Pelagic Studies of Seabirds

in the

Central and Eastern Pacific Ocean

WARREN B. KING, EDITOR

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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 158
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SMITHSONIA N CONTRIBUTION S T O ZOOLOG Y • NUMBE R 15 8

Pelagic Studies of Seabirds

in the

Central and Eastern Pacific Ocean

Warren B. King, Editor

SMITHSONIAN INSTITUTION PRESS

City of Washington

1974
ABSTRACT

King, Warren B., Editor. Pelagic Studies of Seabirds in the Central and Eastern

Pacific Ocean. Smithsonian Contributions to Zoology, number 158, 277 pages, 170

figures, 1974.—Seven papers by various authors on the pelagic distribution of several seabirds in the central and eastern Pacific Ocean based largely on the researches of the Pacific Ocean Biological Survey Program, 1963-1968. "Introduction," by Patrick J. Gould, introduces these and future papers in this series. He

discusses the methods and procedures used by the POBSP in gathering and recording

data on observations of seabirds, outlines the areas under surveillance, and provides a general account of the oceanography and marine biology of the areas under

discussion as a background to understanding the movements of seabirds in relation

to their environment. "Sooty Tern (Sterna fuscata)," by Patrick J. Gould, presents

the POBSP'S records of this most abundant tropical and subtropical Pacific species.

Its distribution at sea depends on erratic food availability, location of breeding

islands, breeding schedule, and postbreeding dispersal patterns. "Wedge-tailed

Shearwater (Puffinus pacificus)," by Warren B. King, gives data on the distribution of the northern, predominantly white-breasted and the southern, darkbreasted morphs of this species. Subtropical populations migrate extensively, for

example between the Hawaiian Islands and the Pacific coast of Middle America;

tropical populations are apparently nonmigratory. "Black-footed Albatross

(Diomedea nigripes)," by Gerald A. Sanger, discusses the distribution and frequency of sightings on a seasonal basis of this ship-following seabird, both in general terms throughout its range and in detail in certain areas, for example, the

CalCOFI study covering an eight year period oft California and Baja California.

Its winter range overlaps largely with, but lies slightly to the south of, its summer

range. "Laysan Albatross (Diomedea immutabilis)," by Gerald A. Sanger, analyzes

observations of this species and relates its seasonal distribution and abundance to

its oceanographic environment. This species is more abundant in the western and

central Pacific, whereas the Black-footed Albatross is more abundant in the central

and eastern Pacific. "The Storm Petrels (Hydrobatidae)," by Richard S. Crossin,

summarizes the POBSP'S data on eighteen species or subspecies of storm petrels

based on sightings and collected specimens. Pelagic distribution is related to

breeding cycles, location of breeding sites, and marine environment. "Red-tailed

Tropicbird (Phaethon rubricauda)," by Patrick J. Gould, Warren B. King, and

Gerald A. Sanger, discusses seasonal distribution and abundance of this species

relative to its breeding cycle. This species disperses widely from its breeding islands, for example, from the Hawaiian Islands to the Pacific coast of Middle

America. "Recoveries of Banded Laysan Albatrosses (Diomedea immutabilis) and

Black-footed Albatrosses (D. nigripes) in the Pacific Ocean," by Chandler S. Robbins and Dale W. Rice, summarizes the seasonal distribution of pelagic recoveries

of 324 banded Laysan Albatrosses and 399 banded Black-footed Albatrosses. Different age groups of each species concentrate in somewhat different areas, and, although range overlap between species is almost complete, each has its own distinctive seasonal distribution pattern.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4901. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus) .

Library of Congress Cataloging in Publication Data

Main entry under title:

Pelagic studies of seabirds in the central and eastern Pacific Ocean.

(Smithsonian contributions to zoology, no. 158)

"Seven papers by various authors . . . based largely on the researches of the Pacific Ocean

Biological Survey Program, 1963-1968."

Bibliography: p.

1. Sea birds—Pacific Ocean. 2. Pacific Ocean Biological Survey Program. I. King, Warren B.,

ed. II. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 158.

QL1.S54 no. 158 [QL694] 591'.08s [598.4'09164] 73-10383

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price $3.70
Contents

Page

INTRODUCTION, by Patrick J. Gould 1

Survey Areas 2

Methods and Procedures 4

Acknowledgments 4

SOOTY TERN {Sterna fuscata), by Patrick J. Gould 6

Introduction . 6

Behavior 8

Distribution and Abundance 13

Summary and Conclusions . 33

Appendix: Tables AC 46

WEDCE-TAILED SHEARWATER (Puffinus pacificus), by Warren B. King 53

Introduction 53

Distribution and Abundance . 56

Density and Distribution within Equatorial Currents . 56

Range of Sea Surface Temperatures and Salinities at Which Wedgetailed Shearwaters Were Observed 59

Specimen Records, Molt, and Band Recoveries 59

Discussion 62

Behavior 63

Summary 67

Appendix: Summary of Published Data on Wedge-tailed Shearwater

Distribution 92

BLACK-FOOTED ALBATROSS (Diomedea nigripes), by Gerald A. Sanger 96

Introduction 96

Distribution and Abundance 98

Specimen Records 98

Sighting Records 98

Band Return Information 103

Distribution off California and Baja California, 1951-1959 103

Abundance at Weather Station Victor 107

Analysis of Distribution . 107

General Considerations 107

Seasonal and Monthly Variations 109

Distribution in Relation to the Environment 110

Addendum 113

Appendix: Summary of Published Data on Black-footed

Albatross Distribution 126

LAYSAN ALBATROSS (Diomedea immutabilis), by Gerald A. Sanger 129

Introduction 129

Distribution and Abundance . 130

Specimen Records 130

Sighting Records 130

Annual Pelagic Cycle 134

iii
Page

Abundance at Weather Station Victor 134

Band Return Information 134

Analysis of Distribution 134

General Considerations 134

Distribution in Relation to the Environment 138

Addendum 139

Appendix: Summary of Published Data on Laysan Albatross

Distribution 152

THE STORM PETRELS (Hydrobatidae), by Richard S. Crossin 154

Introduction 154

Pelagodroma marina (Latham) 157

Oceanodroma furcata (Gmelin) 158

Oceanodroma leucorhoa leucorhoa (Vieillot) 158

Oceanodroma leucorhoa beali Emerson 165

Oceanodroma leucorhoa chapmani Berlepsch 169

Oceanodroma leucorhoa socorroensis Townsend 170

Oceanodroma homochroa (Coues) 176

Oceanodroma castro (Harcourt) 177

Oceanodroma tethys (Bonaparte) 179

Oceanodroma hornbyi (Gray) 183

Oceanodroma melania (Bonaparte) 183

Oceanodroma markhami (Salvin) 187

Oceanodroma tristrami Salvin 187

Halocyptena microsoma Coues 189

Oceanites oceanicus (Kuhl) 190

Oceanites gracilis (Elliot) 190

Fregetta grallaria (Vieillot) 190

Nesofregetta albigularis (Finsch) 193

Discussion 200

Appendix: Tables A-E 203

RED-TAILED TROPICBIRD (Phaethon rubricauda), by Patrick J. Gould,

Warren B. King, and Gerald A. Sanger 206

Introduction 206

Behavior 207

Specimen Records 210

Molt 212

Distribution and Abundance 213

Environmental Factors 216

Discussion 216

Appendix: Summary of Published Data on Red-tailed

Tropicbird Distribution 230

RECOVERIES OF BANDED LAYSAN ALBATROSSES (Diomedea immutabilis)

AND BLACK-FOOTED ALBATROSSES (£>. nigripes), by

Chandler S. Robbins and Dale W. Rice 232

Introduction 232

General Patterns of Distribution 236

Concentration Areas 238

Statistical Analysis of Geographic Range 238

Comparison of Distribution of Laysan and Black-footed Albatrosses 241

Discussion 242

LITERATURE CITED 272

iv
Pelagic Studies of Seabirds

in the

Central and Eastern Pacific Ocean

Introduction*

Patrick J. Gould

In 1963 the Smithsonian Institution initiated a

research project to study the ecology of certain

areas of the Pacific Ocean. The activities and objectives of this project, called the Pacific Ocean Biological Survey Program (POBSP) , have been summarized by Humphrey (1965). The present paper

is the first in a series summarizing at-sea bird observations made by the POBSP, although a number

of papers have already been published incorporating some POBSP at-sea observations (Amerson, 1969;

Gould, 1967; Gould and King, 1967; King, 1967;

King, 1970; King and Gould, 1967). The following

introduction is rather lengthy so that subsequent

papers herein and elsewhere may avoid needless

repetition of material relevant to all of them.

POBSP efforts were concentrated primarily on a

4ys million-square-mile area of the central Pacific

between 10°S and 30°N, and 148°W and 180°. The

birds of this area have received the greatest attention, although plants, arthropods, mammals, fishes,

reptiles, and other forms have figured in the research as well. The energies of the POBSP were divided between periodic visits to the islands of the

Leeward Hawaiian chain, the Line group, the

Patrick J. Gould, Department of Zoology, University of

Arizona, Tucson, Arizona 85721.

•Paper Number 100, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

Phoenix group, and observations in the open ocean.

Peripheral island groups such as the Tokelaus,

Marshalls, Gilberts, Wake, and the Pribilofs were

visited less frequently.

On island surveys POBSP personnel estimated the

breeding and roosting populations of each seabird

species, described the breeding status of each, made

representative collections of the plants and animals

(with special attention to vagrants), and marked

large numbers of as many species of birds and mammals as possible. In the course of this work, POBSP

personnel have banded over 1,800,000 birds of 56

species. On two atolls, Johnston and Kure, POBSP

maintained continuous surveillance. A large proportion of the birds on these islands was banded,

and uninterrupted breeding biology studies were

conducted.

Late in 1966, field work was expanded eastward

to include a survey area off southern California

and northern Baja California. Observers also accompanied many cruises (south to as far as 20°S

and east to as far as 135°W) of project EASTROPAC.

This latter project was an intensive oceanographic

investigation of the eastern tropical Pacific Ocean

by Chile, Ecuador, Mexico, Peru, and the United

States, sponsored and coordinated by the U.S. Bureau of Commercial Fisheries.

Observations at sea have been made in the central and eastern Pacific to determine the identity,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

occurrence, and abundance of seabirds. Data on

atmospheric and oceanographic conditions were

collected concurrently on some cruises to provide a

broad ecological foundation. POBSP personnel made

continuous observations, normally from sunrise to

sunset, but sometimes around the clock, on cruises

along replicate tracks and straight-line transects in

all months of the year. On most island survey

cruises, personnel made observations en route to,

from, and between the islands. Furthermore, data

on the population and breeding phenology of seabirds from island surveys added to the understanding of the distribution and densities of birds at sea.

In addition, the use of plastic leg streamers and

feather dye applied by island workers increased the

chances of assigning an island of origin to marked

birds observed or collected at sea.

SURVEY AREAS

Data were gathered systematically from the

north-central, south-central, and eastern Pacific during all months of the year. In these areas, ships followed replicate cruise tracks or concentrated their

efforts within a small area of ocean so that the

abundance and distribution of birds could be documented seasonally in great detail. Cruises also went

into peripheral areas but less regularly (Figure 1).

Although the seasonal movements of birds in these

peripheral areas cannot be shown in as much detail, the resulting data broaden the total coverage.

The north-central Pacific is defined herein as the

area between 10°N and 30°N, and between 148°W

and 180°. The only islands within this predominantly tropical oceanic area are the Hawaiian group

and Johnston Atoll. This area is within the North

Pacific Trade Wind Zone which is characterized by

mild temperatures and remarkably constant winds

from the northeast, normally between 10 and 25

knots. Anticyclonic high pressure cells move from

west to east between 35°N and 50°N and generate

the trade winds. These cells break down occasionally,, more frequently in winter than in summer, at

which times southerly and westerly winds bring

warm moist air and increased rainfall.

The north-central Pacific is within the large

North Pacific Central water mass. This is bounded

on the east by the southward flowing California

Current, the westward extension of which flows

into the North Equatorial Current. The southern

border of the North Equatorial Current forms a divergence with the Equatorial Countercurrent between 9°N and 12°N depending on the season. The

Kuroshio Current and the North Pacific Current

border the water mass on the west and north, respectively. The North Pacific Central water mass

in the Hawaiian Islands area has a high surface

salinity, up to 35.3 parts per thousand, decreasing

toward the south to 34.1 parts per thousand. Surface water temperatures range in summer from

25°C in the north (26°N) to 27°C in the south

(10°N), and in winter from 20°C in the north to

25°C in the south. A summary of north-central Pacific oceanography is found in Seckel (1962).

The flow of water through the Hawaiian Islands

is to the southwest. The large submerged bases of

the islands deflect the water and cause eddies to

form in the lee of the islands, which result in local

areas of nutrient turnover and enrichment (Sette,

1955). Seabirds are often associated with such

areas. The leeward Hawaiian Islands, Johnston

Atoll, and, to a lesser extent, the main Hawaiian

Islands, have large seabird breeding colonies. In

the spring and summer, when most of the species of

this area are breeding, high densities of seabirds

are found at sea near the islands. The oceanic areas

within 100 miles of these islands provide most of

the food resources that make possible the large colonies.

The south-central Pacific, as herein defined, extends from 10°N to 10°S and from 150°W to 180°.

Within this area are the Line Islands, the Phoenix

Islands including Howland and Baker, and the

Tokelau Islands. Northeast trade winds predominate in the northern part of this area, and southeast

trade winds predominate in the south. The narrow

zone of light, variable wind between the two trade

wind systems is called the doldrums. It is characterized by low atmospheric pressure, warm, humid

air, and more abundant rainfall than in the trade

wind zones. In January the doldrums are farthest

south, being found at 5°N at 150°W and 5°S at

170°W. In July they are found between 5°N and

9°N (Riehl, 1954:13, fig. 1.9). The belt of high

rainfall (up to 118 inches per year) moves north

and south seasonally with the doldrums.

The oceanographic conditions of the south-central Pacific are dominated by the equatorial current system which includes the easterly setting

Equatorial Countercurrent, and the westerly setting
NUMBER 158

North Equatorial and South Equatorial currents.

The boundaries of these currents change seasonally

and annually (Barkley, 1962). They are strongest in

summer as the result of stronger and more constant

trade winds. In winter the width of the currents decreases and the surface flow is weaker. In general

the North Equatorial Current is north of 9°N, the

Countercurrent lies between 4°N and 9°N, and the

South Equatorial Current is south of 4°N. Surface

temperatures range between 26° and 29°C, and surface salinities between 34.4 and 35.8 parts per thousand. For a more thorough treatment of the oceanography of the area see Barkley (1962). Ashmole

and Ashmole (1967) present an excellent review of

the general biology of birds and their food organisms in the equatorial current system.

The uninhabited islands of the south-central Pacific support large breeding seabird populations,

and pelagic areas close to islands maintain high

seabird densities. In addition, high seabird densities are normally found along the southern boundary of the Equatorial Countercurrent where local

140"E 150' WO' 170'W 160" 150" 140' 130' 120' 1K>' t00'

FIGURE 1.—Area covered by POBSP observations.

80' 70'W
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

concentrations of food organisms are caused by

convergence of that current with the South Equatorial Current (Ashmole and Ashmole, 1967:57).

The eastern Pacific is herein defined as the expanse of ocean between 35°N and 20°S, and between the American Continental coast and 135°W.

Most of the islands in this area occur within 100

miles of the coast but a few are oceanic. The surface water conditions of this area are dominated by

the California Current in the north and the Peru

Current in the south. These currents, especially the

latter, carry relatively low temperature surface waters toward the equator. This results in cooler surface temperatures in this area than are found

farther west at the same latitudes.

METHODS AND PROCEDURES

Observers maintained daily watches on ships moving through areas of interest. When two or more

observers were available, watches began before sunrise and alternated every two to four hours until

sunset. If only one observer was present, one- or

two-hour rest periods were taken occasionally. Nocturnal observations were made whenever possible.

In no case was an inexperienced observer expected

to make identifications without the supervision of

an experienced observer. However, in 1963 all observers were relatively inexperienced and for this

reason the 1963 data (8 cruises) are included only

as supplemental material in this report.

All birds seen were recorded in a daily field log.

The following information was included: time of

sighting, identification (to species or subspecies

when possible), number of birds, direction of

flight, behavior, and special comments (e.g., description, association with other species, fish activity) . When weather conditions and ship schedules

permitted, specimens were collected to verify sight

identifications and to show the range of individual

birds and, by inference, of whole populations. All

specimens are in the collection of the National

Museum of Natural History, Smithsonian Institution, Washington, D.C. Records were kept of all

position fixes and of interpolated hourly positions.

On a few cruises bathythermograph and other

oceanographic recordings were also taken. Preliminary reports were made of each trip and these,

along with the raw data obtained, are on file at the

National Museum of Natural History.

Line transects provide the basis for data collection and analysis. Densities were calculated in

birds per mile (BPM) or birds per hour (BPH) . In

this report only the former value is used. Since the

majority of observations were made at a speed of

approximately 10 knots, it is necessary only to multiply all BPM figures by 10 to get an idea of BPH

values.

In order to store and analyze data, an electronic

data processing system was designed (King, Watson, and Gould, 1967). This system can simultaneously analyze data pertaining to sighting, environment, and location and duration of observation.

The system was programmed to calculate and list

the abundance of each species. For each day of

each cruise, the total diurnal miles traveled and the

total number of a species seen were used to calculate relative densities for the entire day. All sightings were tied to the noon position of the ship.

The BPM units were plotted by month on maps,

one per month, for all data from January 1964

through April 1968. Contour lines were drawn on

the maps, connecting points of equal bird density.

In most cases a linear gradation of bird density was

assumed between any two points (i.e., noon positions) . Exceptions to this were when several positions with significantly different densities (greater

or less than the next contour increment) occurred

within a relatively small area. This may have been

because of different densities noted during a given

month or a given year, or because of different densities noted among the four years for a given

month. In such cases, the contours were drawn according to the arithmetic mean of the densities

within the area. Thus, the maps represent the

monthly average distribution and density for all

four years. All midday positions are indicated by

dots, and varying density is indicated by degrees

of shading.

ACKNOWLEDGMENTS

The following POBSP personnel and collaborators

contributed observations during the course of the

Program: Kenneth E. Amerman, A. Binion Amerson, Jr., Alan H. Anderson, J. Phillip Angle, Kenneth C. Balcomb, Frederick A. Blagden, David A.

Bratley, Robert L. Brownell, Jr., Walter Buhner,

David L. Burckhalter, Richard D. Chandler, Jane

P. Church, Roger B. Clapp, Richard S. Crossin,
NUMBER 158

Robert L. DeLong, Paul G. DuMont, Robert P.

Elliott, Charles A. Ely, John H. Fitch, Robert R.

Fleet, Douglas E. Gill, Patrick J. Gould, C. Douglas Hackman, Brian A. Harrington, Richard

Heiden, Norman N. Heryford, the late J. Vincent

Hoeman, David I. Hoff, Lawrence N. Huber,

Dayle N. Husted, Raymond R. Jillson, Cameron B.

Kepler, Warren B. King, Ralph D. Kirkpatrick,

Vernon M. Kleen, Philip N. Lehner, T. James

Lewis, Charles R. Long, James P. Ludwig, Peter

Marshall, Richard L. Maze, Robert W. McFarlane,

Richard W. Merrill, David L. Pearson, Robert L.

Pyle, Gerald A. Sanger, Ralph W. Schreiber, Philip

C. Shelton, Fred C. Sibley, Frank H. Smith, Jr.,

Dennis L. Stadel, Robert S. Standen, Robert A.

Sundell, F. Christian Thompson, Max C. Thompson, Jeffrey P. Tordoff, Michael N. Trevor, Robert

Tuxson, George E. Watson, J. Douglas Whitman,

Kenneth J. Wilz, William O. Wirtz, II, George S.

Wislocki, and Paul W. Woodward.

Reginald Creighton and Warren Minami developed and operated the automatic data processing

program. Anne K. Poulson prepared most of the

illustrations. Mae H. Esterline gave editorial advice. All work was under the direction of Philip S.

Humphrey.

All the observations to be presented were made

by POBSP personnel as well as by many other collaborators. On innumerable occasions logistic and

technical support has been generously provided by

the United States Coast Guard, the United States

Navy, the Bureau of Sport Fisheries and Wildlife

and Bureau of Commercial Fisheries of the U. S.

Department of Interior, the State of California Department of Fish and Game, the State of Hawaii

Division of Fish and Game, the Scripps Institution

of Oceanography, and the institutions and countries involved in the EASTROPAC investigations. We

are grateful to all the participants who have made

this series of papers possible.
Sooty Tern (Sterna fuscata)*

Patrick J. Gould

Introduction

SUMMARY OF PUBLISHED PELAGIC DISTRIBUTION.—

The Sooty Tern is one of the most numerous and

characteristic seabirds of the tropical and subtropical Pacific Ocean, occurring widely at sea during

all times of the year. Birds have been recorded

south to 40°S on both sides of the Pacific, and

north to southern Japan and southern Baja California. Population estimates of breeding colonies

for mid-central Pacific Islands visited by the POBSP

indicate total numbers in that area to be in excess

of 30 million birds (Table 1). Data from the eastern Pacific are fewer and less precise but indicate

many thousands of birds are present. Vast numbers

occur throughout the Atlantic and Indian Oceans

as well.

Appendix Table A is a summary of published information on Sooty Tern distribution in the Pacific Ocean. It can be seen that at-sea records are

spotty, both with respect to time of year and to

geographical area. It is apparent, however, that

Sooty Terns range widely at sea throughout the

tropical and subtropical Pacific. Morzer Bruyns

(1965) found them common to abundant in November within the Equatorial Countercurrent (6°-

8°N) across most of the Pacific. Although he recorded the largest numbers near islands and coastal

areas, he found them most consistently, on a dayto-day basis, across the large open stretch between

145°W and 115°W. King and Pyle (1957) found

these terns most abundant near islands and coastal

areas. They observed birds only sporadically along

the northern edge of the Equatorial CountercurPalrick J. Gould, Department of Zoology, University of Arizona, Tucson, Arizona 85721.

• Paper Number 68, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

rent (ca. 10° N) in November between 156°W and

120°W, and from mid-October to mid-November

between Manzanillo, Mexico, and the Marquesas

Islands. In early December they recorded Sooty

Terns every day between the Marquesas and the

Line Islands.

Distributional extremes in the south Pacific are

represented by one specimen from Rio Valdivia,

Chile, ca. 40°S (Murphy, 1936:1132) and three

records along the Wellington coast of New Zealand,

ca. 40°S (Falla, et al., 1967:165). In the north Pacific extreme records are from: the Alijos Rocks, ca.

25°N (McLellan, 1926:283), north of the leeward

Hawaiian Islands, ca. 33°N (POBSP) , and Japan,

35° N (Austin and Kuroda, 1953:450-451).

Factors influencing Sooty Tern distribution (e.g.,

feeding habits) have been studied by Ashmole

(1963a), and Ashmole and Ashmole (1967). In

the latter study they found that these terns fed

mainly on fish and squid between 2 and 8 centimeters in length. They suggest that Sooty Terns are

capable of utilizing food sources up to 700 miles

from breeding islands, and that Christmas Island

birds often feed at great distances from land during

the breeding season. Nocturnal feeding has been

documented by Morzer Bruyns and Voous (1965)

and by Gould (1967).

BREEDING PHENOLOGY.—At-sea distribution and

densities of Sooty Terns are greatly influenced by

the timing of breeding activities. A brief summary

of these activities is thus necessary to the understanding of data presented later in this paper.

Sooty Terns breed, or have bred, on almost all

islands in the tropical and subtropical Pacific between latitudes 29°N and 32°S. The timing of the

breeding cycle is apparently quite variable (Hutchinson, 1950; Chapin, 1954; Ashmole, 1963a). For

colonies within the Hawaiian Islands the breeding
NUMBER 158

TABLE 1.— Maximum number of Sooty Terns

recorded on islands in the central and eastern

Pacific

Island

CENTRAL PACIFIC

Hawaiian-Leeward

Kure

Midway

Number

48,000

353,000

Pearl and Hermes Reef 40,110

Lisianski

Laysan

Gardner Pinnacles

French Frigate Shoals

Necker

N'ihoa

Moku Manu

Manana

Johnston Atoll

Line Islands

Palmyra

Fanning

Christmas

Jan is

Maiden

Starbuck

Caroline

Phoenix Islands

Canton

Enderbury

McKean

Phoenix

Birnie

Hull

Howland

Wake

Marshall Islands

Taongi

Bikar

Taka

Eniwetok

Ailinginae

Jaluit

EASTERN PACIFIC

Isabel

Revilla Gigedos

Clipperton

IslasFrailesdelSur

Cocos

Culpepper

1,000,000

2,000,000

1,000

250,000

50,000

100,000

20,000

200,000

600,000

750,000

thousands

15,000,000

1,900,000

10,000

3,000,000

500,000

100

400,000

250,000

250,000

1300

3,000,000

375,000

1,750,000

20,000

7300

60,000

16,000

5,000

30

thousands

thousands

2,000

200

30

thousands

San Felix large numbers

Source

POBSP

••

"

*•

"

••

"

"

Amerson, 1969:23

Amerson, 1969:37

Amerson, 1969:50-51

Amerson, 1969:116

Amerson, 1969:141

Amerson, 1969:196

McLellan, 1926:283

Gifford, 1913:20

Stager, 1964:365

Wetmore, 1965:457

Hundley, 1962:114

Leveque, 1964a:39-40

Millie, 1963:566

cycle is annual and regular, the dates of peak laying generally falling within the same four-week

period in most years. Dates of egg-laying, however,

occur progressively later on the chain from Oahu

northwestward to Kure Atoll. On Manana, close to

Oahu, the peak of egg-laying occurs during the last

week in March or the first week in April. On Kure,

at the northwestern end of the leeward Hawaiian

chain, egg-laying begins in May.

On Johnston Atoll the peak of egg-laying comes

in the middle of March. Birds first appear over the

island at night, nearly three months prior to the

time of laying. Numbers swirling over the island at

night build up gradually to the time of egg-laying,

when birds are present throughout the day as well.

Maximum numbers on, or over, the island coincide

with the hatching peak in the middle of April.

Most fledging takes place in June. Fledglings generally leave the island by the first of August, and

most adults leave by the end of August. The Johnston population is composed of approximately

300,000 breeding birds, and a roughly equivalent

number of subadults and nonbreeding adults. The

relative proportion of subadults and nonbreeders

to breeding adults increases from June to the end

of the cycle. Sooty Terns are virtually absent from

Johnston Atoll from mid-September to the end of

December (Shdton, in. prep.).

In the Line island group, the breeding cycle appears to be semiannual. Birds that successfully rear

a chick breed again in 12 months, but those that

fail nest again in only 6 months. The egg-laying

peaks are in December and June. This cycle has

been documented on Christmas Island by Ashmole

(1965) and appears to hold true for other islands

of that chain as well, although there may be exceptions or complicating factors in some populations.

The timing of the breeding cycles of Sooty Terns

on Wake Island, and in the Phoenix, Marshall, and

Gilbert chains, and on islands in the eastern Pacific is not understood. Some islands may have two

or more individual colonies, each breeding at different times. Many may have a non-annual cycle.

A discussion of breeding cycles and associated problems may be found in Ashmole (1963a).

ACKNOWLEDGMENTS.—I would like to give special

credit to Warren B. King and Gerald A. Sanger who

have worked with me in analyzing all at-sea bird

data obtained by the POBSP and Philip C. Shelton

who has provided data and comments on the population dynamics of Sooty Terns on breeding islands.

Charles A. Sklar plotted the majority of the noon

positions on the maps, and Helen H. Quinn typed

the final draft.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 2.—Sample size of POBSP Sooty Tern

observations

Observation

Sightings

Birds

1964 1965 1966 Total

1,547

19,070

1,665

20,738

782

11,287

3,994

51,095

I am indebted to William B. Robertson, Jr., and

George E. Watson for their critical reading of the

manuscript and their many helpful suggestions.

The many POBSP personnel and various cooperators without whose observations and help this paper

could not have been written have already been acknowledged in the Introduction.

Behavior

In this section all data, except when specifically

stated otherwise, were collected within the following parameters: (1) at sea over 50 miles from land,

(2) within approximately three-fourths mile of the

ship, (3) in the north-central Pacific Ocean, (4)

from 1964 through 1966, (5) from diurnal observations (sunrise to sunset). These parameters have

been purposely chosen. Observations near land

have been excluded because it was often impossible

to get a clear idea of what was happening when

birds were "too numerous to count": birds seem to

be everywhere, moving in all directions, joining

groups, leaving groups, flying high, flying low, etc.

In such situations it was impossible to follow individual birds or flocks, or to understand behavioral

patterns and interactions. The parameter of threefourths mile from the ship was chosen because, although Sooty Tern flocks could be seen at greater

distances, they could not be counted accurately, nor

could they be observed well enough for behavioral

studies beyond that distance. Moreover, single birds

cannot be observed at greater distances so that the

inclusion of distant birds would over-emphasize eflects created by flocking. The north-central Pacific

was the most uniformly covered large area, and had

by far the largest number of observations made

within it; also, Sooty Terns breeding in this area

have an annual rather than semiannual cycle. Only

the years 1964, 1965, and 1966 were included because of the spottiness of coverage in the northcentral Pacific during other years. Within these

parameters a total of 51,095 birds in 3994 sightings

was recorded (Table 2).

At this point it seems advisable to define a few

special terms which will be used in the following

discussion. A "sighting" refers to a single bird or

two or more birds acting as a unit. A "flock" is considered to be the association of five or more individuals, "BPS" (birds/sighting) is a good index of

the gregariousness or flocking tendency of a species.

A "mixed" flock or sighting is one that contains

more than one species, while a "pure" flock or

sighting is one which contains only one species.

"Searching" birds are those actively hunting for

food, while "traveling" birds appear to be moving

towards a specific goal.

FEEDING.—Ashmole and Ashmole (1967) have

discussed the feeding ecology of Sooty Terns, considering particularly the kind of food taken and

how it is captured. Our observations are in general

agreement with theirs. Sooty Terns, searching for

food, generally remain from 10 to 20 meters above

the water surface. When the food source appears,

they descend, simultaneously, and begin wheeling

rapidly and erratically in circles. At this time there

does not appear to be any coordination between

individuals within a flock, although small groups

may act in unison for short periods. When the food

source descends, the flock rises to its original position and follows until the food returns to the surface or until it disappears. In a feeding flock working over a large area, terns in one section may be

flying high, following locally deep food, while those

in another section may be low and actively feeding.

"Air dipping" and "contact dipping" (Ashmole

and Ashmole, 1967) appear to be the preferred

feeding techniques, although "plunge to surface" is

frequently used if the food source remains near but

under the surface. The latter technique has been

recorded only once in the Sooty Tern literature

(Watson and Lashley, 1915). In POBSP observations, the "plunge to surface," although actually

causing the water to splash up and obscure the

bird momentarily, is never powerful, nor is it made

from any great height. It never results in complete

submergence of the bird, nor do the wings ever appear to cease beating. The feet do not seem to be

utilized.

FLOCKING.—Sooty Terns were recorded in sightings of from 1 to 3000 individuals. The overall BPS

ratio was 13, the highest value for any seabird
NUMBER 158

TABLE 3.—Percent of sightings and numbers of

Sooty Terns in different sighting classes

Birds per

sighting

1

2

3

4

5

6

7

8

9

10+

1-4

5-55

56-105

106+

Percent of all sightings

1964

36

20

9

4

3

3

1

1

1

22

69

25

4

2

1965

15

21

9

5

4

2

1

1

1

21

70

?4

4

2

1966

1?

21

10

6

4

3

1

?

1

20

69

3

1

mean

35

21

9

5

4

2

1

1

1

21

70

25

4

2

Percent of all birds

1964

3

3

2

0.5

86.5

9

37

27

26

1965

1

3

2

2

?

1

1

1

1

84

10

3">

27

28

1966

?

3

2

2

86

9

in

16

45

mean

3

3

2

2

1

1

1

1

1

85

10

15

24

31

species regularly feeding over 50 miles from land.

Although 90 percent of all individuals were found

in flocks, flocks comprised only 30 percent of the

sightings in all years. Indeed, sightings of single

birds (35 percent) far outnumbered sightings of

any other group size. Singles and groups of two ac120

100

80

60

40

20

counted for 56 percent of all sightings (Table 3).

The POBSP data agree with Ashmole and Ashmole's (1967:97) statement that "most tropical sea

birds depend partly or entirely on schools of predatory fish (mainly tunas) to drive their prey close to

the surface and so make it available." Although

Sooty Terns have been observed feeding in the

absence of predatory fish, many actively feeding

flocks were directly associated with such schools.

The sudden, and often relatively short-term, appearance of feeding tuna apparently places a premium on the ability of Sooty Terns to join feeding

flocks containing other species. Seventy-seven percent of all Sooty Terns, and 24 percent of all Sooty

Tern sightings, were associated with one or more

seabird species (Table 4). Almost all species normally occurring in the area were involved, but the

degree of their involvement was related to their

gregariousness and their status within the area. For

example, 70.6 percent of all mixed flocks containing

Sooty Terns also contained Wedge-tailed Shearwaters (Puffinus pacificus). Conversely, King (p.

65, herein) found that 77 percent of all mixed

flocks containing Wedge-tails contained Sooty

Terns. Wedge-tails are the next most abundant

species in the area and have a high BPS ratio (King,

p. 64 herein). On the other hand, Sooty ShearwaV

VV —

V

VVi, . ^

VV

V

VV

VV

rfV

VV

VV

£/ > r"

^

FIGURE 2.—Schematic representation of a mixed feeding flock showing the general stratification

of selected species and their general pattern of movement while feeding.
10

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 4.—Percent of association of Sooty Terns zoith other seabird species,

1964-1966

Species

Puffinus pacificus

Pterodroma externa ... .

Gygis alba

Pterodroma nigripennis..

Fregata minor

Puffinus griseus

Anous stolidus

Puffinus puffinus

Sula sula

Bulweria bulwerii

Pterodroma neglecta ... .

Sula dactylatra

Puffinus nativitatis

Phaethon rubricauda ...

Oceanodroma leucorhoa .

Sterna lunata

Stercorarius pomarinus ..

Puffinus carneipes

Pterodroma alba

Pterodroma phaeopygia..

Stercorarius longicaudus.

Fregata oriel

Pterodroma hypoleuca ..

Phaethon lepturus

Puffinus bulleri

Puffinus Iherminieri

Puffinus tenuirostris ... .

Pterodroma inexpectata .

Sula leucogaster

Catharacta species

Anous tenuirostris

All sightings

16.4

7.4

4.8

S.9

3.3

1.1

1.0

1.0

1.0

0.7

0.7

0.6

0.5

0.5

0.4

0.4

0.3

0.2

0.2

0.2

0.2

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

Mixed Sightings

70.6

32.0

20.8

16.8

14.2

4.5

4.4

4.3

4.1

2.8

2.8

2.5

2.3

2.2

1.8

1.5

1.2

1.0

1.0

0.6

0.6

0.4

0.4

0.4

0.4

0.3

0.3

0.3

0.2

0.2

0.2

General at-sea status

abundant most of the year

common summer and fall

uncommon throughout year

common summer and fall

uncommon throughout year

abundant spring and fall migrant

rare throughout year

uncommon spring, summer and fall

common winter

uncommon spring, summer and fall

uncommon throughout year

common winter

uncommon spring, summer and fall

common throughout year

abundant winter

uncommon spring, summer, and fall

uncommon spring and fall migrant

rare spring and fall migrant

rare throughout year

rare summer and fall

rare spring and fall migrant

rare throughout year

rare throughout year

uncommon throughout year

rare spring and fall migrant

rare throughout year

abundant fall migrant

uncommon spring and fall migrant

rare throughout year

rare spring and fall migrant

rare throughout year

ters (Puffinus griseus) were abundant at certain

seasons and had a high BPS ratio, but were found in

•only 4.5 percent of all mixed flocks containing

Sooty Terns. This difference between two highly

flocking and abundant species is explained by the

fact that Wedge-tails are resident in the area while

Sooty Shearwaters are primarily passing through

on migration and rarely stop to feed.

The association of Sooty Terns with other seabird species appears to be mainly one of a common

interest in the same food source. While within

mixed feeding flocks, Sooty Terns maintain a definite spatial position in accord with the feeding

abilities and techniques of all species involved.

(Figure 2).

We have a number of records of Sooty Terns being harrassed by Pomarine Jaegers (Stercorarius

pomarinus), Long-tailed Jaegers (Stercorarius

longicaudus), Great Frigatebirds (Fregata minor),

and Lesser Frigatebirds (Fregata ariel).

