After the passage of a moderate cold front through Cape May on 4, 5, and 6 October,
1970; the center of high pressure responsible for it lingered off the coast till 15 October.
This caused for nine days a flow of air from a generally southern and eastern direction
whose w^estern boundary’ extended along a stationary front from the Gulf near New Or-
leans in a northeastern direction west of the Alleghenies and along the St. Lawrence to
its Gulf. It is possible that these continuous southerly winds acted as a temporary brake
on the fall bird migration. A high pressure center moving south from Canada centered
about Kansas on 14 October. Its northwestern winds extended to the Alleghenies on a
front that reached from the St. Lawrence valley almost to the Gulf of Mexico. As it
moved eastward this wide swath of strong northwestern wind swept large numbers of
migrating birds toward the coast. About 15:00 on 15 October, the arrival of this front
in the Cape May area was heralded by thunderstorms and heavy rain which continued
throughout the night until about 09:00 the next morning, tapering off in intermittent
showers about 11:00. The northwest wind, which registered 25 to 30 miles per hour with
occasional gusts up to 50 on a local wind gauge, continued throughout the day.

About 08:30 I was alerted by a neighbor, J. d’Arcy Northwood, to the fact that despite
the driving rain many hawks were on the wing. So I made my way about a quarter-mile
to the Cape May Point State Park, where I met Alfred Nicholson at 09:00. We took up
a station about 100 yards east of the lighthouse, which gave us an unobstructed view to
the north and east over the marshes, to the south over the beach and the ocean, and an
open area to the west for 100 yards with low trees and small buildings in the background.
Flying in a westerly direction as they came down the coast in a wide swath, the hawks
veered toward the north as they approached the tip of the Cape May peninsula.

Our first problem was to come up with a means of approximating the number of Spar-
row Hawks iFalco sparverius) rapidly passing by. W'e finally decided that using the
lighthouse as a reference point, as though it were 12 on a watch lying horizontally in
front of us, we would together scan the area using our binoculars in a clockwise direc-
tion from 12 through 1, 2 and 3 back to 12, the lighthouse. After several trials we

arrived at an estimate of 100 birds seen in one sweep around. We then calculated that

it took about one minute for the 100 in sight at a given moment to be replaced by a
succeeding 100. We checked this method of counting several times in the course of the
morning and arrived at approximately the same figures. The flight continued with un-
diminished intensity for three hours giving us about 6000 Sparrov/ Hawks per hour until
noon. Then the numbers dropped to about 65 per minute making it about 4000 in the
hour from 12:00 to 13:00. Numbers continued to drop as we recorded 2000 hawks from
13:00 to 14:00, 700 from 14:00 to 15:00, 100 from 15:00 to 16:00, and 75 from 16:00 to
17:00. The total for the day was about 25,000 Sparrow Hawks.

A second problem was to assure ourselves that birds were not circling after they left
the Point and passing us a second time. To check on this Alfred Nicholson went about

noon to the Higbee Beach area two miles north of Cape May Point on the Delaware Bay.

He found that the flight continued up the bay shore with all birds flying northward
although in lesser numbers than at the Point. An hour or so later to check the inter-
vening area I went north on the Bay Shore Road for about two miles. This road parallels
the bay shore about a mile inland. Quite a few birds were seen to the west of the road
and only 10 on its east side. All were flying toward the north. This made it evident that
the flight was continuous with no repetitions.

340

September 1972
Vol. 84, No. 3

GENERAL NOTES

341

So engrossed were we with the numbers of Sparrow Hawks that the recording of only
three Pigeon Hawks (F. columbarius) suggests that some of this species were overlooked.
Other hawks recorded were: Sharp-shinned (Accipiter striatus) 613, Cooper’s {A.

cooperii) 6, Red-tailed {Buteo jamaicensis) 7, Red-shouldered {B. lineatus) 4, Marsh
(Circus cyaneus) 82, Osprey (Pandion haliaetus) 14, and Peregrine (F. peregrinus) 4.
Our total for the day was approximately 25,600. This estimate is conservative particularly
in view of the fact that birds flying before 09:00 are not included.

We also noted four Turkey Vultures (Cathartes aura), 15 flocks of Canada Geese
(Branta canadensis) with 50 to 250 in each flock, several flocks of Robins (Turdus
migratorius) , one of about a thousand birds in such a compact mass that it seemed
to bounce along in a gusty wind like a ball, a flock of 13 Great Blue Herons (Ardea
herodius) , and overwhelming numbers of small passerines mostly sparrows and war-
blers.— Ernest A. Choate, Cape May Point, New Jersey 08212, 20 December 1971.

Osprey carrying a mammal. — During our investigation of the Peace River near its
confluence with Branch Creek in Hardee County, Florida, on 6 January 1972 at 14:00,
we were surprised to observe an Osprey (Pandion haliaetus) unmistakenly carrying a
mammal in its talons. The mammal was approximately the size of a squirrel or small
rabbit. The bird flew over at a height of 30 feet about 75-100 feet downstream from our
position. It paralleled the river for a short distance before disappearing into the border-
ing woods.

Ospreys are known to be almost exclusively piscivorous, hut occasionally are reported
to take crustaceans, amphibians, and birds (Brown and Amadon, Eagles, hawks and
falcons of the World, Vol. 1, p. 198, 1968). Bent (Life histories of North American
birds of prey, U.S. Natl. Mus, Bull., 167:368-369, 1938) mentions that Ospreys have
been known to take beetles and reptiles on rare occasions. Sindelar and Schluter ( Wilson
Bull., 80:103, 1968) reported an Osprey carrying what was believed to he a Cardinal
(Richmondena cardinalis) .

We assume this occurrence occurred as a direct result of a large phosphate slime spill
entering the Peace River from a detention pond that burst on 3 December 1971. Over
90 per cent (Florida Game and Fresh Water Fish Commission sample estimate) of the
resident fish were killed by the choking slime. The spill may have forced the Osprey
to turn to other prey items for sustenance — in this case the mammal. — William W. Tait,
H. Malcolm Johnson, and William D. Courser, Southwest Florida Water Management
District, Post Office Box 457, Brooksville, Florida 33512, 28 January 1972.

The migration of the Buff-breasted Sandpiper through Surinam. — The migra-
’ tion of the Buff-breasted Sandpiper (Tryngites subriificollis) through continental South
America, to and from its winterquarters in Paraguay, Uruguay, and Argentina is hut
I poorly known. According to my cooperator Mr. Th. Renssen, who lived for some time at
!' the sugar estate Marienburg (Commewijne Dist.), Surinam and whom 1 thank for sending
I me the specimens mentioned below, it is a regular hut not numerous migrant both in
' the northern fall and spring. It favors open ground with a ver\ low vegetation hut espe-

• I cially recently harvested and burnt over sugar cane fields. This same habitat is fre-
' j (luented by the American Golden IBover iPluvialis dominica) and the Upland Plover

I i Bartramia longicauda) and the Buff-breasted Sandpiper is often in company with these

• two species. The earliest date during the fall migration is 15 August 1969 (sight) and
1 birds were collected (all in the Leiden Museum) on 20 .Sept<*mh<*r 1966 (mah‘, weight

342

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

50.5 g), 17 October 1963 (male, 43 g) the latest record being 13 November 1968 (Male,

60.5 g). In the northern spring there is a sight record on 15 March 1969, the latest
records being two birds collected on 12 May (female, 53 g) and 13 May 1967 (female, 69
g very fat) . It is clear from these records that both fall and spring migration is extended
over long periods and that the birds seem to be in no hurry.

The Buff-breasted Sandpiper is not yet known from neighboring French Guiana
(Berlepsch, Nov. Zook, 15:251, 1909) and there is only a single sight record from Guyana
on 20 April 1965 (Snyder, The birds of Guyana, 1966, p. 96). — F. Haverschmidt, 16
W olfskuilstraat, Ommen, Holland, 7 February 1972.

Congenital foot abnormality in the Ring-billed Gull.^ — During ecological and
behavioral studies of Ring-billed Gulls (Larus delawarensis) on Granite Island, Ontario
(48° 43'N, 88° 27'W), we leg-banded 359 newly-hatched chicks. On 10 June 1971 we
found a one-day-old Ringbill chick with a foot abnormality known as polydactyly (Fig.
1). An X-ray photograph (Fig. 2) indicates the extra foot elements on each leg originated
distally from the median anterior portion of the tibiotarsus. In that the phalangeal
portion of the avian foot normally develops from the distal aspect of the tarsometatarsus,
it is conceivable that, with secondary induction, phalangeal elements may arise from
the metatarsal elements of the tibiotarsus. Although the abnormality reported here is
not bilaterally symmetrical, the middle toe is more fully developed on both sides than
the inner or outer toes. No hallux is apparent on either extra foot. The bird did not
seem to be handicapped by the abnormality at the time of capture.

Relative to the amount of past and current research using larids, the paucity of reports
of congenital abnormalities is somewhat surprising (see Austin, Auk, 86:352, 1969 and
Smith and Diem, Auk, 88:435, 1971). It may be that non-passerines are not able to
adapt their behavior to abnormalities as well as passerines and thus are eliminated rapidly.
This was noted by Pomeroy (Brit. Birds, 55:49-72, 1962) referring to bill abnormalities.

Bellairs (Skeleton. In A new dictionary of birds, A. L. Thomson, Ed, Nelson & Sons,
London, 1964) stated that inherited skeletal abnormalities of many types occur in birds.
However, only the “fowl” have been studied extensively, presumably because of their
economic importance. Napier (Wildfowl Trust Ann. Rept., 14:170-171, 1963) discussed
foot malformations in Mallards (Anas platyrhynchos) and noted polydactyly can occur
from genetically determined increases in mesenchymal plates which later give rise to
the foot. Little information is available on effects of secondary inducers which may affect
early embryonic development in wild birds. Kear (Wildfowl Trust Ann. Rept., 15:99,
1964) summarized results of studies of congenital malformations in wildfowl bred at
Slimbridge, England, She reported an incidence (0.56 per cent) of abnormalities in
1961 which did not occur in the subsequent two seasons and suggested the effects of
agricultural chemicals might be investigated.

We do not infer the malformation reported here is necessarily purely genetic in origin.
Recently Hays and Risebrough (Auk, 89:19-35, 1972) recorded incidences of 0.1 per
cent abnormalities in 1969 and 1.3 per cent in 1970 from a sample of over 4,000 young
Common Terns (Sterna hirundo) and more than 1,600 young Roseate Terns (S. dougallii)
at Great Gull Island, New York. The abnormalities reported by Hays and Risebrough
(ibid.) resemble those produced experimentally in domestic chickens by the chlorinated
dibenzo-p-dioxins and some polychlorinated biphenyls.

In view of a possible important relationship between chemical residues in birds, and
congenital abnormalities we ask for increased monitoring and communication of inci-

September 1972
Vol. 84, No. 3

GENERAL NOTES

343

Fig. 1. Extra digits on right (A) and left (B) of one-day-old Ring-billed Gull.

Fig. 2. X-ray showing polydactyly on both feet of one-day-old King-hill(‘d (fuII.

344

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

dences of these phenomena.— John P. Ryder and Damd J. Chamberlain, Department
of Biology, Lakehead University, Thunder Bay “P,” Ontario, 4 October 1971.

Swallow-like behavior in the Rusty-margined Flycatcher, Myiozetetes cayanen-
sis, in Colombia. — On 20 November 1970, while collecting birds near Mitu, Vaupes,
Colombia, I noticed a curious swallow-like behavior in a pair of Rusty-margined Fly-
catchers {Myiozetetes cayanensis) . During two rainstorms, the flycatchers flew low
over the surface of the water (a river), in company with more than a dozen swallows
engaged in the same type of behavior. Such behavior is of course typical of feeding
swallows, but I find no published description of tyrannids behaving in this manner.

The flycatchers flew like this throughout both rainstorms, each of which lasted approxi-
mately fifteen minutes. They sustained glides for two or three seconds, then regained
their speed with strong and rapid wing beats before gliding again. At least once every
five minutes they rested for about a minute on a branch at the edge of the river, but
did not preen while perched at this time. At the termination of each rainstorm, they
resumed feeding in a fashion typical of this species.

The pair did not appear to exhibit extraordinary powers of flight, as flycatchers are
capable of gliding up to several seconds during routine movements to new perches. Nor
did they appear to endure exceptionally long periods of flight.

The purpose of this behavior was not clear, and it could possibly represent bathing. I
could not ascertain if the flycatchers obtained food while flying in this fashion, but this
possibility cannot be ruled out, as the family exhibits considerable versatility with regard
to feeding behavior. The Great Kiskadee (Pitangus sulphuratus) is reported to take
small fish by “diving just like a kingfisher” (Haverschmidt, Birds of Surinam, 1968) ;
Myiozetetes similis, in Central America, captures aquatic animals by wading out into
shallow water, and picks up food by flying down to the surface of the water (Skutch,
Pacific Coast Avifauna, 34:428, 1960).

I was unable to remain in the Mitu vicinity for more than one day, so I could not
determine if swallow-like behavior was typical of this pair of Rusty-margined Flycatchers.
Professor Jose-Ignacio Borrero, at the Universidad del Valle in Cali, had not observed
comparable behavior in this or any other flycatcher during his extensive studies of
Colombian birds.

One of the specimens is now in the Zoological Collections at Texas Tech University.
The study that made this observation possible was supported in part by the International
Center for Medical Research and Training, Cali, Colombia. — Michael Kent Rylander,
Department of Biology, Texas Tech University, Lubbock, Texas 79409, 12 February 1972.

The recent history of Bachman’s Warbler. — The recent history of Bachman’s
Warbler {Vermivora bachmanii) can best be understood against a background of its
earlier history (1880-1910). For this purpose, it should suffice to mention the records
of only a few observers in Florida — that is, south of the species’ known breeding range,
but on its chief migration route. In the spring migration, Brewster and Chapman
(Brewster, 1891) encountered large, but unspecified, numbers in March, 1890. Of these,
46 specimens were collected! In the same general area, Arthur T. Wayne (1893) col-
lected 50 specimens in 1892 and 1893, but also made no reference to the total number
seen. Farther north, he collected eight specimens on the Wacissa River in 1894 (Wayne,
1895) .

September 1972
Vol. 84, No. 3

GENERAL NOTES

345

In the fall migration, the best documented records were made at Key West, where J.
W. Atkins (Scott, 1887, 1888, 1890a) encountered the species in July and August, 1887
to 1889, collecting at least 58 specimens and seeing a total of perhaps 150 to 200! He
mentioned a peak of “25 or 30” on 8 August 1889. Oddly, there seems to be no mention
of the bird’s occurrence there in spring, although two collected on the Dry Tortugas in
1890 were about 65 miles farther west (Scott, 18906).

Although the numbers seen on the species’ breeding grounds during these early years
were hardly comparable, it seems likely that the chief migration pathway was relatively
narrow, thus concentrating the birds much more, and that Florida received more ornitho-
logical attention than other states in those days. Even so. Embody (1907) found at least
22 singing males in Kentucky in 1906, and collected five of them.

During the present century, numbers apparently dwindled steadily. By the time
Howell’s “Birds of Alabama” appeared (1928) the species was considered “one of the
rarest and least known of the warblers.” He cited only nine records at widely separated
localities, plus one nest in Bear Swamp. Other states experiencing declines in the num-
ber of records during this period (1910-1930) were Louisiana, Georgia, and South Caro-
lina, and it seems obvious that there was indeed a sharp decrease in its total population.

During the time I studied birds in north Alabama (1930’s and early 1940’s) the species
still persisted in small numbers where the habitat was suitable. It may be pertinent to
itemize these records here, though some have been published before (Wilson Bull., 50:
36-41, 1938).

1. Irondale, a presumed migrant seen and heard singing on 9 and 13 April, 1936 (with
Harry Wheeler on the 13th).

2. Moody Swamp, Tuscaloosa, 9 April 1937, a singing male; 1 May 1937, pair and
nest containing three young “scarcely a week old”; with Harry Wheeler. None could be
found there on 29 May, when my journal indicated that “a lot of timber had been cut.”

3. Bear Swamp (Autauga Co.), 8 May 1937, singing male; with Harry Wheeler, et al.
None found on return trip, 1-5 June.

4. Moody Swamp, 25 March 1939, two singing males.

5. Moody Swamp, 27 March 1939, two singing males and one female.

6. Moody Swamp, 8 April 1939, “several”; one male displaying on or about this date,
but female not seen. (Trips to swamp interrupted by illness, c. April 14-20).

7. Moody Swamp, 22 April 1939, “one” (sex?).

Thus there were no records after 22 April 1939, in Moody Swamp, or 1 May 1937, in
that swamp, or 8 May 1937, in Bear Swamp. Early nesting in this species is presumably
followed by early diminution of song, early molt, and early fall migration.

By 1950 Bachman’s Warbler had become truly rare, as a search for published records
since that time reveals. Most of these records appeared in various issues of Audubon
Field Notes, and most records involved a single male. The breakdown of numbers of
individuals by years follows: 1950, 2; 1951, 3; 1952, 3; 1953, 0; 1954, 3; 1955, 2; 1956

and ‘57, 0; 1958, 3; 1959, 3; 1960, 6; 1961, 2; 1962, 1; 1963, 1; 1964 and 65, 0; 1966,

1; no record since 1966. It is interesting to note that nearly all of these records were
made within, or at least not south of, the bird’s geograi)liic breeding limits and involved
singing males. It is under just such conditions that dis<<)very would be enhanced. In
other words, the hundreds formerly seen on migration in Florida stand in striking contrast
to the two reported there since 1949.

It is not necessary to argue for the validity of all of the 30 sight records (no specimens,
! one photograph) over the past two decades, or to hold that all unpublished records

i

1

346

THE WILSON BULLETIN

September 1972
Vol. 8i, No. 3

should be summarily dismissed. The point is simply that the number of records — pub-
lished or unpublished — is roughly proportional to the total population of the species,
thus the picture is a bleak one by any standard. With the full realization of the species’
previous ups and downs, and the consequent risk of being wrong, I nevertheless believe
Bachman’s Warbler to be on the verge of extinction.

At least one experienced ornithologist around 1960 indicated to me a belief that the
bird was probably being overlooked among the hordes of other small, migrating land
birds. However, note that Brewster and Chapman made direct comparisons of its degree
of abundance with that of other species. Although they ranked it less common than the
Parula, Myrtle, Black-and-white, and Yellow-throated Warblers, the Blue-gray Gnat-
catcher, and the Ruby-crowned Kinglet, it outnumbered such relatively common species
as the Orange-crowned \^’arbler, and the Red-eyed, Solitar>', and Yellow-throated Vireos.
Thus, they specified, it ranked seventh in abundance among small woodland transients
along the lower Suwannee River in March.

My recent attempts to find Bachman’s Warbler in two swamps where it formerly nested
have proven futile in each case. I looked for it in early April of 1954 and 1966 in Moody
Swamp, near Tuscaloosa, Alabama, where it was last known to nest, and Dan Holliman
wrote me that he had spent a week in this swamp -without success a few years earlier.
In Bear Swamp, northwest of Montgomery, which is the site of the other Alabama nest,
four of us failed to find it in early April, 1970 and 1972. In other recent years I have
searched unsuccessfully in two other swamps slightly south of its known breeding range.

If Bachman’s arbler is, indeed, on the verge of extinction, what causes may be as-
signed to its sharp decrease? The ans-wers are not easy to find. Although some have
maintained that the draining of swamps is to blame — and it may be in some cases — the
two swamps I revisited in the last ten years appeared much the same as they did when
the bird was there 30 years ago. If they have somehow been made less appealing to the
bird, the difference is too subtle for me to see. Thinking that there may have been wide-
spread habitat destruction on its wintering grounds ( Cuba and the Isle of Pines ) , I con-
tacted Senor Orlando Garrido about the bird's status in Cuba. He concurred that it -v\as
becoming ver>- rare, the last specimens having been taken in 1942. with sight records of
three females as recently as 1963 and ‘64. However, he emphasized that there had been
no important habitat destruction. In the case of the Isle of Pines, Dr. Albert Schwartz
made the same point.

The possibility of over-collecting in the early years has also been mentioned. Some
fragmentary' data, along -vs-ith a bit of reasoning, should exonerate these collectors. The
largest number collected in one day by Brewster and Chapman on the Suwannee River
in 1893 was 10 on 23 March on which date they saw “upwards of 30’’; in other words,
less than one-third of the number seen along one small part of the river on a single day
were actually collected. Their records, however, indicated that the bird occurred at all
points along the river except near the Gulf over a period of at least two weeks. How
many additional thousands may have been in other parts of its migration route during
that period, if not still on its wintering grounds or already on its breeding grounds? How
long should it take such a population, for that matter, to compensate for the entire num-
ber of merely 46 specimens these obseners collected that year? Data given by Atkins
at Key ^'est in 1888 are similar in that few were collected on the days when the largest
numbers were estimated: July 26, 4 out of “2 dozen”; August 6, 5 out of “2 dozen”;
August 8, 5 out of 17. In summaiy, only 14 out of about 40 were collected. Key West,
like the lower Suwannee River, evidently was only a minute part of the bird’s total migra-
tion route. Furthermore, I do not know of a single specimen collected in the United

September 1972
Vol. 84, No. 3

GENERAL NOTES

347

States since 1940, when I had the impression that the bird was in no danger of extinction.
Only three specimens have been collected in Cuba, all in 1942 (Orlando Y. Garrido, pers.
comm.) .

Taking a parallel case, Swainson’s Warbler is also a swamp-inhabiting bird, and its
population today may be less than that of Bachman’s Warbler during the 1880’s and
1890’s. Yet I venture to state that if all licensed collectors living today set out to collect
every Swainson’s Warbler they saw, they would scarcely make a dent in the total
population.

Thus, despite the fact that man has played the major role in the decline of so many
organisms, I doubt that he is guilty in this instance. For some reason, Bachman’s Warbler
seems to be poorly equipped for survival even under the conditions it demands and is not
sufficiently adaptable to survive under different conditions. In the long process of the
evolution, flourishing, and eventual extinction of species, perhaps this is one whose
time has come. In this pessimistic outlook, however, I sincerely hope that I may be
proven wrong.

LITERATURE CITED

Brewster, W. 1891. Notes on Bachman’s Warbler {Helminthophila hachmani) . Auk,
8:149-157.

Embody, G. C. 1907. Bachman’s Warbler breeding in Logan County, Kentucky. Auk,
t 24:41-42.

I Scott, W. E. D. 1887. Another Bachman’s Warbler in Florida. Auk, 4:348.

Scott, W. E. D. 1888. Bachman’s Warbler (Helminthophila hachmani) at Key West,
Florida, in July and August. Auk, 5:428-430.

Scott, W. E. D. 1890a. A summary of observations on the birds of the Gulf coast of
Florida. Auk, 7:lT-22; 114^120.

Scott, W. E. D. 18905. On birds observed at the Dry Tortugas, Florida, during parts
of March and April, 1890. Auk, 7:301-314.

Wayne, A. T. 1893. Additional notes on the birds of the Suwannee River. Auk, 10:
336-338.

Wayne, A. T. 1895. Notes on the birds of the Wacissa and Aucilla River regions of
Florida. Auk, 12:362-367.

Henry M. Stevenson, Department of Biological Science, Florida State University, Talla-
hassee, Florida 32306, 1 January 1972.

< I
tf*

Winter habitat of Kirtland’s Warbler. — The alarming decline of Kirtland's War-
blers {Dendroica kirtlandii) on the nesting ground in northern L<jwer Michigan (May-
field, Auk, 89:263-268, 1972) has stimulated interest in its survival problems on the
wintering ground in the Bahama Islands. As an aid to those who may he looking for
the bird in the Bahamas, I am bringing together what we know about the winter habitat.

Observers have found Kirtland’s Warbler on several of the major islands of the
Bahamas from the northernmost to the southernmost, hut no one has seen it in winter on
the nearby mainland of Florida nor on the nearby islands of (.uha and Hispaniola. I he
greatest numbers of reports have come from those islands visited by the greatest numbers
of bird students. On New Providence near Nassau collectors took 45 specimens between
1884 and 1915; and on Grand Bahama visiting groups of the Florida Audubon Society
and local residents have found it every year from 1959 through the 1960s.

348

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Yet the bird has proved diffieult to find by those seeking it. James Bond spent about
100 days in these islands, mainly in the 1930s, and saw the Kirtland’s Warbler only once.
Josselyn Van Tyne and I spent 59 man-days on New Providence and Eleuthera searching
for it in January and February of 1949, and I have made a number of brief trips to
Great Abaco, Grand Bahama, and Inagua since that time without ever finding the bird.
John Emlen spent about 500 hours systematically combing measured tracts on Grand
Bahama and Andros, with brief visits to other islands from 1968 to 1971, without seeing
it. His time in the field exceeded 200 days. Others have had similar experiences for
shorter periods.

Unless the birds are concentrated in some locality or in some unusual habitat not
yet discovered, the prospect of finding them is discouraging indeed. The 400 Kirtland’s
Warblers in existence in 1972 are to be sought on 4,466 square miles of the Bahamas
distributed among 15 islands larger than 10 square miles each, 700 smaller cays, and
2,400 “rocks.”

The person with most experience with Kirtland’s Warbler on its wintering ground
was C. J. Maynard, who collected 38 specimens between 1884 and 1915 on New Providence
and Eleuthera. Writing in 1896 about his experience in 1884 when he collected 26 speci-
mens, he described the behavior and habitat of these birds as follows: “. . . shy birds
of solitary habits, for never in any case did I find two together. They inhabit the low
scrub, preferring that which is only three or four feet high, but retire at night to roost
in the higher, more dense shrubbery near the spots which they frequent during the day.
Those taken were, with one or two exceptions, found in an exceedingly limited area,
within a mile or two of the city [Nassau!, and always in old fields grown up to low
shrubbery . . . the only note that they uttered was a harsh chirp, with which they greeted
me when alarmed at my approach. When one was not secured at first sight, it generally
retreated into the bushes and silently disappeared. The thick and tangled character of
the scrub rendered any quiet or swift pursuit impossible, thus a retreating bird was never
seen again that day, and a number escaped this way . . . twice at least as I was making
my way through the thickets in search of the Greater Yellow-throat . . . birds appeared
from out of the thieket within a yard of my path, remained a few seconds then darted
off into the scrub.” (Birds of eastern North America, rev. ed.:594).

C. B. Cory, who collected the first winter specimen (on Andros) on 9 January 1879,
said it behaved like a Myrtle Warbler ( Dendroica coronata) and seemed to prefer thick
brush (Bull. Nuttall Ornithol. Club, 4:118, 1879). The last winter specimen also was
taken in brush, on Watling Island (San Salvador) on 27 December 1965, “. . . at the
edge of an extensive area of scrub forest or low coppice with canopy about 8 to 10 feet
above the ground, i.e., composed of what eould be called small trees . . . Palms were
scarce there.” (Dennis Paulson, in litt., 22 October 1966).

All modern observers mention the presence of scrub: on Inagua between 1935 and
1940 “in scrub near the sea” (Janies Bond, in litt., 22 March 1946) ; on Eleuthera in
“scrub growth” (Margaret Hundley, Auk, 84:426, 1967) ; on Paradise Island, called Hog
Island before 1962, across the harbor from Nassau “in low broad-leafed scrub . . . along
a path through a plantation of Australian pine, Casiiarina equisetijolia’^ (David Challinor,
Jr., Wilson Bull., 74:290, 1962), and in “woods . . . fairly open, consisting of tall pines
[Ca5«anna?l with a considerable (but not dense) undergrowth of palmettos and uni-
dentified broad-leaved shrubs rather than in the pines.” (George Wallace, Jack-Pine
Warbler, 46:7, 1968).

The first of the modern series of records on Grand Bahama came in November, 1959,
“in scrub and Casuarina growth near West End airport (Dorothy Blanchard, Jack-Pine

September 1972
Vol. 84, No. 3

GENERAL NOTES

349

Warbler, 43:39-42, 1956). Charles F. Walker saw the bird at West End on 28 December
1969. He detected it first on the lawn of the hotel, watched it pursue a moth to the
concrete floor of the porch, fly to the top of a small shrub in the lawn, and finally
vanish at low level in a dense row of broad-leaved shrubs. Although he searched the
area carefully for the next several days, he did not find the bird again (30 December
1971). However, the “usual place” for finding the Kirtland’s Warbler on Grand Bahama
has been an open stand of large . . Caribbean pine iPinus caribeae) with an under-
story of poisonwood {Metopium toxiferum) and palmetto (Serenoa repens) P (Hundley,
op. cit.). Here the Kirtland’s Warblers gleaned food from the trunks and branches like
Black-and-white Warblers (Mniotilta varia) . In April, 1969, Paul Fluck mist-netted and
banded a Kirtland’s Warbler “in fairly open, young Caribbean pine about 25 feet high,
with a shrubby understory” (John T. Emlen, in litt., 14 December 1971).

From all of these reports, old and modern, I conclude that the Kirtland’s Warbler
usually inhabits low broad-leaved scrub in the Bahamas. Areas that have been cleared
and then allowed to grow back but have not yet reached their maximum height and
density may hold particular promise. I think it is significant that no one has reported
them in the high scrub or coppice, trees 15 feet or more in height, that abounds in these
islands. The presence of pines where the warblers have occurred repeatedly on Grand
Bahama I think may be incidental or of secondary importance. By shading and by en-
couraging ground fires the pine may hold back the brushy understory to the desired
state of sparseness and low height. All of the large pines I have examined show fire
scars at the base. Only the northernmost islands of the Bahamas have pines, and even
on these the Kirtland’s Warbler has occurred frequently on portions that have no pines.
The several mentions of Australian pine I think is a consequence of the widespread
planting of this exotic in resort areas visited by tourists; that is, the tree happens to be
where the visitors are.

Unfortunately for the searcher, low broad-leaved scrub is abundant on all the islands
of the Bahamas. — Harold F. Mayfield, 9235 River Road, WaterviUe, Ohio 43566, 14
January 1972.

Stability of a population of male Red-winged Blaekbirds. — An important aspect -
in the survival of a species is its ability to recover rapidly from a low population resulting_
from some catastropher The history of a population of Red-winged Blackbirds (Agelaius
phoeniceus) for 8 years illustrates a method of rapid increase after a decline occasioned
hy a series of drought years. During the drought the number of nesting females declined
drastically but the number of males holding territories remained essentially constant.
This arrangement permitted rapid increase once conditions became more favorable be-
i cause the males were ready each year on their territories for the available females.

The Redwings of Millbrook Marsh near State College, Pennsylvania were studied by-
several persons beginning in 1960. The details of the vegetation changes resulting from
a drought are recorded by Brenner (Amer. Midi. Naturalist, 76:201-210, 1966). His
I data show that monthly precipitation in 1960, 1962, and 1963 was about 20 per cent below
I normal. During these years a rainfall deficit of 26 inches occurred, mostly during the
I growing season. During this drought the marsh changed from vegetation, measured in
I biomass, composed of cattails 148.3 per cent) and sedges (39.3 jx'r cent) to few cattails
' (4.6 per cent) and many sedges (89.5 p('r cent). For five years the territories of the
breeding males were mapped in considerable detail ( Breniu'r, op. cit.). For 196.5 67
I Peek mapped the territories. In these latter years, due to some changes in drainage of

350

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

the stream, an adjacent area became available for Redwings and the total population of
the marsh increased. However, the figures cited here refer only to the area inhabited
originally in 1960.

The number of territorial males beginning in 1960 are: 21, 17, 19, 17, 18, 21, 20, and
19. Data for the number of females for all years except 1965 are: 42, 35, 19, 7, 17, ?,
28, and 30. It will be noted that although the number of males remained stable the
number of females dropped as low as seven at the time of maximum drought and then
returned to a normal level. Thus, while the total population changed rather drastically
and the production of young decreased during the drought, nevertheless, the number of
males remained constant. These males were ready for maximum breeding as soon as
the drought ended and the marsh again became suitable for nesting. It would appear
that the system of stability of males allows a population to recover rapidly from a low
level.

Brown (Wilson Bull., 81:293-329, 1969) commented on the report by Brenner (op.
cit.) from a somewhat different viewpoint. He noted that the territorial behavior sta-
bilized the male population and buffered the breeding density. — David E. Davis, North
Carolina State University, Raleigh, North Carolina 27607 and Frank Peek, University
of Minnesota, St. Paul, Minnesota, 10 January 1972.

NEW LIFE MEMBER

Dr. M. Philip Kahl of Naples, Florida is
a new Life Member of the Wilson Ornitho-
logical Society. Dr. Kahl, who holds de-
grees from Butler University and the Uni-

versity of Georgia, is currently engaged in
research on the flamingos of the world
under grants from the National Geographi-
cal Society, the New York Zoological So-
ciety, and the International Council for
Bird Protection. He is a recognized
authority on the large wading birds and
has published some 18 papers as a result
of his studies. His interests extend to wild-
life photography, and persons who attended
the banquet at the Williamsburg Annual j
Meeting will remember his excellent film
on the storks of the world that was shown
on that program, although Dr. Kahl was
not present. Dr. Kahl is married and has
one son, and is a member of the AOU, the
BOU, and the Deutsch Ornithologen-
Gesellschaft.

ORNITHOLOGICAL NEWS

The full account of the 1972 Annual Meeting appears elsewhere in this issue but it
is appropriate that we offer further congratulations liere to Frances James for winning
the Edwards prize for the best paper published in The Bulletin in 1971, and to Anthony
Erskine as runner up for this prize, as well as to W. John Richardson for winning the
Alexander Wilson Prize for the best paper presented by a student or non-professional
at an Annual Meeting.

It has been called to the Editor’s attention that many people are unfamiliar with the
Edwards prize. Through the generosity of Ernest P. Edwards, the Society is in the posi-
tion to award a prize of $150 to the author of the best paper appearing in The Bulletin
in a given year, and a prize of $50 for the second best paper. The papers are judged by
a committee of three on the basis of both the caliber of the work presented and the
quality of the presentation.

The Council of Biological Editors has recently published the third edition of the “CBE
Style Manual”, available from the American Institute for Biological Sciences, 3900 Wis-
consin Avenue NW, Washington, D.C. This style manual is the ultimate authority in
matters of style for The Wilson Bulletin. Much of the book is devoted to “helpful hints”
in the preparation of MSS for publication, and prospective authors of papers to be sub-
mitted to The Bulletin will find that consultation of the Manual will make life smoother
for both them and the editor during the process of conversion of a MS to a published
paper.

FROM THE A.O.U.

At the annual meeting of the A.O.U. at Grand Forks, North Dakota on 14 August the
following officers were elected.

President: Joseph J. Hickey Secretary: Richard C. Banks

First Vice-President: George A. Bartholemew, Jr, Treasurer: Burt L. Monroe, Jr.
Second Vice-President: H. B. Tordoff Editor: Oliver L. Austin, Jr.

The Brewster Medal was awarded to Barbara and David Snow for their studies on
Neotropical birds. The newly established Elliott Coues Awards went to Alexander
Wetmore and Niko Tinbergen.

Robert S. Arl)ib, Jr. has been awarded the John Burroughs Medal for excellence in
nature writing for his recent book, “The Lord’s Woods”.

We report with regret the death on 26 May 1972 of Arlie William Schorger, Professor
Emeritus of Wildlife Ecology at the University of Wisconsin, and a former Elective
Member of the Council of the Wilson Ornithological Society, in his 87th year.

I The Membership List of the Society is included as a separate supplement to this issue.

Members should rei)ort any errors of omission or commission directly to the Treasurer,
I Extra copies may be purchased from the J'reasurer.

351

1

ORNITHOLOGICAL LITERATURE

Ecological Isolation in Birds. By David Lack Harvard Univ. Press, Cambridge,

Massachusetts, 1971: 5% X 8% in., xi + 404 pp., 34 tables, 58 text figs, by R. Gillmor.

$12.00.

In the last six years David Lack has written three new hooks, each involving extensive
and intensive reviews of available literature on the ecological relations of birds. The
first, “Population Studies of Birds” (reviewed in the Wilson Bulletin, 79:469-471, 1967),
dealt with the regulation of population size in birds. The second, “Ecological Adapta-
tions for Breeding in Birds” (Methuen & Co., London, 1968), focused on the evolution
and adaptive characteristics of avian breeding systems. The third book, the one being
reviewed here, is devoted to a synthesis of the ways in which similar species achieve
ecological isolation.

The basic theme of the book is that ecologically similar, usually closely related species
of birds differ from one another in (1) geographical range, (2) habitat occupied, or if
they coexist within the same habitat, in (3) foods eaten. Such segregation is considered
primarily an evolutionary result of competitive exclusion. Over the past three decades.
Lack has contributed significantly to the development of current evolutionary and eco-
logical theory, with particular reference to the role of competition. In this book he brings
his extensive knowledge and experience to bear on a detailed review of available infor-
mation on ecological isolating mechanisms in birds.

For his analysis Lack presents a comprehensive survey of those bird groups for which
there is reasonably good ecological information. Specifically, he summarizes and dis-
cusses the ecological relations of the following groups: the European tits; the tits (Parus)
of Asia, Africa, and America; the nuthatches (world- wide) ; the European fringillids;
the European trans-Saharan migrant passerines; other European birds; North American
passerines, hawks, sandpipers, and auklets; African avifaunas, turacos, brood parasites,
and vultures; tropical fruit-eaters, honey-eaters, and seabirds; the Galapagos finches and
Hawaiian sicklebills; the white-eyes (Zosteropidae) ; and an analysis of the avifauna of
a tropical archipelago, the West Indies. In addition to these detailed presentations which
comprise the main chapters of the book, there is an 84-page appendix which contains
tables and summaries of the geographical distribution, habitat preferences, morphological
characteristics, food habits, and foraging methods of the above-mentioned groups of
birds. This compendium, even without regard to the main theme of the book, provides
a very valuable summary of widely scattered and not always easily accessible information.
For this reason alone, the book belongs in the library of anyone seriously interested in
the biology of birds.

The main point of this book is well made — closely related species of birds are ecologi-
cally isolated from one another. The mechanisms involved vary with the taxonomic
group, the geographic area occupied, the habitats present, the characteristics and nature
of the food supply and the numbers and kinds of sympatric species. Separation by
geographic range is most frequent among wholly frugivorous congeners that feed on
similar sized fruit and among land-birds of oceanic archipelagos where ecological diver-
sity is assumed to be low. Isolation by habitat is commonest among congeneric passerines
on large continental areas but is generally widespread in most taxonomic groups.

Closely related species occurring sympatrically are segregated primarily by differences
in foods taken. In some groups, competitive exclusion has resulted in the evolution of
different body or beak sizes; such differences are not usually found among congeners

352

September 1972
Vol. 84, No. 3

ORNITHOLOGICAL LITERATURE

353

separated by range or habitat. In other groups, sympatric species have evolved distinctive
foraging practices, e.g. feeding at different heights or in different parts of the habitat,
presumably also a result of competitive interactions. Large overlaps in the diets of
sympatric congeners are considered to occur only when the food supplies are especially
abundant. As these supplies become scarce, however, the overlap is reduced as each
congener takes different foods. From all examples available to him. Lack concludes
that no coexisting bird species take the same major prey items on a sustained basis.

Although the book provides a comprehensive survey of ecological isolation in a wide
variety of birds, some aspects of this topic are only briefly considered. Lack circumvents
the problem of how much overlap in habitat or in foods taken can he tolerated before
competition becomes a critical factor. This is a very important practical matter that
has to be considered in each case and is subject to different opinions and interpretations.
A more detailed discussion of the criteria Lack used in making his judgments of each
example would have been most helpful.

In the final chapter of the book Lack touches only briefly on the relevance of ecological
isolation to speciation processes, adaptive radiation, species diversity, and faunal com-
j position. Other related topics that warrant critical analysis are not included. Examples
of these are the effects of ecological isolation on the structure and dynamics of avian
1 communities, and the genetic and ecological factors that operate (d) in the evolution of

!such isolating mechanisms. One wishes that Lack would make these and related topics
the subject of future reviews.

i| Nevertheless, this book provides an extremely comprehensive and useful review of
, current knowledge about ecological isolation in birds. It will provide the basis for con-
j tinning critical studies on the dynamics of ecological relations among birds.

|| I highly recommend the book to anyone interested in birds. It is very clearly written,
I and the drawings and sketches by Robert Gillmor are excellent. — Richard T. Holmes.

I Grundriss der Vogelzugskunde. 2nd Edition. By Ernst Schiiz. Verlag P. Parey, Ber-
;> lin — Hamburg, 1971: 7 X 9% in., xi + 402 pp., 142 figs. DM 88.00.

!j Professor Schiiz, director emeritus of the State Museum of Natural History at Stuttgart
|| and former director of the bird banding stations at Rossitten and Radolfzell, presents
2 a completely revised edition of his comprehensive textbook on bird migration. In addi-
I tion to his elaborate descriptions of the migration patterns of European species, he dis-
|! cusses the migrations of many species from Asia, Australia, New Zealand, Antarctica,
the Americas, and Africa.

1 1 Twenty years of extensive research have passed since the first publication of this
I unique text. New and sophisticated information on the phenomenon and the mechanisms

Iof bird migration has been accumulated. Schiiz has delegated special topics to several
young research ornithologists, H. Oelke (research methods), P. Berthold (physiology),
eland E. Gwinner (orientation).

)f I i In his introductory' chapter, Schiiz stresses the adaptive significance of bird migration,
)D I an important means for the survival of the migratory species and largely the result of
;r- ! their evolutionary history. Apart from a limited glossary, definitions are given throughout
ifj the book. Migration is defined as a periodic and oriented wandering. Application of this
definition poses certain difficulties as there are numerous forms of transgressions from
strictly resident to migratory species. The introduction lists the important institutes and
stations throughout the world that devote their entire work to the investigation of bird
migration. Historical sketches illuminate the origins and developments of the German

354

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

bird banding stations at Heligoland, Rossitten (now Radolfzell), and Hiddensee. The
introduction of the term “Vogelwarte” (bird banding station) dates back to 1883 when
H. Gatke first used it for the famous Heligoland station.

The brief descriptions of research methods pertain to the qualitative and quantitative
aspects of bird-watching, recording of flight calls, banding procedures, the Louisiana
“moon-watching,” photography, radio and radar telemetry.

The following chapters can be considered the core and masterpiece of the Schiiz text.
They contain substantial descriptions of different patterns of migration exemplified by
migrant species from all over the world. Included are topics on specialized migrations
such as the concentrated “flyway” movements in coastal ranges, the modifying effects of
off-shore islands and lighthouses on the flight pattern, migrations across mountain passes,
along river systems, and the importance of oases in desert habitats. The detailed descrip-
tion of the migration patterns of a variety of 15 species is very informative. Among these,
the White Stork has been Schiiz’s favorite subject through many years of pioneering
research which contributed much to our understanding of bird migration. Particular
aspects of migration, such as aerial, terrestrial, and aquatic locomotion, diurnal and
nocturnal flights, social contacts of migrants, their flight altitude, speed, and overall
efficiencies during narrow and broad front migration, are given an excellent treatment.
Schiiz also discusses dismigration (in contrast to site tenacity), range expansion, emigra-
tion, nomadism, and other forms of environmentally induced migratory movements.

The terminology on the categories of migration directions leaves something to be
desired. It might have been better to have defined the “primary direction” not as the
“obviously inborn migration direction” but rather as the species- or population-specific
migratory direction in the absence of disturbing environmental factors. The “secondary
direction” is characterized as the deviation resulting from the influence of landmarks;
however, one should not exclude the modifying effects of various astronomical, meteoro-
logical, electrical, and magnetic forces. In Europe, most of the fall migrations are di-
rected toward the southwest; they are eight times more common than southeast flights,
and south migrations are exceptional.

Berthold’s introduction to the physiology of bird migration consists of chapters on
methods, registration of migratory restlessness, determination of migratory disposition
(fat deposition and energetics). He describes also exogenous and endogenous release
and guidance systems of migration stimulated by climate, food, light, and endocrinolog-
ical processes.

Gwinner informs the reader about the study of migration orientation, compass and goal-
directed flights, time-evaluation and calculation of the solar movement with the aid of
an “internal clock.” His description of stellar orientation is historically and factually
misleading. Gustav Kramer (1949), contrary to Gwinner’s statements, never claimed to
have worked with Blackcaps that had shown preferred directions frequently matching
the autumnal migration direction of the species. Apart from his Red-backed Shrikes,
Kramer had observed a single female Blackcap in ten nightly sessions to show a NE-
preference. As Kramer explained, the bird’s only determinable optical response was
toward the reflected harbor lights of Wilhelmshaven in the northeast. Kramer had not
thought of star orientation but considered effects of shortwave radiation as a guidance
system for nocturnally migrating birds. After our first studies of the nocturnal migratory
flights of sylviid warblers (Sauer and Sauer, 1955), in which the shooting-star response
of our birds led us to the concept of star orientation, Kramer visited us in our laboratory
at Freiburg. He thought our experimental cage a horrible stovepipe device into which
he would never dare to place a bird. He proposed to lend us two metallic nets with two

September 1972
Vol. 84, No. 3

ORNITHOLOGICAL LITERATURE

355

different, physically selected mesh sizes of mathematical accuracy that we ought to put
over our stovepipe cage in order to filter out undesired radiation and to check the re-
sponse of the migrants with regard to the two sharply defined wavelengths. Our answer
that we first want to test the birds’ response to the planetarium sky in the mariners’ school
at Bremen was met by Kramer with utter disbelief. Later he visited us in the planetarium
during an experimental session. Kramer watched for some time in complete silence.
Finally he signalled to leave, and quietly we stepped out of the planetarium leaving the
active warbler behind. Under the impact of what he had seen, with both his hands in
the pockets of his pants, Gustav Kramer stood speechless for quite a time until he said:
“Im Geist hab ich’s begriffen, im Gemiit bin ich erschiittert.” This was the historical
moment when Gustav Kramer, deeply moved by his emotions, realized the existence of
avian stellar orientation. Never again were the metal nets mentioned in our talks.
Gwinner’s misquote might have been extracted from American ornithological literature
in which it has appeared repeatedly, possibly as the result of faulty translation and sub-
sequent compilation.

Gwinner further refers to directional finding without visual clues. His example of
orientation (not necessarily in the primary direction!) under overcast skies must be
supplemented in so far as one can not rule out a secondary orientation by landmarks both
during the day and at night. The magnetic field of the earth and prevailing winds are
mentioned as further orienting factors. He also discusses briefly the hypotheses on bird
navigation, the mechanisms of goal-directed or bicoordinate flights. A more thorough
treatment of the relevant literature would have brought more enlightenment.

Schiiz concludes the discussions with some illuminating remarks on the origin and
significance of bird migration. Though a translation of this remarkable text into English
appears very desirable, it must be appreciated that the well-illustrated book is clearly
written in generally understandable terms. Readers with some basic knowledge of Ger-
man and a professional or amateur interest in ornithology should be able to dig through it.
Students of bird migration should not bypass this book.- — E. G. Franz Sauer.

Natural History of the Swainson’s Warbler. By Brooke Meanley. North American
Fauna, No. 69. Bureau of Sports Fisheries and Wildlife, U. S. Department of the
Interior, Washington, D. C. 1971: 6 X 9% in., vi -f- 90 pp,, frontispiece, 26 figs.
$0.50. Distributed by Superintendent of Documents, U. S. Government Printing Office,
Washington.

Swainson’s Warbler {Limnothlypis swainsonii) has long needed monographic treat-
ment; Brooke Meanley has supplied an excellent one. He has assembled and digested
all available literature on the species, he has studied the birds in all their major known
breeding habitats, and his approach is carefully ecological. Photographs are numerous
and good, and his bibliography is comprehensive.

Of the North American wood warblers, Swainson’s comes closest to having a split
personality. For many years after its original discovery in South Carolina the species
I was quite comfortably assigned, and in literature restricted, to the southeastern Atlantic
Coastal Plain, and to the lowland swamps adjacent to southern rivers. By common obser-
vation and experience, its breeding habitat was placed in canebreaks and such other
I dense vegetation as could tolerate warm, moist situations. Those who sought the bird on
i its nesting grounds turned to such situations; if they knew where to look they found the
birds, and .Swainson’s got categorized as definitely as has Kirtland’s in a jack pine
! situation.

1

1

356

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Then data of an unsettling nature began to appear. On 14 June 1924, Bibbee collected
a male in breeding condition in Monongalia County, West Virginia, only a few miles from
the Pennsylvania state line. His record was not published for some years, and when it
did appear it was dismissed; the specimen was too obviously an accidental. A short
while later when Jones observed the birds, and found and collected a nest in southwestern
Virginia, he, quite frankly, was not believed, and no national ornithological journal
would publish his data. Presently Wetmore (who had questioned Jones’ record) collected
a specimen in southern West Virginia, and birds were found in the North Carolina
Piedmont.

It remained for Legg, working in hilly Nicholas County, West Virgina, in the Allegheny
Plateau to report the species as a locally common breeder in tangles of rhododendron,
hemlock, mountain laurel, and American holly, at elevations around 1,600 feet. This was
a country of far call from southern coastal canebreaks, and it became imperative that the
range of Swainson’s be reexamined.

The remote village of Mt. Lookout, Nicholas County, W. Va., became a mecca for
those in search of Swainson’s, and to the area came Sutton, Lunk, Brooks, and many
others. All found the birds, sometimes in numbers, and nesting data began to accumulate.

To Meanley and others it seemed logical that these birds of the Allegheny Plateau were
racially distinct from those on the distant coastal plains and riverine swamps. A separate
race was proposed, but this was not acceptable to the A.O.U.’s Check-list committee, so
Limn othly pis swainsonii remains monotypic.

Thanks to the thorough work of Meanley and others, we now know a great deal more
about these birds, and we can even postulate a movement route which allows the birds
to pass from coastal areas to southern Appalachians with no conspicuous gaps in its
nesting range. The Savannah River in its course from mountain to ocean is certainly
one such possible route; there may be others.

Although this bird is frequently considered elusive and difficult to observe, Meanley
correctly points out that while it chooses dark tangles it is often quite tame when found,
and will often allow close observation. In deciduous tangles just outside the limits of
Charleston, West Virginia, DeGarmo, Simms, and many others have studied the species
in one of its habitats of greatest abundance, and Gunn chose this area to record a series
of songs which he includes in one of his LP records.

After careful study of Swainson’s in all its known major breeding places, Meanley
concludes, and this reviewer certainly concurs: “It is possible that the Swainson’s War-
bler can adapt to so-called marginal Coastal Plain habitats better than is suspected.
Some occur there, but these usually are bachelor males. But if the Swainson’s Warbler
ever has to make a last stand it may well be in the Southern Appalachians, where many
of them occur in national forests and national j)arks or in areas unsuitable for agricultural
production.” — Maurice Brooks.

The Trade Wind Zone Oceanography Pilot Study. Part VII: Observations of Sea
Birds, March 1964 to June 1965. By Warren B. King. U. S. Fish and Wildlife Ser-
vice, Special Scientific Report ^ — Fisheries No. 586. June, 1970. 8 X lOFt in., vi + 136
pp., 36 maps and figures, 11 tables, 2 appendix tables. No price given.

This is perhaps the most systematic seabird survey ever planned. Reported here are the
results of a series of cruises devoted solely to seabird ornithology, or what I would call
“pelagic ornithology.” This science has two main directions — one, the analysis of species
variety and distribution of seabirds, and the other, the contribution to comprehensive

September 1972
Vol. 84, No. 3

ORNITHOLOGICAL LITERATURE

357

marine biology through knowledge of the birds’ niches in the pelagic community, espe-
cially in relation to food supply. The present report is a milestone in the study of species
composition and distribution, owing to its multiple analyses.

As King writes, “Sea birds were observed by scientists of the Smithsonian Institution’s
Pacific Ocean Biological Survey Program on a systematic basis in the central Pacific
Ocean for 15 months as a part of the Trade Wind Zone Oceanography Program of the
Bureau of Commercial Fisheries Biological Laboratory, Honolulu, Hawaii. In 3561 hours
of observation, 13,080 sightings were made of 65,707 birds along the replicate cruise track
covering 34,384 nautical miles.” During 17 cruises, each averaging 232.9 hours and 2258
miles of observation (averages calculated by reviewer), 51 species and subspecies were
identified. These cruises covered about 50,000 square miles of the sea east of Hawaii.

Data were recorded on sea surface temperature and salinity, temperature at 10 meter
depth, wind speed and direction, barometric pressure, weather, state of sea, swell direc-
tion and period, visibility, wet and dry bulb air temperatures, type of clouds and their
amount of cover. A 25 minute surface plankton haul was made every evening, but the
correlations with bird abundance are not discussed. Automatic Data Processing (ADP)
as described by King et al. (1967) was used for storage and analysis of data.

The avifauna of the study area consisted of 12 families with 49 species and identifiable
subspecies of 2 more species. The number of species per day ranged from 2 to 15 and
the number of species per month ranged from 17 (July) to 32 (April). These numbers
increased during the spring and fall migration periods. Seabird numbers were usually
highest within 50 miles of Oahu though many were seen as far as 700 miles from land.

Some interesting records may be cited. A banded Diomedea nigripes followed the
ship for 18 hours, 180 miles. This and the less abundant D. immutabllis showed similar
ranges with midwinter expansion and spring contraction correlated with breeding. A
southern species, D. melanophris, was recorded on January 23, 1965 for the first time
in the north Pacific. Analysis of monthly distribution of Pterodroma externa externa
and P. e. cervicalis is a valuable contribution to the knowledge of their pelagic range;
I would add to this one example of the latter race found in Japan (Kuroda, Misc. Rep.
Yamashina Inst. No. 18:222, 1962). Twelve species and subspecies in the difficult group
of Pterodroma were identified (with some inevitable confusion) and their status clarified.
Another important contribution is a detailed analysis of the seasonal ranges of the light
and the southern dark phases of Puffinus pacificus, which were abundant at water temper-
atures of 25°C and 27°C respectively. In storm-petrels, Oceanodroma leucorhoa, besides
winter stragglers of 0. furcata, was the only species that occurred in abundance, although
some 0. castro may have been missed, as tlie author mentions. Monthly distributional
maps of other species, especially the most abundant Sterna fuscata are also valuable.

The species accounts are followed by summaries and discussions of the following items:
monthly summary, islands of origin of seabirds recorded in the study area and modes of
utilization of the area, distance from land, analysis of density, direction of birds’ move-
ments, daily cycles of activity (shown by graphs), environmental influences (winds,
temperature, and salinity) on each species, and flock analysis. Of 893 flocks recorded.
Sooty Terns were present in 76 per cent of the flocks and the m‘xt most common. Wedge-
tailed Shearwaters, were present in 39 per cent. Finally, there are giv(‘n 28 j>ages of
Appendix Tables of daily complete data adapted for ADI’ coding system.

The foregoing is only a bare summary of the contents of this important paper in which
Dr. King has raised pelagic ornithology to a more comprehensive* and analytical level
than ever before. Much, however, remains to be studied, particularly in the marine bio-
logical asp<‘ct of seabirds (see Bourne, I’roc. XIII Internatl. Ornithol. (!ongr.:831, 1963)

358

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

and correlation of the birds with food supply in the marine community (Shuntov, Zool.
Journ., 43:590, 1964; 44:441, 1965). In closing, I take pleasure in extending my con-
gratulations to the author. — Nagahisa Kuroda.

A Naturalist in Costa Rica. By Alexander F. Skutch. Univ. of Florida Press, Gaines-
ville, 1971: 6F2 X 9^4 in., x -f- 378 pp., 2 endpaper maps, 68 photos, 8 drawings.
$12.50.

A good deal of what is known of the lives of tropical American birds, especially during
the vital reproductive period, we owe to the selfless dedication of Alexander F. Skutch.
Here he tells us something of his life and times, his experiences as a struggling naturalist,
his thoughts and aspirations during a residence of thirty-five years in Costa Rica, mostly
at 2,200-2,500 feet above sea level in the General Valley. The book is divided into two
parts: “A Naturalist’s Wanderings” recounts his early years in Costa Rica, “A Naturalist’s
Homestead” describes the site and home selected and built. Both parts contain natural
history observations and philosophical comments, including views on the state of man,
but the major preoccupation is with birds. The bulk of the book consists of items that,
in the case of birds and undoubtedly of other groups, too, the author has published at
least once before, though only one such instance is acknowledged by him. These range
from closely paraphrased condensations and excerpts to lengthy, virtually word for word,
repetitions. Skutch’s writing should appeal to devotees of his choice of words and
humorless style.

The author’s motivation in seeking out a wild place in which to live was the desire to
“penetrate, as far as possible, to the secret springs of this multiplex phenomenon called
life, to understand its significance in the whole vast drama of cosmic evolution. Here
I hoped to have leisure to mature my thoughts on these baffling problems” (p. 140).
His outlook on nature no doubt helped him decide where to settle (p. 191) : “And as
the physician gauges his patient’s health by examining his tongue, so earth’s liquid
tongues reveal her condition: if only they are pure and transparent, she is in a sound
and flourishing state; if they are opaque with silt and debris, she is sick and wasting
away.” Thus, “the Pena Blanca River that formed my eastern boundary ran clear and
pure.” Later (p. 203), we learn that the Pena Blanca River becomes “swollen and
turbid from the afternoon downpours.”

Page 173 offers two examples of the author’s esthetics. “People who regard each
other’s taste in painting, sculpture, or music as barbarous may delight in the same flowers.
This fact might make us question some of the newest theories about art.” “This golden
display is provided by a slender, woody vine of the dillenia family, for which I know
no name more poetic than its scientific designation, Davilla kunthii.''’ The latter sort
of private enthusiasm colors his reaction to the vocalizations of birds.

As a lover of nature the author has strong views about snakes. A long black snake
gliding to a rock almost beneath two young hummingbirds in a nest above a forest stream
elicited these remarks (p. 124) : “A snake intent upon ravin appears to become insensi-
ble to everthing else, at times even to mortal wounds. This one was no exception; it
delayed immobile while I approached and delivered the stroke that sent it writhing
madly into the water, where the current bore it slowly downstream to die.”

In fact, the author wishes for a world in which life has evolved free of “that most
hideous blot on the fair face of nature, predation, the killing and devouring of one
creature by another” (p. 231). “If predation had never arisen, predators would not

September 1972
Vol. 84, No. 3

ORNITHOLOGICAL LITERATURE

359

be necessary to prevent overpopulation. Predation, including its subtle form, parasitism,
is a tragic miscarriage of evolution. It is responsible for some of the worst passions that
afflict that long-time predator, man, and through them for a large share of the evils
from which we suffer” (p. 232). When it comes to the population control of man, he
sees a moral problem (pp. 340-341) : “Are our only alternatives a hideously overpopu-
lated world, afflicted with famine, crime, ugliness, and disease, and a ‘contraceptive
society,’ in which men, women, and children wallow, like pigs in mire, in sex divorced
from its natural function of reproduction, which gives it dignity and makes it sacred”?

Skutch’s observations on the forested part of his property, now an isolated remnant
subject to trespass, could only have resulted from a long-term stay (p. 338) : “It is
widely held that mature tropical forest is a stable vegetable formation that remains essen-
tially unchanged from century to century. Yet in this forest, which appeared mature
when I first saw it, the largest trees have been dying faster than they are being replaced
by younger trees. . . . The explanation of this puzzling phenomenon may be that this
forest has not yet reached its climax but represents an advanced successional stage on
lands cleared by the Indians and abandoned by them centuries ago. Or could it be that
climatic changes, resulting from the destruction of the surrounding woodland, cause the
large, old trees to die prematurely? The smoke-laden atmosphere of the latter part of
the dry season must have some effect. Even the destruction of so many [palmitol palms
must alter the dynamics of the forest.”

There are two very useful appendices. The first, an annotated list of the status of
the species of birds identified by the author on the 100 hectares of his property between
1941 and 1970, to which have been added other species observed by him elsewhere in
the General Valley since 1935, is especially valuable. The second is a chronological list
of the author’s books and articles since 1926. — P. Slud.

The Hungry Bird Book. By Robert Arbib and Tony Soper. Taplinger Publishing Com-
pany, New York, 1971: 5% X 8% in., x + 118 pp., many drawings by Robert Gillmor.
$4.95.

Robert Arbib collaborated with Tony Soper to Americanize “The Bird Table Book,”
a popular British book. Many comparisons are used throughout referring to English
gardens and attendant bird life, but “The Hungry Bird Book” most generally delineates
the variety of birds, specific habitats and foods in the area of North America covered
by Peterson’s eastern field guide referring to that book by page number for each species
named. Only those species likely to frequent feeders and dooryards are included, a total
of 99.

Suggestions for planting to attract birds, instructions and dimensions for nest boxes,
supplementary food mixes, water and feeding arrangements, even an appendix on first
aid make this a “not too technical” comprehensive coverage for use by such as scout
troops, garden clubs, interested homeowners, and the like. Pen and ink illustrations by
Robert Gillmor, both practical diagrams and captivating birds in action, add entertain-
ment to the attendant information. Lists of sources for supplies, book references and
extensive bibliography broaden the use of the book for the would-be enibusiast.

This book would seem to be helpful in answering many of the (pieries that come to
persons reputed to have knowledge of birds. — Nancy Ellison.

360

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Owls. Their Natural and Unnatural History. By John Sparks and Tony Soper.

Taplinger Publishing Co., New York, 1970: 6 X 8Y2 in., 206 pp., col. frontispiece, 17

hi. and wh. pis., many pencil drawings. $5.95.

This book is not a “scientific” product. It is disappointing when judged by such
criteria as use of the relevant literature, evenness of coverage, accuracy, and absence of
teleology and anthropomorphism. It is successful insofar as it provides some general
knowledge of owls for laymen. The most pleasing features are the drawings and photo-
graphs by Robert Gillmor, which add immensely to the attractiveness of the book.

Throughout the book, the authors tend to digress from whatever is under discussion.
This first is overdone to an irritating and distracting degree in Chapter 3, “Numbers of
Owls”, giving the impression that Sparks and Soper were becoming hard-pressed to pro-
duce a whole book on owls. This chapter is a generalized, rambling discourse on
predator-prey interactions, including cyclic population fluctuations and the concept of
food chains. Chapter 4, “Owls and Man”, is subject to the same criticism. Six pages are
devoted to rehashing the problem of DDT and other toxic substances introduced by man
into the environment. Owls are hardly mentioned.