The largest Sooty Tern flock ever recorded by the

POBSP occurred on 20 May 1966, some 200 miles

south of Oahu. On this day a feeding flock of

4300+ birds, including Wedge-tailed Shearwaters,

Pale-footed Shearwaters (Puffinus carneipes),

Christmas Shearwaters (Puffinus nativitatis), Manx

Shearwaters (Puffinus puffinus), Bulwer's Petrels

(Bulweria bulwerii), Great Frigatebirds, Brown

Noddy Terns (Anous stolidus), Black Noddy

Terns (Anous tenuirostris), and 3000+ Sooty Terns

was observed. The birds were concentrated over

eight to twelve Fin-backed Whales (Balaenoptera

physalus) and about 200 porpoises. The fringes of

the flock stretched for approximately three miles.
NUMBER 158 11

Although we have no direct information on how

much time individual birds spend feeding, searching, or traveling, the fact that the great majority of

all birds observed were in mixed flocks, usually an

indication of current or recent feeding, suggests

that the greatest percent of their time is spent feeding or actively searching for food, with the former

outweighing the latter. There is certainly a tendency for Sooty Terns to occur in larger flocks

while feeding (Table 5). Our observations indicate that mixed, nonfeeding groups are composed

mostly of searching birds. Pure, nonfeeding groups

may be either searching or traveling; the activity

cannot always be determined. Pure flocks of up to

140 birds and mixed flocks of up to 125 birds have

been recorded traveling. Single birds and small

groups have been observed both searching (moving

slowly, dropping occasionally to the water surface,

and investigating other birds in the water), and

traveling. The distinction between searching and

traveling, however, sometimes breaks down (traveling birds may stop to feed if the stimulus is strong

enough), or it is sometimes even meaningless

(many traveling birds may be headed for a distant

feeding flock).

It was difficult to obtain direct evidence on how

flocks form, how long they are maintained, and

what happens when the food source being utilized

disappears. In discussing the feeding behavior of

Brown Noddies and Sooty Terns, Watson (1908:

193) wrote: "The birds feed singly or in groups,

usually in groups. The group may be composed of

both noddies and sooties and may contain sometimes as many as 50 to 100 individuals. All during

the day groups of noddies and sooties may be seen

at work. As the minnows cease to jump above the

surface of the water, the group disbands and scatters in every direction. An instant later, as an attack is made upon the minnows in some other locality, the birds immediately rush there and renew

their feeding." POBSP observations include a number of isolated observations documenting various

stages in this process. The following entries, with

annotations enclosed in brackets, are abstracted

from the POBSP original daily log sheets. They are

arranged in a subjective order from "searching"

birds through "feeding" birds (including birds traveling toward already formed feeding flocks), to

flocks "breaking up."

TABLE 5.—Total Sooty Tern sightings and numbers

in mixed and pure, feeding and nonfeeding, situations

Situation

Mixed

Feeding ..

Nonfeeding

Pure

Feeding ..

Nonfeeding

Mixed

Feeding . .

Nonfeeding

Pure

Feeding ..

Nonfeeding

Mixed

Feeding ..

Nonfeeding

Pure

Feeding ..

Nonfeeding

1964 1965 1966 Mean

Percentage of sightings

14

8

2

14

10

2

14

8

5

14

9

3

75 74 74 74

PerCe«»=><*** nt total numtv»r*

58

16

6

18

51

24

33

3

54

24

3

19

BPS

48

30

22

3

69

8

10

13

ratio

70

16

28

3

59

18

6

18

53

25

28

3

SEARCHING

05 March 1964. 0700 Hours. 16°48'N, 169°06'W.

3 ST [Sooty Terns], [flying at] ca. 30-40 feet. One bird

separated and circled a dead albatross in the water, then

joined other two.

08 March 1964. 1103 Hours. 14°50'N, 169°40/W.

1 ST. Investigated downed [dead in water] albatross and

continued NE.

07 June 1964. 1441 Hours. 18°11'N, 166°10'W.

2 ST. One shot [ship circled to retrieve downed bird]. At

1450 Hrs. 12 ST circled and looked over downed bird.

02 April 1964. 1612 Hours. 20°41'N, 159°ITW.

2 ST flying SW joined and drded with 6 ST circling at

1615 Hrs., then all 8 departed SW. No feeding was observed.

04 July 1964. 0600 Hours. 16°40'N, 169° 18^.

Hock of 26 ST and 1 WTS [Wedge-tailed Shearwater].

Original group of 14 joined by 6 then 6 more. Birds

were not actively feeding but flew around as if food

were near by.

FEEDING

10 May 1964. 1900 Hours. 15°04'N, 170°37'W.

30 ± ST. Very high, maybe 1000 feet up. Some of them

seem to be gathering to move on, but then descend sud-
12

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

denly as feeding flock. Big fish, probably tuna 5' or more

long and some about 3' long jump at least 6' clear of

water.

22 July 1964. 1110 Hours. 18°46'N, 150°59'W.

Feeding flock containing 90± ST, 2 WTS, 8 JFP [Juan

Fernandez Petrel, Pterodroma externa], 1 W'T [White

Tern, Gygis alba]. Three separate groups joined up,

each with about 30 ST.

11 March 1964. 1656 Hours. Near Johnston Atoll.

Feeding flock in formation started with 4 birds on their

way south starting to circle and dive. Within minutes, 8

other Sooties came in, seemingly from all directions to

join them. No fish action noted and feeding over area of

about 14 mile length (or diameter). [Ship continuing to

move at ca. 8 knots.] 1700 Hours: 25+ ST moving low

towards above flock. 1702 Hours: 40 ± ST at ca. 50' moving to join above? 1702 Hours: 10 ± ST low, moving

right under above. 1705 Hours: 2 ST moving low toward

above flock.

18 May 1965. 1500 Hours. 20°14'N, 154°02'W.

Feeding flock of 50 ST, 8 WTS, and two unidentified

shearwaters or petrels. Original flock of 20 joined by 10

individuals and then by group of 25 or so.

06 September 1964. 1645 Hours. 17°34'N, 167°03'W.

30 ± ST, 8 WTS, 1 GFB [Great Frigatebird]. Feeding

over fish jumping out of water. 1640 Hours: 13 ST at 50'

going to above flock. 1646 Hours: 10 ST, 1 GFB, circling.

1648 Hours: 11 ST flying towards 1645 flock. 1656 Hours:

8 ST flying towards 1645 flock.

12 May 1964. 0715 Hours. 15°30'N, 171°33'W.

Flock of 55 ±1 ST and 3 WTS. Actively feeding. Large

tuna-type fish jumping under flock. Flock was originally

only of about 30 birds but soon increased to final number. At one point flock broke up into two groups, one of

about 25, the other about 30. One group was soaring

around high on port side of ship, the other was low,

flying on starboard.

BREAKING UP

11 April 1964. 0825 Hours. 15°07'N, 171°24'W.

16±2 ST feeding. 3 birds left flock as we approached.

18 July 1964. 0905 Hours. 21°48'N, 162°27'W.

Flock of 50 ±10 ST, 6 WTS, 2 BFB [Blue-faced Booby,

Sula dactylatra], 1 WT, 1 GFB, feeding—but breaking

up into small groups. 091") Hours: flock of 30 ST, 10

WTS, 1 RFB [Red-footed Booby, Sula sula], 2 CIS

[Christmas Shearwater], and 1 WT, undoubtedly was

once part of last flock; we saw birds from last flock

join this one.

13 May 1964. 1705 Hours. 16°25'N, 17O°51'W.

17 ST, 5 to 50' [above water]. Not feeding, but apparently looking for food source—group tended to split up

but constant movement was to E[ast].

Most shearwaters and gadfly petrels tend to sit

on the water in either compact or loose aggregations after heavy feeding. It is well known, however, that Sooty Terns are incapable of spending

long periods in such a fashion (Watson and Lashley, 1915:39-41). Sooty Terns do, however, alight

occasionally at sea, either on a floating object or

actually on the water. All such POBSP records are

listed below. Omitting the bird knocked down by

shot and the three sitting on turtles or flotsam,

0.3 percent of all sightings and 0.16 percent of all

individuals recorded by the POBSP were on the

water. These estimates, however, are undoubtedly

low since most birds tend to rise before they can

be detected.

19 August 1965. 0920 Hours. 13°53'N, 173°01'W.

One Sooty Tern was knocked down by shotgun blast and

sat in the water for 12 minutes then flew at the approach

of the ship.

23 October 1965. 0940 Hours. 01°16'S, 173°38'W.

One adult and one immature Sooty together on water,

immature being fed by the adult.

23 October 1965. 1730 Hours. 02°00'S, 172°52'W.

One adult, one immature were collected while sitting on

the water.

10 November 1965. 17°5rN, 164°09'W.

In a feeding flock containing ca. 15 Sooty Terns (at least

four being immature), one adult and one young were

noted as "on water together."

September-October 1964.

"Three different times during the trip I saw Sooty Terns

sitting on the water. A total of 6 birds were observed,

always in twos. Each pair contained an immature bird

and an adult. In one case both the immature and the

adult were observed on the water. In the other two cases

just the immature was on the water with the adult hovering overhead. In all cases the birds flew off as the ship

approached. I never saw them land on the water so I

can't say how long they stayed there. The longest I observed them was about 5 seconds." (POBSP, Robert

Standen)

12 May 1965. 0744 Hours. 16°44'N, 162°16'W.

10 and 25 Sooty Terns. "Two separate flocks sitting on

the water. They were gliding around and at first appeared to be Wedge-tails from their flight pattern. Birds

were flying and then sitting down again. They were not

feeding."

01 September 1967. 0930 Hours. 01°44'N, 98°04'W.

75 ± ST. All adults, seemed to have fresh plumage. Most

circling high 200'±, some close to water. About 8 of

them were sitting on the water.

14 June 1967. 1425 Hours. (Atlantic Ocean) 12°42'N,

81°06'W.

2 adult ST sitting on water with wings closed—quite

happy 10-15 seconds that I saw. (POBSP, Richard Chandler)

February 1968.

"On February 13 both shipboard observers saw a single

flock of 22 adult Sooty Terns resting on the water about

10 miles south of Johnston. When first seen all were together on the water spaced two to six feet apart. As the

ship aproached two or three birds rose off the water and
NUMBER 158

began hovering over the remaining 20. These remained

on the water for at least another minute before the ship

scared them into flight. The time lapse between the

lust sighting and flushing was about two minutes, but it

was obvious that the birds had been there quite a bit

longer." (POBSI\ Brian Harrington)

07 July 1967. 0955 Hours. 18°35'N, 104°53'W.

One Sooty Tern sitting on a turtle.

10 July 1967. 1433 Hours. 17°O8'N, 101°05'VV.

One Sooty Tern standing on head of turtle.

18 August 1966. 1713 Hours. 32°06'N, 163°42'W.

One adult Sooty Tern sitting on fish ball [float].

DISCUSSION.—Sooty Terns occur over the entire

pelagic area of the north-central Pacific. They are

distributed primarily as singles and small groups

interspersed with a few small flocks and even fewer

large flocks. Over 90 percent of all individuals,

however, are found in flocks. The degree of flocking is probably greatest in areas of food abundance.

Single birds and small groups generally appear to

be searching. Their flight is usually slow, indirect,

and often high above the water. They frequently

drop to just above the surface, apparently investigating possible food items. When available food is

spotted the bird or birds descend and begin feeding. This change in behavior pattern is distinct and

easily recognizable to the human eye. Other birds

within visual range probably can detect and

identify the new pattern and are attracted to it.

Birds heading towards a feeding flock fly in a relatively fast and direct manner distinct from that of

searching birds. It is possible that this type of flight

may provide a clue to other birds which were not

aware of the newly formed feeding flock. Similar

behavioral differences are also found in other flocking seabirds (e.g., Wedge-tailed Shearwaters) and it

seems probable that Sooty Terns could recognize

such behavioral changes in other species and act

accordingly.

As a feeding flock grows it becomes visible to

more distant birds. The eventual size of the flock

would thus be controlled, primarily, by the length

of time that food is available. The total number

of terns within range of the food supply would,

however, have a restricting effect, since distant

birds might be hard put to detect the presence of

food and to reach it before it disappeared. When

the food source disappears, Sooty Terns rise high

into the air and disperse, either by fragmenting

into two or more smaller groups each going in a

separate direction, or by all going in the same

direction but becoming widely separated. Subsequent fragmentation of groups or continued separation of individuals may eventually result in the

dispersal of all birds over the ocean as individuals.

If another food source is discovered before a flock

has fragmented or separated completely, the group,

whatever size it has been reduced to, becomes the

nucleus of a new feeding flock. As the length of

time between feedings increases, sightings of single

birds should increase since flocks would have had

more time to disperse. The relative frequency of

sightings of single birds, as opposed to sightings of

groups, should thus provide an estimate of food

availability and tuna school density in a given

pelagic area.

Distribution and Abundance

Figures 17-28 (pp. 34-45) summarize monthly

POBSP Sooty Tern sightings in the Pacific Ocean.

They attempt to show gross distributional patterns

and in most cases tend to de-emphasize local or

short-term variations. Only at-sea sightings are included, although these may include sightings

within a few miles of land. Sightings cover the

period January 1964 through April 1968, and contour lines are drawn without regard to year. Densities are recorded in BPM units.

NORTH-CENTRAL PACIFIC.—Sooty Terns are present in the north-central Pacific throughout the

year. At least one bird was recorded during 74.5

percent of all days of observation from 1964

through 1966. Only during January 1964, December 1965, and August 1966, were birds seen on

fewer than 50 percent of all observation days

(Figure 3).

Densities throughout the year ranged from a low

of 0.0 BPM to a high of 54.5 BPM. Densities greater

than 10.0 BPM were uncommon and, with one exception, always occurred within 50 miles of land.

This exception, however, was the second highest

density ever recorded within the study area (27.1

BPM). The highest density figure, 54.5 BPM, is somewhat unreliable since observations on that day

covered only four miles and lasted somewhat less

than one hour (Table 6).

With the fledging of chicks in August, Sooty

Tern numbers near islands decrease markedly.

Lowest maximum densities near the Hawaiian Islands and Johnston Atoll occurred in October
14

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100

90

80

70

60

t

8 50

I

40

30

20

10

Average

J FMAMJJASON D

63 59 83 115 77 99 66 76 58 72 79 77

Days of Observation

FIGURE 3.—Percent of observation days on which one or more Sooty Terns were recorded in the

north-central Pacific during 1964-1966.

(Table 7). In the area as a whole, however, densities were lowest in November and December,

even though densities near the Hawaiian Islands

and Johnston Atoll increased slightly. Densities

over 50 miles from land began increasing in June

with an influx of newly fledged birds. From June

through November, immature birds became increasingly abundant and wide-spread throughout

the north Pacific. We have a few records which

indicate that newly fledged birds accompany their

parents when they leave the breeding colony, i.e.,

the six sightings of an adult and immature sitting

on the water listed in the behavior section. The

record of an adult feeding an immature over 100

miles from land on 23 October 1965 is certainly

conclusive.

Increasing densities in January and February,

particularly near breeding islands, were the result

of birds returning to these islands for the next

breeding season. From September through December, and especially during September and October,

densities in areas over 50 miles from land were

generally greater than those within 50 miles. This

was particularly noticeable in two widely separated

areas where at-sea densities reached as high as 9.0

BPM. The first area was 200-300 miles west-southwest of Oahu. This is apparently a rich feeding

area favored by many species of seabirds, particu-
NUMBER 158

15

TABLE 6.—Date and location of all Sooty Tern

densities of 10.0 or greater BPM recorded within

the north-central Pacific, 1964-1966

(Observation = within 50 miles of "Location")

TABLE 7.—Maximum Sooty Tern densities (BPM)

in the north-central Pacific

Density

(BPM)

10.0

10.2

10.4

10.9

11.0

11.5

11.8

12.4

12.8

12.9

14.5

16.1

23.2

26.9

27.1

54.5

Location

Oahu

Johnston Atoll

Oahu

Oahu

French Frigate Shoals

Oahu

Laysan

Johnston Atoll

Oahu

Johnston A toil

Laysan

Johnston Atoll

Lisianski

Oahu

at-sea, 17°54'N,

158°48'W

Oahu

Date

6 Jun

5 Jun

5 Jul

5 Jun

17 Jun

4 May

20 Jun

13 Apr

13 Jul

31 Jan

5 Aug

5 Jul

14 Jul

31 May

20 May

2 Jul

66

66

66

64

64

65

66

65

64

66

65

65

65

65

66

65

Miles of

observation

28

141

23

73

108

40

39

117

51

22

80

127

33

104

117

4

larly those breeding in the leeward and main

Hawaiian Islands. The second was 700-800 miles

south-southeast of Oahu. This area may be occupied by birds from more southerly breeding localities (e.g., Line Islands) as suggested by King

(1970:54), although it is somewhat north of the

Equatorial Gountercurrent which Ashmole and

Ashmole (1967:66) considered a likely feeding

ground for Christmas Island birds.

During this winter period, a strange pattern of

occurrence was found in the area between 50 and

300 miles southwest of Johnston Atoll. During the

day, Sooty Tern densities decreased through November and December to a low of 0.0 BPM in

January, and then increased again in February.

Nocturnal observations in the same area, on the

other hand, revealed few terns in November and

December, but large numbers in January and

February. This occurred in all three successive

years of our investigations in this area (Table 8).

Nocturnal counts were primarily of birds heard

near the ship. Densities listed in Table 8 are conservative, particularly with respect to diurnal sightings, since birds can be seen at greater distances

than they can be heard. Although Sooty Terns are

often attracted to the ship's lights, particularly on

Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Near Near 50+ miles

Hawaiian I. Johnston Atoll from land

4.8

6.7

6.9

5.6

26.9

11.8

54.5

14.5

1.0

0.1

1.0

1.5

12.9

5.0

7.9

12.4

7.2

10.2

16.1

2.8

3.5

02

1.3

2.3

4.9

6.7

8.0

6.4

27.1

3.9

9.4

8.0

9.0

7.1

2.6

5.0

TABLE 8.—Winter Sooty Tern densities 50-300

miles southwest of Johnston Atoll, 1963—1967

Year

1963-1964

1964-1965

1965-1966

1966-1967

Mean

1963-1964

1964-1965

1965-1966

1966-1967

Mean

Nov Dec Jan Feb

Birds per 100 miles of diurnal

observations

23 1 0 1

1 17 0 0

32

3

14

1

10

8

0

0

0

8

41

20

Birds per 100 miles of nocturnal

observations

2 0* 2# 0#

13

9

1

2

» 2

0

5

3

62

5

32

30

23

47

40

•Months in which less than 100 miles of observations were

made.

stormy nights, they are still difficult to observe. The

chances of counting the same birds twice are much

greater at night than during the day. In this case,

however, most of the nocturnal birds appeared to

be traveling in a specific direction, rather than

circling the ship, thus reducing the chances of

duplicate recording.

Two additional features were also apparent.

First, there was a definite nocturnal activity cycle.

Sooty Terns were first heard about an hour after

sunset and increased in numbers to maximum
16

6

5

r

u

s

IE

i

3

2

1

-

-

-

-

- m

I

i

m

11

n

1

I

I

i

1

1

I

1

sXXS

I

i

i

1i

I

i

I

!

i

I

i

g j JAN. - FEB.

[ | NOV. - DEC.

SUNRISE-0617-0790

SUNSET -1749 1912

I

I

1

I

I

i

w

I

1100 19-20 20 21 21-22 22-23 23-24 24-01 01-02 02 03 03-04 04-0 m

1

5 OJ-0 14 0600

to to

190 0 HOURLY PERIODS 0700

FIGURE 4.—Nocturnal abundance cycle for Sooty Terns from

50 to 300 miles southwest of Johnston Atoll during 1963-

1967.

densities between 2200 and 0200 hours. Numbers

then declined to zero about an hour before sunrise (Figure 4). This was especially noticeable in

January and February, but was also true in November and December. Second, a majority of the

nocturnal terns heard south and west of Johnston

Atoll was apparently moving north and northwest

towards the atoll, or towards other breeding islands

farther north and northwest in the Leewards. The

number moving in southerly directions was almost

nil. Unfortunately, adequate records for nocturnal

direction of movement are available only for January and February of 1966 (Figure 5).

A similar nocturnal-diurnal pattern occurred

on the breeding island at Johnston Atoll. Lowest

numbers of Sooty Terns occurred in October and

November when only a few individuals and small

flocks visited the island briefly and irregularly.

These were probably wandering pelagic birds that

happened to pass the island and were temporarily

attracted to it, primarily at night or just at dusk.

They rarely landed on the island. Potential breeding birds were first observed at the island between

late November (1964—1965) and late December

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

(1963). In 1966 flocks first occurred near the island

during the first two weeks of December. These

birds first gathered offshore at night, then began

settling on the island in small groups. These groups

grew until much of the land was occupied. This

development took several weeks, generally lasting

through mid-February, during which no more than

a few wandering birds were over the island during

the day. All of those on the ground at night left

shortly before dawn. Finally, the birds began to

stay on the island during the day, after which

courtship and egg laying followed in quick succession (POBSP, Philip Shelton). Sooty Terns occurred

within 50 miles of the atoll in fair numbers during

the day throughout this period, especially in January and February.

Several causative and perhaps interrelated factors

have been suggested to explain the day-night differences in January-February densities. Although

none of these explanations is complete in itself,

one or more may provide part of the answer.

1. At this time of year Johnston birds are known

to avoid land during the day, and to be attracted

to it at night. Birds may react toward ships in the

same way, thus avoiding diurnal detection at sea.

2. Sooty Tern migration may be rapid and nocturnal. Birds may "pile up" in preferred feeding

areas during the day and complete the last leg of

their migration in a single night.

3. Most Sooty Terns may remain within 50 miles

of Johnston during the day even though they avoid

close approach to land.

4. The area southwest of Johnston is probably

very poor in available food. Terns leaving Johnston before dawn may pass through the area before

sunrise and return through the area after sunset. A

lack of food would deter them from pausing within

the area.

5. The January and February nocturnal aggregations may represent prebreeding swirls from

Johnston Atoll. W. B. Robertson of the National

Park Service (pers. comm.) informs me that early

prebreeding swirls at the Tortugas often do not

seem to be oriented toward the colony site. Instead

they may occur anywhere around the general area

and, quite possibly, well outside the area.

Although egg-laying commences in late February

on Johnston Atoll, at-sea densities of Sooty Terns

continued to increase through March in the surrounding waters. This was consistent with a con-
NUMBER 158 17

169°3O'

16°45'

•Jr

^ 9

Johnston

A Atoll

WIND

Total °h for 271 bird*

. = 24OO position

Avg. 16 knots

5 1

2 7

8 1

FIGURE 5.—Nocturnal flight directions for Sooty Terns southwest of Johnston Atoll during January-February 1966. (Arrows indicate direction in percent, numbers indicate sample size.)

tinued increase of birds on the island. Maximum

island and at-sea densities were generally maintained through July, although some terns began

leaving Johnston Atoll in early June.

During the northern summer, densities in the

1-5 BPM range were common over 50 miles from

land, and ranged from 0.0-8.0 BPM. Densities up

to at least 26.9 BPM were recorded within 50 miles

of the breeding islands at this time. The largest

single concentration of Sooty Terns recorded by

the POBSP north of the equator, however, occurred

on 20 May 1966, at 17°54'N, 158°48'W, some 200

miles south of Oahu.

Repeated observations to the northeast of the

Hawaiian Islands illustrate the seasonal expansion

and contraction of Sooty Tern distributional limits

in the north central Pacific (Figure 6). During the

nonbreeding season, in particular November-December, birds were rarely recorded over 100 miles

northeast of Hawaii. With the return of the birds

and the beginning of nesting activities (MarchApril), distributional limits were extended, and

by July-August, when chicks were being fed, birds

were found up to 600 miles northeast of Hawaii.

The northernmost sighting in the central Pacific

was of two adult-plumaged birds recorded at 33°

06'N, 164°08/W on 9 August 1966.

To summarize, at-sea densities of Sooty Terns in

the north-central Pacific Ocean are reflections of

breeding island densities. The annual cycle is represented by a fairly smooth curve, with lowest density in November-December and highest density in

June (Figure 7).

To clarify the distributional patterns of birds
18

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

160'

FIGURE 6.—Seasonal variation in the distributional limits of

Sooty Terns northeast of the Hawaiian Islands.

within the central Pacific, the POBSP initiated an

intensive banding program. Since March 1963, over

1,200,000 Sooty Terns have been banded. These

include birds from nearly all major breeding colonies on the main and leeward Hawaiian, Line,

and Phoenix (including Howland) island groups,

as well as on Johnston and Wake atolls. Greatest

numbers have been banded on Johnston (over

250,000), Laysan (over 130,000), and Howland (over

100,000). Colored vinyl leg streamers were also

placed on birds from Johnston (orange) and Howland (blue). A special effort was made on all POBSP

field trips, both at sea and on islands, to look for

streamered and banded birds. In addition, a program of intensive advertisement of our efforts,

including appeals for help in locating banded and

streamered birds, was made throughout the inhabitated areas of the tropical and subtropical

Pacific.

As of December 1968, we have processed 1027

interisland and at-sea recoveries and 339 at-sea

streamer sightings of Sooty Terns. These represent

WEST

170° 160°

M A M J

MONTHS, 1964-1966

N

FICURE 7.—Annual at-sea density cycle for Sooty Terns in the north-central Pacific.
NUMBER 158 19

CENTRAL PACIFIC OCEAN

\SLANOjs

»NUKUNONOt

mryyD IQO 20ST 355 «oo

FIGURE 8.—Distribution of banded and streamered Sooty Tern sightings.
20

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

110° IJ0° 130* 140° ISO* 160* 170° t»0°

130° 110° 110* 100* 90* to' 70*

FIGURE 9.—Interisland movements of Sooty Terns banded in the north-central Pacific.

less than 0.01 percent of the total number banded.

Over one-half of the interisland recoveries represent elapsed times greater than one year and 68

percent were short-distance movements within

island groups (e.g., between Kure and Midway

atolls). It is thus too early to attempt a detailed

analysis of the banding data. Since some of these

records provide insight into the confusing pelagic

dispersal of Sooty Terns, however, a brief summary

is presented here.

Two hundred and thirty-five orange-streamered

birds have been observed at sea (Appendix Table

B). All were in the central Pacific north of 11°N.

Similarly, orange-streamered birds have been seen

and handled on most islands in the same area, but

none have been observed on islands farther south.

No blue-streamered birds have been recorded north

of 02°N. Ninety-six percent of all orange-streamered birds were recorded during the breeding season (March-August). Of these, 70 percent were

within fifty miles of Johnston Atoll even though

over 80 percent of all observation time in that general area was spent over 50 miles from the atoll.

During the breeding season, four streamered birds

were sighted over 275 miles from Johnston (one

adult in August, 278 miles SE; one immature in

August, 287 miles SW; one adult in August, 392

miles SW; and one adult in March, 392 miles SW).

We have 10 records of 13 streamered birds feeding

at distances up to 225 miles from Johnston (AprilJune). Recently fledged streamered birds have been

found over 100 miles from the breeding colony only

during August (3 birds: 180, 226, and 287 miles

SW). During the nonbreeding season (September-
NUMBER 158 21

February), three of a total of eight orange-streamer

sightings were over 50 miles from Johnston (two

in September, 394 and 481 miles NE; and one in

December, 299 miles ENE). The remaining five

were found in September, January, and February,

and were probably late departing or early arriving

birds.

Twelve banded birds (10 from Johnston, 1 from

Oahu, and 1 from Laysan) have been recovered at

sea (Appendix Table C). As with the streamer

sightings, all were from the central Pacific north of

11°N. All but three were recovered over 100 miles

from the site of banding. One immature banded on

Laysan in August was recovered four months later

1170 miles to the southeast. Another, banded on

Johnston in July, was recovered four months later

460 miles to the southwest. Figure 8 is a spatial

summary of all at-sea streamer sightings and band

recoveries.

The above data suggest that during the breeding

season, Johnston-based Sooty Terns may forage up

to 300 miles from the breeding colony, but that the

greatest numbers remain within 50 miles. At the

end of the breeding season, adults and immatures

disperse widely at sea and many disappear from the

north-central Pacific. Four late fall and early winter

orange-streamer sightings show dispersal from Johnston of birds to the northeast (three) and to the

southwest (one). The one late fall record from

Laysan was to the southeast.

Figure 9 summarizes interisland movements of

Sooty Terns involving the main and leeward

Hawaiian, Johnston, and Wake islands. Unfortunately, few of these recoveries involve known status

birds (e.g., breeding, nonbreeding), or elapsed times

less than the length of one breeding season. It is

thus impossible to connect the islands of banding

and recovery with meaningful directional arrows.

TABLE 9.—Interisland Sooty Tern movements occurring within six months of

banding

Banding and recovery

locations

Hawaiian banded :

Hawaiians

Leeward banded:

Leewards

Johnston

Japan

Philippines

Johnston banded:

Leewards

Japan

Philippines

Wake banded:

Johnston

Carolines

Japan

Phoenix banded:

Phoenix

Leewards

Line banded:

Leewards

North Pacific banded:

North Pacific

Western Pacific . . .

South Pacific banded:

South Pacific

North Pacific

Recovery month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2

-

1

_

2

1

-

3

!•

9

1

-

16

_

-

-

2

1 + 1

1 - 3

1

5 9 28 -

-11 4

-3- 2

1

1 1

•Banded as locals or immatures.
22

Table 9 summarizes all recoveries made less than

6 months after time of banding. It is apparent,

however, that there is considerable interisland

movement between islands of the north-central

Pacific. Birds banded on Johnston regularly occur

on Wake and in the main and leeward Hawaiians

and vice versa. Similarly, much movement occurs

between islands of the south-central Pacific. A certain amount of interchange between these two

areas has been recorded, but our eighteen records

probably exaggerate its amount. The lack of

orange-streamer sightings in the southern islands,

and blue-streamer sightings in the northern islands,

particularly on frequently surveyed islands such as

Howland and Johnston, indicate that some of the

north-south band recoveries may be due to misread

band numbers. Unfortunately, none of the northsouth band recoveries have been substantiated by

the collection of the bird or the removal of its

band. The relatively large number of these northsouth records, however, indicate that such movements may occur.

Twenty-eight poBSP-banded birds have been reSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

covered in the western Pacific. Ten were reported

as being associated with typhoons, and three with

stormy weather. Another three were reported exhausted when found. By comparing the dates and

localities of recapture with typhoon and tropical

storm tracks in the western Pacific (Joint Typhoon

Warning Center, 1965, 1966, 1967; DeAngelis, 1968,

1969), a total of 20 can be directly associated with

typhoons and tropical storms (Table 10). This

indicates that at least a majority of banded birds

recovered in Japan and the Philippines was driven

there by storms. By analyzing the origin and pathway of these storms, it is possible to make assumptions as to the area these Sooty Terns were carried

from and thus determine at least part of their nonbreeding range.

Typhoons in the northwest Pacific appear to

originate in the area between 5°N and 20°N, and

between 170°E and the Philippines. The United

States Naval Oceanographic Office (1964:42) describes the typhoon tracks in this area as follows:

. . . the greater number of typhoons conform to the usual

tropical cyclone track pattern and move initially westward or

100 E

20

10

FIGURE 10.—Tracks of typhoons which blew banded Sooty Terns to the western Pacific.
NUMBER 158 23

TABLE 10.—Sooty Tern recoveries from the western Pacific

Recovery location

Leyte, Philippines

(ca. 11°N, 126°E)

Southern Honshu, Japan

(34°4O'N, 135°56'E)

Honshu, Japan

(37°4O'N, 139°J0'E)

Southern Leyte, Philippines

(ca. 10°N, 125°E)

Masbate, Philippines

(ca. 12°N, 122°E)

Isabela, Philippines

(prob. 1O°35'N, 124°E)

Near Ticao, Philippines

(12°3O'N, 123°5O'E)

Tarlac, Luzon, Philippines

(ca. 15°S0'N, 125°E)

Southern Honshu, Japan

(34°5O'N, 138°20'E)

Honshu, Japan

(35°I9'N, 139°22'E)

Honshu, Japan

(35°00'N, 1S8°2O'E)

Southern Luzon, Philippines

(ca. 15°N, 121°E)

Eastern Samar, Philippines

(12°N, 125°20'E)

Mawmawan, Philippines

(ca. 10°N, 124°E)

Philippines

(no location specilicd)

Southern Leyte, Philippines

(ca. 10°N, 126°E)

Toledo City, Philippines

(ca. 10°20'N, 124°E)

Negros Island, Philippines

(09°10'N, 123°10'E)

Southeast Luzon, Philippines

(13°3O'N, 123°10'E)

Northern Luzon, Philippines

(ca. 15°40'N, 121 °E)

Southeast Luzon, Philippines

(ca. 13°2O'N, 123°2O'E)

Southern Luzon, Philippines

(ca. 14°15'N, 121°15'E)

Eastern Samar, Philippines

(ll°40'N, 125°20'E)

Honshu, Japan

(35°20'N, 139°35'E)

Shikoku, Japan

(ca. 33°3O'N, 133°3O'E)

Shikoku, Japan

(ca. 33°3O'N, 133°3O'E)

Shikoku, Japan

(ca. 33°3O'N, 133°3O'E)

Negros, Philippines

(ca. 10°N, 123°E)

Date Remarks

Banding

location Date Age

7 Mar 65 tropical storm Vera off Leyte on 7 Mar 65; bird

exhausted by "typhoon" winds

7 Aug 65 typhoon Jean moved north over Kyushu 5 Aug

65; birds "typhoon-driven"

18 Sjp 65 typhoon Trix over eastern Honshu on 17 Sep 65

before typhoon Faye passed about 250 mi NE of islands

17 Dec 65 on 23 Nov 65

before as above; bird exhausted

22 Dec 63

before no typhoons or tropical storms since Faye passed

10 Mar 66 250 mi NE on 23 Nov 65

20 Mar 66 as above

20 May 66 typhoon Irma over SW Luzon on 18 May 66; bird

in wake of typhoon Irma

25 Sep 66 typhoon Ida passed over Honshu on 24 Sep 66;

birds "typhoon-driven"

25 Sep 66 as above; no recapture data

25 Sep 66 as above; bird "typhoon-driven"

4 Jan 67 no typhoons or tropical storms since Pamela on

27 Dec 66; raining

11 Jan 67 as above; bird exhausted

4 Feb 67 as above; bird in heavy rain in front of "typhoon"

? Feb 67 as above; bird "storm-driven"

3 Mar 67 typhoon Sally passed over central islands on 3

Mar 67

4 Mar 67 as above; bird at height of typhoon Sally

4 Mar 67 as above; male bird

6 Mar 67 as above; bird weak

17 Oct 67 typhoon Carla passed over northern Luzon on

17 Oct 67; after typhoon Trining

3 Xov 67 typhoon Emma passed over southern Luzon on

3 Nov 67; stormy

4 Nov 67 as above; "typhoon-driven"

4 Nov 67 as above; bird after typhoon Welling

26 Apr 68 cannot be accounted for by typhoons or tropical

storms

3 Jul 68 last stages of typhoon Lucy passed about 250 miles

S of Shikoku on 2 Jul 68

28 Jul 68 typhoon Mary passed over Shikoku on 28 Jul 68

29 Jul 68 as above

25 Nov 68 typhoon Nina passed over Negros on 24 Nov 68

Johnston 8 May 64 local

Wake 1 May 65 nestling

Johnston II May 65 local

Laysan 9 Aug 65 adult

Johnston 26 May 65 local

Johnston 28 May 65 local

Johnston 7 Jun 65 local

Midway 27 Jul 65 nestling

Johnston 22 Mar 66 adult

Midway 12 Jun 66 breeding

adult

Lisianski 17 Jun 66 adult

Johnston 13 Mar 66 adult

McKean 19 Jul 64 adult

Johnston 15 Jun 66 adult

Wake 15 Jun 66 nestling

Howland 19 Jul 66 adult

Christmas 12 Mar 66 nestling

McKean 21 Sep 65 local

Howland 16 Aug 66 local

Midway 27 Jul 65 nestling

Johnston 14 Jun 67 local

Midway 22 Jul 64 local

Midway 8 Sep 64 immature

Laysan 6 Aug 65 adult

Johnston 8 Mar 64 adult

Johnston 20 May 68 local

Johnston 2 May 66 adult

Midway 13 Jun 66 adult
24 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

west-northwestward from the source region. Those that reach

higher latitudes, normally north of 15°N, have a tendency to

recurve and move in a northeasterly direction over or to the

east of Japan. A considerable number, however, travel almost

due westward and eventually dissipate over the Philippines

or the China coast. At the height of the typhoon season over

the western Pacific (July through October) the majority of

these storms passes to the north of the Philippines moving

toward Taiwan, the Japanese Islands, and the China coast.