Errors and poor phraseology are not infrequent. For example, in Chapter 5 we are told
that competition from bats and nightjars may have prevented owls from evolving insect-
chasing techniques (p. 146), and that a bountiful food supply stimulated active speciation
in rodents (p. 138).

Chapter 6, the final chapter, “Owls — Their Unnatural History”, is an attempt to gather
together references to owls and folklore about them from a variety of sources including
the Bible, Shakespeare, Chaucer, the Greeks, “Red Indians”, and others. Some of the
information presented is thought-provoking, e.g. “Hooting nearby could mean loss of
virginity to a Welsh girl.” Three short appendices conclude the book.

In summary, “Owls” is a sometimes entertaining but superficial book. Readers should
keep in mind that very little of the literature available on owls was utilized, and that as
a result coverage is uneven and incomplete, and that inaccuracies are not rare. — J. David
Eicon.

Galapagos Islands. Museum Pictorial No. 19. By Alfred M. Bailey. Denver Museum

of Natural History, 1970: 6 x 9 in., paper covered, 85 pp., many photos. $1.50.

Museums commonly dispatch expeditions but rarely report on them to the public.
Here is an account of the Denver Museum’s field trip to the Galapagos Islands in July
and August 1960. The narrative is augmented by a comparison of the experiences of
other field workers who have been there. The very nature of the place makes for inter-
esting reading, and the report is larded with observations upon the plants and animals.
Although the purpose of the expedition was to collect material for a habitat group, several
scientific accomplishments were made. To quote from the Foreword, “The first eggs
of the Galapagos Penguin and dusky gull to be reported were discovered, photographs
were made of nesting dark-rumped petrels in the highlands of Santa Cruz, and infor-
mation was secured covering the nesting cycle of the Galapagos albatrosses.” The booklet
is illustrated with a map and excellent monochrome photographs by Bailey, Robert R.
Wright, and Jack A. Murphy. A bibliography is included. — Peter Stettenheim.

PUBLICATION NOTES AND NOTICES

Field Work of a Museum Naturalist. Museum Pictorial No. 22. By Alfred M. Bailey.
Denver Museum of Natural History, 1971: 6x9 in., paper covered, 192 pp., many
photos. $2.50.

This is an account of the author’s field work in southeastern Alaska from 1919 to 1921
for the U.S. Biological Survey, and in Arctic Alaska from 1921 to 1922 for the Denver
Museum of Natural History. Although it is intended primarily as a popular account,
there is much information of value about conditions in Alaska as they were 50 years ago.
The booklet is abundantly illustrated with photographs of the natives, the wildlife, and
the scenery. — G.A.H.

Birds of the Buffalo Creek Region, Armstrong and Butler Counties, Pennsylvania.
By W. E. Clyde Todd. Edited, with an introduction, by Mary Heimerdinger Clench.
Audubon Society of Western Pennsylvania, 1972: 6 x 9 in., paper covered, 21 pp, 6
photos, 4 line drawings by G. M. Sutton, one map. $2.50 ( Obtainable from Mrs. R. C.
Abbott, 8468 Peebles School Road, Pittsburgh, Pennsylvania 15237).

As a young boy the late W. E. Clyde Todd studied the birds on his grandfathers’ farms
and in their vicinity during the years 1889 to 1897, and in 1898 he prepared this account
of his observations, but never published it. In 1942 Mr. Todd had given the Audubon
Society of Western Pennsylvania some of the original farm property, which has been set
aside as a sanctuary. On the occasion of the thirtieth anniversary of the Todd Sanctuary
the Society has published this MS, with a biographical introduction, as well as annota-
tions about the present birdlife of the area by Mary H. Clench. The account gives a
valuable summary of the status of the birdlife of the region as it was 70-80 years ago.—
G.A.H.

Bird Census Surveys of the Hoopes Reservoir Area, New Castle County, Delaware.
By Lloyd L. Falk. Monograph No. 1, Delmarva Ornithological Society, 1971: 5% X
8V2 in., paper covered, 87 pp. $1.75 (Obtainable from the Delmarva Ornithological
Society, c/o Philip K. Klabunde, 2715 Bardell Drive, Wilmington, Delaware 19808).

This is a detailed summary of 158 bird census surveys conducted during 1943, 1944,
and 1945, compared with 52 surveys made in 1964. The two surveys show very graphically
the changes in birdlife over the 20-year period. — G.A.H.

' The Delmarva Ornithologist. The Delmarva Ornithological Society, Wilmington, Dcl-
; aware. Vol. 7, No. 1, January 1972.

A new regional publication intended to appear semiannually succeeding a mimeo-
graphed publication which appeared at irregular intervals. Obtainable from the Editor,
I Mrs. Francis H. Beach, P.O. Box 37, Northbrook, Pa. 19361. Single copies $1.00 each. —

! G.A.H.

PROCEEDINGS OF THE FIFTY-THIRD ANNUAL MEETING

James Tate, Jr., Secretary

At the invitation of the Delaware Valley Ornithological Club, the New Jersey Audubon
Society, and the Academy of Natural Sciences of Philadelphia, the Fifty-third Annual
Meeting of the Wilson Ornithological Society was held at Cape May, New Jersey, from
Thursday 15 June, through Sunday, 18 June 1972.

Early arrivals at Cape May were invited to a reception at the Wetlands Institute on
the causeway between Stone Harbor and the mainland on Thursday afternoon. The
Institute is about two miles from the Stone Harbor heronry, which many participants
visited on their return to Cape May. Thursday evening in the Convention Hall, William
E. Parker showed motion pictures which included birds photographed at the New Jersey
shore and at recent Wilson meetings.

On Friday evening Merrill Cottrell presented a well recieved slide show, “New Jersey’s
Natural Assets.” An impromptu showing of a new film “Everybody’s Eagle” was pre-
sented by its producer George Allez later Friday evening.

The annual banquet was held on Saturday evening at the Colonial Hotel. Following
the President’s Address, the group adjourned to the Convention Hall for a premier show-
ing of a new Audubon Wildlife Film, “Serengeti Safari” by Donald S. Heintzelman.

Throughout the meeting, paintings of North American waterfowl by William Zimmer-
man were on display in the Colonial Hotel.

Ornithologists visiting the Cape May peninsula were attracted to the famous breeding
colony of herons and Glossy Ibis at Stone Harbor, and the beach and salt meadowland
nesting colonies of gulls, plovers, terns, and skimmers. Early morning trips were held
Friday and Saturday to Cape May Point. Also scheduled during the meeting for those
not attending the paper sessions was a beach walk, a plant walk, and a walking tour of
historic Cape May. The Sunday boat trip was washed out by the advance rains of Hurri-
cane Agnes, but trips to the Brigantine National Wildlife Refuge and to the Osprey
colonies were held.

The recipients of the Wilson Society prizes were announced at the annual banquet
by First Vice-President Parkes as follows;

Louis Agassiz Fuertes Award: Donald E. Kroodsma, Oregon State University — Denies,
dialects, and dispersal in the Bewick’s Wren.

Margaret M. Nice Award: Mrs. Rebecca L. Radcliffe, Bloomfield Hills, Michigan —
Forty-year comparison study of nesting and migratory birds of Cranbrook Campus, Oak-
land County, Michigan.

Ernest P. Edivards Prize: First Prize, Mrs. Frances C. James, Fayetteville, Arkansas —
Ordinations of habitat relationships among breeding birds.

Second Prize, Anthony J. Erskine, Ottawa, Ontario — Some new perspectives on the
breeding ecology of Common Crackles.

Alexander Wilson Prize: W. Jon Richardson, Cornell University— Spring migration

over Puerto Rico: A radar study.

FIRST BUSINESS MEETING

The first business meeting was called to order by President Hofslund at 09:30. The
minutes of the business meetings held at Dauphin Island, Alabama, were approved by

362

September 1972
Vol. 84, No. 3

FIFTY-THIRD ANNUAL MEETING

363

the membership as published in The Wilson Bulletin (83:331-339, 1971). The President
appointed the following temporary committees:

Resolutions: Ernest P. Edwards, Chairman;

Alexander Wilson Prize: Douglas James, Chairman; Kenneth C. Parkes, Robert D.
Burns.

Auditing: C. Chandler Ross.

The names of the Nominating Committee members were announced as follows: Walter
J. Breckenridge, Chairman; John T. Emlen, Jr., 0. S. Pettingill, Jr.

The Secretary reported on highlights of the Council meeting of the previous evening.
Reports of officers of the society which were presented at the Council meeting were
summarized, and are reproduced here:

Report of the Treasurer — 1971

The Internal Revenue Service made an audit of the tax return for the year 1969 and
after reviewing our activities and examining the financial records, found we were in
compliance and continued our Federal tax-exempt status and accepted on March 24,
1972 the return as filed.

As the Society is exempt under 501(c) (3) and qualified favorably under Section
509(a) as “not a private foundation,” the filing of tax returns on the new Form 990
requires reporting in a manner that tests financial compliance each year and to some
extent for compliance with activities for which exemption was granted. In consequence,
any new activities contemplated need to be carefully evaluated for tax consequences and
the choice of words should be carefully weighed.

The value of Life Membership was dramatized this year in several resignations which
emphasized financial inability to continue many modest activities such as continuing
W.O.S. membership. This appeared to indicate fewer gifts probable, especially to the
Library, and offers to sell Wilson Bulletins were not uncommon.

FINANCIAL STATEMENTS

General Fund

Balance as shown by last report 31 December 1970 19,811.26

RECEIPTS

Membership Dues

Active for 1971 $ 5,965.00

Active for 1972 6,498.50

Total Active $12,463.50

Sustaining for 1971 540.00

Sustaining for 1972 375.00

Total Sustaining 915.00

Subscriptions to the Wilson Bulletin

For 1971 2,057.22

For 1972 2,955.38

Total Subscriptions 5,012.60

Sales of hack issues of The Wilson Bulletin 423.94

Interest and dividends on savings & investments 3,729.51

Royalties from microfilming hack issues of The Wilson Bulletin . 157.03

Total Receipts $22,701.58

364

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

DISBURSEMENTS

The Wilson Bulletin (Printing & Engraving) .... $15,394.95

Less contributions from authors 737.43

Printing & Engraving Expense $14,657.52

The Wilson Bulletin (Additional Mail & Service) 636.18

Editor’s Expense 220.01

Secretary’s Expense 83.90

Treasurer’s Expense 439.80

Foreign discount, bank charges and transfer fees 51.37

Annual Meeting Expense 658.00

Committee Expense 35.58

International Council for Bird Protection (1970-71 dues) .... 55.00

Transfer to Research and Other Grants 284.00

Review Editor’s Expense 28.38

Miscellaneous Expense 2.00

Total Disbursements $17,151.74

Excess of Receipts over Dislmrsements 5,549.84

GENERAL CASH FUND

Checking Account 10,416.09

Savings Account 4,945.01

Balance in National City Bank, Cleveland, Ohio 31 December 1971 . . . $15,361.10

JOSSELYN VAN TYNE MEMORIAL LIBRARY BOOK FUND

Balance as shown by last report 31 December 1970 171.23

RECEIPTS

Sale of duplicates and gifts 316.00

Total Balance and Receipts 487.23

DISBURSEMENTS

Purchase of Books 102.87

Balance in National City Bank, Cleveland, Ohio 31 December 1971 .... $ 384.36

LOUIS AGASSIZ FUERTES RESEARCH FUND, MARGARET MORSE NICE FUND,

EDWARDS, AND W.O.S. PAPER FUNDS

Balance as shown by last report dated 31 December 1970 $ 104.00

RECEIPTS

Contributions 232.00

Transfer from General Fund 284.00

Total 620.00

DISBURSEMENTS

Grant to Flash Gibson 200.00

Grant to William J. Maher 150.00

Grant to John P. Ryder 50.00

Grant to Kenneth P. Able 100.00

Grant to T. A. Beckett, 111 100.00

Total 600.00

Balance in National City Bank, Cleveland, Ohio 31 December 1971 .... $ 20.00

September 1972 FIFTY-THIRD ANNUAL MEETING 365

Vol. 84, No. 3

SPECIAL FUND ACCOUNTS

Balance as shown by last report 31 December 1970 $ 199.50

RECEIPTS

Prepaid Student Dues 0.00

Advanced Renewals 200.75

Discount Due Agencies 23.00

Total Receipts 223.75

Total 423.25

DISBURSEMENTS 80.50

Balance in National City Bank, Cleveland, Ohio 31 December 1971 . % 342.75

ENDOWMENT FUND

Balance in Endowment Fund Savings Account as shown by
last report dated 31 December 1970 $12,252.50

RECEIPTS

Life Membership Payments 4,985.00

Patronship Payments 750.00

Total Payments 5,735.00

Total $17,987.50

DISBURSEMENTS

For Investments 7,250.00

Balance in Endowment Fund Savings Account
National City Bank, Cleveland, Ohio 31 December 1971 $10,737.50

INVESTMENTS HELD AS OF 31 DECEMBER 1971

United States Government bonds 4,996.09

Canadian Provincial bonds 4,300.00

Corporate bonds 8,925.00

Convertible corporate bonds 3,462.50

Convertible preferred stock 38,804.50

Common stocks 17,186.25

Investment trusts 8,310.32

$85,984.66

Total Endowment Fund 31 December 1971 $96,722.16

Respectfully submitted,
William A. Klamm, Treasurer

Report of the Secretary — 1971

The Secretary of the Society answered a small amount of correspondence, forwarded
several items to the Treasurer, and had the Society’s stationery and envelopes printed and
distributed. Utilizing volunteers the committee choices of the (luestionnaire respondents
were tabulated on 3 X 5 index cards for the convenience of the President as he contacted
committee chairmen. These were delivered to him in two portions.

366

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

A letter summarizing the duties of the Secretary was received from retiring Secretary
Swinebroad which proved to be of great help. The Guide to the Local Committee in
Charge of the Annual Meeting was sent at the same time. This was revised and updated.
Copies were sent to the local committee. Events of the year rendered it partially
ineffective.

President Hofslund appointed Elden W. Martin as Program Chairman in the antic-
ipated absence of Second Vice-President Berger. With his help, and that of the local
committee, the Secretary prepared, edited, and printed the announcement of the meeting.
The announcement was mailed in late April. The program was printed and carried to
the meeting by the Secretary.

From the Secretary’s viewpoint it was an interesting, informative, and occasionally
frustrating year. It was a pleasure to be of service to the Society. — James Tate, Jr.,
Secretary

Editors Report — 1971

Volume 83 (1971) consisted of 468 pages and included 34 papers, 45 Notes, 26 book
reviews, one conservation paper, and the index. There were two colored plates, both
of which had outside subsidy.

Two issues of Volume 84 have appeared totalling 228 pages.

During the past year 59 papers and 82 Notes have been submitted, and 27 papers
and 48 Notes have been accepted. Fourteen papers and six Notes have been returned
to the authors for substantial change before acceptance; 14 papers and 25 Notes have
been rejected; and no decision has been reached on 8 papers and 3 Notes.

The current backlog of papers is a very comfortable one. The September issue is
being set in type, and there is not quite enough material accepted as yet for the December
issue. This issue should be filled shortly with the return of some papers for which change
had been suggested. Thus the publication delay on some papers can be as short as six
months, and on most no longer than one year. The average delay for papers in the June
issue was 10 months, excluding one paper for which the author delayed six months in
making revisions. The average delay for Notes was 9 months.

The members of the Editorial Board have continued in their excellent service, and
once again I extend my thanks to them, and to the many other ornithologists who reviewed
papers during the year. — George A. Hall, Editor

Reports of several of the committees which reported to the Council Meeting were then
summarized, and are reproduced here:

Report of the Research Committee — 1971

Your committee unanimously recommends that the Fuertes Award go to Donald E.
Kroodsma, Department of Zoology, Oregon State University. The title of his research
project is “Denies, dialects, and dispersal in the Bewick’s Wren.” Mr. Kroodsma was
ranked well ahead of his closest competitors. In the committee’s voting there was a tie
for second place.

Thirteen people completed the application process, i.e., did more than write letters
of inquiry or request forms. One of these later withdrew his name when he received other
support. In addition to these thirteen, an approximately equal number of people wrote
letters indicating an interest in applying.

For the Nice Award the committee recommends Rebecca L. Radcliffe, c/o Cranbrook
Institute of Science, P.O. Box 801, Bloomfield Hills, Michigan 48013. Mrs. Radcliffe, who

September 1972
Vol. 84, No. 3

FIFTY-THIRD ANNUAL MEETING

367

was the sole applicant having no affiliation with an academic institution (her husband
is employed by the Cranbrook Institute, but not as a scientist), is working on a project
entitled “A forty-year comparison study of nesting and migratory birds of Cranbrook
Campus, Oakland County, Michigan.”

It seems worth calling attention to the paucity of applicants for the Nice Award and
suggesting that the Society take measures to encourage interest in it. This year, as in
the past, applications for both the Fuertes and the Nice Awards were solicited only by
means of repeated announcements in the major United States ornithological journals.
It is possible that even amateurs who are serious enough to have research projects may
not see these announcements. Perhaps the Bird Banding Laboratory at Patuxent might
be asked to give publicity to the Nice Award. — Val Nolan, Jr., Chairman

Report of the Membership Committee— 1971

Even though I agreed in mid-summer to President Hofslund’s request that I serve as
chairman of the membership committee, I was unable to begin work on the membership
drive until early October. My first efforts were directed toward increasing the number
of committee members and the geographic representation on the committee. I contacted
over thirty WOS members who had indicated a willingness to help with membership
recruitment on the questionnaire circulated a couple of years ago. This resulted in the
membership committee increasing from 14 to 41 members and increased our geographic
representation from 13 states to 24 states and one Canadian Province.

In mid-January I sent each committee member a packet containing a two-page letter
suggesting some possible techniques for recruitment, ten each of brochures and member-
ship application cards, and an average of five names of prospective members gleaned
from the AOU membership list. Since January, several committee members have requested
a total of over 100 additional brochures and cards. Thus, assuming that most committee
members contacted at least the number of names given them, a minimum of around 200
persons were approached about membership. If a substantial number of the members
also turned up contacts on their own, this number could be as high as 400.

As of 6 June, I have received the cards of 104 new members from the Treasurer (list
attached). Of this total, 36 were nominated by Treasurer Klamm, and 39 others were
nominated by a total of 28 WOS members not serving on the membership committee.
Unless some of the applicants whose cards were signed by the Treasurer were recruited
by committee members, it appears that the committee has been responsible for the pro-
duction of only 29 new members. While this number is embarrassingly low, particularly
in view of the increased size of the committee, I do not know whether or not it is unusual.
The recent annual reports of this committee have not reported the number of members
recommended by committee members.

The 104 new members represents an increase of 7 over the number of new members
reported in last year’s annual report. However, we have lost 28 members from resigna-
tion, 9 from deaths, and 88 have been suspended for being delinquent in dues, for a total
loss of 125. Thus, it appears at this time as though our total member.diip is down 21
from last year. The only encouraging aspect of this figure is that la.«t year's decrease in
membership, based on figures in the 1971 report, was 84. Treasurer Klamm also reports
that we have 3 new life members and 2 new patrons. — NoitMAN L. Ford, Chairman

Report of the Student Membership Committee — 1971

After an initial special mailing in 1970 to all 429 WOS members at institutions of
higher learning the Student Membership Committee has since then relied on colh'ge

368

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

student nominations in response to a notice in the December Wilson Bulletin. The notice
has been a complete failure. There were only two responses totaling two nominations in
1971, and so far in 1972 the two nominations received came from a single person. This
compares to 55 responses providing 188 nominations and yielding 40 new members fol-
lowing the massive mailing in 1970. So it is apparent that a simple journal notice is
ineffective. Instead an actual nomination form has to reach the membership. We sug-
gest the possibility be explored of including such a form in the annual mailing for mem-
bership renewal since a special separate mailing to our members yearly is expensive.
This approach could seek non-student as well as student nominees for membership.

In 1971 and again this year the Committee mailed letters to nature centers, municipal
museums, Audubon Societies and the like in an attempt to find talented pre-college stu-
dents with a keen interest in bird study to invite them to join the Wilson Ornithological
Society at an early age. This quest is being conducted on a regional basis progressively
covering the nation in successive years. In 1971 some 102 mailings to 10 northeastern
states produced 11 responses and 27 nominees. This year 124 letters were posted in May
to 13 states, mostly in the upper Midwest but extending to Virginia, and so far there
have been four responses including 10 nominees.

The Committee will continue the pre-college search on a continuing regional basis,
but it also feels it now is time to make a direct appeal to the college student again. We
strongly recommend testing the procedure that provides nomination forms sent to mem-
bers with the annual dues request. — Douglas A. James, Chairman

Report of the Library Committee — 1971

The year has been relatively uneventful for the library but, on the whole, successful.
The collection continues to grow.

Thirty-one gifts were received from 23 donors: 13 books, 81 periodicals and 300

reprints, in all.

Fifty-one loans were made by mail to 45 members; and, as always, the library had
constant on-the-spot use.

Both the foregoing items represent an increase over last year.

The library receives 98 journals in exchange for The Wilson Bulletin.

An effort is being made to dispose of a rather large accumulation of duplicates. Success
in this area is already considerably augmenting our New Book Fund, which will make
possible the purchase of books still badly needed.

Our space problem may soon again become acute, where storage of back issues of
the “Bulletin” is concerned. However, it is hoped that solutions will once more be found.

As always, members are invited to borrow, and also urged to contribute in any way
possible. — William A. Lunk, Chairman

Continuing the summary of the Council meeting. Secretary Tate reported on the ap-
pointment of the Editor. The Council voted on the appointment of the Editor of The
Wilson Bulletin, and selected George A. Hall. Editor Hall accepted the appointment,
commenting that he would begin his tenth consecutive year with Volume 85 of The
Wilson Bulletin. He reported that he would tender his resignation upon the completion
of that Volume year.

The fifty-fourth annual meeting of the Society will be held at Chapel Hill, North
Carolina from 17-20 May 1973.

There being no further business, the President closed the first business meeting at
09:47.

September 1972
Vol. 84, No. 3

FIFTY-THIRD ANNUAL MEETING

369

SECOND BUSINESS MEETING

President Hofslund opened the second business meeting at 14:20 on Saturday. The
following resolution was read by Ernest P. Edwards:

WHEREAS, the Wilson Ornithological Society met in its Fifty-third Annual Meeting
at Cape May, New Jersey, one of the famous ornithological sites of the east coast, and

WHEREAS, lodgings were provided and numerous special events were planned and
offered, in addition to the papers sessions and business sessions,

THEREFORE, BE IT RESOLVED THAT the Society express its warmest appreciation
for the hospitality of the City of Cape May, the Delaware Valley Ornithological Club,
the New Jersey Audubon Society, and the Academy of Natural Sciences of Philadelphia,
and particularly of the Local Committee on Arrangements who took care of the necessary
arrangements to make the meeting possible.

The resolution was approved by the members in attendance.

Report of the Auditing Committee

We have examined the accounts of the Wilson Ornithological Society for the year 1971
and find everything in good order. We therefore approve the treasurer’s report sub-
mitted by William A. Klamm.

We suggest that in the future the chairman of the Local Committee for any annual
meeting be instructed to send all fees for attending the meeting to the treasurer and that
the Local Committee be reimbursed for any expenses which it incurs, in our behalf, by the
treasurer. — C. Chandler Ross, Chairman.

Proposed new members of the Wilson Ornithological Society were elected as posted.

The report of the Nominating Committee was presented by the Secretary in the absence
of any member of the committee. The nominations were as follows: Pershing B.

Hofslund, President; Kenneth C. Parkes, First Vice-President; Andrew J. Berger, Second
Vice-President; James Tate, Jr., Secretary; William A. Klamm, Treasurer; Harvey I.
Fisher, Elected Member of the Council.

There were no further nominations, and a motion was made and seconded to close
the nominations. The motion passed. A motion was made, seconded and passed that the
Secretary be instructed to cast a unanimous ballot for the slate proposed by the Nomi-
nating Committee.

The President closed the Second Business Meeting at 14:40.

PAPERS SESSIONS

Jay M. Sheppard, California State College, Long Beach, Movements of Color-marked
LeConte’s Thrashers (Toxostoma lecontei).

W. Jon Richardson, Cornell University, Spring Migration over Puerto Rico: A Radar
Study.

Robert C. Reason, U.S. Air Force, Kirtland AFB, New Mexico, Aspects of Precision
Radar in Monitoring Bird Behavior.

Deborah V. Howard, Massachusetts Audubon Society, Fall Migration of Black-capped
Chickadees at Manomet Bird Observatory.

Daniel D. Berger, Cedar Crove Ornithological Station, The Fall Migration of Sharp-
shinned Hawks Through the It estern Great Lakes Region.

370

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Kenneth A. Youngstrom, Manomet Bird Observatory, Applied Bird Banding: The Use of
Banding to Facilitate Radiological Studies of Avifauna.

William S. Clark, 7800 Dassett Court, Annandale, Va., Cape May Point Raptor Banding
Station.

Charles F. Leek, Rutgers University, The Expansion of the Monk Parakeet in New Jersey.

Ralph E. Babcock, Western Michigan University, Range Expansion of the Cardinal, Part
II, Great Lakes States.

Brian Sharp, Bird Banding Laboratory, Laurel, Md., The Status of the Dusky Seaside
Sparrow (Amniospiza nigrescens) .

Mary Heimerdinger Clench, Carnegie Museum, Fall Migration Records of Kirtland’s
W arbler; The First Documented State Record for Pennsylvania.

Frank B. Gill, F. J. Stokes, and C. C. Stokes, Academy of Natural Sciences of Philadel-
phia, Contact Zones and Hybridization in the Jamaican Hummingbird, Trochilus
polytmus (L.)

Jon S. Greenlaw, C. W. Post College, Habitat Differences in Territory Size and Clutch-size
of the Rufous-sided Towhee in Relation to Food Supply.

Roland R. Roth, University of Delaware, A Case of Interspecific Aggression: Misdirected
or Adaptive?

Ernest A. Choate, Delaware Valley Ornithological Club, Academy of Natural Sciences of
Philadelphia, American Bird Names.

William J. Francis, Patuxent Wildlife Research Center, Reproductive Phenology of
Blackbirds in Upland Nesting Habitat.

Fred J. Alsop, III, University of Tennessee, A Comparison of Eggshell Thickness in
Contemporary Populations of the Red-winged Blackbird (Agelaius phoeniceus) with
Populations Predating DDT.

Elden W. Martin, Bowling Green State University, Sensitivity of Starlings to Sulfur
Dioxide as an Experimental Air Pollutant.

George B. Reynard, Cornell Laboratory of Ornithology, A New Collapsible Parabolic
Reflector Convenient for Overseas Travel.

Paul Spitzer, Cornell University, Reproductive Failure of the Osprey in Southern New
Jersey.

Jerome A. Jackson, Mississippi State University, Behavior of Nestling W oodpeckers.

L. Irby Davis, 2503 Keating Lane, Austin, Texas, Acoustic Evidence of Relationship in
North American Potoos.

Stephen I. Rothstein, Chesapeake Bay Center, Smithsonian Institution, Egg Recognition
in North American Passerines and its Relation to Cowbird Parasitism.

Helmut C. Mueller, University of North Carolina, The Role of the Specific Searching
Image and Oddity in Prey Selection.

Daniel S. McGeen, Oakland University, The Kirtland’s Warbler — Cowbird Interaction.

ATTENDANCE

One hundred ninety members and guests were registered. Thirty states, the District

of Columbia, two Canadian provinces, Germany, and Mexico were represented.

From ARKANSAS: 1 — Fayetteville, Douglas James.

From COLORADO: 1 — Fort Collins, Gustav A. Swanson.

From CONNECTICUT: 1 — Storrs, George A. Clark, Jr.

From DELAWARE: 6 — Newark, Roland R. Roth; Wilmington, Charles R. Conway, Mr.
and Mrs. Albert E. Conway, Mr. and Mrs. Rodman Ward.

September 1972
Vol. 84, No. 3

FIFTY-THIRD ANNUAL MEETING

371

From DISTRICT OF COLUMBIA: 2 — Richard C. Banks, Paul W. Woodward.

From FLORIDA: 1 — Winter Park, Marjory Bartlett Sanger.

From HAWAII: I — Honolulu, Andrew J. Berger.

From INDIANA: 1 — Dillsboro, William Zimmerman.

From IOWA: 2 — Davenport, Mr. and Mrs. Peter C. Petersen.

From KENTUCKY: 2 — Danville, Mr. and Mrs. Frederick W. Loetscher, Jr.

From MAINE: 2 — Orono, Mr. and Mrs. Edward J. Danforth.

From MARYLAND: 12 — Adelphi, Brian Sharp; Baltimore, Richard D. Porter, C. John
Ralph, Robert Wood; Chestertown, Mr. and Mrs. Edward Mendinhall, Mrs. James
Plymire; Columbia, Charles J. Henry; Edgewater, Stephen Rothstein; Gaithers-
burg, Jeff Swinebroad; Laurel, Jay M. Sheppard; Towson, Gladys Cole.

From MASSACHUSETTS: 5 — Manomet, Kathleen S. Anderson; Petersham, John and
Rosalie Fiske; Sherborn, Richard T. Darby; West Newton, Deborah V. Howard.
From MICHIGAN: II — Alma, Lester and Alma Eyer; Ann Arbor, Robert W. Storer
(4) ; Bronson, Mr. and Mrs. Ralph E. Babcock; Detroit, Vivian Telford Anderson;
Pontiac, Mr. and Mrs. Daniel S. McGeen.

From MINNESOTA: I— Duluth, P. B. Hofslund.

From MISSISSIPPI: 5 — State College, Mrs. W. L. Croft, Jerome A. Jackson (3), Miss
Martha Ward.

From NEW HAMPSHIRE: 1 — New Hampton, Robert W. Smart.

From NEW JERSEY: 35 — Audubon, Clarence E. Stasz, James L. Stasz; Blackwood,
James K. Merritt; Bound Brook, Robert C. Conn; Cape May Point, E. A. Choate;
Cranbury, Bruce Adams; Cranford, Farris S. Swackhamer, Louise W. Swackhamer;
Delmont, C. Brooke Worth; Linwood, Mr. and Mrs. William E. Saveli; Mt. Holly,
Katherine Price; New Brunswick, Charles F. Leek, Bertram G. Murray, Jr.;
Pennsauken, Joseph Jacobs; Piscataway, John Kenny; Princeton, Miss Dorothy
M. Compton, Charlotte A. DuBois, Mr. and Mrs. Charles H. Rogers; Riverton,
George B. Reynard; Rocky Hill, Mr. and Mrs. Charles D. Allen; Stone Harbor,
Herbert Mills, Miss Glosopy, Mark A. Pokras, Francis J. Singer; Lena fly, Mr. and
Mrs. Dean Amadon; Trenton, Donald S. Heintzelman; Turnersville, James K.
Meritt; Verona, Mr. and Mrs. Alfred E. Eynon; W enonah, E. R. Manners, W. R.
Middleton.

From NEW MEXICO: I — Albuquerque, Robert C. Beason.

From NEW YORK: 19— Buffalo, Mr. and Mrs. Harold H. Axtell; Dix Hills, Jon S.
Greenlaw; Ithaca, W. John Richardson, James Tate, Jr., D. Jean Tate; Jamaica,
Frederick S. Schaeffer; Lake Luzerne, Elizabeth R. Thomas, Lester S. Thomas;
Long Island City, Mr. and Mrs. Julius J. Keil; Mamaroneck, Robert S. Arbil), Jr.;
New York, G. Stuart Keith, Helen S. Lapham, Lester Short, Doug Vageler; Owego,
Ruth Williams; Rye, Devin A. Garrity; Staatsburg, Erik Kiviat.

From NORTH CAROLINA: 5 — Chapel Hill, Helmut C. Mueller; Montreal, Mrs. Ira 1).

Holt, Miss Jane P. Holt; Raleigh, Thomas L. Quay, Vi Quay.

From OHIO: 15 — Ashtabula, Howard E. Blakeslee; Bowling Green, Elden W. Martin;
Burton, Robert McCullough; Cleveland, Ethel 1). Surnian; Columbus, Mrs. Vera
Auten, Mr. and Mrs. Milton B. Trautman; Gambier, Robert 1). Burns; East Liver-
pool, Mr. and Mrs. John Laitsh; Lakewood, William A. Klamm; Sandusky, W illiam
J. Francis; Steubenville, Mr. and Mrs. Clinton S. Banks; Toledo, J. M. \b-Corinick.
From PENNSYLVANIA: 24 — Butler, W. Preston; Chester Springs, Mr. and Mrs.

Phillips B. Street; Elizabethtown, Mr. and Mrs. Robert S. K(*nned\ ; Elourtown,
Mr. and Mrs. G(‘ne Stern; Jenkintown, Brad Gottfri(‘d; Media, Keith C. Hicliards;

372

THE WILSON BULLETIN

September 1972
Vol. 84, No. 3

Northbrook, Mrs. Frances H. Beach; Philadelphia, Frank B. Gill, Mr. and Mrs.
Jeddu Keil, C. Chandler Ross, Robert H. Sehl, Mr. and Mrs. F. Joseph Stokes,
Jr.; Pittsburgh, Mary H. Clench, Kenneth C. Parkes; State College, Dorothy L.
Bordner; Trout Run, Mr. and Mrs. Walter K. Bigger; Strafford, Mr. and Mrs.
Robert A. Livingston.

From SOUTH CAROLINA: 6 — Chester, Mrs. Walker M. Atkinson, Mrs. B. Clyde

Carter, James W. Crowder, Mrs. Catherine T. Moore, Mrs. W. C. Stone, Sr.;
McClellanville, James B. Shuler.

Form TENNESSEE: 2 — Knoxville, Fred J. Alsop, III; Maryville, Ralph J. Zaenglein.
From TEXAS: 2 — Austin, Mr. and Mrs. L. Irby Davis.

From VERMONT: 1 — South Londonderry, Mrs. James R. Downs.

From VIRGINIA: 7 — Annandale, William S. Clark; Arlington, Mrs. Herbert M. Church,
Jr.; Manassas, Mrs. Roxie C. Laybourne; Portsmouth, Gilbert S. Grant; Rich-
mond, Charles R. Blem; Sweet Briar, Mr. and Mrs. Ernest P. Edwards.

From WASHINGTON: Seattle, Karl W. Kenyon.

From WEST VIRGINIA: 7 — Inwood, Clark Miller; Morgantown, Mr. and Mrs. Maurice
Brooks, Mr. and Mrs. George A. Hall, Larry T. Schwab, Martha Schwab.

From WISCONSIN: 3 — Cedar Grove, Daniel D. Berger; Plainfield, Frances Hamerstrom,
Frederick Hamerstrom.

From GERMANY: 1 — Carlsruhe, Ulrich Querner.

From MEXICO: 1 — San Miguel Allende, Mrs. Lillian R. Birkenstein.

From ONTARIO: 3 — Hamilton, Eric W. Bastin, Parry Sound, Mr. and Mrs. J. W.
Robinson.

From QUEBEC: 2 — Westmount, Mr. and Mrs. G. H. Montgomery.

This issue of The W ilson Bulletin was published on 29 September 1972.

Editor of The Wilson Bulletin
GEORGE A. HALL
Department of Chemistry
West Virginia University
Morgantown, West Virginia 26506

Editorial Advisory Board

William C. Dilger
Douglas A. James
William A. Lunk
Andrew J. Meyerriecks

Helmut C. Mueller
Robert W. Nero
Kenneth C. Parkes
Glen E. Woolfenden

Ornithological Literature Editor
Peter Stettenheim

Box 79, Plainfield, New Hampshire 03781

Suggestions to Authors

Manuscripts intended for publication in The Wilson Bulletin should be neatly type-
written, double-spaced, with at least one inch margins, and on one side only of good quality
white paper. Tables should be typed on separate sheets, and should be designed to fit
the normal page width, i.e., narrow and deep rather than wide and shallow. Before pre-
paring these, carefully consider whether the material is best presented in tabular form.
Follow the AOU Check-list (Fifth Edition, 1957) insofar as scientific names of United
States and Canadian birds are concerned unless a satisfactory explanation is offered for
doing otherwise. Use species names (binomials) unless specimens have actually been
handled and subsequently identified. Summaries of major papers should be brief but
quotable. Where fewer than five papers are cited, the citations may be included in the text.
All citations in “General Notes” should be included in the text. Follow carefully the style
used in this issue in listing the literature cited; otherwise, follow the “Style Manual
for Biological Journals” (1964. AIBS). Photographs for illustrations should be sharp,
have good contrast, and be on gloss paper. Submit prints unmounted and attach to
each a brief but adequate legend. Do not write heavily on the backs of photographs.
Diagrams and line drawings should be in black ink and their lettering large enough to
permit reduction. Authors are requested to return proof promptly. Extensive alterations
in copy after the type has been set must be charged to the author.

Notice of Change of Address

If your address changes, notify the Society immediately. Send your complete new
address to the Treasurer, William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.
He will notify the printer.

The permanent mailing address of the Wilson Ornithological Society is: c/o The
MUSEUM of Zoology, The University of Michigan, Ann Arbor, Michigan 48104. Persons
having business with any of the officers may address them at their various addresses
given on the back of the front cover, and all matters pertaining to the Bulletin should be
sent directly to the Editor.

Plan Now to Attend the

FIFTY-FOURTH ANNUAL MEETING

at

CHAPEL HILL, NORTH CAROLINA

17-20 May 1973

TIieWlsotiBulletia

PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY
WEST VIRGINIA U. • MORGANTOWN, W. VA.

VOL. 84, NO. 4 DECEMBER 1972 PAGES 373-533

The Wilson Ornithological Society
Founded December 3, 1888

Named after ALEXANDER WILSON, the first American Ornithologist.

President — Pershing B. Hofslund, Dept, of Biology, University of Minnesota Duluth,
Duluth, Minnesota 55812.

First Vice-President — Kenneth C. Parkes, Carnegie Museum, Pittsburgh, Pennsylvania
15213.

Second Vice-President — Andrew J. Berger, Dept, of Zoology, University of Hawaii,
Honolulu, Hawaii 96822.

Secretary — James Tate, Jr., Laboratory of Ornithology, Cornell University, Ithaca, New
York 14850.

Treasurer — William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.

Elected Council Members — Elden W. Martin (term expires 1973) ; Robert D. Burns (term
expires 1974) ; Harvey I. Fisher (term expires 1975) .

Membership dues per calendar year are: Active, $8.00; Sustaining, $15.00;

Life memberships, $200 (payable in four installments).

The Wilson Bulletin is sent to all members not in arrears for dues.

The Josselyn Van Tyne Memorial Library
The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed
in the University of Michigan Museum of Zoology, was established in concurrence with
the University of Michigan in 1930. Until 1947 the Library was maintained entirely
by gifts and bequests of books, reprints, and ornithological magazines from members
and friends of the Society. Now two members have generously established a fund for
the purchase of new books; members and friends are invited to maintain the fund by
regular contribution, thus making available to all Society members the more important
new books on ornithology and related subjects. The fund will be administered by the
Library Committee, which will be happy to receive suggestions on the choice of new books
to be added to the Library. William A. Lunk, University Museums, University of Michi-
gan, is Chairman of the Committee. The Library currently receives 104 periodicals as gifts
and in exchange for The Wilson Bulletin. With the usual exception of rare books, any
item in the Library may be borrowed by members of the Society and will be sent prepaid
(by the University of Michigan) to any address in the United States, its possessions, or
Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers,
as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to
“The Josselyn Van Tyne Memorial Library, University of Michigan Museum of Zoology,
Ann Arbor, Michigan.” Contributions to the New Book Fund should be sent to the
Treasurer (small sums in stamps are acceptable). A complete index of the Library’s
holdings was printed in the September 1952 issue of The Wilson Bulletin and newly
acquired books are listed periodically.

The Wilson Bulletin

The official organ of the Wilson Ornithological Society, published quarterly, in March, June, September,
and December, at Morgantown, West Virginia. The subscription price, both in the United States and elsewhere,
is $10.00 per year. Single copies, $2.50. Subscriptions, changes of address and claims for undelivered
copies should be sent to the Treasurer. Most back issues of the Bulletin are available (at $2.50
each) and may be ordered from the Treasurer. Special prices will be quoted for quantity orders.

All articles and communications for publications, books and publications for reviews should be addressed to
the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology,
Ann Arbor, Michigan.

Second class postage at Lawrence, Kansas, U.S.A. 66044

Allen Press, Inc., Lawrence, Kansas 66044

THE WILSON BULLETIN

A QUARTERLY MAGAZINE OF ORNITHOLOGY

Published by The Wilson Ornithological Society

VoL. 84, No. 4 December 1972 Pages 373-533

CONTENTS

The Subspecies of the Red-headed Parrot-Finch

Painting by George Sandstrom facing page 375

Notes from Western Samoa, Including the Description of a New

Parrot-Finch (Erythrura) John E. duPont 375

The Behavior of Plain-brown Woodcreepers, Dendrocincla fuligi-

nosa Edwin O. Willis 377

Red-tailed Hawk Populations and Ecology in East-central Wis-
consin John M. Gates 421

Predator-Prey Relationships and Reproduction of the Barn Owl
IN Southern Texas

Lee C. Otteni, Eric G. Bolen, and Clarence Cottam 434

Seed Size Preference in Finches Mary F. Willson 449

Nestling Development of Boat-billed Herons {Cochlearius coch-
learius) at San Blas, Nayarit, Mexico

Carlos Juarez L. and Robert W. Dickerman 456

Eggshell Thickness and Its Variation in the Cedar Waxwing

Stephen I. Rothstein 469

Vernal Testes Development in Tropical-wintering Dickcissels

John L. Zimmerman and James V. Morrison 475

General Notes

TOOL-USING BY A DOUBLE-CHESTED coKMOHANT Andrew J. Meycrriecks 482

COLD HARDINESS AND THE DEVELOPMENT OF HOMEOTHEHMY IN YOUNG BLACK-BELLIED

TREE DUCKS - — Brian Cain 484

RUDDY DUCKS COLLIDING WITH WIRES — - Jf . Boy Sief’fried 186

A NOTE ON GOLDEN EAGLE TALON WOUNDS Jo/w R. Alford, III and Erie G. Bolen 487

ROADSIDE RAPTOR CENSUS IN COLORADO — WINTER 1971-72

David Johnson and James H. Enderson 489

SPARROW HAWK EATS EUROPEAN CORN BORER

Clive A. Petrovic and Gregory S. Mills 491

BLACK RAILS HIT A TELEVISION TOWER AT RALEIGH, NORTH CAROLINA

Micoii M. Browne and William Post 491

EGGSHELL REMOVAL IN THE SPOTTED SANDPIPER Edward H. Burtt, Jr. 492

STOMACH CAPACITY IN THE COMMON NiGHTHAwK Charles R. Blem 492

RETENTION OF EGG IN A WILD DOWNY WOODPECKER Lawrence KUham 493

THE USE OF SAWDUST PILES BY NESTING BANK SWALLOWS J on S. Greenlaw 494

ADDITIONAL VERTEBRATE PREY OF THE LOGGERHEAD SHRIKE

Brian R. Chapman and Stanley D. Casto 496

COWBIRD PARASITISM OF WESTERN KINGBIRD AND BALTIMORE ORIOLE NESTS

Thomas S. Smith 497

OBSERVATIONS OF BIRDS AT CECROPIA TREES IN PUERTO RICO Charles F. Leck 498

Ornithological News 501

Ornithological Literature 503

George Miksch Sutton, High Arctic, An Expedition to the Unspoiled North,
reviewed by William J. Maher; G. E. Watson, J. P. Angle, P. C. Harper, M. A.
Bridge, R. P. Schlatter, W. L. N. Tickell, J. C. Boyd, and M. M. Boyd, Birds of
the Antarctic and Subantarctic, reviewed by Robert Cushman Murphy; Austin
L. Rand, Birds of North America, reviewed by Sally Hoyt Spofford, Charles
Vaurie, Classification of the Ovenbirds ( F urnariidae ) , reviewed by Peter L.
Ames; Stuart Keith and William W. H. Gunn, Birds of the African Rain Forests,
reviewed by Dale A. Zimmerman ; Russ Williams, The Ways of Wildfowl. Repro-
ductions of Etchings and Paintings by Richard E. Bishop, reviewed by Miles D.
Pirnie; Elizabeth Barlow, The Forests and Wetlands of New York City, reviewed
by John Bull; Richard D, Teague (Ed.), A Manual of Wildlife Conservation,

reviewed by Oliver H. Hewitt.

Publication Notes and Notices 511

Suggestions to Authors 513

The Wilson Ornithological Society, Officers and Committee

Chairmen 514

Index to Volume 84, 1972 Emma J. Messerly and John F. Messerly 515

The subspecies of the Red-headed Parrot-Finch: (A) Erythrvra cyaneovirens cycneov/rens,
(B) E. c. gaughrani, (C) £. c. pealii, (D) E. c. regia, (E) E. c. serene.

Painting by George Sandstrom.

NOTES FROM WESTERN SAMOA, INCLUDING
THE DESCRIPTION OF A NEW PARROT-
FINCH {ERYTHRURA)

John E. duPont

IN 1970 the Delaware Museum of Natural History sent a field party to Savaii,
Western Samoa, to carry out ornithological research, including recording
the voices of some of the endemic species. The visit was made during the
first three weeks of September by me and Dr. and Mrs. James Gaughran.
We visited both the islands of Upolu and Savaii, concentrating on the latter,
where we spent two weeks and ranged from sea level to the mountain tops
(elevation 5,000 feet). One new subspecies was discovered, and records were
obtained for three species new to Western Samoa.

I wish to thank Dr. Dean Amadon of the American Museum of Natural
History and Dr. David Snow of the British Museum (Natural History ) for
lending specimens and assisting in other ways. Common names used are
those suggested by Mayr (Birds of the Southwest Pacific, Macmillan Co., New
York, 1945).

Peregrine {Falco peregrinus) . — One adult bird seen on two occasions three miles inland
from Lalomalava. Peregrines occur at least sporadically in Fiji (Viti Levu), some 750
miles WSW of Savaii, and may breed there (race nesiotes) (Mayr, op. cit.). Otherwise
the species is virtually unknown in the Central Pacific.

Not previously recorded from Western Samoa.

Rock Dove {Columba livia) . — A total of about 20 birds was seen on Savaii on two
occasions, once at Lalomalava, and once at Satuiatua. The birds did not seem to stray
far from the native huts and were not seen around large buildings in towns. Undoubtedly
these were domesticated birds, but all were of the wild plumage type, i.e. gray coloration.
The species may be expected to spread into other areas as a feral bird, but probably in
settled areas only, as few cliffs are available in the wild.

Not previously recorded from Western Samoa.

Tooth-billed Pigeon (Didunculus strigirostris) . — Found in virgin forest from 1,000 feet
to 4,500 feet, where most often seen sitting on large limhs near tree trunk and not on
the ground as has been generally recorded. Voice a slow hoo, hoo, hoo, low-pitched and
infrequently heard.

This species is in no immediate danger of extinction so long as the forests remain intact.
The bird was seen in original forests, sometimes quite near towns, but not in cut-over
areas anywhere.

Red-vented Bulbul (Pycnonotus cafer benga/ensis) . — 1 adult $ specimen was taken
6 September 1970, at Lalomalava. Birds seen in Apia. Upolu, and around Lalomalava,
Savaii. These birds were numerous in Apia, but in Lalomalava only small numbers were
seen. This species was undoubtedly introduced into Samoa, perhaps directly from India,
but more likely from the introduced po|)ulation of Fiji.

Not previously recorded from Western Samoa.

Samoan Starling i Aplonis atrijusca) . — This bird was (mcoiintered in small to moderate

375

376

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

numbers from the sea coast to the mountain tops. Nests, heretofore unknown, were found
on two separate occasions about 40-50 feet up in cracks in old, dead trees, one in a limb
and one in a trunk. A female carrying nest material was collected on 12 September 1970,
at Lalomalava, Savaii. Soft part colors of four adults are; bill black, iris dark brown,
feet black.

Red-headed Parrot-Finch ( Erythrura cyaneovirens) — This colorful parrot-finch of the
Central Pacific is separable into five subspecies, the nominate race being from Upolu,
Western Samoa. Although some years ago Mayr (Amer. Mus. Novitates, 489:7, 1931)
pointed out the Savaii population might be separable, only recently has material been
collected that proves this suggestion to be valid. The Savaii race may be called:

Erythrura cyaneoviretts gaughrani new subspecies

Type: DMNH 4868, male, Mt. ’O’a, Savaii, Western Samoa, 5,000 feet, 8 September
1970. Wing 64 mm, tail 32 mm, bill 13 mm, tarsus 18 mm.

Diagnosis: Male differs from E. c. cyaneovirens of Upolu by having the red on the head
and tail decidedly darker; blue on the nape paler and less extensive; back green, lacking
any blue; chin and throat green with a less extensive and paler blue wash; underparts
green with only a slight trace of a blue wash; wing coverts greener lacking any of bluish
edgings. Immatures from Savaii mirror the characters of the male by being green with
very little blue. Adult female unknown.

Range: Savaii, Western Samoa.

Specimens examined: E. c. cyaneovirens — Upolu, 4 (J , 1 $ , 1 ? ; E. c. gaughrani —
Savaii, 1 $ (Type), 2 imm. $, 4 imm. $, 2 imm. ?.

Etymology: This new subspecies is named for Dr. James Gaughran of Stanford Uni-
versity.

The other races that I recognize of the species are:

Erythrura cyaneovirens pealii. — Geospiza prasina Peale, 1848, U.S. Expl. Expd. Bds.,
p. 116 (Vanua Levu, Fiji). Erythrura pealii Hartlaub, 1852, Arch. F. Naturg., p. 104
(new name for Geospiza prasina Peale, 1848). Range: Fiji Islands.

Erythrura cyaneovirens regia. — Erythrospiza regia Sclater, 1881, Ibis, p. 554 (Api rr
Epi Island, New Hebrides). Range: Bank Islands and northern New Hebrides.

Erythrura cyaneovirens serena. — Erythrospiza serena Sclater, 1881, Ibis, p. 544 (Aneiteum
Island, New Hebrides). Erythrura cyaneovirens efatensis Mayr, 1931, Am. Mus. Novitates,
489:8 (Efate Island, New Hebrides).

E. c. efatensis is slightly and incompletely differentiated from E. c. serena, and I treat
it as a synonym of the latter. Differences in the red coloration of the head and upper tail
coverts seem to be due to differences in wear in the available specimens. The serena series
was taken in February and appears to be more worn than the efatensis series, taken in
June and July. Mayr (1931:10) also mentioned possible differences in the color of the
secondary coverts, those of serena thought to be green versus bluish in efatensis. I found
this character to be variable, with the fully adult serena being quite blue.

In wing length Mayr (1931:9) shows efatensis as being 61-65 mm in 26 adults, versus
66-67 in 3 adult serena. I have remeasured 16 of the efatensis and 2 of the serena and
find that while the former average shorter-winged, there is overlap. My efatensis measure-
ments are 62.5-66.5 and serena are 65-67.5, thus showing an overlap in the range 65-66.5
(4 birds). Range: Aneiteum and Efate Islands, New Hebrides.

DELAWARE MUSEUM OF NATURAL HISTORY, GREENVILLE, DELAWARE 19807, 10
APRIL 1972.

THE BEHAVIOR OF PLAIN-BROWN WOODCREEPERS,

DENDROCmCLA FULIGINOSA

Edwin 0. Willis

IN forests of tropical America, woodcreepers of the genus Dendrocincla
follow swarms of army ants persistently (Willis, 1960:158-159; Skutch,
1969:136; Oniki and Willis, 1972). Intensive studies of ant-following birds
on Barro Colorado Island, Panama Canal Zone, and brief studies in other
areas show that Plain-brown Woodcreepers regularly follow army ants. The
changes in foraging niche when these woodcreepers confront different sets of
competing antbirds at some of the localities have been detailed elsewhere
(Willis, 1966). Here social and individual behavior will be considered.

Feduccia (1970:1) lists many brief references, mostly in annotated lists,
on the behavior of woodcreepers. The only extensive studies have been
Skutch’s (1969) of Tawny-winged and other woodcreepers. Slud (1960,
1964) and several others, including Johnson (1954) and Snow and Snow
(1964) and Oniki (1970) among references not listed by Feduccia, have
commented briefly on the natural history of Plain-brown Woodcreepers.
The species and its genus and family are not well known ethologically.

Appendix 1 lists common and scientific names of birds mentioned herein,
following Meyer de Schauensee (1970), except for Central American birds
listed only in Eisenmann (1955) and for northern birds listed in the A.O.U.
Check-list.

THE PLAIN-BROWN WOODCREEPERS

Plain-brown Woodcreepers wait on or hitch up the trunks of trees like
slender woodpeckers or overgrown Brown Creepers. They live in the middle
and lower levels of humid lowland forests from Honduras to central Brasil.
Occasionally they wander to the edge of the forest, into cacao and coffee
orchards, or into second growth more than 5 m tall. Instead of hammering
or probing at bark or epiphytes, they peck prey off the surface of vegetation
or sally out like flycatchers to snap prey off nearby vegetation, the ground,
or out of the air. Commonly they follow army ants and capture arthropods
they flush. Occasionally they flycatch away from ants, alone or with wan-
dering interspecific flocks of insectivorous birds.

This is a brown bird with a dark malar streak below a i)ale gray face
(Fig. 1) ; as in many woodcreepers, the flight and tail feathers are rufous.
The yellow linings of wings and mouth and the pale throat seldom show
as the bird waits stolidly. A dark streak from hill to eye and a yellowish
streak behind the eye are similarly inconsj)icuous.

377

378

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 1. Plain-brown Woodcreeper on Barro Colorado Island, Panama Canal Zone from
slide; seen from below.

On Barro Colorado Island, weights of eight Plain-brown Woodcreepers ranged from
38.5 to 43.4 g (mean 41.6) ; these birds were captured over ant swarms, where food
is abundant. James Karr (pers. comm.), netting mostly birds away from army ants
nearby in the Canal Zone, found a range in seven birds (ten weights) from 35.0-44.4 g
(mean 40.4). Culmens of 39 Panamanian birds in the American Museum of Natural
History range from 27.1-32.5 mm (mean 30.2) without sexual differences.

Wing lengths (chord) for Panamanian specimens at the American Museum and at the
Museum of Comparative Zoology are 96-106 mm (mean 101.4) for 21 females and 102-
113 mm (mean 108.6) for 31 males. Some “males” with short wings and “females” with
long wings may have been sexed incorrectly, since labels of these particular specimens
indicate gonads were not enlarged. However, short-winged males may have been young.
(Birds with very worn, damaged or molting wings were excluded from samples). Birds
from other countries have different wing lengths, but males always average longer in

Edwin O.
Willis

WOODCREEPER BEHAVIOR

379

3

2

M

^ /

UJ

X

5o

is:

'ir

0.5

1.0 15 20 25

TIME IN SECONDS

±6

w5-

UJ

O 4 ■
Z

o

UJ 2 ■

\T'

\

nif'

0 0.5 10

TIME IN SECONDS

2.0

Fig. 2. Audiospectrograms of vocalizations of Plain-brown Woodcreepers. Above,
“song”; two caws of a Slaty Antshrike overlap the end of the song. Below left, a “stick”
alarm note. Below right, “long rattling.”

wing length than do females from any given region. The dimorphism in wing length
helped me sex some birds captured on Barro Colorado Island. Eight adult females
there had wings 101-105 mm long (mean 102.5), and four adult males had wings 108-
110 mm long (mean 109). Two other birds, with wings of 104 and 106 mm, were judged
by their later activity to be nearly-grown fledglings. Adult females also have vascularized,
featherless brood patches while nesting.

THE STUDY AREAS

The climate, forest, and study area on Barro Colorado Island and several other
localities where I watched Plain-brown Woodcreepers are described in Willis (1967).
This reference also describes the behavior of army ants (especially the important species,
Eciton burchelli and Labidus praedator) and methods of study. Many woodcreepers were
banded with color bands; female RBYM, for instance, had a blue band above a red
one on her left leg and a yellow band above red/white one on her right leg.

I studied woodcreepers over or away from army ants on Barro Colorado from 28
September, 1960 to 25 November, 1961, and for a few months each year to 1971. Infor-
mation on Plain-brown Woodcreepers comes mainly from observations at swarms of army
ants while I was watching many species. However, nearly as many hours have been spent
censusing birds while looking for ants, so that the woodcreepers have occasionally been
studied away from ants.

VOICE

Plain-brown Woodcreepers have only five calls that seem worthy of sep-
arate names, and none is varied, complex, or musical.

Sticking. — This is a piercing, sudden, high-pitched (Fig. 2) sclieek or
stick given by an alarmed bird. The beak flajis o])en suddenly, showing the

380

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

yellow lining more prominently than at any other time. The call is given at
a rate of less than 40 per minute unless the bird is extremely disturbed.

Rattling. — This is a faint series of short grunting noises like the distant
put-putting of an outboard motor or clacking of a train. The whole body
quivers for the notes, but the bill is closed or barely open. The series may
be brief (“rattlet”) or continue for several minutes at a time (“long rattle”).
Cliut-ut-ut-ut-u-u-u-u, a-a-a-a-a-a-a, riiiii chew-ew riiii and similar nota-
tions are in my field notes for this call. It often varies in pitch and speed,
but usually is at about 23 notes per second ( Fig. 2 ) .

Singing. — The rough “song” of this species (Fig. 2) is a descending series
of 25 or so notes, each one like a grunt during rattling but less rough in
quality and given more loudly. Notes are longer toward the end of the
song. Whee-hee-he-hah-huh-huh-huh-huh-huh-huh-huh-hu-hu-hu-hu-hu-hu-hoo-
hoo-hooh, wee-i-woo\ is one rendering. The sudden up-and-down ending,
the greater speed, and the loudness of the song distinguish it from the rather
similar but longer descending song of Black-striped Woodcreepers. Unlike
rattling, singing is rather stereotyped. Males, females, and young birds all
sing; songs occur in every month of the year, and seem communications of
isolated birds hunting others rather than aggressive calls or sexual ones.

Hissing and Growling. — When a bird follows another closely a hissing or
growling chauhh or similar sound is given. At increased speed the hissing
or growling grades into rattling.

Screaming. — In the hand or when pecked by a supplanting bird, a wood-
creeper screams roughly and piercingly. The burst of noise, screeah or the
like, is more like hissing than like the clear and distinct sticking.

POSTURES AND MOVEMENTS

While clinging to a vertical trunk, the Plain-brown Woodcreeper often
takes what may be designated the “standard posture” (Fig. 1 shows a slightly
crouched bird, close to the standard posture). The slender and rather long
body angles away from the trunk about 15 degrees and is clearly separated
from it in side view. The bird is suspended by the front claws as it rests on
the stiffened and somewhat incurved bare tips of the tail feathers. When seen
from behind, as the bird clings to the trunk, the three front toes on each foot
spray from just below the horizontal to 70 or so degrees above it, while the
rear toe follows the line of the tarsus at about 60 degrees below the horizontal.
The long, curved front claws dig into the thin and smooth bark usual on trop-
ical trees, and the rear claws clamp in to some extent. Ordinarily the toes
and sole of the foot are off the perch. The bill points about 15 degrees toward
the trunk, or some 30 degrees from the line of the body. The wings meet above
the base of the tail, and the bend of the wing is exposed.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

381

Table 1

Perch Characteristics of Plain-brown Woodcreepers

Height“

Angle**

Diameter

Height (m)

Records

Angle ( deg )

Records

Diameter ( cm )

Records

0.1

4

20 or less

31

0-1

11

0.2

19

40

37

-2

107

0.3

99

60

74

-3

206

0.4

242

80

284

-4

213

0.5

308

100

2525

-5

202

0.6

201

120

153

-15

1177

0.7

177

140

12

-25

471

0.8

218

160

4

-50

259

0.9

164

-100

138

1.0

148

100+

22

1

1580

2

1676

3

1167

4

1084

5

650

6

497

7

360

8

340

9

200

10

158

15

234

20

14

25

3

30

3

Totals

7966

3120

2806

“ Barro Colorado Island, 1960-1964 data over army ants. Records are 0^0.1 or 0—1 m up to
26-30 m.

Barro Colorado Island, 1960—1961 data over army ants. Records over 90“ represent clinging
to the underside of a perch. Records are for 0—20°, 20-40° etc.

^ Barro Colorado, 1960-1961 data over army ants. Records are 0—1.0, 1. 1-2.0 cm etc.

A tailless bird, in heavy molt, rests against the undertail coverts and upper
parts of the legs when clinging to a vertical perch.

On the rare occasions (Table 1 ) when this woodcreeper perches on a hori-
zontal or nearly horizontal perch, it frequently stands across it like a perching
bird rather than along it like a woodpecker. Commonly the woodcreeper sits
I close, splay-legged and somewhat humped around the perch (Fig. 3,1)), hut
at times one stands almost as upright as a thrush. One bird that tried to perch
crosswise on a wet limb kept sliding backward (Fig. 3,E). A woodcreeper

382

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 3. Perching and travel of Plain-brown Woodcreepers. A bird alarmed by the
stieking of another holds its head out (A), flies to another trunk and crouches IB),
swings around the trunk (C) and on to another foraging area, where it perches briefly
on a horizontal limb (D) but keeps sliding back on the wet bark (E) ; it flies to the
ground briefly but has its crest raised (F). Another bird flashes its wing to flush a
prey (G), waits on a slender sapling above ants (H), dives toward prey on the ground
(I, J) by using its wings. From scattered field sketches at Simla, Trinidad.

perching crosswise reminds one of a leaf scraper {Sclerurus sp.) or other
furnariid. The plain brown leafscrapers often cling vertically to a tree trunk
or buttress when first flushed, and then resemble Plain-brown Woodcreepers
remarkably. Feduccia (1969) suggests from morphological studies that the
genus Dendrocincla may have evolved from Furnariidae, but from the foliage-
gleaners (Philydorinae) rather than from leafscrapers (Sclerurinae) .