. . . During the so-called slack season (December through

February) many continue on a westward course and enter

the South China Sea.

Figure 10 shows the typhoon and tropical storm

tracks that can be associated with POBSP band recoveries in the western Pacific. All originate in, or

immediately southeast of, the Philippine Sea, and

all pass through it. Thus, the Philippine Sea must

constitute at least part of the nonbreeding range

of north-central Pacific Sooty Terns. The only

typhoon that can be associated with birds from the

Line and Phoenix islands was Sally in 1967. This

was the most southern of all Sooty Tern-bearing

typhoons, and had the southwesternmost point of

origin. No northern birds were reported as a result

of this storm. Lane (1967), however, reports the

recovery of a Sooty Tern originally banded on

Roach Islet, Lord Howe, New South Wales, 28

November 1962, from southern Leyte, Philippines,

on 4 March 1967. This is the same recovery date and

area as two of our recoveries associated with

typhoon Sally. This suggests that the nonbreeding

ranges of south-central and north-central Pacific

terns are essentially allopatric. Unfortunately,

literature records from this area are scarce. Brinkley (in Bourne and Radford, 1961) recorded seven

birds in August at 22°N, 124°E. In late October,

Morzer Bruyns (1965) recorded two groups of 50

birds each at approximately 9°N, 131°E, three

groups of 40, 10, and 3, near 7°N, 142°E, and

possibly two birds at 7°N, 150°E. He did not, however, find any terns in late October or early November near the Palau, western Caroline, or

Marshall islands. Records for the timing of the

breeding cycle in the Carolines are lacking so that

we do not know whether the birds he observed

were of that population.

EQUATORIAL CENTRAL PACIFIC.—Sverdrup, et al.

(1942:709) point out that the Equatorial Countercurrent is remarkably well developed in the Pacific

Ocean, present at all seasons, lies always in the

northern hemisphere, and is farther north in the

northern summer. Barkley (1962:5) shows that the

borders of this current generally lie between 4°-

5°N and 9°-10°N. North of the Countercurrent is

the westward flowing North Equatorial Current,

while south is the westward flowing South Equatorial Current. Data from the Carnegie Expedition

(Sverdrup, et al., 1942:711) state that

within the Equatorial Countercurrent descending motion

takes place at the southern boundary and ascending motion

at the northern boundary, and between the Equator and the

Countercurrent descending motion takes place at the boundary of the Countercurrent and ascending motion at the Equator. Thus, two cells appear with divergence at the northern

limit of the Counlercurrent and at the Equator, and with a

convergence at the southern boundary of the Countercurrent.

Ashmole and Ashmole (1967) have discussed the

distribution of seabirds with relation to the equatorial currents in the central Pacific. They make

several points which are relevant to the following

discussion: (1) Most tropical seabirds depend, at

least in part, on schools of fish to drive their prey

close to the surface. (2) Upwelling waters are generally rich in nutrients and zooplankton. (3) As

water moves away from divergence areas, phosphate

and zooplankton decrease and forage animals increase. (4) In the equatorial current area fish schools

are generally most abundant within the Countercurrent. They (1967:107) conclude that "localized

concentrations of plankton and nekton produced

by convergence and sinking of surface waters at

'fronts' which have been suggested as exerting important effects on the distribution of surface schools

of tunas in the open ocean, may also provide favorable feeding grounds for many oceanic birds."

Other authors, among them King and Pyle (1957)

and Morzer Bruyns (1965) have shown some of the

effects of oceanic currents in the central Pacific on

the density and distribution of seabirds.

From January 1964 through 1967 twenty cruises

were made by the POBSP across the equatorial currents (0°-13°N) between 148°W and 180°. Surface

water temperatures ranged between 25.5° and

30.6°C with the majority falling between 27.0°

and 29.5°C. Barkley (1962) presented averaged

temperatures for this area of 27° to 28°C, and

averaged salinities of 34.30 to 35.40 ppt.

FIGURE 11.—Sooty Tern density in relation to equatorial currents in the central Pacific between longitudes 148°W and

180°.
I

T:

70

J 110

a 130

J -

Q 210

230

250
H

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WEST LONSITUDE

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NORTH LATITUDE

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 [J] SEPTEMBER

[|]| OCTOBER

• NOVEMBER

I 12 11 10 9" 8" T 6" 5" 4" 3" 2" 1" 0"

NORTH LATITUDE
NUMBER 158 27

Figure 11 shows latitudinal variation of Sooty

Tern densities plotted against the depth of the

20°C isotherm for five 1966 cruises. The slope of

this isotherm can be used as a rough indication of

the position of major currents. Figure 12 presents

density data for all 20 cruises on a seasonal and

monthly basis, while Figure 13 shows a composite

of all 1965-1966 densities and an average density

per each degree of latitude.

Ignoring areas under the immediate influence of

islands (i.e., areas within 50 miles of Howland,

Christmas, and Palmyra) Sooty Terns are more

abundant within the Equatorial Countercurrent

than in either the North or South Equatorial currents. The South Equatorial Current has greater

Sooty Tern densities than the North Equatorial

Current, possibly because of the more direct influence of islands and/or the convergence at its

northern border. It is within the convergence area

that greatest over-all densities have been recorded

(Figure 13). Our data thus support the assumptions reached by the Ashmoles. Our data also suggest, but are too few to prove, a seasonal shift in

high densities from the convergence area (4°N5°N) in the fall, to the northern Countercurrent

area (7°N-9°N) in the spring. Intervening seasons

are intermediate, with greatest winter densities recorded in the area of 5°N to 6°N, and greatest summer densities in the area of 6°N to 7°N. The more

northerly position of high density in spring and

summer might be explained if many of the terns

in the Countercurrent area were part of the northern islands' (e.g., Johnston Atoll) breeding population. Unfortunately, there have been no band

returns or color-streamer sightings from this area.

It seems quite probable that Sooty Terns in the

equatorial currents are from islands in both the

north and south central Pacific and that the influence of each area varies with the season and

with the local breeding schedule.

Within the equatorial currents lie a number of

islands, most of which support large Sooty Tern

colonies. These include the Line Islands: Kingman

Reef (06°24'N), Palmyra (05°52'N), Washington

(04°43'N), Fanning (03°52'N), Christmas (01°51'N)

and Jarvis (00°23'S), and two islands often considFIGI'RE 12.—Sooty Tern density across the equatorial central

Pacific.

ered part of the Phoenix group: Howland (00°

45'N), and Baker (00°13'N). The latter two islands

have been intensively investigated by the POBSP

with respect both to island and at-sea bird populations.

The POBSP observations show a very close relationship between the breeding schedule and densities on Howland Island, and at-sea densities

within a 100-mile radius of it (Figure 14). Peak

at-sea densities occurred during each of the two

major egg-laying periods in 1966-1967. The large

numbers of birds at sea during September and

October 1965 while island populations were at their

lowest are thought to be due to birds from other

populations moving into or through the area. The

only evidence for this was the collection within

the area in October of three immature and one

adult Sooty Terns originally banded on Hull Island three to eight weeks earlier. At-sea collections

and sightings of banded or color-tagged birds during all other surveys were of Howland-marked

birds.

SOUTH-CENTRAL PACIFIC.—Pelagic observations

were conducted on 13 POBSP surveys to the southcentral Pacific from March 1964 through February

1967. During most of these trips many days were

spent in the Phoenix Islands. Twelve trips continued south to eastern Samoa and one to the Fiji

Islands. Two general cruise tracks were used, one

by way of the Tokelaus and Swain's Island, and

the other by way of Rakahanga and the Danger

Islands. Table 11 summarizes the distribution and

abundance of Sooty Terns during these trips. The

area of coverage was too restricted, and the timing

of observations too unevenly spaced to allow more

than the following brief summary.

Sooty Terns were abundant at all times of the

year on and around the Phoenix Islands. Highest

densities were recorded from September through

February, particularly October to December. Annual at-sea abundance cycles in this area, however,

cannot be evaluated because of the variation in

the timing of breeding cycles between the islands,

and because of the nearness of these islands to one

another and our inability to assign island origins

to birds observed at sea. These factors prevented

relating a daily at-sea density to a particular island.

Also May-September records are few while OctoberApril records are numerous. South of the Phoenix

Islands these terns became progressively less abun-
28

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

8* 7* 6* 5* 4*

NORTH LATITUDE

Daily Observations

Avsrage Density

12* 11* 10* 9* 8*

NORTH LATITUDE

FIGURE 13.—Summary of Sooty Tern densities across the equatorial central Pacific during 1965-

1966.
NUMBER 158 29

HOWLAND ISLAND

0

5 UJ

UJ -

1

I U O

(C >

mo

i^5 If S

3 I

i n n

•M'-L L

iOCCS ta.*W— ill —

525 -5 5 s * III

I 8'

K j Diurnal density

^ Nocturnal density

Average Miles of Observations per Month

Diurnal = 690

Nocturnal 479

FIGURE 14.—Correlation of at-sea densities (within 100 miles o£ Howland) of Sooty Terns with

the breeding schedule and population fluctuations of Howland Island.

dant, being seen on fewer days as well as in smaller

numbers.

Movements of banded and streamered birds from

this area are summarized in Table 10, Appendix

Tables B, C, Figures 8, 10, and 15. These records

are discussed under the section dealing with northcentral Pacific banding results, and under the discussion of Howland Island in the equatorial central

Pacific.

EASTERN PACIFIC.—Surveys in the eastern Pacific

north of 30° N have been conducted from December 1966 through April 1968 off southern California and northern Baja California, generally on a

semimonthly basis. South of 30°N surveys have

been made in cooperation with EASTROPAC. POBSP

personnel recorded observations during nine

cruises. Three of these ran concurrently in JanuaryMarch 1967, one in June-July 1967, two concurrently in August-September 1967, one in OctoberDecember 1967, and two concurrently in FebruaryApril 1968. The survey pattern was based on

north-south cruise tracks along specific longitudes.

Two of these tracks (119°W, 112°W) were followed

five times each; two (105°W, 98°W) were followed
30 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

•c
NUMBER 158 31

TABLE 11.—Distribution and occurrence of Sooty Terns within 100 miles of southcentral Pacific islands from March 1964 through February 1967

Area

Days

observed

(No.)

Days

recorded

(No.)

Days

recorded

Average

density

(BPM)

Range of

density

(BPM)

Months of observations

Phoenix Islands

Tokelau I

Rakahanga I.

Danger I

Swains I. .... .

Wallis I

£. Samoa

Horn I

Fiji I

Total/average .

51 51 100 3.9 0.02-34.6 all except Jun and Aug

20 17 85 0.7 0.0-3.4 all except Jan and May

2 1-0. 3 0.0-0.6 Jun

3 3 - 0.3 0.03-0.7 Mar and Jun

17 13 76 0.1 0.0-1.0 all except Jan, May, and Dec

2 2-0. 6 0.04-1.2 Feb

15 4 27 0.1 0.0-1.1 all except Jan, May, Sep. and Dec

2 2-0. 1 0.02-0.2 Feb

3 3-0. 1 0.01-0.3 Feb

11? % 8? T? 0.0-34.6 all months

four times each; one (92°W) was followed twice;

and three (126° W, 96°W, 88°W) were followed

once.

Sooty Terns have never been recorded north of

26°N in the eastern Pacific, and POBSP personnel

have not found them north of 22°N. Our data

from the eastern Pacific are not complete enough

to show much in the way of annual trends. Observations, for example, do not exist for May and

December, and are minimal for January and April.

Figures 17 through 28 summarize all POBSP records

for the eastern Pacific (pp. 34-45).

Sooty Terns were generally common (1-5 BPM)

in the Equatorial Countercurrent, particularly

west of 110°W to 126°W, and along the Mexican

coast from Acapulco north to the Gulf of California. Densities greater than 5 BPM were recorded on

TABLE 12.—Date and location of Sooty Tern

densities (BPM) greater than 5.0 in the eastern

Pacific

Date

2 Feb 67

22 Feb 67

5 Jun 67

7 Jul 67

5 Sep67

9

22

17

18

7

Noon position

°38'N,119

°18'N,109

°56'N,102

°38'N,104

°42'N,112

°00'W

°17'\V

°55'W

°48'W

°06'W

Area

Equatorial Countercurrent

mouth of Gulf of

California

coast of Mexico

coast of Mexico

Equatorial Countercurrent

Density

8.8

7.8

18.5

6.1

9.0

only five days (Table 12). These were also either

along the Mexican coast or in the Equatorial

Countercurrent. We have never recorded Sooty

Terns north of 15°46'N except at the mouth of the

Gulf of California where birds have been seen

north of 21°49'N. Anthony (1898), Kaeding (1905),

Gifford (1913), and McLellen (1926) recorded Sooty

Terns as breeding on die Revilla Gigedo Islands

(19°N, 111°W) in the northern spring. However,

during four days of POBSP observations within 150

miles of these islands (11 February, 20-21 March, 15

September) no Sooty Terns were seen. Brattstrom

and Howell (1956) did not record this species there

in March or November.

Only in February and March were observations

made south of 20°S. During these two months Sooty

Terns were common (1-5 BPM^ in southern waters

from 5°S to 14°S in the more western area (119°W126°W), with scattered birds recorded to 19°48'S

at 121°3rW. In August, Sooty Terns were likewise

common from 5°S to 10°S, the southern limit of

our observations.

Equatorial currents were probably as influential

on Sooty Tern distribution and abundance in the

eastern Pacific as they are in the central Pacific.

There are, however, several important differences

between the two areas. These appear to be significant in their effect on Sooty Terns. Wyrtki (1966,

n.d.) characterizes the Equatorial Countercurrents

east of 120°W as clearly developed from May to December and absent from February through April.

From May to December, west of 110°W, its bound-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

11" 10* 9" 7"

NORTH LATITUDE

112*through 119*

NORTH LATITUDE

88* through 106*

FIGURE 16.—Sooty Tern density across the Equatorial Countcrcurrent in the eastern Pacific.

aries vary between 4°N to 6°N and 8°N to 12°N,

while east of 110°W there is a southward shift so

that at the end point the boundaries lie south of

4°N and 10°N. From February to April surface water flow is to the west and northwest between the

South Equatorial and North Equatorial currents.

Figure 16 summarizes data from our nine cruises

across the Equatorial Countercurrent. The distribution and abundance of Sooty Terns appeared to

change in response to changes in the Countercurrent as described by Wyrtki. In both seasons Sooty

Terns were found across the entire current area.

Density centers, however, differed markedly. During

the season when the Countercurrent was not present, high densities were found only west of 110°W

(the two highest densities were at 119°W) and only

north of 9°N. (If the Countercurrent were developed, this position would be at its northern boundary which is contrary to what would be expected

from the Ashmoles' discussion and from the observed distribution of central Pacific terns.) Eastern

Pacific distribution, however, may be the result of

the west and northwest flow developed through

this area at this time of year. During the season

when the Countercurrent was clearly developed,

high densities were mainly at the convergence

along the southern border of the Countercurrent

(ca. 5°N). It is also pertinent to note that during

both seasons highest densities were recorded west

of 112° W where the currents are generally stronger

and well developed.

Sooty Terns appear to be present throughout the

year in the eastern Pacific. Our fragmentary data

suggest that during the spring (February-April)

greatest numbers occur west of 110°W, while during the fall (August-November) high densities also

occur over much of the area east of 110°W. This

would be in accord with fall nesting on the Galapagos Islands and Clipperton Atoll, and with a

westward dispersal at the conclusion of the breeding season. Such an hypothesis for breeding stations

is consistent with central Pacific Sooty Tern distribution patterns. We would expect to see colorstreamered birds if central Pacific birds were moving into the area. Unfortunately, only a few birds

have been collected so that the chance of recover-
NUMBER 158 33

ing banded birds has been exceedingly small. It is,

however, possible that birds from French Polynesia enter the area. This is suggested by the large

numbers of birds found from 5°S to 15°S, and

from 119°W to 126°W in February and March. All

traveling flocks observed at this time were heading

east.

Summary and Conclusions

Sooty Terns are abundant and widely dispersed

throughout the tropical and subtropical Pacific

Ocean. The perimeter of peripheral breeding localities marks the normal limits of their pelagic dispersal. Within this area they may be found over

almost any part of the ocean at any time of the

year. The occurrence of Sooty Terns beyond the

normal limits of their range is generally the result

of major climatic disturbances, such as typhoons

and cyclones in the western Pacific, and possibly

of fluctuations in oceanic currents and water

masses. The regularity of stragglers in such areas

as Japan is due to the regularity of these disturbances.

Sooty Tern densities fluctuate widely in both

space and time. Factors affecting these densities

are complicated, often interacting, and sometimes

obscured by the presence of two or more populations which are indistinguishable in the field. The

following factors are educed in this investigation,

but this list is not exhaustive:

Food Availability: Over a greater part of the

ocean, Sooty Terns are generally few and scattered,

with occasional high densities shifting from area

to area in response to an erratic food supply. In

such areas, tern densities vary directly with the

length of time food is available. In areas where

food is regularly available (e.g., the Equatorial

Countercurrent), tern densities are uniformly

higher.

Breeding Island Proximity: During the breeding

season Sooty Terns are island-oriented; highest

densities generally occur within 25 miles of breeding islands. Individual breeding birds, however,

may forage up to 300 miles at sea away from breeding colonies.

Breeding Schedule: At-sea densities vary directly

with the breeding cycles on nearby islands; highest

at-sea numbers occur at the peaks of the nesting

seasons. In the north-central Pacific (HawaiianLeewards and Johnston), the at-sea density and

island nesting cycles are annual and regular. In

the south-central Pacific (Line and Phoenix islands), breeding is semiannual or irregular, and

at-sea densities may be high at any time depending

upon the status of nearby breeding colonies.

Post-breeding Dispersal: During the nonbreeding

season birds may be rare or absent in some parts

of the Pacific. After the young fledge, Sooty Terns

become ocean-oriented, and densities near islands

decrease; birds appear to remain in the general

area of the breeding islands for up to a month before moving to nonbreeding areas. Central Pacific

Sooty Terns of all age groups disperse westward;

many north-central birds reach the Philippine Sea,

which constitutes at least part of their nonbreeding

range. Nonbreeding ranges, as well as breeding

ranges, of north<entral and south-central Pacific

Sooty Terns appear to be allopatric.
34

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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NUMBER 158 35

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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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NUMBER 158 37

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40 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER'158 41

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42 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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NUMBER 158 43

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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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NUMBER 158 45

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"
Appendix

TABLE A.—Summary of published data on Sooty Tern distribution

Location Date Remarks Source

EAST-CENTRAL PACIFIC

Roca Alijos

Coast of Mexico

ca. 20°N

Between Manzanilla

and the Marquesas I.

Roca Partida

Oneal Rock

Isabel I.

Clipperton I.

Panama

7°46'S, 120°W

7°09'N, 81°08'W

7°N, 131°W

7°N, 125°W

7°N, 116°W

7°N, 101°W

7°N, 93°W

Pedro Gonzales I.

7°N, 82°3O'W

3°N, 93°30'W

2°50'N, 120°W

SOUTHEAST PACIFIC

Central and

South America

10°15'S, 101°53'W

10°30'S, 103°20'W

Independencia Bay,

Peru

San Felix

Near Mas Atierra

Near San Felix I.

100 mi S of

San Felix I.

Between Valparaiso

and the Juan

Fernandez I.

33°S, 74°W

Rio Valdivia, Chile

NORTHWF-ST PACIFIC

Japan and Taiwan

24 Apr 25 probably breeding, specimens taken

mid-Oct 53 abundant

24 Oct-24 seen occasionally

Nov 55

22 May 25 probably breeding, specimens taken

1925 some

24 May 25 thousands, large numbers of almost fully

grown young

Aug 58 estimated 2000 breeding

breeds on Islas Frailes del Sur and ranges the adjacent

waters of the Gulf of Panama and the open sea

4 Nov 55 flock of 25-30

28 Aug 64 many

9 Nov 60 groups of 1 and 40

10 Nov 60 one group of 50

11 Nov 60 groups of 1, 20, 20, and 10

13 Nov 60 one possible Sooty Tern

14 Nov 60 groups of 10-50 continuously through the

afternoon

7 Sep 61 one seen by D. R. Paulson

21-22 Dec? 1, more

4 Jan 63 3

8 Nov 55 flock of 14 associated with a convergence

front in the upper layer of the ocean

Hanna, 1926:28

King and Pyle, 1957:37

McLellen, 1926:283

Stager, 1964:365

Wetmore, 1965:456

King and Pyle, 1957:37

Jones, 1965:67

Morzer Bruyns, 1965:63-64

Wetmore, 1965:457

Mitchell in Bourne, 1965:37

Morris in Bourne, 1965:36-37

King and Pyle. 1957:37

recorded breeding from the Tres Marias and Revilla Gigedos south to the northern Galapagos Islands, also at San

Felix Island, Chile

28 Nov 62 1

27 Nov 48 1, in surface water temperature 27.4°C

13 Jan 25 many noted by Murphy, sighting coincident with a general warming of the

water in this area

18 Feb 35 Chapin noted moderate-sized flocks

19 Dec 13 Beck noted birds flying toward the island

10 Oct 62 some birds flying away from the islands

in the morning and toward the islands

in the evening

9 Oct 62 flock of 20 flying toward San Felix in

afternoon

7 Dec 13 observed feeding with shearwaters by Beck

5 Dec 13 4 specimens taken by Beck

2 Aug 1855 1 specimen

occasional summer straggler to southern Japan; breeds on

the Bonin, Riu Kiu, Senkaku Retto, and Marcus islands;

recorded also from Borodino Island and Formosa [TaiMurphy, 1936:1121

Worgan in Bourne, 1964:37

Fleming, 1950:181

Murphy, 1936:1132

Millie, 1963:566

Murphy, 1936:1132

Hachisuka, et al., 1958:222

46
NUMBER 158 47

TABLE A.—Summary of published data on Sooty Tern distribution—Continued

Location

Honshu, Japan

Izu I.

Honshu, Japan

" "

Shikoku

Kyushu

WEST-CENTRAL PACIFIC

26°57'N, 126°07'E

26°36'N, 121°20'E

25°26'N, 124°18'E

24°55'N, 122°01'E

22°N, 124°E

19°N, 163°05'E

135 mi W of Wake I.

Micronesia

14°30'N,113°43'E

9°N, 131°E

7°N, 142°E

Philippines

l°01'N, 119°01'E

0°02'N, 129°47'E

0°09'S, 159°50'E

0°44'S, 136°46'E

1°18'S, 138°35'E

4°22'S, 128°50'E

8°25'S, 119°42'E

8°30'S, 134°30'E

9°S. 123°E

SOUTHWEST PACIFIC

SW Coral Sea

15°10' 151°39'E

to 15°20'S, 151°41'E

15°57'S, 151°50'E

tol5°38'S, 151°39'E

16°10'S, 157°14'E

16°47'S, 152°27'E

to 17°03'S, 152°48'E

New Caledonia

19°44'S, 156°33'E

to 19°50'S, 156°33'E

20°02'S, 153°31'E

to 19°41'S, 153°36'E

20°26'S, 153°09'E

to 19°32'S, 153°05'E

20°48'S, 164°13'E

21°55'S, 173°21'E

22°07'S, 154°20'E

to22°18'S, 154°13'E

22°39'S, 166°28'E

23°21'S, 153°24'E

to 23°36'S, 153°26'E

26°16'S, 161°24'E

27 °S, 176°30'E

29°06'S, 154°01'E

Date

25 Apr 04 j

undated

10 Jul 04

24 Aug 07

4 Sep 50

undated

undated 2

31 May 29 :

10 Jun 29

30 May 29

12 Jun 29 1

16 Aug 60

18 Mar 60

6 Mar 45 (or 46)

Remarks

ilus two undated records

j

> or 6

lock of about 50 (species?)

flock of about 30

ew

1

arge flocks

I

found in the Mariana, Palau, and Caroline islands

19 May 29

27 Oct 60

29 Oct 60

flock of about 100

wo groups of 50

three groups of 40, 10, and 3

recorded from Siquijor and Sulu Islands

14 Aug 29

30 Jul 29

21 Jul 29

25 Jul 29

24 Mar 29

6 Apr 29

27 Sep 63

26 Sep 63

Hock of about 150-200 (species?)

dock of about 58 (species?)

several

many in flocks

.everal (species?)

airly common

many

scattered flocks

vast numbers breeding in this area

11 Sep 62

8 Sep 62

20 Aug 61

8 Sep 62

12 Dec 57

22 Aug 61

17 Aug 61

7 Sep 62

26 Nov 28

8 Jul 62

23 Aug 61

29 Nov 28

14 Sep 62

19 Dec 57

14 Feb 63

1 May 60

3

5

ca. 50

8

:> resent

6

3

ca. 200

arger flock far out (species?)

20

ca. 30

fairly numerous

10

one flock

2

7

Source

Austin and Kuroda, 1953:450-451

•• •• •• "

" " " " "

" " " •• "

" " " " "

Jespersen, 1933:206

..

Brinkley in Bourne and Radford, 1961:25

Mitchell in Bourne and Radford, 1961:25

Dixon and Starrett, 1952:271

Baker, 1951:161

Jespersen, 1933:206

Morzer Bruyns, 1965:63-64

" " " "

Delacour and Mayr, 1946:77

Jespersen, 1933:206

" " "

••

" " "

" " "

Mitchell in Boume, 1965:37

Hindwood, et al., 1963:28-30

Norris, 1967:46

" " "

" " "

Gibson, 1960:18

Norris, 1967:46

" " "

»t it »»

Jespersen, 1933:206

Norris, 1967:46

" " "

Jespersen, 1933:206

Norris, 1967:46

Gibson, 1960:18

Morris in Bourne, 1965:37

King in Bourne, 1964:37
48 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE A.—Summary of published data on Sooty Tern distribution—Continued

Location

29°54'S, 178°30'E

29°56'S, 156°37'E

SO°55'S. 155°17'E

OS Sydney

Lord Howe I.

New South Wales

New Zealand

Near Sydney

Sydney Harbor

Queenscliff

Near Sydney Head

Dorrigo

North I.

S4°S2'S, 172°31'E

CENTRAL PACFIC

Central Pacific

23°S0'N, 162°W

Honolulu

Oahu

Pearl Harbor

2O°23'N, 158°52'W

20°31'N, WWW

Marshalls

7°N, 159°W

7°N, 145°W

7°N, 1S8°W

7°N, 179°E

Gilberts

02°15'N, 169°17'W

Hull I.

8°40'S, 136°54rW

8°30'S, 156°30'W

Marquesas I.

to Palmyra I.

Marquesas I.

SOUTH-CENTRAL PACIFIC

10°08'S. 142°01'W

10o41'S, 172°22'W

11°44'S, 144°10'W

14°39'S, 174°27'W

18°07'S, 179°47rW

18°40'S, 176°21'W

20°57'S, 158°58'W

27°06'S, ffl"41'Vf

29°45'S. 176°57'W

31°35'S, 176°25rW

Date

23 Nov 64

25 Feb 29

20 Dec 57

17 Feb 29

Remarks

singles and small flocks in water temperature 70° F

few

present

1 specimen

regular breeding cycle beginning in September each year

undated

breeding on

lands

May 1892

undated

3 Feb 34

11 Dec 42

25 Jun 50

Feb-Apr

late Jul-Aug

30 Jul 61

reported as

rare straggler

Lord Howe, Norfolk, and the Kermadec is1 specimen

several specimens

1 immature specimen

1 bird observed

2 cyclone-driven birds, 1 collected

7 records following northerly gales

6

1 bird landed on ship

breeding or as having bred on every island

group except the New Hebrides and the Solomons

12 Apr 64

24 May 59

undated

27 May 60

26 May 60

13 Jan 60

Oct-Nov 64

Jun 66

Apr 67

5 Nov 60

7 Nov 60

8 Nov 60

3 Nov 60

Nov 64

27 May 59

28 May 59

1 Oct 28

6 May 64

early Dec 55

2 Oct 28

late Nov 55

5 Oct 28

2 Nov 28

6 Oct 28

8 Nov 28

13 Nov 62

8 Dec 57

21 Oct 28

13 Dec 28

14 Dec 28

15 Dec 28

present

50

many groups all around the coast

hundreds

5

30

occurred near and between breeding atolls

" " " " •• "

..

groups of 2 to 200, one group with immatures present

groups of 1 and 10

groups of I, 10, and 3

three groups of 100

20 seen between Makin and Maiana

1

ca. 1000 seen fishing in small groups

few

large flock over a school of tuna

observed daily at sea

fairly common

abundant in and around these islands

few

flock of about 10 (species?)

still a few (one possible flock of 50)

small flock

120

1

few (species?)

2 and 2

1 specimen

few

Source

Edgar, et al., 1965:42

Jespersen, 1933:206

Gibson, 1960:18-19

Jespersen, 1933:206

Hindwood, et al., 1963:30

Goddard and Hindwood, 1951:170

Falla, etal., 1967:165

Goddard and Hindwood, 1951:170

" " " " "

" »• ,» •, »,

" " " " "

Falla, etal., 1967:165

» .. » ..

Jenkins, 1962:33-34

King, 1967:76

Lamb in Bourne, 1966:33

Peakall. 1960:202

..

King in Bourne, 1964:37

.. ,.

Amerson, 1969:302

..

Morzer Bruyns, 1965:63-64

"

••

"

Amerson, 1969:302

Peakall, 1960:202

" "

Jespersen, 1933:206

Mitchell in Bourne, 1966:33

King and Pyle, 1957:37

Jespersen, 1933:206

King and Pyle, 1957:37

Jespersen, 1933:206

Worgan in Bourne, 1964:37

Gibson, 1960:18

Jespersen, 1933:206

..

.. .,
NUMBER 158

TABLE B.—At-sea sightings of streamered Sooty Terns

Date

JOHNSTON

1963

5 Aug

1964

5 Mar

••

11 Mar

14 Mai

••

••

"

9 Apr

13 Apr

14 Apr

7 May

••

••

••

••

8 May

10 May

15 May

"

••

••

7 Jun

8 Jun

••

••

»

••

••

••

"

••

11 Jun

16 Jun

11 Jul

"

5 Aug

6 Aug

••

"

8 Aug

10 Aug

11 Aug

12 Aug

lime

STREAMERED

0704

1040

1110

1148

1400

1607

0659

0713

0719

0736

0837

0930

1431

1751

1520

1810

1630

1335

1002

1026

1146

1530

1600

1218

1428

1205

1315

1423

1603

1636

1713

0622

0720

0735

1151

1154

1157

1300

1304

1547

0714

0824

1345

1420

-•

0700

0702

0928

0933

1640

1650

1050

1250

So.

I

1

1

1

1

1

1

1

1

3

•)

1

1

1

1

:">

1

4

5

1

1

1

1

1

4

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

Behavior

flying E

flying E

feeding

not noted

flying N

not noted

flying SE

flying NNE

flying N

flying SSE

not noted

flying NE

flying NE

feeding

Hying NE

feeding

• •

flying NE

not noted

flying SE

flying E

flying SE

feeding

not noted

feeding

flying SE

flying NNE

flying SE

flying S

flying ENE

flying NNW

flying ENE

flying WSW

flying ENE

not noted

flying NE

flying SE

flying ENE

flying SE

flying NE

feeding

"

flying NNW

flying N

not noted

flying SE

flying E

not noted

flying NW

not noted

N lat.

15°45'

16°43'

16°41'

"

16°22'

16°40'

16°57'

••

••

••

"

14°07'

16°03'

15°26'

16°20'

17°05'

17°31'

16°54'

16°52'

16°47'

16°20'

16°16'

13°54'

15°36'

16°55'

16°59'

17°04'

17°09'

17°11'

18°05'

17°06'

16°59'

••

16°42'

••

16°36'

"

16°07'

15°32'

20° 02'

15°58'

16°05'

18°30'

16°54'

16°42'

16°41'

14°01'

14°26'

16°24'

14°42'

W long.

169°19'

169°21'

169°23'

169° 22'

169°21'

169°31'

169°39'

169° 36'

••

"

171°49'

171°51'

173°24'

171°37'

171 °20'

169°16'

168° 08'

169° 00'

169° 05'

169° 46'

169°23'

169° 22'

169° 24'

170°02'

169°21'

169°11'

168° 58'

168° 47'

168° 44'

166°28'

I68°27'

168° 38'

168°41'

169°19'

169° 20'

"

169° 27'

169° 20'

169°57'

169°27'

170° 52'

170° 46'

M

165°03'

169°00'

169°23'

169°21'

170° 46'

172°31'

170°51'

173° 57'

Miles from

origin

55 SSE

9 ESE

8 SE

9 SE

25 SSE

5 S

14 NNW

13 NNW

"

"

211 SW

144 SW

187 SW

125 WSW

109 WSW

24 NE

90 NE

30 NE

24 NE

16 W

26 SSE

30 SSE

174 S

76 SSW

13 NE

23 NE

36 NE

48 NE

51 NE

177 ENE

63 NE

52 NE

50 NE

11 SE

10 SSE

39 SSE

79 SSW

200 N

91 SW

84 SW

••

278 NE

30 NE

7 SE

7 SE

180 SSW

226 SW

80 SW

287 SW

Age

adult

"

"

"

"

"

adult

'*

**

immature

adult

adult

immature
50

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE B.—At-sea sightings of streamered Sooty Terns—Continued

Date

1965

IS Apr

19 Apr

••

20 Apr

••

15 May

21 May

17 Jun

••

••

21 Jun

5 Jul

11 Jul

15 Aug

••

••

••

22 Aug

>•

"

••

••

••

••

"

"

"

8 Sep

••

10 Sep

1966

31 Jan

6 Mar

8 Mar

1 Apr

2 Apr

••

4 Apr

5 Jun

'•

••

"

Time

1507

1215

1630

0955

1345

1130

1415

0430

1045

»

1710

0956

1710

0740

"

1018

1143

1414

1418

1419 '

1451

1507

1508

"

1530

1630

1700

1905

0850

1700

1515

1745

0853

0852

0642

1754

0805

1215

1710

1024

1030

1430

0731

0733

0744

0756

0809

0821

0830

0837

0923

1027

1659

1849

1851

No.

2

1

4

10

9

2

3

5

1

17

2

5

12

3

3

11

1

18

3

4

2

Behavior

not noted

feeding

••

••

••

not noted

feeding

not noted

feeding

flying S

flying NE

feeding

flying SE

flying SE

flying NW

feeding

not noted

feeding

not noted

feeding

not noted

feeding

"

••

not noted

feeding

••

••

••

not noted

flying NE

flying N

flying NE

flying W

feeding

"

••

not noted

flying NW

feeding

flying S

••

not noted

feeding

•>

"

not noted

feeding

••

flying NE

flying E

N. lat.

16° 18'

15°37'

16°06'

17°28'

16° 17'

13°32'

18°50'

15°07'

15°22'

••

17°44'

17°07'

15°40'

16°54'

"

16° 32'

16°20'

16°43'

16°44'

••

16°46'

16°48'

"

16°50'

16°54'

16°56'

17°03'

19°47'

19°15'

16°43'

16°28'

16°34'

11°38'

16°47'

16°43'

15°05'

14°22'

13°40'

16°02'

16°03'

16°28'

16° 18'

••

16°17'

16°16'

16° 15'

16°14'

16°13'

16° 12'

I6°08'

16°02'

15°33'

15°23'

••

W long.

169°25'

17S°41'

173°O7'

170°Sl'

172°25'

169°49'

170°24'

169° 35'

170°14'

169°53'

168°06'

173° 39'

169°44'

169°34'

169° 30'

169°29'

"

169° 25'

169°23'

••

"

169°20'

169° 14'

169°12'

169°02'

161 °47'

163° 10'

169°3r

169°39'

170°53'

173°34'

167°21'

169°29'

170°25'

170°40'

171°O3'

171°11'

171°10'

171 °08'

169° 15'

••

169° 17,

169°19'

169°22'

169°23'

169°25'

169°26'

169° 34'

169°45'

170°45'

171°02'

171 °03'

Miles from

origin

28 S

225 SW

218 WSW

73 NW

172 WSW

195 S

137 NNW

97 S

93 SSW

••

63 NNW

83 NE

247 WSW

16 NW

"

13 SSW

25 S

2 S

1 S

"

5 E

8 E

"

11 ENE

17 ENE

20 NE

32 NE

481 NE

394 NE

2 SSW

19 SSW

80 W

392 SW

124 E

4 SSE

113 SSW

160 SSW

209 SSW

107 SW

106 SW

95 WSW

30 S

••

31 S

•>

32 S

33 S

34 S

38 S

45 SSW

101 SW

122 SW

••

Age

adult

"

••

immature

"

adult

"

immature

adult

••

"

adult

••

"

••

••

immature

adult

••

••

•>

••

••

••

••

••

••

••

n

-

••

-

adult

••

»

»

••

»

••

••

"

••

»
NUMBER 158

TABLE B.—At-sea

Date

1966

10 Sep

3 Dec

1967

8 Jan

12 May

1968

12 Feb

Time

1458

1016

1153

1429

1200

HOWLAND STREAMEREG

1966

14 Jul

17 Jul

20 Jul

••

"

••

••

21 Jul

••

M

14 Aug

••

15 Aug

16 Aug

17 Aug

••

••

••

••

••

••

••

••

••

••

19 Aug

16 Sep

19 Sep

••

20 Sep

••

22 Sep

23 Sep

"

••

16 Oct

12 Dec

1967

18 Jan

18 Feb

0832

0845

0846

0830

1017

1144

1617

1724

0936

1645

1649

1010

1025

0845

0930

0649

1659

0923

0948

1015

1044

1059

1117

1135

1204

1320

1330

1415

1440

1500

1515

0850

0808

1035

1425

1522

1543

1736

0430

1040

1710

1015

1652

1153

0836

No.

1

1

1

1

2

1

1

1

1

1

2

1

1

1

3

1

1

1

1

1

1

2

3

1

1

1

3

1

3

1

1

1

3

3

2

1

1

1

sightings of streamered

Behavior

flying N

feeding

not noted

feeding

flying S£

••

flying NW

flying NE

flying E

"

flying NW

flying S

not noted

feeding

flying W

feeding

••

••

••

not noted

••

••

flying ENE

flying NE

flying SE

feeding

flying NE

feeding

flying S

not noted

flying S

feeding

"

not noted

flying N

feeding

not noted

••

feeding

not noted

flying SE

flying E

feeding

N lat.

16°42'

18°44'

16°38'

18° 14'

16°35'

O°53'

0°54'

0°45'

0°41'

0°24'

0°14'

0°34'

0°41'

0°27'

0°38'

0°31'

0°30'

0°40'

0°34'

0°40'

0°42'

0°45'

0°44'

0°42'

0°40'

0°39'

0°38'

0°S7'

0°34'

0°26'

0°25'

0°22'

0°21'

0°20'

0°19'

1°28'

0°52'

0°29'

0°42'

0°52'

"

••

0°48'

0°18'

0°07'

l°05'

0°58'

0°45'

0°49'

Sooty Terns—Continued

W long.

170°13'

164°44'

169°11'

169° 12'

168°35'

176°44'

176°45'

176°31'

176°38'

"

176°36'

176°4r

176°40'

176°32'

176° 36'

176°35'

176°28'

176°40'

176°48'

176°47'

176°44'

176°48'

176°52'

176°57'

176°59'

177°O1'

177°04'

177°12'

177°22'

177°23'

177°30'

177°34'

177°37'

177°39'

177°OO'

176°47'

175°51'

176°26'

176°35'

176°37'

176°23'

176°27'

176°01'

176°46'

176°39'

177°35'

176°29'

Miles from

origin

42 W

299 ENE

19 ESE

89 N

54 E

8 NW

9 NW

7 E

7 S

24 S

34 S

15 SSW

8 SSW

22 SSE

10 SSE

18 S

15 S

14 SSE

12 SW

11 SW

4 SW

12 W

14 WSW

20 WSW

22 WSW

24 WSW

28 WSW

32 WSW

50 WSW

51 WSW

58 WSW

62 WSW

66 WSW

68 WSW

46 NNW

7 NW

52 SE

15 SE

7 NNE

6 N

••

8 S

32 SSE

54 SSE

17 NNW

11 N

56 W

9 E

Age

"

••

"

"

"

"

adult

"

••

••

"

••

"

"

••

••

••

••

"

••

"

••

adult

••

••

••

*•

••

"

••

••

••

immature

adult

••

••

••

51
52 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE C.—At-sea recoveries of banded Sooty Terns

(table based on distance between banding and recovery localities; ? uncertain, - not noted)

Original data

Date Age Location Date

9 May 66

14 Aug 66

9 Apr 66

21 Jul 66

-•

Recovery

Age

adult

"

-

adult

data

Sex

$

$

-

$

Elapsed months

15.2

18.4

14.3

8.7

17.6

0.3

Miles

HOWLAND ISLAND

2 Feb 65 adult

1 Feb 65

19 Jul 65

2 Feb 65

12 Jul 66

18 Jul 66

12 Oct 64

2 Feb 65

1 Feb 65

23 Jul 64

12 Jul 66

19 Jul 66

21 Jul 66

17 Aug 66 immature

1 Feb 65 adult

21 Jul 66

9 Oct 64

1 Feb 65

12 Jul 66

2 Feb 65

HULL ISLAND

26 Sep 65

24 Sep 65 immature

25 Sep 65

JOHNSTON ATOLL

8 Jul 66

3 Feb 64 adult

30 Jan 64

8 Jun 64

27 Apr 65

I Aug 63

25 Jul 63

22 Jul 64

II Feb 64

21 Apr 66

LAYSAN ISLAND

9 Aug 65 immature

MANANA, OAHU

20 Mar 64 adult

1°OO'N-175°47'W

0

oH'N-176°30'W

0°12'N-176°36'W

0°15'N-176°40'W

O°17'X-176°3rW

1°17'N-176°34'W

O°42'N-176°17'W

0°47'N-176°59'W

0°48'N-176°59'W'

l°OrN-176°39'W

O°44'N-176°27'VV

O°38'N-I76°34'\V

O°44'N-176°27'W

0°50'N-176°26'W

lear Howland

0

o

27'S-177o31'W

0°34'N-176°20'W

O°O2'S-176°37'\V

O°14'N-175°52'W

11°57'N16°18'XI5°44'X14°36'N18°58'X18°49'X18°43'X14°59'X17°42'N16°44'N175°49'W

172°57'W

172°2O'W

171°03'W

170°16'W

170°24'W

17O°31'W

170°37'W

169°47'W

169°11'W

ll°09'N-140°53'W

at sea, Hawaiian

area

15 Jul 66

17 Jul 66

13 Jul 66

9 Dec 66

22 Apr 67

23 Sep 66

18 Sep 66

19 Sep 66

23 Sep 66

17 Jul 66

17 Jan 67

20 Oct 65

22 Oct 65

17 Oct 65

22 Nov 65

13 Nov 66

20 May 65

18 Apr 65

16 Apr 65

21 May 65

16 Apr 65

20 Apr 65

8 Jan 67

before 6 Dec 65

mid-Oct

adult

?

adult

adult

immature

adult

adult

adult 9

immature $

$

9

adult

0.1

21.1

17.5

17.4

28.5

4.9

9.1

2.1

1.0

19.6

2.1

21.3

15.5

0.2

2S.5

0.8

0.9

0.8

1.9

4.2

15.6

14.6

10.3

0.8

21.7

21.9

8.8

14.3

8.6

3.9

31.0

52 EXE

38 S

35 S

33 S

32 S

28

22

22

21

17

13

12

11

12

5

N

ESE

W

VV

W

N

ESE

SSE

ESE

ENE

1 W

400

390

370

360

460

202

175

158

141

135

132

124

60

18

XW

xw

NW

NW

sw

wsw

wsw

svv

NNW

XX W

NNW

SW

NNW

E

1,170 SE

0 to 400
Wedge-tailed Shearwater {Puffinus pacificus)*

Warren B. King

Introduction

The material contained in this report was gathered in the course of intensive biological investigations in the central and eastern Pacific by the

Pacific Ocean Biological Survey Program (POBSP),

Smithsonian Institution, Washington, D. C Humphrey (1965) has given a general summary of the

activities and objectives of the program, and Gould

(pp. 1-5) has discussed the methods and materials

and areas of coverage of the program.

At-sea work began in 1963 and was concluded

in 1969. This report is one of a series of studies of

the pelagic distribution of Pacific seabirds. By the

end of 1968 POBSP personnel observed 81,740

Wedge-tailed Shearwaters during 2747 days (26,457

hours) and 259,710 miles of observation.

The Wedge-tailed Shearwater (Puffinus pacificus)

is an abundant, wide-spread species in the tropical

and subtropical Pacific and Indian oceans; it may

be encountered far from land most of the year. In

the central Pacific its population is approximately

one-half million birds (Table 13). It also breeds on

numerous islands in the western Pacific from the

Bonin, Volcano, and Pescadore islands in the

north, along the east coast of Australia to Montague Island near Bass Strait in the south-. In the

eastern Pacific it breeds only on San Benedicto Island of the Revilla Gigedo group.

Its marine range is only slightly larger than its

breeding range in the Pacific, although in the Indian Ocean its marine range appears to extend

farther north than its breeding range (Bailey, 1968).

In the eastern Pacific it has been recorded from

Warren B. King, International Council for Bird Preservation,

Smithsonian Institution, Washington, D.C. 20560.

Baja California south to the Gulf of Guayaquil,

Ecuador. In the western Pacific it has been recorded

from the Izu Islands south of Japan to the South

China Sea and the Tasman Sea.

The northernmost records are a sighting (POBSP.

TABLE 13.—Maximum estimates by POBSP

(1963-1968) of Wedge-tailed Shearwaters on

islands in the central Pacific*

Island

Kure

Midway

Pearl and Hermes Reef

Lisianski

Laysan

Gardner Pinnacles

French Frigate Shoals

Necker

Nihoa

Islets of the Main Hawaiian group

Johnston

Christmas

Canton

Phoenix

McKean

Taongi

Bikar

Taka

Eniwetok

Wake

Number

6,250

3,000

22,400

60,000

200,000

100

13,600

2,000

25,000

70,000

2,500

6,000

40

10,000

500

12,000 +

6

12

3

6

• Paper Number 70, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

•Estimates are of birds "using" the islands, including

breeding birds, nonbreeders, and, in some cases, chicks. Estimates of nocturnal burrowing birds are notoriously inaccurate so that many of these estimates may be low by 100

percent or more. On the basis of total number of birds

handled in one year during banding operations on islands on

which coverage was thorough (Kure, Johnston), roBSP experience indicates that most initial estimates should be doubled

or trebled. Above estimates, however, give a good idea of

order of magnitude of the populations.

53
54

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Paul Woodward) at latitude 35°26'N, longitude

164°17'W in August 1966 and a typhoon-driven

bird found 30 September 1959 in Fukui, Japan, near

the Sea of Japan at latitude 36° N (Anonymous,

1960). The southernmost record is a U.S. Fish and

Wildlife Service (USFWS) band return record from

Cook Strait, New Zealand, on 8 November 1965;

the light-phase bird had been banded as an adult

19 September 1963 on Johnston Atoll by POBSP personnel. Another Wedge-tailed Shearwater, also

light-phase, was reported by Falla (1962) from

Makara, Wellington, also in Cook Strait. On tenuous grounds Falla assigned this bird to one of the

north Pacific light-phase breeding islands, rather

than the Shark's Bay, Western Australia, breeding

grounds where light-phase birds occur as well.

Murphy (1951) recognizes two subspecies, P. p.

pacificus Gmelin, an all-dark form from the Kermadec Islands, Norfolk Island, and Kandavu Island

of the Fiji group, and P. p. chlororhynchus Lesson,

a slightly smaller form, from all other islands in

the Pacific and Indian oceans. The latter occurs in

both light-phase and dark-phase morphs, and occasionally in an intermediate form. The light-phase

morph predominates in all breeding colonies north

of 10°N except the Marianas, where only dark

birds occur, and in the Revilla Gigedos. These

breeding grounds include:

island or group latitude

San Benedicto 19° N

Main Hawaiians 19°-22°N

Northwestern

Hawaiians 23°-28°N

Johnston Atoll 16°N

Northern Marshalls 11°-14°N

Bon ins, Volcanos 24°-27°N

Pescadores 20 °N

longitude light-phase

pop- <%)

110°W 33 or less

154°-160°W 97

162°-179°VV 99 +

169°W 95

162°-170°E 93

140°-142°E 99 +

119°E 99?

Light-phase birds make up about one percent of

the Phoenix Islands' population. Light-phase birds

have not been reported in any other breeding colonies in the south Pacific. The figure of 33 percent

light-phase birds for the Revilla Gigedos comes

from Murphy's (1951:9) comment that "in certain

colonies, as at the Revilla Gigedo Islands, both

dark- and white-phase birds are found together in

a respective ratio of about two to one." The comment was probably paraphrased from Anthony

(1898:313), who was speaking of the birds "about"

San Benedicto and Socorro Islands, not particularly of the birds "on" either island. Anthony's

(1900:251) statement that "by far the greater number were in dark plumage," refers to breeding birds

on San Benedicto, and Loomis (1918:143) quotes

Bunnell's notes which say that "the white-breasted

ones were a very small proportion of the total

number" just offshore or on the island of San

Benedicto. At the risk of reading information into

these comments, it would seem that the proportion

of light- to dark-phase birds on San Benedicto may

be smaller than one to two.

BREEDING PHENOLOGY.—The breeding season is

from April to November in northern subtropical

Pacific breeding localities, and October to May in

southern subtropical localities. Birds are most

abundant at sea near their breeding areas during

these months. When the birds of the year fledge,

young and old alike disperse from the general vicinity of the breeding islands, so that numbers encountered nearby at sea are only a small fraction

of those seen during the breeding season. The

routes of dispersal are not yet known.

Birds from tropical Pacific breeding stations are

often present near their breeding islands year

round, and their breeding cycle may extend beyond

the eight months of the subtropical breeders.

In the Hawaiian group, Johnston Atoll, and the

northern Marshalls, the Wedge-tailed Shearwater

breeds synchronously on an annual cycle. Birds appear first on their breeding islands at night in early

March. In the Hawaiian group maximum numbers

occur in May, although on Johnston Atoll numbers increase gradually to an August peak. Eggs are

laid in mid-June. Nonbreeders visit the islands

sporadically and usually account for more than half

the population on an island at any given time.

Eggs hatch in early August and by mid-August the

chicks are left alone in their burrows during the

day. By early November neither breeding nor nonbreeding adult birds visit the island, and by the

middle of November the young have fledged and

no birds remain. From September to November

large flocks are often encountered off the shore of

breeding sites. Birds presumably form such flocks

prior to migration.

The gonadal development cycle of light-phase

birds was determined on the basis of measurements

of 75 males collected at sea in all months but January and of 79 females from all months but January,

October, and November (Figure 29). Gonadal de-
NUMBER 158 55

15r

E

E

Ovary length

Left testis length • •""" yy

Ovary width

Left testis width

Largest ovum

JFMAM J JASO N

FICURF. 29.—Monthly gonad dimensions of light-phase Wedge-tailed Shearwaters collected at sea.

velopment apparently begins with the birds' return

to the vicinity of their breeding islands and reaches

a peak by May, a month before eggs are laid. After

May, gonads decrease in size, but the decrease stops

between July and October during which gonad

sizes hold constant; thereafter they shrink rapidly

to minimum size during winter. There is little indication from the data of any distinction between

adults and subadults on the basis of gonad size. An

exception was that two of four birds collected on

the equator in April had gonads very much smaller

than the mean dimensions, suggesting they might

have been subadults. The other two, and several

others taken later in the year south of 10°N latitude

where subadults might be expected to be found,

showed gonadal development not appreciably different from monthly averages.

Birds from Christmas Island breed on a schedule

similar to that of Hawaiian birds although it is

somewhat more prolonged (Schreiber and Ashmole, 1970), but it is not known if the birds disperse

after breeding.

In the Phoenix Islands the breeding cycle is annual but the peaks are not clearly defined (POBSP) .

The cycle is five months ahead of the cycle in the

Hawaiian group. Breeding birds arrive at their islands in September and eggs are laid in late November or early December. Peak populations are

found on the islands at this time, although more

than half of the birds present are nonbreeders. Eggs

hatch in early February and by March the adults

visit the islands only sporadically at night to feed

their chicks or to roost. Most adults leave the islands in early May, followed by most of the fledged

young two weeks later. By early June few birds are

left on the islands except small roosting populations which remain during the nonbreeding season.

The breeding cycle of San Benedicto Island appears to be roughly synchronous with that of the

northwestern Hawaiian group on the basis of the

only available information: two egg dates, 31 May

and 26 July (Anthony, 1900:252; Loomis, 1918:

142).

SUMMARY OF PUBLISHED PELAGIC RECORDS.—The

appendix summarizes the status of the Wedgetailed Shearwater in the Pacific Ocean. Because few

observers are familiar with the distinguishing characteristics of this species, many of the pelagic records are ambiguous; they could refer to one or more

species that resemble either light- or dark-phase

Wedge-tailed Shearwaters.

In the eastern Pacific Wedge-tailed Shearwaters

have never been identified with certainty south of

the Gulf of Guayaquil (latitude 3°S) (Le've'que,

1964b:53-54). They have been reported several

times along the Middle American coast from Panama to Mexico near Manzanillo. Murphy's (1958)

record of both light- and dark-phase birds off north
56 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

era Baja California in December is exceptional;

they have not otherwise been reported north of

21 °N (Loomis, 1918), fully 500 miles farther south.

Records from the eastern Pacific have been obtained

mainly in the northern spring and fall.

Morzer Bruyns (1965) saw Wedge-tailed Shearwaters over the Equatorial Countercurrent across

most of the Pacific in November, dark-phase west

of the Line Islands, and mixed from there east;

King and Pyle (1957) found them in the Countercurrent between the Line Islands and Mexico in

October.

In the southwest Pacific several authors (Jespersen, 1933; Fleming, 1950; Gibson, 1960; Mitchell,

in Bourne, 1965; Morris, in Bourne, 1965; Norris,

1967) have noted scattered individuals or small

groups of dark-phase birds between Samoa and

Australia throughout the year.

ACKNOWLEDGMENTS.—In addition to all the cooperators who have made this paper possible (p.

5) special thanks are due to Gerald A. Sanger and

Patrick J. Gould who were closely involved in

analyzing the data. The latter was almost solely

responsible for the section entitled "Density and

Distribution within Equatorial Currents."

I am also indebted to William R. P. Bourne,

Roger Bailey, and George E. Watson for their critical reading of the manuscript and their many helpful suggestions and comments.

Distribution and Abundance

Figure 34-57 (pp. 68-91) show monthly densities

of Wedgetailed Shearwaters in the central and eastern Pacific based on POBSP observations between

1963 and 1968. Densities are expressed in terms of

birds per linear mile of observation, and located on

the monthly map at the ship's noon position. Areas

of similar daily densities are contoured to show the

relative abundance of the species in all areas of the

Pacific where POBSP observations have been made.

In cases where parallel ocean transects were made

on cruises spanning two months, the contouring

takes into account the distribution and abundance

reflected in adjacent areas even though the data

came from different months. Because of their geographical and, often, phenological distinctness,

light-phase and dark-phase birds are treated separately.

DENSITY AND DISTRIBUTION WITHIN

EQUATORIAL CURRENTS

The Equatorial Countercurrent is an eastwardflowing current, bounded on the south by the westward-flowing South Equatorial Current and on the

north by the westward-flowing North Equatorial

Current or the California Current Extension, depending on the longitude.

Sverdrup, et al. (1942:709) point out its salient

features, i.e., it is a well-developed, northern hemispheric phenomenon, whose boundaries fluctuate

with the seasons, moving north with the northern

summer. Data from the Carnegie Expedition discussed by Sverdrup, et al. (1942:709-711) show that

at latitude 140°W the countercurrent lies between

3°N and 10°N. Due to a distinct transverse circulation superimposed upon the major flow direction,

a divergence occurs at the northern boundary of

the countercurrent and at the equator, while a convergence occurs at the southern boundary. They

speculate, on the basis of the plankton collections

of the Carnegie Expedition, that divergences are of

high productivity. Similarly, convergences concentrate plankton and organisms that feed on plankton along narrow fronts (Ashmole and Ashmole,

1967). Other authors, e.g., Murphy (1936) and

Morzer Bruyns (1965), have noted some of the effects of oceanic currents on density and distribution of birds.

In the central Pacific Wedge-tailed Shearwaters

may be found throughout the current areas. In

general the dark-phase population predominates in

the area south of 10°N, the area generally covered

by the Equatorial Countercurrent and the South

Equatorial Current. The dark-phase population

moves north in conjunction with the northward

movement of warm waters during the northern

summer months.

North of the countercurrent, light-phase birds

predominate, although small numbers may sometimes be encountered as far to the south as the

equator or farther. These may represent migrants

or nonbreeding visitors since they occur primarily

during the nonbreeding period of the light-phase

population.

CENTRAL PACIFIC.—From January 1964 through

February 1967, sixteen cruises were made by the

POBSP across these equatorial currents in the area

bounded by longitudes 165°W and 180°. Surface
57

15

North

Equatorial

Current Equatorial Countercurrent

Degrees North Latitude

FIGURE 30.—Density of Wedge-tailed Shearwaters in relation to latitude across the equatorial

currents in the central Pacific (165°W to 180°), all months, 1966. (Shaded bars -= dark phase;

white bars = light phase.)

water temperature ranged from 25.5° to 30.6°C

throughout the period of study; the vast majority

of samples fall between 27 °C and 30°C. Lowest

temperatures were generally found north of the

countercurrent and highest temperatures south.

Within the countercurrent temperatures remained

remarkably constant.

Small densities of Wedge-tailed Shearwaters were

recorded throughout the current area at all times

of the year; a few notable concentrations occurred

between 4°N and 7°N in winter and spring, and

at 9°N in July. A July peak, composed of 99 percent dark-phase birds, occurred during the period

of northward movement of the dark-phase population. A concentration in the fall at 15°N can

best be explained in terms of the attraction of

Johnston Atoll, a nearby breeding site. Unlike

Sooty Terns, whose pattern of distribution in the

Equatorial Current area does not conform to any

boundaries (Gould, p. 32 herein), Wedge-tailed

Shearwaters appear to be most abundant within

the borders of the Equatorial Countercurrent. This

is best exemplified by Figure 30, in which all the

data from 1966 are combined. Data from 1966 were

used because data were complete enough to permit

identification of the countercurrent on the basis of

water temperature samples.

EASTERN PACIFIC.—In the eastern Pacific the

Equatorial Countercurrent is generally well defined

east to 90°W longitude from June through December, but diffused or absent during the rest of the

year. Its southern boundary remains relatively stable at 4°N to 6°N; its northern boundary fluctuates between 8°N and 12°N. It is farthest north

during the northern summer (Wyrtki, 1966; n.d.).

Figure 31 shows densities for six cruises through
58

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

5.0

4.5

4.0

3.5

_» 3.0

8.2.5

5 2.0

1.5

1.0

.5

6.08

15 14 12 10

m

8 7 6 5

Equatorial Countercurrent

Degrees North Latitude

FIGURE 31.—Density of Wedge-tailed Shearwaters in relation to latitude across the Equatorial

Countercurrent in the eastern Pacific (97°W to 126°W), 1967. (Shaded bars = dark phase;

white bars = light phase.)

the area bounded by 97°W and 126°W during

1967. Surface water temperatures show a different

pattern for these cruises than for the central Pacific cruises. Temperatures remained between 25.5°

and 28.8°C in latitudes south to ca. 6°N. At 6°N,

temperatures began to drop rapidly; at ca. 2°N

readings were between 23.8° and 25.7°C, dropping

in one instance to 20.7°C near the equator at

97°W.

Both color phases occur within this area, and, although the data base is too small to provide a complete picture, it appears that light-phase birds (possibly nonbreeding sojourners from the central Pacific) predominate in the northern winter, while

dark-phase birds (possibly from the Revilla Gigedo

population) predominate during the rest of the

year.

All large concentrations were found between

4°N and 10°N. In February and March highest

densities were near 10°N. Due to the unstable condition of the countercurrent at this time, its boundaries cannot be defined clearly. In June and July

highest densities were from 4°N to 5°N, corresponding fairly closely with the southern boundary

of the countercurrent; smaller concentrations were

found at 7°N and from 10°N to 11°N, the former

being just north of the southern boundary of the

countercurrent, and the latter just south of the

northern boundary. In the fall (September) only

one large concentration was noted, at 8°N, somewhat south of the northern boundary of the countercurrent. In the eastern Pacific, especially in the

northern summer when the Equatorial Countercurrent is strongest, Wedge-tailed Shearwaters
NUMBER 158 59

reach highest densities near and within the borders

of that current.

RANGE OF SEA SURFACE TEMPERATURES AND

SALINITIES AT WHICH WEDGE-TAILED SHEARWATERS

WERE OBSERVED

The Wedge-tailed Shearwater is distributed

throughout most of the tropical central and eastern

Pacific Ocean, and, thus, it is not surprising to find

that the range of sea surface temperatures and

salinities at which the species was observed is

roughly as broad as the recorded temperatures and

salinities of the area. Sea surface temperatures were

recorded on a sufficiently large number of cruises to

provide a substantial amount of data from which

to draw conclusions; salinity determinations were

far fewer, and the data are less conclusive.

The water samplings within five minutes of the

hours of 0800, 1000, 1200, 1400, and 1600 were assumed to give a fairly accurate measure of the

temperature and salinity for one hour before and

one hour after the hours mentioned. All sightings

made one hour before to one hour after were assigned the temperature and salinity values of said

hours. Since each sample covers two hours of observation, the ratio of birds to samples divided by

2 yields a bird per hour of observation figure.

TEMPERATURE.—Sightings made when no sea

surface temperatures were taken, or more than one

hour before 0800 or after 1600, account for slightly

more than one-half the data. Temperature correlations apply to 34,073 of 82,000 Wedge-tailed Shearwaters observed during the study. Table 14 shows

the number of birds observed in conjunction with

each whole degree of temperature centigrade, the

number of water samples at each temperature, and

the ratio of birds to samples.

Table 14 suggests that Wedge-tailed Shearwaters

showed no great sensitivity to temperature as long

as it was above 21 °C. The lowest sea temperature

at which Wedge-tailed Shearwaters were observed

was 15.0°C. Two individuals were seen at this remarkably low temperature; otherwise the lowest

temperature was 20.8°C, and the highest was

33.0°C.

SALINITY.—Far fewer salinity measurements were

made, too few to show anything but the range of

salinities over which Wedge-tailed Shearwaters

were observed. Table 15 shows the number of birds,

TABLE 14.—Relative abundance of Wedge-tailed

Shearwaters at various sea surface temperatures

Temperature (°C)

20

21

22

23

24

25

26

27

28

29

30

31

Total

Number Number of

of birds water samples Birds/Sample

0

13

502

278

5,193*

1,618

11,642

6396

5,579

1,185

1,398

69

34,073

56

66

75

98

133

445

853

900

814

340

276

14

4,070

.00

.20

6.56

2.84

39.05

3.64

13.65

7.33

6.85

3.49

5.07

4.93

'Includes a single sighting of 3500 individuals. This sighting is unusually large, and accounts for the inflated birds/

sample figure at 24°C.

TABLE 15.—Wedge-tailed Shearwaters observed at

various sea surface salinities

Surface salinity

(parts per thousand)

33.0-33.3.

33.3-33.7..

33.8-34.1 .

34.2-34.5

34.6-34.9

35.0 +

Total

Number Number of

of birds water samples Birds/Sample

4

18

17

84

158

87

368

4

11

31

46

49

38

179

1.00

1.64

0.55

1.83

3.22

2.29

the number of samples, and the birds per sample in

each of six salinity ranges. Table 15 shows a fairly

even spread across the recorded salinity range, with

a tendency toward greater abundance at salinities

34.6 parts per thousand and above. The lowest recorded salinity at which Wedge-tailed Shearwaters

were seen was 32.60 parts per thousand; the highest

was 36.54 parts per thousand.

SPECIMEN RECORDS, MOLT, AND BAND RECOVERIES

SPECIMEN RECORDS.—The POBSP secured specimens of Wedge-tailed Shearwaters at sea in both
60 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

30°

N

20°

10°

0°

0°

s

180°

•

•

•

•

•

»

\

•

170* \

it

•

 T

•

I-

•

- •

DS

•

•

-

r.

i •

-

! |

160

•A-

•

:

•sir

•

*

•

.

>

1

•

L

•k

(

1

|

i

o

150

1

N

 it

10*

0*

120 W

12C*

s

1

<.

110

>

5,i

, \

v S

r

IK)'

H

i

|

s.

00

no

V\

30"

20

FICURE 32.—Distribution of light- and darkphase Wedge-tailed Shearwater specimen records: left, in the central Pacific; right, in the

eastern Pacific.

the central and eastern Pacific. Table 16 lists the

numbers of specimens of the two color phases collected each month. Figure 32 shows the location; by

degree squares, where specimens were obtained;

color phases are differentiated.

TOPOGRAPHY AND SYNCHRONY OF MOLT.—Primary molt proceeded distally from one locus. It was

far more symmetrical than rectrix molt. The primaries on either wing were almost invariably at

identical stages of growth. Growth differentials of

one-half of a feather length were noted rarely. In

distal primary molt (primaries 7 to 10) only one

feather was replaced at a time. Growth of a distal

primary was nearly completed as the next one began to grow. Several inner primaries can be replaced simultaneously.

Rectrix molt was most intense during later primary molt. It was only marginally symmetrical,

usually more in the number and spacing of replaced

feathers than in their position. For example, rectrices 2 and 4 might be growing on the left, and

rectrices 3 and 5 on the right. Rectrix replacement

followed no fixed sequence. Usually one or two,

and up to five, of the six rectrices on each side were

replaced simultaneously.

Contour feather molt probably started at the

same time as, but was more protracted than, primary molt. Head and nape feathers were replaced

first, followed by scapular and rump feathers. New

head and nape feathers of light-phase birds were

gray and soft; old ones were browner and coarser.

Newly replaced scapulars had conspicuous pale

scallops at their tips. These pale scallops were most

conspicuous in light-phase birds in December (presumably first-year birds), slightly less so in adults

in April. Most December light-phase birds had gray

vermiculations on the crissum, flanks, and sides,

similar to those of adult Pink-footed Shearwaters
NUMBER 158 61

TABLE 16.—Specimens of Wedge-tailed Shearwaters collected by the POBSP each

month

Area and

color phase

CENTRAL PACIFIC

Light phase

Dark phase

EASTERN PACIFIC

Light phase

Dark, phase

Total

Jan

0

- 3

-

_

3

Feb

3

3

-

1

7

Mar

1

2

3

6

Apr

12

20

-

_

32

May

32

7

-

39

Jun

25

17

1

43

Jul

18

10

-

1

29

Aug

30

2

-

32

Sep

24

10

-

34

Oct

2

5

4

1

12

Nov

1

11

-

12

Dec

16

3

-

19

Total

164

93

8

3

268

(Puffinus creatopus). Such vermiculations were

present infrequently in light-phase birds from other

months.

First-year birds probably retain their juvenal

plumage for 15 months. Adults molt primarily during their nonbreeding season, although replacement of contour feathers extends throughout the

breeding season. Since adults and subadults are

present together on islands, and most likely also

at sea, most age-classes were probably sampled in

the POBSP collections. Thus, it is likely that molt

occurs simultaneously in all age-classes after the

first year.

SCHEDULE OF MOLT.—Light-phase Birds: No

light-phase birds were collected at sea in January.

Few were seen in the central Pacific, but they were

common in the eastern Pacific. In early February in

the eastern Pacific POBSP personnel (Woodward,

pers. comm.) reported that they had noticeable

gaps in their primaries, indicative of molt of the

inner primaries. The three central Pacific specimens from February had no molt of remiges, rectrices, or contour feathers; two had gray vermiculations on flanks and abdomen. These three were

probably first-year birds with 3-month-old plumage

since March and April specimens, presumably

adults growing their 9th or 10th primaries, were

in the midst of rectrix replacement and had replaced head, nape, and some scapular contour

feathers. Some March specimens collected on the

northwestern Hawaiian Islands were completing

growth of their 10th primaries. In April seven of

twelve specimens taken at sea had completed remex

and rectrix molt, but all were still replacing contour feathers. In May only one of 32 specimens had

not completed flight feather molt, but contour

feather molt was continuing in the scapulars and

on the rump. No flight feather molt occurred on

any bird from June to December. However, all sixteen December specimens had fresh plumage, including remiges and rectrices with a silvery sheen

and prominent white scalloping on scapular and

lower back feathers. (The scalloping was noticeable

from a considerable distance at sea.) Their remiges

had broad vanes and blunt tips with small sharp

central points, similar to those of May specimens,

indicative of unworn feathers. There was no indication of remex replacement in the small sample of

October and November birds, so I conclude that

the December birds, which were all from the central Pacific, were fledglings and that adults and subadults had already left that area. Although the

date of onset of molt is not known, adults and subadults might have already started to molt their

worn plumage by December. These December birds

were the only ones that followed ships regularly

(see "Behavior").

Dark-phase Birds: The molt cycle in dark-phase

birds is more complex than it is in light-phase

birds because of the geographical and temporal

overlap of populations at sea. There was some rectrix or remex molt in 40 out of 96 birds, and in all

months but May. Using the clear-cut molt cycle of

the light-phase birds as a model, it is difficult to

explain the molt cycles of dark-phase birds. Phoenix

Islands' birds lay eggs in November and December;

they should start flight-feather molt in May and

complete it in October. Many specimens conform to

this schedule. Five of 17 June birds were growing

primaries 4, 5, or 6; 7 of 10 July birds were growing primaries 6, 7, 8, or 9; several August birds and

7 of 10 September birds were growing primaries 9
62 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

or 10, and all 5 October birds had completed or

nearly completed molt.

Christmas Island birds lay eggs in June and July.

They would be expected to begin molt in November and to complete it in April. Seven birds collected in November were growing primaries 3 to 7;

two January birds were growing primary number

8; 17 of the 20 April birds and all May birds had

completed molt of flight feathers. These birds conform to the Christmas Island schedule.

There are still a number of dark-phase specimens

that conform to neither of these schedules. The

large number of birds molting at all times of the

year suggests two explanations: either most birds

are from local populations (e.g., Line and Phoenix

islands) and are present around their breeding islands a greater part of the year and molt is more

protracted than in their subtropical, light-phase

counterparts, or the central Pacific is invaded by

postbreeders from other populations. The two

theories are not mutually exclusive. I suspect both

are true.

BAND RECOVERIES.—Between 1963 and 1969

POBSP personnel banded 75,285 Wedge-tailed Shearwaters, 65,806 in the Hawaiian Islands, Johnston

Atoll, and the northern Marshall Islands, and 9,479

in the Line and Phoenix islands. Nineteen banded

birds were recovered at sea by August 1969. Three

had been banded on Johnston Atoll; the remainder

had been banded on islets off the northeast coast

of Oahu.

The only significant recovery is the southernmost

record from Cook Strait, New Zealand, described

in the introduction. Recoveries of birds banded on

Johnston Atoll were within 300 miles southwest or

northwest of Johnston Atoll. Birds banded on islets

off Oahu were recovered within 100 miles in all directions of Oahu. All recoveries were made between

April and October—the breeding season.

On 11 October 1964 a bird that had been marked

with an orange plastic leg streamer on Johnston

Atoll was seen at latitude 9°25'N, longitude

152°55'W, about 1250 miles southeast of its place

of marking. Although it is tempting to suggest that

this is evidence for migration, individuals doubtless

range thousands of miles searching for food, so that

this location might well be included within the

possible foraging range of the Johnston Atoll

population.

DISCUSSION

In the central Pacific light-phase distribution and

abundance at sea were quite evidently tied to the

breeding cycle of the birds on the Hawaiian Islands

and Johnston Atoll. During the northern winter

light-phase bird abundance was lowest and, although there was a poorly defined density center at

the Equatorial Countercurrent, for the most part

the few birds that were recorded were scattered. In

February light-phase birds were virtually absent

from the central Pacific north of 10°N (7 individuals in 4 years). Data from March showed birds reentering that area, and from April through November a typical distribution pattern prevailed with

only minor irregularities; maximum densities during this period were recorded consistently within

100 miles of the breeding islands.

In the eastern Pacific the timing was reversed.

Light-phase birds were most abundant from October to February (a maximum of 10.6 BPM south of

Guatemala in February), and least abundant from

March to September. Greatest densities were recorded between 6°N and 12°N, the area of the

Equatorial Countercurrent, and the normal lightphase range did not appear to extend very much

farther north or south. The northern limit appeared to be approximately 25°N latitude.

I conclude that the eastern Pacific is a major wintering ground for light-phase birds from the Hawaiian group. I suspect they migrate there along

the Equatorial Countercurrent and return via the

North Equatorial Current.