Plain-brown Woodcreepers stay on perches near the vertical far more
often than they stand on horizontal perches or cling underneath perches
(Table 1). Their woodpeckerlike adaptations also seem better suited for
perching on trunks larger than 2 cm in diameter (Table 1), particularly for
poles 5 to 15 cm in diameter. In this respect they differ from such competing
birds as Bicolored Antbirds, which cling horizontally to vertical perches but
cling to perches more than 4 cm in diameter only with great difficulty
(Willis, 1967). The vertically-clinging types of birds and the horizontally-
clinging types, both usual at swarms of ants, complement each other. Oc-
casionally a Plain-brown Woodcreeper clings to slender saplings, especially
on Trinidad where competing antbirds are absent. If the sapling is 1-2 cm
in diameter, the bird simply interlaces its toes. On perches less than 1 cm in
diameter the bird has to put one foot above the other (Fig. 3,H) or oppose

Edwin O.
Willis

WOODCREEPER BEHAVIOR

383

the first and second toes of each foot while the outer toes hang freely. The
outer feathers often slip forward and do not support the bird on such narrow
perches.

Plain-brown Woodcreepers perch near the ground when few antbirds
compete with them and high in the trees when antbirds are present (Willis,
1966). Table 1 summarizes the vertical distribution of the Woodcreeper over
swarms of army ants on Barro Colorado Island.

HOPPING AND FLIGHT

Plain-brown Woodcreepers move up or down trunks by hopping or
“hitching.” In hitching upward, the bird catches itself with the tail at the
end of each backward extension of the legs, then flexes the legs and catches
hold of the bark again. In contrast to Barred Woodcreepers, hitching up and
around perches is far more common than hitching downward. However,
Plain-brown Woodcreepers do back downward occasionally. I have never
seen hitching with head down like a nuthatch. On a horizonal perch or on the
ground the bird may hop sideways, body angled at about 60 degrees from the
line of progress; but the short legs force the bird to fly or flutter-hop for
progressive movement. Adaptations for perching like a woodpecker definitely
restrict freedom of movement on a perch compared with species like Bicolored
Antbirds (see Willis, 1967).

In taking flight, the main push comes from the wings rather than from the
short and forward-angled legs. These woodcreepers seldom hop from one
perch to another without flapping the wings, and rapid movement up a trunk
is often performed by fluttering vertically rather than by hitching. The long
claws, which keep the feet off the trunk, probably do not permit rapid hopping
or the effective use of the legs in taking wing in many situations.

Flight is strong. The long and broad wings flap rapidly, with occasional
pauses, as a bird weaves rapidly through leaves and branches. The flight
is slightly undulating. Long flights in one direction are rare, but the birds
are expert at frequent changes of direction and at darting in and out of
moderately dense vegetation. At times a fluttering or slow flight is adopted
when one bird chases another. Flight is silent unless the bird hits leaves.
These woodcreepers hover readily for brief periods: they can hover in any
direction but backwards. In general, they combine speed with maneuverability
very well.

In alighting, the Plain-brown Woodcreeper seldom glides up and in with
wings outspread as do larger woodcreepers (especially the Barred Wood-
creeper) ; it usually flaps as it comes to the perch, then quickly closes the
wings when it alights. The yellow wing linings are seldom consj)icuous in
flight.

384

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 2

Activities of Plain-brown Woodcreepers away

FROM Swarms of

Ants

Activity

Occasions

No. Birds

No. minutes

1. Wandering

a. With other ant-followers^

12 ( 4.4%)

13

53

b. In to playback*"

8 ( 2.9 )

8

50

c. Singing

59 ( 21.5 )

65

163

d. Rattling or quiet

38 ( 13.9 )

48

159

2. Foraging

a. With bird flock"

38 ( 13.9 )

47

498

b. Not with flock

20 ( 7.3 )

26

231

3. Bathing

8 ( 2.9 )

11

54

4. Resting

1 ( 0.4 )

1

7

5. Search for nest site

3 ( 1.1 )

4

29

6. Stieking at predator or me

67 ( 24.4 )

84

314

7. Activity uncertain

20 ( 7.3 )

22

41

Total

274 (100.0 )

329

1599

“ Bicolored Antbird, Ocellated Antbird, Spotted Antbird, or Barred Woodcreeper. Recorded with
Gray-headed Tanagers elsewhere (Rio Agua Salud, Panama Canal Zone).

*> Of songs of Bicolored Antbirds.

^ Followed flocks of birds for at least one minute.

WANDERING AND INTERSPECIFIC FLOCKS

Johnson (1954:45) proposed that Plain-brown Woodcreepers typically
follow the wandering interspecific flocks through the forest but are easily
attracted to flocks of birds that follow army ants. I would reverse the order
of importance. These woodcreepers follow army ants whenever they are
available, even when no other bird is present, but occasionally join the wan-
dering flocks when no ants are available. At other times the woodcreeper
drifts through the forest alone, waiting and foraging as it goes, until it en-
counters a swarm of ants.

Away from swarms the Plain-brown Woodcreeper typically travels singly.
Two adult birds together are generally unmated and unrelated birds, together
for a short time. Most groups of two and three birds are a female with de-
pendent young. Away from swarms on Barro Colorado, I have 210 records
of one bird, 46 records of two, and 6 records of three together. The activities
of these birds are listed in Table 2. For this table, a bird was considered
to be “wandering” if it rapidly changed perches in a given direction and spent
little time looking about at stops; a “foraging” bird stays and looks about
from a perch, and changes perches first in one direction and then in another.
Wandering birds forage to some extent.

WOODCREEPER BEHAVIOR 385

Fig. 4. Percentages of Plain-brown Woodcreepers away from swarms of army ants on
Barro Colorado Island, 1960-1965.

Plain-brown Woodcreepers forage readily away from swarms of ants, in
contrast to such ant-following species as Bicolored Antbirds (Willis, 1967).
The percentage of woodcreepers away from swarms of ants on Barro Colo-
rado rises during the rainy or nesting season (Fig. 4), when arthropods are
more numerous away from swarms of ants. Highest use of swarms is in the
late rainy season and in the dry season, when the young of the previous
breeding season swell the ranks of ant-following birds (Fig. 5). There is
some variation from year to year. In January and February of 1961 an
unusually high percentage of woodcreepers wandered away from swarms.
Perhaps this was a case of what Tinbergen (1946) calls “specific search
images.” During the preceding three months there had been an unusual
number of swarms of Labidus praedator, which emerged frequently in the
wet year of 1960. Disappearance of swarms of praedator in early 1%1
apparently left many woodcreepers searching for them, even though swarms
of Eciton hurchelli were not overcrowded during these months (Fig. 5). In
1964 and 1965 there were unusually many swarms of Eciton hurchelli, so
that the percentage of woodcreepers away from swarms (Fig. 4) and number
per swarm (Fig. 5) were both low.

On 58 of 255 occasions when Plain-brown Woodcreepers were recorded
away from swarms and ant-following birds on Barro Colorado, they were

386

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

•H-

o

5

w

CD

Q.

(o 2-

Q.

CD

<D _

O

XJ

O

O

O-I960

+ -I96I

*-1962

Y-1963

0-1964

A-1965

JAN.' FEB.' MAR.' APR.' MAY 'jUNE 'JULY ' AUG.' SEP. ' OCT.' NOV.' DEC.'

Fig. 5. Numbers of Plain-brown Woodcreepers at swarms of Eciton burchelli on
Barro Colorado Island, 1960-1965.

with the wandering interspecific flocks of the forest interior (Willis, 1972).
These flocks, which are entirely different from the ant-following interspecific
flocks even though a few species occur in both, are characteristic of many
forested areas in the tropics. Plain-brown Woodcreepers rarely lead such
flocks or attract other species; they are desultory joiners and followers, or
what Moynihan (1962) calls “active attendant species.” Moynihan’s term
“active” implies joining rather than activity; the woodcreepers do not forage
by moving actively, and often are rather inactive in following flocks about.

I doubt that other small birds often flush the large insects favored by wood-
creepers. It is more likely that mixed flocks are efficient at detecting hawks
and other predators, so that individual birds can then devote more time to
finding food and specialize in foraging niches or use otherwise unsafe
niches rather than watch in all directions for predators (see Willis, 1972).
Plain-brown Woodcreepers stiek loudly from their elevated perches when
hawks or distant ground predators such as tayras {Eira barbara) appear.
The small birds near the forest floor are the first to call when predatory
mammals pass in dense vegetation. Thus the high-foraging woodcreepers
must often get advance warning of danger in a zone where they are not
foraging actively.

I sometimes detected a Plain-brown Woodcreeper away from swarms by

Edwin O.
Willis

WOODCREEPER BEHAVIOR

387

its loud sticking when I or a predator passed (Table 2) . At other times wood-
creepers sang as they wandered through the forest. Most singing birds
wandered as if looking for a swarm of ants; such songs are sometimes an-
swered by birds at swarms, and the singer homes on the replier. Females
separated from their young also sing, and the young sing, stick or hiss to
their mother. The song is thus often used in the way Bicolored Antbirds use
‘doud-songs,” (Willis, 1967), as a locating or “lost” call rather than as a
territorial, agonistic, or sexual call. Songs occasionally follow agonistic en-
counters. Rattles and other calls were occasionally used by wandering birds,
but silence was more usual if birds were not singing or sticking.

Playing recorded loud-songs of Bicolored Antbirds in the forest (see Willis,
1967:25 for methods) brought Plain-brown Woodcreepers up to the loud-
speaker on 10 out of 79 trials. On several occasions the woodcreeper flew past
the speaker and then flew back to it when the next loud-song was played.
On a separate occasion the chirring of Bicolored Antbirds near their recently-
fledged young brought up a Plain-brown Woodcreeper. A woodcreeper is
thus able to home on the calls of the noisy Bicolored Antbirds, which as
professional ant-followers usually are close to swarms of ants. It also homes
on the calls of other species that follow army ants, especially the noisy and
common Spotted Antbirds. On 3 October 1961 one woodcreeper arrived as
two male Spotted Antbirds disputed away from a swarm. On several other
occasions woodcreepers flew to the songs of Spotted Antbirds or associated
with them in wandering flocks at points distant from known swarms ; in some
of these cases the two may have stayed together after leaving a folded or in-
active swarm nearby, however. Plain-brown Woodcreepers occasionally follow
other professional ant-followers when they move between branches of a
swarm or to other swarms distant in the forest (Table 2).

Besides homing on the calls of other species that follow army ants or fol-
lowing those species about. Plain-brown Woodcreepers show several other
behavior patterns usual among “professional” ant-followers. Interest in
ants is not confined to swarms that are actively flushing insects, as is usual
for the many “non-professional” ant-followers on Barro Colorado and else-
where. Plain-brown Woodcreepers commonly visit “statary” (sedentary)
army ant bivouacs, peer around the tree trunk, and follow any line of ants
to the distant swarm. The woodcreepers occasionally wander near inactive
bivouacs for hours until the ants finally start swarming. Plain-brown Wood-
creepers, like other professional ant-followers, move along lines or trails of
ants between nomadic bivouacs and swarms rather than stumbling on swarms
by accident. Individual woodcreepers follow the same colony of the army ant
Eciton hurchelli for days or weeks at a time, return to it })eriodically during
a statary period, and may resume following the colony when it becomes active

388

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

again during the nomadic period. They shift readily from one colony to
another, even when they have to travel a kilometer or more to do so.

Plain-brown Woodcreepers show by their behavior that they are strong
ant-followers, and they are certainly “professional” ant-followers (ones that
get more than 50 per cent of their food over ants) even though they forage
readily away from ants. On Trinidad, where competing ant-following ant-
birds are absent, the woodcreepers rarely forage away from swarms. In other
regions they probably depend on swarms of ants for most (60-90 per cent)
of their food.

FORAGING BEHAVIOR

When following army ants a Plain-brown Woodcreeper waits on the trunks
of trees or saplings, turning its head at intervals, until a large prey moves;
then the bird darts over and snaps the prey out of the air or off the vege-
tation. Occasionally a bird hitches up or down, perhaps spiraling rapidly,
and pecks prey while on a perch. These birds rarely poke in epiphytes or
under bark as do many species of the Dendrocolaptidae. At times there is
an involved aerial or semiaerial pursuit, with fluttering or hovering or
rapid changes of direction.

When foraging off the ground. Plain-brown Woodcreepers forage most
actively around rotten trunks and stubs, tangles of lianas in the crowns of
saplings, near epiphytes, in the crowns of palms, at places where a dead limb
or tree has jammed above the ground, and near other tangled places. Usually
the birds wait on vertical lianas or saplings near the tangle or palm crown
and sally to the periphery of the tangle for prey. At times, how^ever, a bird
hitches or flutters to deep within a tangle. The vicinity of a tangled treefall
on the ground is another favorite site. When the ants pass through open
forest, the woodcreepers scatter to vertical trunks and forage little unless
competing antbirds are absent. Then they forage rapidly, and capture many
prey items on the ground.

Table 3 lists foraging motions for Plain-brown Woodcreepers over ants
on Barro Colorado Island. Birds take prey on the wing (“sallying”) more
frequently than they “lunge” or peck for prey from a perch. Prey taken on
trunks is commonly pecked, however. Although these woodcreepers sally to
the ground rather frequently, they take a large proportion of their prey from
leaves and other vegetation above the ground. A greater proportion of prey
is taken above the ground when such competing ground-foraging antbirds as
Ocellated Antbirds are present (Willis, 1966).

The woodpeckerlike foraging position of the Plain-brown Woodcreeper
seems a distinct disadvantage compared to the crosswise positions of com-
peting ground-foraging antbirds. The woodcreeper uses small trunks only

Edwin O.
Willis

WOODCREEPER BEHAVIOR

389

Table 3

Foraging Motions of Plain-brown Woodcreepers^

Place of capture

Foraging

Motion

Sallying

Lunging

Leaftossing

Prying

Ground, root, log

328

5

3

_

Trunk

219

263

-

1

Stem or liana

230

83

-

-

Limb or twig

27

8

-

-

Leaf or petiole

410

23

-

-

Dead leaf or debris

26

7

-

-

Air

182

7

-

-

Unspecified

204

7

-

-

Total

1626

403

3

1

^ From 1 October 1960 to 30 September 1961,

over army ants on

Barro Colorado.

with difficulty (Fig. 3,H)- Large perches, besides being uncommon, block
part of a bird’s view. The woodcreeper must fly upward for a short distance
or turn in midair (Fig. 3,1, J) to get away from the trunk if it is to capture
prey below it, since it starts from a head-up position, but it is not delayed
more than a fraction of a second by the conflict of adaptations for clinging
with those for pursuing prey below it. Still, when a fast-leaping antbird and
a woodcreeper go for the same prey the antbird usually captures it. The
short legs and long toes of the woodcreeper also make hopping after prey
on the ground rather difficult. If the woodcreeper misses prey on the first
sally it must fly up again, fly short distances along the ground, or stay flop-
ping, wheeling, and pecking in the midst of attacking army ants. A long-
legged antbird hops nimbly about, exposing its feathers and body to the ants
only rarely.

Away from swarms, I have never seen a woodcreeper sally to the ground.
The woodcreepers forage 3-15 m above the ground at such times, in the mid-
levels of the forest. Probably this is the zone in which the perching behavior
and foraging motions of woodcreepers are most effective. Moreover, there
probably are few prey items large enough on the ground unless ants flush
them. Foraging strategy away from ants involves short waits on tree trunks,
hitches upward to new waiting sites, flights to other trunks, and the like. To
get food, a woodcreeper away from ants usually sallies to distant foliage or
trunks, and hovers to catch the prey or chases it in flight. Less often it pecks
off prey as it alights or as the prey alights, or pecks prey off a surface while
hitching upward. They are unlike most woodcreepers (genera Xiphorhynchus,
Glyphorhynchus, etc.), which forage by peering and pecking at or into trunks

390

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

40 r

Fig. 6.

Distances that Plain-brown Woodcreepers flew to try for prey (“sallying”).

and epiphytes close-by, but are like other ant-following woodcreepers (genera
Dendrocincla, Dendrocolaptes and Hylexetastes) , in being “flycatchers” to
distant surfaces.

Prey at and away from ants is captured both above and below a foraging
bird. The distances of sallying are shown in Fig. 6. The Plain-brown Wood-
creeper has a larger foraging radius than do such species as Bicolored Ant-
birds (Willis, 1967). However, 75 per cent of the prey of Plain-brown Wood-
creepers is captured within 3 m from the perch and 98 per cent within 6 m.

Plain-brown Woodcreepers frequently use “wing-flashing” when prey stops
and is concealed. The bird moves to the trunk where prey disappeared and
briefly flashes one wing widely along the surface of the trunk. On slender
trunks the bird may simultaneously sidle and peer around the trunk from the
opposite direction (Fig. 3,H), so that it will run into prey fleeing the wing.
At times a woodcreeper flashes its wings alternately, sidling and feinting back
and forth around the trunk as if shadow boxing. The bird may also angle
the head one way and then the other in the direction opposite the wing flashed
instead of sidling bodily. On larger trunks the bird may crane the head or
sidle in the direction of the flashed wing rather than in the opposite direction.
Thus wing-flashing is not just a way to sidle more rapidly, although it could
easily have originated from such rapid sidling motions.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

391

Food

Table 4

OF Plain-brown Woodcreepers

Size

of prey in

mm

Food

?

0-10

10-20

20-30

30-40

40-50

50-125

Unspecified

no

60

34

4

1

Sowbug

1

Whip scorpions

2

3

Scorpions

1

4

4

Spiders

6

11

24

4

1

Egg case

1

Centipede

3

3

5

4

Millipede

1

Roaches

7

3

18

23

6

Orthopterans

12

15

32

17

4

6

Walkingstick

1

Mantids

1

1

1

Odonatans

1

Cicadas

6

1

3

1

Heteropterans

1

2

Beetles

2

Beetle grubs

1

1

Neuropteran

1

Moths

10

2

7

4

Caterpillars

2

1

Ants

4

1

1

1

Ichneumon

1

Hymenopterans

1

3

Lizards

1

2

3

“ Barro Colorado Island, 1960-1971.

In 89 out of 105 recorded observations of wing-flashing, the presence or
absence of foraging motions was noted. In 32 cases (36 per cent) the bird
peered intently after wingflashing one to several times but made no try for
prey. In one case the bird flashed at an insect covered by army ants; although
unsuccessful here, wing-flashing may occasionally flush prey already captured
by army ants. In a second of the 32 cases a Black-breasted Puffbird sitting
above captured prey flushed by the wing-flashing woodcreeper. In 57 cases
(64 per cent), the woodcreeper immediately sallied or lunged for fleeing prey.
The woodcreeper is thus somewhat less successful at wing-flashing than is
the Mockingbird which tries for prey after 74 per cent of its wingflashes
(Hailman, 1960).

I recorded successful wing-flashing to flush prey by a White-chinned Wood-
creeper at Cashibococha, Peru. Tawny-winged Woodcreepers flash the wings

392

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

even more frequently than do Plain-brown Woodcreepers. Perhaps the con-
spicuous tawny wing patches of the Tawnywing and the yellow undersides
of the wings of all three species are adaptations for flushing prey. There is
some use of double wing-flashing in aggressive displays in all these species,
however.

Orthopterans (mostly long-horned grasshoppers, katydids, crickets),
roaches, and spiders are the primary large food of Plain-brown Woodcreepers
at swarms of ants (Table 4). Moths, centipedes, scorpions, cicadas, and
lizards (mostly Anolis limifrons) are also taken readily. Only prey that was
held in the bill long enough for size to be estimated as a fraction of exposed
bill length (about 25 mm) or for reasonably certain identification is listed
in this table. The size range indicated is skewed toward the maxmum sizes of
prey, since small prey was often swallowed before I could see it. This distri-
bution of maximum-sized prey centers on the bill length of the species,
although slender prey (centipedes, orthopterans, damselflies, lizards) were
sometimes three to five times the length of the beak.

Small prey is swallowed at once. Large prey is frequently chewed vigorously
and hammered or flailed against the trunk. The woodcreeper may hitch up
the trunk now and then, hammering the prey at each stop, or fly to a new
perch to continue work. The feet are never used for holding prey. One wood-
creeper drooped its wings toward the trunk as it hammered prey, in the fashion
of a hawk “shielding” its prey. Moth and locust wings are usually dropped.
Legs and other small pieces of prey that fall are ignored, but the bird may
dive after a major piece. If dropped prey falls to near the ground it is readily
snapped up by Bicolored Antbirds. At other times other Plain-brown Wood-
creepers may catch dropped prey.

Some small prey items are dropped or thrown away immediately or dropped
after some chewing in the tip of the bill. These are probably prey with
chemical defenses, for the woodcreeper often wipes the bill and shakes the
head after such an encounter.

ANTING

Some small prey items elicit “anting” behavior. Instead of dropping the
prey and wiping the bill, the bird chews the prey in the tip of the bill, brushes
the prey through the rectrices or the under tail coverts (Fig 7,F), and resumes
chewing. Often the bird shakes the prey before brushing it through the
rectrices or regimes repeatedly. I recorded anting 67 times. On 35 occasions
the prey was eaten. On one occasion the bird dropped the prey and bill-wiped
repeatedly; on another, the prey was thrown away. On the 30 other occasions
I did not record what happened to the prey, but think it was generally eaten.
After a woodcreeper eats such prey, it often champs the beak or wipes it.

Edwin 0.
Willis

WOODCREEPER BEHAVIOR

393

Fig. 7. Postures of Plain-brown Woodcreepers. A, during long rattling. B, wing-
fluttering by a subordinate bird as a dominant one approaches. C, sunning on a log.
D, a dominant bird takes an aggressive posture as a subordinate one hitches up below it,
then (E) fights with it in the air. F, “anting” requires a C-shaped posture if the under-
tail coverts or tail is to be used.

Anting in this species is probably a standard method for treating distasteful
prey; it does not seem to reach the level of non-foraging anting as is recorded
for some birds (see Whitaker, 1957; Simmons, 1966; and Potter, 1970, for
summaries) .

394

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Southern (1963) and Potter (1970) suggest that anting soothes skin irri-
tated by molt processes. Potter does not cite Dubunin’s (fide Kelso and Nice,
1963) evidence that anting kills feather mites, nor my (Willis, 1967:33)
evidence that subordinate Bicolored Antbirds have to take distasteful prey
and ant with it. Perhaps there are two preening and one foraging uses for
anting, rather than the single use suggested by Potter. Her main argument for
anting as a molting poultice is that anting has been recorded more frequently
in months when birds are molting.

I have recorded Plain-brown Woodcreepers anting every month of the year,
but in 1960-61 I had more observations from September to November, 1961.
(In summer visits later, I have obtained many records for July and August).
September and October seem to be the main months of wing and tail molt in
Panamanian Plain-brown Woodcreepers, judging from my observations and
from the few specimes in museums. Some birds start molting in July and
August. Although molting may be the reason for a peak of anting in the late
months of an annual cycle, there are several alternatives that Potter does not
consider: since molting follows nesting in most passerines, there are more
birds present in molting months; the large number of young birds in months
of molt means that more can make mistakes and pick up insects with chemical
defenses; competition is high as young birds crowd in to local food sources,
forcing some to take prey with chemical defenses; there may be more insects
with chemical defenses about in late months of the annual cycle, since early
insects of such a cycle are not so subject to predation and can be fast-
reproducing ones without chemical defenses; observations of anting may be
less frequent in spring and early summer because most observers are distracted
by songs, bright colors, and territorial and reproductive activities of birds;
winter observations are rare because few insects are out in northern areas
and because few observers are out.

For Plain-brown Woodcreepers, the brief time of most anting episodes tends
to indicate that care of the skin or use against feather mites is not as important
as use as a part of a foraging strategy. Occasional sequences in which a bird
anted with several prey usually seemed reactions to absence of more suitable
prey rather than attempts to extend skin exposure to ants. Most anting epi-
sodes came when other Plain-brown Woodcreepers or Ocellated Antbirds were
interfering with the bird’s foraging, although some birds anted when few or
no competitors were about. While young and subordinate birds sometimes
anted, some adult and dominant birds also did so. There is not the clear
correlation of subordinate status and anting that I found for Bicolored Ant-
birds. However, Plain-brown Woodcreepers are a subordinate species that
uses a variety of prey items, and such birds might be expected to ant with
prey with chemical defenses more often than do dominant species.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

395

Simmons (1966) and I (Willis, 1967) have suggested that the original use
of anting may have been wiping off distasteful secretions of prey, and that
anting as a preening method may be learned individually. That such tropical
species as Plain-brown Woodcreepers and Bicolored Antbirds show anting
as a foraging pattern rather frequently may reflect the well-known diversity
of tropical insects. Species of distasteful prey are likely to vary tremendously
in appearance and to look like mimicking palatable prey rather often. It may
be better strategy for a hungry or young bird to try for prey and then find if
it is palatable rather than wait until species known to be palatable appear.
Species of intermediate palatability may provide suitable prey for hungry
birds if they are detoxified by chewing and by rubbing their secretions on
the wings or tail.

MAINTENANCE BEHAVIOR

After chewing distasteful prey or large, juicy prey the bird often wipes the
bill in the usual fashion: alternate sides, base to tip. Fluffing the head, a
frequent movement in bill wiping in many species, was not detected. However,
the feathers of the head are so short that it is difficult to detect head fluffing.

To egest fecal material, the Plain-brown Woodcreeper lifts the tail off the
trunk by flexing the femora briefly, ejects the dropping forcefully, and quickly
drops the tail to the trunk. Probably front and hind claws oppose each other
at such times. Occasionally a woodcreeper coughs up parts of insect exo-
skeleta. It gapes one to several times as if choking, then shakes the head
briefly as it is turned to one side; the exoskeleta drop out of the open beak.

Periods of inactivity or preening frequently interrupt periods of foraging.
In addition, when competing antbirds are present, the woodcreepers are partly
excluded from the continuous source of food near the ground and must depend
on occasional probes of ants into tangles above the ground. During periods
when ants are inactive above the ground the woodcreepers may cling and
look about for long periods or wander widely about the swarms. They dis-
appear for minutes at a time, but reappear as soon as the ants start up a tree.
Johnson (1954:60) was also struck by similar behavior patterns when he
watched these woodcreepers at swarms.

When preening interrupts periods of waiting or resting, the woodcreeper
generally perches vertically in woodpeckerlike fashion. To preen the body,
the feather tract is fluffed and the bird pokes the bill down in to the feathers,
then out. In addition to movements of the feathers and neck, the bird extends
the legs when it preens the underparts and flexes the legs when it preens its
back. In the latter case the bird may rest on the ventral feathers for a time.
There is also no difficulty when the wings are preened; extension of one
wing at a time does not interfere with perching. However, preening the tail

396

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

and scratching the head require awkward contortions. To preen the tail the
bird raises it and directs it laterally, then falls back on the tail coverts or the
sides of the tail so the body forms a C-shaped arc. Plain-brown Woodcreepers
always scratch the head over the wing. When one foot is released from the
trunk the bird seems to rest on the abdominal area on that side while the other
foot grasps strongly and the tail forms the other leg of the tripod. Scratching
the head is often awkward and hasty even when the bird rests in this position.

Perhaps the requirements of grasping during egestion and preening partly
account for the large size of the rear toe, which Bock and Miller (1959)
consider a hindrance or functionless in climbing birds that use the tail for
support. In the Plain-brown Woodcreeper the rear toe is shorter and thicker
than the front toe ; the rear claw is less curved but is longer and thicker than
a front claw. The rear toes and claws of this bird probably have a different
function from the front ones rather than being vestigial, and in perching may
act as wedges to prevent backward rotation. Perhaps a small bird that clings
to smooth-barked tropical trees and to the under sides of smooth trunks or
limbs occasionally clamps front and rear toes into the bark. Plain-brown
Woodcreepers also use their rear toes to perch horizontally.

Woodcreepers stretch in the ways usual among birds: yawning, half-

flexing both wings, or stretching fully on one side or the other (see Willis,
1967). When the bird does a left or right stretch the leg on that side is
stretched and the bird swings against the trunk. I have not recorded toe-
standing, which should be difficult for a clinging bird. After stretching move-
ments the bird usually flies off.

Occasionally a woodcreeper suns itself on a log (Fig. 7,C) or on a limb of
a tree. One wing and side of the tail are spread more fully than the others,
and the face on the same side is turned toward the sun. Ordinarily Plain-
brown Woodcreepers avoid full sunlight, although they readily cross clearings,
openings in the forest, and esteros on Barro Colorado Island. They are by no
means as strongly restricted to forest as are Bicolored Antbirds and similar
species. On Trinidad, Plain-brown Woodcreepers follow swarms of ants
through open cacao groves and to isolated trees in yards and pastures. Rivers
and clearings should not be strong barriers to this species. There is little
evidence of subspeciation across large rivers in the tropics, except across the
“inland seas” of the Amazon, Tapajoz, and Madeira. There is much reason
to suspect any subspeciation arose in isolated forest refugia during dry climatic
periods, not because of the rivers (Haffer, 1969).

On many occasions woodcreepers bathed in holes in trees. I repeatedly
found one or two woodcreepers bathing in one hole in a fig crotch in the
evenings. On one occasion another bird drank after peering in the knothole,
then backed in carefully and repeatedly, emerging and shaking briefly be-

Edwin O.
Willis

WOODCREEPER BEHAVIOR

397

tween dips. Investigation of cavities above ground is frequent, perhaps for
roosting or nesting sites as well as for drinking or bathing.

Although this woodcreeper is a victim of the bites and stings of army ants
less often than are birds that perch near the ground, one occasionally bends
down quickly and throws an attacking ant into the air. Once a woodcreeper
ate a soldier of Eciton burchelli. Occasionally a woodcreeper jitters, shaking
one leg or shifting back and forth from one foot to the other rapidly, when
ants attack. Normally the bird hitches a few centimeters away and waits in
a position out of the stream of ants.

REACTIONS TO HUMANS AND PREDATORS

When predators appear. Plain-brown Woodcreepers occasionally freeze in
place by clinging very close to the trunk and staying very still. Often the
reaction includes loud stieking. In addition to the yellow flash from the gape
as the lower mandible flaps down for each call, occasional flitting of the
wings may betray the position of the bird. The yellow under wings flash in-
conspicuously when a bird flits. Often one wing seems to extend more than
the other, but flitting never extends as widely or as close to the trunk as does
wing-flashing, which is normally a movement of one wing. Commonly a
stieking or silent bird whisks around the trunk so that it is hidden from the
predator or the observer. At times it hitches up the trunk, flitting the wings
at each jump, or darts suddenly and repeatedly from one tree to another,
circling trunk after trunk. There is relatively little fluffing or sleeking,
although a freezing bird is slightly more fluffed than usual and a hyperactive
stieking bird is more sleeked and stands out farther from the trunk than it
does in the standard posture. However, birds freezing on slender saplings
seem sleeked, as if hiding behind the saplings. Often the bird jerks its head
one way and then the other with or between stieking notes.

Stieking is commonly set off by a hawk, although it is also a common re-
action when I first appear at a swarm unless the individual bird has seen
me frequently. Stieking was recorded as reactions to hawks on 29 occasions
involving seven species of hawks. Other records included stieking at a
Spectacled Owl (1), Mottled Owls (2), Turkey Vultures (3), Collared
Aragaris (1), Chestnut Woodpecker (1) in Brasil, a large bird flying over
(1), the alarm note of a Buff-throated Woodcreeper (1) in Brasil. Once a
woodcreeper stieked at a tayra, once at a jaguarundi {Felis yagouaroundi) .
once at running agoutis (Dasyprocta punctata), once at squawking of a
squirrel [Sciurus granatensis) , twice at the grunting and stick-dropping of
white-faced monkeys [Cehus capucinus), once in Peru at red litis [Callicehus
cupreus) , and several times at my swinging my cap at mosquitos.

Many other birds react to stieking by freezing, fleeing, or giving alarm
calls: Ocellated Antbirds (31 records). Bicolored Antbirds (13), Spotted

398

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Antbird (12), Gray-headed Tanagers (3), Buff-throated Woodcreeper (1),
Chestnut-backed Antbird (1), Streaked Elycatcher (1), and Barred Wood-
creeper (1). In Peru a Lunulated Antbird keened; in Brazil, a Harlequin
Antbird chipped. In Guyana, Rufous-throated Antbirds (2), White-plumed
Antbirds (2), White-browed Antbird (1), and a Black-banded Woodcreeper
(1) fled. At times, other Plain-brown Woodcreepers repeat stieking or flee
when one bird starts calling. Usually only one or two birds stiek at a time
while the others hide or stiek infrequently.

The reactions of Plain-brown Woodcreepers often precede those of other
ant-following birds when a predator appears in the canopy, partly because
these woodcreepers forage high in the vegetation rather than concentrating
on ground prey as is the case for many ant-following birds. Once a wood-
creeper, seeing a tayra approach on the other side of a hill, stieked and
alarmed ground antbirds before the latter could see the tayra. However,
Plain-brown Woodcreepers are also prone to hysterical outbreaks of stieking
with no obvious cause after a hawk disappears or I take a position behind
the swarm. Other birds at swarms may start a “dread,” becoming hyperactive
and giving alarm calls, when a woodcreeper continues stieking or resumes
it long after danger has passed. Since the woodcreeper sometimes moves
down and forages in the zone deserted by the antbirds even though it continues
to stiek, one wonders if its seeming hysteria may help it by relaxing com-
petition from domineering antbirds. I have suggested this for another sub-
ordinate bird, the Spotted Antbird (Willis, 1971). Another possibility is
that the hair-trigger hysterics of Plain-brown Woodcreepers discourage
types of predation which are probably quite common in tropical forests.
In central Brasil the Lined Forest-Falcon, which occasionally follows ants
for hours, often returns time after time to the same area. It sits and waits
quietly for long periods. Although I have seen it capture only large insects,
it undoubtedly gives the antbirds and woodcreepers reason for hysteria.
Stieking may annoy such predators so that they move away, or keep the birds
on their guard against still-hunters and hawks that return repeatedly. Plain-
brown Woodcreepers, which work the middle levels of the forest in a zone
where there is light and space for a hawk to maneuver, have to be more
careful than do antbirds foraging in dim and tangled areas near the ground.
On Trinidad, where the woodcreepers work near the ground on an island
that has few species of forest hawks, they were far less prone to hysterical
stieking than in other areas.

Plain-brown Woodcreepers react to the alarm calls of other birds. At
chipping notes of Bicolored Antbirds or stieking of another woodcreeper,
a woodcreeper often presses close to its perch, sleeks, and freezes. At chipping
of Spotted Antbirds, one looked about quickly.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

399

Woodcreepers that have had some experience with me quickly become
tame, especially if I scare away Ocellated Antbirds or other domineering
competitors so that the woodcreepers can forage near the ground. At times
the woodcreeper changes from flitting and then sleeked hiding behind trunks
to open foraging via the “displacement activity” of preening. However, I
never saw any evidence of the “curiosity” or investigating behavior so
characteristic of tame Bicolored Antbirds. Woodcreepers use peering and
investigating behavior very little in foraging, in contrast to Bicolored Ant-
birds; the seeming lack of curiosity may be related to their noninvestigative
type of foraging. Still, tame woodcreepers often hide behind trunks of trees
when one tries to observe them closely.

Woodcreepers that were semi-tame or ones that I forced to fly from a
swarm sometimes reacted with long rattles. Once long rattles were a reaction
to marmosets {Sag,uinus geoffroyi) . The bill is closed and the bird hardly
moves, except for a pulsing low on the neck. The neck seems long, probably
because of extending the angles between vertebrae (Fig. 7,A). The feathers
of throat and forehead, possibly those of the entire head, are raised as the
bird clings close to the trunk. The feathers of the vent are also fluffed. The
bend of the wing is sometimes exposed. One bird ended its rigid display by
ejecting feces, doing a half-flex of both wings, and spiraling up the trunk.

Woodcreepers held in the hand for banding commonly scream loudly and
persistently. Some individuals squeak rather faintly or growl softly. Clawing
stops if the bird is allowed to grasp a finger. Pecking is often vigorous, but
these woodcreepers do not hold and twist so vigorously or for such a long
time as do antbirds.

AGONISTIC BEHAVIOR

The frequent interspecific supplantings when Plain-brown Woodcreepers
and other species compete over swarms of ants have been discussed elsewhere
(Willis, 1966).

Large birds that follow army ants supplant (chase from its perch) or
displace (cause to move off) the Plain-brown Woodcreeper (Table 5). It
is rather nonaggressive, except to a few stolid moderately large birds and to
small ant-followers. Buff-throated Woodcreepers are particularly pugnacious
to it, and chase it about persistently on the rather infrequent occasions when
Buff-throats follow army ants. Black-striped Woodcreepers are also rather
pugnacious on the few occasions when they follow ants. Most of the large
ant-following birds in Panama, such as Barred Woodcreej)ers and Ocellated
Antbirds, supplant or displace it rather regularly; but the Plain-brown
Woodcreeper is good at keeping out of their way. In other countries, I have
seen Plain-brown Woodcreepers supplant Scale-hacked Antbirds and White-

400

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table

Antagonistic Interactions of

5

Plain-brown

Woodcreepers

Numbers of Wins/Losses by Species A

a

Species A

Fights

Supplantings

Displacings

Returns’^

Plain-brown Woodcreeper

53

1196/

65/

Barred Woodcreeper

109/

48/

Ocellated Antbird

80/

28/

4/

Buff-throated Woodcreeper

85/2

18/

2/

Bicolored Antbird

1

60/16

8/11

Black-striped Woodcreeper

42/

9/

Gray-headed Tanager

2

9/9

6/1

Squirrel Cuckoo

2/

7/

Black-breasted Puffbird

4/

1/

Bright-rumped Attila

2/1

Rufous Motmot

1/

1/

Keel-billed Toucan

1/

Broad-billed Motmot

/I

Canada Warbler

/I

Acadian Flycatcher

/I

Wedge-billed Woodcreeper

/I

Scaly-throated Leafscraper

/I

White-whiskered Puffbird

/I

Slaty Antshrike

/2

Swainson’s Thrush

/5

/2

Spotted Antbird

/9

/4

® Barro Colorado Island, over ants, 1960-1971.

** One bird has to watch until other leaves before moving in.

throated Antbirds. Rufous-vented Ground-Cuckoos, Ruddy Woodcreepers,
Red-billed Woodcreepers, Hoffmanns’ Woodcreeper, Spix’s Woodcreepers,
Black-banded Woodcreepers, Rufous- winged Bare-eyes, Black-spotted Bare-
eyes. Bare-crowned Antbirds, and Black-headed Antbirds supplant or displace
Plain-brown Woodcreepers. Twice I saw White-chinned Woodcreepers displace
Plain-brown Woodcreepers, and once a Plain-brown displaced a White-chin.

Generally a woodcreeper surprised by a larger species screams loudly if
attacked or pecked but simply flees or sticks and flits as it hitches up a trunk
if it is supplanted less strongly. It may ruff the throat, or cling close with
feathers fluffed out. The woodcreeper gives rattlets or long rattles if it is
gradually crowded out or displaced rather than attacked bodily. Once one
shivered the wings as it approached a Barred Woodcreeper, which did not
attack it.

Interactions with species close to its own size or dominance are frequently
more varied. Once one supplanted a male Gray-headed Tanager (at 30 g,

Edwin O.
Willis

WOODCREEPER BEHAVIOR

401

only three-fourths the weight of the woodcreeper) by spreading the wings
and showing the yellow wing linings at it. A minute later the same tanager
supplanted the woodcreeper when it did not spread its wings. On another
occasion a tanager female, crest raised, gave faint notes as she pecked down
repeatedly at a woodcreeper under the limb she stood on. The woodcreeper
sidled back and forth, weaving and feinting at her with the beak, before
it flew off. When Bicolored Antbirds (30 g) supplant the woodcreeper the
latter sometimes stays and growls, pecking back at the smaller bird. How-
ever, the woodcreeper is usually forced to sidle back and forth around the
perch by the repeated jabbing of the more agile antbird, so that the wood-
creeper is often supplanted despite its initial resistance and larger size. Once
a woodcreeper supplanted the antbird by flashing one wing at it and growling
at it.

The intraspecific agonistic or competitive behavior of Plain-brown Wood-
creepers seems as undistinguished as their plumage and voice. Simple
avoidance, chasing, and fighting seem to replace aggressive and submissive
displays most of the time. When two or more birds are present at a swarm
of ants, they often stay apart. At times avoiding each other is not possible;
the birds crowd around a palm or liana-covered tree the ants are ascending.
At such times peck order is mainly evident in the well developed and rather
diverse methods of fleeing and pursuing.

When a dominant bird flies up near a subordinate bird or supplants a
third bird, the subordinate commonly sidles quickly behind its perch. If on
a slender sapling, the subordinate bird may cling close and sleek the feathers
as if to become as narrow as possible. Often one bird hitches up the trunk
or around it when another alights below it. It may turn the head one way
and then the other, looking down at the dominant bird (Fig. 7,D). When a
subordinate bird flies, its flight seems normal unless it is hotly pursued by
the dominant bird. It then twists and turns, zigzags in and around trunks,
and quickly hitches or spirals around them on alighting. It may stiek at times,
give rattlets in flight or on alighting, or end a series of rattlets with a song
if completely driven away from the swarm.

Commonly a dominant bird ignores a nearby subordinate as long as it is
quiet or sidles behind its perch. At times birds ignore each other even when
three or four aggregate within a meter of each other for minutes at a time.
Once a watching woodcreeper waited until another finished dissecting a
tettigoniid, then hitched up and supplanted it. Most species that follow army
ants wait until a subordinate finishes its meal before supplanting it, although
Plain-brown Woodcreepers and other species commonly supi)lant subordinate
birds during and immediately after prey capture. The position of dissecting
birds in this and other species, hunched close to the perch and with necks

402

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

retracted and bodies fluffed, may mimic submissive display and thus inhibit
attack.

At other times a dominant bird may pursue the other bird by hitching or
spiraling up the trunk after it, extending the neck to jab at it if it hesitates
too long, or flying after it for as much as several hundred meters off into
the forest or back and forth over the swarm. The pursuer or both birds may
adopt a somewhat slow, flapping flight like a dove or a buzzy flight like
a Spotted Sandpiper in the more protracted chases. Possibly such forms of
flight display the yellow wing linings. At times the fluttery flight is accom-
panied by “tailgating,” when the pursuer seems to slow and speed up when
the pursued bird does so rather than try to overtake and attack it. Such flights
may have sexual or parental connotations, as is discussed below.

Simple supplanting, often followed by long chases, is common. Fighting,
or at least pecking and fluttering duels around and around a perch or down
through the air (Fig. 7,E), is less common. Of 1,314 presumably agonistic
displacings or supplantings, 53 (4.0 per cent) ended in fighting. This fre-
quency is about ten times that for Bicolored Antbirds, a species with well
developed aggressive and submissive displays. The contrast between these
two species may support proposals that agonistic displays evolve to prevent
dysgenic fighting. Fighting involves pecking with the bill as well as scratching
at the opponent with the feet. Growling notes emerge during the more violent
fights, which sometimes end on the ground.

A common display of subordinate birds is “rattleting.” The beak is closed
as a rattlet of 5 to 20 notes is uttered. The rigid, rather sleeked bird often
ruffles the throat and lower face, sometimes the whole head. The neck is
sometimes extended or ruffled, but more often the head is close to the body.
At times the body seems ruffled. The wingtips commonly droop loosely.
The legs are flexed, so the bird is close to the trunk. The eyes seem glazed,
perhaps because they are diverged rather than focused binocularly. A bird
that is consistently chased or forced away from a swarm by another wood-
creeper or any other domineering competitor often extends rattleting into long
rattles, as described under “reactions to humans and predators.” At times the
calling is omitted from the display of rattleting.

Another possibly submissive display is gaping and growling, or growling
rattlets, during chases. Squealing comes from a bird losing a fight. Possibly
growling is restricted to sexual and juvenile-parent chases, described below.

At times the subordinate bird flits the wingtips out sharply and repeatedly
as it hitches jerkily up a tree after being supplanted. The dominant bird
occasionally flits the tips of the wings. Such actions commonly accompany
or lead into a stiek note or two, suggesting the bird may be panicking.

Occasionally the subordinate bird shivers or rapidly flutters the tips of

Edwin 0.
Willis

WOODCREEPER BEHAVIOR

403

the wings (Fig. 7,B). In seven out of 21 cases, however, the dominant bird
shivered the wings and then chased the other off. In some of these cases
the dominant bird seemed hesitant and initially unsure of its dominance, but
the meaning of wing-shivering is unclear. Among Bicolored Antbirds it seems
a juvenile or submissive activity (Willis, 1967, p. 47).

If there is an aggressive display in Plain-brown Woodcreepers, it is not
frequent or conspicuous. Ordinarily the aggressor starts a chase from the
standard posture, without calling. At times the legs are extended so that the
body is far out from the trunk, as in the more conspicuous aggressive display
of Barred Woodcreepers. If so, the head and neck are often arched, the head
being flexed toward the neck (Fig. 7,D). Really aggressive birds fluff out the
belly, chest, and back feathers ; but I have not seen strong ruffling. The head
is usually sleeked, so that the dark brown malar and presuperciliary lines seem
more prominent than usual but the pale throat and yellowish postsuperciliary
line less so. However, at times an attacking bird has the head ruffed; some
such birds seemed unsure of their dominance. At times the attacker gapes,
especially if defending a spot from an approaching bird. At times the yellow
underwings are flashed out as well, especially if the approaching bird persists
long enough to start a fight or chase.

One woodcreeper that preceded me to a swarm raised its back and cbest
feathers as it looked up at a bird one meter above; the latter dropped to half
a meter below the new bird and shivered its wings. The newcomer then tail-
gated the other off. On another occasion an arriving woodcreeper went round
and round a pole pecking and gaping at an unbanded bird ; the latter tailgated
the banded bird off after a pause.

MOVEMENTS AND TERRITORIES

Banding birds on Barro Colorado Island between 1960 and 1971 has given
a moderately clear picture of territoriality and movements, even though many
birds are not banded. Some banded individual birds ( Fig. 8) , especially birds
known to be less than a year old, wander irregularly. Other banded birds,
which I call “settled” birds, occasionally follow a swarm of ants outside
the centers of their home areas but return to the areas year after year until
they disappear. Settled birds with the long wings and feathered edges of
the ventral apterium characteristic of males (Fig. 9) wander out from the
centers of their home areas more frequently than do other birds (Fig. 10 I
with wing lengths characteristic of females; the latter are mostly birds that
have vascularized, bare ventral brood patches during breeding seasons and
birds that cared for one or more broods of young during the 1960-1971
period.

It is likely that the home ranges of these settled birds are territories, al-

404

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 8. Wanderings of Plain-brown Woodcreeper “XR” from November, 1960, to
September, 1961.

though there is not enough evidence on supplanting and chasing to be certain
of dominance. The known females have nearly exclusive ranges; I have yet
to observe two banded ones together at the same swarm of ants or to observe
two unbanded females with their broods at one swarm. The settled males
have home ranges completely overlapping those of settled females. The ranges
of settled males overlap each other, so that two or more settled males oc-
casionally follow the same swarm. However, overlapping of ranges is no
proof that animals are non-territorial (Willis, 1967) ; each male may be
dominant over other males toward the center of his own range. The centers
of ranges of settled males are different suggesting that males do have this form
of territoriality.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

405

Fig. 9. Observations of three settled male Plain-brown Woodcreepers, 1960-1971.
Within overlap zones, records of RYBX are underlined, of BYMG are overlined, and of
SOOS start with a parenthesis.

There is some evidence that settled males are subordinate to settled females.
The wider wanderings of settled males suggest this, since a subordinate bird
must wander more widely than does a dominant one to find an unoccupied
swarm. In 37 cases of supplantings involving settled females, the female was
the victor in 35 cases. The exceptions may represent meetings of two females
at territorial boundaries; in both cases the banded female was chased by an
unbanded bird at a place where the neighboring female was unbanded. On
14 August 1961, female RBYM (Fig. 10) supplanted male BYMG (Fig. 9)
within the ranges of both. Male RYBX rattleted whenever female BRYB
came near him on 18 August 1964; the location was well within the area of
the male but peripheral to the area of the female. On August 16 and 21 female
PSPM repeatedly supplanted male RYBX; she was near the edge of her
range, while he was well within the boundaries of his. On 2 October 1965
female BRYB displaced male RYBX at the edge of her range hut well
within his.

406

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 10. Observations of five settled female Plain-brown Woodcreepers, 1960-1971.
Dark lines separate records of individual females.

There were always unhanded birds wandering through the territories of
these settled males and females. Probably most of them were either males
with home ranges overlapping those of the banded birds or else wandering
birds. I do not know how many years these birds wander before they settle
down, for the only banded young rediscovered later (MGYY) was not found
until nearly 10 years after banding. The extremely long lives of settled birds,
especially settled females ( of three females banded in 1961 as adults, two
were still alive and on their territories in 1971 and the third disappeared after
1969) suggest that young may wander for years at times waiting for territories.

Preliminary evidence thus indicates that Plain-brown Woodcreepers have
the kind of territoriality found in the European Cuckoo, some lizards, and

Edwin 0.
Willis

WOODCREEPER BEHAVIOR

407

some mammals. Females occupy exclusive territories, while the settled males
have more or less separate ranges completely overlapping those of the females.
The spacing system should be investigated further in an area where Plain-
brown Woodcreepers are more abundant and easily studied, as on Trinidad.

There were 2.8 females and 1.8 males per square kilometer on the study
area in 1960-1971. (Each female had an area of about 36 hectares.) At 41
grams per bird, this is a biomass of 188.6 grams per square kilometer or 1.9
grams per hectare. Possibly there were 1 or 2 wandering birds per square
kilometer in May each year, or an additional 0.6 grams per hectare, for a
total of 2.5 grams per hectare. The total population of Barro Colorado Island
in May, at the low point of the annual cycle, would be about 90 birds. In
December there would be somewhat over twice as many birds, or 180-200
birds (5 grams per hectare).

SEXUAL BEHAVIOR

Sexual behavior seems to grow directly out of agonistic behavior in this
species. Pair bonds and courtship are certainly brief and rudimentary in
nature.

Males chased by females in seemingly normal agonistic encounters some-
times growl or give soft rattlets, and allow tailgating or a pecking duel rather
than flee to a distance. Gradually the two birds begin to associate in their
chasing and to ignore trespassing birds. There are persistent chases during
this period, but the two birds frequently alight close together and wait several
seconds before resuming pursuit. The two may peck and spar back and forth
before resuming a chase. Presumably the process involves an increasing
tendency for the female to stay rather that attack the male when he approaches
her, but these preliminary stages are difficult to distinguish from agonistic
behavior. Occasional reverses of chases, in which the pursuer becomes the
pursued, are the first clear sign that sexual behavior is involved and not just
agonistic or parental chasing.

Over the course of a few days other elements enter the feuding. The
chases become slower and more fluttery; there may be bursts of wingbeats
so that the two undulate in flight. The male consistently alights below the
female. Growling notes become more frequent than rattlets. Growling,
whether by pursued or pursuer, is sometimes accompanied by fluffing of the
throat, breast, and crown to a degree far surpassing the normal state among
rattleting birds. At times the feathers of the breast part from those of the
lower abdomen. The male may hitch up after the female at each stoj), even
though she pecks down at him and chases him off at times.

In the final days of the pair association, one bird consistently hitches
up to the other and nibbles more and more vigorously into its lower back.

408

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

“Nibbling” is often accompanied by vigorous growling from either bird, at
times speeding into a rattle. The throat of the chased bird is sleeked, but
the chasing bird fluffs its throat as it growls. The chased bird often takes
wing and is pursued by the other. The chased bird may jab downward re-
peatedly at the insistent other one, or hitch upward; but the chasing bird
quickly follows the chased one. The chaser swings back and forth below the
other when it jabs at him, then moves quickly in to nibble its back when it
returns to the standard posture. Eventually it stays still for the nibbling.
The male eventually nibbles her rump, then moves upward nibbling the
female’s back more and more rapidly and deeply. She gapes slightly and
flattens herself against the vertical trunk as the male hitches up on her back
and clings to her slightly spread wings. The male flutters rapidly as the tails
of both birds are shifted off and on the perch rapidly. The female seems to
rest on the side of her tail while the spread tail of the male remains on the
trunk. Copulations I have observed were brief, generally less than a second,
as both birds seemed to have difficulty copulating in this vertical position.
In one case the male hitched up above the female after copulation, then
hitched down past her and repeated the process of growling, nibbling, and
copulation. He chased her to new perches and attempted or completed several
more copulations during the course of the day.

On one occasion a female alighted just above an unhanded bird. As it
growled faintly and gaped slightly, she looked down and gaped as she hitched
down under it until she wedged up its breast with her tail. It gaped and finally
started nibbling before she looked down and chased it off in a fluttering aerial
flight.

On a few occasions wandering females were persistently nibbled by un-
handed birds even though each female snapped down at the other bird or
chased it off. On another occasion a female with young birds was persistently
nibbled by an unhanded bird, although fluttering and pecking aerial duels
were the result. Once a wandering young bird, independent less than two
weeks, nibbled the back of another bird. Perhaps a male may attempt
nibbling and copulation as soon as a bird it approaches fails to flee or
attack, whether or not male or female are settled or in the appropriate stage
of the nesting cycle. This may explain occasional cases where one bird nibbled
another and the second nibbled back before there was a fluttering chase.
However, female PSPM was observed to nibble the back of male RYBX in
one pairing sequence, and to be the recipient of nibbling from an unhanded
bird on another occasion, so the sex roles in nibbling must be reversed
occasionally.

Most observations of sexual behavior were for unhanded birds, so that
I do not know how many days the birds of a pair consort with each other or

Edwin O.
Willis

WOODCREEPER BEHAVIOR

409

Fig. 11. A, “cavity-sitting” by two woodcreepers. B, female BXRB peers snakelike
from the top of her nest cavity before leaving it and the single nestling. From field
sketches.

whether the female accepts more than one male. Observations of another
behavior pattern, “cavity-sitting,” suggest that the interest of the male may
extend somewhat beyond copulation. One bird flies to a cavity in the top of
a pole-sized stub, peers down into it and around, then turns and backs down
inside repeatedly. At times a second bird flies up and joins it in hitching up
and down inside the cavity (Fig. 11,A). Growling sounds emerge as if a
bumblebee is boring into the wood. After a minute or two of their jack-in-
the-box behavior one bird and then the other emerge and fly off. It may be
that copulations occur during cavity-sitting, for one wandering young female
was mounted by an unbanded bird as both cavity-sat, despite much pecking
when he first nibbled her back.

Male RYBX and female PSPM went through a sequence on 5 July 1966
in a way that suggested he was showing her a nest-hole. He gave a series of
growls at a hole in a big stub; she flew up beside him and he hitched side-
ways, then flew off; she hitched up and flitted as she peered in several holes.
Later he gave a rattlet as she hitched up to him. Both looked about, then she
nibbled his back a few times. He flew off after looking down at her.

NESTING

A bird brought food to and carried a fecal sac away from a northwest-
facing hole 4 m up in a stub 0.2 m in diameter in a new agricultural clearing
in the forest at Tres Esquinas, Colombia, at 10:04 on 20 April 1962. One
carried food to and a fecal sac away from a cavity in the top of a stul) 0.2 m
in diameter and 5.5 m tall, 25 m out in a manioc field in forest at Malo-
quinha, Brasil, at 18:02 on 25 February 1966. Pinto (1953) records an

410

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

incubating female collected at a nest with a single white egg 2 m up in the
trunk of a tree, 1 January 1924. Snow and Snow (1964) record dates of
laying in nests in Trinidad from May to “September” (= early October).
The latter record represents a young bird prematurely out of the nest on 10
November (D. W. Snow, in litt.). I noted adults still feeding grown young
out of different nests on Trinidad on 4 and 15 December 1961, so that the
nesting season extends later than the Snows indicate in their article and is
essentially the whole rainy season.

Five nests the Snows located (their three other records are of birds carrying
food to sites not exactly located) ranged from 1 to 9 m above the ground,
in tree holes, the open tops of a bamboo stake and of a broken Bactris palm,
and in a hollow tree branch. Two eggs were in each of three nests, two young
in a fourth; none were successful (the fifth nest, high, was not revisted) . Four
of the nests were in forest and one near a house.

One nest on Barro Colorado was 3.5 m in a cavity in the top of a 0.2 m
diameter stub in open forest. The nest-cup, a few dead leaves with a rhizo-
morph lining 0.5 m down inside the stub, held two small and downy young
with areas of bare orange skin at 13:50 on 3 June 1966. They were probably
two days old. One young left the nest about 16:30 on 25 June, so the nestling
period was 23-25 days.

I watched from a blind 38 hours on 12 days, mainly in the afternoons
because morning visits on 7 and 11 June (7.5 hours) showed no different
patterns. Only female BXRB fed the young. She brooded them only during
rain on 6 June and between 09:27 and 10:28 on 7 June; perhaps even small
young are often allowed to cool off despite the longer developmental period
lack of heat would require. Her visits with food were very irregular, from 4
to 162 minutes apart (mean, 46.0, n = 39). On 6 and 7 June the average
interval was 87 minutes, then 48 minutes on 10-11 June, 30 minutes on 14-16
June, 40 minutes on 18-20 June, 54 minutes for 21-23 June, and 39 minutes
for 25 June.

On nine occasions she brought variously colored cicadas, which probably
were not taken over ants. Other prey were a lizard {Anolis limifrons) , a
lizard or a frog, a roach, and orthopterans (2), and several mangled insect
abdomens. Usually she held the prey lengthwise inside her open bill, but the
lizard projected back past her face and the roach was held in the bill tip.
Prey was seldom less than the exposed bill length (25 mm). She was not
known to follow ants during the nestling period, although other females feeding
young in undiscovered nests have been known to do so.

She occasionally sang at a distance, but approached quietly otherwise
She often froze on a nearby sapling or the nest pole for a minute or two
looking about, before hitching to the nest edge and looking about again. If ]

Edwin O.
Willis

WOODCREEPER BEHAVIOR

411

approached the nest as she did, she stieked and fled with wing-flitting,
hitching up distant trees. Once a Chestnut-mandibled Toucan flew down
and scared her away as it peered in the nest before I drove it off with diffi-
culty. She froze or hitched behind the nest-stub at each whirr of toucan wings
overhead, but on other days had ignored their sounds.

To feed, she looked inside and flipped head-first into the cavity. Once,
returning in rain to brood without food, she backed tail first into the cavity.
She sometimes gave faint rattlets as she looked in or went inside, and con-
tinued them if the young did not take the food. To rechew food, she sometimes
reappeared at the nest entrance or flew off, then returned. Often she ap-
peared at the nest entrance after a feeding and craned her neck about slowly
like a snake (Fig. 11,B) for several minutes. At times her throat feathers were
ruffed. Often she champed her bill, especially one day when toucans were
flying overhead. Once she pecked and tossed a large ant {Paraponera
clavipes) walking nearby. After peering, she often hopped to the inside top
of the stub and waited before flying off, or flew off directly. A few times
she flew off directly before waiting at the entrance.

She normally flew off directly when carrying a fecal sac, which she did
on 12 of 26 visits between 14 and 24 June, but only three of 16 times 6 to 11
June and on one of five on 25 June. Presumably she ate most fecal sacs before
emerging until the young were about two weeks old, and ignored fecal sacs
on the last day.

The young gave a few hissing answers to her rattlets on 10 June and there-
after. On 16 June it gave a weak song inside the nest about three minutes
before the female arrived. On 25 June, but not as late as 24 June evening,
the young came to the nest entrance except during a rain. It seemed as big
as the female, but had a rather short bill, a tail one quarter the normal
length, and three-quarters-open remiges showing bare bases. It gave a
rattly song once, but preened and looked about silently most of the time the
female was away. It gaped widely for feedings and after one feeding. At
15:51 she watched as it flapped one wing out to climb up on the nest entrance
after a feeding, then tapped twice on the nearby trunk with her bill. Both
watched and waited as marmosets passed overhead, and it hissed at her a
few times. She pecked into its open gape before leaving 16:08, and it gave
squeaky rattlets as it looked after her. Later it fluttered atop the nest-stub.
At 08:34 the next morning the female looked in the empty nest; at 09:14 she
sang and rattled when I shook a nearby vine on which there was a snake
{Pseustes poecilonota) , discovered by scolding antwrens of a forest flock.

From 11 to 20 July the young and female were with army ants elsewhere
in her territory. On 11 July the young had tail and bill three-(piarters the
normal lengths, and was “playing” by pecking off and dropping bits of moss

412

THE WILSON BULLETIN

December 1972
Vol. 84. No. 4

(Other young often pecked at leaves and billed them or other bits of debris,
as if hungry or playing). It tried fluttery sallies for prey. On 16 July its tail
and bill were nearly the adult lengths, and it caught one prey on its own.
The female was by now in very worn plumage. (Female GX went into molt
when her young were about this age, 14 July 1966). On 19 July she pecked
it after it hissed near her, and it fled. On 20 July, however, she lured it away
from me with rattlets.

There is no information on incubation except for Pinto’s (1953) record
of collection of an incubating female. Skutch (1969) records that one bird
alone incubates and feeds the young in Tawny- winged Woodcreepers, another
species with the attack-and-nibbling type of sexual behavior. Probably the
female Plain-brown Woodcreeper also cares for eggs alone, as males lack
incubation patches. Male and female do not associate during the period of
nesting, as far as I have been able to determine.

Several other broods of young have been seen on Barro Colorado, including
other broods of female BXRB. The young appeared as early as June and as
late as September. One or two fledglings follow one female; no male asso-
ciates with the group. The young are well grown and fly well before the
female brings them to a swarm; the smallest young I have seen, those of
female PXRP in 1964 and of an unbanded female in 1969, were fully feathered
but had small beaks and half-length tails. At times these smaller young stay
in one area and the female commutes to them from a swarm. The female
more often stays nearby, even if no ants are available nearby. She stieks
loudly as a human passes, but the young are silent at this stage.

The young birds forage little at this stage, but they gradually become in-
dependent over the next month or two (young were with female RBYM at
least 17 August-11 October 1965). When the female catches food and has
hammered or chewed it thoroughly, she utters a brief rattlet. If the young
is busy preening, the female has to utter several rattlets. The young bird
eventually flies up, takes the food in hitching past her, and eats it. The young
may gape or flutter the tips of the wings briefly if the female holds the food
or moves away at first. At times the young hisses or squeaks as it is fed.
Larger, well-flying young hardly give the female a chance to rattle; they
follow or chase her with hissing notes and hitch up to her as soon as she
captures food. They gape at her head silently or with hisses. At times one
nibbles the back of the female. She is forced to flee their hissing pursuit
if she is to eat any food herself or even to forage in peace. Occasionally the
female chases away larger young or snaps at them when they follow her
closely. During feedings there is scarcely any display beyond gaping and
squeaking by the young; the parent chucks the food into the open gape and
bill-wipes or flies away.

Edwin O.
Willis

WOODCREEPER BEHAVIOR

413

Fig. 12. Wanderings of two young Plain-brown Woodcreepers, the offspring of female
RBYM, from September to November, 1961, and in 1962-1964 and 1971. Both young were
with the female in her territory (inside the dot-dash line) in September and October,
1961; thereafter, records of YGYG are underlined and of MGYY overlined.

On one occasion a female Plain-brown Woodcreeper called stick loudly
nearby when an Ocellated Antbird briefly pounced on her screaming young.
Females and juveniles sometimes sing back and forth when separated from
each other. When the observer passes a female and her grown young all often
start stieking and hide behind trees, and move off through the forest with
occasional songs or stick notes.

Sibling woodcreepers occasionally supplant each other, but they are
usually so widely separated around a swarm that there are no chances for
arguments at feeding times. In some of the broods I observed, the female
fed one sibling frequently while the other was ignored and began to forage
at an early age. This suggests that a female may sometimes have difficulty
feeding more than one fledgling.

Young birds beginning to forage for themselves peck and pry at debris
or even hit it on a perch as if to kill it; they examine epiphytes and nearby
trunks actively in a fashion reminiscent of woodcreepers of the genus

414

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Xiphorhynchus. One pecked at army ants (Eciton burchelli) , and dropped
them before fleeing with stiek notes. One tried backing down to a leaf-filled
cavity as if to bathe or cavity-sit, but missed the cavity. Later the young
woodcreepers wait more patiently and sally for prey in adult style.

The few birds banded as young wandered widely after leaving the female
and did not associate with her or with each other even if they returned to
her home area later (Fig. 12) . Occasionally a young bird supplants wandering
birds known to be older, although settled birds supplanted young birds in
most cases.

DISCUSSION

Of all the birds that follow army ants on Barro Colorado, the Plain-brown
Woodcreeper has the simplest and most individualistic social behavior. It is
plain in this aspect of behavior as it is in voice and plumage.

Parental bonds involve little interaction between birds, except for persistent
following of the parent by young birds. A long nestling period, typical of
cavity-nesting birds, perhaps allows young to be relatively independent soon
after they leave the nest. However, it seems more likely that having incon-
spicuous communication may protect young birds in a species that depends
to a considerable extent on hiding or fleeing from predators in open vege-
tation rather than on keeping in or near dense cover.

Care of nests by one parent obviates the need for displays between parents
and thus perhaps makes these open-cavity nesting birds even safer. Also, as
Smith (1968) has pointed out for chickarees (T amiasciurus spp.), the ab-
sence of the male means that there is one less animal to deplete food supplies
or frighten prey near the nest. Skutch (1969:407) records that a female
Tawny- winged Woodcreeper foraged actively near the nest in the evening;
if the Plain-brown Woodcreeper ever does this a male and female caring for
the nest together would compete rather strongly. Nesting Plain-brown Wood-
creepers apparently do not travel much to distant ant swarms, and probably
forage in areas near the nest on rather alert prey, such as lizards and cicadas;
two birds might scare such prey more than would one.

The sexual behavior of Plain-brown Woodcreepers also involves little
social display or interaction. Most birds with brief pair bonds have well-
developed courtship ceremonies, plumage, or voice. Darwinian sexual
selection, the necessity for correct recognition of a conspecific bird, and
competition between males should lead to hypertrophy of male sexual
behavior in such species. It is possible that insectivorous birds cannot develop
a lek or similar time-consuming system of strong courtship display because
their food is too widely dispersed or unpredictable (Snow, 1962). European
Cuckoos, a species with a social system most like that of Plain-brown Wood-

Edwin O.
Willis

WOODCREEPER BEHAVIOR

415

creepers, are also insectivorous. The necessity of not frightening alert prey
by having too many birds about, and of not attracting predators, may make
it advantageous to Plain-brown Woodcreepers to be retiring and inconspicuous
in courtship behavior.

These birds have not developed the strong or conspicuous aggressive and
submissive displays that would seem useful for establishment of dominance.
Instead, there are fighting and long chases that seem to waste time and energy.
Perhaps quick fights and unpredictable chases may reduce danger to birds
that forage in rather open forest midlevels or open lower levels most of the
time. Ignoring the opponent until there is a sudden chase makes maximum
benefit of the protective coloration until the last moment. Moreover, a de-
feated bird has plenty of room in which it can forage. Such birds can escape
in any direction from a dominant opponent or a predator. Ground-foraging
antbirds could trap and hurt each other if they were to use fighting instead
of displays. Thus the emphasis on displays instead of fighting in such species
as Bicolored Antbirds and the opposite emphasis in these woodcreepers may
reflect the ecological limitation of the former species to a narrow zone near
the ground and to areas near safe cover. The woodcreepers, by contrast, must
be fast at moving to unprotected sites not occupied by antbirds, and must
behave inconspicuously or unpredictably in such sites. If so, it would be
instructive to determine if the low-foraging woodcreepers on Trinidad, in an
area with few competing antbirds or predatory hawks, show a relatively
greater use of displays than do the woodcreepers on Barro Colorado. Another
factor is that woodcreepers are generally less numerous at swarms than are
Bicolored Antbirds; hence woodcreepers may have less need for frequent
displays to set up and maintain peck orders. Again, the woodcreepers are
very numerous at swarms on Trinidad and may use displays more.

Many patterns of submissive and evasive behavior are also inconspicuous
in Plain-brown Woodcreepers, but are rather well developed. It is a bird that
seems good at fleeing and hiding, whether from a competitor or from a
predator. Submissive calls include rattleting, persistent rattling, and to a
certain extent growling (which is more often a social call from fledgling
to parent or from one sex to another in courtship). There is no clearly ag-
gressive call, while in some antbirds the aggressive calls outnumber the sub-
missive ones. Even song is rare and seldom seems to have an aggressive or
territorial function in Plain-brown Woodcreepers.

The poor or inconspicuous development of forms of social behavior in
Plain-brown Woodcreepers may have been favored as a result of their foraging
behavior under conditions of competition with antbirds. These woodcreepers
forage mainly above the ground during periodic probes of ants up trees or
slip in and out at open and unsafe places where comj)eting antbirds hesitate

416

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

to go. Exploitation of such irregular sources of food at a swarm, in contrast
to the regular feast enjoyed by ground-foraging antbirds, must place a
selective premium on rapid movement of individuals. Antbirds, which lead
mates or young about, have special calls and must be very active to get the
mate or young to follow them to another part of a swarm. Not only is time
wasted, but other birds of the same or other species quickly home on the calls
and antics of the leading bird. Birds that work near the ground, where ants
flush food regularly, need seldom use this kind of behavior; but if wood-
creepers maintained close pair or parental bonds they would need it every few
minutes. It is far better for them to wander individually, quickly move in
at available sites as soon as they develop, and keep quiet so few competitors
are attracted.

One form of social behavior, stieking and hyperactivity in response to
predators, is well developed in Plain-brown Woodcreepers. Single wood-
creepers stiek as readily as ones together, and stieking generally causes birds
to scatter. Possibly the calling is a communication to the predator (“Here am
I, alerted and a difficult catch”), or a call that irritates or disturbs predators;
it may also drive off competing antbirds as has been suggested for a similarly
subordinate species on Barro Colorado (Willis, 1972). In the past, alarm
calls have often been assumed to be altruistic; stieking may also have such
a function in Plain-brown Woodcreepers, especially when a family is
together. Hamilton (1963) discusses how such “altruism” can evolve in
situations where related animals are together.

In contrast to ground-foraging antbirds. Plain-brown Woodcreepers use
the same call for terrestrial predators as for aerial predators. Probably
there is no reason to develop a separate call for ground predators when a
species normally forages well above the ground. Long rattling may represent
a type of predator call, perhaps one that irritates or disturbs a predator, but
this behavior is also used when a domineering competitor is present.

In contrast to most forms of social behavior, foraging and other types of
individual behavior are well developed in Plain-brown Woodcreepers. The
woodcreeper is peculiarly specialized in some ways and generalized in
others. The woodpeckerlike perching and hitching restrict it in many ways;
for instance, these woodcreepers tend to avoid perches below 3 cm in
diameter. A bird that perches like a woodpecker is also relatively slow at
catching prey below or behind it, and hence is at a disadvantage catching
prey near the ground. When better-adapted horizontally-clinging antbirds
are present, the woodcreeper scarcely uses the rich and constant source of
food on the ground (Willis, 1966). As a result, it is very generalized and
opportunistic in its vertical level of foraging. It uses wait-and-flycatch tech-
niques, but moves from the ground to near the tops of forest trees as oppor-

Edwin O.
Willis

WOODCREEPER BEHAVIOR

417

tunities arise. Since the Plain-brown Woodcreeper is a generalist in at least
two respects (variety of prey and level of foraging) but a specialist in others
(woodpeckerlike perching, wait-and-flycatch techniques, relatively frequent
attendance at swarms of army ants), it may be difficult to answer the question
(Klopfer, 1962), are tropical avifaunas more diverse because the species have
narrower niches? A species may have a niche that is narrow in one or more
dimensions but broad in other dimensions. However, the niche of the Plain-
brown Woodcreeper is broader on Trinidad, a “peripheral” tropical area with
few competing species of ant-following birds, in the sense that the woodcreeper
is more abundant there and catches a greater percentage of the total prey
items flushed by ants there than in Panama or Guyana (Willis, 1966).

Perhaps a simple objective way to say if a niche is broad or not is to see
if a species captures a greater percentage of the total prey or other resource
in a given area than does another species or does the same species in another
area. Even though the Plain-brown Woodcreeper “narrows” its foraging
niche on Trinidad by foraging mostly near the ground, the ground is such a
rich source of food over army ants that the woodcreeper actually gets more
prey and thus broadens its niche. It may lose to some extent the ability to
forage above the ground, but it is certainly exploiting more of the available
food supplies when competing antbirds are absent.

SUMMARY

Plain-brown Woodcreepers usually forage over swarms of army ants and capture
arthropods flushed by the ants. The woodcreepers occasionally forage away from ants,
at times with the wandering interspecific flocks of the forest interior. They generally
wait on vertical perches 1-10 m above the ground and sally like flycatchers to capture
orthopterans, roaches, spiders, and other prey from the vegetation or the air. When com-
peting antbirds are absent, the woodcreepers descend and capture prey on the ground
more frequently. They use “anting” and “wing-flashing” as foraging techniques; the
former behavior pattern apparently wipes harmful secretions off prey and the latter
flushes concealed prey.

Alarm behavior, especially fleeing and repetition of a loud call (“sticking”) is well
developed. In contrast, social behavior is as plain or inconspicuous as are voice and
plumage. Agonistic behavior is mainly confined to ignoring conspecific birds, to sudden
chasing, and to fighting. Submissive display is better developed but inconspicuous:
there is wing-quivering, also a rigid posture during a “rattling” call; aggressive display
is rarely seen. The relative lack of display or necessity for inconspicuous displays to
avoid predators and competitors may be the reason for an observed high frequency of
fighting, which in this species is perhaps not very dysgenic Ijecause the birds fight in
the relatively open middle levels of the forest where entrapment is difficult.

Settled females occupy exclusive areas, and seldom visit ant swarms outside tliese
areas. Settled males wander widely around the separate centers of their own areas; tlieir
mutually overlapping foraging areas overlap with but do not correspond to the foraging
areas of females. Settled females apparently dominate settled males occupying the same

418

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

regions. There is no permanent pair bond. For a few days at the time of mating an
individual female permits a male to come near her without fleeing or attacking. For a
time the two squabble vigorously, but the female finally submits to mounting after the
male “nibbles” her back repeatedly. “Cavity-sitting,” a behavior pattern in which the
two birds visit holes in stubs together, suggests that the pair association may extend for
a short time beyond copulation. It is possible that the insectivorous niche of the species,
and particularly its relatively irregular and marginal source of food, prevent evolution
of lek behavior or hypertrophy of male voice or other characters by sexual selection.

Nesting and care of young are tasks of the female. Begging and parental behavior are
inconspicuous. “Singing” is used when female and young are widely separated, as it
is when adult woodcreepers are alone and wandering away from swarms. A kind of
“rattlet” call notifies the young that the female has food. After a month or so the
juveniles leave the female and wander separately.

The individuality of these woodcreepers and their relative plainness of plumage, voice,
and social behavior may result from their irregularly available and exposed foraging
niche. The woodcreeper depends upon irregular sources of food, when ants probe above
the ground or when domineering antbirds happen to be absent near the ground. The
premium this places upon rapid movement of individuals perhaps precludes development
of pair bonds and parental behavior, which would require special calls and displays and
thus attract domineering competitors. Moreover, these woodcreepers are adapted for
using open sites in the forest midlevels and near the ground in places that antbirds
hesitate to go; to use such unsafe sites the woodcreepers apparently depend on incon-
spicuousness of plumage and behavior, or sudden and unpredictable moves to get prey or
chase competitors. They avoid fights with other species, or move in on them quickly
or with wing-shivering, perhaps so neither predators nor competitors will be attracted.
Individual woodcreepers seem successful at avoiding predation; some on Barro Colorado
were over 10 years old.

ACKNOWLEDGMENTS

Financial support was provided by fellowships from the Woodrow Wilson Foundation,
the National Science Foundation (including grants GB-21442 and GB-30776), the Frank
M. Chapman Fund of the American Museum of Natural History and Sigma Xi. The
staff of the Smithsonian Institution at Barro Colorado Island, of the William Beebe
Tropical Research Station at Simla, Trinidad, of the Rockefeller Virus Laboratory at
Bush-bush, Trinidad, and of the Compania Minera Choco-Pacffico at El Tigre, Colombia,
helped these studies greatly. Special thanks are due Ram S. Singh of the Georgetown
Museum for arranging my trips to Nappi Creek and Bartica, Guyana. I also appreciate
the help of curators at the American Museum of Natural History and the Museum of
Comparative Zoology, as well as a reading of the manuscript by Eugene Eisenmann.

LITERATURE CITED

Bock, W. J., and W. D. Miller. 1959. The scansorial foot of the woodpeckers, with
comments on the evolution of perching and climbing feet in birds. Amer. Mus.
Novitates, no. 1931.

Eisenmann, E. 1955. The species of Middle American birds. Trans. Linnaean Soc.
N.Y., 7:1-128.

Feduccia, J. a. 1969. Evolutionary trends in the avian families Furnariidae and Dendro-
colaptidae. Unpubl. Ph.D. Disser. Univ. Michigan.

Edwin 0.
Willis

WOODCREEPER BEHAVIOR

419

Feduccia, J. a. 1970. Natural history of the avian families Dendrocolaptidae (Wood-
hewers) and Furnariidae (Ovenbirds). Grad. Res. Center, Southern Methodist Univ.,
38:1-26.

Haffer, J. 1969. Speciation in Amazonian forest birds. Science, 165:131-137.

Hailman, j. P. 1960. A field study of the Mockingbird’s wing-flashing behavior and
its association with foraging. Wilson Bull., 72:346-357.

Hamilton, W. D. 1963. The evolution of altruistic behavior. Amer. Naturalist, 97:
354-356.

Johnson, R. A. 1954. The behavior of birds attending army ant raids on Barro Colo-
rado Island, Panama Canal Zone. Proc. Linnaean Soc. N.Y. 63-65:41-70.

Kelso, L., and M. M. Nice. 1963. A Russian contribution to anting and feather mites.
Wilson Bull., 75:23-26.

Klopfer, P. H. 1962. Behavioral aspects of ecology. Prentice-Hall, Englewood Qiffs,
New Jersey.

Meyer de Schauensee, R. 1970. A guide to the birds of South America. Livingston
Publ. Co., Wynnewood, Pa.

Moynihan, M. H. 1962. The organization and probable evolution of some mixed species
flocks of neotropical birds. Smithsonian Misc. Coll., 143:1-140.

Oniki, Y. 1970. Roosting behavior of three woodcreepers (Dendrocolaptidae) in
Brazil. Condor, 72:233.

Oniki, Y., and E. 0. Willis. 1972. Studies of ant-following birds north of the eastern
Amazon. Atas Amazonica, (In press).

Pinto, O. 1953. Sobre a colecao Carlos Estevao de peles, ninhos, e ovos de aves de
Belem (Para). Papeis Avulsos Dept. ZooL, Sao Paulo, 2:111-222.

Potter, E. F. 1970. Anting in wild birds, its frequency and probable purpose. Auk,
87:692-713.

Simmons, K. E. L. 1966. Anting and the problem of self-stimulation. J. Zook, 149:
145-162.

Sketch, A. F. 1969. Life histories of Central American birds HI. Pacific Coast
Avifauna, 35.

Slud, P. 1960. The birds of Finca “La Selva,” Costa Rica: a tropical wet forest
locality. Bull. Amer. Mus. Nat. Hist., 121:49-148.

Slud, P. 1964. The birds of Costa Rica. Bull. Amer. Mus. Nat. Hist., 128:1-430.

Smith, C. C. 1968. The adaptive nature of social organization in the genus of
three (sic) squirrels Tamiasciurus. Ecol. Monogr., 38:31-63.

Snow, D. W. 1962. A field study of the Black and White Manakin, Manacus manacus,
in Trinidad. Zoologica, 47:65-104.

Snow, D. W., and B. K. Snow. 1964. Breeding seasons and annual cycles of Trinidad
land-birds. Zoologica, 49:1-63.

Southern, W. E. 1963. Three species observed anting on a wet lawn. Wilson Bull.,
75:275-276.

Tinbergen, L. 1960. The natural control of insects in pinewoods. I. Factors influencing
the intensity of predation by songbirds. Arch. Neerl. Zook, 13:266-336.

Whitaker, L. M. 1957. A resume of anting, with particular reference to a captive
Orchard Oriole. Wilson Bulk, 69:195-262.

Willis, E. 0. 1960. A study of the foraging l)ehavior of two species of ant-tanagers.

Auk, 77:150-170.

Willis, E. 0. 1966. Interspecific competition and tlie foraging behavior of Plain-brown

Woodcreepers. Ecology, 47:667-672.

420

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Willis, E. 0. 1967. The behavior of Bicolored Antbirds. Univ. of Calif. Publ. Zool.,

79:1-132.

Willis, E. 0. 1972. The behavior of Spotted Antbirds. A.O.U. Monographs, 10.

appendix: names of birds in text

Antbird, Bare-crowned. — Gymnocichla nu-
diceps

Bicolored. — Gymnopithys bicolor
Black-headed. — Percnostola rufifrons
Chestnut-backed. — Myrmeciza exsul
Harlequin. — Rhegmatorhina berlepschi
Lunulated. — Gymnopithys lunulata
Ocellated. — Phaenostictus mcleannani
Rufous-throated. — Gymnopithys rujigula
Scale-backed. — Hylophylax poecilonota
Spotted. — Hylophylax naevioides
White-plumed. — Pithys albifrons
White-throated. — Gymnopithys salvini
Antshrike, Slaty. — Thamnophilus punctatus
Aragari, Collared. — Pteroglossus torquatus
Attila, Bright-rumped. — Attila spadiceus
Bare-eye, Black-spotted. — Phlegopsis nigro-
maculata

Reddish-winged. — Phlegopsis erythrop-

tera

Crane-Hawk. — Geranospiza caerulescens
Creeper, Brown. — Certhia familiaris
Cuckoo, European. — Cuculus canorus
Squirrel. — Piaya cayana
Flycatcher, Acadian. — Empidonax virescens
Streaked. — Myiodynastes maculatus
Forest-Falcon, Barred. — Micrastur rufi-

collis

Lined. — Micrastur gilvicollis
Ground-Cuckoo, Rufous-vented. — Neomor-

phus geoffroyi

Hawk, Semiplumbeous. — Leucopternis semi-
plumb ea

White. — Leucopternis albicollis
Kite, Double-toothed. — Harpagus bidentatus
Gray-headed. — Leptodon cayanensis

Hook-billed. — Chondrohierax uncinatus
Leaf scraper. Scaly-throated. — Sclerurus
guatemalensis

Mockingbird. — Mimus polyglottos
Motmot, Broad-billed. — Electron platyrin-
chum

Rufous. — Baryphthengus ruficapillus
Owl, Mottled. — Ciccaba virgata
Spectacled. — Pulsatrix perspi cill at a
Puffbird, Black-breasted. — Notharcus pec-
toralis

White- whiskered. — Malacoptila pana-
mensis

Sandpiper, Spotted. — Actitis macularia
Tanager, Gray-headed. — Eucometis penicil-
lata

Thrush, Swainson’s. — Hylocichla ustulata
Toucan, Chestnut-mandibled. — Ramphastos
swainsonii

Keel-billed. — Ramphastos sulfuratus
Warbler, Canada.- — Wilsonia canadensis
Woodcreeper, Barred. — Dendrocolaptes cer-
thia

Black-banded. — Dendrocolaptes picumnus
Black-striped. — Xiphorhynchus lachrymo-
sus

Buff-throated. — Xiphorhynchus guttatus
Hoffmanns’. — Dendrocolaptes hojfmannsi
Plain-brown. — Dendrocincla fuliginosa
Red-billed. — Hylexetastes perrotti
Ruddy. — Dendrocincla homochroa
Spix’s. — Xiphorhynchus spixii
Tawny- winged. — Dendrocincla anabatina
Wedge-billed. — Glyphorhynchus spirurus
White-chinned. — Dendrocincla merula
Woodpecker, Chestnut. — Celeus elegans

DEPARTMENT OF BIOLOGY, PRINCETON UNIVERSITY, PRINCETON, NEW JERSEY

08540, 21 JUNE 1971.

RED-TAILED HAWK POPULATIONS AND ECOLOGY
IN EAST-CENTRAL WISCONSIN

John M. Gates

This paper reports on a study of Red-tailed Hawk (Buteo jamaicensis)
populations, reproductive success, and food habits in relation to Ring-
necked Pheasants (Phasianus colchicus) in east-central Wisconsin. Informa-
tion on the Redtail and other species of raptors was gathered as one phase
of a population study of pheasants, concerned in part with pheasant mortality
and with the possible influence of Red-tailed Hawk predation on pheasant
survival (Gates, 1971). Although the Redtail is one of the most common
birds of prey occupying the farmlands of the Midwest, comparatively few
studies of its ecology have been published. In view of the alarming decline
in population exhibited by many falconiformes in recent years, particularly
in relation to biocides (Hickey, 1969), information on reproductive success
and population density for all birds of prey is urgently needed as a reference
point from which future population trends can be evaluated. Although Hickey
(1969) still regards the Redtail as having normal reproductive success, Seiden-
sticker and Reynolds (1971) have more recently uncovered evidence of post-
DDT eggshell thinning in this species in Montana.

STUDY AREA

Observations of raptor ecology were made from December, 1959, to August, 1965, on
the Waupun Study Area, a 42-square-mile tract in southwestern Fond du Lac County and
adjacent parts of Green Lake and Dodge counties, Wisconsin (latitude 43°45'N; longi-
tude 88° 53' W). The topography of the area is level to gently undulating, with 78 per
cent of the landscape under cultivation. Dairy farming is the principal farm enterprise;
major crops include corn, oats, and hay. Twenty-two per cent of the land area is un-
cultivated, consisting largely of wetlands (10 per cent) and permanent pasture (7 per
cent). Only 0.3 per cent of the area is covered by closed-canopy woodlots, predominantly
bur oak {Quercus macrocarpa) and black oak (Q. velutina) . Small groves of these species
also occur in many pastures and on wetland edges. Most of the woodlots, and about half
of the wetlands, are used to some extent for grazing. The most prevalent forms of wetland
vegetation include sedge meadow (principally Carex stricta) , canary grass {Phalaris
arundinacea) , and shrub swamps, the latter dominated by willow {Salix spp.) and dog-
wood {Cornus stolonifera; C. Purpusi) .

In the winter of 1958-59 (December through March), observations were also made on
the Springvale Study Area (15 square miles), approximately 3 miles northeast of the
area described above. Except for greater abundance of woodlots on the Springvale Area
(6 per cent), landscape features and cover composition were generally similar between
the two.

To the best of my knowledge, use of insecticides during the period of study was light.
I knew of only two crops that received regular foliar treatment — sweet corn (DDT) in
late summer for control of corn earworm and peas (Parathion) in early summer for control

421

422

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

of pea aphids. Collectively, these crops constituted about 12 per cent of the land area,
but treatment 4vas not applied to the total acreage in any one season and was highly
variable between years. Dicke (1960), quoted by Hickey (1961), reported that only 12
and 7 per cent, respectively, of the statewide acreage of these crops was treated in 1959.
These figures fall well in line with my subjective evaluation of the intensity of insecticide
use during the study, suggesting that Redtails at Waupun probably were not being heavily
contaminated by insecticides through the local food chain. Furthermore, since it appeared
that the adult segment of the population was to large extent non-migratoiy, I also doubt
that breeding birds were earning high levels of pesticide residues accumulated elsewhere.
Unfortunately, no egg or tissue analyses were available to support these conjectures,
however.

METHODS

On the Springvale Area in February, 1959, Red-tailed Hawk and Rough-legged Hawk
i Buteo lagopus) populations were determined by direct search. On the Waupun Area in
subsequent years, winter populations of these species were estimated by the car-count
method (^Craighead and Craighead, 1956). A 45-mile transect was driven by two obseners
on two or three closely spaced afternoons between mid- January and mid-Februar>*. Counts
were made on snow-covered ground, with -wind velocities below 10 mph, and temperatures
above 0° F. AU Redtails and Roughlegs observed on the ground, perched, or in flight
within 44 mile of the transect were recorded, giving approximately 50-per cent coverage
of the study area. The number of each species observed on successive runs was averaged
and doubled as an estimate of mid-winter population size. Because of the area’s open
terrain, near-level topography, and scarcity of large woodlots, this method probably gave
a reliable estimation of winter buteo numbers. The main criticism of the method was the
small number of censuses run. Successive counts for individual winters showed an average
variability of 41 per cent. Because each winter’s population estimate was accordingly
subject to considerable sampling error, attention in this paper is largely confined to the
mean level of popirlation for all winters of study combined.

inter population data for other birds of prey were obtained from a daily log of all
raptors sighted, from which the number of indiHduals was later inferred from the distribu-
tion of sight records. Sno-v\y Owls {Nyctea scandiaca) were so conspicuous that a complete
inventory of this species was doubtless obtained. Cooper’s Hawks {Accipiter cooperii)
and Homed Owls {Bubo virginianus) , by comparison, were more secretive, and estimates
for these species were necessarily regarded as minimum figures.

The breeding population of Red-tailed Hawks was determined over the 3-year period
1962-64 by systematic coverage of the Waupun Study Area for active raptor nests. Search
was conducted during late March and early April, either on foot or by scanning for
potential nest sites through binoculars and spotting scopes. Nests tended to be highly
conspicuous at this season, and I believe that a complete census of breeding pairs was
obtained. No estimate was made of the number of non-breeding Redtails on the area.

Redtail nests were periodically checked between the time of nest discover}- and the
time the young were fledged. After initially determining that eggs had been laid, no
nest trees were climbed until the young were hatched. Prey remains were identified at
each nest visit.

WINTER POPULATIONS

Red-tailed Hawks. — The estimated winter population of Redtails at aupun
varied from a high of 21 individuals in 1961—62 to a low of 9 in 1964—65

johnM. RED-TAILED HAWK POPULATION AND ECOLOGY 423

Estimates

Table 1

OF Midwinter Raptor Population Density
Central Wisconsin®

ON Two Study Areas

IN East-

Winter

Study area*^

Red-

tailed

Hawk

Rough-

legged

Hawk

Cooper’s

Hawk

Snowy

Owl

Homed

Owl

1958-59

Springvale

14

8

4

0

6

1959-60

Waupun (2)*^

19

21

-

-

-

1961-62

Waupun (2)

21

5

3

4

4

1962-63

Waupun (3)

17

28

2

2

5

1963-64

Waupun (3)

16

13

2

2

3

1964-65

Waupun (2)

9

13

3

3

4

® No raptor-census data available in 1960—61.

Springvale Study Area 15 square miles in size; Waupun Study Area 42 square miles.

Figures in parentheses represent the number of car-count census runs from which Red-tailed and
Rough-legged Hawk population estimates were derived.

(Table 1). The number of winter residents showed comparatively little
fluctuation between 1959 and 1964, during which period the average winter
density was 0.44 per square mile. On the Springvale Area, 14 Redtails were
censused in 1958-59, a density of 0.93 per square mile. Because of its larger
size and longer period of study, the Waupun Area probably furnished more
representative information on the density of wintering Redtails for the region.
These data show an average winter population of 0.39 per square mile based
on five seasons of field study.

In February, 1962, an immature Redtail was found dead where it apparently
had been struck and killed by a motor vehicle while feeding on the remains
of a road-killed cottontail rabbit [Sylvilagus floridanus) . Aside from this
single individual, all winter observations of Redtails in this study consisted
of adult (= red-tailed) birds. Orians and Kuhlman (1956) reported much
greater frequency of immatures wintering in Green County, Wisconsin. Four-
teen per cent of the Redtails they encountered consisted of immature individ-
uals as a 2-year mean. (Green County is located approximately 80 miles
south-southwest of the Waupun Study Area.)

In general, I believe that most of the wintering Redtails at Waupun were
mated pairs that eventually bred on the area. Two lines of evidence suggested
that the majority were permanent residents. (T ) The population of breeding
Redtails for the period 1962-64 (Table 2) was only eight birds greater (62
versus 54) than the corresponding population totals of the preceding winters
(Table 1). (2) In February and March of 1962 and 1963, seven Redtail pairs
were maintained under near-daily surveillance. After mid-February in both
years, each of these pairs was observed with increasing frequency in the
vicinity of old nest trees that were eventually occuj)ied. Five of the seven

424.

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 2

Summary of Red-Tailed Hawk Breeding Populations and Reproductive Performance,

Waupun Study Area

Year

Number of
active nests

Number of
successful nests

Total number
of young
fledged

Young
fledged per
successful
nest

Young
fledged per
nesting
attempt

1962

9

7

00

13

1.9

1.4

1963

10

7

(70)

11

1.6

1.1

1964

12

6

(50)

11

1.8

0.9

Totals and

means 31

20

(65)

35

1.8

1.1

“ Figures in parentheses represent the percentage of total active nests.

were observed one or more times at the nest site proper, and two were also
seen carrying nesting materials. No influx of migrant Redtails or other raptors
was noted during the period of these observations.

In California, Fitch et al. (1946) similarly reported that Redtail pairs were
permanently resident in definite hunting and nesting territories. Orians and
Kuhlman (1956), in Wisconsin, reported that resident birds were on territory
by the end of February; however, some migrants were also present that
traveled singly or in groups. In central Iowa, Weller (1964) most commonly
observed wintering Redtails in areas in which active nests were later located.

The winter density of Redtails in Green County, Wisconsin, averaged 0.46
per square mile in 1953-54 and 1954-55 (Orians and Kuhlman, 1956). On
a study area in Columbia and Dane counties, Wisconsin, the 3-year mean
density was 0.76 per square mile (Kabat and Thompson, 1963). All three
Wisconsin study areas on which winter Redtail censuses have been conducted
are located in roughly the southeastern quarter of the state. Available evidence
suggests that Redtails regularly winter in this region at densities approaching,
and locally exceeding, 0.50 per square mile. This compares with 0.37 per
square mile as the three-winter mean density observed by Craighead and
Craighead (1956) in southern Michigan.

Other raptors. — Midwinter population estimates of Rough-legged Hawks
tended to be highly variable (Table 1) . Comparatively small numbers of these
hawks were observed during the two winters of heaviest snowfall, 1958-59
and 1961-62. Since the Roughleg’s winter diet consists almost exclusively of
small mammals (Bent, 1937; Craighead and Craighead, 1956; and Weller,
1964), lower vulnerability of small-mammal prey with heavier snow cover
probably encouraged a higher percentage of these migrants to continue south-
ward. In both winters, my recollection is that larger numbers of Roughlegs
were present in early winter before build-up of heavy snow cover.

John M.
Gates

RED-TAILED HAWK POPULATION AND ECOLOGY

425

The minimum density of Cooper’s Hawks and Horned Owls at Waupun was
0.06 and 0.10 per square mile, respectively, as a 4-winter mean (Table 1).
On the Springvale Area in 1958-59, densities were 0.27 and 0.40 per square
mile. These differences in population level doubtless stemmed from the greater
abundance of wooded habitat on the Springvale Area.

Snowy Owls were present at Waupun each winter that an attempt was made
to estimate their numbers (Table 1). Occurrence of these owls over the short
period of study demonstrated no evidence of periodicity. Other birds of
prey observed in winter included one Sparrow Hawk {Falco sparverius) in
1962-63 and one Barred Owl (Strix varia) in 1963-64. Screech Owls {Otus
asio) were present in unknown numbers each winter of study. Short-eared
Owls {Asio flammeus) were found in several day-roosting concentrations as
large as 15 or 20 birds throughout the open winters of 1960-61 and 1963-64;
however, no more than five Shortears were believed present during any other
season of study.

Collectively, the average density of large raptors (Red-tailed Hawks, Rough-
legged Hawks, Cooper’s Hawks, Horned Owls, and Snowy Owls) in this study
was slightly less than 1.0 per square mile.

OBSERVATIONS ON WINTER ECOLOGY

Intraspecific interactions. — I observed no overt sign of intraspecific intoler-
ance between wintering Redtails; however, it was my definite impression that
the hunting ranges of individual pairs tended to be mutually exclusive. Out
of 41 birds encountered on winter car counts, 24 (58 per cent) were sighted
no more than 0.50 mile apart. This seemed to imply a high degree of aggrega-
tion in winter Redtail distribution, which could be explained by a tendency
for pairs to share home ranges that did not overlap those of other pairs.

One series of observations was particularly instructive on this point. In
mid-February of 1962, at which time over 2 feet of snow blanketed the area
and small-mammal prey were virtually invulnerable to avian predation, one
pair of Redtails over an 11-day span killed at least eight hen pheasants out of
a flock of 85-100 wintering birds. These pheasants were particularly vulner-
able to predation, since they were concentrated around a bait-trapping station
in a 0.15-acre grove of willow brush adjacent to several black willow {Salix
nigra) trees that made ideal hunting perches. It ultimately became necessary
to remove these hawks to continue pheasant trapping at the site, and on
17 February both members of the pair were trapped and dispatched. Three
days later, a single Redtail was perched at the site, and on 23 February it
too was captured and removed from the area. On 27 February, another pair
of Redtails appeared on the scene, whereupon pheasant trajjping was sus-
pended. I was able to recognize one member of this second pair by consj)icuous
plumage variation. Earlier in winter, this individual had been consistently

426

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

observed on a hunting range which centered approximately 1.7 miles north-
east. At least in this particular instance, it seemed clear that removal of the
original pair created a vacant hunting range that contained an attractive and
highly vulnerable food source, and that this vacuum was almost immediately
filled by individuals that were previously excluded from the site.

Interaction with pheasants. — Well before the conclusion of this study, I
came to regard the Red-tailed Hawk as a skilled and highly capable pheasant
predator. Out of 165 preyed-upon pheasants encountered in winter, 99 ( 61
per cent) were attributed to birds of prey. Of the 99, 50 were further assign-
able to individual species of raptor according to field sign described by
Einarsen (1956) or from actual observations made at the kill site: Redtails
28, Horned Owls 11, Cooper’s Hawks 9, and Roughlegs 2. At face value,
these records suggested that Red-tailed Hawks were responsible for 55 per
cent of all pheasants killed by avian predators and for 34 per cent of the
overall winter predation loss. Twenty-one of the 28 Redtail records consisted
of actual flushes from freshly made kills; in addition, I observed 2 successful
and 17 unsuccessful attempts by Redtails on pheasants. From these observa-
tions, I believe that pheasants were an important component of the Redtail’s
winter diet, even though the actual percentage they comprised was not estab-
lished through systematic food-habits investigation.

During the period 1959-65, winter (early January through late March)
mortality of Ring-necked Pheasant hens at Waupun averaged 27 per cent.
Predation accounted for 74 per cent of the winter loss (Gates, 1971), hence
the kill by Redtails could be estimated at 7 per cent of the January pheasant
population.

It is conceivable that this percentage was a somewhat inflated estimate.
Because birds of prey generally do not cache prey remains, I believe that field
evidence of avian predation tended to be more conspicuous than mammalian
predation, probably leading to an over-estimate of the proportionate pheasant
kill by raptors in general and Redtails in particular. Notwithstanding, I con-
clude that Red-tailed Hawks did in fact remove a substantial percentage of
the hen pheasants at Waupun during the winter period.

The overall predation rate on pheasants, and I believe the Redtail rate
individually, was highly variable between winters. During two winters of
heavy snow cover (1958-59 and 1961-62), predation losses were calculated
at 29 and 33 per cent, respectively, of the January population. Corresponding
figures during two winters of virtually snowless conditions (1960-61 and
1963-64) were 2 and 17 per cent, respectively, and during three winters of
intermediate snowfall (1959-60, 1962-63, and 1964-65) 13, 18, and 21 per
cent, respectively (Gates, 1971). Of the 28 pheasant kills attributable to
Redtails, 18 were recorded in 1958-59 and 1961-62.

RED-TAILED HAWK POPULATION AND ECOLOGY 427

During these particular winters, snow depths of 10 to 30 inches prevailed
for at least a 70-day span between 1 January and 31 March. Pheasants during
these periods were hard pressed for winter food and shelter, and virtually the
entire population was concentrated at only 14 sites on the study area that still
afforded protective cover. With small mammals well sheltered under the
heavy snow canopy, it was clear that Redtails were taking full advantage of
the increase in pheasant vulnerability. In February of 1962, for example,
13 out of 18 Redtails observed on winter car counts were sighted on hunting
perches or in flight in the immediate vicinity of a pheasant concentration
site. Although I could not measure the impact of Redtail predation on pheas-
ants by individual winter of study, 1 conclude that it was highly variable
between years, and that higher rates of pheasant loss resulted from a shift
in food habits and hunting behavior as the small-mammal portion of the prey
base became increasingly invulnerable with deeper snow cover.

Recent studies have characterized the Redtail as a versatile and highly
adaptable predator, one capable of exploiting a wide variety of prey species
(Craighead and Craighead, 1956; Orians and Kuhlman, 1956; and Luttich
et ah, 1970). For this reason, it doubtless enjoys considerable flexibility in
adjustment of food habits to changes in prey vulnerability, at least in com-
parison with the more specialized feeders, e.g., the Rough-legged Hawk, which
appears to be primarily a small-mammal specialist. The Redtail’s ability to
switch over to larger prey, including pheasants, during periods of heavy snow
may be an important factor in this species’ ability to successfully winter year
after year in regions as far north as Waupun.

BREEDING POPULATIONS

Red-tailed Hawk. — The average number of active Redtail nests at Waupun
during the breeding seasons of 1962-64 was 10.3, equivalent to one pair per
4.1 square miles or 0.54 breeding adults per square mile per year (Table 2).
This was regarded as a minimum density, however, since no attempt was
made to determine the number of non-breeding birds that may have been
present. Of the 31 nesting pairs under observation, 30 comprised both adult
(= red-tailed) individuals. The single remaining pair consisted of one adult
paired with an apparent yearling (= brown-tailed) bird. The sex of the latter
individual was unknown.

Breeding densities of the Redtail at Waupun were generally lower than
reported elsewhere. In California (Fitch et ah, 1946), New York (Hagar,
1957), Green County, Wisconsin (Orians and Kuhlman, 1956), and Alberta
(Luttich et ah, 1971), the number of breeding pairs averaged one per 0.5,
2.2, 2.8, and 2.7 square miles, respectively.

Other raptors. — One Horned Owl nest was found in 1963 and 1964; no

428

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

nests of this species were found in 1962. Even though search for raptor nests
may have been undertaken too late in the year for a complete inventory of
Horned Owls, my conclusion was that the breeding density of this species at
Waupun was extremely low. A sufficient amount of field work was conducted
in February and March each year that I believe that most, if not all. Horned
Owl nests would have been discovered before the spring search. Scarcity of
woodlots at Waupun seemingly represented poor breeding habitat for this
species. Many of the owls present in winter probably were non-breeding
individuals.

BREEDING SEASON ECOLOGY

Nest sites. — Nineteen out of 31 Redtail nests under observation were situated
in black oaks, five in bur oaks, three each in American elms {Ulmus amer-
icana) and black willows, and one in quaking aspen {Populus tremuloides) .
Only four of the 31 were located in closed-canopy woodlots. Eighteen occurred
in open groves, generally less than one acre in size, and nine were situated
in isolated trees along fencelines and ditchbanks. Aside from a single nest
in an aspen swamp, all nest trees were located on w^ell-drained upland sites.

Reproductive success. — A nesting attempt was considered successful if at
least one young eventually fledged. Of the 31 nests in which eggs were laid
in 1962-64, 20 (65 per cent) succeeded (Table 2). The cause of nest failure
was known for only six of the 11 unsuccessful nesting attempts. Three were
partly dismantled and blown down by high winds in 1964, two were destroyed
by unidentified predators, and one failed when one of the adults w^as shot.

A total of 35 young were fledged from the 20 successful nests, an average
of 1.8 young per successful clutch. Seven of the 20 nests produced one
fledgling apiece, 11 produced two fledglings, and two produced three fledged
young. The rate of fledging success at Waupun compared favorably with
populations investigated elsewhere. In southern Wisconsin, the mean was
1.9 young per successful nest (Orians and Kuhlman, 1956) ; in New York,
1.9 (Hagar, 1957) ; in Montana, 1.7 ( Seidensticker and Reynolds, 1971) ;
and in Alberta, 1.4 (Luttich et ah, 1971). 1 made no attempt to determine
clutch size, nor brood size at hatching, for each of the nests under observation,
hence information was not available on rates of egg mortality or nestling
survival. From the average number of fledged young per successful clutch,
however, rates of rearing success at Waupun appeared satisfactory.

The overall rate of reproductive success was 1.1 fledged young per breeding
pair. Based on North American productivity and mortality data for the Red-
tail, Henny and Wight (in press) concluded that between 1.3 and 1.4 young
must be raised per nesting attempt to maintain a stationary population. At
Waupun, it might therefore be inferred that Redtail productivity was inade-
quate for population maintenance. If so, the problem seemed to center on

j^ohn M. RED-TAILED HAWK POPULATION AND ECOLOGY 429

Gates

the high rate of nest failure, since rearing success was very near the maximum
recorded in the literature. Orians and Kuhlman (1956) reported 1.4 young
raised per breeding pair in southern Wisconsin during 1953 and 1954.

Summer food habits. — Nineteen species were represented among the aggre-
gate prey remains identified at seven Redtail nests (Table 3). These seven
nests were visited at approximately weekly intervals between hatching and
fledging. It is possible, however, that prey remains were collected too infre-
quently for a completely unbiased sample of summer food habits. Fitch et al.
(1946) reported that adult Redtails sometimes remove unused prey items
from the nest site, and English (1934) observed that smaller animals, partic-
ularly mice, were often eaten without leaving trace. Of the prey species listed
in Table 3, I suspect that Microtus, passerine birds, and invertebrates were
somewhat under-represented in the food-habits sample.

The five leading items of prey, which accounted for 63 per cent of the
observed nesting-season diet, consisted of pheasants (23 per cent), Microtus
(17 per cent), cottontail rabbits (11 per cent). Red- winged Blackbirds (8
per cent), and domestic chicken (5 per cent). Birds constituted 58 per cent
of the observed diet by frequency of occurrence, mammals 38 per cent, and
invertebrates 5 per cent.

Most other studies have revealed a higher incidence of mammalian prey
than I observed in the Redtail’s summer diet at Waupun. In Wyoming (Craig-
head and Craighead, 1956), Alberta (Luttich et al., 1970), and Michigan
(Craighead and Craighead, 1956), mammals accounted for 93, 66, and 40
per cent, respectively, of the prey species taken. In southern Wisconsin, 85
per cent of diet reported by Errington (1933) consisted of mammals, among
which thirteen-lined ground squirrels, Microtus, and cottontail rabbits were
most important. The nesting-season prey of a single pair of Redtails observed
in Michigan by English (1934) included 76 per cent mammals and 24 per
cent birds.

It is interesting to note the close correspondence between Redtail food habits
at Waupun and those observed in Green County by Orians and Kuhlman
(1956). From evidence at nest sites, pheasants in their study also ranked as
the leading item of prey (33 per cent), followed by cottontail rabbits (19
per cent), domestic chicken (14 per cent), crows (6 per cent), and Microtus
(6 per cent). Sixty-five per cent of the nesting-season diet was made up of
birds and 35 per cent of mammals.

To my knowledge, these two studies provide the only available information
on Redtail food habits in areas that also represent good pheasant habitat.

I Green County, at the time of Orians and Kuhlman’s investigation, was an area
! of comparative pheasant abundance by Wisconsin standards, as was the Wau-
I pun Area during the course of the present study. Although mammals seem

430

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 3

Frequency of Occurrence of Prey Remains Collected at
Nests, Waupun Study Area, 1963-64

Seven Red-Tailed Hawk

Item

Number

identified

Per cent
occurrence

Birds

Ring-necked Pheasant {Phasianus colchicus)

40

22.7

Red- winged Blackbird (Agelaius phoeniceus)

14

8.0

Domestic Chicken

9

5.1

European Partridge {Perdix perdix)

5

2.8

Crow {CoTvus brachyrhynchos)

5

2.8

Yellow-shafted Flicker (Colaptes auratus)

4

2.3

Mourning Dove {Zenaidura macroura)

3

1.7

Common Crackle (Quiscalus quiscula)

3

1.7

Catbird (Dumetella carolinensis)

2

1.1

Blue Jay (Cyanocitta cristata)

2

1.1

House Sparrow (Passer domesticus)

1

0.5

Unidentified passerine remains

14

8.0

Mammals

Meadow mouse (Microtus spp.)

29

16.5

Cottontail rabbit (Sylvilagus floridanus)

19

10.8

Thirteen-lined ground squirrel (Citellus tridecemlineatus)

8

4.5

Muskrat (Ondatra zibethicus)

4

2.3

Fox squirrel (Sciurus niger)

4

2.3

Norway rat (Rattus norvegicus)

2

1.1

Invertebrates

Unidentified beetle remains (Coleoptera)

3

1.7

Unidentified crayfish remains (Astacidae)

5

2.8

Totals

176

99.8

to predominate in the Redtail’s diet over much of its North American range,
it is clear that this hawk is capable of exploiting pheasants as a major part
of the spring and summer diet when this prey species is available in reasonable
numbers.

Interaction with pheasants. — In 1963 and 1964, an attempt was made to
determine the rate of predation on pheasants by nesting Redtails. Two proce-
dures were relied upon. First, the number of marked hen pheasants recovered
at Redtail nests was compared with the number of marked individuals present
on the study area on 1 May. Pheasant marking was accomplished by leg
bands and backtags. Pheasants were captured by autumn nightlighting and
winter bait trapping, and estimates were made each year of the number of

RED-TAILED HAWK POPULATION AND ECOLOGY 431

marked hens surviving on the area on 1 May (Gates, 1971) . As an alternative
procedure, the total number of hen pheasants identified at Redtail nests,
including both marked and unmarked individuals, was compared with the
1 May census total for the study area at large.

In both years of study combined, 13 Redtail nests produced young and were
periodically checked for pheasant marks. Twenty-seven sets of leg bands
and/or backtags appeared at these sites, 6 per cent of the 443 marked indi-
viduals that I estimated to be alive on the area on 1 May. A total of 81 hen
pheasants was represented among the aggregate prey remains identified. The
1 May hen population for the area in 1963-64 was 1,863, from which a
predation rate of 4 per cent was calculated.

For two reasons, these percentages could not be accepted as unbiased esti-
mates: (1) It is conceivable that backtagged pheasants were more vulnerable
to Redtails than unmarked birds, which may have accounted in part for the
higher rate of exploitation indicated by the first as compared with the second
method. (2) In addition, proof was obtained that some of the pheasant hens
whose remains appeared at Redtail nests had originally died or were seriously
injured by mortality factors other than hawk predation. Leg bands from one
marked hen that I initially found as a freshly made kill at the entrance to an
active fox den I later recovered beneath a Redtail nest. Two other backtags
were found at Redtail nests which belonged to hayfield-nesting hens that I
knew had lost at least one leg as a result of hay-mowing accidents (the identity
of these birds was established from leg bands attached to amputated legs at
the nest site). The fact that some of the apparent Redtail kills actually
represented carrion, and that certain other hens were severely incapacitated
before being preyed upon, meant that both methods of calculation probably
led to a somewhat exaggerated estimate of the rate of Redtail predation.

On the other hand, these findings applied exclusively to the nestling period
when adult Redtails were rearing young. No allowance was possible for
pheasants preyed upon outside the nesting season, nor for the kill by unsuccess-
ful or non-breeding pairs. On balance, I conclude that Red-tailed Hawks prob-
ably removed close to 5 per cent of the spring population of pheasant hens
in 1963-64.

The following figures perhaps provide some perspective in evaluating the
overall impact of Redtail predation on pheasants. The average annual mor-
tality rate of hen pheasants in this study between 1 October and 30 September
was 76 per cent (Gates, 1971). Of those hens surviving in early January in
an average winter, 27 per cent died before the end of March. Calculations
suggested that a maximum of 7 per cent of the January |)opulation, or 26 per
cent of all hens dying during the interval, were preyed upon by Redtails.
Among those hens surviving on 1 May, 41 ]>er cent disappeared by early

432

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

August (Gates, 1971). The estimated rate of Redtail predation on the 1 May
population was approximately 5 per cent, equal to 12 per cent of the total loss.

Because predation rates were measured at only two seasons of the year, it
is impossible to assess quantitatively the year-round importance of Redtail
predation. I believe that this study has conclusively demonstrated, however,
that where Red-tailed Hawks and Ring-necked Pheasants coexist, pheasants
may comprise a significant proportion of the Redtail’s winter and nesting-
season diet, and that Redtail predation, in turn, may account for an appreciable
fraction of the losses sustained by a pheasant population at these seasons.
Under conditions of the present study, the number of pheasants killed by
Redtails was nevertheless a modest fraction of total mortality, and the possible
role of Redtail predation in regulation of pheasant density would have to be
evaluated in context of other mortality factors which collectively accounted
for a much larger proportion of total deaths.

SUMMARY

A study of Red-tailed Hawk populations, ecology, and predation on Ring-necked Pheas-
ants was conducted in east-central Wisconsin in 1959-65. The average winter density of
Redtails on a 42-square-mile tract was 0.39 per square mile; the average breeding density
over a 3-year span (1962-64) was 0.54 per square mile. Wintering Redtails consisted
almost exclusively of adults, the majority of which appeared to be paired and permanently
resident.

Redtail nest success was 65 per cent, and the average number of young fledged per
successful clutch was 1.8. The overall rate of productivity was 1.1 fledged young per
breeding pair, well below the threshold of 1.3 to 1.4 young reportedly required for popula-
tion maintenance in this species (Henny and Wight, in press). Rearing success was close
to the maximum reported in the literature, the main limitation to breeding success being
the high rate of nest mortality prior to hatching.

Pheasants were the leading item of prey in an analysis of spring and summer food
habits. Pheasants were also preyed upon in winter, but the percentage they comprised
of the winter diet, though considered substantial, was not quantitatively evaluated. Over
a seven-winter period (1958-65), Redtails removed an estimated 7 per cent of the hen
pheasant population between early January and late March. In 1963-64, Redtail predation
during the spring and summer period was estimated at 5 per cent of the 1 May population.
Under conditions of the present study, it was concluded that the Red-tailed Hawk was
a highly capable predator on pheasants, and that Redtail predation accounted for a
significant percentage of year-round pheasant mortality.

ACKNOWLEDGMENTS

I am indebted to the following persons for assistance in various phases of field work:
G. F. Martz, A. E. Loomans, G, E. Ostrom, and the late F. V. Holzer. This investigation
was supported by the Wisconsin Department of Natural Resources, financed in part
through Federal Aid to Wildlife Restoration funds under Pittman-Robertson Projects
W-78-R and W-141-R. I am indebted to J, B. Hale and L. R. Petersen for review of the
manuscript.

RED-TAILED HAWK POPULATION AND ECOLOGY 433

LITERATURE CITED

Bent, A. C. 1937. Life histories of North Ameriean birds of prey (Part I). U.S. Natl.
Mus. Bull., 167.

Craighead, J. J., and F. C. Craighead, Jr. 1956. Hawks, owls and wildlife. Stackpole
Co., Harrisburg, Pennsylvania, and Wildlife Management Institute, Washington, D.C.

Einarsen, a. S. 1956. Determination of some predator species by field signs. Oregon
State Monogr., Studies in Zoology. No. 10.

English, P. F. 1934. Some observations on a pair of Red-tailed Hawks. Wilson Bull.,
46:228-235.

Errington, P. L. 1933. Food habits of southern Wisconsin raptors. Part II. Hawks.
Condor, 35:19-29.

Fitch, H. S., F. Swenson, and D. F. Tillotson. 1946. Behavior and food habits of the
Red-tailed Hawk. Condor, 48:205-237.

Gates, J. M. 1971. The ecology of a Wisconsin Pheasant population. Unpubl. Ph.D.
Thesis, Univ. Wisconsin, Madison, Wisconsin.

Hagar, D. C., Jr. 1957. Nesting populations of Red-tailed Hawks and Horned Owls in
central New York state. Wilson Bull., 69:263-272.

Henny, C. j., and H. M. Wight. In press. Red-tailed and Cooper’s Hawks: Their pop-
ulation ecology and environmental pollution. Symposium on the population ecology
of migratory birds. Patuxent Wildlife Research Center. (Original not seen; cited by
Luttich et ah, 1971.)

Hickey, J. J. 1961. Some effects of insecticides on terrestrial birdlife in the Middle
West. In Report of the Subcommittee on Relation of Chemicals to Forestry and Wild-
life for the State of Wisconsin. Madison, Wisconsin.

Hickey, J. J. 1969. Peregrine falcon populations: Their biology and decline. Univ.
Wisconsin Press, Madison, Wisconsin.

Karat, C., and D. R. Thompson. 1963. Wisconsin quail 1834-1962/Population dy-
namics and habitat management. Wisconsin Conservation Dept. Tech. Bull. No. 30.

Luttich, S., D. H. Rusch, E. C. Meslow, and L. B. Keith. 1970. Ecology of Red-tailed
Hawk predation in Alberta. Ecology, 51:190-203.

Luttich, S. N., L. B. Keith, and J. D. Stephenson. 1971. Population dynamics of the
Red-tailed Hawk (Buteo jamaicensis) at Rochester, Alberta. Auk, 88:75-87.

Orians, G., and F. Kuiilman. 1956. Red-tailed Hawk and Horned Owl populations in
Wisconsin. Condor, 58:371-385.

Seidensticker, j. C., IV, and H. V. Reynolds, HI. 1971. The nesting, reproductive
performance, and chlorinated hydrocarbon residues in the Red-tailed Hawk and Great
Horned Owl in south-central Montana. Wilson Bull., 83:408-418.

Weller, M. W. 1964. Habitat utilization of two species of buteos wintering in central
Iowa. Iowa Bird Life, 34:58-62.

WILDLIFE RESEARCH SECTION, STATE OF WISCONSIN DEPARTMENT OF NATURAL
RESOURCES, MADISON, WISCONSIN 53701 (PRESENT ADDRESS: DEPARTMENT

OF WILDLIFE AND FISHERIES SCIENCES, SOUTH DAKOTA STATE UNIVERSITY,
BROOKINGS, SOUTH DAKOTA 57006), 20 MARCH 1972.

PREDATOR-PREY RELATIONSHIPS AND REPRODUCTION
OF THE BARN OWL IN SOUTHERN TEXAS'

Lee C. Otteni, Eric G. Bolen, and Clarence Cottam

This study was designed to reveal the ecological interactions existing
between the food habits and breeding of Barn Owls {Tyto alba) in
southern Texas. Specific areas of investigation included determination of
(a) Barn Owl food habits, (b) relative abundance of prey populations, and
(c) Barn Owl nesting biology. Certain portions of the study began in 1965,
whereas intensive field work was initiated and continued in 1969 through
1971.

STUDY AREA

Field work was conducted on the Rob and Bessie Welder Wildlife Foundation (hereafter
referred to as the Welder Refuge), eight miles northeast of Sinton, San Patricio County,
Texas. The Welder Refuge covers 7,800 acres of a broad ecotone between the Coastal
Prairies and Rio Grande Brushlands. The region supports a complex biota of nearly 1,400
flowering plants and more than 500 animal species. A subhumid climate prevails; hot
summers and mild, short winters are characteristic together with frequent late summer
and fall hurricanes. Rainfall averages about 31 inches per year, but the fluctuation
between years is highly variable with the extremes, rather than the average, influencing
the permanent vegetation.

Box and Chamrad (1966) described the soils and plant communities of the area. The
vegetation can be generally considered a brush-grass complex developing on (a) clay and
clay loam sites, (b) sandy and sandy loam sites, (c) bottomland sites, and (d) semi-
permanent lake sites. Our work centered on eight of the major plant communities present
at the Welder Refuge.

METHODS

Capture and handling of owls. — Most adult Barn Owls were caught in nest boxes erected
throughout the Welder Refuge. Snares set on top of the nest boxes were also used if
the resident owl could not be captured inside the box. Nesting owls were returned to
the box and detained for several minutes by blocking the entrance hole. This usually
was sufficient to calm the bird and inhibit its flushing.

Adult owls were banded with standard aluminum leg bands. Juveniles of sufficient size
were also banded. The sex of adults were determined only during the breeding season
by cloacal examination. The female Barn Owl develops an incubation patch and, if still
in the laying period, also has an enlarged, reddened vent. No reliable method was other-
wise found to determine the sex of either adult or immature owls.

Periodic inspection of the nest boxes yielded information on clutch size, nesting success,
breeding chronology, and general nesting behavior.

Analysis of owl foods. — Barn Owl foods were determined from an examination of pellets
collected on a monthly basis from nest boxes and roost sites. The analysis included the

^ Contribution No. 151, Rob and Bessie Welder Wildlife Foundation, Sinton, Texas.

434

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

435

frequency (percentage) and the minimum number of prey items in the pellets. Prey
species were identified by comparison with museum specimens and by the mammalian
skull key developed by Glass (1951). Bones from birds were compared with specimens
at the U.S. National Museum.

Prey census. — Small mammal populations were estimated in eight of the major plant
communities described in part by Box and Chamrad (1966) : Bunchgrass-Annual Forb;
Mesquite-Buffalograss; Chaparral-Bristlegrass; Pricklypear-Shortgrass ; Paspalum-Aquatic
Weed; Live Oak-Chaparral; Annual Forb Disclimax (i.e. disturbed sites) ; Texas Winter-
grass Stands.

Trapping stations at 25-foot intervals formed a grid of eight by six trap lines. Trapping
periods consisted of 48 traps checked for three consecutive nights. Sex, age, species, and
trapping station were recorded for each captured mammal which was ear-tagged and
released at the point of capture. The composition and relative abundance of each popula-
tion were determined using the marking-and-recapture method (Davis, 1959). Details
of the habitat preferences and other ecological aspects of the small mammal populations
not directly relevant to the present study are as yet unpublished.

The blackbird population, consisting of Red-winged Blackbirds (Agelaius phoeniceus) ,
Boat-tailed Crackles {Cassidix mexicanus) , Brown-headed Cowbirds (Molothrus ater) ,
and Bronzed Cowbirds {Tangavius aeneus) , was also estimated with the mark-and-release
method. Large (5 X 16 X 18 feet) poultry-wire decoy traps containing live decoy birds,
food, and water were used to capture blackbirds.

RESULTS

Dynamics and composition of prey populations. — No attempt was made to
fully estimate the rodent densities on the Refuge because of non-random
sampling bias inherent in the trapping procedure (cf. Krebs, 1966). Instead,
the objective was to measure trends important to the availability of prey to
Barn Owl predation. Trap success provided an adequate measure for these
fluctuations (Table 1).

Rodent populations declined from the summer of 1969 to the following
winter and spring of 1970 (Table 1). The lowest level of trapping success
was reached in May 1970, and thereafter it increased to 48 per cent success
in the fall of 1970. This peak was again followed by a period of decline that
stabilized during the winter and spring of 1971.

In 1969, prior to live trapping, small mammals were snap-trapped in the
major plant communities to gain a cursory view of the composition of the
rodent population. The results showed the highest percentage of rats found
during the duration of the study (Table 2). Following the summer of 1969,
the rat population declined to less than 1 per cent of the catch.

Mice dominated the catch throughout the study; they varied from 78 to
99 per cent of the overall rodent population, d'hese data indicate that the
decline in the rodent population was strongly influenced by a disproportionate
reduction in the rat populations that was not accompanied l>y marked losses
of mice.