The at-sea distribution and abundance of darkphase birds cannot be tied as readily to their breeding cycles. In the first place the two populations

that breed in the central Pacific do so at opposite

seasons. (Increasing density in the eastern Pacific

concurrent with the beginning of the breeding season on Christmas Island suggests that the bulk of

eastern Pacific dark-phase birds in the northern

summer do not come from Christmas Island.) Secondly, both populations number in the tens of

thousands, rather than hundreds of thousands as

does the Hawaiian population. Thirdly, there are

many more dark-phase colonies across the Pacific

than there are light-phase colonies. Thus, assigning

islands of origin to any group of dark-phase birds

encountered at sea is, at our present level of knowledge, only conjecture.
NUMBER 158

Several tendencies in dark-phase distribution are

worth noting. The first is the repeated association

of high densities with the Equatorial Countercurrent area, not only in the central Pacific but also in

the eastern Pacific. The second is the extent and

timing o£ the northward penetration of dark-phase

birds. This penetration began in April at the same

time that light-phase birds were once again becoming numerous to the north. It increased in scope

and intensity to a peak in July and August, during

which time dark-phase birds were found nearly as

far north (to ca. 23°N) as light-phase birds. Numbers decreased thereafter until there were almost

no dark-phase birds to be seen north of 10°N during December, January, and February. In other

words, the distribution and abundance pattern of

dark-phase birds north of 10°N in the central Pacific paralleled that of light-phase birds.

A parallel situation occurs in the Indian Ocean

(Bailey, 1968). During the northern winter, the

breeding season for Wedge-tailed Shearwaters in

the western Indian Ocean, the birds are distributed

most abundantly along the Equatorial Countercurrent. In summer, when the countercurrent weakens

or is absent, birds move north to the Bay of Bengal and the Arabian Sea in substantial numbers.

In the eastern Pacific light-phase and dark-phase

birds occupied roughly the same area, but they

reached maximum abundance at different times of

year. Both phases reached greatest densities between

the Equatorial Countercurrent and the coast of

Mexico near Manzanillo. Light-phase birds generally were not seen south of 4°N, whereas darkphase birds were seen occasionally as far south as

POBSP observations were made (to latitude 20°S in

some months). Light-phase birds were most abundant between October and February; dark-phase

birds attained highest densities from June to September. It is likely that a few birds of both phases,

probably nonbreeders, were present throughout the

year in the eastern Pacific.

The implication of an abundance cycle in the

eastern Pacific of dark-phase birds similar to that of

light-phase birds, although several months out of

phase, is that dark-phase birds from yet unspecified

breeding sites perform an annual translongitudinal

migration also. Even if all the dark-phase birds encountered in the eastern Pacific were from the

Revilla Gigedos, which is quite unlikely, they must

be making an extensive migration, for there are

fewer dark-phase birds to be found in the eastern

Pacific from October to May than from June to

September.

Several sources (Jespersen, 1933; Dixon and Starrett, 1952; MacDonald and Lawford, 1954; Morzer

Bruyns, 1965) indicate the presence in the western

tropical Pacific between New Guinea and the Marianas, and in the Philippine Sea, of large numbers

of dark-phase Wedge-tailed Shearwaters from April

to October. POBSP personnel saw light-phase birds

between the Tokelau and Samoan islands at 12°S

latitude in February. Dixon and Starrett (1952)

also suggest that light-phase birds are present, at

least south of the Marianas, in January and February although these may have been any of several

other species, especially Streaked Shearwater (Calonectris lencomelas). Thus there may be in the

western Pacific a situation directly analogous to

that of the eastern Pacific in which both phases are

present but with abundance peaks in different seasons.

Behavior

FEEDING.—Wedge-tailed Shearwaters have been

observed feeding on the surface, under the surface,

and in the air. The method most frequently noted

by POBSP observers, at least for diurnal flocks, was

"contact dipping," to use the terminology of Ashmole and Ashmole (1967). Second in frequency

was "feeding on the surface," third was "air dipping," and fourth was "air diving."

In contact dipping birds flew close to the surface, wings held back as if to hover, sometimes

touching the surface with outstretched feet. Head

and neck were plunged down several inches into

the water. Forward momentum was regained by

vigorous wing beats and foot paddling. Usually

when a fish was caught it was eaten without interrupting flight although birds stopped on the surface occasionally, presumably to swallow heavy

prey. This was the only method of feeding observed

at night (Gould, 1967), although it is likely that

feeding on the surface was used too.

Feeding on the surface was often accomplished

from a sitting position but sometimes a surface dive

was employed, although rarely forcefully enough to

submerge a bird completely under water. Wing tips

and tail usually remained out of water.

Air dipping was seen infrequently. It involved
64

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

70 T

1 2 3 5 610 11-25 26-50 51100 101

Number in Sighting

FIGURE 33.—Number of Wedge-tailed Shearwaters per sighting in a sample of 1000 sightings in which this species was

recorded.

pursuit of a Hying fish above the surface of the water, sometimes accompanied by vigorous foot strokes

for increased speed.

Air dives were rarely observed. They involved a

dive into the water "just about like the boobies"

(POBSP, Dayle Husted). No further description is

available.

There were no observations to indicate that birds

swim any distance under water, in spite of adaptations for this purpose such as laterally compressed

tarsi and compact plumage (Kuroda, 1954; Storer,

1960).

FLOCKING.—Figure 33 shows the number of

Wedge-tailed Shearwaters counted or estimated per

sighting in a random sample of 1000 sightings in

which the species was observed. A sighting is defined here as the observation of one or more birds

acting as a unit. Occasionally it was difficult to decide whether birds seen at the same time were associated or not. This was especially true close to

breeding areas where streams of birds of several

species could be seen coming and going at the same

time.

Most sightings (66.9%) were of single birds.

Progressively fewer sightings were made of larger

groupings. Only 0.3 percent of sightings contained

100 or more birds. However, the largest number

seen in one sighting was 3500. This was part of a

large milling mass of birds near Kaula Rock. Of 70

flocks containing 100 or more Wedge-tailed Shearwaters, the mean number for that species was 307.

Fifty out of 70 (71.4%) flocks of more than 100

Wedge-tailed Shearwaters were within one day's

travel (100 miles or less) of the Hawaiian Islands.

ASSOCIATION WITH OTHER SPECIES.—Casual observations at sea suggest that birds of some species

tend to occur individually, others tend to associate

frequently with other members of the same species,

and still other species tend to occur in mixedspecies aggregates. Wedge-tailed Shearwaters usually travel singly or in small groups, but feed most

frequently in large mixed-species flocks.

Data on association of Wedge-tailed Shearwaters

in all sightings between 1963 and 1969 were analyzed to determine the relative tendency for the species to occur alone or in conjunction with other

species. Data showed that Wedge-tailed Shearwaters

associated with members of other species in 57.8

percent of the sightings, and were alone or with

other Wedge-tailed Shearwaters in 42.2 percent of

the sightings (Table 17).

To understand why more Wedge-tailed Shearwaters were seen in mixed-species aggregates than

alone, it is important to look at the behavior of the

respective groups. The categories of behavior for

which information was recorded systematically included sitting on the water, feeding, searching, following the ship, displaying, parasitism, dispersing,

and traveling. The behavior of birds at sea, however, is sometimes difficult to characterize. Searching and dispersing are closely related to feeding.

Searching implies that a flock of birds has formed

and is about to feed when schooling fish break the

surface. Dispersing implies that a flock was feeding

a short time before observation, but inability to

TABLE 17.—Sightings of Wedge-tailed Shearwaters

in association with other species and alone

Status

Associated

Unassociated

Total

Average number

Number of Number of of birds per

birds sightings sighting

47,276

34,561

81,837

3^25

14,743

17,968

14.66

2.34

4.56
NUMBER 158 65

TABLE 18.—Number and percentage of sightings in

which various species were observed feeding with

Wedge-tailed Shearwaters (n = 1285)

Species

Puffinus pacificus (alone)

Sterna fuscata

Anous stolidus

Gygis alba

Sula sula

Pterodroma externa externa

Fregata minor

Pterodroma hypoleuca nigripennis

Sula dactylatra

Puffinus puffinus neweHi

Sula leucogaster

Puffinus griseus

Bulweria bulwerii

Pterodroma externa cervicalis

Sterna lunata

Anous tenuirostris

Fregata ariel

Pterodroma neglecta

Puffinus nativitatis

Oceanodroma leucorhoa

Stercorarius pomarinus

Puffinus carneipes

Puffinus Iherminieri

Pterodroma alba

Phaethon rubricauda

Procelsterna cerulea

Stercorarius longicaudus

Diomedea immutabilis

Phaethon lepturus

Number Percentage

85

994

241

239

213

192

112

104

90

75

45

43

43

40

31

30

28

26

24

20

17

15

15

13

11

10

8

7

7

6.6

77.4

18.8

18.6

16.6

14.9

8.7

8.1

7.0

5.8

3.5

3.3

3.3

3.1

2.4

2.3

2.2

2.0

1.9

1.6

1.3

1.2

1.2

1.0

0.9

0.8

0.6

03

0.5

find more surfacing fish was resulting in disintegration of the flock. Wedge-tailed Shearwaters were

not known to display at sea, nor were they subject

at sea with any regularity to parasitic attacks by

jaegers (Stercorarius spp.), skuas (Catharacta

skua), or frigatebirds (Fregata spp.).

Wedge-tailed Shearwaters not actively involved

in any other behavioral activity were assumed to be

traveling. Thus, it is not surprising that in only

2172 sightings (12.1%) was a behavior noted other

than that of traveling.

Of behavioral categories other than traveling,

feeding was probably of greatest significance, because, next to traveling, the greatest number of

sightings were of feeding birds (1285 sightings). An

additional 295 sightings were noted as searching

and 16 were dispersing. Significant interspecific relationships can be shown best by analyzing the species content of the 1285 sightings of feeding birds.

I disregarded searching and dispersing birds in this

analysis because of the possibility that these behaviors were misinterpreted by the observers. Table 18

lists the number and percentage of sightings in

which various species were in feeding association

with Wedge-tailed Shearwaters. Wedge-tailed

Shearwaters fed without other species present only

6.6 percent of the time; 93.4 percent of the time

they fed in association with other species, especially

Sooty Terns (Sterna fuscata).

In mixed feeding flocks in the tropical Pacific

Ocean, Wedge-tailed Shearwaters and the noddies

(Anous spp.) fly lowest, usually no higher than 10

meters above the water. Boobies (Sula spp.) usually fly between 10 and 30 meters and Sooty Terns

and White Terns (Gygis alba) fly between 20 and

60 meters above water level. Frigatebirds can be

found substantially higher, perhaps as high as 120

or 160 meters. These are the approximate levels at

which these species fly during the periods when the

schooling fish are not surfacing. The longer the

periods between surfacing, the higher the Sooty

Terns and frigatebirds tend to fly, and the more

dispersed the typical feeding flock becomes. When

fish once again break the surface it is difficult for an

observer to tell which component of the flock spots

them first, but an observer quickly learns to watch

for a characteristic flash of white as the Sooty Terns

bank from horizontal flight, exposing their white

underparts against the sky, in a dive toward the

surfacing fish. It is visible to an observer perhaps a

mile or more away, appearing like snowflakes dancing on the horizon. The presence of frigatebirds

over the terns confirms the suspicion that a flock

has gathered and is or has been feeding.

Wedge-tailed Shearwaters utilize a modified

dynamic soaring technique in flight, less efficient

than the soaring of albatrosses because of higher

wing loading and lower aspect ratio. However, they

take advantage of the differentials in windspeed at

different elevations over the waves caused by surface friction, and are, therefore, more or less tied

to the air layer in which windspeed differentials are

greatest. Sooty Terns and frigatebirds, on the other

hand, either soar statically or propel themselves by

constant wingbeats, and are not tied as closely to

the surface of the water.

Sooty Terns are in a good position to act as the

"eyes" of the flock, both because they are high
66 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

above the water and because their greater abundance permits a greater area of ocean to be kept

under surveillance for surfacing fish. If human observers can take advantage of the Sooty Terns' dives

to the surface as an indication of feeding activity,

it is not unreasonable to suspect that birds do the

same. Although the behavioral pattern of Sooty

Terns may bring increased numbers of other species to the feeding area, competition for food is

probably minimal because food is superabundant

for the short periods when it is available.

The ephemeral nature of the food supply suggests that, up to a point, more, rather than fewer,

birds help to make the supply of food more readily

available. Ashmole (1963, postscript) suggested

that although tropical seabirds may be limited in

their abundance by the availability of food, their

effect on the abundance of the food organisms is

probably negligible. This is probably also true in

areas of food concentration (for example, in the

upwellings of the Peru current, where birds' search

efficiencies are undoubtedly much higher than for

tropical oceans as a whole), where breeding adaptations permit more rapid growth of offspring and

population sizes commensurate with predictable

abundance of food (see Nelson, 1968, for a comparison of breeding adaptations of boobies within

and without such an area of predictable food abundance) . Seas surrounding breeding islands in areas

without unusual food abundance may support seabird concentrations large enough to cause competition for available food resources. In the face of such

competition some species, such as Sooty Terns and

Wedge-tailed Shearwaters, can, if necessary, exploit

seas at greater distances from their breeding islands

than can others, e.g., noddies and boobies. Traveling greater distances for food places more importance on the role of search time in the species' energy budget than in birds of areas of food abundance, and the resulting breeding strategies tend to

be more conservative, e.g., fewer offspring, longer

incubation stints, and longer fledging periods.

Of significance is the relatively low percent of

participation in feeding sightings of the Sooty

Shearwater Puffinus griseus, Bulwer's Petrel Bulweria bulwerii, Leach's Petrel Oceanodroma leucorhoa, and the two tropicbirds Phaethon spp., all

of which are more abundant than is suggested by

Table 18. The first species, and its traveling companion the Slender-billed Shearwater Puffinus

TABLE 19.—Sightings of sitting birds that included

Wedge-tailed Shearwaters (n=465)

Species

Puffinus pacificus (alone)

Pterodroma externa

Anous stolidus

Puffinus puffinus newelli

Sula sula

Puffinus puffinus auricularis or P. p.

opisthomelas

Sula leucogaster

Puffinus griseus

Pterodroma hypoleuca nigripennis. .

Sula dactylatra

Number Percentage

382

34

9

7

6

4

3

3

3

3

82.2

7.3

1.9

1.5

1.3

0.9

0.6

0.6

0.6

0.6

tenuirostris, seldom stops to feed in the tropics during its transequatorial migrations. The other species

are all more or less solitary feeders.

SITTING ON WATER.—Wedge-tailed Shearwaters

frequently sit on the water during the day. Of 465

sightings of sitting birds which included Wedgetailed Shearwaters, 382 (82.2%) sightings were of

Wedge-tailed Shearwaters only. Other species most

frequently associated with Wedge-tails were Juan

Fernandez Petrels Pterodroma externa externa, and

White-necked Petrels P.e. cervicalis. These petrels,

not readily distinguished from one another on the

water, were frequently seen sitting on the water

singly and in rafts up to ten birds during the

months of June to October undergoing heavy molt.

They were frequently joined by Wedge-tailed Shearwaters. Table 19 gives the frequency with which

other species were seen to sit on the water with

Wedge-tailed Shearwaters.

Wedge-tailed Shearwaters seem to sit on the water most frequently under two conditions. The first

is in association with flocks in which individuals

have finished feeding and are resting on the water

in small rafts. The second is evidently prior to migration. Rafts of up to 700 or more Wedge-tailed

Shearwaters have been seen, mainly near the Hawaiian Islands in November when the young of the

year are fledging; the age-structure of the rafts is

not known.

FOLLOWING SHIPS.—Wedge-tailed Shearwaters

were recorded following ships 20 times. I will omit

an analysis of the other species involved in these

sightings because of the difficulty in determining if

an individual bird was actually following, or if it
NUMBER 158 67

passed aft of the ship, turned, and ran with the ship

and the other birds for a short while. Also, if the

ship provided the stimulus that led the birds to follow, then the association of the various species

would be purely accidental.

There can be no doubt, however, that Wedgetailed Shearwaters occasionally followed ships for

30 minutes or more. They followed ships most readily in November and December in the vicinity of

the Hawaiian Islands, and the birds that followed

always seemed to have very fresh plumage. They

may have been fledglings, attracted to the ship because of food smells emanating from it. Normally

Wedge-tailed Shearwaters did not follow ships, although they did not seem to avoid them as did

some other species, e.g., Sooty and Slender-billed

Shearwaters.

Summary

The Wedge-tailed Shearwater breeds on numerous islands in the tropical and subtropical Pacific

Ocean. The infrequent sightings of the species at

sea belie the fact that it is abundant and widespread. Some of its subtropical populations perform extensive migrations. Birds from the Hawaiian Islands, for example, probably migrate

south to the Equatorial Countercurrent and then

east to the coast of Middle America during their

nonbreeding season. Molt takes place during the

nonbreeding season and is nearly completed when

the birds return to the central Pacific to breed.

Tropical populations are present at sea near their

breeding islands most of the year, and may not migrate.

Consistently high densities of birds were recorded

in the vicinity of the Hawaiian Islands, in the equatorial current area between latitudes 4°S and 10°N,

and off the coasts of Middle America. Light-phase

birds were abundant in the central Pacific during

the northern summer and all but absent during the

northern winter; the cycle of abundance was reversed in the eastern Pacific. The abundance of

dark-phase birds paralleled that of light-phase birds

in the central Pacific, but alternated with lightphase birds in the eastern Pacific. Within the equatorial currents birds were most abundant near the

boundaries of the Equatorial Countercurrent.

Wedge-tailed Shearwaters are gregarious when

feeding, but more solitary when traveling. Threequarters of the sightings in which this species was

noted feeding contained Sooty Terns; Wedge-tailed

Shearwaters may rely on the conspicuous diving behavior of the Sooty Terns to help them locate food.
68 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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Appendix

Summary of published data on Wedge-tailed Shearwater distribution

Location Date Remarks Source

NORTHEAST PACIFIC

Vancouver, B. C.

EAST-CENTRAL PACIFIC

Off N Baja California

Off Manzanillo, Mexico

20°59'N, 111°57'W

19°37'N, H1°H'W

Rcvilla Gigcdos

Rcvilla Gigcdos

16°55'N, 07°23'N to

97°48'W, 112°55'W

Off Cape San Lucas.

Mexico

Off Xayarit, Mexico

Off Nicoya Peninsula,

Costa Rica

11°N, 90°55'W

Off Darien, Panama

10°18'N, 121°04'W

Clippcrton

9°46'N, 93°S0'\V

7°58'N, I08°25'W

7°N. 131 °W

7°N, 123°W

7°N, 109°W

7°N, 101°VV

7°N, 93°W

W of Panama

S of Panama

4°N, 96°30'W

3°24'N, 84°12'W

l°40'N. 86°W

l°30'N, 108c30'W

0°30'S, 120°W

NW coast of South

America

NW of Galapagos I.

Gulf of Guayaquil

6°22'S, 117°O8'W

SOUTHEAST PACIFIC

13°34'S, 103°;>9'W

23°28'S, 127O31'W

not noted hypothetical, based on 1 specimen,

questionable data

16 Dec 56 light and dark seen

24 Oct 55 8

23 Jul 05 a few

2"> Jul 05 common

not noted thousands

not noted breeds

28 Scp-18 Oct seen daily

05

not noted recorded

not noted recorded

8 Fcb 38 3 specimens, 20 miles S of Cabo

Blanco

17 Nov 56 many, all light

5 Mar 41 2 specimens at sea 5 km NW of

Enscnada, Guayabo

13 Oct 55 came aboard ship

not noted 3 specimens, 7 seen in caves and on bank

of lagoon

6 Dec 56 seen

27 Oct 55 I

9 Nov 60 25 dark, 1 pale

10 Nov 60 1 dark

12 Xov 60 1 dark, 3 pale

13 Xov 60 2 dark

14 Xov 60 10-20 dark and 10-20 pale

not noted seen

not noted seen

25 Apr 64 1 of this species or P. natwitatis

23 Nov 58 1

3 Sep 56 3

27 Apr 64 1 of this species or P. natwitatis

29 Apr 64 1 of this species or P. nativitatis

not noted occurs regularly

7 Aug 62 1 specimen

14 Mar 62 seen in numbers, light phase

23 Nov 57 1 light, probable

29 Mar 50 2 possibles, dark

9 Jul 48 3 possibles, dark

Godfrey, 1966:23

Murphy, 1958:104

King and Pylc, 1957:35

Loomis, 1918:142

Anthony, 1900:250-251

Brattstrom and Howcll, 1956:111-112

Loomis, 1918:142

Blake, 1953:10

Slud, 1964:31

Murphy, 1958:104

Wctmore, 1965:42

King and Pylc, 1957:35

Loomis, 1918:142

Murphy, 1958:104

King and Pylc, 1957:35

Morzcr Bruyns, 1965:58

Harrison in Bourne, 1959:13

Mitchell in Bourne, 1966:19

Leveque, ct al., 1966:84

Mitchell in Bourne, 1966:19

I^veque. et al., 1966:84

Lcvequc, 1964b:53-54

Gibson. 1960:16

Laird, 1951:176-177

Fleming, 1950:175

92
NUMBER 158 93

Summary of published data on Wedge-tailed Shearwater distribution—Continued

Location Date Remarks Source

NORTHWEST PACIFIC

Off Izu I. not noted not uncommon Austin and Kuroda, 1953:305

WEST-CENTRAL PACIFIC

Bonin and Volcano I. not noted

Marcus

Pescadores

Pescadores

Philippine Sea

15°57'N, 113°12'E

Philippines

Marianas

Marianas

Marianas

Carolines

7°N, 141°E

7°N, 150°E

7°N, 157°E

7°N, 157°E

10°S, 151°30'E

Off S coast of New

Guinea

New Guinea

New Guinea and

Celebes

Solomons

not noted

not noted

not noted

Apr 52

10,15,28 Jan 61

not noted

22 Aug 45

Jan-Fcb 46

not noted

not noted

29 Oct 60

30 Oct 60

31 Oct 60

1 Nov 60

4 Oct 63

3 Oct 63

not noted

Jul 29

not noted

"Comes to land in late Mar. or Apr., some

remaining until end of Nov. After breeding, a few stray northward to the waters

off Japan."

may still breed

seen in May

breeds

this species or P. carneipes, sometimes in

large numbers

probables seen

a few stragglers

flocks of 21 and 41 (dark-bellied?) 100

miles S\V from Sariguan, Marianas

white-bcllicd birds, possibly this species,

off southern Marianas

breeds Aug

breeds

tlark phase in numbers up to 10

up to 6 dark at Helen Shoal

1 dark at Ngatik I.

0 dark N of Kusaie I.

several

1

1

this species or P. carneipes, very numerous from X point of Celebes, easterly

toward the waters N of New Guinea

breeds

King, 1967:118

Cheng, 1955:6

Murphy, 1951:9

MacUonald and Lawford, 1954:19-20

Mitchell »>i Bourne and Radford, 1962:16

Dclacour and Mayr, 1946:21

Dixon and Starrett, 1952:269-270

Baker, 1951:65

Murphy, 1951:2

Morzcr Bruyns, 1965:58

Mitchell in Bourne, 1965:19

Rand and Gilliard, 1967:29

Jespersen, 1933:196

Murphy, 1951:2

SOUTHWEST PACIFIC

I7°S, 158°E

Near New Caledonia

23°46'S, 151°18'E

New Caledonia

New Caledonia

26°16'S, 161°24'E

27°3O'S, 154°30'E

30°55'S, 155°17'E

lasnian and Coral Seas

East Australia, Lord

Howe and Norfolk I.

Off Sydney, Australia

Off Sydney, Australia

37°41'S, 134°E

Makara, New Zealand

1

well represented

$ probables, dark

several, all dark

breeds

usually 1 or 2 in sight

24 Oct 63

18 Dec 57

16 Nov 61

Nov 28

not noted

19 Dec 57

26 Oct 63 2

20 Dec 57 some in sight all day, once in hundreds

Aug 61-Scp 62 numerous dark-phase sightings

not noted breeds Sep to Dec

21 Dec 57 seen

27 Oct 63 2

19 Apr 57 1 dark

26 Jan 62 1 specimen, white-breasted

Mitchell in Bourne, 1965:19

Gibson, 1960:18

Semple in Bourne and Radford, 1962:16

Jespersen. 1933:1%

Delacour, 1966:20

Gibson, 1960:18

Mitchell in Bourne, 1965:19

Gibson, 1960:18-19

Norris, 1967:37-38

Mathcws and Iredale, 1921:26

Gibson, 1960:19

Mitchell in Bourne, 1965:19

Gibson, 1960:12

Falla, 1962:278-279

CENTRAL PACFIC

N, E, and W of

Hawaiian I.

Feb 64-Jun 65 Abundant Mar-Nov, uncommon Dcc-Feb King. 1970:25
94 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Summary of published data on Wedge-tailed Shearwater distribution—Continued

Location

Hawaiian I.

Hawaiian I.

Off Pearl Harbor, Oahu

150 to 350 miles WSW

of Johnston Atoll

Off Oahu

Wake

13°S0'N, 180°

Marshalls

9°55'N, 164°48'W

9°43'N, lM°5lrW

9°04'N. 143°49'W

Christmas I.

7°N, 179°E

7°N, 180°

7°N, 166°W

7°N, 152°W

7°N, 146°W

7°N, 138°W

(N of Marquesas )

6°N, 153°W

Jaluit

Phoenix

4°-02°30'S, 169°-155°E

Marquesas

SOUTH-CENTRAL PACIFIC

New Hebrides

11°S, 177°W

11°S, WW W

Samoa

Samoa

Tonga

14°30'S, 176°E

14°47'S, 170*35^

Fiji

Fiji

Tuamotus

Henderson

16°S, 178°W

16°09'S, 176°42'E

17°57'S, 169°52'E

Society

18°28'S, 172°48'W

19°30'S, 177°3O'E

19°30'S, 178°E

2O°O2'S, 175°01'W

Near Papeete, Tahiti

Near Fiji

24°S, 166°30'E

25°S, 176°30'E

Australs

Date

27 Apr 45

28 Apr 45

29 Apr 45

not noted

24 Dec 61

30 Apr 45

24 May 59

not noted

1 May 45

not noted

26 May 59

6 Oct 55

4 Oct 55

not noted

3 Nov 60

4 Nov 60 (E)

4 Nov 60 (W)

6 Nov 60

7 Nov 60

8 Nov 60

9 Dec 63

2 Nov 60

not noted

Oct 51

not noted

not noted

30 Mar 63

8 May 64

Nov 28

not noted

not noted

16 Nov 63

27 Feb 63

not noted

Nov 28

not noted

not noted

10 May 64

9 Dec 57

10 Dec 57

not noted

6 Dec 57

12 May 64

2 Feb 63

25 Feb 63

28 Nov 57

24 Mar 59

14 May 64

3 Feb 63

not noted

Remarks

11 S of Oahu

14 S of Oahu

5 near Johnston Atoll

breeds May-Nov

200 light, 3 dark

33

5

migrant (bred formerly)

2

breeds

8 of this species or P. carneipes

flock of 20

came aboard ship

breeds Feb-Nov

two groups of 200 dark

2 dark

2 dark

6 pale

3 dark

110 dark, 1 pale

1

10 dark

breeds all months

small numbers of this species or P. carneipes between Niutao Atoll and the

Admiralty I.

breeds

breeds Jan-Jun

3

1 of this species or P. nativitatis

several, all dark

breeds

breeds

several

1 in hand

breeds

several, all dark

breeds

breeds

1 of this species or P. nativitatis

occasional

seen

breeds

small flock, dark birds, 1 light

1 of this species or P. nativitatis

I probable

1 in hand

dark birds seen, possibly this species

seen

several

1 probable

breeds

Source

Cogswell, 1946a:47

Cogswell, 1946a:47-48

Cogswell, 1946a:48

Richardson, 1957:16

King in Bourne, 1964:19

Cogswell, 1946a:48

Peakall, 1960:199

King, 1967:111

Cogswell, 1946b:53

Amerson, 1969:295

Peakall. 1960:199

King and Pyle, 1957:35

" " "

Schrciber and Ashmole, 1970:368

Mdrzer Bruyns, 1965:58

" " " "

" »

" " •• "

" " •• »

Mitchell in Bourne, 1965:19

Mdrzer Bruyns, 1965:58

King, 1967:93

MacDonald and Lawford, 1954:19

Murphy, 1951:2

King, 1967:105

Morris in Bourne, 1965:19

Mitchell in Bourne, 1966:19

Jespersen, 1933:195-196

Murphy, 1951:2

Davidson, 1931:217-218

Mitchell in Bourne, 1965:19

Jenkins in Bourne, 1965:19

Murphy, 1951:2

Jespersen, 1933: 196

Murphy, 1951:2

>. >.

Mitchell in Bourne, 1966:19

Gibson, 1960:18

» »

Murphy, 1951:2

Gibson, 1960:17

Mitchell in Bourne, 1966:19

Morris in Bourne, 1965:19

Jenkins in Bourne, 1965:19

Gibson, 1960:17

Dixon in Bourne, 1959:11

Mitchell in Bourne, 1966:19

Morris in Bourne, 1965:19

Mnrnhv IQR1-9
NUMBER 158 95

Summary of published data on Wedge-tailed Shearwater distribution—Continued

Location Date Remarks Source

26°15'S, 176°56'W 14 Mar 47 50-60 Fleming, 1950:172

26°28'S, 176°32'W 15 Mar 47 scattered group of 15 " " "

30 °S, 175°30'E 4 Fcb 63 1 probable Morris in Bourne, 1965:19

Kermadecs not noted breeds Oct-early Jun Falla, et al., 1%7:42

Kermadecs not noted breeds Dec-May Sorensen, 1964:70

33°S, 176°30'E 5 Jun 63 2 Morris in Bourne, 1965:19
Black-footed Albatross (Diomedea nigripes)*

Gerald A. Sanger

Introduction

The material contained in this report is a summary of all at-sea observations of the Black-footed

Albatross (Diomedea nigripes) by the POBSP in

the central and eastern Pacific Ocean. Literature

records, scattered northern Pacific POBSP records,

and data obtained from POBSP island surveys are

included for general background information.

Humphrey (1965) gave a general summary of the

objectives of the program and Gould summarized

the areas surveyed and the methods and materials

used in data collection and analysis. The reader is

referred to these papers for more details.

The Black-footed Albatross is probably the most

often seen and best known of the truly pelagic

northern Pacific birds. It has been the subject of

more papers on distribution and habits at sea than

any other northern Pacific seabird. In recent years,

intensive research relating to albatross interference

with aircraft operation at Midway Atoll has been

conducted. While the breeding grounds research

has been most fruitful (Rice and Kenyon, 1962a,

1962b; Robbins, 1966), the at-sea studies, because

of their general lack of temporal and seasonal

scope, have given only general ideas of the overall

distribution and ecology.

Rice and Kenyon (1962a: 383) conservatively

estimated the world's population of Black-foots at

300,000 birds during the period 1956-1958. Robbins (1966:9) noted a sharp decrease in the nesting

population at Sand Island, Midway Atoll, through

1963, but felt that there was not enough informaGeiald A. Sanger, National Marine Fisheries Service, Northwest Fisheries Center, 2725 Montlake Blvd. East, Seattle,

Washington 98112.

tion available on prebreeding and older "unemployed" ( = not breeding) birds for a direct comparison with Rice and Kenyon's 1957-1958 population estimate.

BREEDING.—The Black-footed Albatross breeds

mainly in the leeward Hawaiian chain (Rice and

Kenyon, 1962a). A small colony (ca. 20 birds) exists

on Torishima, in the Izu Islands, south of Honshu,

Japan (Aronoff, 1960).

The leeward Hawaiian Islands support breeding

Black-footed Albatross populations as shown in Table 20. The breeding cycle (see Rice and Kenyon,

1962b) is nearly identical from island to island and

from year to year. Table 21 summarizes this information. Breeding birds begin returning to their

islands late in October. Eggs are laid between the

middle of November and the first week of December; they are incubated for 66 days, and most of

the chicks have hatched by the end of January. At

TABLE 20.—Largest numbers of breeding Blackfooted Albatross populations (all derived from

POBSP data except for Kaula, which is from

Rice and Kenyon, 1962a: 377)

Location

Kure

Midway

Pearl and Hermes Reef

Lisianski

Laysan

French Frigate Shoals

Necker

Nihoa

Kaula

Number of birds

1,150"

24.000*

9,000'

4,000b

40,000"

3,100+'

375«

100«

50-

• Paper Number 72, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

' Recorded.

b

 Estimated.

96
NUMBER 158 97

TABLE 21.—Timing of Black-footed Albatross

activities at breeding grounds (adapted from

Rice and Kenyon, 1962b)

Activity

Arrival

Egg-laying

Incubation

Hatching

Departure of fledged chicks

Period

6 Oct-6 Nov

3 Nov-SO Nov

peak - 21 Nov

x—65.6 days

15 Jan-7 Fcb

peak=25-26 Jan

Juii-inid-Jul*

•Parents cease visiting breeding grounds when chicks are

fledged, but no sooner.

least one parent is present with the chick continuously through mid-March, when the guard state

terminates. During April and May breeding birds

are mostly at sea and return only briefly to feed

fledging young, liy June only young birds are present all day; breeding adults return only long

enough to feed their young. Most young have

fledged and departed the islands by the middle of

July, and toward the end of July all birds are at

sea.

SUMMARY OF PUBLISHED PELAGIC OBSERVATIONS.

—The Black-footed Albatross is an abundant and

commonly seen species throughout much of the

northern Pacific Ocean. At sea it ranges from the

coasts of China, Japan, and Russia eastward to continental North America, and from the southern

Bering Sea and the Gulf of Alaska southward to

18°N off North America, occasionally to 10°N in

the central Pacific, and to 19°N off Asia.

The appendix summarizes published data on

Black-footed Albatross distribution. Papers on observations from the eastern half of the northern

Pacific outnumber those on other areas by a wide

margin; a few of these papers warrant discussion.

McHugh (1955) made a detailed analysis of

Black-foot distribution off North America in 1949-

1950. In 1949 a progressive northerly distributional

shift occurred in the spring. The population center

lay relatively close to shore off southern California

in March, close to shore north of San Francisco in

April, and off Oregon and Washington in May,

when the center showed a tendency to withdraw

from the coast and to disperse over a larger area.

Summer months generally showed a decrease in

number of birds, and a somewhat irregular distribution. Birds were present in low to moderate density (x = 11-20 birds/sighting, from stopped ship)

in an area off the southern California Channel Islands in August, resulting in the highest abundance of the year there. In October there was a

high overall density of birds, with a broad, heavy

concentration some 200 miles off southern Oregon

and northern California. By November the population center had shifted southward far off central

California, and overall density had diminished considerably. The 1950 distribution patterns were not

clear, but the abundance peak for the entire area

was in Mardi; there was evidence of a southerly

shift of heavy concentrations of Black-foots from

southern Oregon-northern California in May, to

central California in June.

In the period June-September of 1937 and 1938,

Black-footed Albatrosses were concentrated in a

cold tongue of water off the California Channel

Islands (Miller, 1940). There were commonly 12-

15 birds at oceanographic sampling stations in the

cold tongue, but never more than five or six at stations outside this area. None were seen in the Santa

Barbara channel. Miller (1942) showed that most

Black-foots followed his ship for only a few miles.

Of 25 birds marked with paint, 12 followed the

ship for 20 miles, seven for 30 miles, three for 40

miles, and only one for 60 miles.

In 1945 Thompson (1951) observed the distribution of D. nigripes between Pearl Harbor, Hawaii,

and San Francisco, California. Most months showed

an increase in abundance as the California coast

was approached, except in June, when there was

fairly even pelagic distribution, and late November,

which showed a bimodal distribution with peaks at

ca. 125°W and 150°W, and minimums at 140°W

and 155°W. There appeared to be an inverse correlation between surface water temperatures and

albatross numbers. This easterly increase was associated with passing from the North Pacific Central

Water (Sverdrup, et al., 1942) into the California

Current between 130°W and 155°W. The maximum number of birds seen at any one time was 45

at 130°W in October. A parallel increase in albatross and jellyfish abundance was observed, which

Thompson (1951) believed was a similar response

of the two organisms to the same environmental

conditions.

The Black-footed Albatross was the most com-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

monly seen and abundant species during seven

cruises off Washington and Oregon in 1964-1965

(Sanger, 1970). They were present on 94 percent of

the 88 days spent in the area and accounted for 53

percent of all birds seen. Maximum abundance and

occurrence were in the summer, and minimums

were in the winter. Peak abundance occurred in

August 1965 when albatrosses were 2.5 times as

abundant as in the previous August. Minimum

abundance was in January 1965. Generally, numbers increased with distance from shore, although

the maximum number seen at a single sighting

(78) occurred just 40 miles off northern Washington

in August 1965. Generally there was no difference

in abundance or distribution between the areas off

Oregon and Washington. For data lumped for all

seven cruises there was a general increase in abundance with air temperature and surface water

temperature (range: 6°-18°C.). There was no observed relation between albatross numbers and surface salinity, with birds found in salinities ranging

from greater than 33 parts per thousand (%«,) far

offshore to 15%o just off the mouth of the Columbia

River. There appeared to be no relationship between albatross numbers and rate of primary productivity, although the largest number of birds in a

single sighting (78) occurred in water with the highest primary productivity rate of all cruises. These

data have been incorporated with the POBSP records

and are included on the distribution maps.

The literature suggests that Black-footed Albatrosses are less abundant, or less frequently encountered, in the western than in the eastern Pacific.

For example, Starrett and Dixon (1946) noted a

general absence of albatrosses from the southwestern

portion of their range between June 1945 and February 1946, and MacDonald and Lawford (1954)

noted that flocks of Black-foots were generally

smaller in the western Pacific than the eastern Pacific in 1951 and 1952.

ACKNOWLEDGMENTS.—In addition to the many

cooperators mentioned by Gould (p. 5 herein), a

number of other people gave significant aid with

this paper. Warren B. King, Robert L. Pyle, and

especially Patrick J. Gould, offered useful advice

on early drafts. Elizabeth Anthony and Charles

Sklar assisted in analyzing the CalCOFI data,

which was made available to the Pacific Program

through the generous cooperation of Carl L.

Hubbs and Robert L. Wisner of the Scripps Institution of Oceanography. Furthermore, the mass of

CalCOFI data, which is the single most intensive

pelagic record ever assembled for the species, would

not have been possible without the cooperation of

the many CalCOFI sea-going personnel who diligently recorded the sightings. Among these were

Robert Counts, David Kramer, James Thrailkill,

and Andrew Vrooman, all of the National Marine

Fisheries Service, La Jolla, California. To all

of these people I express my sincere appreciation.

Distribution and Abundance

SPECIMEN RECORDS

Table 22 summarizes Black-footed Albatrosses

collected at sea by POBSP personnel. Most were

from the central Pacific; a few were from the western Aleutians and the coast of southern California.

SIGHTING RECORDS

Figures 66-77 (pp. 114—125) are monthly maps of

the average Black-footed Albatross distribution for

January 1964 through November 1967. Relative

abundance, i.e., average number of birds per sighting for each day, is indicated by different degrees

of shading. Because of the ship-following habits of

the Black-footed Albatross and a consequent disparity in field recording techniques for this species,

it was impossible to estimate the actual abundance

in the standard units of birds per linear mile of

travel. The disparity in field recording techniques

was mainly a failure of observers to record the number of birds at set time intervals; some observers

recorded hourly counts and others recorded at

irregular intervals, or whenever the Black-foot density changed. However, the relative abundance was

determined by using a unit of mean number of

birds per sighting (BPS) for each day the species was

seen, thus eliminating discrepancies in abundance

due to variations in recording techniques.

Three principal areas received consistently good

seasonal coverage of Black-footed Albatross distribution: the central Pacific, off the southern California coast to about 126°W, and off the coasts of

Washington and northern Oregon to about 140°W.

Relative abundance in the former two areas is mutually comparable in every way. In the latter area,

however, many counts were made from a stopped
NUMBER 158

TABLE 22.—Black-footed Albatross specimens collected at sea by POBSP personnel

Location

47°18'N,173°13'E

47°03'N, 173°16'E

33°23'N,122°18'W

33°23'N, 122°18'W

21°23'N,167°37'W

20°58'N,158°06'W

20°56'N,158°33'W

20°49'N,158°52'W

20°23'N,161°07'W

19°28'N, 162°11'W

18°2S'N,165O12'W

18°01'N, 166°H'W

17°20'N,164°12'W

16°50'N, 169°50'W

16°38'N, 169°38'W

14°46'N,160°44'W

12°20'N,167°41'W

USNM

number

503266"

503267"

497772'

497773d

496723

493513

492911

492910

lost

493917

494145

496198

493819

495791

493512

494144

495792

Sex

_

-

9

9

9

9

S

9

9

9

9

S

9

$

S

9

Body weight

(gm)

3110++

3110+ +

-

-

2527

2802

3200

2100

2533

2900+

_

-

2610

-

2857

3000 +

2006

Gonad size

(mm)

_

-

18 x 8

18 x 8

20 x 10

23 x 15

26 x 17

30 x 14

19 x 11

25 x 17

45 x 35

27 x 5

20 x 4

22 x 25

-

14i/2x7i/2

16 x 6

11 x 6

15 x 10

Date

9 Oct 65

9 Oct 65

21 Jan 67

21 Jan 67

22 May 65

3 Jan 64

3 Dec 63

3 Dec 63

4 Jan 64

4 Feb64

9 Dec 64

9 Dec 64

6 Jan 64

15 Jan 65

12 Feb 64

8 Mar 64

22 May 65

Collector

R. DeLong

R. DeLong

B. Harrington

B. Harrington

D. H usted

-

R. Fleet

R. Fleet

-

V. Hoeman

R. Standen

M. Thompson

C. Kepler

D. H usted

-

V. Hoeman

R. Merrill

99

* Banded, U. S. Fish and Wildlife Service Number 737^*5577 (adult, sex unknown, 8 Nov 63,

Green Island, Kure Atoll).

b

 Banded, U. S. Fish and Wildlife Service Number 697-73041

1

 Banded, U. S. Fish and Wildlife Service Number 757-26257 (local, sex unknown, 12 Jun 66,

East Island, French Frigate Shoals).

d

 Banded, U. S. Fish and Wildlife Service Number 767-42423 (nestling, sex unknown, 19 Mar

63, Crass Island, Pearl and Hermes Reef).

ship, a fact that may make the counts seem large

compared to the other areas due to the increased

attraction stopped ships have for Black-foots. All

mileage figures refer to statute miles.

January Distribution (Figure 66): The densest

concentration of birds occurred in the central Pacific across a broad front at ca. 25°N, between

148°W and 157°W; however, there were no observations along the leeward Hawaiian Islands.

Black-foots occurred in most of the area off California farther than 75 miles off the coast, and in

areas farther than 100 to 200 miles off the coasts of

Oregon and Washington.

February Distribution (Figure 67): In the central

Pacific, birds were seen in fair numbers as far south

as 11°N, 151 °W, although they were peculiarly

absent a few longitudinal degrees in either direction. Concentrations were still found across the

front at 25°N; no observations were conducted in

the Leewards. Scattered birds were seen south to

13°N, 170°W, although there was a conspicuous

absence of Black-foots at similar latitudes between

153°W and 168°W. Off California, overall densities decreased from January; a few birds were observed within 30 miles of the coast. Scattered birds

were seen between northern Washington and 53 °N

in the Gulf of Alaska; these sightings apparently

represent the northernmost winter records for the

species.

March Distribution (Figure 68): During March,

observations were extended westward along the leeward Hawaiian Islands. Correspondingly, extremely dense concentrations of Diomedea nigripes

were seen in areas near the breeding islands. A

maximum of 56 BPS was seen near Laysan Island.

No Black-footed Albatrosses were seen south of

31 °N in the area off California; a few birds were

encountered within 25 miles of the coast. No observations were conducted off Washington or Oregon.

April Distribution (Figure 69): Due to two

cruises between Hawaii and North America, cover-
100 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

age this month was quite broad in area, although

the Leewards area was not included. A localized

concentration of 10-20 BPS was found some 100

miles north of the main Hawaiian Islands, but the

bulk of the Black-foot population was seen north

of 25°N. A relatively small concentration of birds

was centered at 148°W, 28°N, but between here

and northeastward to 130°W, distribution was remarkably uniform. Off southern California, overall

densities remained essentially unchanged from

March; scattered birds were seen within 25 miles of

shore. Between the area off southern California

and Oregon, distribution is largely speculative, because noon positions were so far apart. However,

there apparently was a broad band (5° wide) of

5-10 BPS density off northern California and Oregon between ca. 127°W and 132°W, with lesser

densities to either side. The densest concentrations

this month occurred off Washington and northern

Oregon.

May Distribution (Figure 70): The most evident

feature of May distribution in the central Pacific

was the continued northward withdrawal of the

population to 20°N. A lone bird was encountered

at ca. 13°N. Concentrations were centered at French

Frigate Shoals, and some 450 miles northwest of the

main Hawaiian Islands. Distribution off California

was quite uniform at 2-5 BPS across most of the

area. There were no observations off the Washington-Oregon coasts.

June Distribution (Figure 71): A continued

northward withdrawal of the population in the

central Pacific was evident this month; the southern

limits were at 21 °N, 160°W, although two widely

scattered individuals were seen at the 16°N parallel.

The species was observed along the Leewards as

far west as Lisianski Island. Off southern California, the overall density diminished greatly. A bimodal distribution was evident off Washington and

Oregon, with concentrations of birds found relatively close to shore off northern Oregon and 400

miles off northern Washington.

July Distribution (Figure 72): The Black-foot

population continued to move northward, with

28° N marking the southern range limits. Ten to

twenty BPS densities were seen some 1000 miles due

west of San Francisco, with an apparent density decrease toward the southern California coast. A bimodal distribution was noted off southern California. Concentrations of 10 to 20 BPS were seen

within 75 miles of the coasts of Washington and

Oregon.

August Distribution (Figure 73): In the central

Pacific, Black-foots were found still farther north

than during the previous months. Overall abundance off southern California declined slightly. Diomedea tiigripes was very abundant off the Washington and Oregon coasts; about half of the region

was populated with birds in 10 to 20 BPS densities

and a general increase in abundance with distance

from shore was noted.

September Distribution (Figure 74): In the central Pacific two widely separated individuals were

sighted near Midway Atoll and at 04°S0'N, 174°W;

the latter sighting is the southern record for the

species, excluding the two strays in the southern

hemisphere (Oliver, 1955:181). Overall abundance

off southern California decreased markedly; a few

Black-foots were seen within 20 miles of shore. A

region near the western Aleutians was censused this

month and low concentrations were encountered

over most of the area. There was no observation

off the Washington-Oregon coast.

October Distribution (Figure 75): Only one Diomedia nigripes was found in the central Pacific this

month, near Gardner Pinnacles; however, areal

coverage was scanty. Farther north, among and

south of the western Aleutians, low densities were

still encountered over most of the area. Overall

abundance off Washington and Oregon diminished

markedly from August, and Diomedea nigripes

numbers were distributed erratically in the region

off southern California.

November Distribution (Figure 76): The species

had again returned in some numbers to the central

Pacific area, south to 19°N. There was a pronounced decrease in overall abundance off California, while the region off Washington and Oregon

showed an increase in Black-foots between 134°W

and 139°W.

December Distribution (Figure 77): The population level in the central Pacific increased to an

observed all-time high this month. As would be

expected, maximum concentrations were found

among the leeward Hawaiian breeding islands. Off

California, overall density showed an increase over

November, and two days of observations off the

Washington-Oregon coast revealed a few birds off

Oregon but none within 50 miles of the Washington coast.
NUMBER 158 101

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FOOTED ALBATROSS DATA

OF BLOCKS (AFTER McHUGH,1955)

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FIGURE 58.—Location of area blocks for analysis of CalCOFI Black-footed Albatross distribution.
BLOCK 10

BLOCK 13

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1957 1958 1959
NUMBER 158 103

BAND RETURN INFORMATION

Robbins and Rice (pp. 232-271 herein) made a

detailed analysis of at-sea band returns of Blackfooted and Laysan albatrosses including POBSP records. No young Black-foots were captured in the

leeward Hawaiian Islands during their first winter

of life, but some were captured within a couple of

hundred miles of both Japan and the United

States. As the birds grew older (through their

fourth summer), there was an increasing tendency

for band recoveries to occur farther north and east

in summer, and closer to the Leewards breeding islands in winter. Once the birds reached breeding

age, there was only a slight tendency for more recoveries to occur off North America in summer

than off Japan. The relative chances of a tagged

bird being caught in either area are unknown.

There are a number of POBSP band returns from

various breeding islands from birds that were

originally banded on other breeding islands. Thus,

this species exhibits some interisland movement;

the individuals involved are probably prebreeders.

DISTRIBUTION OFF CALIFORNIA AND

BAJA CALIFORNIA, 1951-1959

In 1949, an interagency oceanographic research

program known as the California Cooperative

Oceanic Fisheries Investigations (CalCOFI) "was

established as a broad and thoughtful inquiry into

the environment and the biology of the California

Current system" (Ahlstrom, et al., 1967:5). As a

regular part of routine survey cruises, the number

of Black-footed Albatrosses congregating around

the ships was counted at each sampling station.

Black-foot distribution has been analyzed for only

the first two years of these data (McHugh, 1955),

although the albatross counts continued through

April 1959. Data subsequent to 1950 are analyzed

and discussed here for the first time.

McHugh's (1955) method of analyzing the data

was, for the most part, used herein. The survey

area was divided into the same series of blocks

(Figure 58), and the monthly average of the number of Diomedea nigripes counted at each station

«*-

FIGURE 59.—Real time graphs of the BPSt for inshore

blocks: a, 1951-1953; b, 1954-1956; c, 1957-1959. (Numbers

on graphs indicate number of stations contributing to BPSt.)

within a block was calculated as mean number of

birds per station (BPSt), using the maximum number of birds seen at any one time during a station

and including "zero counts." McHugh (1955) discusses the reasons for averaging the counts from

stations within the blocks, rather than considering

individual counts at each station. An atlas-type

presentation of monthly distribution maps such as

McHugh (1955) used would be impractical in this

paper because of the large amount of data involved.

Therefore the blocks were divided into three northsouth strips, inshore (blocks 4, 7, 10, etc.), intermediate (blocks 5, 8, 11, etc.), and offshore (blocks

6, 9, 12, etc.). The seasonal changes in abundance

within individual blocks have been analyzed, as

well as changes within the entire strips.

SEASONAL CHANGES IN ABUNDANCE WITHIN AND

AMONG INDIVIDUAL BLOCKS.—Seasonal fluctuations

in birds per station were examined in blocks with

the most intensive coverage. These were blocks 10,

13, and 16 in the inshore strip, and 11, 14, and 17

in the intermediate strip. Blocks 12 and 15 in the

offshore strip were also considered in this manner

because of their proximity to the other blocks, although their coverage was poor. Real time graphs

of the BPSt in the inshore blocks are presented in

Figure 59, in the intermediate blocks in Figure 60,

and in the offshore blocks in Figure 61. In the inshore blocks (10, 13, 16) a north-south density cline

is quite evident, as are seasonal cycles in abundance, with peak numbers occurring in late springearly summer, especially in block 10. A study of

the intermediate blocks (11, 14, 17) shows that Diomedea nigripes was generally more abundant there

than closer inshore. Also evident during most of

the period is a north-south population cline (regardless of year or season) and seasonal abundance

cycles, with maximum numbers occurring in late

spring and early summer. Figure 61 indicates that

the highest numbers of Black-footed Albatrosses in

the entire area may have occurred farthest off the

coast. However, the scanty coverage, both in time

and in number of stations, precludes direct comparisons with the blocks closer to shore.

OVERALL DISTRIBUTION AND ABUNDANCE.—Temporal changes in albatross abundance within each

of the north-south strips are presented as contoured density real time diagrams (Figure 62) . By

simultaneously examining the diagrams for all

three strips it is possible to see changes in distribu-
20-

lfr

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BLOCK 11

* BLOCK 14

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1951 1952 19b3

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1957 1958 1959
NUMBER 158

BLOCK 12

105

J F M A M J j A S O N 0 J F M A M JJASOHDJFMAMJJASON D

•1951 -1952 -1953

*195 4 * 1955 "1956

ol95 «

FIGURE 61.—Real time graphs of the BPSt for offshore blocks 1951-1956 and 1958.

(Numbers on graphs indicate number of stations contributing to BPSt.)

tion and to infer movement among the three areas.

There are a number of salient features to the distribution and abundance evident in each of the strips.

Inshore Strip (upper diagram in Figure 62):

Seasonal cycles in abundance are apparent for most

years, especially north of Point Conception, California. Black-foots occurred in concentrations of 5 to

10 BPSt mostly between April and July; other

months they were absent, or present in concentrations of 5 BPSt or less. Off southern California they

were generally absent most of the year, but a few

birds showed up sporadically. The year 1958 was

unique in that Black-foots occurred in this area continuously from March through September (except

for June), although mostly in densities of 1 BPSt or

less. In strong contrast, Black-foots occurred during

most months north of Point Conception and off

northern Baja California.

Concentrations as high as 10-20 BPSt occurred

only north of Point Conception; indeed, south of

here densities of 5 BPSt or less occurred most of the

time. Also quite evident each year was an absence

FIGURE 60.—Real time graphs of the BPSt for intermediate*

blocks: «, 1951-1953; b, 1954-1956; c, 1957-1959. (Numbers

on graphs indicate number of stations contributing to BPSt.)

of birds between 24°N and 30°N in late summer or

early fall. This could be due to either a northward

migration, or a progressive northward withdrawal

to seaward from these latitudes. This phenomenon

culminated in a complete withdrawal from the inshore strip in the fall and winter of 1952-1953

and 1955-1956.

Intermediate Strip (middle diagram in Figure

62): The most striking feature here is that Blackfooted Albatrosses were continuously present in at

least part of this zone for the entire 100-month

period (no stations were occupied in October and

November 1956). There appeared to be a trend for

maximum density to occur between April and July,

although in 1955 Black-foot densities of 10-20 BPSt

lingered until October north of 32°N. Relatively

few birds were found in the strip in August through

March. Densities of greater than 10 BPSt were rarely

encountered south of ca. 32°N; when they did occur, usually as somewhat anomalous groups, it was

from June through August (e.g., at 30°N in August

1952 and June-July 1954). Evident in most years in

varying degrees was an exodus from, and return to,

the area south of 30° N, from late summer to early

winter in the same manner as in the inshore strip.

This movement generally started in September

south of 25° N and progressed northward to 30°N,
J FMAWJ J ASOMDIF H » H i 1 » j 6 » 6

SlPO t PE R STA T

• E23 ED • •
NUMBER 158 107

where it peaked in October or November. In December and January low numbers of Diomedea

nigripes returned to the southern end of the strip

but another brief evacuation from the southernmost degrees usually followed. This phenomenon

occurred every year for which data are available,

except 1958-1959.

At or south of 25°N anomalous patches of 5-10

Bpst densities frequently occurred from June

through August; examples of this were observed in

July-August 1953, June 1955, June-July 1956, and

June 1957.

Offshore Strip (lower diagram, Figure 62): As

seen in the figures, coverage in the offshore strip

was quite spotty compared with those closer to

shore, but a few salient features of distribution and

abundance are evident. Densities of more than 20

upst occurred with greater frequency in this strip

than in either the inshore or the intermediate zones.

There also seems to be a tendency for high densities to occur farther south in this strip than in the

other two. These high densities occurred quite erratically, and with no apparent evidence of the cycles which were displayed in the other two strips.

Discussion: South of Point Conception, the relative abundance among the three strips indicates a

general increase in abundance with distance from

shore, but north of here there is no consistent pattern. A more uniform pattern of distribution among

the strips is evident, and sometimes there is even a

decrease in abundance with distance from shore.

Indeed, north of Point Conception, maximum

densities among the strips occurred within the inshore strip in June and/or July of 1952, 1953, 1955,

and 1956.

ABUNDANCE AT WEATHER STATION Victor

Personnel aboard the USCGC Winnebagq kept a

record of albatross numbers seen while the ship was

positioned at Ocean Weather Station Victor (34°N,

164°E) from 26 February through 19 March 1967.

Figure 63 presents the results of this record. The

most birds seen at any time during the day (upper

graph) ranged from a low of 2 on 17 March to highs

FIGURE 62.—Contoured density real time diagrams of BPSt

in inshore, intermediate, and offshore blocks: a, 1951-1953;

b, 1954-1956; c, 1957-1959.

of 31 birds on 1 March and 30 birds on 12 March.

There appeared to be a cycle in numbers of birds,

changing from low to high numbers at 5-7-day intervals. The bottom graph of Figure 63 shows that

the maximum number of birds usually occurred in

the afternoon (1600), but never occurred in the

morning (0800).

Analysis of Distribution

GENERAL CONSIDERATIONS

Two major trends in the distribution of Blackfooted Albatrosses are evident. First, there is a major latitudinal population shift coincident with the

breeding season, i.e., the birds are in the southern

part of their pelagic range in winter (breeding season), and in the northern part of their range in

summer (Figure 64). This is especially evident in

the central Pacific. However, because there is considerable spatial overlap between the two ranges,

and some birds are well north as early as April and

as late as October, there are Black-foots throughout

most of the absolute range at any given time of the

year. Secondly, the evidence suggests that this species is predominantly an eastern Pacific bird, although a part of the population regularly occurs

west of 180°. For example, the numbers of birds

seen in single sightings in the northeastern Pacific

are far in excess of similar counts for the northwestern Pacific. Examples of this are: 70 birds 40

miles off San Francisco Bay (McHugh, 1950); 125

birds some 1000 miles southwest of San Francisco,

and 53 Black-foots 465 miles off Oregon (Yocom,

1947), 78 birds 40 miles off northern Washington

(Sanger, 1970); and 100 Black-footed Albatrosses at

Unimak Pass in the Aleutians (ca. 165°W, 54°N)

(Arnold, 1948). Although similar counts for the

western Pacific are scarce, those available show far

lower numbers; Kuroda (1955) saw a maximum of

11 birds 240 miles east of Hokkaido during his summer observations, and Wilhoft (1961) had a maximum cumulative daily total of only 70 birds, some

100 miles northwest of Luzon in the Philippines.

Furthermore, a general scarcity of Black-foots has

been noted in the western Pacific at various seasons

(Starrett and Dixon, 1946; Aronoff, 1960). TransPacific observations (MacDonald and Lawford, 1954;

Nakamura, 1963) have revealed generally more

Black-foots in the eastern Pacific than in the west
108

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

30

25

20

15

10

(A)

Birds seen at

.... 0800hours

— 1200 hours

— —1600 hours

26 27 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

February March

1967

FIGURE 63.—Fluctuation in Black-footed Albatross numbers at Ocean Weather Station Victor

(WOCN. 164°00'E).
Seasonal Variation in the Range of

Black-Footed Albatross

E D Summer (July)

£Z2 Winter (February)

HOE 130 150 170 170 150 130 110

FIGURE 64.—Seasonal variation in the range of the Black-footed Albatross.

TON

(although Austin and Kuroda [1953:299-300] stated

that this albatross is common off Japan from April

to November, and Hamilton [1958] observed that

in June 1955 they were more abundant between

Japan and 180° than east of there). Perhaps the

most convincing evidence that the majority of the

population prefers eastern Pacific waters is obtained from banding studies. Robbins and Rice

(pp. 237-238) reveal that band recoveries of prebreeding young showed a marked tendency to occur

in the eastern half of the Pacific in all seasons, as

did those for adults during winter. In summer, however, band recoveries of adults occurred with nearly

equal frequency off North America and Asia. The

relative chances for recovering banded birds in

these two areas of the Pacific are unknown.

SEASONAL AND MONTHLY VARIATIONS

Starting in late fall, adult birds begin arriving at

the breeding grounds. This would explain, at least

in part, the sharp reduction in the number of

Black-foots off Washington and Oregon between

August and October. The regular late summer-early

fall reduction in numbers off southern California

and Baja California may be partly due to adult

birds leaving for the breeding islands. Except for

copulation, breeding activities do not require the

simultaneous presence of both parents. "Incubation

spans" range up to 18 days, and "guard spans" last

about 21/2 days (Rice and Kenyon, 1962b). When

the guard stage ends in late February, both parents

leave the island, returning only briefly to feed the
110

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

fledging young. Thus, even during the breeding

season, about half of the breeding birds are at sea.

It is uncertain how far parents range from breeding sites, but they probably remain within 1500 to

2000 miles. Evidence to this effect is a dramatic

buildup at sea during the breeding season in areas

near the main Hawaiian Islands, some 1500 miles

east and southeast of the major breeding areas on

the Leewards. Robbins and Rice (Figure 148)

indicate a host of band returns of adult birds from

December through March between 155°E and

170°W, along the latitude of 30°N, and very few

elsewhere. This further suggests the tendency for

adults to range as indicated above. The Black-foots

that occur off Washington, Oregon, and southern

California in winter are probably largely nonbreeding immatures, but it is physically possible for the

parents to range for food as far away from the

breeding grounds as the North American Pacific

Coast and return to the breeding grounds within

two to three weeks.

Although parent birds are gathering food for the

young, and presumably for themselves, they apparently exist under a progressive nutritional deficit

during the breeding season. Frings and Frings

(1961) noted that the weight of adult Black-footed

Albatrosses decreased by about 8 percent over a twoweek period in early egg-laying and nesting stages,

presumably because of a reduction in heavy fat deposits which birds have prior to that time.

Woodward (POBSP) shows a dramatic decrease in

the number of nonbreeding Black-foots during

March and April on Kure Atoll. By late February

most breeders are away from the atoll most of the

time. The general exodus of birds from breeding islands which takes place in March and April may

explain the regular April-May ingression of birds

into the area off California as noted in the CalCOFI data. McHugh's (1955) 1949 distribution

data certainly suggest a northeastward movement

away from the breeding grounds, followed by, and

coincident with, a northward movement paralleling

the coast. The timing of this movement corresponds

to the subsequent CalCOFI data reported here.

After the young albatrosses are fledged in early

July, the adults stay away from the breeding

grounds permanently and disperse throughout their

range. Their distribution is probably governed by

the distribution of food organisms, concentrations

of which, at least in the case of immature birds, are

possibly found only by random searching.

Overall movements, as indicated earlier in the

literature review, show that some birds are in the

area of the Aleutians as early as May (Gabrielson

and Lincoln, 1959:74), and as late as November

(Kenyon, 1950). There seems to be no clear-cut

trend in the winter movements in the far northeast

Pacific. Rice and Kenyon (1962a) estimated that

about 14 percent of the Black-foot population (oneand two-year-old birds) winter at sea.

DISTRIBUTION IN RELATION TO THE ENVIRONMENT

CURRENTS AND WATER MASSES.—The southern

limits of Black-foot distribution generally coincide

with the southwestern sweep of the California Current in the eastern Pacific Ocean off Baja California and the North Equatorial Current in the central Pacific Ocean. Although there are few data

available for the western Pacific it seems likely that

Black-foots usually do not range south or west of

the North Pacific or the Kuroshio Currents, which

may explain the scarcity of birds reported by Starrett and Dixon (1946). La Touche (1934) and

Cheng (1955) both stated that this species occurs

off China. It is common in the Bering Sea in summer, considerably north of the major northerly

currents, the West Wind Drift and the Alaskan

Stream. In winter the species apparently does not

range very far north of the Kuroshio-Oyashio convergence in the northwest Pacific, nor of the subarctic current (ca. 50°-55°N) in the northeastern

Pacific.

Thompson (1951) found that Black-foots tended

to be more abundant in the California Current off

California than in eastern North Pacific Central

Water. Within the California Current, Miller

(1942) found Black-foots concentrated within

"tongues" of cold water off the southern California

Channel Islands. Sverdrup, et al. (1942) explain that

these tongues are caused by intense upwelling of

deep water along the coast which are swept southward along the surface by the California Current.

The point of upwelling in Miller's description

would have been at Point Conception, California.

Reid, et al. (1958:30) note that upwelling along

the North American coast is seasonal, being

"strongest off Baja California in April and May, off

southern and central California in May and June,
NUMBER 158 111

off northern California in June and July, and off

Oregon in August." Thus, while the initial increase

in abundance of Black-foots close to the central

California coast (north of Point Conception) is correlated with the departure of adults and nonbreeding birds from the breeding islands in March and

April, it seems quite possible that this high density

of Black-foots is prolonged by the enriching process

of upwelling in May and June. Further, the decrease in upwelling off the central California coast

in July might well be a factor in the reduction in

Black-foot numbers usually noted at this time.

Farther north off Oregon, upwelling also occurs

close to the coast in August, and Black-footed Albatrosses are apparently concentrated there then

(Gerard Bertrand [Oregon State University], pers.

comm.). The large concentrations of birds found

by Yocom (1947) are well within the California Current, but the observed abundance was probably distorted by the fact that his ship spent several days

in the same location, thus creating a strong attraction factor.

Sanger (1970) observed a concentration of 78

Black-footed Albatrosses relatively close to shore

over the continental shelf in August 1965, but over

an 18-month period there was a general increase

in abundance with increasing distance from shore;

however, observations in nearshore areas may have

been inadequate for a direct comparison with offshore data. P. W. Martin (1942) implied an abundance of Black-foots off British Columbia in summer over offshore banks. The large concentration

of birds observed in Unimak Pass in the Aleutians

(Arnold, 1948) could well have been coincident with

local island-induced upwelling or tidal currents. In

the western Pacific, Kuroda (1955) saw his highest

numbers of Diomedea nigripes in the coastal waters

off Honshu, approximately west of the KuroshioOyashio convergence, in June and July.

SURFACE WATER TEMPERATURE.—There has been

much discussion on the relationship between Blackfooted Albatross distribution and surface water temperatures. Kuroda (1955) considered the species to

be warm water adapted in his study of the birds between Japan and the western Bering Sea. Thompson (1951) observed a seeming inverse correlation

between temperature (mostly 15°-25°C) and albatross numbers between Oahu and California.

Hamilton (1958), Wilhoft (1961), and Nakamura

(1963) all present temperature data which are inconclusive. In oceanic waters off Washington and

Oregon, relatively high surface water temperatures

(range over 18-month period, ca. 6°-17°C) were

associated with relatively large numbers of Blackfoots, and low temperatures were associated with

small numbers (Sanger, 1970). In the central Pacific near the main Hawaiian Islands, King (1970:

91) observed Black-foots in low densities when surface water temperatures were greater than 23°C

(range of ca. 22°-27°C).

The POBSP data correlating water temperature

and albatross occurrence show no clear-cut trends

for individual months; sample sizes (number of

days of observation) are often small and the data

are therefore insufficient to present graphically. In

most months the data apparently simply reflect the

range of surface temperatures encountered on the

cruises. The only month that indicates a trend at

all is March, which shows an inverse correlation

between Black-foot numbers and water temperatures from 20° to 28°C. This is in line with temperature data of King (1970) and Sanger (1970),

which suggest that the species is most often found

in relationship to surface water temperatures ranging from ca. 14° to 22°C.

A detailed analysis of the relationship of albatross abundance and water temperatures in the

CalCOFI area is beyond the scope of this paper;

however, a few brief generalizations can be made.

Ten-meter water temperatures were obtained at the

same time the albatross counts were made (California Marine Research Committee, 1963). The

warmest temperatures generally occurred off southern California and Baja California in September

and October, followed by rapid cooling through

March. Off southern Baja California (ca. 26°30'N

in the inshore strip), the 10-year mean October IOmeter temperature was 23°C; it can reasonably be

assumed that the surface temperature was warmer

by a few, perhaps several, degrees. Thus, the usual

fall evacuation by Black-foots from the zone south

of 30°N in the inshore and intermediate strips may

have been the result of a negative reaction by the

birds to increased water temperatures. Similarly,

the fact that the birds consistently reentered this

zone in winter may have been a result of cooling

water temperatures. Just off Point Conception

(CalCOFI station 80.60), the coldest 10-meter temperatures occurred between February and May (10-

year mean ca. 12.5°C), and the warmest from Au-
112

120 140 160 180 160

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

120 100 80

120 140

FICURF. 65.—The area bounded by the surface isotherms of 14° and 22°C

(after Muromtsev. 1958).

gust through October (10-year mean ca. 17.5°C).

The peak Black-foot numbers occur just north of

here as the water temperature is warming (in June),

although the entire annual range of temperatures

is within the "preferred" temperature range noted

above.

The apparent disparity in abundance of the

Black-footed Albatross between the western Pacific

(fewer birds) and the eastern Pacific (more birds)

may possibly be explained by the species' apparent

preference for a certain range of surface water temperatures. It was noted above that Black-foots were

most often found within a surface temperature

range of ca. 14° to 22°C. Assuming that the species

disperses randomly within, and actively associates

with, waters in this temperature range, one would

expect to find more birds in the eastern Pacific than

in the western Pacific. Figure 65, the average summer surface temperature in the North Pacific (after

Muromtzev, 1958), shows that the region encompassed by the isotherms of 14° and 22°C is more

than two times as large east of 170°W than west of

that meridian. Thus, if the Black-foot indeed does

actively associate within a 14° to 22°C surface water temperature range, one would expect most of

the population to be found in the eastern north

Pacific.

The absolute range of surface water temperature

in which this species has been observed is from

3.4°C in the Gulf of Alaska in March 1967 (University of Washington data), to 30°C in the western

Central Pacific in August 1960 (Wilhoft, 1961).

SURFACE SALINITY.—King (1970) observed an apparent direct relationship between Black-foot numbers and surface salinity in the central Pacific

(within a range of ca. 33.5%, to 35.0%,). He felt,

however, that this resulted from the fact that,

within his study area, the species' geographic range

occurred north of waters with a lower surface salinity. Off the Washington and Oregon coasts there

was no observable relationship between Black-foot

numbers and surface salinity (Sanger, 1970), although Black-foots were occasionally found in salinities far below normal sea water salinities (e.g.,

14.98%.).

AIR TEMPERATURE.—Air temperatures are closely

correlated with ambient surface water temperatures

in the ocean. One would expect, therefore, to find

similar relationships between Black-foot numbers

and these two parameters, and this indeed is the

case. King (1970:89) observed a pronounced inverse

correlation between air temperatures and Blackfoot numbers from 16° through 29°C. Few birds

were seen at temperatures warmer than 22°C, and

none above 27 °C. Sanger (1970) noted a direct relationship between air temperature and Black-foot

abundance within a range of 7° to 18°C, and

Kuroda (1960) believed that within an overall

range of 7.0° to 22.5°C the species preferred air

temperatures from 17° to 22.5°C.
NUMBER 158

WEATHER CONSIDERATIONS.—Wind is probably

the most significant feature of the weather affecting

albatross distribution. Since albatrosses are dependent upon the wind for mobility, it stands to reason

that they would avoid, or be found in lesser numbers in, areas with wind velocities insufficient or

marginal to maintain their sailing flight. The average wind velocity decreases as the equator is approached and the doldrum wind conditions are encountered; this fact no doubt plays a significant role

in limiting the southern distribution of the Blackfooted Albatross. High winds apparently have little

or no adverse effect on the Black-foot, since the

species has been noted sailing in winds as high as

113

70 knots (80 MPH) with no apparent ill effects

(Sanger, 1970).

Addendum

After this paper was written in 1968, the important paper of V. P. Shuntov (1968) came to my attention. It is in general agreement with the findings

reported here that the Black-footed Albatross is primarily a species of the eastern north Pacific, but

with some of the population occurring in the western part. Shuntov indicates the Black-foot ranges in

summer and autumn into the Sea of Okhotsk and

north into the western Bering Sea to the Gulf of

Anadyr, but not as far south in winter as our records in the central Pacific indicate.
114 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 115

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Appendix

Summary of published data on Black-footed Albatross distribution

Location Date Remarks Source

NORTHEAST PACIFIC

Point Barrow, Alaska

Gulf of Alaska and

Bering Sea

Between Unalaska and

the Pribilofs, Bering

Sea

llnimak Pass, Aleutians

Bristol Bay, Alaska

From S of Shumagin I.

(Alaska), W into southern Bering Sea at

75 mi N Seguam I.

From 47 mi NVV Semisopochnoi I., Aleutians,

to 30 mi W Cape

Spencer, Alaska

Southern Bering Sea

000 mi SE Unalaska to

the Farallon I. off

San Francisco

Great Circle route, San

Francisco to Yokohama, return via Honolulu to Los Angeles

Off British Columbia

and in Gulf of Alaska

British Columbia

Off British Columbia

60 mi inside Str. of Juan

de Fuca, Washington

51°44'N, 138°48'W49°5G'\, 128°16'\V

Washington

Trans-Pacific and off

Washington

5-11Jul 1898 the authors note, without comment, 11 Gabrielson and Lincoln, 1959:74

specimens reportedly collected here;

since the expedition during which these

birds were collected was in the north

Pacific 5-11 July 1897, it seems possible

that specimens were collected then and

not a year later at the extremely extralimital site of Point Barrow

May-Oct

Jul 47

9Jun43

no date

8-11 Jun43

some present in this area

100 at once

ranges nearly to 58°N in this region

continuous between these points

20Jun-10 Aug continuously seen in this area

43

Oct 47, Nov 48,

May 49

Nov 48 continuously in sight, following ship; up

to 10 seen at once

Aug 59, Mar 61 abundance slightly higher in NE Pacific

than NVV; maximum at once, 11 at

155°W on Great Circle route, 14 at

164°E on return

Sep 52-May 54 seen each of live cruises, most common

Sep-Oct, least common Nov-Dec

no date in pelagic waters; numbers increase as

spring progresses, a tendency to flock

in summer

Apr-late Sep "constant companion of fishermen on offshore banks"

no date 1

25 Jul 44-27 4-10 seen daily

Jul 55

14 Apr-30Oct "a common migrant or wanderer"

"well offshore"

Jun 55 numbers ranged from 0 at 180° to ca.