436

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fluctuations in

Table 1

Rodent Populations as Shown by
Refuge, 1969-1971

Trap Success, Welder Wildlife

Date

Number

Traps set Traps entered

Percentage
trap success

July, 1969

540

154

28.5

January, 1970

288

37

12.8

February, 1970

192

24

12.5

March, 1970

288

57

19.8

April, 1970

288

26

9.0

May, 1970

864

17

1.9

June, 1970

2,160

83

3.8

July, 1970

1,296

84

6.5

August, 1970

2,160

178

8.2

November, 1970

288

139

48.3

January, 1971

2,160

388

19.3

February, 1971

432

83

19.2

March, 1971

1,584

351

22.2

May, 1971

1,584

299

18.9

Total

14,124

1,920

X = 13.6

Blackbird populations. — Our estimates indicate that about 50,000 resident
and migratory blackbirds roosted each winter in sites dominated by round-
stem rushes {Scirpus californicus) . The spring and summer population was
estimated at 15,000 birds. The population included Red-winged Blackbirds
and lesser proportions of cowbirds and grackles.

An attempt to measure the rate at which Barn Owls preyed on the blackbird
population employed the methods of Southern (1955). Birds were trapped,
banded, and released, and although 2,413 blackbirds were marked, no bands
were subsequently recovered from the owl pellets. Thus it was not possible
to directly assess the proportion of blackbirds taken as prey by the owls.
However, as noted above, the availability of blackbirds was never limited.

Bias in Barn Owl food habits studies. — Barn Owls as well as many other
species of raptors, regurgitate pellets of bone, feathers, and fur. These form
in response to the mechanical barrier posed by a small pyloric opening (Reed
and Reed, 1928) ; the materials are ejected in virtually an undigested mass
because of the absence of free acidity in the owl stomach. Hence, examination
of the pellets generally provides a reliable technique for determination of owl
food habits. However, at least two sources of error may occur. First, there
is the potential failure to collect one of the two pellets usually formed in each
24-hour period. A small pellet is formed and regurgitated during the night

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

437

Table 2

Percentage Composition of Live- and Snap-Trapped Small Mammals, Welder Wild-
life Refuge, 1969-1971

1969 1970 1971 Total

individ-

Species Summer Winter Spring Summer Fall Winter Spring uals

Pigmy Mouse

72.7

89.9

82.5

85.1

94.9

82.6

91.6

1,749

Harvest Mouse

4.1

9.3

4.8

3.8

1.4

14.9

6.4

184

Deer Mouse

1.0

—

6.3

3.4

—

1.5

1.0

15

Hispid Pocket Mouse

—

—

—

0.7

—

—

—

2

House Mouse

—

—

0.8

—

—

0.1

0.3

3

Sub-total

77.8

99.2

94.4

93.0

96.3

99.1

99.3

1,953

Wood Rat

9.6

0.8

0.4

—

—

—

30

Rice Rat

8.3

—

1.6

0.4

1.4

—

—

29

Cotton Rat

—

0.8

2.4

2.7

—

0.1

0.3

12

Sub-total

17.9

0.8

4.8

3.5

1.4

0.1

0.3

71

Least Shrew

4.1

—

0.8

3.4

2.2

0.6

0.7

32

Total Individuals

290

118

126

262

139

822

299

2,056

while the birds are still foraging whereas a second and larger pellet is deposited
at the diurnal roost (Guerin, in Wallace, 1948:25). In our study, the nesting
boxes were the sites of diurnal roosting so that we were able to collect and
examine only these pellets and not those scattered elsewhere. Secondly, errors
may occur when soft-bodied foods (invertebrates, nestling birds, etc.) were
eaten (Glading et ah, 1943) . These foods may be overlooked or not accurately
identified. Errington (1932) noted that the foods of very young owlets may
be masked because of their temporary proficiency at digesting calcium and
thus dissolving many of the bones otherwise diagnostic of their food habits.

Year-to-year variation in Barn Owl foods. — Variations in fundamental
predator-prey interactions due to environmental factors often complicate a
full understanding of Barn Owl food habits. Physical changes in the habitat
(floods, rainfall, etc.) as well as biological changes have much to do with
the pressure exerted on prey populations (Craighead and Craighead, 1956:
147). However, we are able to evaluate the Barn Owl diet in southern Texas
over a seven year period, 1965—1971, inclusive, using the pellet analysis
technique. This method permits us to determine the frequency of each prey’s
occurrence in the diet, but not directly, determination of either volume or
availability.

Mice represented 4,715 or 40 per cent of the 11,625 items identified as
owl foods. The species included pigmy mice {Baiomys taylori) , fulvous

438

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Percentage Frequency for

Table 3

Barn Owl Foods on the Welder Wildlife Refuge,
1965-1971

Species

1965

1966

1967

1968

1969

1970

1971

Mammals

White-footed Mice

1.3

1.8

1.5

3.5

2.0

2.2

0.6

Pigmy Mice

27.5

23.7

8.6

2.6

14.8

30.0

20.0

Fulvous Harvest Mice

12.9

30.9

5.7

2.0

2.5

2.0

5.1

Pocket Mice

31.1

5.2

3.3

0.5

1.8

1.2

—

Mice Sub-total

72.8

61.6

19.1

8.6

21.1

35.4

26.7

Cotton Rat

2.3

14.0

20.8

9.2

12.9

11.1

2.0

Riee Rat

1.1

1.2

2.2

5.7

17.7

7.1

5.4

Wood Rat

—

1.1

12.1

25.9

1.6

0.7

—

Rat Sub-total

3.4

16.3

35.1

40.8

32.2

18.9

7.4

Least Shrew

10.0

11.9

9.8

9.0

24.5

24.0

34.0

Cottontail

1.4

4.4

7.6

4.3

0.1

0.7

0.4

Poeket Gopher

7.1

2.7

8.7

2.4

0.5

0.4

0.8

Unidentified

4.2

—

0.2

0.4

1.7

—

Mammal Sub-total

98.9

96.9

81.4

65.5

80.1

79.6

69.3

Birds — Roosting

Over Water

—

1.0

13.7

17.2

13.4

16.4

17.0

Over Land

1.1

1.6

4.4

17.1

3.2

1.3

3.3

Bird Sub-total

1.1

2.6

18.1

34.3

16.6

17.7

20.3

Insects

Grasshopper

—

0.3

1.0

—

2.6

2.6

10.4

harvest mice {Reithrodontomys fulvescens) , white-footed mice [Per omy sens
leucopus) , and hispid pocket mice [Perog,nathus hispidus) . Of these, all but
white-footed mice were subject to pronounced fluctuations in the owl diet
during the seven year period (Table 3). A crash in the mouse populations
was particularly noticeable in 1968, following the earlier (October 1967)
inundation by Hurricane Beulah.

Gray wood rats [Neotoma micropus) ^ rice rats [Oryzomys palustris) , and
cotton rats [Sigmodon hispidus) represented 21 per cent (2,430 individuals)
of the diet. Gray wood rats were not present in the pellets in 1965, nor were
they important in 1966. Their numbers began to increase in 1967 (12 per
cent of the diet), and in the year following the hurricane, they were a major
food item (26 per cent). The principal habitat of the wood rat, clay soil

Otteni, Bolen,
and Cottain

BARN OWL PREY AND REPRODUCTION

439

communities, was not flooded by Hurricane Beulah. Rice rats were partic-
ularly evident only in 1969.

Least shrews [Cryptotis parva) were a relatively stable food throughout
the study. Overall, the pellets contained 1,861 individuals (16 per cent) and
varied from 9 to 34 per cent in annual occurrence. Pocket gophers {Geomys
bursarius) comprised 4 per cent (458 individuals) of the total diet. Cotton-
tail rabbits {Sylvilagus jloridanus) made up 318 separate items or 3 per cent
of the diet. Adult rabbits are likely less vulnerable as Barn Owl prey because
of their comparatively large size ; all of the rabbit skulls taken from the pellets
between 1969 and 1971 were from sub-adults, and it is probable that Barn
Owls select only the smaller, and thus younger rabbits as food.

Birds roosting in association with aquatic communities at the Welder
Refuge occurred 1,066 times (9 per cent) in the owl pellets. These were
primarily members of the Icteridae: 182 grackles, 390 Brown-headed Cow-
birds, and 435 Red-winged Blackbirds. The Barn Owls apparently used the
abundant icterid populations as a buffer group when the availability of rodents
was low (Table 3). With the decline of mice in 1967, icterids in pellets
increased from less than 1 per cent in 1966 to 14 per cent in 1967. Further
declines in the rodent population in 1970 and 1971, indicated in both the
live trapping census and in the pellet analysis, were again compensated by
increased use of blackbirds as food.

Other birds contributed 403 individuals (3 per cent) to the owl diet. Non-
passerine species included Sparrow Hawks {Falco sparverius) , Mourning
Doves (Zenaidura macroura) , Inca Doves [Scardafella inca) , Yellow-billed
Cuckoos [Coccyzus americanus) , and 81 Bobwhite {Colinus virginianus) .
An additional 308 individual passerine birds were identified; these were
primarily 111 Dickcissels {Spiza americana) and lesser numbers of 28 other
species. The occurrence of Bobwhite and other landbirds in the Barn Owl
diet was prominent only in 1968.

Grasshoppers of the family Acrididae were infrequently found in the pellets
although, in 1971, 10 per cent of the pellets contained grasshopper remains.
Other invertebrates were of even rarer occurrence.

Seasonal variation. — The seasonal food-habits picture is least representative
in late summer and early fall, when few pellets were collected. At this time,
young Barn Owls were awing and expanding their range, and the adult birds
used established roosts less than before.

There were pronounced seasonal changes in the percentage of prey species.
Predation on birds, predominantly those that roost over water, was charac-
terized by a seasonal variation. In the winter, j)redation on birds was directed
toward adult migratory blackbirds, whereas in late spring and early summer
predation on nestlings increased. Likewise, there was an inverse relationshij)

440

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 4

Seasonal Variation in Barn Owl Foods, Welder Wildlife Refuge, 1969-1971
Data are percentage frequency.

1969 1970 1971

Species

Summer

Fall

Winter

Spring Summer

Fall

Winter

Spring

Mammals

Mice

42.2

62.3

47.8

5.9

2.7

16.6

24.7

27.9

Rats

7.2

2.2

10.6

22.5

30.5

13.7

7.1

8.6

Shrews

28.3

33.3

27.0

16.8

42.0

34.3

34.6

32.5

Birds Roosting Over

Water

0.4

2.2

6.0

41.7

17.0

6.0

12.8

27.4

Land

0.8

—

—

1.5

3.0

9.8

3.8

2.0

Insects

Grasshopper

21.1

—

1.9

0.8

—

14.7

15.7

—

in the proportion of rats versus mice. The greatest number of rats in the diet
(summer, 1970) corresponded to the lowest number of mice. Conversely,
the period when mice were consumed in great numbers (fall, 1969) coincided
with a small amount of rat foods. These relationships, shown in Table 4,
reflect opportunistic hunting by Barn Owls in various habitats as seasonally
characterized by prey availability.

Biomass. — Pellet analysis alone provides only an index to the numbers of
food items taken, but if the average weight of individual prey species can
also be determined, an index of biomass can be developed. Biomass is ecolog-
ically significant because small species (pigmy mouse, etc.), while numerically
abundant in the pellets, may provide relatively little bulk to the Barn Owl diet.
Hence, using the weights of specimens collected in live traps, the mouse
population which numerically contributed 41 per cent of the owl foods actually
comprised only 11 per cent of the biomass (Table 5). In contrast, the rat
population contributed 50 per cent of the biomass and, numerically, only 21
per cent of the diet.

Using the biomass estimates shown in Table 5, we found that a strong
relationship exists between the percentage frequency of each class of food and
the percentage biomass in the Barn Owl diet. Mammals comprised 85 per
cent of the individual prey and 87 per cent of the biomass and birds, 13 per
cent of the individuals and 13 per cent of the biomass.

Barn Owl breeding biology: nest sites. — Tbe Barn Owl primarily nests in
tree cavities, holes in river banks, and in crevices in cliffs although nests in
towers, barns, and other buildings are common. At the Welder Refuge, Barn

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

441

Table 5

Numerical and Biomass Composition of Barn Owl Foods as Determined by Pellet
Analysis, Welder Wildlife Refuge, 1965-1971

Species

Number

individuals

Percentage

of

individuals

Estimated
weight
( grams )

Estimated

biomass

Percentage

of

estimated

weight

Mammals

Pigmy mouse

2,252

19.7

9.5

21,394

2.9

White-footed mouse

208

1.8

20.5

4,264

0.6

Fulvous harvest mouse

1,161

10.2

10.5

12,190

1.6

Hispid pocket mouse

1,094

9.6

42.0

45,948

6.1

Cotton rat

1,232

10.8

170.0

209,440

28.0

Rice rat

660

5.8

56.0

36,960

5.0

Wood rat

538

4.7

236.0

126,968

17.0

Least shrew

1,861

16.3

4.5

8,374

1.1

Cottontail

318

2.7

250.0

79,500

10.6

Pocket gopher

458

4.0

229.0

106,256

14.2

Unknown mammals

166

1.4

Sub-total

9,740

85.4

651,294

87.1

Birds

Boat-tailed Crackle

182

1.6

120.0

21,840

3.0

Brown-headed Cowbird

390

3.4

40.0

15,600

2.1

Red-winged Blackbird

435

3.8

65.0

28,275

3.8

Dickcissel

111

1.0

150.0

16,650

2.2

Miscellaneous birds“

291

2.5

50.0

14,000

1.9

Unknown birds

69

0.6

Sub-total

1,478

12.9

96,365

12.9

Insects

Grasshoppers

190

1.7

2.0

380

0.1

All species

11,408

100.0

748,039

100.0

® Birds each providing less than 1.0 per cent total biomass include a wide range of passerines and
81 individual Bobwhite (Colinus virginianus) and 38 Virginia Rails (Rallus lirnicola), among other
non-passerine species.

Ov/ls made extensive use of nesting boxes described elsewhere (Bolen, 1967).
Of the 112 Barn Owl nests found in this study, 109 were located in 36 nesting
boxes situated on the Welder Refuge; the additional three nests were located
in a small shed also on the Refuge grounds.

Nest materials. — Pellets regurgitated in the confines of the nest boxes are
subsequently trampled underfoot and in time become a thick, coarse mat of
organic debris underlying the eggs. Wallace ( 19481 also rejjorted that Barn

442

THE WILSON BULLETIN

December 1972
Vol. 84. No. 4

Months

OF Nest Initiation

Table 6

for Barn Owls, Welder Wildlife

Refuge, 1965-1971

Date

Number of nests

All years

1965

1966

1967

1968

1969

1970

1971=»

Number Mean Per cent

Januan-

3

7

_

_

5

_

_

15

2.1

13.4

Februar>-

2

2

10

4

2

4

-

24

3.4

21.4

March

3

3

~

7

7

7

4

38

5.4

33.9

April

1

1

2

-

-

2

1

7

1.0

6.2

May

1

-

-

1

-

1

-

3

0.4

2.7

June

5

7

-

-

2

-

-

14

2.0

12.5

July

5

2

-

-

-

-

7

1.2

6.2

August

1

1

-

-

-

-

2

0.3

1.8

September

1

-

-

-

-

-

1

0.2

0.9

October

-

1

-

-

-

-

1

0.2

0.9

Total

22

24

19

12

16

14

5

112

—

100.0

“ Field study ended in June, 1971.

Owls crushed many of their pellets when nesting; no other materials are
involved in nest construction.

Nesting chronology. — Nests were initiated four times in January, twice in
February, and once in March (Table 6 ). These differences suggest that the
onset of nesting may be regulated by the availability of food more so than
by such environmental features as photoperiod or temperature.

The length of the Barn Owl nesting season in south Texas was determined
from the beginning dates of each year’s first and last nests. The last nests,
respectively, were started in September of 1965, October of 1966, April of
1967, ^lay of 1968, June of 1969, May of 1970, and April of 1971. The
average nesting season lasted 5.3 months during the period 1965-1971. Nest-
ing attempts increased rapidly as each season began and reached their peak
in March (Table 6) .

Number of broods per season. — At the elder Refuge female Barn Owls
usually produce only one brood per year. However, there was one instance
(1965 ) of a banded Barn Owl raising two broods in the same calendar year.
Male Barn Owls feed their mates while the latter incubates, whereas after
hatching both parents tend the flightless young and remain with the brood
for some time even after flight is attained. This pattern of events does not
usually permit time for a second clutch during the nesting season unless tlie
male were to divide his efforts between the re-nesting female and the owlets
of the first nest.

Clutch size. — Of 112 separate clutches under study, 91 were considered as

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

443

Table 7

Mean Clutch Size for 91 Barn Owl Nests, Welder Wildlife Refuge, 1965-1971

Clutch size

No. clutches

Total eggs

3

19

57

4

12

48

5

29

145

6

24

144

7

4

28

8

3

24

Totals

91

446

Mean clutch size

4.9

Standard deviation

1.3

completed sets. The size of these varied from 3 to 8 eggs per nest with a
mean clutch size of 4.9 eggs (Table 7). The additional 21 nests, 11 with
1 egg and 10 with 2 eggs, were excluded from the analysis as incomplete
clutches.

Lack (1947) found a tendency for the mean clutch size of owls to increase
with latitude and with an increased abundance of rodents. Henny (1969)
reported a mean clutch size of 5.3 eggs for Barn Owls nesting in Switzerland
(Lat. 46-47 N) and 4.9 eggs for those in Maryland (Lat. 38-43 N). Clutch
sizes for the 68 Maryland nests and the 91 nests in this study (Lat. 28 N)
thus yielded identical results. It thus appears that clutch sizes in Barn Owls
are more closely associated with factors other than with latitude. Lack (1954:
22) also suggested that the number of eggs laid by each species (i.e. average

Table 8

Nest and Egg Success for the Barn Owl, Welder Wildlife Refuge, 1965-1971

Nests

Eggs

Year

Attempts

No.

Hatched

No.

Percentage

successful

Layed

No.

Hatched

No.

Percentage

successful

Clutch

mean

1965

19

10

52.6

95

45

47.3

5.0

1966

21

12

57.1

106

57

54.2

5.0

1967

16

13

81.2

86

60

69.7

5.4

1968

12

11

91.6

62

38

61.2

5.2

1969

14

11

78.6

63

35

55.5

4.5

1970

6

2

16.6

23

8

34.7

3.8

1971

3

1

33.3

11

2

18.1

3.7

Totals

91

60

65.9

446

245

54.9

4.9

444

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 9

Influence of Prey Availability on Barn Owl Breeding Success, Welder Wildlife

Refuge, 1965-1971

Abundance of prey
(scale 1-14 )“

Reproductive effort

Abundant
( 3 years )
14-7

Scarce
(4 years)
6-1

Number of pairs breeding

14.0

11.5 N.S.

Mean clutch size

5.0

4.4 N.S.

Young fledged/pair

2.5

1.0*

® Abundance scale defined as

biomass per year divided by total biomass for all

years, rounded to

nearest whole number.
* P < 0.05.

clutch size ) has been established by natural selection to correspond with the
largest number of young that can be successfully raised. Successful rearing, in
turn, is based on the amount of food that is available and provided to the
young by the adults. This hypothesis as it relates to the clutch size of the
Barn Owls nesting in southern Texas, is discussed in a following section.

Nesting success. — Nesting success of the Barn Owls was 66 per cent for the
seven year period of our study. Losses occurred because of abandonment ( 10
per cent ) , swarming bees ( 1 per cent I , and disturbances associated with our
periodic inspection of the nests during incubation (23 per cent). Of 446 eggs
laid in these nests, 245 (55 per cent ) later hatched. Year-by-year details are
shown in Table 8.

Evaluation of prey biomass and Barn Owl reproduction. — Juvenile Barn
Owls remain in the care of their parents for more than two months after
fledging. Prey populations during this time must, therefore, be sufficient
to provide food for the adults and the young. Food supplies are thus critical
to Barn Owl reproductive success for about 18 weeks.

The ultimate measure of breeding success is the average number of young
raised per pair (Lack 1966:142). Accordingly, we found that Barn Owls
raised 1.5 times as many young per pair in years when prey was abundant
than in years when prey populations were more limited (Table 9).

A statistical comparison between the biomass of mammals in the Barn Owl
diet and the number of young owls raised per pair indicated that mammals
were a dietary requirement for successful reproduction. Declines in the
biomass of mammals were significantly correlated ( r = 0.913) with a cor-
responding decline in the number of owlets fledged (Fig. 1). The other-
wise abundant bird population alone did not sustain successful Barn Owl
reproduction.

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

445

Fig. 1. Reproductive success of the Barn Owl relative to the percentage of mammalian
biomass in the owl diet. Statistical correlation of these data was highly significant ir —
0.91, P < 0.01).

The Welder Refuge supported 12 to 17 breeding pairs of Barn Owls from
1965 through 1970. During this time, the pellet analysis indicated that the
mammalian biomass was abundant through the breeding season of 1969.
Thereafter, however, rodent numbers and their biomass rapidly declined in
the winter of 1969-70. The 12 pairs of Barn Owls attempting to breed at
this time experienced a marked reduction in the number of young fledged;
fully 92 per cent more young were successfully raised in 1969 than in 1970
I Table 10 1 .

The three owlets actually fledged in 1970 were indeed nourished by a diet
of 91 per cent blackbirds. Two owlets of another nest — abandoned at 5 weeks
of age — were fed a diet of 72 per cent blackbirds prior to the time of parental
abandonment. The significant amount of birds in the diet of these owlets
was further evidence that rodents were not available in the spring and summer

446

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 10

Breeding History of

Barn

Owls, Welder Wildlife

Refuge, 1965-

-1971

Year

Breeding

pairs

Mean

clutch

Young

fledged

Young
fledged
per pair

Abundance
index of
prey based
on pellet
analysis®

Biomass
ratio of
mammals
to birds

1965

12

5.0

38

3.2

8

99- 1

1966

17

5.0

35

2.0

6

98- 2

1967

16

5.4

32

2.1

14

92- 8

1968

12

5.2

25

2.4

6

93- 7

1969

14

4.5

34

2.4

7

83-17

1970

12

3.8

3

0.2

4

67-32

1971

5

3.7

0

0.0

1

55-45

® Abundance index defined as biomass per year divided by total biomass for all years, rounded to
nearest whole number. The index reads from 14 (abundant) to 1 (scarce).

months of 1970. The amount of rodent biomass available to the Barn Owl
population continued to decline after 1970 (Table 11).

In 1971, 58 per cent fewer pairs nested than in 1970 (five vs. 12 pair).
This again indicated that the Barn Owl population had adjusted their re-
productive efforts to the lower population level of rodents. The mean clutch
size was slightly reduced whereas the number of completed clutches was 50
per cent lower than in 1970. The information from both the trapping and

Table 11

Seasonal Variation in Biomass and Numbers of Live-Trapped Mammals, Welder
Wildlife Refuge, 1969-1971.

1969

1970

1971

Total

Species

Summer

Winter

Spring Summer

Fall

Winter

Spring

Pigmy Mouse

2,004

1,007

988

2,118

1,254

3,059

703

11,133

Harvest Mouse

126

115

63

105

21

1,302

199

1,931

Deer Mouse

61

—

164

184

—

246

61

716

Hispid Pocket Mouse

—

—

—

84

—

—

—

84

House Mouse

—

—

10

—

—

10

10

30

Wood Rat

6,608

—

236

236

—

—

—

7,080

Rice Rat

1,344

—

112

56

112

—

—

1,624

Cotton Rat

—

170

510

1,190

—

170

170

2,210

Least Shrew

54

—

5

40

13

22

9

143

Total Biomass

10,197

1,292

2,088

4,013

1,400

4,809

1,152

24,951

Number Individuals

290

118

126

262

139

822

299

2,056

Biomass/No. Individuals

35.2

10.9

16.6

15.3

10.1

5.8

3.8

12.1

Otteni, Bolen,
and Cottam

BARN OWL PREY AND REPRODUCTION

447

from the pellet analysis showed the lowest biomass of rodents during the
winter and spring of 1971 (Tables 10 and 11).

Predator— prey relationships. — The Barn Owl population on the Welder
Refuge seemed well adjusted to the carrying capacity of the area, and did
not change greatly until the crash of all small mammal populations in 1970.
Prior to 1970, some individual prey species occurred at high population levels
while others were low. However, the overall prey population of mammals
during the Barn Owl breeding seasons appeared sufficient to meet the require-
ments of the owls. The total owl population maintained a constant rate of
food consumption during years preceeding the 1970 rodent crash. A year-
to-year increase in Barn Owls was not apparent because of the balance between
the predator and prey populations. Thereafter, however, a decline in the total
owl population was proceeded by a decline in the populations of rodents.

Thus the increase or decrease in any one small mammal population appeared
to have had no immediate effect on Barn Owl nesting density or success, but
the productivity of the Barn Owl population was greatly reduced when the
overall small mammal population decreased in availability to a point where
the Barn Owls depended on birds for 32 per cent or more of their food.

SUMMARY

A study of Barn Owl ecology was begun in 1965 at the Welder Wildlife Refuge, Sinton,
Texas, and continued to the summer of 1971. Additional study of the small mammal prey
populations took place between 1969 and 1971.

The seasonal fluctuations of the rodent populations were severe, and trap success ranged
from 43.3 to 1.9. Blackbird populations varied between an estimated 50,000 birds during
the winter to 15,000 in the spring and summer. The availability of blackbirds as owl
food was not limited.

Food habits of the Barn Owl were determined from pellet analysis. This material
contained 11,408 food items of which mammals comprised 85 per cent, birds 13 per cent,
and insects 2 per cent. A strong correlation existed between the percentage frequency
and the percentage biomass of these foods.

Barn Owls initiated their nests in the first three months of the year with a peak of
activity in March. The nesting season was irregular, lasting from two to ten months.
Clutch size was calculated as 4.9 eggs per nest. Nesting success over a 7-year period was
65.9 per cent.

There were 1.5 times as many young raised per pair in years when rodent prey popula-
tions were abundant than in years when prey was less available.

Both the quantitative and qualitative nature of Barn Owl foods are important as the
otherwise abundant blackbird population did not sustain successful Barn Owl breeding
as measured by fledged owlets per pair. The changes occurring in a single small mammal
population had no immediate effect on Barn Owl nesting density or success. However,
when the overall small mammal population decreased in their availability as prey, the
productivity of the Barn Owl population was greatly reduced. This point was reached when
birds made up at least 32 per cent of the Barn Owl diet. Mammals, rather than birds,
were the key staple on which Barn Owl reproduction depended.

448

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

ACKNOWLEDGMENTS

We express our gratitude to Marshall White and C. Robert Watts for use of their
unpublished data on the food habits of owls from 1965 to 1968. Steven Labuda assisted
with inspections of the nest boxes and Ronald Cherry helped with the rodent census. An
early draft of the manuscript benefited from the reviews of Robert Packard, Donald
Klebenow, and Billie E. Dahl; the final revision was reviewed by M. Kent Rylander.

LITERATURE CITED

Bolen, E. G. 1967. Nesting boxes for Black-bellied Tree Ducks. J. Wildl. Mgmt., 31:
794-797.

Box, T. W., AND A. D. Chamrad. 1966. Plant communities of the Welder Wildlife
Refuge. \^'elder ildl. Foundation. Contrib. 5, Series B.

Craighead, J. J., and F. C. Craighead. 1956. Hawks, owls and wildlife. ildlife
Management Institute, Washington, D.C.

Davis, D. E. 1959. Manual for analysis of rodent populations. School of Hygiene and
Public Health. The John Hopkins Univ., Baltimore, Mar>Jand.

Errington, P. L. 1932. Technique of raptor food habits study. Condor, 34:75-86.
Glading, B., B. F. Tillotson, and D. M. Selleck. 1943. Raptor pellets as indicators
of food habits. California Fish and Game, 29:92-121.

Glass, B. P. 1951. A key to the skulls of North American mammals. Oklahoma State
Univ., Stillwater.

Henny, C. j. 1969. Geographical variation in mortality rates and production require-
ments of the Barn Owl iTyto alba). Bird-Banding, 40:277-290.

Krebs, C. J. 1966. Demographic changes in fluctuating populations of Microtus cali-
fornicus. Ecol. Monogr., 36:239-273.

Lack, D. 1947. Significance of clutch size. Ibis, 89:302-350.

Lack, D. 1954. The natural regulation of animal numbers. Clarendon Press, Oxford.
Lack, D. 1966. Population studies of birds. Clarendon Press, Oxford.

Reed, C. L, and B. P. Reed. 1928. The mechanism of pellet formation in the Great
Horned Owl. Science, 68:259-260.

Southern, H. H. 1955. Nocturnal animals. Sci. Amer., 193:88-98.

Wallace, G. J. 1948. The Barn Owl in Michigan; its distribution, natural history and
food habits. Michigan Agr. Exp. Sta., Tech. Bull. No. 208.

DEPARTMENT OF RANGE AND WILDLIFE MANAGEMENT, TEXAS TECH UNIVERSITY,
LUBBOCK, TEXAS 79409 ( OTTENI AND BOLEN ) AND WELDER WILDLIFE FOUN-
DATION, SINTON, TEXAS 78387 (COTTAMj. 10 DECEMBER 1971.

SEED SIZE PREFERENCE IN FINCHES

Mary F. Willson

SEED preferences of several finch species have been explored in the labora-
tory ( Willson, 1971; Willson and Harmeson, in press) using both wild
and commercial seeds. Choice among a variety of seed types necessarily
involves many variables such as color, flavor, size, nutritional value and so
forth. In an effort to eliminate some of these variables, I conducted series of
choice experiments using different sizes of the same species of seed (from the
same commercial shipment or gathered from the same areas locally). Most
of these trials used Cardinals (Richmondena cardinalis) but a few observa-
tions are available for other species. Hespenheide (1966) earlier made similar
observations on a few individuals of two species.

METHODS

Birds were captured locally, kept in fairly large, individual cages in the laboratory
(see Willson, 1971), and fed on a diet of mixed seed plus supplements. Equal numbers
of different size classes of seed, placed in small dishes, were presented to the birds. Since
the position of the dishes relative to the perches in the cage influenced choices, the relative
position of each seed size was changed between trials. Four sizes of sunflower seed
{Helianthus annuus) were tested: long and fat (LF), long and thin (FT), short and fat
(SF), and short and thin (ST). Seeds were divided into length categories of 12 mm or
less and 13 mm or more, and thickness categories of 4.7 mm or less and 5.2 mm or more;
width in all categories was similar. Wild hemp {Cannabis saliva), sorted into the two
size classes by sieving, was also used. Seed dishes were placed in the cages and left for
a short period, depending on how fast the seeds were eaten: the dishes were removed
before any one of them was completely empty. Ten trials for each bird were run on both
sunflower and hemp.

The significance of differences in seed choice were tested by chi square, P ^ 0.05.

RESULTS

Five male and five female Cardinals were tested; there was no significant
difference between male and female choices. Nine birds showed no preference,
individually, and one avoided class LT. Taken as a group, however, the ten
manifested a significant preference for class ST and against class LT (Table
lA). Cardinal preferences for certain sizes of sunflower, when shown, were
not based solely on thickness or length for either males or females: when all
seeds of the same thickness or length classes were pooled, no difference between
classes were evident.

In a set of earlier tests, four Cardinal females and two males were given
ten trials each. This group preferred thin seeds to fat, regardless of length.
Nine birds were tested on hemp. Two males and the four females had no

419

450

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 1

A. Sunflower Seed Size Preferences

ST

SF

LT

LF

n

Cardinal*

1. 5 ^ 5 $ $

29

25

20

26

1,391

2. 4 $ 2 ^ ^

30

18

29

22

1,568

Tree Sparrow* (4)

55

9

4

32

22

Song Sparrow* (4)

57

28

11

4

54

Slate-colored Junco* (4)

71

21

4

4

24

Purple Finch* (3)

39

7

39

14

635

Rose-breasted Grosbeak* (2)

57

43

212

B.

Hemp Seed Size Preferences

Large

Small

n

Cardinal (5 4 $ $ )

52

48

2,675

* Indicates significant differences among the choices by

X^ P ^ 0.05.

The percentage of

all seeds eaten that were of each size class is given, with the total number of seeds eaten

in all trials.

preference for either large or small hemp seeds, two other males preferred
small and one preferred large seeds. Males as a group, however, showed no
significant preferences (Table IB).

Both male and female Cardinals husked and ate large and small hemp at
the same rate, but females husked large hemp faster than males (Table 2).
Males husked all sizes of sunflower at the same rate; for females, husking
rates were also similar except that seeds of class ST were husked significantly
faster than those of LT (i-test, df = 50). Males husked large sunflower seeds,
both LF and LT, somewhat faster than did females.

Several other finch species were tested in fewer numbers and with fewer
trials (summarized in Table 1). Tree Sparrows {Spizella arborea), four birds
in four trials each, ate mostly class ST, but class LF was second choice, which
seems peculiar, and is probably a result of the small sample size. Song Spar-
rows {Melospiza melodia) and Slate-colored Juncos {Junco hyemalis) (four
birds of each species, eight trials per bird) preferred class ST, with class SF
in second place, so that in general both species preferred short to long seeds.
The small number of seeds eaten by all the small birds reflects the difficulty
with which they handled even the smallest sunflower seeds. Of two Rose-
breasted Grosbeak [Pheucticus ludovicianus) males in ten trials between long
and short sunflower seeds, one bird preferred long, the other short ones.

Mary F.
Willson

FINCH SEED SIZE PREFERENCE

451

Table 2

Cardinal: Seed Husking-and-Eating Times, in Seconds

(i'cT $ ?

i SE N X SE N

ST

LF

SF

LT

Large

Small

Sunflower

28.8

2.3

25

32.2

3.1

24

29.1

2.8

25

** 39.2

5.0

26

35.0

3.1

25

43.3

4.9

25

33.9

2.4

26

** 39.0

2.3

28

Hemp

6.9

0.87

15

4.1* *

0.32

15

6.2

0.60

15

6.0*

0.98

15

** Indicates a significant difference between males and females.

* Indicates a significant difference between seed sizes.

Three Purple Finches {Carpodacus purpureus) , probably females, 10 trials,
preferred thin seeds to fat ones; length preferences varied among the individ-
uals. Husking times for Purple Finches were similar for all sizes of seeds
(Mann-Whitney U, P = 0.05; x = 83.1 sec., n = 10 seeds of each size category),
but fat seeds were obviously more difficult to handle since over 50 per cent
of those picked up slipped out of the bill before cracking.

DISCUSSION

In the main, the results for Cardinals indicate a highly variable choice of
sunflower seed sizes. Many individuals showed no particular preference, but
the collection as a whole was inclined to favor short-thin seeds, and sometimes
long-thin. Correspondingly few differences were found in husking times,
except that females could handle class ST more quickly than class LT. Also,
no strong preference was seen for size of hemp seed, and there was no differ-
ence in husking time of different sizes. This suggests that all the sizes used
may have been well within the average capacities of the Cardinals to handle.
Any individual preferences could be the result of individual differences in
morphology, learning, physiology, etc. J. R. Jehl (pers. comm.) has recently
emphasized the importance of such individual variability among the experi-
mental birds.

Song and Tree Sparrows and j uncos chose class ST especially, in keeping
with their smaller bills (see Willson, 1971 for average dimensions). Purple
Finches are intermediate between Cardinals and the smaller birds in bill size
(length 10.0 mm, depth 8.3 mm, width 6.9 mm, n = 12). They selected seed
primarily on the basis of thickness rather than length. Purple Finches have

452

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

SONG SR

PURPLE

FINCH

Fic, 1. Top and side views of the bills of the primary experimental species, to scale.

Mary F.
Willson

FINCH SEED SIZE PREFERENCE

453

an average bill length equal to that of j uncos, intermediate between Tree
and Song Sparrows, but much shorter than Cardinals (see Fig. 1) . The ability
of Cardinals to handle experimental seeds of all sizes with almost equivalent
facility is probably a function of their larger bill size. The shorter bills of
Purple Finches and the small-billed species may make difficult the handling
of thicker seeds by providing a smaller “pocket” for the holding of thick
seeds, so that they slip out more readily. The greater bill depth and width
of Purple Finches (and Cardinals) may facilitate handling of long seeds by
providing a broader base for holding the seeds while they are rotated during
cracking and by permitting greater forces to be applied to the seed so that
even if long seeds can’t be balanced as well as short ones, the greater forces
permits them to be cracked before they slip away. Bill characteristics and
related morphological characteristics concerned with food handling are dis-
cussed in some detail by Bowman (1961, 1963) and Ziswiler (1965).

Measurements of the force delivered by the bill in cracking seeds would be
most useful. At present, the only information available came from a Gilson
polygraph “physiograph,” which transforms physical pressure into electrical
impulses to be recorded on a moving graph. The birds were held in such a
manner that either the upper or the lower beak pressed against the transducer
as the bird “bit.” The largest response so generated was used as an index
of maximum pressure generated, and converted to force/unit area. These
estimates of force refer to the middle of the bill, not the tip where the pressure
would be greater. Although in absolute terms the estimates of force applied
may not be accurate, they are probably adequate relative indices.

Six species were so measured: Cardinal, Purple Finch, Song Sparrow,
White-throated Sparrow {Zontrichia albicollis) , Fox Sparrow [Passerella
iliaca) , and junco. At least two individuals of each, sometimes four, were
measured. Invariably the lower jaws exerted a somewhat greater pressure
than the upper, but for purposes of Figure 2, all measurements were averaged.
All bill dimensions are significantly correlated with the average force applied
(Spearman rank correlation, p ^ 0.05), but Figure 2 suggests that force
exerted by the bill is more closely associated with depth or width than with
length. Width and depth are more closely correlated with each other than
with bill length and it seems reasonable to suppose that depth is more im-
portant in determining the force applied than is width (Bowman, 1961).
Obviously the presence of palatal bosses or keels or other special structures
could confound this tendency.

Average kernel weights of the different sunflower seed sizes varied sig-
nificantly (Mann-Whitney U, p ^ 0.05 ) : LF > I/F = SF > S F. 3'he mean
weights of 10 kernels of each size class were as follows: LF. O.Ool g: I/l.
0.065 g; SF, 0.063 g; ST, 0.053 g. Making the reasonable assumption that

454

THE WILSON BULLETIN

December 1972
Vol. 84. No. 4

1000-

A

800 •

600

A

"to n 12 1*3 1*4

Bill length (mm)

Fig. 2. Association of each bill dimension with the average force exerted by the bill:
all correlations are significant, but there is less scatter for width and depth, which are
themselves closely correlated. Cardinal, # ; Purple Finch, Fox Sparrow, (2); Song
Sparrow, (§) ; White-throated Sparrow, A; Slate-colored Junco, ®.

Mary F.
Willson

FINCH SEED SIZE PREFERENCE

455

the per-gram caloric content of different-sized kernels is similar, the small-
billed species were limited in their food intake by their apparent inability to
handle large seeds. In the wild they seldom tackle such large seeds. However,
Cardinals, which could handle all sizes offered, certainly did not exercise their
ability to maximize caloric intake.

SUMMARY

Cardinals showed few preferences for seed (sunflower or hemp) size and little difference
in ability to handle different seed sizes. A slight tendency to prefer short and thin
sunflower seeds may be associated with the ability of females to husk this size more
rapidly.

Other species tested usually preferred small (short and thin) sunflower seeds cor-
responding to their small bills and general inability to handle larger seeds. Purple
Finches preferred thin sunflower seeds to thick ones, regardless of length. Thick seeds
were apparently difficult to hold in relatively short bills, long ones difficult for more
slender bills.

Relative forces applied by the main portion of the bill may be correlated more closely
with bill depth, and perhaps width, than with length.

ACKNOWLEDGMENTS

R. J. Lederer made the physiograph measurements; the Department of Zoology fur-
nished partial financial support.

LITERATURE CITED

Bowman, R. I. 1961. Morphological differentiation and adaptation in the Galapagos
finches. Univ. California Publ. Zool., 58:1-302.

Bowman, R. I. 1963. Evolutionary patterns in Darwin’s Finches. Occas. Papers Cali-
fornia Acad. Sci., 44:107-140.

HESPENHEroE, H. A. 1966. The selection of seed size by finches. Wilson Bull., 78:191-
197.

Willson, M. F. 1971. Seed selection in some North American finches. Condor, 73:
415-429.

Willson, M. F., and J. C. Harmeson. Seed preferences and digestive efficiency of
Cardinals and Song Sparrows. Condor, in press.

ZiswiLER, V. 1965. (Toward an understanding of seed-opening and the structure of the
horny palate in grain-eating oscines) (in German). J. Ornithol., 106:1-48.

DEPARTMENT OF ZOOLOGY, VIVARIUM BUILDING, UNIVERSITY OF ILLINOIS, CHAM-
PAIGN, ILLINOIS 61820. 22 FEBRUARY 1972.

NESTLING DEVELOPMENT OE BOAT-BILLED
HERONS iCOCHLEARILS COCHLEARIUS)

AT SAN BLAS, NAYARIT, MEXICO

Carlos Juarez L. and Robert W. Dickerman

\lthough the Boat-billed Heron iCochlearius cochlearius) is a wide-
spread species in the New V orld tropics from Mexico south to Peru
and southern Brazil, and is widely maintained and recently bred as a zoo
bird (Bell, 19661, little has been written on its sub-definitive plumages and
to date few data are available on its nestling development. A study of the
nesting biology of the Boat-billed Heron has recently been published (Dicker-
man and Juarez, 1971). This report on the gro^sth of the nestlings is the
second part of that study.

METHODS

The field ^vork ^vas carried out from August to October 1964, the period of nesting
activity in the large colony of mixed heron species, 3 kilometers ANE of San Bias, Aayarit
( Dickemian and Gavino, 1969; Dickerman and Juarez, 1971). The field work was largely
carried out by Juarez, and provided in part the basis of his professional thesis submitted
to the Facultad de Ciencias of the Universidad Aacional Autonoma de Mexico (Juarez,
1967). The junior author provided the outline for the project and translated and amplified
the manuscript.

Nesting was well underway when the study was initiated on 19 August. At that time
31 nests contained 65 eggs and one newly-hatched chick (Dickerman and Juarez, 1971).
AU nests and eggs then present were marked. On subsequent daily visits to the colony
new nests and eggs were labeled and as chicks hatched they were color coded with a dab
of paint. When the young were large enough (usually about 15 to 19 days), they were
banded -vGth leg bands provided by the U.S. Fish and \^’ildlife Service. Each day all new
eggs, and as many young as time permitted, were weighed and measured.

Measurements taken were: weight in grams, and the lengths in millimeters of the 3rd
and 8th primaries, the tarsus, the upper mandible from the tear duct and from the anterior
edge of the nostril, and the width of the upper mandible at the base (Fig. 1). Measure-
ments for the upper mandible from the tear duct and of the third primaiv' were modeled
after the study by McClure et al. (1959) . The vane and sheath of the 3rd and 8th primaries
were measured because of the doubt as to which feather McClure et al. referred to as the
3rd primary. Later W. F. Scherer, one of the co-authors, informed us (pers. comm.)
that in the Japanese study they measured the third large primaiv- from the outside (i.e.,
8th primaiy). Measurements were taken with vernier calipers reading to a tenth of a
millimeter. "V^'eights of small young were taken with an Ohaus triple-beam balance. Young
of a few days and older were weighed in a plastic bag on an Ohaus spring scale read to
the nearest gram.

The subspecies of Boat-billed Heron nesting at San Bias, Aayarit, is Cochlearius coch-
learius zeledoni (type locality Mazatlan, Sinaloa). As in other New \^'orld species of the
family Ardeidae, there is only a minor degree of sexual dimorphism in "vCng and tail
measurements (1-3 per cent) within populations of the Boat-billed Heron. However

456

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

457

Fig. 1. Method of measuring nestling Boat-billed Herons. BT = culmen from tear
duct; BN = culmen from anterior edge of nostril; BW = width of bill; T = tarsus;
P r= primary (third and eighth) ; V =: vane and S = sheath.

measurements of the tarsus and the exposed culmen vary about 8 per cent between the
sexes, with males slightly larger (Table 1). Still, sexual dimorphism in size, even of
tarsal and culmen measurements, did not constitute a significant variable in making field
measurements of the young. This is supported further by the nearly parallel growth curves
for male and female nest mates (Fig. 2).

Carpenter (1971) presented measurements of randomly selected nestlings and older
birds raised in the New York Zoological Park and measurements of “mounted specimens”
from the collection of the American Museum of Natural History. Because the zoo colony
included birds from both Central America and South America, and because the sul)species
of the “mounted specimens” measured was not given, comparisons are not made with
that study.

Table 1

Measurements of Adult Boat-billed Herons from the Pacific Coastal Lowlands of
Mexico from Sinaloa South to Oaxaca

Males Females

No.

Range

Mean

so

No.

Range

Mean

SI)

Wing (chord)

16

259-280

269.3

5.4

11

2.58-273

264.5

4.2

Tail

15

102-110

106.5

2.2

11

100-111

104.6

3.8

Tarsus

16

71 83

79.4

3.0

11

7.3-78

75.4

1.8

Exposed culmen

16

78-88

8.3.7

2.8

11

74 82

78.2

2.2

458

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 2. Growth rates of two Boat-billed Heron nest mates at San Bias, Nayarit. August-
September 1964.

NESTLING DEVELOPMENT

Weight. — Gross weights as taken in the field (Fig. 3) were far more variable
than were those for young Green Herons [Butorides virescens) in the same
habitat (Gavino and Dickerman, 1972). Boat-billed young, like those of
Black-crowned Night Herons {Nycticorax nycticorax), were especially prone

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

459

Fig. 3. Daily weights of nestling Boat-billed Herons at San Bias, Nayarit, with range,
mean, and number of young in sample.

to regurgitate their food. However it was not always feasible or possible to
stimulate regurgitation uniformly. Thus weights for an individual bird might
increase (or decrease) by as much as 50 per cent over two consecutive days,
due largely to the volume of food in the bird’s stomach. Nestlings 20 days of
age regurgitated 90-100 g of food, over 30 per cent of the weight of an
average nestling at that age.

Secondly, due to the initiation of incubation with the laying of the second
egg, hatching was similarly spread out over a several-day period ( Dickerman
and Juarez, 1971). Thus, for example, young no. 3 in nest 10, weighing 31.8
when two days old, had to compete on the same date with a sibling 7 days
old that weighed 110.0 grams! In nest 33 one chick was two days younger
than the other. When 10 and 11 days of age resjiectively, tliey weighed 110

460

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig, 4. Daily measurement of length of the tarsus of nestling Boat-billed Herons at
San Bias, Nayarit, with range, mean, one standard deviation (gray bar) on either side
of the mean, and number of young in sample.

grams and 203 grams; yet at age 25 days they weighed 325 and 260 grams,
respectively.

A third cause of low weight gain was poor attendance by the parent bird.
In nest 12, three eggs hatched but two young had disappeared by the time
the last chick to hatch was 4 days old. Even this single young was apparently
poorly fed, for on Figure 3 it represents the minimal weight figure for days
9, 14, 20, and 30! In other nests with two or three young, all developed a
pace with at times exceedingly little variation (see Fig. 2 for development
of two siblings in nest 6) . Because of the great extent of variations in weights,
they are of little value as age criteria. Some young 6 days old equaled or

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

461

Fig. 5. Daily measurement of length of culmen, from the anterior edge of the nostril,
of nestling Boat-billed Herons (key same as Fig. 4).

exceeded in weight other young 19-21 days of age. Conversely, some young
28-30 days of age weighed no more than other young 11 days old.

Gross (1923) in his detailed study of the Black-crowned Night Heron did
not mention great disparity in weights among young of the same age. Un-
fortunately McClure et al. (1959) did not record weights of their large series
of aged young Black-crowned Night Herons; and Wolford and Boag ( 1971 I
only plotted mean values in their growth curve for weight without giving
ranges or sample sizes.

Growth in bony structures. — Growth rates of hony structures that were
measured (length of tarsus, length of bill from anterior edge of nostril and
width at base and from tear duct) for some individual birds were exceedingly
uniform (Fig. 2). However, the measurements of these structures for the
population studied showed a moderate to great amount of variation, in jiarl
because of the variation in nutrition mentioned above I Figs. 1 61. A run-
ning average of the mean values shows that the tarsus grew from 1.0

462 THE WILSON BULLETIN December 1972

Vol. 84, No. 4

Fig. 6. Daily measurement of length of the culmen from the tear duct and the width
of the bill at the base of nestling Boat-billed Herons (key same as Fig. 4).

to 2.9 mm per day to age 18 days. Between day 18 and day 30 the rate
stabilized at about 1 mm per day. In contrast, the bill measurements show
a slightly increased growth rate after day 14-15, averaging less than 1.5 mm
per day before then and over 2.0 per day after that age. The growth rate of
the width of the bill was uniform throughout the time studied. Measurements
for these structures in the oldest young measured fall considerably below the
minimal measurements of comparable measurements for adults (Table 1).
This, in the case of the tarsal measurements, is in contrast to the Green Heron,

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

463

Fig. 7. Daily measurement of length of the eiglith primar>- of nestling Hoat-hilled
Herons (key same as Fig. 4).

464

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

where minimal adult measurements were reached by some individuals by
day 17 I Gavino and Dickerman, 1972).

The mean growth curve for the culmen (method of measuring unstated)
of nestling Black-crowned Night Herons in Alberta is rapid and uniform up
to about day 22, but the extent of individual variation was not plotted ( Wol-
ford and Boag, 1971 ). McClure et al. ( 1959 ), in studying growth in nestling
Black-crowned Night Herons in Japan, also found great variation within an
age class in growth rates of bony structures. In their study some young 21-22
days of age had tarsi and mandible measurements similar to other young only
9-10 days old.

Remiges. — The third and the eighth primaries erupted on days 4-6, rarely
on day 3. Because gro4\th rates were similar, only data on total length ( sheath
plus vane ) of the eighth primary are presented. When the pinfeathers reached
a length of about 20-22 mm on day 13—14, the vane began to emerge. By
day 20-21 the sheath was disintegrating (Fig. 2). Variation in nutrition
apparently influenced the growth rate greatly as shown by the amount of
variation in this measurement exhibited both by the population (Fig. 7) and
to a lesser extent by individual birds (Fig. 9). At the oldest age for which
we have measurements, 28-30 days, the 8th primary had reached barely half
of the adult length (Table 1). Unfortunately, series of fully-grown young in
the first basic plumage are not available for a more meaningful comparison.
Young Black-crowned Night Herons 30 days of age in Alberta had a mean
wing chord of about 250 mm (Wolford and Boag, 1971), nearly within the
range of measurements of the wing chord for adults, 285-315 mm ( Palmer,
1962 ) .

NATAL AND “ JUVENAL PLUMAGE”

The following description of the juvenal plumages is based on a series of
24 young, mostly of known ages, from newly-hatched to 40 days of age, from
San Bias, Nayarit or from near Minatitlan, Veracruz.

The natal plumage has been described by Wetmore ( 1965 ) and Dickerman,
in Dickerman and Juarez (1971). The Boat-billed Heron is unique among
the herons in having a tricolored downy plumage with sharply marked bi-
colored head (Fig. 8). The ventral surface is white, the back (neutral) gray,
and the crown dark sooty gray. The color of the crown and back appear
to fade rapidly even by the 4-6th day post hatching; however, this may be
due to the increase in size of the chick and less dense covering of down. The
mandibles are nearly black with lighter tips and white egg tooth. The latter
is still present in one young 4-6 days old.

By the fourth day rudimentary pinfeathers are visible in most tracts except
in the ventral. The sheaths of the primaries begin to emerge on the 4th day,
and by the 8th day all tracts except the caudal anal and powder-down tracts

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

465

Fig. 8. Early stages of plumage development of Boat-billed Herons (representing ages,
from left to right, newly-hatched, 4 days, 8 days, and 13-14 days).

are clearly demarked by developing pinfeathers. The major abdominal, rump,
and sternal powder-down patches are barely discernible externally in two
young 20-23 days of age, but are well developed in others of the same age.

Feathers of the ventral tracts, the scapular region, primaries and primary
coverts begin to break from their sheaths when the young reach two weeks
of age and by three weeks some young are well feathered ( Fig. 9 ) . As men-
tioned earlier there is great disparity in growth rates between birds of the
same age in different nests. The young on the left in Figure 9 is 23 da\s old.
only 2 days younger than the one next to it. hut is similar in apjiearance to
young about two weeks younger. The two young in Figure 10 are 30 days of
age (larger; oldest young of nest 30) and 32-35 days of age (smaller: fourth
young in nest 12). The tail feathers begin to show color at about 25 da\s.
The pecten of the middle toe nail is visible in one of the young 20 23 da\s
of age and in all young 25 days or older when devel()|)inent was not oh\iousl\
retarded.

The following description of the juvenal jilumage is based on one \oung
52 days of age (right-hand bird. Fig. 9) and two birds 10 days of age. I he

466

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 9. Dorsal and ventral views of plumage development of Boat-billed Herons (rep-
resenting ages from left to right, 23 days, 25 days, 30 days, and 32 days).

Juarez and
Dickerman

BOAT-BILLED HERON NESTLINGS

467

Fig. 10. Young Boat-billed Herons 30 days of age (larger) and 32-35 days of age
(smaller) demonstrating disparity in growth rates occasionally observed among nestlings.

forehead, malar area, auriculars and sides are rich medium brown, darker
in the subloral area. The crown is black, with the feathers of the nape elon-
gated to 45 mm. The interscapular area and the lesser and middle wing coverts
are rich brown, with some individuals showing a vinaceous cast. Remiges,
rectrices, and rump area medium gray. The greater wing coverts are medium
gray, edged with the brown of the interscapular area. The outermost primary
and the feathers of the alula are paler than the other remiges and are tipped
and edged with buff. All remiges and rectrices are still sheathed at 52 days.

Ventrally the overall appearance is pale grayish brown to huffy brown,
paling to whitish on the belly. The breast is nearly uniform but feathers may
j be lightly mottled or, especially medially, tipped with dusky gray. The flank
feathers are weakly streaked. They have a medial white area, varying in width
I between individuals from 1.5 to 3.5 mm, that is bordered by medium gray
. streaks; and the feathers are edged with huffy brown.

I

SUMMARY

Nestling development of the Boat-billed Heron was studied at San Bias, Nayarit, Mexico
August-October 1964. Daily measurements were made on marked young, including weight
and length of culmen from nostril and from the tear duct, width of the bill at base, tarsus
and primaries 3 and 8. Sexual (limori)hism is minimal in all measurements, except length

468

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

of the tarsus and culmen where it is about 8 per cent in adults, but did not constitute a
significant variable in the measurements of nestlings.

Weights of nestlings were exceedingly variable due in part to prolonged hatching period
within clutch and to irregular regurgitation of food. Minimal adult measurements were
not obtained by any structure studied by 28-30 days of age at which time the young could
no longer be caught. Maximal tarsus measurement, for example, was 63 mm compared
to minimal length of 71 for 27 adults from the same region. Variations within an age
group were so great that measurements of even a combination of structure would be of
little use in determining age of nestlings.

The development of the final basic plumage is described.

ACKNOWLEDGMENTS

The project was supported by Research Grant AI-06248 from the U.S. Public Health
Service to the junior author. The senior author wishes to express his gratitude to Dr.
Bernardo Villa R., his advisor of the Universidad Nacional Autonoma de Mexico, and both
authors appreciate his making available to us the facilities of the Institute de Biologia
of that University.

The Direccion General de la Fauna Silvestre, Mexico, D.F., provided the authors with
scientific collecting permits. Gonzalo Gavino T. shared the field work. Dr. Allan R.
Phillips read drafts of the manuscript in Spanish and English and provided critical
suggestions.

LITERATURE CITED

Bell, J. 1966. Boat-bills in our zoo’s “Treetops.” Animal Kingdom, 69:251-252.
Carpenter, J. A. 1971. Notes on the biology and behavior of captive Boat-billed Herons,
Cochlearius cochlearius. Southwestern Naturalist, 16:31-41.

Dickerman, R. W., and G. Gavino T. 1969. Studies of a nesting colony of the Green
Heron [Butorides virescens) at San Bias, Nayarit, Mexico. Living Bird, 8:95-111.
Dickerman, R. W., and C. Juarez L. 1971. Nesting studies of the Boat-billed Heron
(Cochlearius cochlearius) at San Bias, Nayarit, Mexico. Ardea, 59:1-16.

Gavino T., G., and R. W. Dickerman. 1972. Nestling development of Green Herons at
San Bias, Nayarit, Mexico. Condor, 74:72-79.

Gross, A. 0. 1923. The Black-crowned Night Heron {Nycticorax nycticorax naevius)

of Sandy Neck. Auk, 40:191-214.

Juarez L., C. 1967. Observaciones acerca de la biologia, nidificacion y crianzo de la
garza pico de cochuron mexicana, Cochlearius cochlearius, en San Bias Nayarit.
Thesis Professional, Univ. Nacional Autonoma de Mexico.

McClure, H. E., M. Yoshii, Y. Okada, and W. F. Scherer. 1959. A method for deter-
mining age of nestling herons in Japan. Condor, 61:30-37.

Palmer, R. S. 1962. Handbook of North American Birds. Yale Univ. Press, New Haven.
Vol. 1, p. 474.

Wetmore, a. 1965. The birds of the Republic of Panama. I. Tinamidae (Tinamous)
to the Rhynchopidae (Skimmers). Smithsonian Misc. Coll., 150.

W^OLFORD, J. W., AND D. A. BoAG. 1971. Distribution and biology of Black-crowned
Night Herons in Alberta. Canadian Field-Naturalist, 85:13-19.

CALLE TANQUE 11-B, COLONIA BUENAVISTA, CUERNAVACA, MORELOS, MEXICO AND
DEPARTMENT OF MICROBIOLOGY, CORNELL UNIVERSITY MEDICAL COLLEGE,
NEW YORK, NEW YORK 10021 (ADDRESS REPRINT REQUESTS TO JUNIOR
AUTHOR), 4 MAY 1972.

EGGSHELL THICKNESS AND ITS VARIATION
IN THE CEDAR WAXWING

Stephen I. Rothstein

Much recent literature has dealt with the interrelations of certain chlo-
rinated hydrocarbons to reproductive failure and declining populations
in various birds. Ratcliffe (1970 ) has summarized these interrelations which
are mediated largely through changes in eggshell thickness. Despite the
importance of eggshell thickness, general analyses of the factors other than
certain pesticides that might affect it are scarce, save in the chicken {Gallus
gallus) where economic considerations have prompted many studies (see
Romanoff and Romanoff, 1949). Furthermore, data on eggshell thickness in
songbirds are almost totally lacking, even though the latter constitute the
majority of living bird species. This study analyzes the various factors which
might reasonably be thought to be related to the eggshell thickness of a bird
in nature. I have utilized eggs of the Cedar Waxwing ( Bombycilla cedrorum ) ,
an abundant Nearctic passerine.

METHODS

Eggs were collected in 1968 and 1969 in Cheboygan and Emmet Counties, Michigan and
one randomly chosen egg was measured from each nest. Shell thickness, with the mem-
branes, was measured one-third of the way down from the blunt end of each egg, using
a specially adapted Starrett No. 1010 M micrometer. Although this micrometer is grad-
uated in units of 0.01 mm, readings were estimated to 0.001 mm. Blus (1970) and
Kreitzer (1971) apparently also followed this procedure. Accordingly, all statistical tests
were performed with readings in 0.001 mm. However, all of these statistical tests have
also been performed with the data rounded off to 0.01 mm and the results are only slightly
changed from those reported in this paper. (Comparison 2 of Table 1 provides the only
statistical test which is no longer significant when the readings are rounded off to 0.01
mm.)

RESULTS AND DISCUSSION

Natural variation. — The data were divided on the basis of factors which
might relate to shell thickness. Mean eggshell thickness was 4.2 per cent
greater in eggs from three-egg clutches than in eggs from four- and five-egg
clutches, with the difference significant at P < 0.05 (comparison 1, Table 1 ).
A possible inference of this result is that the availability of material for egg-
shell formation may act as a limiting factor for clutch size. Although Lack
(1968) made a comprehensive review of the relations of ecological factors
to egg characteristics, the possible limiting role of material for shell formation
was not considered. Another, although not necessarily mutually exclusive,
explanation of shell thickness dependent on clutch size rests on work with

169

470

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 1

Factors Related to Eggshell Thickness in the Cedar Waxwing

Clutches of less Four and five

than four eggs egg clutches

Entire sample

All eggs
with no
develop-
ment

Eggs with no
develop-
ment

Eggs with
develop-
ment

Eggs with no
develop-
ment

Eggs with
develop-
ment

Recent eggs
(1968-69)
Median (mm)

0.091

0.092**

0.093* *t

0.087t

0.091*?

0.086?

<N)

(68)

(52i

(15»

(2)

( 35)

(14)

Mean (mm)

0.091

0.092

0.095

0.087

0.091

0.087

Old eggs
(1871-1912)

Median (mm) 0.095**

(y) (22)

Mean (mm) 0.095

All the \dtal data could not be acquired for a few eggs. This explains the small changes in certain
sample sizes when tabulated vmder different headings or in Table 1 versus Table 2.

* 1. Probabihtx- for difference between these two samples is <0.05 (two-tailed Mann-WTiitney U
Test; Siegel, 1956).

t 2. P < 0.01 (Randomization test for two independent samples; Siegel, 1956).

±3. P < 0.02 ( Mann-^^'hitney U Test).

** 4. 0.05 < P < 0.06 ( Mann- Whitney U Test).

the chicken. Within a set of eggs, shell thickness generally decreases with
each successive egg, except for the last one (and the penultimate one as well
in sets of six or more) ( Romanoff and Romanoff, 1949; ilhelm, 1940;
Berg, 1945). The first and last eggs usually have similar shell thicknesses.
A similar trend has been found in the Japanese Quail [Coturnix coturnix)
(Bitman et ah, 1969). If this type of trend occurs in songbirds, it could
explain the observed relation between clutch size and shell thickness reported
here for the Cedar axwing. Sixty-seven per cent of the eggs in clutches of
three would have thick shells, but the comparable percentages for clutches of
four and five would be only 50 and 40 respectively. The occurrence of this
trend in songbirds would necessitate the use of nonparametric statistics, the
type applied in this paper, because the frequency distributions for shell thick-
nesses of eggs from different-sized clutches would have different shapes.