7.5/hr off Washington; mean daily

abundance 8.5 over six days E of 180°

Kenyon, 1950:98

Arnold, 1948:556-557

Murie, 1959:35

Arnold, 1948:556-557

Kenyon, 1950:98

Kenyon, 1950:97

Nakamura, 1963:239-245

Poole, 1966:71

Godfrey, 1966:20-21

Martin, 1942:27

Poole, 1966:71

Motoda and Fujii, 1956, t.3

Jewctt, et al., 1953:66

Hamilton, 1958:160-162

126
NUMBER 158 127

Summary of published data on Black-footed Albatross distribution—Continued

Location Date Remarks Source

48°27'N, 126°32'W43°08'N, 179°08'W

Cobb Scamount, 290 mi

off Washington

Off Washington and

Oregon

Central California to

northern Washington

Southern California to

northern Washington

Off Washington and

Oregon

100 mi off Washington

Oregon

Off central and northern

California

130° W off San Francisco

EAST-CENTRAL PACIFIC

California

Off southern California

Southern California

9-20 Aug 55

Aug50

1964-1965

1949-1950

Dec 48

1963

Feb-MarSl

apparently regular summer

visitors

1949

Oct 45

apparent increase during

summer

1949

Jun-Sep 1937,

1938

34°40'N, 129°50'W

34°00'N,131°31'W

34°OO'N,131°31'W

32°N(ca.), 132°34'W

31°40'N,136°00'W

Baja California

Mexico

Off Mexico at 22°N,

109°W

NORTHWEST PACIFIC

Along Aleutians between Oct, Nov 47

Unalaskaand 175°£

Between Kiska and Attu, Jun 43

and the USSR

Japan Apr to Nov

(year?)

Off Hokkaido Dec (year?)

43°05'N, 175°42'E 22Aug55

42°57'N, 171 °04'E 23 Aug 55

24 Feb-19 Mar

45

10Apr-l May

45

24May-15 Jun

45

Jul59

22-27 Jun 45

1949-1950

not noted

15Jun 54

seen daily, up to 12 following ship at

once

presence of Black-foots briefly mentioned

comprehensive seasonal data; see text

herein

comprehensive seasonal data; see text

herein

5-15 followed ship within 30-175 mi off

the coast

presence off coast to I30°W during all

seasons

present from here to Hawaii

not abundant off Oregon

increasing abundance over previous 20-

odd years noted

45 seen at once is maximum of period

"especially along the edge of the continental shelf throughout the length of

the state"

increasing abundance over previous 20-

odd years noted

concentrated offshore of Channel Islands

in "cold tongue" of water; commonly

12-15 birds at oceanographic stations in

cold tongue but never more than 5-6

outside this area; none seen in Santa

Barbara Channel

abundant, maximum of 65 seen at once

abundant, maximum of 50 seen at once

abundant, maximum of 95 seen at once

cumulative total of 30 near here

abundant, maximum of 73 seen at once

comprehensive seasonal data; see text

herein

off Baja California and in the Revilla

Gigcdo I.

seen south to here

a few seen

absent

common offshore in summer

none seen

2 seen in distance

2 seen in distance

Motoda and Fujii, 1956, t.3

Powell, et al., 1952:52

Sanger, 1970:342-349

McHugh, 1955:375-381

Kenyon,1950:98

Sanger, 1965:1

MacDonald and Lawford, 1954:14-15

Gabrielson and Jewett, 1940:80

McHugh, 1950:153

Thompson, 1951:228-229

Grinnell and Miller, 1944:40

McHugh, 1950:153

Miller, 1940:231-232

Yocom, 1947:518

Wilhoft, 1961:258-260

Yocom, 1947:518

McHugh, 1955:375-381

Fricdmann, et al., 1950:15

Poole, 1966:71

Kenyon, 1950:98

Arnold, 1948:556-557

Austin and Kuroda, 1953:299

Kuroda, 1963:234

Motoda and Fujii, 1956, t.3
128 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Summary of published data on Black-footed Albatross distribution—Continued

Location Date Remarks Source

42°51'N, 162°08'E42°45'N, 151°28'E

Off Honshu and

Hokkaido

25-27 Aug 55 none recorded here

Formosa Channel

Western Pacific

West Pacific area

16°05'N,119o02'E

New Hebrides to Solomons to western

Carolines and from

Okinawa to Saipan

Saipan to Pearl Harbor

Philippines to Pearl

Harbor

SOUTHWEST PACIFIC

New Holland

(Australia)

Dusky Sound, N.Z.

CENTRAL PACIFIC

Washington to Oahu

San Francisco to

Honolulu

Honolulu to

San Francisco

4 Jun14 Jul 54

Japan to Washington Jun 55

Between Torishima I. Apr 58

and Tokyo

Honolulu to Yokohama May 20

32°39'N, 160°37'E 16 Sep 64

34°36'N, 141°31'E Apr 51

WEST-CENTRAL PACIFIC

China coast

fairly concentrated close to shore; rare N Kuroda, 1955:292

to 200-300 miles off southern Kamchatka; maximum number of 11 just N of

Hokkaido

from Japan to 180°, mean daily abun- Hamilton. 1958:160-162

dance was 155 over four days, vs 8.5

over six days from 180° to Washington

occurred relatively infrequently Aronoff, 1960:277

present from a day out of Honolulu to a La Touchc, 1934:430

day before arriving Yokohama

I Jones, 1965:71

westernmost record of authors MacDonald and Lawford, 1954:15

winter-spring "Off the China coast during the winter Cheng, 1955:5

and spring; in the Taiwan Straits at

the end of the year, according to Swinhoe."

year round common in Formosa Channel La Touchc, 1934:430

1951-1952 flocks generally smaller in W Pacific than MacDonald and Lawford, 1954:14-15

in E

Jun45-Feb46 general absence noted Starrett and Dixon, 1946:268-270

Aug 60 daily total of 70+ birds Wilhoft. 1961:258-260

Mar, Apr 45 none Thompson, 1951:233

21 Apr 45

Oct45

no date

July 1884

Feb-Mar51

May 20

first seen at 15°40'N, 176°20'E

none

specific location not indicated, specimen Oliver, 1955:181

collected

vagrant specimen collected by A. Reischek

present near Hawaii, with maximum of

18, N of Maui

present to two days out of Honolulu

1000 mi SW San Jul 64

Francisco

San Francisco to Aug 45

Eniwctok

Southern California to Jul 59

Hawaii

North of leeward Mar 51

Hawaiian I.

24°22'N, 163°30'W 25 Aug 60

Philippines to Pearl Oct 45

Harbor

25 Jan-1 Dec 45 during most months abundance increases

as California coast is approached; see

text herein

125; maximum ever seen in single sighting at sea

last seen at 35°N, 151CW

numbers generally low

most plentiful mid-March; maximum of

60, 600 miles NW of Hawaii

daily total of 50 +

none

MacDonald and Lawford, 1954:14-15

La Touche, 1934:430

Thompson, 1951, 228-231

Yocom, 1947:518

Thompson, 1951:233

Wilhoft, 1961:258-260

MacDonald and Lawford, 1954:14-15

Wilhoft, 1961:258-260

Thompson, 1951:233
Laysan Albatross [Diomedea immutabilis)*

Gerald A. Sanger

Introduction

The material contained in this report is a summary of all at-sea observations of the Laysan Albatross (Diomedea immutabilis) gathered by the Pacific Ocean Biological Survey Program (POBSP) in

the central and eastern Pacific Ocean. Literature

records, scattered northern Pacific POBSP records,

and data obtained from POBSP island surveys are

included for general background information.

Humphrey (1965) gave a general summary of the

program's objectives and Gould (pp. 1-5 herein)

summarized the areas surveyed and the methods

and materials used in the data collection and

analysis. The reader is referred to these papers for

more details.

An estimated 1.5 million birds constituted the

world population of Laysan Albatrosses {Diomedea

immutabilis) in 1956-1958 (Rice and Kenyon,

1962a: 383). Although the Laysan is five times as

abundant as the Black-footed Albatross {Diomedea

nigripes) there has been a grossly disproportionate

lack of information on the pelagic habits and distribution of the former species at sea. The Laysan

Albatross is a shy bird, usually not strongly attracted to ships. Consequently, it has been seen and

studied at sea far less than the gregarious, inquisitive Black-foot. Indeed, until 1950 Laysans were

quite erroneously thought to range only to 40°N,

but Kenyon (1950) showed them to range as far

north as the southern Bering Sea. Recent papers

which mention scattered sightings at sea (e.g.,

Hamilton, 1958; Kuroda, 1955) have expanded our

Gerald A. Sanger, National Marine Fisheries Service, Northwest Fisheries Center, 2725 Montlake Blvd. East, Seattle,

Washington 98112.

• Paper Number 71, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

knowledge, but they also glaringly exposed our ignorance of gross distribution and movements. Pelagic observations of the POBSP in the central Pacific, off southern California, northern Baja California, and in the Aleutians, plus a seasonal study

off Washington and Oregon (Sanger, 1970), have

gone a long way toward providing an understanding of movement in rather small areas of the north

Pacific Ocean. Moreover, large-scale banding studies

by the U.S. Fish and Wildlife Service and the POBSP

have revealed much about the qualitative distribution of known-age birds at sea.

BREEDING.—The Laysan Albatross presently

breeds exclusively in the Hawaiian Islands (Table

23). The population is centered in the Leeward

chain, but a small population breeds irregularly on

Niihau and a nesting was recorded on Moku Manu

off Oahu (Richardson, 1957:16). Fisher (1967,

1971) contributed to our knowledge of the Laysan's

breeding biology on Midway Atoll. Rice and

Kenyon (1962a, 1962b) gave an account of general breeding distribution and phenology. The

breeding pattern follows that of the Black-footed

Albatross, but is 10 to 14 days later in starting and

finishing. Breeding birds return to the islands the

first week in November, eggs are laid at the end of

November or early December, chicks hatch at the

end of January or early in February, and all birds

have fledged and headed out to sea by the second

week in August. The proportion of nonbreeding

birds on the islands is the same as that of the Blackfooted Albatross, about 75 percent.

SUMMARY OF PUBLISHED PELAGIC OBSERVATIONS.—

The Laysan Albatross is an abundant species

throughout much of the north Pacific Ocean, although rare or uncommon in some parts of its

range. Its at-sea range is from the Japanese coast

to 150°W and, in winter, almost to the North

129
130 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 23.—Laysan Albatross breeding populations

Location

Largest number Number of

of breeders' breeding pairs'1

Kure

Midway

Pearl and Hermes Reef

Lisianski

Laysan

Gardner Pinnacles ...

French Frigate Shoals

Necker

Nihoa

Niihau

TABLE 24.—Recent specimen records of Laysan

Albatrosses off North America

3200*

no,oood

30,000"

8,000"-

10,000

300,000"-

500,000

14C

1,000"

1,650"

38l

no data

350

100,055

17,750

30,000

130,000

2

584

2,500

500

500

• POBSP and U.S. Bureau of Sport Fisheries and Wildlife

data.

bFrom Rice and Kenyon (1962a:369). A discussion of the

disparity between these two sets of figures is beyond the

scope of the present paper. The estimates are presented

merely to give the reader an idea of the general population

size of Laysan Albatross. A more accurate and detailed evaluation of populations will be presented in island accounts currently under preparation (POBSP) .

c

 Recorded.

" Estimated.

American Pacific Coast; from the southern Bering

Sea and the Gulf of Alaska south to about 28° N

in the eastern Pacific, 13°N in the central Pacific,

and about 30° N in the western Pacific.

Available data on the life history of the Laysan

Albatross prior to 1962 have been summarized

(Palmer, 1962:126-130). The previously known

marine range and published pelagic records are

summarized in the appendix. Information on Laysan distribution adjacent to coastal North America

south of Alaska is scanty or nonexistent in major

area references (e.g., Godfrey, 1966; Grinnell and

Miller, 1944), but a number of recent papers (e.g.,

Holmes, 1964), supported by a mass of POBSP

sightings, show that the Laysan Albatross is indeed

common in this area from late fall through early

spring. Winter storms are notoriously severe in the

northeast Pacific and this fact has no doubt dissuaded bird observers from venturing into the

region at this time.

Since the Laysan Albatross is a reasonably distinctive bird, and the only species normally ranging in the north Pacific with which it could be confused (Diomedea albatrus) is extremely rare

(Sanger, 1972), the sight records as a whole are

Area Date

13Jul60

Remarks

dead specimen on

beach

dead specimen on

beach

caught alive from

a fishing vessel

Source

Fredrich,

1961:500

McAllister,

1954:211

Stager,

1958:404-

405

Northern Oregon

coast

Northern Oregon 30 Jan 53

coast

Five mi off S. 6 Feb 58

California

probably quite valid. Supporting the sight observations off North America are three recent specimen records (Table 24).

ACKNOWLEDGMENTS.—Many people in addition

to those mentioned by Gould (p. 5) helped make

this paper possible. Warren B. King and Patrick J.

Gould were especially helpful in offering useful

criticism on early drafts. George E. Watson read

the final draft. Richard H. Fleming initiated the

bird observation program for University of Washington Department of Oceanography cruises, which

resulted in many sightings; these cruises were sup

ported by various research grants from the U.S.

Office of Naval Research and the U.S. Atomic

Energy Commission. Robert L. Wisner, Scripps Institution of Oceanography, kindly assembled the

California Cooperative Oceanic Fisheries Investigations sightings.

Distribution and Abundance

SPECIMEN RECORDS

Three Laysan Albatrosses have been collected atsea by POBSP personnel. Two were taken south of

the western Aleutians and the third in the central

Pacific. Pertinent data for these specimens are listed

in Table 25.

SIGHTING RECORDS

Figures 81-92 (pp. 140-151) show average

monthly Laysan Albatross distribution in the Pacific Ocean as determined by POBSP sightings. The

relative abundance is indicated by a unit of mean

number of birds per sighting per day (BPS). In addition to POBSP sight records (1964-1968), sightings

during a number of earlier University of Washing-
NUMBER 158 131

TABLE 25.—Laysan Albatross specimens collected at sea by the POBSP

51

44

13

Location

°19'N,172°

°25'N,173°

°53'N,171°

46'E

O2'E

O5'W

USNM

number

496197

503268

496720

Sex Body weight

(gin)

p

3110

?

Gonad size

(mm)

12x3,11x3

?

11x5

Date

4 Oct 65

13 Oct 65

1 Feb 66

Collector

R. DeLong

R. DeLong

R. Crossin,

D. Husted

ton Department of Oceanography cruises are included on the maps. These cruises occurred in the

Gulf of Alaska in September 1955, May 1956, and

April 1957, and in the Aleutians to 173°28'E in

August-September 1957. Since the distribution of

the Laysan has been so poorly understood in northeastern Pacific waters, these sightings are listed in

detail in Table 27, as well as on the maps.

Laysan Albatrosses were also noted during the

CalCOFl oceanographic cruises off California and

Baja California from 1951 through 1959 (for details

of these cruises see the Black-footed Albatross account, Sanger, this volume). These are listed in

Table 26.

January Distribution (Figure 81): In the central

Pacific, only scattered individuals were observed

southwest of the main Hawaiian Islands to

17°15'N. Birds were undoubtedly abundant in the

Leeward Islands, but no trips were made to that

area. The species was relatively common and abundant (up to 4.0 BPS) off southern California. It was

also seen commonly off Washington and Oregon,

and occurred in densities up to 7.3 BPS about 600

miles off northern Oregon.

February Distribution (Figure 82): The frequency of sightings in the central Pacific increased

over January (the southernmost sighting occurring

at 13°02'N), but the species was still seen on only

a minority of all days. A vagrant was noted at

8°30'N by Thompson (1951). Sightings off southern

California decreased, with birds being seen on only

four days. The northernmost winter record was

noted at 53°00'N, 141°30/W in the Gulf of Alaska,

on 6 February 1967.

March Distribution (Figure 83): Laysans were

observed rather frequently in the central Pacific,

and, although scattered birds reached almost 17°N,

they were uncommon south of 20°N. One bird,

possibly a vagrant, was recorded at ll°30'N,

151°04rW. Observations were conducted along the

Leewards for the first time; birds were found in

densities of up to 2.3 BPS. They were seen on only

four days off southern California, the southernmost

record being at 28°49'N. None were observed in

the Gulf of Alaska during five days spent north of

50°N, but scattered individuals were recorded off

Washington and Oregon in 1963.

April Distribution (Figure 84): In the central Pacific Laysans were uncommon south to 17°30'N,

but relatively common from 23°N to at least 35° N.

They were noted on three days off southern California and were seen only at distances greater than

450 miles off Washington and Oregon. They were

recorded north to 55 °N in the Gulf of Alaska

(1957).

May Distribution (Figure 85): Only a single Laysan was seen south of 24°N (18°25'N, 155°28'W)

TABLE 26.—Laysan Albatross sightings (one bird

each) during CalCOFl Cruises, 1951-1959

Date

22 Feb 51

20 Jan 53

10 May 53

17 Jun 53

10 Aug 53

12 Aug 53

4 Sep 53

9 Sep 53

10 Sep 53

23 Jan 54

1 Feb 54

19 Mar 54

13 Oct 54

15 Jul 56

6-7 Nov 56

8 Dec 56

1 Feb 58

10 Apr 58

24 Apr 59

32e

28'

31'

37'

40'

44'

51'

41'

40'

24'

33°

25'

32'

40'

29'

30'

33'

36'

33'

34'

Location

09'N, 125°15'W

'42'N, 116°37'W

'35'N, 118°30'W

'37'N, 123°37'W

'30'N, 149°45'W

=20'N, 150°18rW

W N , 158°40'W

'20'N, 155°13'W

3

00'N, 155°00'W

3OO'N, 132°00'W

28'N, 133°26'W»

'18'N, 125°00'W

5O4'N, 120°39'W

W N , 159°00'W

'26'N, 119°45'W

'25'N, 117°45'W

'00'N, 120°21'W

3

03'N, 122°02'W

'39'N, 122°12'W

'20'N, 122°O1'W

•Two birds.
132 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 27.—Miscellaneous sight records of Laysan Albatross from the eastern

North Pacific, (observers, except one, from University of Washington)

Date

28 Sep 49

3 Sep 55

4 Sep 55

6 Sep 55

5 May 56

7 May 56

8 May 56

8 May 56

8 May 56

8 May 56

9 May 56

9 May 56

9 May 56

9 May 56

12 May 56

13 May 56

29 May 56

1 Jun 56

8 Aug 57

9 Aug 57

9 Aug 57

13 Aug 57

14 Aug 57

15 Aug 57

15 Aug 57

16 Aug 57

16 Aug 57

17 Aug 57

18 Aug 57

18 Aug 57

18 Aug 57

20 Aug 57

20 Aug 57

24 Aug 57

25 Aug 57

25 Aug 57

Location No. of birds

38°OO'N,

53°38'N,

50°58'N,

51°06'N,

50°43'N,

50°12'N,

50°02'N.

50°02'N,

50°01'N,

50°00'N5O°O2'N

51°15'N,

52°02'N,

52°05'N,

52°31'N,

59°17'N.

59°34'N,

54°36'N,

50°01'N,

50°22'N,

50°32'N,

50°52'N,

50°42'N,

50°4O'N,

49°44'N,

49°3O'N.

49°2O'N,

49°35'N,

51°08'N,

51°13'N,

51°19'N,

51°24'N,

52°39'N,

52°42'N,

51°11'N,

51°02'N,

51°02'N,

123°45'W

161°28'W

161°09'W

152°4O'W \

133°48'W

142°39'W

144°12'W 5

144°21'W

144°45'W \

145°02'W144°56'W

145°03'W

145°02'W

145°02'W

145°02'W

144°59'W 5

144°3O'W

152°46'W

144°57'W

177°38'W 1

177°29'W 5

177°35'W

177°12'E

177°18'E S

174°29'E 1

173°29'E S

173°28'E 5

173°28'E

174°41'E 1

174°32'E 5

175°05'E 5

175°35'E 1

180°00'

179°41'W 1

173°2O'W 1

171°45'W 1

171°45'W 1

i

>

>

1

I

>

>

Observer

R.C. Miller*

unknown

"

CM. Love

" ••

• • "

•* "

G.H. Allen

CM. Love

" "

H.Jackson

G.H.Allen

unknown

'•

CM. Love

P. McCrery

H. Jackson

P. McCrery

G.H.Allen

P. McCrery

E. Linger

R. Rubinstein

P. McCrery

R. Rubinstein

P. McCrery

R. Rubinstein

E. Linger

P. McCrery

R. Rubinstein

E. Linger

P. McCrery

R. Rubinstein

E. Linger

Remarks

letter of 21 Jan 66 to Sanger

Operation NORPAC

i . • •

bird stayed with drifting

ship for 7.5 hours

I.G.Y. Expedition

" "

" "

" "

" "

" "

" "

•• "

••

" "

"

" "

"

" "

in the central Pacific, but the species was still common in the Leewards. In 13 days of observations off

southern California, Laysans were seen on only two

days. A single bird was recorded as close as 200

miles off the Washington coast, but most were west

of 140°W. In the Gulf of Alaska (1956) the species

was seen as far north as 59°34'N, this apparently

being the northernmost record for the species.

June Distribution (Figure 86): Laysans were common in relatively low densities (less than 3.2 BPS) in

the Leewards, but were not seen in the remainder

of the central Pacific. None were observed off southern California, and one was seen in the Gulf of

Alaska (1956).

July Distribution (Figure 87): Our records show

only one sighting in the entire Pacific this month,

at 26°15'N, 174°00'W near Lisianski Island.

August Distribution (Figure 88): In the central

Pacific there were but two birds sighted in the Leewards (near Pearl and Hermes Reef), and two more

at 35°N. None were seen off southern California

and only one was observed off Washington, about

750 miles off the coast. In the Aleutians (1957), Laysans were common just south of the islands between longitudes 171°W and 173°E. Two were

noted one day in the southern Bering Sea at ca.

52°40'N, 180°.
NUMBER 158 133

TABLE 27.—Miscellaneous sight records of Laysan Albatrosses from the eastern

North Pacific, (observers, except one, from University of Washington) —continued

Date Location No. of birds Observer Remarks

25 Aug 57

13 Sep 57

14 Sep 57

2 Apr 57

3 Apr 57

13 Jan 61

16 Jan 61

27 Jan 62

10 Oct 62

1 Mar 63

1 Mar 63

9 Mar 63

11 Mar 63

15 Oct 66

15 Oct 66

16 Oct 66

16 Oct 66

18 Oct 66

19 Oct 66

20 Oct 66

23 Oct 66

24 Oct 66

24 Oct 66

26 Oct 66

27 Oct 66

30 Oct 66

13 Nov 66

14 Nov 66

19 Dec 66

21 Dec 66

27 Sep 67

29 Sep 67

29 Sep 67

5 Oct 67

6 Oct 67

7 Nov 67

51°02'N,

52°58'N,

51°53'N,

55°30'N,

54°20'N,

'48°10'N,

46°22'N.

46O41'N,

42°21'N,

48°14'N,

48°13'N,

45°34'N,

44°16'N,

47°04'N,

46°53'N.

47°OO'N,

47°OO'N,

47°OO'N,

47°OO'N,

46°55'N,

46°55'N.

47°OO'N.

47°OO'N.

47°OO'N,

47°00'N.

47°3O'N,

48°00'N,

47°45'N,

48°10'N,

46°03'N,

53°S0'N,

52°3O'N,

52°07'N,

50°00'N,

47°33'N,

48°25'N,

171°45'W

15O°34'W

150°42'W

139°0O'W

135°OO'W

126°42'W

129°30'W

126°40'W

125°25'W

126°46'W

127°45'W

129°30'W

127°24'W

130°08'W

13O°31'W

132°1O'W

132°OO'W

132°00'W

132°OO'W

132°12'W

132°OO'W

132°03'W

132°0O'W

132°00'W

132°00'W

129°45'W

131°52'W

131°55'W

125°41'W

126°4O'W

162°00'W

"l60°00'W

159°2O'W

137°OO'W

133°OO'W

129°18'W

P. McCrery

E. Linger

unknown

CM. Love

K. Light wood

CM. Love

J. Nickerson

R. Robeck

D. Armand

J. Nickerson

D. Armand

R. Robeck

D. Armand

R. Robeck

D. Armand

V. Wyatt

J. Nickerson

V. Wyatt

ca. 35 mi off Cape Alava,

Washington

•California Academy of Sciences.

September Distribution (Figure 89): None were

seen in the central Pacific or off southern California; one was seen some 35 miles off central California (Robert C. Miller, California Academy of

Sciences, pers. comm.). The species was common in

the western Aleutians and in the western Gulf of

Alaska (1955, 1957).

October Distribution (Figure 90): None were

seen in the central Pacific nor off southern California again this month. Off Washington and Oregon,

however, Laysans were common in densities of up

to 4.0 BPS. One was noted 75 miles off Washington,

but most were much farther offshore. South of the

western Aleutians, they were common and extremely abundant. A center of abundance was

noted at ca. 45°N, 173°E, where densities of 20 and

30 BPS were recorded on two consecutive days.

These are high records for pelagic areas away from

breeding islands.

November Distribution (Figure 91): One bird

was observed in the central Pacific near Kaula Rock

(21°45'N, 160°30'W), but no surveys were conducted in the Leewards. Single birds were seen on

three days off southern California and the species

was common to abundant to 138°W in areas farther than 150 miles off the Washington and Oregon

coasts.

December Distribution (Figure 92): Laysan Alba-
134 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

trosses were abundant (up to 10.0 BPS) in the western Leewards, but only scattered sightings were

made south to 13°37'N in the central Pacific. Only

on 3 out of 33 days were they seen off southern

California. Off Washington and Oregon, single

birds were noted on two out of an unspecified number of days; one was a scant 35 miles off Cape

Alava, Washington.

ANNUAL PELAGIC CYCLE

The appearance of Laysan Albatrosses in pelagic

areas of the central Pacific in late November corresponds to their arrival on the breeding islands.

Numbers increase at sea around the breeding islands in December and scattered birds are recorded

to almost the southern limits of their central Pacific range. From December through May they are

seen, though uncommonly, in pelagic areas south

to 13°N, with February being the month of peak

abundance south of 20°N and the month of most

southerly penetration. Birds begin to leave the central Pacific in May and by July and August there

is only an occasional bird seen in the northern

Leewards. They are unrecorded in September and

October. This seasonal shift in distribution is illustrated in Figure 78. It can be seen that this

north-south shifting of birds is synchronized across

the central and eastern Pacific. The northern range

limits also retreat southward in winter, but this is

neither as pronounced nor as well documented as

it is in the central Pacific.

The occurrence of Laysan Albatrosses in the Gulf

of Alaska also appears to be cyclic, with spring being the season of maximum abundance and northward penetration. A few birds occur in the southern

part during winter. As spring approaches they move

northward and by May can be found in the northernmost part of the Gulf. As summer approaches,

they move westward out of the Gulf, and are found

with any regularity only west of 160°W; most of

, the population apparently occurs west of 180°.

Thus, the westward movement out of the Gulf of

Alaska corresponds to the late spring movement

away from British Columbia, Washington, and

Oregon (Sanger, 1970).

ABUNDANCE AT WEATHER STATION Victor

Figure 79 presents counts of Laysan Albatrosses

made by personnel of the USCGC Winnebago at

Ocean Station Victor (34°N, 164°E), from 26

February through 19 March 1967. The maximum

number of birds seen at any time during the day

(upper graph) ranged from none on 17 March to a

high of 27 on 15 March. Most counts revealed no

more than 14 birds. The maximum number of

birds during the day usually occurred in the afternoon (1600), although the high counts were in the

morning on three days. This suggests that Laysans

were less inclined toward a regular daily activity

cycle than Black-footed Albatrosses, who never displayed maximum numbers in the morning in the

same area.

BAND RETURN INFORMATION

Routine monitoring of banded birds during surveys of the breeding colonies on the leeward Hawaiian Islands has documented numerous interisland movements of Laysans. Most of these involve

birds moving the short distance between Kure and

Midway Atoll, or between Kure and other Leeward

locations. Only one bird has been recaptured on

land away from the breeding islands. This specimen, banded as an adult on Kure Island, was recovered on Mejit Island (ca. 10°30'N, 171°00'E),

Marshall Islands, on 20 May 1965 (Amerson, 1969:

293), but must be regarded as a stray in this extralimital location. This represents the southernmost

specimen record for this species.

The POBSP Laysan Albatross band returns are being integrated with those of the U.S. Fish and Wildlife Service (Robbins and Rice, p. 234, herein).

Pertinent highlights of this information are summarized here. Recoveries of subadult birds (through

the fifth year of life) suggest that they are more inclined to be scattered longitudinally than adult

birds, but most recoveries were west of 180°. More

than half of the summer adult recoveries occurred

between 170°E and 180°, in and just south of the

western Aleutian Islands. Almost all of the summer

adult recoveries were from north of 40°N between

Japan and the Aleutians. In winter, the adult recoveries were mainly south of 40°N, scattered between Honshu, Japan, and Midway Atoll.

Analysis of Distribution

GENERAL CONSIDERATIONS

Two major trends are apparent in the gross distribution of the Laysan which are similar to those
NUMBER 158 135

45

40 -

30 -

25

30

25 -

20 -

15 -

10 -

•

-

-

1 1

4 4 4 4

If 1

\l •+- Southern Distribution -*- \

U Point 1

jJIPlllIJi )|[|

/ ~ x -<— Southern Observational -*- ,

v

 Limit

' x '

X

' X '

X

1 1 1* 1 1 1 l' 1 1

J FMAM J JASON O

Months

EASTERN PACIFIC

-

-

pr \

\y Point \

Vagrant Sightings 171°F

• 163°33'W ' N-«-Southern Observational

' v Limit

1 X

/ x

1 1 1 1 l/ 1 >l 1 1 1 1

V

1

J FMAM J JASO N

Months

CENTRAL PACIFIC

FIGURE 78.—Seasonal and latitudinal shifting of Laysan Albatrosses in the central and eastern

Pacific Ocean.
136

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

30

25

20

15

10

5

0

Birds seen at

••••0800 hours

1200 hours

— -1600 hours

26 27 28 1 10 11 12 13 14 15 16 17

February

18 19

KK.IRE 79.—Counts of Laysan Albatrosses made by personnel of the USCGC Winnebago at

Ocean Weather Station Victor (34°\, 164°E) 26 February through 19 March 1967.
Seasonal Variation in the Range of

Laysan Albatross

E 3 Summer (August)

EZ3 Winter (February-March)

72 Spring-Gulf of Alaska

•£23 Area of apparent nonbreeding concentrations

no E 130 ISO 170 170 ISO 130 110

FIGURE 80.—Seasonal variation in the range of the Laysan Albatross.

of the Black-footed Albatross. First, there is a major latitudinal population shift concurrent with

the winter breeding season (Figure 80). In summer, they are fairly far north in the Pacific, apparently concentrated off the Kuriles and in the Aleutian Islands. During the winter breeding season,

their range shifts considerably farther south (to

13°N). Rare birds have been seen at 11°N (King,

1970:9) and 8°30'N (Thompson, 1951) in the central Pacific Ocean. The second major distributional

feature is that the Laysan is predominantly a western and central north Pacific species, in contrast to

the Black-footed Albatross which has a more even

or eastern distribution.

The movements of breeding adults and older immatures are directed toward the breeding grounds

in late fall, and away from the breeding grounds

and toward feeding areas early the following summer. Moreover, about half of the breeding birds are

away from the breeding grounds at any given time

during the breeding season; indeed, the recovery

of a breeding bird over 2000 miles away 23 days

after being banded on its nest shows that breeding

birds can range well away from the breeding

grounds (Kenyon and Rice, 1958). Curiously, the

breeding season range is much broader than that of

the nonbreeding season. In winter, Laysans are uncommon to common off North America from northern Baja California to southern British Columbia, and off Japan as far south as Kyushu. These
138

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

birds are no doubt mostly prebreeding immatures,

but probably include some adult breeders. Kenyon

and Rice (1958) demonstrated the amazing ability

of this species to cover vast distances in relatively

short periods of time, despite adverse weather conditions.

Banding returns indicate that the postbreeding

dispersal of adults and fledged young takes them

northwestward from the breeding grounds. POBSP

sightings for September and October 1964-1965 indicate that maximum numbers of Laysans may occur in the Aleutians in late summer and early fall.

Therefore, the occurrence of Laysans off Japan in

summer may be because of a curvilinear migration

route to the Aleutians.

DISTRIBUTION IN RELATION TO THE ENVIRONMENT

CURRENTS AND WATER MASSES.—As in the case of

the Black-footed Albatross, the gross distribution of

the Laysan Albatross (Figure 80) is similar to the

distribution of certain major currents and water

masses. Winter distribution seems generally to parallel the circulation of the north Pacific cyclonic

currents, but individuals wander north of the West

Wind Drift and south into the Equatorial Countercurrent. Concentrations of birds in summer are apparently mostly within the western Subarctic and

Alaskan Gyres, and north of the West Wind Drift

(see Dodimead, et al., 1963, for descriptions of these

currents and water masses). Summer distribution

seems to conform to the Kurilo-Aleutian surface

water mass (Muromtzev, 1958:248) with some birds

being found in the western part of the "Alaska Bay

( = Gulf) surface water." Distribution off Japan

(Kuroda, 1960; Robbins and Rice, pp. 236-237,

herein) relates well to the Kuroshio-Oyashio convergence, with no birds being found in the warm

Kuroshio Current in summer.

SURFACE WATER TEMPERATURE.—The maximum

surface water temperature tolerated by most of the

population seems to be about 21° to 24°C

(70°-75°F) in the central Pacific in winter. In summer, individuals occur as far south as 35°N, where

the surface temperature would again be in the 21°

to 24°C range (Muromtzev, 1958, fig. 112). However, the surface water temperatures in the western

Aleutians, where most of the population apparently summers, is moderately cold, about 8° to

10°C (Muromtzev, 1958, fig. 112). Kuroda (1960)

suggested that the Laysan is the most cold-adapted

albatross in northwest Pacific waters. When the

Laysan occurs off Washington and Oregon in winter, the surface water temperature generally ranges

from 8° to 10°C. Within an observed annual range

of about 7° to 17°C in this area, Laysans were

found to occur most often in relatively low temperatures, and only three times (all during the same

cruise) in water warmer than 14°C (Sanger, 1970).

King (1970) noted that albatrosses (both Laysan

and Black-foot) were seldom found in water

warmer than 23°C in a survey area east and southeast of the main Hawaiian Islands (the data from

which are included in this report). As long as the

birds are within their physiological temperature

tolerances, distribution will probably be dictated

by the distribution of preferred food organisms and

not by water temperature per se.

AIR TEMPERATURE.—The limits of the Laysan's

range seem to parallel the isotherms of about 5°

and 24°C regardless of season. The 24°C (75°F)

isotherm lies at about 20°N latitude in March and

at about 40° N latitude in August in the central

Pacific (U.S. Navy, 1956). Both of these latitudes appear to be the southerly limits of most of the Laysan population during the respective seasons (see

Figures 81-92). The temperature tolerance of this

species is conjectural at this point, but the species

has been seen in temperatures ranging from 4.8°C

in the Gulf of Alaska in February 1967 to as high

as ca. 26°C in the central Pacific (King, 1970:89).

Kuroda (1960) observed that Laysan Albatrosses

preferred 13° to 15°C temperatures within a range

of 6.2° to 22.5°C in the summer in northwest Pacific waters. In waters off Washington and Oregon,

Laysans were encountered most often when the air

temperature was less than 10°C in an annual range

of 6.6° to 18.0°C (Sanger, 1970).

SURFACE SALINITY.—The distribution of Laysans

indicates that they occur in waters with moderate

to high salinities, and only rarely in low salinity

water (less than 32.5-33.0%o). The surface salinity

in areas of Laysan Albatross concentrations, i.e.,

west of 180° and north of 40°N, generally ranges

from 33-34%o (Muromtzev, 1958:374). Seasonal data

from off Washington and Oregon show that, indeed, Laysans may avoid relatively low salinity

water (Sanger, 1970). In summer, when Laysans are

well away from the coast, salinity of less than

32.5%o (resulting from runoff from the Columbia
NUMBER 158 139

River) has been traced westward to nearly 132°W

off Oregon (Budinger, et al., 1964:52). Coincidentally, there is no such offshore area of low surface

salinity in the northwest Pacific. In winter, prevailing south and southwesterly winds off the Washington-Oregon coasts tend to hold river runoff within

a relatively few miles of the coast (Budinger, et al.,

1964:69), allowing a maximum eastward invasion

of oceanic water toward the coast via the California

Current. It is at this time that maximum abundance of Laysan Albatrosses occurs in the area and

they occur closest to shore (see Figures 81, 91). In

the central Pacific, albatrosses tended to be found

in higher salinity water within a range of 33.9%o

to 35.2%o (King, 1970:96).