Eggs with embryos had significantly thinner shells than ones with no
development, as is shown by two independent tests ( comparisons 2 and 3,
Table 1). To determine whether shell thinning occurs throughout much or
all of incubation, the ideal measure of incubation stage would be the number
of days each egg was incubated before it was collected. However, this is
difficult to determine, especially for species like the Cedar Waxwing which

Stephen I.
Rothstein

EGGSHELL THICKNESS IN WAXWINGS

471

Table 2

Eggshell Thickness and Degree of Development of Embryo (as indicated by its Eye
Diameter) in Clutches of Four and Five Eggs

Diameter of embryo’s eye, mm

Eggshell thickness, mm

1.6

0.087

1.9

0.090

2.2

0.089

3.0

0.084

3.0

0.103

3.6

0.091

4.1

0.090

4.2

0.081

4.3

0.095

5.0

0.082

5.1

0.073

5.4

0.080

5.5

0.079

Probability for above association is <0.025 (Kendall rank correlation, t = -0.416; Siegel, 1956).

normally begin incubating before the clutch is completed (Putnam, 1949;
pers. obs.). Thus, it was decided that some easily measured attribute of the
embryo, such as eye diameter, provides the most reliable measure of the
amount of incubation and development. There is a significant association
(P < 0.025) between the degree of embryonic development (as indicated by
eye diameter) and shell thickness (Table 2), suggesting that thinning occurs
throughout much or all of incubation. The thinning was probably due to
withdrawal of calcium from the shell by the embryos. About 80 per cent of
the calcium in the hatching chick of the domestic fowl is derived from the
shell (Simkiss, 1961) and this withdrawn calcium amounts to about 5 per
cent of the total shell calcium (Simkiss, 1967).

Seven eggs from the four- and five-egg clutches with no development (Table
1) had undergone incubation as indicated by their contents which consisted
of slightly to strongly malodorous yolk and albumen. The average shell thick-
ness of these eggs was close to that for the remaining 28 eggs in the suhsample
(0.092 mm and 0.091 mm, respectively), thus substantiating the inteijiretation
that the shell thinning during incubation is due to the metaholism of the
embryo and not to some ageing or deterioration process in the egg. Previous
studies of birds in nature have not shown a definite relationship hetween sht*ll
thickness and embryonic development, although such a relationship is sug-
gested by data for the Brown Pelican iPelecanus occidentalis) (.Anderson
and Hickey, 1970). However, Vanderstoep and Richards ( 19 <01 have shoun

472

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

that shell thickness in the chicken decreases significantly between the tenth
and eighteenth days of incubation.

Additional analyses done on the 1968-69 sample of waxwing eggs failed
to detect correlations between shell thickness and the following: egg length,
width, or volume and date or year of laying. Although longer eggs tended
to have thinner shells, the association was not statistically significant iP >
0.051 with the Kendall rank correlation coefficient; Siegel, 1956).

It is apparent from the above analyses that the determinants of eggshell
thickness in nature may be quite complex, with little studied ecological and
physiological factors playing significant roles. Indeed, under laboratory
conditions many factors have been found to affect shell thickness in the
domestic fowl ( Romanoff and Romanoff, 1949 ) . The possibility exists that
some factors could bias results in studies intended to deal primarily with
the relation of shell thickness to certain pesticides. A problem of this type
occurred in this study. Waxwing eggs from orchards on farms had a sig-
nificantly greater incidence of sterility and or embryonic death than eggs
layed away from farms ( Rothstein, in press ) . Direct proof was lacking, but
the difference seemed to be most likely due to pesticides, and statistical analysis
demonstrated that the farm eggs had significantly thinner shells. Eurther
analysis, however, showed the farm sample to have a disproportionate number
of incubated eggs (because collecting was done later on the farms than in
the other study areas I . Eggs with no development from each habitat type
were then found to have almost identical shell thicknesses.

Possible ^^unnaturaV’ variation. — Several nonpasserines and two large pas-
serines have undergone statistically significant shell thinning since the use
of DDT began ( Ratcliffe, 1970), but this aspect has not been investigated in
what are perhaps the most ecologically important of all birds, moderate or
small-sized passerines. To determine whether the shells of Cedar Waxwing
eggs have also become thinner, a series of pre-1920 eggs was measured. These
eggs are in the U.S. National Museum and were collected in various parts
of the waxwing’s range. The data (comparison 4, Table 1) strongly suggest
that current waxwing eggs have thinner shells than older ones. The degree
of thinning ( 3.2 per cent ) is probably not severe enough to have a significant
effect on the population size of the Cedar Waxwing. But, incomplete records
made it impossible to determine the incubation status of all of the old eggs,
and some heavily incubated eggs may be included in the sample. Thus, the
shell thicknesses of the old eggs may be biased by being too low whereas in
the sample for the recent eggs, all the eggs with development have been
excluded (comparison 4, Table 1). Therefore, the degree of thinning may
be greater than is indicated by the comparison in Table 1. Furthermore,
even a slight degree of thinning may have a deleterious effect on individual

Stephen I.
Rothstein

EGGSHELL THICKNESS IN WAXWINGS

473

reproductive output, since the shell thickness previously extant was presumably
better adapted than the possibly unnaturally thinned one reported here.

Based on the available evidence it would be merely speculative to suggest
a causal relationship between chlorinated hydrocarbons and the probable
shell thinning in waxwing eggs reported here. However, given the widespread
nature of this type of causal relationship there is a possibility of its existence
in the waxwing and in moderate or small-sized passerines in general and
additional studies of eggshell thickness in such birds would be highly desirable.

SUMMARY

Eggshell thickness in the Cedar Waxwing was analyzed in relation to various factors
and the existence of important natural variation was demonstrated. Eggs from small
clutches have thicker shells than eggs from large clutches. Embryonic development results
in a thinning of the shell. Five other factors failed to significantly correlate with shell
thickness. Recent waxwing eggs appear to have slightly (3.2 per cent) thinner shells than
eggs collected before 1920. The possible significance of these findings to clutch size
determination and other factors as well as to pesticide studies is discussed.

ACKNOWLEDGMENTS

I thank E. S. Morton, J. R. Longcore, and W. H. Stickel for their advice on the manu-
script and 0. S. Pettingill, Jr., N. Roth, R. L. Zusi, and J. F. Kreitzer for their aid at
various stages of the study. Field work was done from the University of Michigan
Biological Station and supported by the Chapman Memorial Fund, the University of
Michigan and Yale University. I have held a NASA Traineeship at Yale University and
a Smithsonian Institution postdoctoral appointment during the course of the study.

LITERATURE CITED

Anderson, D. W., and J. J. Hickey. 1970. Oological data on egg and breeding charac-
teristics of Brown Pelicans. Wilson Bull., 82:14-28.

Berg, L. R. 1945. The relationship of clutch position and time interval between eggs to
eggshell quality. Poultry Sci., 24:555-563.

Bitman, j., H. C. Cecil, S. J. Harris, and G. F. Fries. 1969. DDT induces a decrease in
eggshell calcium. Nature, 224:44-46.

Blus, L. j. 1970. Measurements of Brown Pelican eggshells from Florida and South
Carolina. BioScience, 20:867-869.

Kreitzer, J. F. 1971. Eggshell thickness in Mourning Dove populations. J. Wildl.
Mgmt., 35:563-564.

Lack, D. 1968. Ecological adaptations for breeding in birds. Methuen and Co. Ltd.,
London.

Putnam, L. S. 1949. The life history of the Cedar Waxwing. Wilson Bull., 61:141-182.
Ratclifi’e, D. a. 1970. Changes attril)utable to pesticides in egg breakage fre(iuency
and eggshell thickness in some Britisli birds. J. Appl. Ecol., 7:67-115.

Romanoff, A. L., and A. J. Romanoff. 1949. The avian egg. John Wiley and Sons,
New York.

Rothstein, S. I. Variation in the incidenee of hatching failure in the Cedar Waxwing
and other species. Condor, in j>ress.

474

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill,
New York.

SiMKiss, K. 1961. Calcium metabolism and avian reproduction. Biol. Rev., 36:321-367.
SiMKiss, K. 1967. Calcium in reproductive physiology. Reinhold, New York.
Vanderstoep, J., and J. F. Richards. 1970. The changes in eggshell strength during
incubation. Poultry Sci., 49:276-285.

Wilhelm, L. A. 1940. Some factors affecting variations in eggshell quality. Poultry
Sci., 19:246-253.

CHESAPEAKE BAY CENTER FOR ENVIRONMENTAL STUDIES, SMITHSONIAN INSTITU-
TION, EDGEWATER, MARYLAND (PRESENT ADDRESS: DEPARTMENT OF BIOLOG-
ICAL SCIENCES, UNIVERSITY OF CALIFORNIA AT SANTA BARBARA, CALIFORNIA

03106). 20 MARCH 1972.

NEW LIFE MEMBER

]\Ir. Henry' Bell, 3rd has recently become
a Life Member of The Wilson Ornitholog-
ical Society. Mr. Bell lives in Chevy Chase,
Maryland and is a geologist with the U.S.
Geological Survey. He holds a degree from
the University of South Carolina and has
also attended the University of Pennsylvania,
Pennsylvania State University, and the Uni-
versity of North Carolina. His interests in
birds are of long standing. He is a Fellow
of the Geological Society of America and
a member of the AOU and the Maryland
Ornithological Society. Along with bird
study he counts woodworking and boating
as his hobbies. Mr. Bell is married with
no children.

VERNAL TESTES DEVELOPMENT IN
TROPICAL-WINTERING DICKCISSELS

John L. Zimmerman and James V. Morrison

SINCE 12-hour daylengths experienced by tropical-wintering species are
stimulatory to the hypothalamic — hypophyseal — gonad axis of temperate-
wintering species (Burger, 1953; Dolnik, 1963; Farner, 1961; Wolfson,
1960), the question of why these migrants do not complete gametogenesis
during the several months’ stay on their contranuptial area has been of interest
(Marshall, 1960; Wolfson, 1959a). It can be assumed that different tropical
migrants could adapt the regulation of their annual cycles in a number of
different ways or by a combination of different mechanisms in order to be
successful in their specific environments.

One possibility was suggested by Wolfson (19596) who hypothesized that
these migrants might respond to 12-hour daylengths at a slower rate than
temperate species so that gametogenesis cannot be completed until they are
exposed to the longer daylengths of their temperate breeding grounds. This
hypothesis is indirectly supported from work done on temperate species which
has shown that the rate of testes growth is proportional to the length of the
photoperiod (Lofts, Follett, and Murton, 1970) and hence birds wintering at
tropical photoperiods might be expected to have even a slower rate of testes
development. Another possibility could be that the refractory period of
tropical-wintering species is longer than that of temperate species and thus
they cannot begin to respond to photostimulation until just prior to the north-
ward journey (Marshall, 1959). Both these hypotheses receive indirect sup-
port from the observation that gonad growth begins for tropical migrants on
the winter range, but it does not appear to progress very far (Rowan and
Batrawi, 1939; Marshall and Williams, 1959).

Lofts and Murton (1968:350) stated that “birds that are photosensitive
to medium northern daylengths have had to evolve adaptations if they migrate
to near or across the equator, in particular they require to have long refractory
periods and a slow response to stimulatory daylengths once they are out of
the refractory phase.” As far as we know, however, this generalization based
on the hypotheses of Wolfson and Marshall has not been supported by any
direct evidence.

The Dickcissel (Spiza americana) breeds in temperate North America and
I winters in the Neotropics north of Amazonia. Although we have not shown
that there is a relationship between this species’ natural photoperiod experience
and the regulation of its annual gonadal cycle, Morrison (1971) has demon-
strated in post-breeding adults that after approximately 8 weeks exposure to

475

476

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

a 12-hour photoperiod (around mid-November), precocial gonadal develop-
ment can be stimulated by the 15-hour photoperiod that they would experience
on the breeding grounds. These results show that a 12L-12D photoperiod
regime will terminate photorefractoriness in the Dickcissel and that the length
of its refractory period is similar to that of many Temperate Zone species
(Earner, 1959; Shank, 1959; Wolfson, 1958). It seems, therefore, that a
prolonged refractory period is not the mechanism this species uses to prevent
the development of the reproductive state while on the wintering grounds.

The following data on the rate of testes growth and the magnitude of the
response in wild birds living under their naturally-occurring photoperiod are
presented to test the slower rate of response hypothesis.

METHODS

Male Dickcissels were collected from wild populations on the wintering grounds in
Panama and the Canal Zone (9° N) from 19 January through 2 May 1961, and the length
of each testis was measured in millimeters. The daylengths during this period of collection
ranged from 11 hours, 40 minutes to 12 hours, 28 minutes. Similar data were obtained
on the breeding grounds in Illinois (40° N) from birds collected during May, June, July,
and August in 1961 and 1962.

In order to convert testis length into weight, Morrison in the course of his work on
the refractory period measured the length of the testis and then after treatment according
to the methods used by Wilson (1968), obtained their weight in milligrams. He calculated
the following relationship:

log testis wt. (mg) = -0.5845 3.0696 log testis length (mm).

In the quantification of the gonad growth rate from data collected by photostimulation
of receptive birds under laboratory conditions, the time axis is calibrated according to
days since the beginning of exposure to the stimulatory photoperiod. This, of course, is
not possible with a free-living population, since day zero is not known. In order to cal-
culate k, the logarithmic testicular growth-rate constant f = slope of the time X log weight
regression), the logarithm of the combined weight of both testes was plotted against the
date of collection. Then the linear portion of the curve was identified by inspection, and
28 February was selected as day 1. A linear regression of the logarithm of the combined
testes weight as a function of time was computed through 2 May as day 64. The natural
photoperiod during this period ranged from 11 hours, 56 minutes on day 1 to 12 hours,
28 minutes on day 64, averaging 12 hours, 13 minutes.

RESULTS

Figure 1 is a semi-log plot of the combined testes weights according to the
date of collection. Even though Dickcissels will respond under experimental
exposure to 15 hours of light in mid-November, under the natural photoperiod
conditions of their wintering grounds the testes are still small in January.

This figure also includes the linear regression calculated for the period from
28 February through 2 May, which is expressed by the following equation:

log wt. = 0.2757 + 0.03114 t.

Zimmerman and TESTES DEVELOPMENT IN DICKCISSELS 477

Fig. 1. Combined testes’ weights of wild Dickcissels collected on both the winter and
summer ranges.

' in which “wt” is the comhined testes weight in milligrams and “t” is in days.
I beginning with 28 February equal to day 1. The logarithmic testicular growth-
I rate constant, k, is thus equal to 0.03114 dayh It is also apparent that a
■ growth rate of this magnitude will lead to testes of breeding size by the time
, the population migrates to and becomes territorial on its breeding range in
I mid-May (dashed extension of linear regression in Figure 1).

478

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

The average weight of the combined testes in Illinois is 439.23 ± 21.77 mg
(SE, n = 28). Birds collected in June and July had swollen seminal vescicles,
indicative of the production of spermatozoa. Even the bird collected on 19
July whose combined testes weight was only 256 mg was producing sperm.
Finding functional breeding testes of such a wide range in size apparently
is not unusual (Dolnik, 1963).

DISCUSSION

The temperate-wintering White-crowned Sparrow (Zonotrichia leucophrys
gambelii) has a k value for adult males on a 12-hour photoperiod equal to
0.0225 (Earner and Wilson, 1957). If the same ratio between growth rates
of first year birds and adults that occurs in the White-crowned Sparrow [ k of
first year males = 1.16 k of adults) is valid for adult Chaffinches [Fringilla
coelebs) then the k of first year males which equals 0.0213 in this temperate
species has a value of only 0.0184 in adults at a 12-hour photoperiod ( Dolnik,
1963) . Both these values are less than the 0.03114 computed for the logarith-
mic testicular growth-rate constant in the Dickcissel at a 12-hour photoperiod,
and therefore the slower growth rate hypothesis is rejected for this tropical-
wintering species.

Hamner and Stocking (1970) have similarly rejected both the prolonged
refractory period hypothesis and the slow growth rate hypothesis for a trans-
equatorial migrant, the Bobolink {Dolichonyx oryzivorus) .

The question therefore still remains open as to why the testes do not begin
to develop earlier than they do. The energy resources of the environment do
not appear to be the main limiting factor. Although the prenuptial molt is
typically completed prior to the onset of gonadal growth, the development of
the testes is coincident with fat deposition and migratory behavior ( Zimmer-
man, 1965) .

Hamner (1968) presents the following observations from his studies of the
photoperiod control of the gonadal cycle in the House Finch {Carpodacus
mexicanus) : 1) the termination of photorefractoriness can be accomplished
by daylengths as long as 14 hours or as short as 6 hours and in all cases the
termination is completed in the same time interval, 2 months; 2) wild birds
that are photosensitive in the autumn experience a daylength of 12 hours but
show no gonadal growth while the same daylength does induce rapid game-
togenesis in the spring; 3) the renewal of photosensitivity is a gradual process
in that the long-day effect on birds in the fall is not as great as the same long
daylength in the winter; and 4) using an interrupted night technique on
photosensitive birds, there was a change in circadian sensitivity from October
to January in that this period of photosensitivity shifted from 20 hours after
dawn in the October birds to 12 hours after dawn in the January birds.

S”"" TESTES DEVELOPMENT IN DICKCISSELS 479

Hamner hypothesized that there are two components in the House Finch’s
refractory period. The first phase, the “absolute refractory period,” follows
immediately after breeding and is a period during which even continuous
light treatment is non-stimulatory and whose duration is independent of the
photoperiodic environment. The absolute refractory period is then followed
by a period of “relative refractoriness” during which the bird initially is
insensitive to daylengths equal to or shorter than those to which it had been
previously exposed but this insensitivity is affected by the photoperiod regime
it is experiencing so that as daylengths decrease in the fall there is a shifting
of a threshold for stimulation until finally this threshold reaches a daylength
less than that of the actual environment at that time and light again becomes
stimulatory on the system.

On the basis of Hamner ’s (1968) suggested mechanism, we hypothesize that
Dickcissels escape absolute refractoriness soon after their arrival on the winter
range, but still remain in a state of relative refractoriness to the tropical
photoperiod. Some time in February, as a result of the continued lowering
of the photoperiodic threshold, Dickcissels are released from relative refrac-
toriness and gonad growth begins.

Since we have not been able to illustrate in the tropical-wintering Dickcissel
that there is a refractory period longer than that of temperate species or a
slower rate of testes growth in response to the naturally-occurring photoperiod
in the spring than has been shown for temperate species, we suggest that there
is no special adaptation for the regulation of its gonadal cycle because of its
wintering at a latitude where it seldom experiences days of less than 12 hours
duration. It, like temperate species (Wolfson, 1960), is simply specifically
adapted to the photoperiodic environment it experiences as a result of its
migratory behavior.

SUMMARY

Sizes of testes obtained from wild populations of the Dickcissel on its wintering range
in Panama and the Canal Zone were used to compute a logarithmic testicular growth-rate
constant, k, equal to 0.03114 day"^. Since this value is not less than that of temperate-
wintering species exposed to 12-hour photoperiods, the slower growth rate hypothesis is
rejected for the Dickcissel.

Furthermore, this k value is great enough to lead to the development of breeding-size
testes.

Since previously completed work by Morrison led to the rejection of the prolonged
refractory period hypothesis, the question of why gonads of wintering Dickcissels do not
begin their development earlier is still not answered. A mechanism based on the notions
of Hamner (1958) is suggested as a hypothesis yet to l)e tested.

ACKNOWLEDGMENTS

I The collection of testes data was supported by NSF grant G14251 awarded to S. C.

I Kendeigh at the University of Illinois. Definition of the refractory period and analysis

I

I

480

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

of testes growth was funded by NSF grant GB-6087 awarded to J. L. Zimmerman. We
would also like to thank F. E. Wilson for his suggestions during the course of this work
and the preparation of this paper.

LITER-A.TURE CITED

Burger, J. W. 1953. The effect of photic and psychic stimuli on the reproductive cycle
of the male Starling, Sturnus vulgaris. J. Exp. Zook, 124:227-240.

Dolnik, V. R. 1963. Quantitative study of vernal testicular growth in several species of
finches ( Fringillidae ) . Dokl. Akad. Nauk SSR. 149:191-193. (In Russian, transla-
tion by F. K. Pious, Jr., courtesy of S. C. Kendeigh.)

Farner, D. S. 1959. Photoperiodic control of annual gonadal cycles in birds. In Photo-
periodism and related phenomena in plants and animals, R. B. Withrow^, Ed. Amer.
Assoc. Advance. Sci., Washington, D.C., pp. 717-750.

Farner, D. S. 1961. Comparative physiology: Photoperiodicity. Ann. Rev. Physiol.,
23:71-96.

Farner, D. S., and A. C. Wilson. 1957. A quantitative examination of testicular growth
in the WTite-crowned Sparrow. Biol. Bull., 113:254-267.

Hamner, W. M. 1968. The photorefractorv" period of the House Finch. Ecology, 49:
211-227.

Hamner, W. M., AND J. Stocking. 1970. Why don’t Bobolinks breed in Brazil? Ecology.
51:743-751.

Lofts, B., B. K. Follett, and R. K. Murton. 1970. Temporal changes in the pituitary-
gonadal axis. Mem. Soc. Endocrinol., 18:545-575.

Lofts, B., and R. K. Murton. 1968. Photoperiodic and physiological adaptations regu-
lating avian breeding cycles and their ecological significance. J. ZooL, 155:327-394.

Marshall, A. J. 1959. Internal and external control of breeding. Ibis, 101:456-478.

Marshall, A. J. 1960. Annual periodicity in the migration and reproduction of birds.
Cold Spring Harbor Symp. Quant. Biol., 25:499-505.

Marshall, A. J., and M. C. Williams 1959. The prenuptial migration of the Yellow-
Wagtail {Motacilla flava) from latitude 0.04' N. Proc. Zool. Soc. London, 132:313-
320.

Morrison, J. V. 1971. Evidence for a refractory period in the Dickcissel (Spiza amer-
icana) . Unpubl. M.S. Thesis, Kansas State University.

Shank, M. C. 1959. The natural termination of the refractory period in the Slate-
colored Junco and in the White-throated Sparrow\ Auk, 76:44-54.

Rowan, W., and A. M. Batrawi. 1939. Comments on the gonads of some European
migrants collected in East Africa immediately before their spring departure. Ibis,
(ser. 14) 3:58-65.

Wilson, F. E. 1968. Testicular growth in the Harris’ Sparrow. Auk, 85:410-415.

WoLFSON, A. 1958. Regulation of refractor)- period in the photoperiodic responses of
the White-throated Sparrow. J. Exp. Zool., 139:349-379.

WoLFSON, A. 1959a. Ecologic and physiologic factors in the regulation of spring migra-
tion and reproductive cycles in birds. In Comparative endocrinology, A. Corbman.
Ed. John Wiley and Sons, Inc., New York, pp. 38-70.

\^'oLFSON, A. 19596. Role of light and darkness in regulation of refractory period in
gonadal and fat cycles of migratory birds. Physiol. Zool., 32:160-176.

TESTES DEVELOPMENT IN DICKCISSELS 481

WoLFSON, A. 1960. Regulation of annual periodicity in the migration and reproduction
of birds. Q)ld Spring Harbor Symp. Quant. Biol., 25:507-514.

Zimmerman, J. L. 1965. Carcass analysis of wild and thermal-stressed Dickcissels.
Wilson Bull., 77:55-70.

DIVISION OF BIOLOGY, KANSAS STATE UNIVERSITY, MANHATTAN, KANSAS 66506.
( PRESENT ADDRESS, JVM : DEPARTMENT OF BIOLOGY, RIVERSIDE CITY COLLEGE,
RIVERSIDE, CALIFORNIA.)

NEW LIFE MEMBER

A new addition to the list of Life Mem-
bers of the Wilson Ornithological Society
is Dr. David F. Parmelee, one of the recog-
nized authorities on bird life of the high
Arctic. Dr. Parmelee is currently Professor
of Biology and Chairman of the Field Biol-
ogy Program at the University of Min-
nesota. He has made numerous expeditions
to the Arctic and published approximately
50 papers on his observations there as well
as two small books. Our picture shows him
(with friend?) on one of these trips. Dr.
Parmelee holds degrees from Lawrence Col-
lege, and the University of Oklahoma. He
is a member of the Cooper Society, the
state ornithological Societies of Kansas,
Oklahoma, and Minnesota, and an Elective
Member of the AOU. Besides his scientific
work he is also a skilled bird photographer
and painter. Dr. Parmelee is married and
has one daughter.

GENERAL NOTES

Tool-using by a Double-crested Cormorant. — In a recent review of tool-using in
vertebrates, van La^dck-Goodall (Tool-using in primates and other vertebrates, In Adv.
Study Behavior, Lehrman et al.. eds., vol. 3, 1970) defines a tool-using performance

. . as the use of an external object as a functional extension of mouth or beak, hand
or claw, in the attainment of an immediate goal.” She adds that "This goal may be related
to the obtaining of food, care of the body, or repulsion of a predator, intruder, etc.” Later,
van La^vick-Goodall describes tool-using performances by a variety of birds, but she does
not give examples of birds using tools in relation to care of the body.

My purpose here is to describe an act of tool-using by a Double-crested Cormorant
(Phalacrocorax auritus) in relation to care of the body. Additionally, the obsenation is
unusual in that the bird made use of one of its omti bodily products as a tool.

On 13 February 1970. I was seated on the edge of Florida Bay in the to'WTi of La>ton.
Long Key, in the Florida Keys. About 50 feet from my position a long finger of debris,
stones, and sand extended out into the bay. This man-made finger was a regular resting
place for numerous cormorants, pelicans, gulls, and herons. Chi this particular day I was
watching the behavior of foraging herons as they waded in the shallows between my
position and the finger of solid fill. After the herons left I turned my attention to a group
of five adult cormorants resting on the fill. Two of the cormorants were dozing while the
remainder were preening and head-scratching.

As I watched one of the preening adults it would stretch its head and bill, in what
seemed like an awkward manner to me, back towards its uropygial gland, squeeze the
gland then apply the secretion to its iGng feathers -vs-ith broad sweeps or dabs of tbe
anointed bill. Suddenly, as the cormorant postured with its iGngs iddespread. one of its
secondary' feathers, loosened by the molting process, blew away from the extended wing
and landed about a foot in front of the cormorant. The bird turned and stared at the
feather for several moments, then it picked up the feather and held it cross’sGse in its biU.
It held this pose for several moments, then adjusted its grip on the feather's shaft so that
the object was held almost parallel wth the bill. The cormorant then deftly applied the
tip of the feather to the preen gland by simply turning its head and extending the feather
towards the gland. Next, the cormorant used the feather as a brush by applying tbe preen
gland secretion to its extended right wing, doing so by making side to side sweeps with
its head, the bill still holding the shaft of the feather. The sweeping brush-like motions
were made smoothly and unhurriedly.

Tlie bird continued this beha\-ior, making three sets of such sweeping motions over its
extended wngs, once on the right wing, twice on the left, each sweep preceded by an
application of the secondary feather tip to the preen gland. The gland was not manipulated
by the bill after the feather had been grasped the first time. At no time did the cormorant
modify the tool so as to render the "brush” a more efficient tool.

A passing motorboat startled the cormorants and the tool-using bird opened its bill
slightly; a light easterly breeze wafted the secondary feather from the bird’s bill to a
place about a foot to the cormorant’s left. The bird stared at the feather for a few moments,
reached out and picked it up and manipulated it for a few moments more. Then the bird
released the feather and the breeze carried it out over the bay to a point about 20 feet
from the tool-user. The bird made no effort to retrieve its tool, and further obsenation
of the tool-user and the other cormorants failed to reveal any further tool-using.

This example of tool-using is not only unusual in the startling nature of such an act by
a non-mammalian vertebrate, but it is of further interest in that the bird made use of

-F82

December 1972
Vol. 84, No. 4

GENERAL NOTES

483

one of its own bodily products, a feather, to attain a goal in what seemed to me to be
an easier performance than its typical preening and oiling behavior. Furthermore, this
observation adds another facet to the use of tools by birds and other vertebrates — use of
a tool to care for the surface of the body by means of a brush. — Andrew J. Meyerriecks,
Department of Biology, University of South Florida, Tampa, Florida 33620, 11 February
1972.

Cold hardiness and the development of homeothermy in young Black-hellied
Tree Ducks. — The Black-bellied Tree Duck {Dendrocygna autumnalis) is a southern
species and dump nesting is extensive in Texas (Bolen, 1962 and 1967). Dump nests are
the results of several females laying eggs in the same nest. Large broods with as many
as 43 ducklings have been recorded and are a direct result of these dump nests (Cain,
1970).

Koskimies and Lahti (1964) have shown that surface ducks (Mallard, Anas platy-
rhynchos, and Common Teal, A. crecca) could not maintain combined broods because the
ducklings were not cold hardy. Combined broods are common however in most genera of
diving ducks, such as Aythya and Melanitta (Hochbaum, 1944) and Bucephala and Mergus
(Mendall, 1958).

This study was conducted to determine the cold-hardiness and ontogeny of thermo-
regulation in the Black-bellied Tree Duck young and relate this to possible success of
large brood that result from dump nests.

METHODS

Forty ducklings hatched in forced-air incubators were kept for 3 days at 42° C and
then placed at 32° C. Another 40 ducklings were placed in outdoor pens at one day of
age without a brooder.

The fate of 22 ducklings found abandoned in nests were recorded for comparative
purposes.

During the temperature regulating experiment ducklings were placed in a perforated
paper box in a dark cabinet held at 0° C. At 5-minute intervals a quick-registering
thermister was inserted into the duckling’s mouth to a depth of 40 mm. This core
temperature was then recorded on a Yellow Springs Inc. telethermometer. Cotton gloves
were worn to reduce heat transfer to the ducklings.

The ducklings were removed from the cold when they were unable to stand up, or after
30 minutes, and returned to their initial room temperature. Maintenance of the ducklings
followed the procedure used by Cain (op. cit.).

RESULTS AND DISCUSSKJN

Temperature regulation.— D\xc\d\ngs of this species apparently are unable to maintain
a constant body temperature for several days after hatching (Fig. 1) when exposed to a
low ambient temperature. The body temperature dropped rapidly (1.26° C per minute)
for ducklings 1 day old and slowed as the age increased (0.50° C per minute for 6 day
old ducklings). At 12 days of age the rate of cooling was 0.35° C per minute for 20
1 minutes and then the ducklings maintained a steady temperature of 32° C.

! The slower rate of cooling for older ducklings may be due partly to an increase in
^ metabolism (Cain, in prep.), a decreased surface to volume ratio as the duckling increased

I in weight, and the increased insulation afforded by the development of the juvenal down

1 between 10-12 days of age (Cain, 1970). A similar cooling trend for nestling House W reus

484

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 1. The relationship between body temperature and time exposed to the ambient
temperature (0° C) as a function of age.

^Troglodytes aedon) was reported by Kendeigh and Baldwin (1928) and for nestling
Cactus Wrens (Campylorhynchus brunneicapillus) as reported by Ricklefs and Hains-
worth (1968).

Cold-hardiness. — Both parents stay with the brood in this species even after the young
have attained flight (pers. observ.) and it is assumed that both adults contribute to the
brooding in the early stages. The importance of brooding may be seen in Table 1.
Ducklings not brooded died before 7 days of age and their body weight at death was
significantly lower than ducklings of the same age that were brooded.

This low degree of cold-hardiness, before thermoregulation develops, should restrict the
independence of the young Black-bellied Tree Ducks and increase the adult’s burden of
supplying energy. This may be a considerable amount for the parents of large broods
and this attentiveness may lead to the strong family bonds in this species.

I suggest then that large broods resulting from dump nests in south Texas may enjoy

December 1972
Vol. 84, No. 4

GENERAL NOTES

485

Table 1

Comparison of Ducklings Brooded Artifically and Those Not Brooded
The average body weight is for 7-day-old ducklings or as indicated.

Ducklings considered

Number

hatched

Number

survived

Per cent
survival

Body weight
( in grams )

Artificially incubated

Unbrooded

40

0

0

22.0^

Brooded

40

30

75

31.5

Wild caught

Unbrooded

10

0

0

21.51

Brooded

12

6

50

32.0

^ Average body weight at death.

a high success if adverse weather conditions do not occur during the first 10 days after
hatching. This high degree of success would be a function of the low energetic stress
upon the young themselves and the increased frequency of brooding because of both
parents being present.

ACKNOWLEDGMENTS

I wish to thank Dr. James Heath (Univ. of Illinois) for his review of the manuscript and
suggestions. Don Delnicki and Steve Labuda helped collect the eggs. Texas A&I Uni-
versity and the Texas Parks and Wildlife Department also provided needed assistance.
I especially want to thank Dr. S. Charles Kendeigh for his guidance and the financial
assistance provided by a National Science Foundation grant to him.

LITERATURE CITED

Bolen, E. G. 1962. Nesting of Black-bellied Tree Ducks in Texas. Audubon Field
Notes, 16:482-485.

Bolen, E. G. 1967. The ecology of the Black-bellied Tree Duck in southern Texas.

Unpubl. Ph.D. thesis, Utah State Univ., Logan.

Cain, B. W. 1970. Growth and plumage development of the Black-bellied Tree Duck,
Dendrocygna autumnalis (Linnaeus). Texas A&T Univ. Studies, 3:25-48.

Hociibaum, a. 1944. The Canvasback on a prairie marsh. Amer. Wildl. Inst., Wash-
ington.

Kendeigh, S. C., and S. P. Baldwin. 1928. Development of temperature control in
nestling House Wrens. Amer. Naturalist, 62:249-278.

Koskimies, J., and L. Lahti. 1964. Cold-hardiness of the newly hatched young in
relation to ecology and distribution of ten species of European ducks. Auk, 81:281-
307.

Mendall, H. L. 1958. The Ring-necked Duck in the northeast. Univ. Maine Studies,
2nd ser., 73:1-320.

Ricklefs, R. E., and F. R. Hainsworth. 1968. Temperature regulation in nestling
Cactus Wrens: Development of homeothermy. Condor, 70:121-127.

Brian Cain, Department of Zoology, University of Illinois, Urbana, Illinois 61820, 10
February 1972.

486

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Ruddy Ducks colliding with wires. — Cornwell and Hochbaum (Wilson Bull., 83:
305-306, 1971) remarked that anatid strikes on wires (fence, communications, and power)
occur commonly on the northern prairie breeding grounds, but go largely unnoticed and
unreported. The following observations, made near Minnedosa, Manitoba, during May-
August 1971 are offered in response to comments made by Cornwell and Hochbaum.

Incidental to carrying out weekly surveys of waterfowl breeding on potholes along roads
regularly used as a transect route, I recorded all dead birds encountered while walking
around ponds and while travelling by car. 1 noted the state of freshness of the carcasses
and their locations, before gathering them up for removal. I covered the same 250 km
of road every week; some 50 km of road served as a route for overhead lines.

Ten weekly three-day censuses were carried out, and freshly dead waterfowl were
observed during the course of seven of these. I recorded a total of 16 dead birds; eight
Ruddy Ducks {Oxyura jamaicensis) ; four Am. Coot (Fidica americana) ; two Blue-winged
Teal {Anas discors) ; one Mallard (Anas platyrhynchos) ; and one Pintail (Anas acuta).
Apart from the Pintail, the carcasses were located on the ground within 75 meters of the
nearest pond edge and within 30 meters (mean of 10 meters) of overhead wires. The
Pintail (an adult male) was found impaled on the top strand of a barbed wire fence
standing in water 30 cm deep.

Three Ruddy Ducks were found between 15 May and 15 June, and five were found after
15 June. The Mallard and Pintail were found in mid-May, and the two Blue-winged Teal
in the first week of June. The Coots were found in June. Apart from the Coots, which
were aged but not sexed, all of the dead birds were adult males. Since the surveys were
terminated before the end of August, the absence of juvenile birds is not so surprising.

Of a total of 50 adult Ruddy Ducks (24 females, 26 males) collected during my study
two males with defective wings were taken, and three crippled females were taken in
May. The crippled birds’ injuries were consistent with the type expected as a result of
colliding with wires. The birds were located on ponds close to overhead wires.

Stout (The nature and pattern of non-hunting mortality in fledged North American
waterfowl. Unpubl. M.S. thesis, Virginia Polytech. Inst., 1967) used information from
questionnaires and band recoveries to suggest that dabbling ducks are most often involved
in wire strikes and that males may be more vulnerable than females; perhaps because of
the “reckless” nature of pursuit flights. A comparison of absolute densities of all anatids
on ponds near overhead wires and generally in the study area, showed the Ruddy Duck
to be second to the Blue-winged Teal (Siegfried, unpubl.). However, the ratios favoring
the Ruddy Duck were nowhere near as high as the 67 per cent (Coot excluded) for relative
mortality as recorded here. While Stout (op. cit.) suggested that dabbling ducks are most
often involved in wire strikes, be does state, too, that next to the Mallard the Ruddy
Duck is most susceptible to mortality caused by striking overhead wires. Apparently,
then, a factor other than mere relative abundance of species is involved. Further, since
the Ruddy Duck does not perform pursuit flights, or any other kind of aerial courtship,
this behavior cannot be evoked as contributing to the disproportionate mortality.

A time and motion study of the Ruddy Duck’s daily behavior showed that, once on the
breeding grounds, the birds veiy^ seldom flew by day and that aerial movement was
virtually restricted to late evening twilight, starting just before darkness. During late
May, June, and July these flights were observed to involve only males, flying at low
altitude from one pond to another. In the study-area generally, there were more males
than females, but the sex ratio was too close to parity to account for the disproportionate
kill of males.

Apparently, females are most often involved in wire strikes early in the season during

December 1972
Vol. 84, No. 4

GENERAL NOTES

487

and shortly after arrival on the breeding grounds. Males, on the other hand, suffer
collisions throughout the season, apparently because they move around much more. The
fact that Ruddy Ducks normally fly only during and after dusk, and that they do not
climb steeply after taking wing, but rather perform one or two low and wide circles while
gaining altitude, adds to their risk of striking wires.

I am grateful to Dr. H. A. Hochbaum for commenting on the manuscript. For financial
support in North America, I am indebted to; Delta Waterfowl Research Station; Chapman
Memorial Fund of the American Museum of Natural History; South African Council for
Scientific and Industrial Research; University of Cape Town. The Canadian Wildlife
Service gave permission for the taking of specimens. — W. Roy Siegfried, Percy FitzPatrick
Institute of African Ornithology, University of Cape Town, Rondebosch, Cape Province,
South Africa, 9 February 1972.

A note on Golden Eagle talon wounds. — The recent slaughter of Golden Eagles
{Aquila chrysaetos) in Wyoming has again focused attention on the subject of eagle-
livestock relationships. The problem has been variously studied in many parts of the world
including the United States (Spofford, 1965, 1969; McGahan, 1968; Mollhagen et ah,
1972), Scotland (Brown and Watson, 1964), and Australia (Leopold and Wolfe, 1970).
An important aspect of these and related studies is the determination of whether the eagle
foods — especially lambs — have indeed been freshly killed (i.e. outright predation) or
secondarily secured as carrion.

Hence, emphasis has been placed on the field identification of wounds and other features
present on carcasses alledgedly killed by eagles. In Australia, Rowley (1970) thoroughly
examined the damage inflicted by Wedge-tailed Eagles {Aquila audax) and other car-
nivores on lambs whereas a similar but less exhaustive study was also undertaken in the
southwestern United States where Golden Eagles nest and overwinter (Wiley and Bolen,
1971; Boeker and Bolen, 1972).

Talon punctures, coincident with extensive subcutaneous hemorrhages, are a priori
indications of eagle predation despite the contrary opinion of some stockmen that talon
wounds are more often absent on eagle-killed lambs (and hence, in their view, that the
frequent absence of talon punctures on dead lambs does not preclude assigning the cause
of death to eagles) . Lambs are instead killed, according to some stockmen, by the impact
of an eagle attacking with its feet closed in a “fist” or in some other way that does not
involve the use of their talons.

We wish to cite an instance where deep talon punctures were indeed made by a Golden
Eagle attacking decoys set at Muleshoe National Wildlife Refuge in Bailey County, Texas,
on 23 January 1971. The decoy attacked was one of 24 female Pintail decoys set at
Paul’s Lake immediately within the refuge’s eastern boundary. The attack occurred at
10:15 when the eagle flew across the lake and approached the decoys at an altitude of
about 15 yards; the bird suddenly dropped onto the back of the decoy. The impact of
the attack, even without the advantage of a long stoop, drove the eagle’s talons deeply
into the back and side of the plastic-bodied decoy leaving ample — and obvious! — evidence
of puncture (Fig. 1). Later in the day, after the decoys had been left untended for several
hours, another decoy was discovered with a fouled anchor cord; examination of this decoy
showed that it, too, had deep punctures similar to the earlier “wounds” inflicted by the
Golden Eagle. Sperry (1957) also described the attack of a Golden Eagle “. . . with
distended talons” on a male Pintail decoy, although the eagle in this instance approached
the decoy by wading.

488

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Fig. 1. Golden Eagle talon damage inflicted on a plastic Pintail decoy at Muleshoe
National Wildlife Refuge, Texas. Upper picture shows overall view of the damage; in
the lower photo, the depth of the punctures are visible at two points on the decoy’s back.

December 1972
Vol. 84, No. 4

GENERAL NOTES

489

Talon wounds are equally present on ducks and geese attacked by Golden Eagles. Duck
carcasses (listed only as Anas spp.) taken from a Golden Eagle nest showed . . talon
marks on the shoulders and neck” (Arnold, 1954). Tener (1954) found several talon
punctures along the back of a Canada Goose {Branta canadensis) attacked by a Golden
Eagle whereas Wallace (1937) reported that an eagle “. . . buried its talons” into a
domestic goose (Anser sp.). Recently, Kelleher and O’Malia (1971) watched a Golden
Eagle snatch a drake Mallard in mid-air and hold it in its talons. Federal Game Manage-
ment Agent Don Krieble reports that he has seen Golden Eagles at Muleshoe National
Wildlife Refuge make mid-air attacks on waterfowl suffering from avian cholera; talons
were used prominently in these strikes.

We thus cite our observation, with these others, as evidence that eagles indeed follow
the expected course of action when striking at prey. Specifically, eagles use their for-
midable talons which, of course, are important adaptations to their mode of feeding.
Contentions that carcasses of eagle prey are free of talon punctures would thus seem to
be largely without merit.

LITERATURE CITED

Arnold, L. W. 1954. The Golden Eagle and its economic status. U.S. Fish and Wildl.
Serv. Circ. 27, Washington, D.C.

Boeker, E. R., and E. G. Bolen. 1972. Winter Golden Eagle populations in the south-
west. J. Wildl. Mgmt., 36:477-484.

Brown, L. H., and A. Watson. 1964. The Golden Eagle in relation to its food supply.
Ibis, 106:78-100.

Kelleher, J. V., and W. F. O’Malia. 1971. Golden Eagle attacks a Mallard. Auk, 88:
186.

Leopold, A. S., and T. O. Wolfe. 1970. Food habits of nesting Wedge-tailed Eagles,
Aquila audax, in south-eastern Australia. CSIRO Wildl. Res., 15:1-17.

McGahan, j. 1968. Ecology of the Golden Eagle. Auk, 85:1-12.

Mollhagen, T. R., R. W. Wiley, and R. L. Packard. 1972. Prey remains in Golden
Eagle nests: Texas and New Mexico. J. Wildl. Mgmt., 36:784-792.

Rowley, I. 1970. Lamb predation in Australia: incidence, predisposing conditions, and
the identification of wounds, CSIRO Wildl. Res., 15:79-123.

Sperry, C. C. 1957. Golden Eagle attacks decoy duck. Wilson Bull., 68:107-108.

Spofford, W. R. 1965. The Golden Eagle in the Trans-Pecos and Edwards Plateau of
Texas. Audubon Conserv. Rept. No. 1, Natl. Audubon Soc., New York.

Spofford, W. R. 1969. Problems of the Golden Eagle in North America. In Peregrine
Falcon populations (J. J. Hickey, Ed.), Univ. Wisconsin Press, Madison.

Tener, J. S. 1954. Three observations of predators attacking prey. Canadian Field
Naturalist, 68:181-182.

Wallace, G. J. 1937. Notes from Vermont. Auk, 54:547.

Wiley, R. W., and E. G. Bolen. 1971. Eagle-livestock relationships: livestock carcass
census and wound characteristics. Southwestern Naturalist, 16:151-169.

John R. Alford, III and Eric G. Bolen, Department of Range and Wildlife Manage-
ment, Texas Tech University, Lubbock, Texas 79409, 10 February 1972.

Roadside raptor census in Colorado — Winter 1971— 72. From 11 November 1971
through 15 February 1972, 13 counts of wintering birds of prey were made in the grass-
lands and wheatlands east of Colorado Springs and Fort Collins, Colorado. Two routes

490

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Table 1

Frequencies of Raptors on Plains East of Colorado Springs and Fort Collins,

Winter 1971-72

Species

Total number
observed

Miles traveled
per individual

Rough-legged Hawk (Buteo lagopus)

107

10

(9)

Golden Eagle {Aquila chrysaetos)

57

18

(52)

Prairie Falcon {Falco mexicanus)

36

29

(27)

Sparrow Hawk {Falco sparverius)

34*

31

(52)

Marsh Hawk {Circus cyaneus)

24

44

(22)

Ferruginous Hawk {Buteo regalis)

20

52

(112)

Bald Eagle {Haliaeetus leiicocephalus)

6

175

(186)

Red-tailed Hawk {Buteo jamaicensis)

4

262

(4191

Pigeon Hawk {Falco columbarius)

3

349

(186)

* Eleven of the total were observ ed on 11 November 1971.

■were foUo'vved, the first, extending south and east from Colorado Springs, "vvas approxi-
mately 150 miles long, inyohing a total observation area of approximately 48,000 acres
(a linear strip 150 miles long and F2 mile wide). The second route, beginning 8 miles
east of Fort CoUins, was 54 miles long and involved 17,280 acres. A total of 1,048 miles
was driven during the censuses (910 miles near Colorado Springs, and 138 miles near
Fort (ToUins) . Both routes were chosen because of the abundance of utility poles upon
which raptors perch. Observations were generally made early in the morning, on days
when the "wind was light (0-8 mph), using binoculars and a spotting scope. Table 1
summarizes the frequencies of raptors obseixed. The data in parenthesis were collected
in the same area by Enderson (Wilson Bull., 77:82-83, 1965) in the -vsinters of 1962-63
and 1963-64.

A total of 306 raptors was seen (one even* 3.4 miles) , including 15 buteos not identified
to species. Although the 11 Sparrow Hawks obsened on 11 November 1971 were not
identified -with respect to sex, 17 of 21 identified to sex on the follo4\*ing counts were
males. Of 20 Marsh Hawks identified with respect to sex, 16 were males. Three of four
Bald Eagles identified with respect to age were adults.

Enderson (op. cit.) counted raptors along nearly identical routes about 10 years ago,
traveling 1,675 miles. He recorded Marsh Hawks and Pigeon Hawks t^vice as often as
we did. e recorded Sparrow Hawks 1.7 times more often, and Ferruginous Hawks 2.1
times more often than he did. For the latter species, these and nesting season obseivations
tend to support our impression that Ferruginous Hawks are more abundant in the region
in the last two years. We recorded more Red-tailed Hawks, but three of four were seen
along a creek just outside of Enderson’s route.

In this sur\*ey. Golden Eagles, second only to Rough-legged Hawks in abundance, were
seen 2.9 times more frequently than a decade ago. — David Johnson and James H. Ender-
son, Department of Biology, Colorado College, Colorado Springs, Colorado 80903, 14 April
1972.

December 1972
Vol. 84, No. 4

GENERAL NOTES

491

Sparrow Hawk eats European corn borer. — Because insect prey of the Sparrow
Hawk {Falco sparverius) are usually not identified to species, cases in which such
determinations are made, especially when unlikely prey are consumed are of interest.

On 4 April 1970 a Sparrow Hawk was caught on a Balchatri trap near Newark, Licking
County, Ohio. A few minutes after capture, the bird died of unknown causes. The
specimen was a male with enlarged testes and weighed 113.7 g. The stomach contained
71 European corn borer (Ostrinia nubilalis Hiibner) larvae of various sizes. This prey
item comprised about 95 per cent of the stomach contents. Other contents were two
small pellets composed wholly of fur of the meadow vole, Microtiis pennsylvanicus. At
this time of year in central Ohio, Sparrow Hawks subsist principally on small rodents,
particularly the meadow vole.

Since during the early spring European corn borer larvae are dormant within the stalks
of corn plants and emerge as adults in June, this insect would not be regularly incor-
porated into a Sparrow Hawk’s diet. In a search of the literature, we found no records
of Sparrow Hawks eating this insect, although Lepidopterans in general frequently com-
prise a substantial part of this falcon’s diet. The significant aspect of this record is that
these larvae were eaten so early in the season. In fact, it is surprising these insects
were eaten at all. One may speculate on the source and manner in which the hawk
obtained such a large number of larvae. Early spring plowing or disking of fields may
have broken corn stalks exposing many larvae to predators. — Clive A. Petrovic, F. T.
Stone Laboratory, The Ohio State University, Columbus, Ohio 43210 and Gregory S.
Mills, Dept, of Zoology, The Ohio State University, Columbus, Ohio, 3 April 1972.

Black Rails hit a television tower at Raleigh, North Carolina. — In 1969 and 1970
two Black Rails (Laterallus jamaicensis) collided with the WRAL television tower, nine
miles southeast of Raleigh, North Carolina. This tower is 1,175 feet high, and its base
is 190 feet above sea level.

The first bird, a female with unossified skull, died the night of 19-20 September 1969.
Its weight was 32.9 g; fat class, 2; chord of wing, 78 mm; culmen from skull, 13.2 mm.
The crop contained 14 quartz particles each measuring about 1x1 nim. The stomach
contained no food. During the night of 19-20 September there was rain, wind of 7-12
mph from N to NNE, and the ceiling was 400 to 1,500 feet.

The second bird, a male with an unossified skull, died the night of 27-28 September
1970. It weighed 31.7 g; fat class, 3; weight of subcutaneous fat, 2.6 g; culmen from
skull, 14 mm. The stomach was empty. During the night, there was rain, and the wind
was 9-11 mph from the NE. The ceiling lowered to 100 to 1,200 feet.

These are the first records of the Black Rail in central North Carolina since 1902. In
1891, C. S. Brimley found Black Rails nesting in the present town of Raleigh (Ornithol-
ogist and Oologist, 16:26, 1891). However, it is unlikely that the tower killed birds were
local birds, since local Black Rail habitat has long since disappeared. The two birds
probably originated from a coastal area to the northeast. That such a flight is possible
is indicated by the finding of a Seaside Sparrow i Ammospiza maritima) at this tower
(Wilson Bulletin, 83:102, 1971). A Clapper Rail (Rallus longirostris) also has hit this
tower (N. C. State Museum specimen No. 2671, picked up 28 September 1965).

Black Rails are rarely killed in collisions with man-made structures. There are only
10 recorded casualties, all from Florida (Bull. Tall Timbers Res. Sta. No. 8:51, 1967; Fla.
Nat. 39:53, 1966; Am. Birds, 25:723, 1971). Since Black Rails are nocturnal birds and
also have a limited distribution, it is no wonder they are rarely found colliding with man-

492

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

made obstacles. Ho-vvever, it is more unusual that they should be found at an inland
television tower. The nearest knoTNTi present breeding site for Black Rails are the marshes
of Chesapeake Bay, about 200 miles NE of Raleigh.— Micou M. Browne and William
Post, Zoology Department, \orth Carolina State University, Raleigh, 27607, 3 February
1972.

Eggshell removal in the Spotted Sandpiper. — Tinbergen and co-workers suggested
that the latency of eggshell removal depends on two factors: the importance of ciyptic
coloration to protection of the eggs and young and the extent of predation on unguarded
young (Tinbergen, Broekhagsen, Feekes, Houghton, Kruuk, and Szulc, Behaviour, 19:
74-117, 1962; Tinbergen, Nat. Hist., 72:28-35, 1963). Partially hatched and wet gull
chicks are subject to hea\y intraspecific predation (Tinbergen, 1963, op. cit.). Removal
of conspicuous eggshells is often delayed until the chicks dr>-. The Ringed Plover
i Charadrius hiaticula) and Oystercatcher ^ Haematopus ostralegus) are less subject to the
intraspecific predation found in gulls, depend on cr>ptic coloration for escape, and remove
their eggshells much sooner after hatching than do the gulls. But this is all the comparative
evidence Tinbergen mustered in support of his hypothesis.

On 14 July 1970 I saw an adult Spotted Sandpiper i Actitis macularia) flying over a
speckled alder thicket and holding an eggshell in its bill. The shell hung down, pointed
end forward. The bird called loudly ever>' 5 sec during its entire flight. It landed on
a plank bridge and placed the eggshell on the bridge. It stood by the shell for a short
time then flew through the alders in the general direction of its nest. It continued to
call, a loud peet-iveet whistle, while standing by the shell, but became silent upon depart-
ing.

The eggshell, the larger portion with the pointed end, the blunt end haHng been
knocked out, was damp inside with the allantoic membranes still clinging to the inner
surface. The shell was deposited about 40 m from the nest.

Four chicks were present in the nest which less than two hours earlier had contained
only two chicks. There were no eggshells in the nest nor TNUthin 1 m of the nest. Two
of the chicks were dry, one was damp, and the fourth was wet.

I had checked the nest two hours earlier, thus no more than two hours could have
elapsed between hatching and eggshell removal. The wet membranes lining the eggshell
and the chick’s wet do4\Ti would seem to indicate that only a few minutes had elapsed.
The Spotted Sandpiper, a solitar>-nesting species not subject to intraspecific predation on
wet chicks, a species whose eggs and young are cn-ptically colored, appears to remove
eggshells quickly as predicted by Tinbergen.

I made these observations while doing research supported by a grant from the Surdna
Foundation to Bowdoin College. — Edward H. Burtt, Jr.. Department of Zoology, Uni-
versity of fUisconsin, Madison, Wisconsin 53706, 14 February 1972.

Stomach capacity in the Common Nighthawk. — Analyses of the stomach contents
of the Common Nighthawk (Chordeiles minor) have occasionally revealed the presence
of surprisingly large numbers of insects, particularly -winged ants (Bent, U.S. Natl. Mus.
Bull., 176:224-225, 1940). Two nighthawks collected from a migrator>- flock near Roanoke,
\ irginia, on 4 September 1971, contained such an impressive quantity of food material
that I was prompted to make the foUo-VNlng measurements.

The birds, both female, weighed 101.2 g and 99.7 g. and were extremely fat. Their
stomachs -vsere distended -vsith queen ants (Formicinae) , and the wet weights of the

December 1972
Vol. 84, No. 4

GENERAL NOTES

493

contents were 20.5 g and 19.7 g, respectively. This represents 25.4 per cent and 24.6
per cent of the food-free weight of each nighthawk. In comparison, Stevenson (Wilson
Bull., 45:155-167, 1933) found the food in the stomachs of several species of passerine
birds amounted to about 1.5 per cent of their body weight. The wing-loading of the
Roanoke specimens (0.295 and 0.287 g/cm^) is 36.6 per cent and 32.9 per cent greater
than the value given by Poole (Auk, 55:511-517, 1938).

The food was freeze-dried and the caloric content measured in a Parr non-adiabatic
bomb calorimeter. The average of three determinations was 7.434 ± 0.020 kcal/g dry
weight. Total caloric values of the stomach contents were 78.9 kcal and 75.9 kcal, respec-
tively. Using 70 per cent as a conservative estimate of the metabolic efficiency of this
species, 55.2 kcal and 53.1 kcal would be available to the nighthawk from these meals.
This is 3.7 to 3.8 times the daily standard metabolism of the nighthawk as calculated
from the equation given by Lasiewski and Dawson (Condor, 66:477-490, 1964), and the
average temperature of the collection site during September (20.6 C) .

Since the time required for the passage of insect materials through an avian digestive
tract may be as little as 1.5 hours (Stevenson, ibid.), the total calories collected by
individual nighthawks from a generous source such as an ant mating swarm may be quite
large. In the absence of a crop, a large stomach capacity is certainly adaptive in such
feeding situations, although Bent (ibid.) intimates that one nighthawk met accidental
death because of the handicap of carrying a large mass of food material.

I am indebted to C. F. Murray for assistance in collecting the nighthawks. — Charles
R. Blem, Virginia Commonwealth University, Department of Biology, Richmond, Virginia
23220, 10 February 1972.

Retention of egg in a wild Downy Woodpecker. — The observations given below
on egg-binding in a wild Downy Woodpecker {Dendrocopos pubescens) have appeared
worth reporting from three points of view: first, the condition which can be severe or

even lethal under aviary- conditions ( Boosey, E. J., Foreign bird keeping. Iliffe Books, Ltd.,
London, 1970) might be even more so in the wild where the bird would be a helpless
victim to any passing predator. Secondly, if egg-binding is as prevalent in the wild as
in the aviary, it could be a highly important and largely unrecognized mortality factor
among adult breeding birds of many species; and thirdly the present report serves to
document that egg-binding can occur in the wild and is thus not just an artifact of
captivity. The circumstances attending the observations were as follows:

A pair of Downy Woodpeckers had excavated a nest hole in Lyme, New Hampshire
and I had witnessed a total of seven copulations on 6, 7, and 8 May 1971, when at 06:30
on 9 May I noted the female clinging to the bark of a tree not far from the nest stub.
She was in a drooping position as if about to fall asleep. After a few minutes she ascended
to a cavity, the work of a Pileated Woodpecker {Dryocopus pileatus) to rest at the bottom
of it with her bill tucked into her back feathers. Her mate disturbed her a half hour
later but she returned. I could not locate her at 09:15 until the male, coming close to
another cavity, caused her to show herself. She clung to the hark weakly as before. On
my next glance she was clinging with white belly uppermost, then fell fluttering into
swamp water below. Here she made feeble efforts to reach a tree trunk. With head Iield
back and having difficulties in breathing, she would doubtless have drowned had 1 not
picked her up. I took her home, a 10-minute walk, and my wife and I both felt a hard
ovoid mass, the size of a large egg, distentling her abdomen. The woodpecker appeared
to be in spasm and made no efforts to resist. Forty minutes later she was stronger,

494

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

attacking my finger for the first time. Her abdomen was no longer distended. There
was no trace of her having laid an egg and I presumed that she had either laid one and
eaten it or that it had broken inside. I now took her back to the swamp. She was barely
able to flutter to a tree where she remained clinging to the bark without further efforts
to move.

By afternoon a second female 'vnth different head markings (Kilham, Condor, 64:126,
1962) and habits, had arrived by the nest stub. She engaged the attentions of the male
Downy ^^'oodpecker on this and throughout the following day. On 11 May, the original
female re-appeared. She was now in excellent condition and after further copulations she
must have laid at least four eggs, for on 21 June I watched three fledglings fly from the
nest, leaving a fourth one still looking out. — Lawrence Kilham, Department of Micro-
biology, Dartmouth Medical School, Hanover, New Hampshire 03755, 1 March 1972.

The use of sawdust piles by nesting Bank Swallows. — The Bank Swallow {Riparia
riparia) generally digs its burrows in banks of sand, gravel, or clay along inland bodies
of water and marine coastlines. Rarely, it employs such unusual man-made substrates as
drain holes in concrete banks (Hollom, Auk, 60:270-271, 1943) or a pile of iron ore
“tailings” (Van Deusen, Auk, 64:624-625, 1947). Sawdust heaps in abandoned mill yards
are used also as colony sites by the Bank Swallow (Torrey, Auk, 20:436-437, 1903;
Barrows, Michigan Bird Life, 1912; Norton, Bird-Lore, 29:117, 1927; Brew^ster in Griscom,
Bull. Mus. Comp. Zool., 66:554, 1938; and Palmer and Taber, Auk, 63:299-314, 1946).

The colonies in sawdust heaps reported by the above authors occur in northern lumbering
regions from Michigan to Maine. These occurrences, together with additional ones dis-
covered by the present author in Maine and northern New York, suggest that the use of
this substrate in the north may not be altogether unusual. Few^ of the above authors
proHded much more than a simple notice of the location of such a colony.

In this paper, I present information on two colonies of Bank Swallows in old sawdust
piles along the Aroostook River near Ashland, Aroostook County, Maine. Both colonies
t about 600 m apart) were discovered in 1962 shortly after the mill sites were abandoned.
To my knowledge, there had not been any colonies in the immediate area before 1962,
apparently because of the absence of suitable natural or man-made banks. Both colonies
were still active in 1970 when one of them was bulldozed out of existence. In the late
1960‘s swallows established a few burrows in narrow veins of sand in a new gravel pit
nearby.

Burrows in the sawdust piles. — Repeated visits to the colonies from 1962 to 1970 revealed
that slumping, erosion, and perhaps human disturbance changed the total amount of
bank surface available to the Bank Swallows as burrow sites from one year to the next.
The size of the colonies varied accordingly from ca. 50 to 100 active burrows in each
sawdust heap.

Some swallows apparently faced local slumping problems on the steep banks as they
dug fresh burrows into the compact, weathered sawdust (Fig. 1). Partly excavated burrows
Asdth severe slumping around their entrance, forming large, irregular depressed areas in
the side of the bank, were abandoned. Other burrows with only slightly or moderately
enlarged entrances contained active nests. The entrances to still other burrows, especially
those near the rim of the banks, retained a compact, elliptical shape. Norton (op. cit.) and
Brewster <op. cit.) also reported compact, horizontally elliptical entrances to burrows in
other sawdust piles in Maine.

December 1972
Vol. 84, No. 4

GENERAL NOTES

495

Fig. 1. Bank Swallow colony in an old bank of sawdust at Ashland, Maine. See the
text for comments. Photograph by Stanley H. Greenlaw.

The problems of slumping and wearing of the sawdust around the entranees to burrows
is in part a function of age of the burrow and perhaps age of the bank (time since
formed) as well. Entrances to active burrows whieh were compact early in the breeding
cycle, often showed wear and sometimes moderate slumping later in the cyele. Also, most
entrances in freshly formed vertical banks were compact but those in older banks ( sueh
as in Fig. 1) were more often enlarged and irregular in shape.

In old banks of sawdust, erosion and local slumping created variation in the angle of
exposure of adjacent “faces” (Fig. 1). Some of the tunnels in one face converged and
joined tunnels in an adjacent face situated at an oblique angle to the first. Thus an
active burrow sometimes had two entrances. Other tunnels passed from one face to an
adjacent one and were open at both ends. This was not a problem in the smooth, newly
formed banks.

Burrows in low sawdust banks 1.5 to 3 rn high were placed at all heights from top to
the bottom. But in two apparently freshly formed banks 6 to 8 m high, one sparsely
and the other moderately occupied by burrows, the burrows were concentrated near the
rim. The texture and compactness of the saw'dust in all faces seemed to vary little from
top to bottom. Evidently there is a behavioral tendency for Bank Swallow's to dig their
burrows as high as bank conditions permit. Burrows excavated early tend to be situated
high on the bank and those dug later perforce must be lower as the higher sites are
occupied (cf. Peterson, Wilson Bull., 67:246, 1955).

Tunnel orientation relative to the horizontal was variable. Some tunnels slanted upward
then leveled off at the nest. Other tunnels dipped downwards to the nest or were
horizontal. A few even slanted upwards then downwards. Such variability in tunnel

496

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

orientation, though perhaps not this extreme, has been noted in natural substrates else-
where (Stoner, Roosevelt Wild Life Annals, 4:126-233, 1936; Beyer, Wilson Bull., 50:
122-137, 1938).

The length of completed burrows in the sawdust piles also varied, usually from 47 to
60 cm (ca. 18-24 inches). A few were up to 120 cm in depth. Thus, burrow depths in
the sawdust banks correspond in general to depths recorded for burrows in easily excavated
natural substrates such as sand (Stoner, op. cit.; Gross in Bent, U.S. Natl. Mus. Bull.,
179:405, 1942).

Importance of sawdust as a nesting substrate. — Forbush (Birds of Massachusetts and
other New England States, Part III, p. 160, 1929) and Gross ( /n Bent, op. cit. :404)
speculated that sawdust is likely to be an unsuitable if not precarious nesting substrate
for Bank Swallows because of the problems of erosion and slumping. Contrary to this
view, I am unable to conclude that the erosion and slumping faced by Bank Swallows in
sawdust heaps within a given breeding season are substantially more severe or prevalent
than in certain natural substrates, especially in sand banks exposed to wave and current
action, and spring flooding, along streams (cf. Stoner, op. cit.; Beyer, op. cit.). The large
size of the colonies in the sawdust piles at Ashland (among the largest in northeastern
Maine [unpubl. data]) suggests that over-all nesting was fairly successful. Burrows
destroyed in the sawdust heaps are probably replaced by re-nesting attempts (Stoner, op.
cit.) .

The biggest disadvantage of the sawdust pile as a nesting substrate is its relatively short
life. The old piles slowly wear down or are mined by local residents. Otherwise, within
the short term, old sawdust heaps seem to offer both a suitable and perhaps an important
local substrate for nesting Bank Swallows. Holes are readily dug in the compact sawdust.
And the problems of slumping, wear, erosion, and even total bank destruction in natural
substrates probably have provided important sources of selection in the evolution of
ground-burrowing behavior in this species.

I gratefully acknowledge the help of S. H. Greenlaw, B. A. Greenlaw’, and I. Currie
in obtaining information on the colonies at Ashland. — Jon S. Greenlaw, Biology Depart-
ment, C. Post College, Greenvale, New York 11548, 12 April 1972.

Additional vertebrate prey of the Loggerhead Shrike. — On 4 April 1970 Casto
and Dr. R. W. Strandtmann observed an adult Loggerhead Shrike (Lanius ludovicianus)
flying 20 to 30 feet above the ground carrying a snake in its bill. The pair startled the
bird which immediately dropped the dead reptile and flew on to alight on a nearby wire.
The snake, a desert massasauga rattlesnake iSistrurus catenatus) measured 0.41 m in
total length. After preservation in formalin for over a year, the snake weighed 33 g
(probably less than the living weight due to tissue dehydration by the preservative).
This would represent a considerable burden for a bird that weighs a maximum of 49 g
(Miller, Univ. Calif. Publ. Zook, 38:11-242, 1931). The ability of Loggerhead Shrikes
to fly while carrying hea4'>" prey has also been documented by Vaiden {In Bent, U.S. Natl.
Mus. Bull., 197:142, 1950).

Later examination of the snake demonstrated a puncture wound in the neck and damage
to the region behind the postocular scales. Thielcke (Z. Tierpsychol., 13:272-277, 1956)
noted that the Northern Shrike {Lanius excubitor) always kills its prey with a bite, or
series of bites behind the head. The Loggerhead Shrike also punctures prey in the neck
region by striking the prey repeatedly with the point of the bill (Wemmer, Z. Tier-
psychol., 26:208-224, 1970).

December 1972
Vol. 84, No. 4

GENERAL NOTES

497

The incident reported herein represents apparently the only record of a shrike killing
a poisonous reptile of any species. The snake, collected two miles west of Milnesand,
Roosevelt County, New Mexico is deposited in the Herpetology Collection (Specimen
5401), The Museum, Texas Tech University.

A pair of Loggerhead Shrikes removed three Merriam’s pocket mice {Perognathus
merriami) , a green treefrog {Hyla cinera) , and a spring peeper {H. crucifer) from a
study area one mile south of Riviera, Kleberg County, Texas in August 1966. Pocket
mice are nocturnal but are occasionally taken by diurnal predators at dawn or dusk
(Beal and McAtee, U.S. Dept. Agr. Farmers’ Bull., 506:1-35, 1912). Although Northern
Shrikes have captured a similar sized pocket mouse, P. parvus (Scheffer, U.S. Dept. Agr.
Tech. Bull., 608:1-15, 1938), this is the first record of pocket mice being taken by
Loggerhead Shrikes.

The frogs were impaled on a barbed wire fence near a stock tank. Desiccation lessened
the food value of the frogs within 2 days, but the shrikes visited and pecked the mummified
carcasses for eight months. It is not known how long that shrikes will visit impaled
prey (Bent, loc. cit.). Hyla has been previously reported in the diet of L. ludovicianus
but the species was not identified (Miller, 1931).

The observations at Riviera, Texas were made while the senior author was supported by
a National Science Foundation grant GY 369 administered by Dr. R. L. Packard, Texas
Tech University. — Brian R. Chapman and Stanley D. Casto, Department of Biology,
Texas Tech University, Lubbock, Texas 79409, 13 March 1972.

Cowbird parasitism of Western Kingbird and Baltimore Oriole nests. — On 9

June 1971, in a farm woodlot in York County, Nebraska, I examined a Western Kingbird
[Tyrannus verticalis) nest that contained three kingbird eggs and one Brown-headed
Cowbird (Molothrus ater) egg. The nest was in a Siberian elm {Ulmus pumila) approxi-
mately 20 feet above ground. The eggs were being incubated.

Subsequent examinations at two day intervals indicated that all of the eggs hatched
on approximately 18 June. Examination of the nest was conducted at irregular intervals
after 19 June. However, I observed feeding of the young daily until 1 July when the nest
was empty. Throughout the entire period the ground in the vicinity below the nest was
searched daily. On 19 June a few bits of kingbird egg shell were found. A dead young
kingbird was found on 23 June and another on 26 June. It appears that the cowbird
and one kingbird were fledged from the nest.

Cowbird parasitism of Western Kingbirds appears to be rare. Friedmann (U.S. Natl.
Mus. Bull., 233:49-50, 1963) notes one other instance of its occurrence and that one
without precise data.

On 20 June at the same location, I observed a female Baltimore Oriole {Icterus galbula)
enter her nest which was approximately 25 feet from the ground in a Siberian elm. I was
standing a short distance away from immediately under the nest. My attention was
directed elsewhere until 1 heard a soft “plop ” on the ground under the nest. Examination
showed the source of the noise to be a fresh cowbird egg that was broken. The female
oriole was then observed on a twig next to the nest preening. It appears that the oriole
removed the cowbird egg from the nest. This might explain the lack of records of
cowbird parasitism of Baltimore Orioles as Friedmann (op. cit.:133) suggests. — Thomas
S. Smith, Department of Natural Resources, Nelson Hall, University of Wisconsin, Stevens
Point, Wisconsin 54481, 26 March 1972.

498

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Observations of birds at Cecropia trees in Puerto Rico. — The fruits of Cecropia
trees are a favored food of many tropical birds ( Eisenmann, Auk, 78:636-637, 1961),
and in fact the seeds of these fruits show an enhanced viability after passing through
the alimentar>- canal of birds (Olson and Blum. EcologN', 49:565-566, 1968). Obser-
vations on the avian exploitation of Cecropia have been conducted throughout second-
growth areas of Central and South America, but there have been no studies from the
\^’est Indies. In this note I summarize sightings at Cecropia trees in Puerto Rico to com-
pare with my work at mainland trees and to add another perspective of the impact of
North American migrants in the Caribbean.

ObseiA'ations were made in January- (17-27) 1970, and January (15-26) 1971, in
eastern Puerto Rico at Luquillo National Forest. The ecology of this wet montane area,
with almost 200 inches of rain annually, has been extensively reviewed by Odum (A
tropical rain forest, 1970). I worked between 2,300 feet elevation near the base of El
Yunque to 1,500 feet elevation at the La Mina Visitor’s Center. Large Cecropia peltata
trees were common along cleared areas in the forest, and many indi\4duals were fruiting
in both years. A 1971 census in the study area showed 45 in flower, 27 fruiting, and six
non-reproducing.

Species account of birds at Cecropia trees. — An asterisk is used to identify species
actually seen feeding on Cecropia fruits.

* Canary-winged Parakeet iBrotogeris versicolorus) . — This parakeet is an escaped
species that is becoming established in the lowlands of Puerto Rico, and recently (1971)
expanding in Luquillo Forest. It was relatively tame while feeding on fruits.

Puerto Rican Parrot (Amazona vittata) . — This endangered endemic regularly perched
in Cecropia trees, but was never actually observed feeding.

Puerto Rican Lizard Cuckoo (Saurothera vieilloti). — A few individuals fed on large
insects on the branches. They probably take the common tree lizards (Anolis sp.) as
well.

Puerto Rican Emerald (Chlorostilbon maugaeus) . — Several took insects from the
underside of leaves.

* Puerto Rican Woodpecker iMelanerpes portoricensis ) . — \*i'oodpeckers fed on fruits,
and would sunbathe on the exposed limbs ( this is the first report of sunbathing in a
tropical woodpecker — Kennedy, Brit. Birds, 62:249-258, 1969).

* Pearly-eyed Thrasher (Margarops fuscatus) . — Thrashers regularly took fruits and
sang from Cecropia.

* Red-legged Thrushes {Mimocichia plumbea) . — The crepuscular thrushes were infre-
quently obseixed feeding at the fruits.

* Bananaquit iCoereba flaveola). — Bananaquits were abundant at Cecropia and fre-
quently fed on fruit and insects.

Black-and-white Warbler (Mniotilta varia) . — This species was an infrequent insect
feeder at the trees.

* Parula Warbler iParula americana). — The Parula was common at Cecropia where
it fed on fruit and insects.

* Cape May Warbler {Dendroica tigrina). — This species was also common and fed
on both fruit and insects at the trees. One individual was permanently territorial at a
Cecropia where it would supplant and chase Bananaquits and Black-throated Blue War-
blers iaicay from this tree the Cape May "W arbler was subordinate to the Bananaquit
and of equal dominance with the other warbler) .

* Black-throated Blue Warbler (Dendroica caerulescens) . — This species was an un-
common fruit feeder at Cecropia, and scarce throughout the forest.

December 1972
Vol. 84, No. 4

GENERAL NOTES

499

* Chestnut-sided Warbler {Dendroica pensylvanica) . — This rare migrant regularly fed
at the catkin fruits. The species has not been previously reported from the Luquillo
Forest (Bond, Fifteenth supplement to the check-list of birds of the West Indies, 1956).

* American Redstart (Setophaga ruticilla) . — The redstart was generally an uncom-
mon fruit feeder at Cecropia.

Blue-hooded Euphonia (Euphonia musica) . — Euphonias were regular about Cecropia
but I have no definite feeding records. However it is quite probable that they take the
fruits like other euphonias in Central America (e.g. E. fulvicrissa) .

* Stripe-headed Tanager {Spindalis zena) . — This tanager uses Cecropia for exposed
song perches and eats quantities of fruit.

* Puerto Rican Tanager (Neospingus speculiferus) . — This endemic arrives at the trees
in small flocks to feed on fruits.

* Puerto Rican Bullfinch (Loxigilla portoricensis) . — The bullfinch only feed infre-
quently at the fruits.

* Black-faced Grassquit {Tiaris bicolor). — Grassquits rarely fed on fruits, at short
trees near clearings.

Diet Summary. — Of the 20 species of birds utilizing Cecropia at Luquillo Forest, 14
definitely came for fruit feeding. Three of these frugivores and three additional species
were recorded taking insects from the trees. Similar avian exploitation is noted in
Central America. At Barro Colorado Island in the Canal Zone I recorded 41 species
at Cecropia (13 taking fruits, four insectivores, and 24 incidental visitors), over several
months (Leek, The seasonal ecology of fruit and nectar eating birds in lower Middle
America, Unpubl. Ph.D. thesis, Cornell, 1970) . At Cecropia trees in Costa Rica, H.
Hespenheide (in litt.) and others recorded 21 species of frugivores, one insectivore, and
four visitor species.

Birds exploiting the Puerto Rican Cecropia included almost all of the common species
in Luquillo Forest, while the trees in Central America were visited by only a small
part of the total local avifauna. This difference reflects the large number of rare species
on the mainland and the more specialized feeding niches of mainland birds, with many
species strictly limited to non-fruit diets (e.g. antbirds) .

North American Migrants. — Six of the 20 species recorded at Luquillo trees were
North American migrants. This is a considerably higher migrant percentage (30 per
cent) than noted at the trees in Panama (22 per cent) or in Costa Rica (15 per cent).
Such a shift in the proportion of migrants is predictable from a comparison of selected
avifaunal lists from the neotropics — the percentage of an area’s avifauna that is non-
resident dramatically increases in insular situations and with decreasing island size. Per-
centages of non-residents from sample areas will demonstrate this gradient: Mexico 22
per cent. Canal Zone 26 per cent, Hispaniola 41 per cent, Puerto Rico 44 per cent,
Jamaica 48 per cent, St. Croix 48 per cent and San Andres 80 per cent. This change
in the percentage of migrants is of course produced by a rapid decline in the number
of resident species in insular situations, while there are relatively similar numbers of
migrant species throughout. Of considerable interest then is an evaluation of the impact
of the migrants at food resources in the West Indies — are they a more important com-
petitive element on islands than on the mainland? I made a comparison of migrant vs.
resident exploitation by recording all feeding visits to Cecropia in six hours (Table 1).
The migrants were responsible for more than 60 per cent of both the insect and the fruit-
feeding visits. At fruit trees in Panama migrants accounted for only about 10 per cent
of the feeding visits in the lowland and up to 46 per cent in the highlands (Leek, Auk,
89:842-850, 1972). Thus, in Puerto Rico the migrants, again associated with higher eleva-

500

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Comparison of Resident and

Table 1

Migrant Exploitation of
National Forest
(Six hours — January 1971).

Cecropia Trees

IN Luquillo

Insect-feeding

Fruit-feeding

Visits

Visits

Residents

Canary-winged Parakeet

2

(9%)

Puerto Rican Emerald

1

(6%)

Puerto Rican Woodpecker

1

(5%)

Bananaquit

5

(30%)

3

(13%)

Puerto Rican Tanager

1

(5%)

Puerto Rican Bullfinch

1

(5%)

Resident Subtotals

6

(36%)

8

(37%)

M igrants

Parula Warbler

4

(23%)

4

(18%)

Cape May Warbler

7

(41%)

7

(31%)

Black-throated Blue Warbler

1

(5%)

Chestnut-sided Warbler

2

(9%)

Migrant Subtotals

11

(64%)

14

(63%)

lions, are obviously of greater impact than on the mainland. Over 10 years ago Bond
{In: The warblers of America, 1957) suspected the competitive importance of migrant
warblers in the Greater Antilles, but almost no field data were available.

Cecropia resources. — In both Central America and the West Indies human activities
have greatly increased Cecropia populations through the disruption of forested areas.
Cecropia rapidly invades such disturbed areas and has thus become ubiquitous in most
of the neotropics. As an “insect-resource” Cecropia are fair on islands, but poor on the
mainland where symbiotic ants constantly remove other insects and epiphytes (Janzen,
Ecology, 50:147-153, 1969). As a fruit-resource Cecropia are important to at least
several hundred bird species in the New World, and they are a significant resource for
many opportunistic migrants.

During both recent visits to Luquillo Forest I enjoyed the kind hospitality of Drs.
Cameron and Kay Kepler, U.S. Forest Service. Their suggestions and added sightings
at Cecropias were most helpful. — Charles F. Leck, Department of Zoology, Rutgers
University, New Brunswick, New Jersey 08903, 7 February 1972.

ORNITHOLOGICAL NEWS

Your attention is directed to the “Preliminary Call for Papers” for the 1973 meeting
appearing on the back cover of this issue. It is absolutely imperative that all applications
for a position on the program be in the hands of the Chairman, Dr. Andrew Berger,
Department of Zoology, University of Hawaii, Honolulu, Hawaii 96822, before 1 March.
Because of Dr. Berger’s location it is essential that all correspondence with him be
carried out by (domestic) air mail.

The final number of another volume is once again the place to show appreciation to
the large number of ornithologists who have aided in the preparation of this volume by
refereeing papers, by offering advice, and in countless other ways. Special thanks are
due to Treasurer William Klamm for his preparation of the Membership List that accom-
panied the September issue, and to Emma J. Messerly and John F. Messerly who prepared
the index to this volume.

LOUIS AGASSIZ FUERTES AND MARGARET MORSE NICE AWARDS

Fuertes Awards are devoted to the encouragement and stimulation of young ornithol-
ogists. One particular desire is the development of research interests among amateur
ornithologists. Any kind of ornithological research may be aided. Recipients of grants
need not be associated with academic organizations. Each proposal is considered primarily
on the basis of possible contribution to ornithological knowledge. Although grantees are
not required to publish their studies in The Wilson Bulletin, it is hoped that they will
submit their manuscripts to the editor of the Bulletin for consideration.

Most of the statements applicable to the Fuertes Awards are also applicable to the Nice
Award. However, the Nice Award is limited to amateurs, i.e., those whose research is not
associated with their livelihood and is not being done in pursuit of an academic degree.

In some years two Fuertes Awards have been made, in some years one. Amounts have
been between $200 and $100. One Nice Award is made annually, in the amount of $100.

Interested persons may write to Val Nolan, Jr., Department of Zoology, Indiana Uni-
versity, Bloomington, Indiana 47401. Completed applications must be received by 15
April 1973. Final decisions will be made by the Council at the annual meeting of the
Society, 17-20 May 1973.

RED CROSSBILLS

Little has been done to implement Griscom’s suggestion (Proc. Boston Soc. Nat. Hist.,
1937) that specimens of Red Crossbill iLoxia curvirostra) be preserved from every major
flight; but a new study of this unpredictable bird emphasizes this necessity. Any material,
including road, net, and window casualties, will be welcome. If whole skins cannot he
saved, the heads alone (with bills closed in their natural form, if possible) will be useful
— especially if sewed, not too tightly, to the same individual’s wing(s) and preferably
tail as well. Even skeletons of birds long dead may be very helpful. Please he sure to
tag each with the standard data: collector; locality (if this is some distance from the
nearest conifers, please so state) ; date; if found dead, an estimate (from the bird's
condition) of how long it had been dead; and its weight, in grams, if fresh.

Kindly submit material for study to the undersigned. It will he returned later, after
identification of the subspecies, if you so reijuest. Shipments from outside the United

501

502

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

States should be marked “Scientific specimens. No commercial value.” Please give your
return address, in all cases.

I would especially prize records of movements of banded crossbills, or measurements
of birds banded, accompanied by a sketch of how the measurements were taken, and
weights. — Allan R. Phillips, Delaware Museum of Natural History, P. 0. Box 3937,
Greenville, Delaware 19807.

Dr. George M. Sutton has been honored by the President of Iceland by the award of
the Knight Cross of the Icelandic Order of the Falcon.

On 21 October 1972 the Cornell Laboratory of Ornithology awarded the sixth Arthur
A. Allen Award to Allan D. Cruickshank.

Hoyes Lloyd is the latest addition to the roster of 50-year members of the Wilson Society.

Members who know students that are interested in ornithology should send nominations
to the Student Membership Committee addressed to Douglas James, Department of
Zoology, University of Arkansas, Fayetteville, Arkansas 72701. The nominees will be
invited by the Committee to apply for membership in the Wilson Ornithological Society.

The Laboratory of Ornithology at Cornell University is offering a college-level course
in ornithology’ to be undertaken at home. In nine seminars the course gives a substantial
background in readable style for the appreciation and enjoyment of birds.

Each seminar has been prepared by one or more eminent ornithologists and profusely
illustrated by well-known bird artists and photographers. The course is offered sequen-
tially, with each seminar mailed to the participant for his study and completion before
progressing to the next one. Upon his completion of the course, the participant will receive
an appropriate certificate.

For further details including the procedures and costs of enrollment, write to the Cornell
Laboratory of Ornithology, 159 Sapsucker Woods Road, Ithaca, New York 14850.

The Frank M. Chapman Memorial Fund gives grants in aid for ornithological research
and also post-doctoral fellowships. Applications are due on 15 September and 15 February.
Information on form and content of applications may be obtained from the Frank M.
Chapman Memorial Fund Committee, The American Museum of Natural History, Central
Park West at 79th Street, New York, N. Y. 10024.

Request for Specimens. The University of California at Santa Barbara conducts a large
scale program in the natural history’ of terrestrial vertebrates. However, our small collec-
tion of specimens severely limits the program. We would like to acquire additional speci-
mens, especially of western North American forms but other forms, even foreign ones,
would be desirable. We would welcome the donation of specimens no matter how small
the collection and could probably use the specimens more valuably than institutions
maintaining large collections. Stephen I. Rothstein, Department of Biological Sciences,
University of California, Santa Barbara, California 93106.

ORNITHOLOGICAL LITERATURE

High Arctic, An Expedition to the Unspoiled North. By George Miksch Sutton. Paul
S. Eriksson, Inc., New York, N.Y. 1971: 11 X 8V2 in., xiv + 119 pp., 11 col. + 17 bl.
and wh. pis., $12.95.

In 1969 Dr. Sutton was invited by S. D. MacDonald and David F. Parmelee to accompany
a Canadian National Museum expedition to the northern Canadian Arctic Archipelago.
This book is the author’s very personal account of his part in that expedition illustrated
by several of his paintings and sketches, and also by black and white photographs con-
tributed hy other members of the party.

The expedition spent most of June on Bathurst Island, and then made a brief tour by
chartered aircraft of Western Ellesmere and Meighen islands in an unsuccessful attempt
to locate nesting Ivory Gulls. Ironically after the long flight searching for them. Ivory
Gulls which proved to be breeding, were observed at Resolute Bay, Cornwallis Island,
while the group was waiting for a commercial airline flight back south.

This was Dr. Sutton’s 15th trip to arctic regions, but his first to the high arctic, and
the experience seems to have inspired him. The eleven color plates in the book include
some of the finest work by Sutton that I have seen. He has used water color with lovely
effect to capture the feel of wet snow, melt water pools, misty fog, and the mood of night-
long twilight, grey skies and sun-saturated fog. The arctic landscape dominates many of
the paintings reducing the animal subjects to focal points on the scene. This approach
conveys the overwhelming impact that the large openness of high arctic landscapes has
on an observer and dramatizes the larger-than-life conspicuousness of any living creature
on the northern tundra barrens. Particularly successful are the three King Eiders flying
under a band of drizzly grey fog, and above the green of wet fresh sea ice; or the four
distant muskoxen casting long shadows across wet snow as they walk; and the seven
Black Brant flying along a valley under a luminous grey sky, below the tops of hills
where bare patches of earth are just beginning to show. These paintings and several others
beautifully capture the feeling of the high arctic tundra in spring and are well worth the
price of the book.

I do have a cavil with one painting, however, even allowing for the artist’s impressionistic
style in these works — the back of a Long-tailed Jaeger is slate gray and not sepia toned.

The text recounts the author’s daily experiences and impressions, as well as his obser-
vations of birds and mammals. Anecdotes about muskoxen, wolves, arctic hare, and
Sanderling are particularly interesting. The style is episodic and reads as if the author
has expanded his field notes for presentation. This approach has the advantage of retain-
ing the author’s immediate impressions hut it has the disadvantage that continuity is poor
and that mood and feeling are not created for the reader. This is an instance where less
matter and more art would have helped.

Some of the scenes are too short and contribute so little that I wonder why they were
included. The account of the Buff-breasted Sandpiper (p. 48-49) is an example. Some
of the author’s conclusions, i.e. that sparring male Rock Ptarmigan partly open their wings
to keep themselves upright (p. 57), are questionable. Another statement, that prostrate
arctic willows possibly live for a century (p. 10) is incorrect.

The format of the book is spacious and well designed. The text is confined to part
of each page and a few small black-and-white sketches and photographs are tastefully
inserted. The photographs are on-the-whole interesting and contribute greatly to the overall
impression of the work.

Despite my criticisms I enjoyed this book, and recommend it to anyone wanting a

503

504

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

sensitive impression of the far north. The paintings are certainly its outstanding feature
and the publisher has, in fact, printed them in a separate portfolio available at $14.95. —
William J. Maher.

Birds of the Antarctic and Subantarctic. By G. E. Watson, J. P. Angle, P. C. Harper,
M. A. Bridge, R. P. Schlatter, W. L. N. Tickell, J. C. Boyd, and M. M. Boyd. Antarctic
Map Folio Series, Folio 14, American Geographical Society, New York, 1971: 11 X

17^/4 in., 15 pis. bearing many maps and photos. $10.00. Obtainable from: American
Geographical Society, Broadway at 156th St., New York City.

This elaborate and useful atlas is a milestone along the road of antarctic and sub-
antarctic ornithology. George E. Watson, of the United States National Museum, and
seven collaborators have explored an enormous oceanic area by personal field observation,
as well as by searching the formidable mass of pertinent scientific literature, dating from
1838 to 1968. The authors cite about 125 references to texts covering the relatively narrow
scope of their interests, and 713 additional books, journals, and manuscript sources of the
data that they record in their tables and charts. An adequately labelled map, keyed to
the list of geographic localities, concludes the text of the introductory section. Then
follow 14 large charts in south polar projection on which the nesting places of fifty or
more taxa of Panantarctic birds are indicated. The final or 15th plate shows photographs
of the birds themselves, pictured at breeding sites or in flight in various parts of the
“Roaring Forties.”

The charts present a clearly organized plan of bird distribution throughout a wide
circumpolar belt. The list of breeding places includes every island and all parts of the
Antarctic Continent for which information is available, and the latter is related by number
to the bibliographic sources. On the charts, moreover, the seas are peppered with symbols
that tell whether the record of a species was established by the collection of a specimen
or rests on an observation. Complicated clusters of islands, such as those that fringe the
Antarctic Peninsula, are commonly enlarged in insert maps near the borders of the
circumpolar charts so that islands and symbols can appear in ampler scale. The score
or more of isolated insular groups throughout the Panantarctic ocean are not named on
the charts, but can readily be identified from the locality map. At any rate, they rapidly
become familiar by position alone to anyone who has an interest in their avifauna.

Dr. Watson is responsible for the ten pages of introductory information that precedes
the charts. This is accompanied by an ingenious table of distribution of the species of
birds and by colored maps of the biotic zones, provinces, and districts that the author
recognizes. Other maps show the great divergence, the inner and outer pack ice, and
the subantarctic and subtropical convergences that divide the successive surfaces of the
ocean between the Antarctic Continent and the surrounding tropical world ocean. The
Continent itself embraces 13 million square kilometers, of which less than five per cent
is free of permanent ice cover. Furthermore, much of the exposed land is too remote
from the sea, the sole source of food, to offer breeding stations for birds which, therefore,
are obliged to nest in favorable coastal areas or on the more or less distant antarctic and
subantarctic islands.

Of the birds included in this study, 7 are penguins, 7 albatrosses, 27 petrels, 2 cor-
morants, 2 skuas, 1 gull, and 3 terns (one of which is the Arctic Tern!). The only
non-webfooted species are the two sheathbills and the pipit of South Georgia, which is
the southernmost native land bird in the world. Watson groups the prions ( Pachyptila)

December 1972
Vol. 84, No. 4

ORNITHOLOGICAL LITERATURE

505

with the gadfly petrels, whereas this reviewer would include them in the fulmarine section
of the Procellariiformes. He errs in inferring that Daption, the name of the far-famed
Cape Pigeon, should be classed as a Greek neuter. On the contrary, it is a nonsense
word, an anagram of the Spanish adjective “pintado,” and the name still stands as
Daption capensis.

Instances of how rapidly knowledge of antarctic birds is being amassed at present show
up occasionally in this publication. The recent (1971) appearance of “Marion and Prince
Edward Islands” (A. A. Balkema, Cape Town), representing an expedition under South
African auspices, is a case in point. In this hefty volume. Professor van Zinderen Bakker,
Jr. reports that the South Georgian diving petrel breeds abundantly on both islands, and
to higher altitudes (700 m) than any other birds there. Again, Ian Strange has recently
reported (Ibis, 110:358, 1968) Pachyptila turtur as a resident of Beauchene Island in the
Falklands, but my examination of Strange’s specimens shows that they represent, in reality,
the first record of a different bird, the fulmar-billed prion {Pachyptila crassirostris) .

Such matters have just barely escaped notice by the authors of this notable atlas, which
summarizes so well the environment of the south polar region and the causes of the varying
geographic influences on the distribution of birds. The authors, in their recognition of
three special faunal “districts” — in the subantarctic Atlantic, the southern Indian Ocean,
and the seas to southward of New Zealand and Australia — are abundantly supported by
evidence from the flora and fauna of many groups other than birds. They have produced
a major study that may be amended in numerous details but is likely to stand for a long
while in its substantive structure. — Robert Cushman Murphy.

Birds of North America. By Austin L. Rand. Doubleday and Co., Inc., New York, 1971:

6% X 9 in., 256 pp., 46 col. photos, 35 bl. and wh. photos, by various photographers.
$9.95.

This is a volume in the “Animal Life of North America” series, planned and produced
by Chanticleer Press. Following an introduction in which the author presents very well
a lot of information in a few succinct sentences on bird anatomy, evolution, migration,
molt, ete., the families of North American birds are taken up one by one, with comments
and short descriptions of the species in each family.

I am unable to ascertain, however, the niche this book is expected to fill. There is little
new for the advanced birder or ornithologist, and it does not seem that it will aid the
beginner in learning family characters, or in identifying birds or learning their habits.
It is interesting reading, and has many personal touches by the author which I found
charming. The section on warblers is handled particularly well. But I found myself
wanting more specific details throughout. Even in species descriptions, or hints for
identification, it often seems that a key character is lacking. In fact the treatment of
species in general is shallow — a reader wanting a little more on breeding habits or descrip-
tion or range than is in the field guides will not find it here. Admittedly this may not
be the purpose of the book, but what is the purpose? It is called a “survey in pictures
and text of 600 birds.”

The color reproduction and quality of the illustrations is very good, with few exceptions.
In my copy, at least, the American Goldfinch on page 240 is fuzzy. I have seen the
original photograph and it is sharp. The Bald Eagle picture is of a captive, rather di-
sheveled bird. This reviewer always objects to having to hunt for the name of a particular
photographer; in this volume all photographic credits are lumped on the last page.

506

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

It seems regrettable that in a book of general interest the author makes little or no
mention of recent well-documented declines in several species, and avoids all mention
of the role played by pesticides and by human interference of various kinds in such
declines. It is implied that the Peregrine Falcon still nests throughout the east, and
“sometimes even nests on the ledges of skyscrapers.” There is no mention of the decline
of the Brown Pelican as a nesting bird in part of its range, and the present sharp decrease
of the Eastern Bluebird is lightly dismissed as being temporary and due to weather and
competition with other hole-nesters — factors which contribute but are not the whole answer.

There are a number of typographical errors, and a few minor errors of fact. “On spring
migration the birds (thrushes) are silent; their songs are reserved for their breeding
grounds." Certainly Gray-cheeked and Swainson’s Thrushes frequently sing in migration.
The Yellow Warbler arrives throughout the northeast in early May, not mid- to late May
as stated by the author. “The Trumpeter Swan differs from the Whistling Swan in having
a black bill. . . .” Both have black bills. On page 10: “within each species range the
bird lives only in certain habitats” while on page 59 mention is made of “the great seasonal
changes in (diets and) habitats made by a great many migrating birds.” Vultures are
listed as using large tree roosts— but certainly in the southwest cliff roosts are more
common. In other parts of the text, insertion of the word “usually” or “generally” would
have made for greater accuracy.

This is an interesting book, an easily-read book, and contains many solid bits of
information and charming personal observations, even if it does not add much to ornitho-
logical information. It will be read and enjoyed, but probably not often used as a reference.
— Sally Hoyt Spofford.

Classification of the Ovenbirds (Flunariidae) . By Charles Vaurie. H. F. and G.

Witherby Ltd., London, 1971: 8% X 5^ in., 46 pp., hard cover. Price not given.

Few bird families are more in need of thorough study, or more difficult for the tax-
onomist, than the ovenbirds, one of the two large families of the New World antbird-
ovenbird assemblage. Members of the Furnariidae fill many niches occupied by oscines
in other parts of the world; as predators on non-flying arthropods, they are variously
convergent on thrushes, warblers, creepers, nuthatches, and titmice. Past revisers, the
most recent of whom were Hellmayr (1927) and Peters (1951), evidently relied on bill
shape and general body plan in subdividing the family, defining genera, and creating a
linear sequence.

Vaurie now provides a new classification, the result of many months of study, involving
thousands of skins. It differs strongly from those of Hellmayr and Peters, especially in
the number of genera. Hellmayr recognized 53 furnariid genera and Peters recognized
58; Vaurie has reduced these to 34. There has been little change in the total number of
species, however, the respective figures being 209, 221, and 218.

The brief (half-page) introduction notes that the classification was written originally
for a few colleagues, and subsequently published in order to make it more widely available
and to establish a base of reference for future work. These remarks are followed im-
mediately by the classification (pp. 9-15) which divides the family into subfamilies,
genera (with some subgenera), and species. The classification is followed by 35 numbered
notes (pp. 16-45) that are apparently intended to explain major changes from previous
classifications and to account for missing species. To some extent, the notes do fulfill
these functions, but many of Vaurie’s mergers and separations must be accepted largely

December 1972
Vol. 84, No. 4

ORNITHOLOGICAL LITERATURE

507

on faith. Note 9 (p. 20), for instance, states in its entirety: ^^Synallaxis azarae and S.
elegantior, which are currently considered to be conspecific, are apparently two separate
polytypic species.” Presumably the data supporting this conclusion are to be presented
in a subsequent paper. (Or have they already been published? The reader is not told.)
Two species seem to have vanished without a trace. One of these, Xenoctistes mirandae
Snethlage, 1928 (placed in Syndactyla by Peters) is probably considered by Vaurie to be
a form of Philydor dimidiatus, following Hellmayr (in Meise, Proc. Eighth Internatl.
Ornithol. Congr. : 150, 1934) ; the other, Cranioleuca baroni Salvin, 1895, has probably been
lumped into Certhiaxis albicapilla, if Vaurie agrees with the footnote in Hellmayr (1927, p.
117). This agreement is no means certain, for there are many other instances in which
Vaurie disagrees with Hellmayr and/or Peters on the affinities of species. The genera
Cranioleuca and Certhiaxis are not considered separable, and the author devotes nearly
four pages to a discussion of nesting behavior, pigmentation (the presence of yellow), and
number of rectrices, the characters which he feels unite the 19 species.

In reading this work, one cannot avoid the feeling that there must be more to come,
that what is left unsaid will be covered in an in-depth review of the family. I have no
doubt that this will be the case. In the meantime, evaluation of many of Vaurie’s taxonomic
conclusions will probably be withheld until they are supported by data and by a discussion
of taxonomic characters for this group. One can only guess what Vaurie considers to be
good taxonomic characters at the generic and specific levels. He states emphatically that
bill shape is of no use, and that the number of rectrices cannot be used to define genera
but may be useful in separating species. Although he does not say so directly, Vaurie
clearly considers that nest type (sometimes restricted to details of construction) is a good
generic character in ovenbirds. Unfortunately, the nests of only a fraction of the species
have been described in detail.

It is regrettable that this short, but important work, which must rank as one of the
slimmest hard-cover “books” on the ornithological shelf, was not published in a journal or
museum bulletin. With only 250 copies printed, it will hardly attain the wide availability
that it deserves. We can only hope that it will soon be followed by a more detailed
treatment, in which we are provided greater insight into the author’s research on this
diverse family. — Peter L. Ames.

Birds of the African Rain Forests. Sounds of Nature No. 9. Two 33% rpm records.
Recorded by Stuart Keith. Produced by S. Keith and William W. H. Gunn. Federation
of Ontario Naturalists (1262 Don Mills Rd., Ontario, Canada) and the American
Museum of Natural History. $12.75.

Guaranteed to instill nostalgia in ornithologists who have worked in Africa’s great
forests, this well-produced pair of records provides a splendid supplement to earlier discs
on African birds. Tliis set is perhaps the most useful of those available; it is limited to
a single habitat, one in which bird voices are particularly important in field identification.
Additionally, these records stress the passerines and certain small non-passerines which
are most numerous and which provide most of the voice recognition problems.

A much appreciated feature is the absence of superfluous narration. There are no spoken
words except for the announcement by Mr. Keith of each bird’s Englisli name (following
Mackworth-Praed and Grant). Introduction and comments are properly confined to the
jacket, allowing maximum record space for the recordings.

The jacket itself, attractively decorated l)y a photograph of a Cinnamon-chested Bee-eater

508

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

by C. Hilary Fry, consists of five sides of “text” (marred only by two or three typographical
errors) , There is also a map depicting the numerous forest areas given, along with dates
of each cut, in the notes pertaining to every recording. Identification of significant back-
ground sounds is universal. Comment is brief and informal but interesting and instructive,
often drawing attention to such things as possible taxonomic implications of the vocaliza-
tions. The records cover 92 bird species, plus 20 more distinguished in the backgrounds
of these. Another, not identified, is the Uganda Woodland Warbler {Seicercus budon-
goensis) which gives one readily recognizable song in the Joyful Greenbul recording. Of
the main 92 species, eight are duplicated on Myles North’s and Donald McChesney’s
“More Voices of African Birds” records. Some listeners might criticize this overlap but
the species involved are typical sylvan birds whose absence from a forest bird production
would be inappropriate. (Together with the two Cornell University Laboratory of
Ornithology African albums, the present set brings the total of African bird songs
available on American records to about 237 species.)

Anyone who has spent time learning tropical forest bird voices will appreciate the effort
and time that went into the recordings. Hearing the wierd moan of the Buff-spotted
Crake (Sarothrura elegans) recalled my first stay in Kenya’s Kakamega Forest where
this perplexing sound defied identification for so many evenings — as did the song of the
Honeyguide Greenbul ( Baeopogon indicator) which issued from the canopy for days before
I could trace it to its author. It is great to have available vocalizations of these and of
such rarities as the Green Ibis (Bostrychia olivacea) and Green-breasted Pitta {Pitta
reichenowi) .

Of taxonomic interest are the recordings of the coastal and interior forms of Nicator.
I share Keith’s opinion that these two are not conspecific. The voice of Macrosphenus
kretschmeri — identified from Keith’s tapes by the late R. E. Moreau — does indeed suggest
that this Longbill is not a pycnonotid. Those who have never heard Archer’s Robin-chat
will be surprised at the great difference between its voice and that of other Cossypha
species. A major contribution is presentation of vocalizations from 12 species of greenbuls
( Pycnonotidae) . Of particular value are the songs of three shy forest babblers: Mala-
cocincla fulvescens, M. albipectus, and M. pyrrhoptera. Unfortunately, no recording of
.1/. rufipennis is available. In places this bird is sympatric with fulvescens and albipectus
and apparently no one has yet been able to distinguish its song from that of the latter.
Both are almost equally numerous in the Kakamega Forest where these recordings were
made.

Technically the records certainly are up to modern standards. Nearly all of the indi-
vidual recordings are ver\’ good. Only one (Charinda Apalis) do I consider to be of
inferior quality and it is not bad. There is considerable background sound but as Keith
states, this adds more “flavor” to records of this type. An African forest should not sound
like a recording studio. It is often a noisy place and a visitor’s auditory impressions are
more vivid than his visual ones. I would enjoy these songs and calls much less if the
extraneous sounds had been filtered out.

Along with the decided utilitarian value of these records is considerable aesthetic appeal.
Several of the bird species presented here possess exceptional voices — among them the
Mountain Yellow Warbler ( Chloropeta similis) , Wattle-eye Flycatcher (Platysteira
cyanea) and certain of the thrushes. The African Wood Owl recording is, to me, pure
auditory delight. Almost all of the vocalizations are pleasing as well as educational. The
final band of the second disc reveals a few impressive mammalian voices. Some purists
may object to these occupying space that could have been devoted to another four or five
birds, but I, at least, have always considered the calls of black-and-white colobus monkeys

December 1972
Vol. 84, No. 4

ORNITHOLOGICAL LITERATURE

509

and wild chimpanzees to be among Africa’s most thrilling sounds; I was delighted to
find these on the records. Furthermore, the visitor to an African forest surely will want
to know what animals are responsible for such noises. (The peculiar bird-like chirping
of the copper-tailed monkey, Cercopithecus nictitans, would have made an interesting
inclusion along with the calls of the other primates.)

Messrs. Keith and Gunn have produced a pair of high quality records which I hope
will be the forerunner of more to come. Perhaps eventually we can expect positively
identified recordings of all the forest greenbul species, or some of the other “problem”
groups. The African forests hold much promise for continued work of this sort.— Dale A.
Zimmerman.

The Ways of Wildfowl. Reproductions of Etchings and Paintings by Richard E.

Bishop. Text by Russ Williams. Edited by Thomas C. Jones. J. G. Ferguson Publishing
Co., Chicago, 1971: 1014 X 1314 in., 260 pp., 38 etchings and 64 col. paintings by

Bishop, more than 50 marginal sketches by Bob Hines. $24.95.

For many years Bishop paintings have appeared on calendars — each a mixture of marshes
or woodlands in fall colors and close-ups of waterfowl, pheasants, and other gamebirds
in dramatic action. “Prairie Wings,” published in 1947, included many Bishop sketches
interpreting flight of ducks, a major contribution from joint studies by author Qweeny
and artist Bishop. Their “action shots” revealed many details of flight that are too com-
plicated for the human eye to catch. In his paintings. Bishop has tried to show birds
in motion, in take-off and in landing — and be bas been fairly successful.

Readers of this book will enjoy many of the color plates, although it is a pity that
cropping has left partial birds in some of the pictures. To me, among the most accurate
and pleasing paintings are those of Mallards on pages 129 and 136, and those of Pintails
on pages 135, 157, and 158. Numerous other pictures, however, show poor action and
proportion, as in the Wood Duck hen on page 132, with its too-small tail feathers and
most unnatural bend of the body. A similar distortion appears in the four nearest Pintails
on page 153. Bishop’s upland gamebirds also tend to have too-heavy shoulders. It is
unforgivable to label a drake Gadwall as a “Redhead” (p. 48), even though this particular
painting is far from good of the Gadwall.

The etchings vary greatly in quality and interest; some have suffered, I suspect, from
cropping to fit the page, while offering large images.

Usually the text supports the pictures in a publication of this sort, but alas there is
not a word to explain the flight action nor to identify the earlier works from more recent
ones. Thus, in fairness to the artist, I venture to say that this collection does not represent
the best of his paintings; I doubt that it can be taken as a gallery showing.

A word as to the marginal sketches by Bob Hines: some are fair but many are poor
renderings. On page 59, a pair of Ring-necked Ducks are shown with far too skinny necks
and a misleading white wingpatch. In the mergansers on page 89, the female has the
head and neck pattern of a Common Merganser instead of a Red-lireasted. Also, it is
confusing to use unlabelled sketches of Mallards alongside text about eiders on pages
82 and 89.

In the introduction, Mr. Williams states that his contribution is “not a scientific work
or textbook.” He has given popular accounts of the species of waterfowl and certain
upland game and marsh species, and to a degree has discussed their “ways.” But for
his stories he has drawn heavily, and at times not too critically, on other authors. Accounts

510

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

of species, flyways, etc. were so well presented in “Waterfowl Tomorrow” (U.S. Dept,
of Interior, 1964) that an abstract such as this is far less useful. Also, I regret the
repetition of numerous myths or assumptions now disproved by competent biologists, such
as that “all swans mate for life” or that “when pitching into the water, swans do not
usually extend their feet in front as the geese and ducks do. With feet retracted, they
glide easily into the water with a belly landing — so gracefully and lightly they barely
make a splash.” Loons, grebes, and at times of exercise or play, all waterfowl may “skip”
on the water, but as a rule swans “skate” on the surface when alighting.

The chapter on attracting upland game and waterfowl greatly oversimplifies this subject.
The author forgets aesthetics and beauty in nature when he suggests artificial structures
such as “old tractor tires, washtubs, oil drums” to improve nesting conditions! It is
especially regrettable that the text fails to explain Bishop’s contributions to the under-
standing of bird flight. Nevertheless all of us can sharpen our knowledge of wildfowl
if we really study both text and illustrations. — Miles D. Pirnie.

The Forests and Wetlands of New York City. By Elizabeth Barlow. Little, Brown

& Co., Boston, 1971: X 10 in., xxiv 160 pp., maps, many photos. S8.95.

This book purports to discuss the woodlands and marshy areas of the great metropolis.
Although there are chapters on Staten Island, the Jamaica Bay Refuge, and Pelham Bay
and Inwood Hill parks, nothing is said about Bronx or Van Cortlandt parks in the Bronx,
nor about Alley Pond or Forest parks in Queens. These last four are most certainly well
worth treating in detail, and their omission is serious, indeed.

On the other hand, we are given the bizarre histor>' of the lunatic asylum and its
inmates on what was once known as Blackwell’s Island, now called Welfare Island.
Whatever this has to do with “Forests and Wetlands” completely escapes this reviewer.
Nor can I visualize the chapter on “The Foundations” — a history of the geological forma-
tions of New York City — as having any connection with either the swamps or sylvan
tracts of the five boroughs, except in a ver>' indirect way.

The opening chapter, “The Green Breast,” is a rambling, historical account of Man-
hattan Island, chiefly in the Dutch colonial period, and does manage to touch lightly on
its green belt of former times. The portions on the four forest and wetland locations are
informative and well written, if somewhat chatty.

Many of the black-and-white photographs are good to excellent. Tlie a\id birder will
recognize the names of Howard Cleaves and Arthur Swoger as well-known wildlife
photographers. The maps are adequate, if not outstanding. Altogether, this reHewer
found the book light, entertaining reading, but a great disappointment by reason of its
incompleteness. — John Bltll.

A Manual of Wildlife Conservation. Edited by Richard D. Teague. The Wildlife
Society, Suite S-176, 3900 Wisconsin Ave., N.W., Washington, D.C., 1971: 8y> X U
in., X + 206 pp.. photos, many drawings by Erancis L. Jaques, Ralph Oberg, and
Charles W. Schwartz. $5.50.

This is the text of a “Short Course in Game and Eish Management” conducted annually
since 1965 at the Colorado State University. As a reviewer, I can happily present an
accolade to the editor, to the Wildlife Conservation Manual Committee, chaired by Dwight
R. Smith, and to The Wildlife Society.

December 1972
Vol. 84, No. 4

ORNITHOLOGICAL LITERATURE

511

There has always been a gap between scientists and administrators in our natural
resources society. Lack of understanding and lack of appreciation of the one for the
other is the rule, and is responsible in part for our dying environment.

This book is a series of about 50 brief articles directed to the administrator, and
designed to provide him with the essentials of policy, state and federal objectives, sociology
and public values, wildlife and fisheries management techniques, wildlife law, and re-
search. It is an administrator’s handbook, but it is a fine adjunct to any course in
wildlife management.

There has not been a wiser book on conservation published in the last quarter century.
— Oliver H. Hewitt.

PUBLICATION NOTES AND NOTICES

Annual Bird Report for Southern Vancouver Island, 1970. Prepared by the Ornitho-
logical Records Committee for Southern Vancouver Island, edited by J. B. Tatum.
Victoria Natural History Society, Victoria, B.C., Canada, no date: X 8% in.,

paperbound, 72 pp., photos, sketches, and map. $ 1.90. Order from Dr. J. B. Tatum,
416-3187 Shelbourne Street, Victoria, B.C., Canada.

An annotated summary of the records of 235 species seen during 1970 in southeastern
Vancouver Island and the adjacent Gulf Islands. The records have been scrutinized by
a local experienced committee. Hopefully future reports will be more concise. — P. S.

Birds of Moose Mountain, Saskatchewan. By Robert W. Nero and M. Ross Lein.
Special Publication No. 7, Saskatchewan Natural History Society, Regina, Sask., 1971:
5V2 X in., 55 pp., 8 photos, 2 maps, paperbound. $2.00. Order from Saskatchewan
Natural History Society, Box 1121, Regina, Sask., Canada.

Moose Mountain is situated in extreme southeastern Saskatchewan. Its avifauna — 173
known species — consists of species characteristic of grassland, deciduous forest-edge,
deciduous forest, and boreal forest. This well-prepared booklet presents a description of
the area, a brief discussion of the avifauna, and species accounts. — P. S.

Catalog of Bird Specimens Southwestern Museum of Natural History. By David
M. Niles. New Mexico Ornithological Society, 1963: 6 x 9 in., 36 pp., paperbound.
Revised supplement published in mimeographed form, 1968: 8% X H in., 33 pp.

Bird-Finding Localities in Southwestern New Mexico and Southeastern Arizona.
By Dale A. Zimmerman. New Mexico Ornithological Society, 1966: 6 x 9 in., 12 pp.,
3 maps by Bruce J. Hayward and Mary Huey, paperbound.

Bird-Finding Localities in the Vicinity of Roswell, New Mexico. By Vester A.
Montgomery. New Mexico Ornithological Society, 1969: 6 X 9 in., 10 pp., 2 maps
by Mary Huey, paperbound.

These publications are available (price not given) from the New Mexico Ornithological
Society, P.O. Box 277, Cedar Crest, New Mexico 87008. — P. S.

512

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Annual Review of Ecology and Systematics. Volume 2. Edited by Richard F. John-
ston, Peter W. Frank, and Charles D. Michener, Annual Reviews Inc., Palo Alto, Calif.,
1971: 6% X 9 in., ix + 510 pp. $10.00.

The limits of ecology and systematics spread widely as interpreted by the editors of
this volume. Papers deal with economics and human evolution as well as many subjects
in the natural sciences. Douglass H. Morse presents a theoretical discussion of The
Insectivorous Bird as an Adaptive Strategy and Daniel H. Janzen reviews Seed Predation
by Animals. — P.S.

Bird Study. By Andrew J. Berger. Dover Publications, New York, 1971: 5Y2 X in.,
xi -f 389 pp., many drawings and photographs, paperbound. $3.95.

An unabridged republication of the work first published in 1961 and reviewed in The
Wilson Bulletin, 75:222, 1963.— P. S.

Birds of Maricopa County, Arizona. Annotated Field List. Compiled by Salome R.
Demaree, Eleanor L. Radke, and Janet L. Witzeman. Maricopa Audubon Society (4619
East Arcadia Lane, Phoenix, Arizona 85018), 1972: 5 x 8 in., 64 pp., one map. $2.95
-f- $0.25 postage and handling.

A Field List of the Birds of the Delaware Valley Region. By Alan Brady, W. Ronald
Logan, John C. Miller, George B. Reynard, and Robert H. Sehl. Delaware Valley
Ornithological Club, Academy of Natural Sciences, Philadelphia. 1972: 4 x 7 in..
39 pp., two maps. No price given.

Regional lists giving the familiar bar graphs indicating dates of occurrence and
abundance of the species together with minimal annotations. Both include brief descrip-
tions of good birding areas. — G. A. H.

SUGGESTIONS TO AUTHORS

Manuscripts. — Manuscripts intended for publication in The Wilson Bulletin should be
neatly typewritten, double-spaced {especially tables and 'literature cited”), with at least
one-inch margins all around, and on one side of good quality white paper. Ribbon copies
are preferred but xerographic copies will be accepted if in readable condition. The review
process may be hastened if a duplicate copy (carbon or xerographic) is submitted. All
pages should be numbered.

Tables. — Tables are expensive to print and authors should consider carefully whether
or not a table is really necessary or adds to the paper. Tables should be designed so as
to be narrow and deep rather than wide and shallow. Double space all entries in tables,
including titles. Do not use vertical rules. Tabulate only such data as are important to
the point at hand. Tables should be typed on separate sheets and placed at the end of
the MS.

Figures. — All illustrations should be prepared (particularly insofar as the lettering
goes) so as to be readable when reduced in size. The final size will usually be 4.5 inches
wide. Illustrations larger than 8)4 X H will not be accepted, and these should be reduced
photographically before submitting. Legends for all figures should be typed on a separate
sheet. Photographs should be clear, of good contrast, and on glossy paper. Drawings
should be in India ink on good drawing board, drafting paper, or blue-lined graph paper.
All lettering on drawings should be done with a lettering instrument or the equivalent.
Designate the top of each illustration and identify (on the back in soft pencil) with
author’s name, and figure number. Submit a duplicate or readable xerographic copy of
each figure for the use of the reviewer.

Style and Format. — For general matters of style in preparing a scientific article authors
should consult the “CBE Style Manual,” 3rd Ed., Am. Inst. Biol. Sci., Washington, D.C.
1972. All MSS should be submitted in the general format used in recent issues of the
Bulletin. Avoid footnotes, and avoid more than two levels of subject subheadings. Except
in rare circumstances lead papers should be followed by a summary, not to exceed 10
percent of the length of the paper. Summaries should be informative when standing by
themselves. Most units should be given in the metric system, and compound units should
be given in one-line form (i.e. cm-sec“^). The continental system of dating (21 March
1972) and the twenty-four hour clock (09:00 and 22:00) should be used.

References. — If more than five papers are cited these should be included in a terminal
“Literature Cited” section. Include only such references as are actually cited, and include
only material that is available in the open literature (“In-house” technical reports and
the like should not be cited). The style of citation can be obtained from recent issues
of the Bulletin. For abbreviations of periodical names use the list given in “Biological
Abstracts List of Serials,” Bioscience Information Service, Philadelphia, Pa., 1968. If in
doubt, do not abbreviate serial names. All references in “General Notes” and in long
papers containing less than five references should be cited internally e.g. (Janies, Wilson
Bull., 83:215-236, 1971) or James (Wilson Bull., 83:215-236, 1971).

Nomenclature. — Common names and technical names of birds should be those given in
the 1957 A.O.U. Check-list (and such supplements as may appear) unless justification is
given for departing from this list. For bird species in Middle and South America the
Bulletin uses the common names appearing in Eisenmann, “Species of Middle American
Birds,” 1955 and Meyer de Schauensee “The Species of Birds of South America,” 1966.
Common names of birds should be capitalized.

513

THE WILSON ORNITHOLOGICAL SOCIETY

Officers, 1972-1973

President Pershing B. Hofslund

First Vice-President Kenneth C. Parkes

Second Vice-President Andrew J. Berger

Secretary James Tate, Jr.

Treasurer William A. Klamm

Editor George A. Hall

Additional Members of the Executive Council
Elective Members

Elden W. Martin Robert D. Burns Harvey I. Fisher

Past Presidents

Albert F. Gainer Maurice G. Brooks Phillips B. Street

Margaret M. Nice Walter J. Breckenridge Roger Tory’ Peterson

George M. Sutton John T. Emlen, Jr. H. Lewis Batts, Jr.

S. Qiarles Kendeigh Lawrence H. Walkinshaw William W. H. Gunn

Olin Sewall Pettingill, Jr. Harold F. Mayfield

Trustees

Phillips B. Street Edward L. Altemus Allan Crawford, Jr.

Editorial Staff of The Wilson Bulletin
Editor

George A. Hall
Editorial Advisory Board

William C. Dilger Helmut C. Mueller

Douglas A. James Robert W\ Nero

William A. Lunk Kenneth C. Parkes

Andrew J. Meyerriecks Glen E. Woolfenden

Ornithological Literature Editor
Peter Stettenheim

Chairmen of Committees

Annual Meeting Helmut C. Mueller

Conservation Gustav A. Swanson

Endowment Don L. Bleitz

Library William A. Lunk

Membership Norman L. Ford

Research Val Nolan, Jr.

Student Membership Douglas A. James

514

INDEX TO VOLUME 84, 1972

By Emma J. Messerly and John F. Messerly

This index includes in addition to the names of genera, species, and authors, references
to the following topics: aggression, anatomy, banding, behavior, breeding, care of young,
communication, conservation, copulation, courtship, clutch size, density, display, distribu-
tion, ecology, eggs, food and food habits, genetics, growth and development, habitat,
hatching, incubation, measurements, migration, molts and plumages, mortality, nest site,
nesting, nesting success, nests, parasitism, pesticides, physiology, populations, predation,
recognition, roosting, seasonal distribution, taxonomy, territory, voice and vocalizations,
weather, and weights. Also included are references of biological significance to reptiles
and mammals. Forms described as new in this volume are given in boldface.

Able, Kenneth P., Fall migration in coastal
Louisiana and the evolution of migra-
tion patterns in the gulf region, 231-
242

Abnormality, 342-344
Accipiter cooperii, 64, 341, 422
striatus, 64, 341

Acrocephalus familiaris familiaris, 213
f. kingi, 212
Actitis, 333

macularia, 331, 334, 420, 492
Adaptation, 315-328, 337
Agelaius phoeniceus, 98, 243, 349, 430, 435
tricolor, 243

Aggression, 28, 36, 50-51, 52, 60, 61, 64, 65,
66, 67, 68, 71, 73, 77, 78, 84, 86, 96-97,
98, 176, 254, 256, 257, 258, 259, 297,
309, 310, 311, 313, 399, 400-401, 402,
403, 413, 415, 498
Agouti, 397

Agren, Greta, see Sjolander, Sverre, and

Alford, John R., Ill and Eric G. Bolen, A
note on Golden Eagle talon wounds,
487-489

Akepa, 95-97, 212
Hawaii, 213
Kauai, 95-97
Maui, 213
Oahu, 213
Akialoa, 213
Kauai, 213
Akiapolaau, 213, 215
Albatross, Black-footed, 13
Laysan, 7-27

Royal, 23
Short-tailed, 7
Wandering, 13, 23
Amakihi, 96, 97, 212
Greater, 213
Lanai, 213

Amazona vittata, 498

Ames, Peter L., The Morphology of the
Syrinx in Passerine Birds, reviewed,
224-225; review by, 506-507
Ammodramus bairdii, 54
savannarum, 54
caudacuta, 54
maritima, 54, 491
Anabacerthia, 317
Anas spp., 489
acuta, 486
crecca, 483
discors, 486
laysanensis, 212

platyrhynchos, 90, 131, 342, 483, 486
wyvilliana, 212

Anatomy, 315-328, 329-339, 342-344

Angle, J. P., see Watson, G. E., and

Anianiau, 96, 97, 212
Anolis sp., 498
limifrons, 392, 410
Anser sp., 489
fabalis, 259, 290

Antbird, 383, 389, 398, 399, 415, 416
Bare-crowned, 400, 420
Bicolored, 382, 384, 387, 390, 392, 394,
395, 396, 397, 398, 399, 400, 401, 402,
403, 415, 420
Black-headed, 400, 420

515

516

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Chestnut-backed. 398, 420
Harlequin. 398. 420
Lunulated. 398. 420

Ocellated. 384. 388, 394, 397. 399, 400,
413, 420

Rufous-throated. 398, 420
Scale-backed. 399, 420
Spotted. 384. 387, 397. 398. 400. 420
\^'hite-bro4ved. 398
\^’hite-plumed. 398, 420
hite-throated, 399-400, 420
Anting. 392-395
Antshrike, Slat>-, 379, 400, 420
Antwren. 411
Anumbius, 317
Apapane. 96, 97, 212
Lanai. 213

Aphelocoma ultramarina. 204
Aphrastura, 317
Aplonis atrifusca. 375
Apus affinis, 337
apus, 337
Aquila audax, 487

chiAsaetos, 292, 487, 490
Aracari. Collared. 32, 37, 45, 397, 420
Arbib, Robert and Tony Soper, The Hungr>-
Bird Book, reviewed. 359
Ardea cinerea, 256
c. jouyi, 259
herodius, 341
Arenaria, 333
interpres, 330, 331, 334
Arnold. Keith, review by, 225-226
Asio flammeus, 183, 425
Asthenes, 317
Asyndesmus, 320
lewis, 320

Attila spadiceus, 420
Attila. Bright-rumped, 400, 420
Austin. Oliver L., Jr., Families of Birds,
renewed, 197
Automolus, 317, 319
ochrolaemus, 316, 325
Aythya. 483

Bailey, Alfred M., Field Work of a Museum
Naturalist, Museum Pictorial No, 22.
re^■iewed, 361; Galapagos Islands, Mu-
seum Pictorial No. 19, reviewed, 360
Baiomys taylori, 437

Baida. Russell P., Gary C. Bateman, and
Gene F. Foster, Flocking associates of
the Pinon Jay, 60-76

Baida, Russell P., see Carothers, Steven N.,

and

Bananaquit, 498, 500

Banding, 7. 9. 13, 16, 17, 21, 48. 49. 204.
208, 309. 310, 349, 379, 399. 403. 404.
406. 414. 434, 436, 456
Barash, Da^■id P., Lek behavior in the
Broad-tailed Hummingbird. 202-203
Bare-eye, Black-spotted, 400, 420
Reddish-winged, 420
Rufous-winged, 400

Barlow, Elizabeth, The Forests and Wet-
lands of New York City, reviewed. 510
Bartramia longicauda, 341
Bar>phthengus ruficapillus. 420
Bateman, Gar>- C., see Baida. Russell P..

and

Bat. Red. 204

Beach, Mrs. Francis H., Editor, The Del-
mana Ornithologist, reviewed, 361
BehaWor, 28-47, 48-59, 60-76, 77-89, 98.
136-148. 149-163, 164-172, 173-178,
182. 183, 184-185, 193-197, 199-200,
200-201, 201-202, 202-203. 204-205.
205-206, 243-249. 250-260, 278-295.
296-308, 309-314, 341, 344. 348, 349,
377-420, 425-427, 482-483. 486. 487,
492, 494, 495, 496, 498-500
Berger, Andrew J., Hawaiian birds 1972,
212-222; Bird Study, reviewed, 512
Besser, Jerome F., see Stone, Charles P.,

and

Bittern. Pinnated. 90
Stripe-backed, 201
Blackbird, 436, 439, 445
Brewer’s, 72
Red-breasted, 99

Red-winged, 98, 243-249, 349-350, 429,
430, 435, 436, 439, 441
Tricolored, 243, 244, 247
Blem. Charles R., Stomach capacit\* in the
Common Nighthawk, 492-493
Bobolink, 52, 139, 478
Bobwhite, 439, 441

Bolen, Eric G., see Otteni, Lee C. and

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

517

; see Alford, John R., Ill and

Bombycilla cedrorum, 70, 469

Bonasa umbellus, 261

Bond, James, Native and Winter Resident
Birds of Tobago, reviewed, 197 ; Native
Birds of Mt. Desert Island and Acadia
National Park, reviewed, 197

Botaurus pinnatus caribaeus, 90

р. pinnatus, 90

Boyd, J. C., see Watson, G. E., and

Boyd, M. M., see Watson, G. E., and

Brady, Alan W., Ronald Logan, John C.
Miller, George B. Reynard, and Robert
H. Sehl, A Field List of the Birds of
the Delaware Valley Region, reviewed,
512

Branta canadensis, 90, 278, 341, 389

с. interior, 278, 282, 283
c. maxima, 282, 283, 291
c. parvipes, 278, 283, 291
c. sandvicensis, 212

Breeding, 8, 28, 29, 30, 31, 32-35, 42-45,
46, 296-308, 403, 422, 427-428, 492,
493

Brewer, Richard, An evaluation of winter
bird population studies, 261-277

Bridge, David, see Humphrey, Philip S.,
and

Bridge, M. A., see Watson, G. E., and

Brooks, Maurice, review by, 355-356
Browne, Micou M., and William Post, Black
Rails hit a television tower at Raleigh,
North Carolina, 491-492
Brotogeris versicolorus, 498
Bubo virginianus, 60, 179, 422
Bucephala, 483
Bulbul, Red-vented, 375
Bull, John, review by, 510
Bullfinch, Puerto Rican, 499, 500
Bulweria bulweria, 198
Bunting, Indigo, 139, 140, 210
Painted, 139, 140

Burton, Jean, see McNeil, Raymond, and

Burtt, Edward H., Jr., Eggshell removal in
the Spotted Sandpiper, 492
Buteo jamaicensis, 64, 341, 421, 490

lagopus, 64, 422, 490
lineatus, 341
regalis, 490
solitarius, 212
swainsoni, 92

Butorides virescens, 140, 458
Cain, Brian, Cold hardiness and the de-
velopment of homeothermy in young
Black-bellied Tree Ducks, 483-485
Calidris canutus, 331, 332, 336
Callicebus cupreus, 397
Campephilus, 28, 29, 38
guatemalensis, 34, 42, 43
magellanicus, 29, 31, 39
melanoleucos, 28, 31, 34, 35, 40, 41, 42,
43, 44

principalis, 28, 35
robustus, 37

Campethera abingoni, 320
nubica, 320

Campylorhamphus, 318
Campylorhynchus brunneicapillus, 484
Canadian Wildlife Service Report Series,
Studies of Bird Hazards to Aircraft,
reviewed, 223-224
Capella gallinago, 331, 332, 336
Capito niger, 319, 320
Captive bird, 177, 179, 248, 449
Cardinal, 341, 449, 450, 451, 452, 453, 454,
455

Care of young, 21, 34, 35, 36, 52, 63, 91, 202,
205-206, 243-248, 256, 297, 304-305,
306, 409, 410, 411, 412, 414, 460, 484,
497

Carothers, Steven W., N. Joseph Sharber,
and Russell P. Baida, Steller’s Jays
prey on Gray-headed Juncos and a
Pygmy Nuthatch during periods of
heavy snow, 204-205

Carpenter, Charles C., see Purdue, James

R., and

Carpodacus cassinii, 70
mexicanus, 478
purpureus, 451

Case, Dennis, see Peek, Frank W., and

Cassidix mexicanus, 435
Casto, Stanley I)., see Chapman, Brian R.
and

518

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Casualty,

motor vehicle, 423
television tower, 491
wire, 486-487
Catbird, 139, 430
Catharacta maccormicki, 190
Cathartes aura, 92, 341
Cebus, 37
capucinus, 397
Celeus elegans, 320, 420
flavus, 320
undatus, 320
Centurus aurifrons, 46
carolinus, 46, 261
Certhia, 319

familiaris, 69, 208, 262, 420
Certhiaxis, 317

Chaetoptila angustipluma, 213
Chaffinch, 177, 478

Chamberlain, David J., see Ryder, John P.,
and

Chapman, Brian R., and Stanley D. Casto,
Additional vertebrate prey of the Log-
gerhead Shrike, 496-497
Charadrius, 333
hiaticula, 492
melodus, 334

semipalmatus, 330, 331, 334
vociferus, 331, 334
Chelidoptera tenebrosa, 320
Chickadee, Black-capped, 262, 265, 266,
268, 275

Carolina, 205-206
Chickaree, 414
Chicken, 469, 470
Domestic, 429, 430
Chlorostilbon maugaeus, 498
Choate, Ernest A., review by, 116; Spec-
tacular hawk flight at Cape May Point,
New Jersey on 16 October 1970, 340-
341

Chondestes grammacus, 69
Chondrohierax uncinatus, 420
Chordeiles minor, 492
Ciccaba virgata, 420
Cinclodes, 317
fuscus, 316
Cinclus, 319

Circus cyaneus, 341, 490

Ciridops anna, 213
Citellus tridecemlineatus, 430
Clarke, Robert F., see James R. Purdue
and

Clutch size, 91, 12S-126, 187, 204, 244,
442-444, 470, 471
Coccyzus americanus, 439
Cochlearius cochlearius, 456-468
c. zeledoni, 456
Coereba flaveola, 498
Colaptes, 320, 322
auratus, 320, 430
cafer, 60, 69, 320
campestris, 320
melanochloros, 320
punctigula, 320
rupicola, 322

Colinus virginianus, 131, 439, 441
Collins, Charles T., and Mary LeCroy,
Analysis of measurements, weights, and
composition of Common and Roseate
Tern eggs, 187-192

Color marking, 48, 49, 51, 309, 311, 379
Color vision, 313
Columba livia, 375

Communication, 28-30, 31, 32, 33, 34, 35,
36, 37, 40, 41, 42, 48, 49-50, 51, 52, 53,
63, 64, 65, 66, 67, 68, 71, 72, 73, 74,
80-84, 86, 96, 98, 136, 144, 146, 173-

178, 210, 243, 247, 248, 296, 297, 298,

375, 379-380, 384, 387, 397, 398, 399,

400, 401, 402, 409, 410, 411, 412, 413,

414, 415, 416, 492
Conservation, 101-105, 212-222
Contopus sordidulus, 69
virens, 195

Conway, William G., review by, 226
Cooke, F., and R. K. Ross, Diurnal and
seasonal activities of a post-breeding
population of gulls in southeastern
Ontario, 164-172

Cooper, James A., and Jon R. Hickin,
Chronology of hatching by laying se-
qence in Canada Geese, 90-92
Cooper, Roy P., review by, 112-113
Coot, 486
American, 486
European, 247
Hawaiian, 212

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

519

Copulation, 28, 30, 31, 32, 33, 296, 297,
302-303, 306, 408, 409, 493, 494
Cormorant, 482
Double-crested, 130, 482-483
Corvus brachyrhynchos, 70, 430
corax, 70
ossifragus, 98, 126
tropicus, 212
Coryphistera, 317

Cottam, Clarence, see Otteni, Lee C. and

Cottontail, 438, 441
Coturnix coturnix, 131, 470
Courser, William D., Variability of tail molt
in the Burrowing Owl, 93-95; see Tait,

William W., and

Courtship, 28, 30, 31, 32-33, 34, 37, 62-63,
68, 96, 202-203, 296, 297, 298-302, 306,
407-108, 409, 414, 415, 486
Cowbird, 244, 248, 436, 497
Bronzed, 435

Brown-headed, 244, 435, 439, 441, 497
Crake, Yellow-breasted, 201
Crane, Common, 258
Hooded, 258
Japanese, 250-260
Lesser Sandhill, 258
Sandhill, 93, 250-260
White-naped, 258, 259
Whooping, 259
Crane-Hawk, 420
Cranioleuca, 317, 319
Creeper, 208, 212

Brown, 208-210, 262, 274, 275, 377, 420

Hawaii, 213

Lanai, 213

Molokai, 213

Oahu, 213

Crews, Wendell E., see Raveling, Dennis G,,

and

Crocethia, 333
alba, 331, 335
Crow, 429, 430
Fish, 98, 126
Hawaiian, 212
Cryptotis parva, 439
Cuckoo, European, 406, 414, 420
Puerto Rican Lizard, 498
Squirrel, 400, 420

Yellow-billed, 439
Cuculus canoris, 420
Cyanocitta cristata, 98, 204, 262, 430
stelleri, 69, 205
Cygnus cygnus, 259
Dasyprocta punctata, 397
Davis, David E., and Frank Peek, Stability
of a population of male Red-winged
Blackbirds, 349-350

De Grazio, John W., see Stone, Charles P.,

and

Deconychura, 318

Demaree, Salome R., Eleanor L. Radke, and
Janet L. Witzeman, Birds of Maricopa
County, Arizona, reviewed, 512
Dendrexetastes, 318
Dendrocincla, 318, 377, 390
anabatina, 420
fuliginosa, 377-420
homochroa, 420
merula, 420

Dendrocolaptes, 318, 390
certhia, 420
hoffmannsi, 420
picumnus, 420
Dendrocopos borealis, 320
major, 320

pubescens, 39, 60, 69, 262, 320, 493
scalaris, 320

villosus, 38, 60, 69, 262, 316, 320
Dendrocygna autumnalis, 483
Dendroica auduboni, 69
caerulescens, 498
castanea, 139
coronata, 208, 348
graciae, 69
kirtlandii, 347
pensylvanica, 499
petechia, 139
tigrina, 498

Density, 55-57, 261-277, 407, 424, 425, 427-
428, 490

Dickcissel, 139, 439, 441, 475-481
Dickerman, Robert W,, Further notes on
the Pinnated Bittern in Mexico and
Central America, 90; see Juarez L.,

Carlos, and

Didunculus strigirostris, 375
Digestion, 179-186, 436, 437, 493

520

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Diomedea albatnis. 7
eponiophora. 17
exulans. 13, 17
immutabilis. 7-27
melanophris. 17, 18
nigripes. 13

Display. 30-31. 37. 255. 257. 258. 297. 309.
399. 407, 412. 414

Distribution. 7-27. 99. 119-135. 198. 200-
201. 206-208. 208-210, 344-347. 375-
376

Dolichonyx or>zivonis. 52. 139, 478
Dove. Inca. 439
Mourning. 72, 430, 439
Ring. 131
Rock. 375

Dowitcher. Short-billed. 330. 332. 337
Drepanis funerea, 213
pacifica. 213
Dn ocopus. 29

lineatus. 28, 40, 41. 42. 43, 44, 45. 46. 320
martins. 30

pileatus, 29, 42. 320, 493
Duck. 182. 313. 483, 489
Black-bellied Tree. 483—485
Hawaiian. 212
Koloa. 212
Laysan, 212
Mallard. 131
Ruddy, 486-487

Dumetella carolinensis. 139, 430
Dunning. John S.. Portraits of Tropical
Birds, renewed. 115

du Pont. John E., Notes from western
Samoa, including the description of a
new Parrot-Finch (Er>thrura). 375-376
Eagle. 292, 487
Bald. 292, 490
Golden. 292. 487-489, 490
Wedge-tailed. 487

Ecology-. 8. 10, 11, 12, 13, 14-15, 16, 17, 18,
19, 22, 23. 39. 44-45, 46. 164. 200, 200-
201, 206-208. 208, 209, 243. 244. 254,
375, 377, 421-433, 434-448. 494-496
Eddinger, C. Robert. Discoveiy of the nest
of the Kauai Akepa, 95-97
Egg-binding, 493-494

Eggs. 90-92, 93. 95, 96, 97. 98-99. 125. 126.
127-132, 187-192, 204. 244. 245, 246,

247. 248. 296, 309-314, 410, 422. 428.
443. 456, 459, 469^74, 483, 492, 497
artificial. 309-314
composition of, 187-192
recognition of, 309, 312, 313
Egret. 259
Sno-ssy. 199-200
Eira barbara. 386
Electron plaUrinchum, 420
Ellison. Nancy, reHew by, 359
Embr>olog>', 470-471
Emerald. Puerto Rican, 498, 500
Empidonax. 195
traillii. 194, 195
Hrescens. 420

Enderson. James H,, see Johnson. DaHd,

and

Eremobius, 317
Eremophila. 319
alpestris, 70
Ereunetes, 333
pusillus. 331, 335
Erithacus rubecula, 149-163
Erolia, 333
alpina. 331. 335
fuscicollis, 331, 335
melanotos. 331, 335
minutilla. 330, 331, 335
Enthrura. 375-376

cyaneoHrens, 376, color plate facing page
375

c. cyaneoHrens, 376
c. gaughrani. 376
c. regia, 376
c. serena. 376
Eucometis penicillata. 420
Eudocimus ruber, 99
Euphagus cyanocephalus, 70
Euphonia fulHcrissa, 499
music a, 499
Euphonia, 499
Blue-hooded. 499

Evolution. 45, 77-89, 231-242. 318, 319, 322.
325-327, 337

Falco columbarius, 341, 490
mexicanus, 490
peregrinus. 132, 341, 375
p. nesiotes, 375

spar%-erius. 130, 340, 425, 439, 490, 491

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

521

Falcon, Peregrine, 132, 341
Prairie, 490

Falk, Lloyd L., Bird Census Surveys of the
Hoopes Reservoir Area, New Castle
County, Delaware, reviewed, 361
Falkus, Hugh, see Tinbergen, Niko, and

Farber, Harvey, Evidence of two Tree
Swallow females sharing the same nest
box, 204

Feduccia, Alan, Variation in the posterior
border in some tree-trunk foraging
birds, 315-328
Felis yagouaroundi, 397
Finch, 79, 84, 450
Galapagos, 212
Greater Koa, 213
Grosbeak, 213
House, 478, 479
Laysan, 213
Lesser Koa, 213
Nihoa, 213
Parrot, 375-376
Purple, 450, 451, 452, 453, 454
Fisher, Harvey L, and James R. Fisher,
Distribution of the Laysan Albatross,
Diomedea immutabilis, 7-27
Fisher, James R., see Fisher, Harvey I.,
and

Fitzgerald, Theodore C., The Coturnix
Quail ; Anatomy and Histology, re-
viewed, 109-112
Flicker, 73
Andean, 322

Red-shafted, 60, 62, 64, 66-67, 71, 74
Yellow-shafted, 430
Florida caerulea, 99
Flycatcher, 196
Acadian, 400, 420
Alder, 194, 195
Crested, 195
Great Kiskadee, 344
Rusty-margined, 344
Streaked, 398, 420
Flycatchers, tyrant, 195
Food and food habits, 8, 13, 14, 15, 16, 18,
19, 20, 21, 23, 32, 34, 35, 38-42, 60-76,
96, 165, 166-167, 168, 171, 179-186,
193-196, 199-200, 201, 201-202, 204-

205, 207, 250, 251, 252, 253, 254, 255,

256, 257, 258, 259, 278, 285, 286, 288,

289, 290, 291, 292, 337, 341, 344, 377,

386, 388-392, 410, 411, 412, 414, 417,

421, 422, 423, 426, 429, 430, 431, 434^

448, 449-455, 491, 492, 493, 496-497,
498-500

Forest-Falcon, Barred, 420
Lined, 398, 420

Foster, Gene F., see Baida, Russell P., and

Fowl, domestic, 182, 471
Fox, 431

Frank, Peter W., see Johnston, Richard F.,
and

Franks, Edwin, see Peek, Frank W., and

Fredrickson, Leigh H., and Milton W.
Weller, Responses of Adelie Penguins
to colored eggs, 309-314
Fringilla coelebs, 177, 478
Fulica americana, 486
a. alai, 212
atra, 247

Fulmar, 13, 18, 23
Fulmarus glacialis, 13
Furnarius, 317

Fyfe, R. W., see Keith, J. A., and

Galbula dea, 320
galbula, 320
ruficauda, 320
Gallinula chloropus, 201
c. sandvicensis, 212
Gallinule, Common, 201
Hawaiian, 212
Purple, 208-210
Callus gallus, 469
Gannet, 198-199

Gates, John M., Red-tailed Hawk popula-
tions and ecology in east-central Wis-
consin, 421-433

Gauthreaux, Sidney A., Jr., Behavioral re-
sponses of migrating birds to daylight
and darkness: a radar and direct

visual study, 136-148
Gavia arctica, 298, 305, 306
immer, 296, 300, 306
stellata, 300, 303, 304, 305, 306
Genetics, 77-78, 78-79, 80, 84-86, 87

522

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Geomys bursarius, 439

George, William G., Breeding status of the
Purple Gallinule, Brown Creeper, and
Swainson’s Warbler in Blinois, 208-210
Geositta, 317

Geranospiza caerulescens, 420

Gilbert. Barrie, see Pulliam, Ronnie, and

Gilbert. Douglas L., Natural Resources and
Public Relations, reviewed, 225-226
Glyphorhynchus, 318, 389
spirurus, 420

Gnatcatcher, Blue-gray, 346
Goatsucker, 196

Gochfeld, Michael, Observations on the
status, ecology, and behavior of Soras
wintering in Trinidad, West Indies,
200-201

Goertz, John W., and KJm Rutherford, Adult
Carolina Chickadee carries young, 205-
206

Goldfinch, 52
Goose, 292, 293, 489
Bean, 259, 290, 291, 292
Canada, 90-92, 27R-295, 341, 489
Domestic, 489
Hawaiian, 212
Nene, 212

Gopher, Pocket, 438, 439, 441
Graber, Richard, review by, 223-224
Crackle, 436, 439
Boat-tailed, 435, 441
Common, 430
Gracula religiosa, 177
Grassquit, 77-89
Black-faced, 499
Yellow-faced, 77, 84

Greenlaw, Jon S., The use of sawdust piles
by nesting Bank Swallows, 494-496
Grosbeak, 139, 140
Rose-breasted, 139, 140, 450
Ground-Cuckoo, Rufous-vented, 400, 420
Grouse, Ruffed, 261, 266, 268, 275
Growth and development, 35-36, 176, 177,
189, 201-202, 305, 329-339, 456-468,
475-481, 483-485
Grus americana, 259
canadensis, 250, 257, 258
c. canadensis, 258

c. tabida, 93

cinerea longirostris, 258

grus, 258

japonensis, 250, 256, 257, 258, 259
monacha, 258
vipio, 258, 259
Guiraca caerulea, 139
Gull, 164-172, 482
Glaucous, 164

Great Black-backed, 164, 305
Herring, 164, 166-167, 171, 309
Iceland, 164

Ring-billed, 164, 342-344
Gunn, William W. H., see Keith, Stuart,
and

Gymnocichla nudiceps, 420
Gymnopithys bicolor, 420
lunulata, 420
rufigula, 420
salvini, 420

Gymnorhinus cyanocephalus, 60
Habitat, 32, 33, 38, 39, 45, 46, 48, 49, 61,
77, 78, 79, 86-87, 96, 201, 206-208, 341,
346, 347-349, 349, 375, 377, 409, 410,
421, 422, 425, 434, 437, 494-496
Haematopus ostralegus, 492
Haliaeetus leucocephalus, 292, 490
Hall, George A., reviews by, 36, 361, 361,
361, 512

Harpagus bidentatus, 420

Harper, P. C., see Watson, G. E., and

Hatching, 90-92, 492, 497
Hatching success, 126, 127
Haverschmidt, F., The migration of the Buff-
breasted Sandpiper through Surinam,
341-342

Hawk, 64, 340-341, 397, 398, 415
Cooper’s, 64, 341, 422, 425, 426
Ferruginous, 490
Hawaiian, 212
Marsh, 341, 490
Pigeon, 341, 490
Red-shouldered, 341
Red-tailed, 64, 341, 421-433, 490
Rough-legged, 64, 167, 422, 423, 424, 425,
426, 427, 490
Semiplumbeous, 420
Sharp-shinned, 64, 341
Sparrow, 340, 425, 439, 490, 491

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

523

Swainson’s, 92-93
White, 420

Heintzelman, Donald S., Rare or Endan-
gered Fish and Wildlife of New Jersey,
reviewed, 172

Hemignathus lucidus affinis, 213
1. hanepepe, 213
1. lucidus, 213
obscurus, 213
procerus, 213
wilsoni, 213

Heron, 200, 258, 259, 482
Black-crowned Night, 212, 458, 461, 464
Boat-billed, 456-468
Eastern Gray, 259
Gray, 256
Great Blue, 341
Green, 140, 458, 462
Little Blue, 99
Louisiana, 200
Yellow-crowned Night, 140
Hesperiphona vespertina, 70
Hewitt, Oliver H., review by, 510-511
Hickin, Jon R., see Cooper, James A., and

Himantopus himantopus knudseni, 212
Himatione sanguinea, 96
s. freethii, 213
s. sanguinea, 213
History, 344-347

Hock, Hiltrud, see Wiltschko, Wolfgang,
and

Holmes, Richard T., review by, 352-353
Honeycreeper, 212, 215
Crested, 213
Laysan, 213
Maui Crested, 213
Hummingbird, 203
Broad-tailed, 202-203

Humphrey, Philip S., David Bridge, Per-
cival W. Reynolds, and Roger Tory
Peterson, Birds of Isle Grande (Tierra
del Fuego), reviewed, 107-109
Hydranassa tricolor, 200
Hylexetastes, 390
perrotti, 420
Hylocichla, 206, 207
fuscescens, 206
guttata, 206

mustelina, 139, 206
ustulata, 206, 420
Hylocryptus, 317
Hyloctistes, 317
Hylophylax naevioides, 420
poecilonota, 420
Ibis, 200
Scarlet, 99

Icterus galbula, 139, 497
spurius, 139
liwi, 96, 97, 212, 213
Molokai, 213
Oahu, 213

Incubation, 34, 36, 93, 95, 95, 99, 204, 245,
303-304, 306, 309, 310, 311, 312, 313,
409-410, 412, 442, 459, 497
Indicator indicator, 320
variegatus, 320
Iridoprocne bicolor, 204
Ixobrychus involucris, 201
Jacana jacana, 201

Jacoby, H., G. Knotsch, and S. Schuster,
Die Vogel des Bodenseegebietes, re-
viewed, 99
Jaguarundi, 397

Juarez L., Carlos, and Robert W. Dicker-
man, Nestling development of Boat-
billed Herons (Cochlearius cochlearius)
at San Bias, Nayarit, Mexico, 456-468
Jay, 205

Blue, 98, 204, 262, 272, 275, 430
Mexican, 204
Pinon, 60-76

Steller’s, 64, 72, 74, 204-205
Johnson, David, and James H. Enderson,
Roadside raptor census in Colorado —
winter 1971-72, 489-490
Johnson, H. Malcolm, see Tait, William
W., and

Johnston, Richard F., Peter W. Frank, and
Charles D. Michener, Editors, Annual
Review of Ecology and Systematics,
reviewed, 512

Jones, Thomas C,, Editor, Text by Russ
Williams, The Ways of Wildfowl. Re-
productions of Etchings and Paintings
by Richard E. Bishop, reviewed, 509-
510

Junco caniceps, 70, 205

524

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

hyenialis. 70, 450
oreganus. 70

Junco. 64, 74. 205, 451, 452, 453
Gray-headed, 204-205
Slate-colored, 450, 454
Jynx torquata, 320

Keith. J. A., and R. W. Fyfe, Pesticides
and ildlife, reviewed, 178
Keith. Stuart, and William W. H. Gunn,
Producers, Birds of the African Rain
Forests. Sounds of Nature No. 9, re-
viewed, 507-509

Kestrel, American, 130, 131, 132
Kieran. John, A Natural Histor>- of New
York City, reviewed, 105
Kilham, Lawrence, Habits of the Crimson-
crested Woodpecker in Panama, 28-47 ;
Retention of egg in wild Downy Wood-
pecker, 493-494
Killdeer, 337

King, Warren B., The Trade Wind Zone
Oceanography Pilot Study. Part VII:
Observations of Sea Birds, March 1964
to June 1965, reviewed, 356-358
Kingbird, Eastern, 139
Western, 497

Kinglet, Ruby-crowned, 346
Kioea, 213
Kiskadee, Great, 344
Kite, Double-toothed, 420
Gray-headed, 420
Hook-billed, 420
Kittiwake, 247
Kiwi, 194

Klemm, Robert D., review by, 109-112
Klimstra, W. D., see Raveling, Dennis G.,
and

Klopfer, Peter, see Pulliam, Ronald, and
Knot, 332, 337

Knotsch, G., see Jacoby, H., and

Kroodsma, Donald E., Variations in songs
of Vesper Sparrows in Oregon, 173-178
Kuroda, Nagahisa, review by, 356-358
Kushlan, James A., Aerial feeding in the
Snowy Egret, 199-200
Lack, David, Ecological Isolation in Birds,
reviewed, 352-353

Lanius excubitor, 496
ludovicianus, 69, 496, 497
Larus argentatus, 164, 309
delawarensis, 164, 342
glaucoides, 164
hyperboreus, 164
marinus, 164, 395
Lasiurus borealis, 204
Laterallus jamaicensis, 491
Laughlin, Sally, review by, 228
Leafscraper, 382
Scaly-throated, 400, 420
Leek, Charles F., Observations of birds at
Cecropia trees in Puerto Rico, 498-500
LeCroy, Marv', Young Common and Roseate
Terns learning to fish, 201-202; see

Collins, Charles T., and

Lederer, Roger J., The role of avian rictal
bristles, 193-197

Lein, M. Ross, see Nero, Robert W., and

Leistes militaris, 99
Lepidocolaptes, 318
Leptasthenura, 317
Leptodon cayanensis, 420
Leuconerpes candidus, 320
Leucophoyx thula, 199
Leucopternis albicollis, 420
semiplumbea, 420
Ligon, J. David, revdew by, 360
Limnodromus griseus, 330, 331, 336
Limnothlypis swainsonii, 209
Limosa, 333
haemastica, 335

Littlefield, Carroll D., An unusual nest of
the Sandhill Crane, 93
Lizard, 79, 392, 406, 410, 414
Tree, 498
Lochmias, 317

Logan, W. Ronald, see Brady, Alan, and

Loomelania melania, 198
Loon, 296, 297, 305
Common, 296-308
Loxigilla portoricensis, 499
Loxops coccinea, 95
c. caeruleirostris, 95, 212
c. coccinea, 95, 213

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

525

c. ochracea, 95, 213
c. rufa, 95, 213
maculata bairdi, 212
m. flammea, 213
m. maculata, 213
m. mana, 213
m. montana, 213
m. newtoni, 212
parva, 96, 212
sagittirostris, 213
virens, 96
V. wilsoni, 213

Ludwig, James P., review by, 227-228
Lymnocryptes minimus, 337
Macronectes giganteus, 7
Maher, William J., review by, 503-504
Malocoptila panamensis, 320, 420
Mallard, 90, 156, 342, 383, 486, 489
Mamo, 213
Black, 213

Management, Game, 292-293
Marcellini, Dale L., see Purdue, James R.,
and

Margorops fuscatus, 498
Margarornis, 317, 319
Marmoset, 339, 411
Geoffrey’s, 37

Masatomi, Hiroyuki, Communal wintering
of a Sandhill Crane with Japanese
Cranes in Hokkaido, Japan, 250-260
Maxwell, Terry C., Spring migration of the
Gannet in Florida waters, 198-199
Mayfield, Harold F., Winter habitat of Kirt-
land’s Warbler, 347-349
McCormick, Jack, The Pine Barrens. A
Preliminary Ecological Inventory, re-
viewed, 115-116

McDonald, Dennis, see Pulliam, Ronald,
and

McDonald, Linda, see Pulliam, Ronald, and

McNeil, Raymond, and Jean Burton, Cranial
pneumatization patterns and bursa of
Fabricius in North American shore-
birds, 329-339
Meadowlark, Western, 177
Mean ley, Brooke, Natural History of the
Swainson’s Warbler, reviewed, 355-356
Measurements, 90, 93, 97, 187-192, 376, 378,

456, 457, 460, 461, 462, 463, 469-474,
476, 478, 491, 492, 492-493
Meiglyptes tukki, 320
Melanerpes, 320
aurifrons, 320
carolinus, 320
chrysogenys, 320
erythrocephalus, 320
formicivorus, 70, 320
portoricensis, 498
pucherani, 44, 320
uropygialis, 320
Melanitta, 483

Melospiza melodia, 52, 54, 247, 450
Mergus, 483

Meyerriecks, Andrew J., Tool-using by a
Double-crested Cormorant, 482-483
Michener, Charles D., see Johnston, Rich-
ard F., and

Micrastur gilvicollis, 420
ruficollis, 420
Microtus, 184, 429
spp., 430
ochrogaster, 179
pennsylvanicus, 491
Migrants, 475, 491-492, 499, 500
Migration, 49, 53, 92-93, 136-148, 149-163,
198-199, 231-242, 256, 340-341, 341-
342, 344, 345

Miller, John C., see Brady, Alan, and

Millerbird, Laysan, 213
Nihoa, 212 ,

Millikan, George, see Pulliam, Ronald, and

Mills, Gregory S., see Clive A. Petrovic
and

Mimocichla plumbea, 498
Mimus polyglottos, 98, 420
Miskimen, Mildred, review by, 224-225
Mniotilta varia, 349, 498
Mockingbird, 98, 391, 420
Moenke, Helen, Ecology of Colorado Moun-
tains to Arizona Deserts, reviewed, 105
Moho apicalis, 213
bishopi, 213
braccatus, 212
nobilis, 213

Molothrus ater, 70, 244, 435, 497

526

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Molts and plumages, 53, 93-95, 250-251,
330. 376, 394, 464-467, 482
Monasa atra, 320
Monkey, 37

bite-faced, 397

Montgomery, Vester A., Bird-Finding Lo-
calities in the Vicinity of Roswell, New
Mexico, reviewed. 511
Morrison, James V., see Zimmerman, John
L.. and

Morse. Douglas H., Habitat differences of
Swainson’s and Hermit Thrushes, 206-
208

Mortality, 423, 426, 428, 486, 487, 491
nestling, 21
Morus bassanus, 198
Motmot, Broad-billed, 400, 420
Rufous, 400, 420

Mott, Donald F., see Stone, Charles P,,

and

Mouse, 440
Deer, 437, 446

Fulvous Harvest, 437-438, 441
Harvest, 437, 446
Hispid Pocket, 437, 441, 446
House, 437, 446
Meadow, 430
Merriam's Pocket, 497
Pocket, 438, 497
Pygmy, 437, 438, 440, 441, 446
White-footed, 438, 441
Murphy. Robert Cushman, renew by, 504-
505

Murre, 244

Common, 130, 243, 244
Muskrat, 430
Myiarchus crinitus, 195
Myiodynastes maculatus, 420
Myiozetetes cayanensis, 344
similis, 344

Mynah, Indian Hill, 177
Myrmeciza exsul, 420
Navigation, 149-165
Neomorphus geoffroyi, 420
Neospingus speculiferus, 499
Neotoma micropus, 438
Nero, Robert W., and M, Ross Lein, Birds
of Moose Mountain, Saskatchewan, re-
newed, 511

Nest failure, 50

Nest site, 46, 54, 96, 244-246, 247, 248, 309,
303, 312, 423, 428, 429, 440-441, 494-
496

Nesting, 34-35, 49, 55-57, 58, 63, 95, 95-97,
98-99, 125, 204, 205-206, 409-414, 456
Nesting success, 91, 119, 120, 121, 122, 123,
124, 125, 246, 424, 428, 443, 444, 445
Nests, 29, 30, 32, 33, 34, 35, 42^5, 54, 55,
91, 93, 95, 96, 97, 98, 98, 125, 201, 204,
243, 244, 245, 246, 247, 248, 297, 303,
309, 310, 311, 312, 313, 410, 422, 428,
437, 483, 497
Nighthawk, 492
Common, 492-493

Niles, David M., Catalog of Bird Specimens
Southwestern Museum of Natural His-
tory, reviewed, 511
Notharchus macrorhynchos, 320
pectoralis, 420

Nucifraga Columbiana, 60, 70
Nukupuu, Kauai, 213
Maui, 213
Oahu, 213
Numenius, 333
phaeopus, 334
Nutcracker, 73

Clark’s, 60, 61, 62, 67, 71, 72, 74
Nuthatch, 205
Pygmy, 204-205

White-breasted, 262, 265, 266, 267, 275
Nyctanassa violacea, 140
Nyctea scandiaca, 422
Nycticorax nycticorax, 458
n. hoactli, 212

Oceanodroma castro cryptoleucura, 212
Ochetorhyncbus, 317
Oedepomidas geoffroyi, 37
Olrog, Claes C., renew by, 107-109
Ondatra zibethicus, 430
Oo, Hawaii, 213
Kauai, 212
Molokai, 213
Oahu, 213

Oriole, Baltimore, 139, 139-140, 497
Orchard, 139

Ornithological Literature, 106-116, 223-228,
352-360, 503-511
Oryzomys palustris, 438

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

527

Osprey, 341, 341

Otteni, Lee C., Eric G. Bolen, and Clarence
Cottam, Predator-prey relationships and
reproduction of the Barn Owl in south-
ern Texas, 434-448
Otus asio, 425
Ou, 213
Hawaii, 213
Kauai, 213
Maui, 213

Ovenbird, 318, 325, 326, 327
Owl, 64, 179
Barn, 179-186, 434-448
Barred, 425
Burrowing, 93-95

Great Horned, 60, 64, 179, 181, 182, 183,
422, 425, 426, 427, 428
Mottled, 397, 420
Screech, 425
Short-eared, 183, 425
Snowy, 422, 425
Spectacled, 35, 397, 420
Tawny, 183

Oxyura jamaicensis, 486
Oystercatcher, 492
Palila, 213, 215
Palmeria dolei, 213
Pandion haliaetus, 341, 341
Paradaptation, 325
Parakeet, Canary'-winged, 498, 500
Parasitism, 497
Parrot, Puerto Rican, 498
Parrotbill, Maui, 213
Parrot-Finch, Red-headed, 375, 376
Partridge, European, 430
Parula americana, 208, 498
Parus atricapillus, 262
bicolor, 262
carolinensis, 206
gambeli, 69

Passer domesticus, 245, 329, 430
Passerculus sandwichensis, 48
Passerella iliaca, 453
Passerherbulus caudacutus, 54
henslowii, 54
Passerina ciris, 139
cyanea, 139, 210

Paynter, Raymond A., Jr., and Robert W.
Storer, Check-List of Birds of the

World, Volume XHI, reviewed, 116
Peek, Frank W., Edwin Franks, and Dennis
Case, Recognition of nest, eggs, nest
site, and young in female Red-winged
Blackbirds, 243-249

Peek, Frank, see Davis, David E., and

Pewee, Eastern Wood, 195
Pelecanus eiythrorhynehos, 130
occidentalis, 119-135, 471
Pelican, 482
Brown, 119-135, 471
White, 130

Penguin, Adelie, 309-314
Pennula sandwichensis, 213
Percnostola rufifrons, 420
Perdix perdix, 430
Peregrine, 375
Perognathus hispidus, 438
merriami, 497
parvus, 497

Peromyscus leucopus, 438
Pesticides, 129-132, 342, 472, 473
Peterson, Roger Tory, see Humphrey, Philip

S., and

Petrel, 198
Black, 198
Bulwer’s, 198
Giant, 7

Hawaiian Dark-rumped, 212
Harcourt’s Storm, 212

Petrovic, Clive A., and Gregory S. Mills,
Sparrow Hawk eats European corn
borer, 491
Phacellodomus, 317
Phaenostictus mcleannani, 420
Phaeornis obscurus lanaiensis, 213
o. myadestina, 212
o. oahensis, 213
o. rutha, 212
palmeri, 212

Phalacrocorax auritus, 130, 482
Phasianus colchicus, 421, 430
Pheasant, 421, 425, 427, 429, 430, 431
Pheasant, Ring-necked, 421, 426, 430, 432
Pheucticus ludovicianus, 139, 450
IMiilohela minor, 332
Philydor, 317

528

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Plilegopsis en throptera, 420
nigromaculata, 420
Phleocnptes, 317
Phloeoceastes, 28
guatemalensis, 320
melanoleucos, 43
rubicollis, 320
Phoebe, Black, 247
Eastern, 195
Phoeniculus, 322, 323
purpurescens, 322, 323
Physiology, 179-186, 475-481, 483-485
Piaya cayana, 420
Picoides arcticus, 320
tridactylus, 320
Piculus flavigula, 320
simplex, 320

Picumnus minutissimus, 320
temminckii, 320
Picus viridis, 320, 322
Pigeon, Tooth-billed, 375
Pintail, 486, 487, 488
Piranga flava, 69
ludoviciana, 69
olivacea, 139
rubra, 139

Pirnie, Miles D., review by, 509-510
Pitangus sulphuratus, 344
Pithys albifrons, 420
Plover, 337

American Golden, 341
Ringed, 492
Semipalmated, 330
Upland, 341
Pluvialis, 333
dominica, 331, 334, 341
Pollutants, 119, 127-133, 342
Pollution, 341

Pooecetes gramineus, 98, 173-178
Populations, 55-57, 77, 80-84, 87, 119-135,
201, 208-210, 261-277, 344-347, 349-
350, 421-433, 435, 436, 490-491
Porphyrula martinica, 208
Porzana Carolina, 200
flaviventer, 201
Porzanula palmeri, 213
Post, William, see Browne, Micou M. and

Savannah Sparrows in southeastern
Michigan, 48-59

Predation, 34-35, 37, 57, 63-64, 98, 126,
204-205, 292, 341, 397-399, 421, 426,
427, 429, 430, 431, 434-448, 487-489,
491, 496-497.

Preening, 254, 395-396, 399, 482-483
Premnoplex, 317, 319
Premnornis, 319
Procyon lotor, 93
Psaltriparus minimus, 70
Pseudocolaptes, 317, 319
Pseudonestor xantliophiys, 213
Pseustes poecilonota, 411
Psittirostra bailleui, 213
cantans cantans, 213
c. ultima, 213
flaviceps, 213
kona, 213
palmeri, 213
psittacea, 213

Pterodroma phaepygia sandwichensis, 212
Pteroglossus aracari, 320
castanotis, 320
torquatus, 32, 320, 420
Publication Notes and Notices, 99, 105, 116,
172, 178, 197, 277, 361, 511-512
Puffbird, Black-breasted, 391, 400, 420
White-whiskered, 400, 420
Puffinus Ihermineri, 198
puffinus newellii, 212

Pulliam, Ronald, Barrie Gilbert, Peter
Klopfer, Dennis McDonald, Linda Mc-
Donald, and George Millikan, On the
evolution of sociality, with particular
reference to Tiaris olivacea, 77-89
Pulsatrix perspicillata, 35, 420
Purdue, James R., Charles C. Carpenter,
and Dale L. Marcellini, Spring migra-
tion of Swainson’s Hawk and Turkey
Vulture through Veracruz, Mexico, 92-
93

Pycnonotus cafer bengalensis, 375
Pygarrhichas, 317, 319
albogularis, 315
Pygoscelis papua, 309
Quail, Bobwhite, 131
Japanese, 131, 470
Quiscalus quiscula, 430

Potter, Peter E., Territorial behavior in

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

529

Rabbit, 341, 439
Cottontail, 423, 429, 430, 439
Raccoon, 93

Radke, Eleanor, see Demaree, Salome R.,
and

Raikow, Robert J., Evolution of Diving
Adaptations in the Stifftail Ducks, re-
viewed, 114-115
Rail, Black, 491-492
Clapper, 491
Hawaiian, 213
Laysan, 213
Spotted, 201
Virginia, 441
Rallus limicola, 441
longirostris, 491
maculatus, 201

Ramphastos sulfuratus, 320, 420
swainsonii, 320, 420
toco, 320

Rand, Austin L., Birds of North America,
reviewed, 505-506
Rat, 440

Cotton, 437, 438, 441, 446
Gray Wood, 438
Norway, 430

Rice, 437, 438, 439, 441, 446
Wood, 437, 438, 441, 446
Rattlesnake, desert massasauga, 496
Rattus norvegicus, 430
Raveling, Dennis G., Wendell E. Crews, and
W. D. Klimstra, Activity patterns of
Canada Geese during winter, 278-295
Recognition, nonspecific, 248
of eggs, 243-249, 309, 312, 313
of nest, 243-249
of young, 243-249
specific, 348
Redstart, American, 499
Redwing, 350
Regulus calendula, 69
Reithrodontomys fulvescens, 438
Reynard, George B., see Brady, Alan, and

Reynolds, Percival W., see Humphrey,

Philip S., and

Rhegmatorhina berlepschi, 420
Rhinopomastos, 322, 323
cyanomelas, 322, 323

Richmond, Milo E., see Smith, Charles R.,
and

Richmondena cardinalis, 341, 449
Riparia riparia, 494

Risebrough, see Schreiber, Ralph W., and

Rissa trydactyla, 247

Robin, 72, 95, 341
European, 149-163

Roosting, 68, 165, 167, 250, 251, 254, 256,
259, 278, 279, 286, 287, 291, 292, 436,
437, 439

Roots, Clive, Soft-billed Birds, reviewed,
226

Ross, R. K., see Cooke, F., and

Rothstein, Stephen I., Eggshell thickness
and its variation in the Cedar Wax-
wing, 469-474

Russell, Stephen M., review by, 115

Rutherford, Kim, see Goertz, John W., and

Ryder, John P., and David J. Chamber-
lain, Congenital foot abnormality in the
Ring-billed Gull, 342-344
Rylander, Michael Kent, Swallow-like be-
havior in the Rusty-margined Fly-
catcher, Myiozetetes cayanensis in
Colombia, 344
Saguinus geoffroyi, 399
Sandgrouse, 337
Sandpiper, 259, 329
Buff-breasted, 341-342
Least, 330

Spotted, 402, 420, 492

Sandstrom, George, painting by, facing
page 375

Sauer, E. G. Franz, review by, 353-355
Saurothera vielloti, 498
Sayornis nigricans, 247
phoebe, 195
Scardafella inca, 439
Schizoeaca, 317

Schlatter, R. P., see Watson, G. E., and

Schoeniophylax, 317

Schreiber, Ralph W., and Robert W. Rise-
brough, Studies of the Brown Pelican,
119-135

530

THE ILSON BULLETLX

December 1972
Vol. 84, No. 4

Schroeder. Max H.. Vesper Sparrow nests
abandoned after snow. 98-99

Schuster. S.. see Jacoby. H., and

Schiiz. Ernst. Grundriss der Vogelzugsk-
unde. 2nd Edition, reviewed. 353-355
Sciurus granatensis, 397
niger. 430
Sclerurus. 317
sp.. 382

guatemalensis. 315, 316, 420
rufigularis, 315

Seasonal distribution. 7-26. 61-63, 164—172.
198, 198-199, 250-260. 278-295. 422-
425, 489-490

Sehl. Robert H.. see Brady, Alan, and

Seibert, Henri C., Another record of a short
incubation period for the Robin, 95
Selasphorus platycercus, 69, 202
Semnornis rhamphastinus, 320
Setophaga ruticilla. 499
Sharber. X. Joseph, see Carothers. Steven
and

Sheanvater, Audubon's, 198
XewelFs Manx. 212
Shorebirds, 329-339
Shrew, 440

Least. 437. 438. 439, 441, 446
Shrike, 497
Loggerhead. 496—497
Northern, 496, 497
Sialia currucoides, 70
mexicana. 70

Siegfried. W. Roy. Ruddy Ducks colliding
with 4\-ires, 486-487
Sigmodon hispidus. 438
Sistrurus catenatus, 496
Sitta. 319

carolinensis, 69. 262
pygmaea, 70, 205
Sittasomus, 318

Sjdlander, Sverre, and Greta Agren, Re-
productive behaHor of the Common
Loon, 296-308
Skua. South Polar, 190
Skutch, Alexander F., A Naturalist in Costa
Rica, renewed. 358-359
Slater, Peter, and others, A Field Guide to

Australian Birds. Non-Passerines, re-
viewed, 112-113
Slud, Paul, review by, 358-359
Smith. Charles R., and Milo E. Richmond,
Factors influencing pellet egestion and
gastric pH in the Barn Owl, 179-186
Smith. Thomas S.. Cowbird parasitism of
estern Kingbird and Baltimore Oriole
nests, 497
Snake. 35. 411, 497
Snipe. Common, 332, 337
Jack, 337

Soper, Tony, see Arbib, Robert, and ;

see Sparks, John, and

Sora. 200-201

Sparks, John, and Tony Soper, Owls, Their
Natural and Unnatural History, re-
viewed, 360
Sparrow. 204. 341
Baird’s, 54
Chipping, 54, 64
Field, 52, 54, 57
Fox. 453, 454
Grasshopper, 54
Henslow's, 54
House, 245, 430
Le Conte’s, 54
Savannah, 48-59
Seaside, 54, 491
Sharp-tailed, 54

Song, 52, 54, 247, 450, 451, 452, 453, 454
Tree, 54, 450, 451, 452, 453
Vesper, 98-99, 173-178
White-cro^\Tied, 478
\^'hite-throated. 453, 454
Speotyto cunicularia. 95
c. floridana, 93
c. hypugaea, 93
Sphryapicus varius, 69, 320
Spindalis zena. 499
Spinus pinus, 70
psaltria, 70
tristis, 52

Spiza americana. 139, 439, 475
Spizella arborea, 54, 450
passerina, 54. 69
pusilla. 52, 54

Spofford. Sally Hoyt, review by. 505-506
Spoonbill, 259

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

531

Spring, Lowell, review by, 114^115
Squatarola, 333

squatarola, 331, 334
Squirrel, 341, 397
Fox, 430

Thirteen-lined Ground, 429, 430
Starling, 60, 62, 67-69, 71, 73
Samoan, 375

Sterna dougallii, 187, 191, 202, 342
fuscata, 18, 244
hirundo, 187, 191, 202, 342
Stettenheim, Peter, reviews by, 105, 116,
172, 178, 197, 360, 511, 512
Stevenson, Henry' M., Records of the Scarlet
Ibis and Red-breasted Blackbird in
Equador, 99; The recent history of
Bachman’s Warbler, 344-347
Stilt, Hawaiian Black-necked, 212
Stone, Charles P., Donald F. Mott, Jerome
F. Besser, and John W. De Grazio,
Bird damage to corn in the United
States in 1970, 101-105
Storer, Robert W., see Paynter, Raymond

A., Jr., and

Stork, 200

Streptopelia risoria, 131
Strix varia, 425
Sturnella neglecta, 177
tnagna, 70

Sturnus vulgaris, 60, 70
Sutton, George Miksch, High Arctic, An
Expedition to the Unspoiled North,
reviewed, 503-504
Swallow, 196, 344
Bank, 494-496
Tree, 204

Swan, Whooper, 259
Swifts, 196, 329, 337
Sylvilagus floridanus, 423, 430, 439
Sylviothorhynchus, 317
Synallaxis, 317
Syndactyla, 317
Tachycineta thalassina, 69
Taeniopygia castanotis, 329
Tait. William W., H. Malcolm Johnson, and
William I). Courser, Osprey carrying a
mammal, 341
Tamiasciurus spp., 414
Tanager, Gray-headed, .384, 398, 400, 420

Puerto Rican, 499, 500
Scarlet, 139, 140
Stripe-headed, 499
Summer, 139
Tangavius aeneus, 435
Tanner, James T., review by, 99
Tate, D. Jean, review by, 106-107
Tatum, J. B., Editor, Annual Bird Report
for southern Vancouver Island, re-
viewed, 511
Tawnywing, 392
Taxonomy, 90, 315-328
Taylor, Joseph W., Probable Bulwer’s Petrel
off Key West, Florida, 198
Taylor, Walter Kingsley, Mobbing of a Fish
Crow by passerines, 98
Tayra, 386, 397, 398

Teague, Richard D., Editor, A Manual of
Wildlife Conservation, reviewed, 510-
511

Teal, Blue- winged, 486
Common, 484
Tern, 201, 202

Common, 187-192, 201-202, 342
Least, 202

Roseate, 187-192, 201-202, 342
Sooty, 18, 244, 245

Territory, 28, 36-37, 45, 48-59, 77, 78, 84,
176, 177, 296, 297, 298, 299-300, 349,
403-407, 498

Thamnophilus punctatus, 420
Thrasher, Brown, 195
Pearly-eyed, 498
Thrush, 206, 208, 381
Oahu, 213
Hermit, 206-208
Lania, 213
Large Kauai, 212
Molokai, 212
Red-legged, 498
Small Kauai, 212
Swainson’s, 206-208, 400, 420
Wood, 139, 206, 208
Thryomanes bewickii, 173
Tiaris, 79
bicolor, 499
olivacea, 77-89

Tickell, W. L. N., see Watson, G. E., and

532

THE WILSON BULLETIN

December 1972
Vol. 84, No. 4

Tinbergen. Niko, and Hugh Falkus, Signals
for Survival, reviewed, 228
Titi. Red. 397
Titmouse. Tufted, 262, 275
Todd. W. E. Clyde, Birds of the Buffalo
Creek Region, Armstrong and Butler
Counties. Pennsylvania, reviewed, 361
Tool-using, 482-483
Totanus, 333

flavipes, 330, 331, 335
melanoleucus, 330, 331, 334
Toucan, Chestnut-mandibled, 411, 420
Keel-billed, 400, 420
Toxostoma rufum, 195
Trachyphonus darnaudi, 320
Tricholaema diadematum, 320
lachr>mosum, 320
Tringa, 333
solitaria, 334
Troglodytes aedon, 484
Tr>ngites subruficollis, 341
Turdus migratorius, 70, 95, 341
Turnstone, 337
Ruddy, 330

Tyrannus tyrannus, 139
verticalis, 497
vociferans, 69
Tyto alba, 179, 434
Ula-Ai-Hawane, 213
Upucerthia, 317
Upupa, 322, 323
epops, 322, 323
Uria aalge, 130, 243

Vaurie, Charles, Classification of the Oven-
birds < Furnariidae) , reviewed, 506-507
Veer>-, 206, 208
Veniliornis fumigatus, 320
spilogaster, 320

Vermeer, Kees. Breeding Biology of Cali-
fornia and Ring-billed Gulls: A Study
of Ecological Adaptation to the Inland
Habitat, reviewed, 227-228
Vermivora bachmanii, 344
peregrina, 139
Vestarea coccinea, 96, 213
Vireo olivaceus, 139
solitarius, 69

Vireo, Red-eyed, 130, 346

Solitary, 346
Yellow-throated, 346

Voice and vocalizations, 31, 32, 33, 35, 36,
37, 40, 41, 42, 48, 49-50, 51, 52, 53, 63,
64, 66, 67, 72, 73, 74, 80-84, 86, 96, 98,
144, 146, 173-178, 210, 296, 297, 298,
375, 379-380, 384, 387, 397, 398, 399,
400, 401, 402, 409, 410, 412, 413, 414,
415, 416, 492
Vole, 181, 182
Meadow, 491
Prairie, 179

Vulture, Turkey, 92-93, 341, 397
Warbler, 208, 341, 349
Bachman’s, 344-347
Bay-breasted, 139
Black-and-white, 346, 349, 398
Black-throated Blue, 498, 500
Canada, 400, 420
Cape May, 498, 500
Chestnut-sided, 499, 500
Grace’s, 64
Kirt land's, 347-349
Myrtle, 208, 346, 348
Orange-crowned, 346
Parula, 208, 346, 498, 500
Swainson’s, 208-210, 347
Tennessee, 139
Yellow, 139
Yellow’-throated, 346
Waterfowl, 290

Watson, G. E., J. P. Angle, P. C. Harper,
M, A. Bridge, R. P. Schlatter, W'. L. N.
Tickell, J. C. Boyd, and M. M. Boyd,
Birds of the Antarctic and Subantarc-
tic, reviewed, 504-505
Waxwing, Cedar, 469-474
W’eather, 92, 92, 93, 98, 138, 140-141, 142,
146, 149, 164, 165, 16&-170, 171, 204-
205, 231-242, 254, 278-295, 340, 424-
425, 426, 427, 434, 438. 439
Weights, 187-192, 456, 458, 459, 460-461,
476, 477, 478, 483, 484, 485, 491, 492,
492-493, 496

W'eller, Milton W'., see Fredrickson, Leigh
H., and

Wiens, John A., An Approach to the Study
of Ecological Relationships among
Grassland Birds, reviewed, 106-107

December 1972
Vol. 84, No. 4

INDEX TO VOLUME 84

533

Williams, Russ, see Jones, Thomas C., and

Willis, Edwin 0., The behavior of Plain-
brown Woodcreepers, Dendrocincla fu-
liginosa, 377-420

Willson, Mary F., Seed size preferences in
finches, 449-455
Wilson Ornithological Society
Conservation Section, 101-105, 212-222
Suggestions to authors, 513
Louis Agassiz Fuertes Award, 501
Margaret Morse Nice Award, 501
Membership, 163, 192, 210, 308, 314, 350,
474, 481
Officers, 514

Ornithological News, 100, 211, 351, 501-
502

Proceedings of the Fifty-third Annual
Meeting, 362-372
Wilsonia canadensis, 420
Wiltscho, Wolfgang, and Hiltrud Hock,
Orientation behavior of night-migrating
birds ( European Robins) during late
afternoon and early morning hours,
149-163

Witzeman, Janet L., see Demaree, Salome
R., and

Woodcock, American, 332, 337
Woodcreeper, 377

Barred, 383, 384, 398, 399, 400, 403, 420
Black-banded, 398, 400, 420
Black-striped, 380, 399, 400, 420
Buff-throated, 397, 398, 399, 400, 420
Hoffmanns’, 400, 420
Plain-brown, 377-420
Red-billed, 400, 420
Ruddy, 420
Spix’s, 400, 420

Tawny-winged, 377, 391, 412, 414, 420
Wedge-billed, 400, 420
White-chinned, 391, 400, 420
Woodhewer, 318, 322, 325, 326, 327
Woodhoopoes, 322

Woodpecker, 68, 73, 322, 324, 326, 327, 337,
381, 383

Acorn, 64, 72
Black, 30
Black-cheeked, 44
Chestnut, 397, 420
Crimson-crested, 28-47
Downy, 39, 46, 60, 62, 65-66, 71, 72, 262,
265, 493-494

Hairy, 38, 39, 40, 46, 60, 62, 64-65, 66,
71, 261-262

Ivory-billed, 28, 29, 30, 34, 35, 37, 41
Lineated, 28, 30, 31, 32, 37, 40, 41, 42,
43, 44, 45, 46
Magellanic, 29
Pale-billed, 34, 35

Pileated, 29, 30, 37, 38, 40, 41, 42, 45,
493

Puerto Rican, 498, 500
Red-bellied, 261, 275
Ruddy, 400

Wren, Bewick’s, 173, 175, 176, 177
Cactus, 484
House, 483
Xenops, 317, 319
rutilans, 315
Xiphocolaptes, 318

promeropirhynchus, 315, 316
Xiphorhynchus, 318, 389, 414
guttatus, 316, 325, 420
lachrymosus, 420
spixii, 420

Yellowlegs, Greater, 330
Lesser, 330

Yellowthroat, Greater, 348
Young, 240-248

Zenaidura macroura, 70, 430, 439
Zimmerman, Dale A., review by, 507-509;
Bird-Finding Localities in Southwest-
ern New Mexico and Southeastern
Arizona, reviewed, 511
Zimmerman, John L., and James V. Mor-
rison, Vernal testes development in
tropical-wintering Dickcissels, 475-481
Zonotrichia, 156
albicollis, 453
leucophrys gambelii, 478

This issue of The W ilson Bulletin was published on 29 December 1972.

Editor of The Wilson Bulletin
GEORGE A. HALL
Department of Chemistry
West Virginia University
Morgantown, West Virginia 26506

Editorial Advisory Board

William C. Dilger
Douglas A. James
William A. Lunk
Andrew J. Meyerriecks

Helmut C. Mueller
Robert W. Nero
Kenneth C. Parkes
Glen E. Woolfenden

Ornithological Literature Editor
Peter Stettenheim

Box 79, Plainfield, New Hampshire 03781

Suggestions to Authors

See Wilson Bulletin, 84:513, 1972 for more detailed “Suggestions to Authors.”
Manuscripts intended for publication in The Wilson Bulletin should be neatly type-
written, double-spaced, with at least one inch margins, and on one side only of good quality
white paper. Tables should be typed on separate sheets, and should be designed to fit
the normal page width, i.e., narrow and deep rather than wide and shallow. Before pre-
paring these, carefully consider whether the material is best presented in tabular form.
Follow the AOU Check-list (Fifth Edition, 1957) insofar as scientific names of United
States and Canadian birds are concerned unless a satisfactory explanation is offered for
doing otherwise. Use species names (binomials) unless specimens have actually been
handled and subsequently identified. Summaries of major papers should be brief but
quotable. Where fewer than five papers are cited, the citations may be included in the text.
All citations in “General Notes” should be included in the text. Follow carefully the style
used in this issue in listing the literature cited ; otherwise, follow the “CBE Style Manual”
(1972, AIBS) . Photographs for illustrations should be sharp, have good contrast, and be
on gloss paper. Submit prints unmounted and attach to each a brief but adequate legend.
Do not write heavily on the backs of photographs. Diagrams and line drawings should be
in black ink and their lettering large enough to permit reduction. Extensive alterations
in copy after the type has been set must be charged to the author.

Notice of Change of Address

If your address changes, notify the Society immediately. Send your complete new
address to the Treasurer, William A. Klamm, 2140 Lewis Drive, Lakewood, Ohio 44107.
He will notify the printer.

The permanent mailing address of the Wilson Ornithological Society is: c/o The
MUSEUM of Zoology, The University of Michigan, Ann Arbor, Michigan 48104. Persons
having business with any of the officers may address them at their various addresses
given on the back of the front cover, and all matters pertaining to the Bulletin should be
sent directly to the Editor.

PLAN TO ATTEND THE 1973 ANNUAL MEETING

The 1973 meeting of the Wilson Ornithological Society will be held jointly
with the Carolina Bird Club on the campus of the oldest state university, The
University of North Carolina in Chapel Hill, from Thursday, 17 May through
Sunday, 20 May. Chapel Hill is a small university town, with trees along
much of the main street. The downtown area, with its many small shops,
boutiques, and a variety of restaurants, borders the University. The campus
contains many historic buildings, gardens, an art museum, and the finest
planetarium in the nation. The nearby county seat, Hillsborough, was founded
in 1754, and has a number of homes and public buildings that were built
before the Revolution. Duke University, less than ten miles away, has a
beautiful chapel and extensive formal gardens. Tours of these and other
attractions are being arranged.

Chapel Hill is served by the Raleigh-Durham airport and four airlines
provide frequent service from a variety of cities, including direct flights to
points as distant as Los Angeles. Passenger trains still run to Raleigh, and
Chapel Hill can be reached by bus. Rooms in dormitories and the University-
owned hotel will be available for housing.

Chapel Hill lies in the Piedmont, near the edge of the Coastal Plain. The
Brown-headed Nuthatch, Blue-gray Gnatcatcher, White-eyed Vireo, Protho-
notary. Yellow-throated, Prairie, Kentucky, and Hooded Warblers and other
typical southern birds are found in the vicinity. Red-cockaded Woodpeckers
nest nearby. A field trip is being planned to the coast where one can expect
to see resident two species of ibises, ten species of herons, six species of terns.
Black Skimmers, Brown Pelicans, Willets, Wilson’s and Piping Plovers,
Avocets, stilts, and many other birds. We expect to find considerable numbers
of migrating shorebirds, and pelagic species, such as shearwaters, are not
unlikely.

The chairman of the local committee is Dr. Helmut C. Mueller, Department
of Zoology, Wilson Hall, University of North Carolina, Chapel Hill, N. C.
27514. Detailed information concerning accommodations, transportation,
field trips, and tours will be sent to members with advance registration forms.

PRELIMINARY CALL FOR PAPERS

The program chairman is Dr. Andrew 1. Berger, Department of Zoology,
University of Hawaii, Honolulu, Hawaii 96822. Members who wish to present
papers should send the following to the program chairman: (1) title of paper;
(2) name and address (institutional affiliation, if any) of author; (3) three
copies of an abstract, typed, double-spaced, not to exceed 250 words; (4)
amount of time desired; (5) special facilities needed (a blackboard, 2X2
(35 mm) and 3^/4 X 4 slide projectors will be available for all sessions).
Applications for a place on the program must be in the Program
Chairman’s hands before 1 March. All correspondence with Dr.
Berger should be by (domestic) air mail.

MCZ ERNST MAYR, ^library

3 2044 118 616 218

Date Due