WEATHER CONSIDERATIONS.—As in the case of

Black-footed Albatrosses (see p. 113), wind is

probably the most significant feature of the weather

affecting Laysan distribution. The doldrum wind

conditions no doubt play a significant role in limiting the southern distribution of the Laysan Albatross.

Addendum

After this paper was completed in 1968, two important papers on the pelagic distribution of Laysan Albatrosses were published, those of V. P.

Shuntov (1968) and Fisher and Fisher (1972). Generally, these authors indicate the same distribution

patterns reported here, but with certain notable

exceptions.

Shuntov, using sightings at sea, has Laysans ranging much farther north in winter than our data

indicate, to about 59°N in the Gulf of Alaska, and

to about 55° N in the western Bering Sea. Also, contrary to our sightings and those in the literature,

Shuntov has Laysans ranging south to only about

21 °N in the central Pacific. In summer, he shows

Laysans ranging well into the Sea of Okhotsk and

north in the western Bering Sea to the Gulf of

Anadyr.

The Fishers' paper is based on 109 captures at

sea of birds banded on Midway Island and most of

the sightings noted in the literature; omitted for

unknown reasons are Sanger's (1970) records off

Washington and Oregon. These omissions cast

some doubt on the validity of the graphs (Fisher

and Fisher, 1972: figs. 3, 5, 7) portraying average

monthly longitudinal and latitudinal movements,

as does the lack of statistical treatment of the data

in the graphs. The inclusion of standard deviations

of the means shown in the Fishers' figures 3 and 5

would have given an idea of how representative the

means really are. Puzzling is the contention (Fisher

and Fisher, 1972:8) for "a probable similarity in

the distribution of tunas and albatrosses in the

North Pacific. . . ." The facts are that tuna

range far south of the southern limit of the Laysan's range (cf., Rothschild and Uchida, 1968),

and that Laysans range far north of the northern

limits of tuna distribution. The northern part of

the tuna range and the southern part of the Laysan's range merely overlap. Fisher and Fisher's

(1972:16) curious reference to Seckel's (1970) discussion of weather-sea surface interactions in the

area from 0° to 35°N, and 130°W to 170°W, for

documenting "turbulence and many eddies between 35° and 40°N and 140° to 160°E," and their

erroneous view that warm oceanic waters have low

salinity (Fisher and Fisher, 1972:17, 23), suggests

that more rigor might have been applied in discussing oceanographic matters. The question raised

by the authors of whether their data reflected the

distribution of albatrosses or of persons recapturing

albatrosses never was convincingly answered, especially in view of the disparity in the distribution of

albatrosses and tuna (and therefore tuna fishermen).

Longline tuna fishing is by far the most susceptible

means of capturing albatrosses at sea because the

birds actively go after the baited hooks. These and

other flaws notwithstanding, the Fishers have presented an important, useful document, all the more

so because they have given evidence for differences

in the at-sea distribution of young and adult Laysan Albatrosses.
140 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 141

53* *S
142 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

z'2 "
NUMBER 158 143

a.

<
144 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 145
146 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 147
148 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 149

z'2 "
150 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
NUMBER 158 151
Appendix

Summary of published data on Laysan Albatross distribution

location Date Remarks Source

NORTHEAST PACIFIC

Various sites in the May-Oct

Aleutians, three Gulf

of Alaska sightings

230 mi £ Kodiak I., IS Oct 48

Alaska

Various sites in Aleutians Jun, Jul

90 mi S of Aleutians at 28 Mar 51

49°51'N, 178°22'W

Off Vancouver I. 25 Dec 52

10 Dec 53

Off Washington, Oregon 24-27 Fcb 58

and Vancouver I.

Off Washington and May 64-Nov 65

Oregon

100 mi off Washington Fcb 51

to Oahu

50°N, 173°W 23 Scp 54

48°N, 150°W to 30 mi

NW of Farallon I.

47°15'N, 126°45'W

Along 47° Nat 155° and

178°W

45°36'N, 124°S6'W

45°14'N, 127°31'W

44°45'N, 132°00'W

44°10'N,135°45'W

44°10'N, 132° W

41 °N. 137°30'W24°30'N, 155°W

40°32'N, 138°17'W

39°40'N, 139°W

37°37'N, 124°53'W

30 Nov-6 Dec 48

1 Dec 45

Aug 59

1 Oct 63

16 Mar 63

16 Dec 63

15 Dec 63

30 Nov 45

16-20 Jan 60

29 Nov 45

29 Nov 45

25 Jan 45

EAST-CENTRAL PACIFIC

North America when not

breeding

Within 45 mi of central Feb-Mar 58

California coast

California, far offshore Oct-Apr

from Cape Mendocino

to San Nicolas I.

possible confusion of early records with

Short-tailed Albatross

individual followed ship for several

hours; ship's captain quoted as often

seeing Laysans in same area

sight and specimen records; possibility

of several Short-tailed Albatross

sightings being Laysans

1, apparently the northernmost record

for the central North Pacific at this

early date

2 at 48°N, 133°W, was closest sighting

to North America

3 at 49°N, 133°W, were the most teen

off North America at this latitude;

generally scarcer in NE Pacific than

NW Pacific

6 sightings of 1-3 individuals, 60-100

mi off northern Washington and

southern Vancouver I.

comprehensive seasonal data; see text

herein

seen less often and in fewer numbers

than Black-footed Albatross

12 this date; place was maximum for

general area; seen north of 52 °N

several times

seen every day during this period; 1

collected 40 mi off northern California

1

155°W, apparently near eastern limits

of summer range

1

2

1

1

2

"Two or three were always present"

only southern range limits, i.e, Baja

California, specifically mentioned

11 sightings 8 Feb-29 Mar as close as

18 mi offshore

rare or casual visitant; specimen collected San Nicolas

Murie, 1959:39-40

Kenyon. 1950:100

Gabrielson and Lincoln, 1959:75

MacDonald and Lawford. 1954:16

Poole. 1966:71-72

Sanger, 1965:1-2

Sangcr, 1970:342-343, 349-352

MacDonald and Lawford, 1954:15-16

Poole, 1966:71-72

Kenyon. 1950:100

Thompson, 1951:234

Nakamura, 1963:239-245

Sanger, 1965:1-2

Thompson, 1951:234

Agnew, J. H. in Bourne, 1961:12

Thompson, 1951:234

Vaurie, 1965:19

Holmes, 1964:302-303

Grinnell and Miller, 1944:41
NUMBER 158 153

Summary of published data on Laysan Albatross distribution—Continued

Location Date Remarks Source

Baja California to

Oregon

Feb-Apr 49

San Geronimo, no date

Cuadalupe and San

Martin, Baja

California

34°N, 131°30'W 17 Mar 45

31 °47'N-35°3rN, within 31 Mar-5Apr

100-300 mi of shore

31°45'N, 129°W

NORTHWEST PACIFIC

SE of Kamchatka Peninsula

49

26 Mar 60

16Aug?

45ON,155°E 22 Oct 53

Off Pacific coast of Hon- early springshu and Hokkaido late autumn

Off Hokkaido, Kuriles, Jun,Jul54

and Kamchatka

40°N, from 165°E to

172°W

Coastal Honshu, Japan,

from ca. 35 °N to

38°30'N

Off Japan

36°N, 141°E

Off Japan 35°37'N,

142°59'E

Off Japan

34°56'N, 157°OO'E

30°N, 154°E

29°N, 146°E

CENTRAL PACIFIC

33°N, 166°E-23°30'N,

162°W

26°S0'N,151°3O'W

22°N, 170°W

N, S, and E of Hawaii

17°44'N,159°56rW

17°3O'N,171°2O'W

8°S0'N,163°35'W

6-8Jun55

Dec 62

Apr, May 51

10Jun53

apparently

May 51

not specified

22Aug60

Mar 61

22 Mar 60

9-12 Apr 61

12 Apr 60

Mar 61

1964-1965

22 May 59

22 Apr 45

1 Feb45

several sightings by people on oceanographic cruises; unspecified positions

and numbers

formerly fairly common but not recently seen

McHugh, 1950:153-154

Friedmann, et al., 1950:15

2 stayed near the stopped ship for most Yocom, 1947:510

of one day; crew members saw other

white-bodied albatrosses in the area

prior to 1945

scattered singles and doubles

1

1 obtained in Kamchatka waters

25, maximum number seen at single

sighting; generally more common in

western Pacific than other areas

regular and not uncommon visitor; not

as plentiful as Black-foot

maximum number 14 ca. 240 mi S

southern tip Kamchatka; other sightings mostly scattered singles; none

seen in western Bering Sea; suggested

temperature preference is 7°-8°C

maximum numbers (2.5 per hr) seen at

180°

second in abundance only to Rissa tridactyla; winter banding returns for

coastal Japan; suggests wintering birds

are nonbreeding young

more common here at this time than in

NE Pacific in previous February

6, closest sighting to land during 5

trans-Pacific trips

westernmost and southernmost position

at which sighted

suggests main summer range off Japan

as N of 40°N; main winter range S of

35°N (quoted by Kuroda, 1963:234)

only time species seen during 36 days

at sea, including 2 days off southern

and central Japan

1

1

regular occurrence in area implied

McHugh, 1950:153-154

Agnew, J. H. in Bourne, 1961:12

Dementev and Gladkov, 1951:347

Poole, 1966:72

Austin and Kuroda, 1953:300

Kuroda, 1955:292

Hamilton, 1958:160-162

Kuroda, 1963:234

MacDonald and Lawford, 1954:16

Poole, 1966:71-72

MacDonald and Lawford, 1954:16

Yamashina, 1942:247 [in Japanese]

Wilhoft, 1961:260

Nakamura, 1963:241-243

Mitchell, J. B. in Bourne, 1961:12

Lamb, K.D.A. in Bourne, 1961:12

2 Agnew, J. H. in Bourne, 1961:12

1 Nakamura, 1963:241-243

see text herein King, 1970:9

1, apparently southernmost record for Peakall, 1960:199

month

3 Thompson, 1951:234

1, southernmost record for species " " "
The Storm Petrels (Hydrobatidae)

Richard S. Crossin

Introduction

The family Hydrobatidae consists of a group of

morphologically similar species distributed over

most of the pelagic waters of the earth. At least 15

species and a variable number of subspecies (depending upon the reviewer) are found in the areas

of the Pacific Ocean covered in the present work.

Many of these species are included in the genus

Oceanodroma which contains groups of sibling species, often only separable with some difficulty in the

hand, and presenting considerable problems to the

observer in the field. The pelagic ranges, as well as

other aspects of the life histories of most of the

Pacific forms, are little known; for some species

even the breeding grounds are unknown. Austin

(1952) discusses the taxonomy and breeding stations

of most north Pacific species but deals little with

pelagic distribution or other aspects. Palmer (1962)

covers those hydrobatids that occur in North American waters, but the pelagic distribution maps are

inadequate. In many cases lack of knowledge of

pelagic distribution of a species is admitted by

placing a large question mark in an area. For other

species range maps are presented with little or no

information given as to the type of records (specimens, sightings) used to determine the distribution

area shown. Murphy (1936) discusses the forms

found in waters off the South American continent,

as well as many species found to the north. Despite

the considerable ornithological work since these volumes were written, there has been little or no new

information gained regarding many species of

hydrobatids considered therein.

Richard S. Crossin, Neotropical Ornithological Foundation,

J719 North Huachuca, Tucson, Arizona 85705.

* Paper Number 84, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

The major reason for lack of positive knowledge

regarding Pacific Ocean hydrobatids is the logistics

problem with which the student of these seabirds

must contend; the Pacific is a vast area where ports

are few and far between, and shipping is primarily

restricted to large commercial or military vessels.

Harrison (1962) had a rather exceptional opportunity of making seabird observations while aboard

Royal Navy ships. King and Pyle (1957), Szijj

(1967), and others have gained information while

on trans-Pacific research cruises. The unique opportunities of consistent area observation available

to the Smithsonian Institution's Pacific Ocean Biological Survey Program (POBSP) during the course

of field work from 1963 to 1968 have added a wealth

of new information not only on Pacific hydrobatids,

but on Pacific seabirds in general.

In this paper I shall not attempt to summarize

all information available from other sources on the

forms of hydrobatids under consideration. Rather

I shall present the recently acquired POBSP data,

with inclusion of previous data only when it seems

necessary for cogency. The POBSP data on Pacific

hydrobatids covers essentially four categories: (1)

pelagic distribution, (2) breeding biology, (3) molt,

(4) taxonomy. As might be expected, unequal

amounts of information in these categories were

acquired for the various species concerned. These

data are presented in the species accounts.

Throughout the course of POBSP studies, a variety

of vessels were utilized: United States Department

of Interior, Bureau of Commercial Fisheries ships;

United States Navy vessels; Scripps Institution of

Oceanography research vessels; United States Coast

Guard ships; leased fishing ships; and others. POBSP

observers normally worked in rotating two-man

teams who were on watch constantly during daylight hours and occasionally at night. On cruises

154
NUMBER 158 155

with only a single POBSP observer aboard, he usually observed from dawn to dark with intermittent

breaks. All bird sightings were recorded with accompanying pertinent data. The recording of time

of day at each sighting permitted interpolation of

latitude and longitude positions from the ships'

cruise charts. Weather and oceanographic conditions were coupled to each sighting when possible,

and all information was later transferred to magnetic tape from which rapid summations of data

for single species or species groups could be drawn

for analysis. For a more comprehensive view of the

Automatic Data Processing program, see King, Watson, and Gould (1967). As field work was performed

for the most part on a year-round basis, migrational

patterns, seasonal movements, and other factors can

be analyzed to determine variations present in seasonal timing and areas utilized by the various species concerned. During the course of POBSP activities

some 12,574 observations covering 27,140 individuals of the family Hydrobatidae were recorded.

Regular and periodic surveys of islands used for

nesting within the area of investigation allow for a

more complete understanding of the pelagic observations. Specimen collecting accompanied pelagic

observations whenever feasible. Artificial oil slicks

(see Murphy, 1936:8) were often put out specifically

to attract hydrobatids.

During the course of the study 650 specimens of

11 hydrobatid species were collected. Most specimens collected and observations made were of the

various subspecies of the Leach's Storm Petrel

(Oceanodroma leucorhoa). The means, with standard errors and standard deviations, are given in

Appendix Tables A to E for all standard measurements of the POBSP specimens of leucorhoa races, as

well as of other species. All wing measurements are

of the chord. In comparing chord measurements

with measurements of the flattened wing on storm

petrels, I find extremely little difference between

the two.

AREA COVERED BY POBSP.—Gould (Figure 1)

shows the approximate outlines of the areas surveyed during all POBSP cruises from August 1963

through April 1968. All portions of those areas were

not comparably surveyed in regard to total coverage

or to time of year. Without question, certain areas

received consistent and by far more regular coverage than other areas, which were surveyed only once

or very irregularly. By and large, the area surveyed

falls into two major regions: the central Pacific

and the central eastern Pacific (hereafter referred

to as the eastern Pacific). The former was surveyed

almost constantly from 1963 to 1967. The latter was

surveyed intensively during 1967 and 1968. Intermittent cruises were also run in the Alaskan area.

FIELD IDENTIFICATION.—As a group, the various

white-rumped and dark-rumped storm petrels in

the Pacific present as great an identification problem to the field worker as any two groups of sibling

species known. I have no doubt that each species

has its peculiar identifying characters and that under ideal conditions most individuals might be

properly identified to species, but sightings in the

field are seldom under ideal conditions. In fact, it

is unusual when weather, lighting, distance and

other factors are satisfactory for positive identification. Most sightings are assigned to species only by

inference and deduction.

In 1965 Wilson's Storm Petrels (Oceanites oceanicus), a totally unexpected species, were collected

for the first time in the central Pacific. No doubt

some were seen during late 1963 and 1964, but were

erroneously recorded as Leach's (Oceanodroma leucorhoa) or Harcourt's Storm Petrels (Oceanodroma

castro). Continued collecting after 1965 with the resultant procurement of scattered specimens of Wilson's, plus a detailed survey of migration in the

central Pacific (Huber, 1971) have shown that these

birds apparently move through the Pacific (Marshall Islands area, at least) in considerable numbers,

and are scattered throughout the central Pacific in

small numbers during the migratory period. Any

purely visual identification made of storm petrels

in an unknown area is, in my opinion, speculative.

In the central Pacific, identification problems

were greatest for Leach's, Harcourt's, and Wilson's

Storm Petrels, all white-rumped forms. The latter

two were present in fewer numbers than Leach's.

Random collecting performed throughout the area

allowed for a fairly good estimate of the percentage

of each species present.

In the eastern Pacific the situation was considerably different in that both white-rumped and

dark-rumped forms were present. Although more

species were involved, the majority of these were

sufficiently diverse to allow reasonably accurate

field identification. General collecting proved even

more fruitful here than in the central Pacific, as

certain forms, such as the two races of the Gala-
156

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

120° 110° 100° 90°

FIGURE 93.—POBSP sightings and specimens of Pelagodroma marina.

10

70°

pagos Storm Petrel (Oceanodroma tethys), are readily separable in the hand. Thus in a situation such

as this, the ideal is realized in that a collected specimen not only provides positive identification of the

species, molt, food, and gonadal information, but

allows for designation of the at-sea range of a specific geographic race.

Hence, despite the problems connected with field

identification of hydrobatids, observations made

during the POBSP surveys can be discussed with a

considerable degree of assurance for the following

reasons: (1) the observers concerned had an extraordinary opportunity to gain experience in field

identification during extensive periods of work at

sea under every conceivable condition, and (2)

most at-sea observations were backed by random

collecting; this constant procurement of specimens

throughout various areas provided a constant check

on visual observations.

ACKNOWLEDGMENTS.—The following made important observations and collected field data pertinent

to hydrobatids during the program; without their

contributions, this paper could not have been written: A. Binion Amerson, Jr., Richard D. Chandler,

Roger B. Clapp, Robert L. DeLong, Patrick J.

Gould, C. Douglas Hackman, Brian A. Harrington,

Lawrence N. Huber, Dayle N. Husted, Warren B.

King, Horace Loftin, Max C. Thompson, and Paul

W. Woodward. (For a more complete listing of

POBSP personnel and objectives of the Pacific Program, see Gould, pp. 1-5, herein.)

I also wish to thank the following individuals

who aided the writing of this paper in their respective ways. Philip S. Humphrey, as Principal Investigator of the Pacific Program, offered valuable advice and encouraged the writing of the present

work. Dean Amadon of the American Museum of

Natural History in New York and Joseph R. Jehl,

Jr., of the San Diego Natural History Museum

made available the hydrobatid specimens in their

charge. Carl L. Hubbs of Scripps Institution of

Oceanography generously offered me the use of his

field notes and preliminary consolidated data on

hydrobatids from the eastern Pacific islands, espe-
NUMBER 158 157

FIGURE 94.—POBSP sightings of Oceanodroma furcata. (Breeding localities are largely from

Palmer, 1962).

daily Guadalupe. Oliver L. Austin, Jr., reviewed

the manuscript and offered valuable suggestions.

Ralph Browning donated his time and effort to

performing much of the tedious work of measuring

specimens. Anne K. Poulson prepared the illustrations.

Pelagodroma marina (Latham)

WHITE-FACED STORM PETREL

PELAGIC DISTRIBUTION.—Most POBSP pelagic records of this basically southern hemisphere hydrobatid are from west of the Galapagos Islands. Practically all sightings fall within a triangular area

with points at 5°N, 112°W; 8°S, 112°W, and 3°S,

100°W (Figure 93). Two adult females were collected by the POBSP on 24 August 1967 at 6°19'S,

111°55'W. Three other specimens taken in the eastern Pacific (two near the Galapagos, one near Ecuador) are mentioned in Murphy (1936:768). LeVeque,

et al. (1966) report a specimen collected in September 1930 about 100 miles southwest of the Galapagos, and two sightings in August 1960 and seven

sightings in July 1961 about halfway between the

Ecuadorian mainland and the Galapagos.

The similarity of south Atlantic (Tristan da
158 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Cunha Islands) and south Pacific (Australia-New

Zealand) subspecies makes it difficult to assign origin to specimens collected near the Galapagos.

Murphy (1936:768), while implying that some form

of this species was probably resident in the eastern

Pacific, left the question of origin open. Most likely

these eastern Pacific records pertain to members of

the Australian-New Zealand populations, which

migrate to the South American coast and follow the

Peru Current north and west through the Galapagos region. The large number of records west of the

Galapagos in August and September (84% and

14%, respectively, of total POBSP sightings for those

months) indicate a buildup prior to the return to

the Australian-New Zealand breeding grounds

where egg-laying takes place in late October. The

condition of our August specimens (in terminating

stages of complete molt and with moderate fat) is

in accord with the condition of other procellariiforms prior to a prebreeding migration. Murphy

(1936) and Palmer (1962) summarize the known

biology of the species.

Oceanodroma furcata (Gmelin)

FORK-TAILED STORM PETREL

PELAGIC DISTRIBUTION.—This species was observed commonly on all POBSP cruises in the central

and eastern Pacific north of 40°N (Figure 94). A

region of high density off the California coast between 31 °N and 36°N probably consists of birds

from the northern California or Oregon populations. An obvious straggler was observed on 22

February 1968 feeding on refuse behind a ship in

the company of several Black Storm Petrels (Oceanodroma melania) near the southern tip of Baja

California. POBSP collected only a few specimens of

nominate O. f. furcata near the Aleutian Islands;

thus most of our pelagic sightings are not referable

to race.

Oceanodroma leucorhoa leucorhoa (Vieillot)

LEACH'S STORM PETREL

PELAGIC DISTRIBUTION.—The nominate race of

Leach's Storm Petrel is distributed in its at-sea

range over much of the Pacific Ocean with a decided center of abundance in the central Pacific.

Measurements of normally used characters of all

specimens collected (Figure 95) in this area are compared with known breeding O. I. leucorhoa from

the Alaskan area in Appendix Table B. It can

easily be seen that central Pacific birds fall well

within the range for nominate leucorhoa. As a

whole, the specimens are comparable both in measurements and other more subtle morphological

characters with nominate leucorhoa from the

breeding grounds. However, because of the difficulty involved in separating nominate leucorhoa

from O. I. beali, the presence of a small percentage

of the latter in the central Pacific is not to be excluded.

Oceanodroma I. leucorhoa attains greatest winter

densities in a broad belt along the equator. Numbers drop rapidly to the south, and south of 12°S

only an occasional individual is sighted. Waters to

the north of this equatorial high-density area present problems of seasonal density specification.

High density in small sectors north of the equatorial complex is probably due to several factors,

among which are local, temporary, high concentrations of food. Additionally, late fall and early

spring migrants may tend to mass at certain points

in the northern sector of the wintering grounds before moving on south or north, as the case may be.

Birds are found throughout the central Pacific wintering grounds throughout the year, with decided

buildups of wintering birds as would be expected

(compare Figure 96 "Summer" with Figure 97

"Winter").

The number of summering birds is considerable,

but their age status is uncertain. In the Atlantic

population of the nominate race, birds presumably do not breed until three years of age, but twoyear old birds may return to the colony during the

breeding season (Wilbur, 1969). Wilbur (1969) implies that first-year birds might fly over the colony

without entering it; he apparently has no positive

evidence for this in the form of banded birds.

Huntington (pers. comra.) informed me that of

eleven breeding birds banded as nestlings, the

youngest were four years old; of thirteen banded

birds mist-netted over the colony, breeding status

unknown, the youngest were three years old. There

may be considerable individual variation among

one- and two-year old birds in regard to their return to the breeding colony.

The only other explanation for the large number of birds that summer in the central Pacific is
NUMBER 158 159

180

FIGURE 95.—Localities of collected specimens of Oceanodroma leucorhoa leucorhoa in the central

Pacific.

that for some reason, some adults do not return to

the breeding colony every year. Both Huntington

(1963) and Wilbur (1969) record that approximately 50 percent of birds banded while nesting

one year are found nesting the following year. Unless we assume some birds were missed in the study

plots or had moved elsewhere, this seems to be an

exceptionally high mortality rate. Possibly some

adults that successfully raise a chick one year do not

return to the breeding grounds the following year.

The migrational pattern of nominate leucorhoa

is largely obscured by the high densities of sum-
160

170 W 160'

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

150° 140° .

150° 140°

FICURE 96.—Summer densities (May, June, July, August) of Oceanodroma leucorhoa leucorhoa.
NUMBER 158 161

160 E 170 180" 170 W 160 150 140° o

—130

20'

10"

20

Birds per square mile

.01 -.10

if!-11--

20

•1.21 +

20

10°

,20

160 140° ° 170 180 170 160° 150°

FIGURE 97.—Winter densities (November, December, January, February) of Oceanodroma

leucorhoa leucorhoa.

mering birds, and is more readily ascertained by

field observations of flocking birds rather than by

actual increases or decreases in recorded density.

The spring migration north begins in March and

probably occurs sporadically throughout April,

since April densities in the central Pacific are still

far greater than in mid-summer when most breeding birds are on the breeding grounds. The fall migration south is also largely obscured by summering birds, but definite density increases are noted

southward to the high-density equatorial center as

early as September. At this time of year breeding

birds would still be expected on the breeding

grounds or at least in more northerly latitudes.

These early fall buildups in the equatorial area

may either be of birds that have experienced nesting failures, and thus have left the breeding

grounds earlier than the successful breeders, or of

prebreeders that have spent the summer farther

north and have returned to more southerly latitudes

for the winter. As it is virtually impossible to distinguish immature prebreeders from adult breeding birds when the latter's gonads are in a winter

quiescent stage, collected specimens from these sea-
162

20

10°

s

10"

130

110°

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100° 90

"140°

1 bird

5 birds

30"

Islobela I., A -

Galapagos j

Islands

10"

120°

10°

no 100° 90°

FIGURE 98.—Localities of collected specimens of Oceanodroma leucorhoa leucorhoa in the eastern

Pacific Ocean.
NUMBER 158 163

sons do not lend information as to their recent

breeding activities.

Movements and distribution of the nominate

race throughout the eastern Pacific are less clear

because of the difficulty of separating individuals

from the abundant O. I. beali, which winters prominently along the western American coast. A few

specimens from the eastern Pacific are clearly referable to nominate leucorhoa by their greater size;

collecting localities of these are shown in Figure 98.

Aside from POBSP specimens, Loomis (1918:182)

mentions three specimens collected south of the

Galapagos Islands whose measurements indicate

their allocation to the nominate race. Palmer (1962:

227) mentions examples of the nominate form taken

off the coast of Ecuador. Comparatively, the numbers of these eastern representatives are low and

the equatorial high-density area between 170°W

and 175°E is, if not the center of winter abundance, one of the most important of such centers.

TAXONOMY.—Considerable taxonomic work was

performed on available POBSP specimens during the

course of this study in the hope that the ability to

distinguish races of at-sea collected specimens would

allow for a clearer picture of their respective at-sea

ranges. In some cases this was possible, but many

individuals cannot be designated unconditionally to

a particular race. Concerning the Pacific races of

Leach's, Austin (1952:400) stated: "On dimensions

alone these are all weak races. Despite significant

differences between the means of some characters,

fewer than half the individuals of many of the

recognized subspecies are distinguishable." Despite

the recently collected large series of most of the

races concerned, we are no better off in regard to

solving these problems. Austin's (1952) arrangement of the various Pacific subspecies of Oceanodroma leucorhoa is followed here. The unusual

situation concerning O. I. socorroensis at Guadalupe Island and the possible need for revision of

the taxonomy of that population is discussed beyond.

In working with fresh series of recently molted

birds of all populations, I find that little significance can be attached to the oft-mentioned character of a lead bloom to the plumage of the northern races, which is supposedly most prominent in

nominate leucorhoa. All races in very fresh plumage show this particular bloom but with considerable individual variation, and this particular cast

is lost quite rapidly, both in living birds and in

museum specimens. Freshly molted series of either

O. I. chapmani or O. /. socorroensis show this character as prominently as newly molted nominate

leucorhoa from the Alaskan area, although the

overall plumage is admittedly considerably darker

in the southern races. Juvenile socorroensis from

Guadalupe are especially prone to show this particular character, but drastic differences exist between new and old plumage. When the plumage

is several months old the entire feather coat in all

races is of a washed-out brown hue in addition to

its ragged condition, with hardly a trace of the rich

charcoal present in new featheration. Body contour

feathers, as well as flight feathers, are badly worn

at the end of a plumage sequence. Of the flight

feathers, primaries appear to take the most wear.

In contour feathers, those about the head and neck

appear most subject to wear and at the beginning

of a new molt sequence these are often no more

than ragged portions of the original appendages.

Only in the case of exceptionally large individuals of O. I. leucorhoa, and exceptionally small individuals of O. I. socorroensis, can birds of the leucorhoa complex be segregated with any degree of

certainty. As is evident from the measurements in

Appendix Table B, nominate leucorhoa from the

Alaskan area is the largest of all races. While the

average individual of the nominate race has a generally more massive bill, this subtle difference is

useful only in direct comparison of specimens, and

does not lend itself meaningfully to mensural application.

MOLT.—Members of the nominate race of Leach's

that enter the central and eastern Pacific from

northern breeding grounds, as well as year-round

semipermanent residents there (nonbreeders), are

already undergoing a pronounced primary molt by

July. This continues in some individuals throughout the fall and winter (to December or even later).

In a large percentage of birds the entire primary

molt has been accomplished by November, and in

exceptional individuals by October (Figure 99).

For many others this molt may not terminate until

April. It cannot be determined whether individuals

finishing primary molt from, say, February through

April, are birds that have a very prolonged cycle or

whether they are individuals that began molt very

late in the year. Primary molt can be clearly ascertained and follows a set pattern of replacement of
164 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100

90

80

70-

60-

5 50

s.

40

30

20

10

July

N=6

I I Old

3 Molting

Non-molting

FIGURE 99.—Seasonal molt stages in Oceanodroma leucorhoa leucorhoa. The percentages of new,

growing, and old primaries and rectrices are calculated from direct count of all birds in each

respective sample; narrow portion of bar equals nonmolting percentage of sample, wide portion

of bar equals molting percentage of sample, (n = sample size.)

new feathers from the innermost to the outermost

primaries with corresponding feather pair members

of each wing coincident or very closely attuned.

Most individuals of chapmani and socorroensis, returning to the breeding islands, were in terminal

stages or had very recently completed a body and

primary molt. Some individuals were still growing

the outermost (tenth) primary as defeatheration of
NUMBER 158 165

the brood patch and gonadal enlargement were occurring. We took no specimens of either beali or

leucorhoa on any breeding grounds except for

willetti ( = beali) on the Coronados Islands.

Rectrix molt, like the preceding, is already well

along in our July sample of O. I. leucorhoa, and is

for all practical purposes, finished by November.

Only a few isolated individuals show any evidence

of rectrix molt during the period from January

through May. There seems to be no set pattern of

rectrix molt except that opposite members of a pair

of tail feathers are generally molted at the same, or

at nearly the same time.

Investigation of the molt pattern of the secondary feathers was less satisfactory because of the difficulty of working with study skins in these small,

long-winged birds. In general, it appears that the

outer secondaries begin to molt at about the time

the first primaries shed, and molt then proceeds

progressively toward the body. Secondary molt is

closely parallel to primary molt and is usually terminated before the last primary has finished growing.

Extensive body molt of the contour feathers in

the nominate race begins in November and is apparent in a decreasingly smaller number of individuals through April. Body molt is generally distributed over most of the body; the crown and

throat regions and the primary and greater coverts

are the last areas to replace feathers. The various

races of Leach's show certain variations in molt patterns.

No doubt much of the variation in molt between

individuals of the nominate race can be attributed

to differences between juvenile, immature, and

adult breeding birds. However, I cannot satisfactorily separate immature birds from adults on the

wintering grounds after the latter's gonads have

regressed, except for truly adult females, which

form only a small part of our sample. The more

extensive lighter margins of the coverts and the

scapulars, and the wrinkling of the nostril area in

study skins, which are supposed to be good characters for separating juvenile birds from older individuals, are not positive determinants and at any

rate these differences disappear within the first year

of life. Hence, the monthly samples shown in the

molt graphs are unquestionably made up of a variety of age classes.

Oceanodroma leucorhoa beali Emerson

BEAL'S STORM PETREL

PELAGIC DISTRIBUTION.—Our at-sea observations,

backed by routine collecting of specimens throughout the eastern Pacific (Figure 100), have determined that O. I. beali winters throughout a broad

area south of the breeding grounds from northcentral California (northern limit of recurrent

POBSP cruises) to at least 20°S. South of 10°S decreasingly lower densities are recorded. Within this

extensive area the distributional picture is somewhat confused because of the admixture of certain

other white-rumped forms, such as a scattering of

identifiable nominate leucorhoa, O. I. socorroensis

and two races of Galapagos Storm Petrels (O. tethys

tethys and O. t. kelsalli). Nevertheless dense wintering populations of beali are found off both central

and southern California and throughout a broad

area from ca. 26°N to ca. 8°S, between 90°W and

120°W (Figure 101). Although not readily apparent

from the density distribution maps, these are the

areas most heavily surveyed by the POBSP. Hence,

as is often the case, graphic display of geographical

distribution of an organism more often tends to

show distribution of the researcher rather than of

the organism. The POBSP has not surveyed to the

west or south of the areas involved in EASTROPAC

cruises. Our summer cruises in the eastern Pacific

only extend to ca. 5°S; densities of O. I. beali are

fairly high to that point (Figure 102).

It may be noted that the density figures in the

O. I. beali pelagic distribution charts are considerably higher than those for O. I. leucorhoa in the

central Pacific. Despite the fact that more forms are

involved in the eastern area, actual eastern Pacific

densities for all races of leucorhoa are roughly

three times greater than those recorded in the central Pacific. Since the magnitude of observations

under varying conditions in both areas would eliminate, or render insignificant, any temporary variations in the data gathering, the differences in

density consistently recorded between these two

areas must be regarded as real.

TAXONOMY.—Austin (1952) synonymizes both

O. I. beldingi from the northern California coast,

and O. /. willetti from the Coronados Islands, with

O. I. beali. Hence, O. I. beali applies to all Leach's

Storm Petrels breeding along the North American

west coast from extreme southeastern Alaska to the
166

130 W

20

10

130e

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100° 90° .

• 1 bird

• 5 birds

40

30°

l.abela I.. '

Galapagos

Islands

120° 110° 100°

FIGURE 100.—Localities of collected specimens of Oceanodroma leucorhoa beali.

10"

10

90°
20 -

130

20

70"

FIGURE 101.—Winter densities (November, December, January, February, March) of

Oceanodroma leucorhoa beali.
168 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

13C w 70" 0

50

10°

0°

Birds per square mile

.01 .20

40-

30

130° 120° 110° 100° 90° 80°

FIGURE 102.—Summer densities (May, June, July, August) of Oceanodroma leucorhoa beali.

Coronados Islands* just south of the United StatesMexican border. Although this eliminates the confusion involved in attempting to recognize more

than one form along the United States west coast,

many individuals in this complex cannot be distinguished from nominate leucorhoa to the north;

a considerable number of individuals from the

Coronados population cannot be distinguished

from either dark-rumped O. I. chapmani from the

San Benitos Islands (along the west-central coast
NUMBER 158 169

•o I

FHUJRE 103.—Seasonal molt stages in Oceanodroma leucorhoa beali. (See Figure 99 for explanation of symbols.)

of Baja California), or O. I. socorroensis of Guadalupe Island.

BREEDING BIOLOGY.—A number of authors record

the nesting of O. I. beali along the western North

American coast; among these are Grinnell and

Daggett (1903), Willett (1915), Howell (1920),

Bailey (1927), E. W. Martin (1938), and Campbell

and Stirling (1968). The consensus of these reports

is that beali nests from at least April through September. Eggs are recorded from June to August,

and young from July to September. An exceptionally early record of the Coronados Island population ( = willetti of the 1957 A.O.U. Check-list) is that

of a three-quarter grown downy young taken 27 April 1929 (specimen in the San Diego Natural History Museum). Other specimens from the Coronados in that institution were collected between 6

July and 5 September. A few of the September

birds are small downy young that probably would

not have left the island until October. The POBSP

captured three dark-rumped birds of the Coronados

population in a mist net on the night of 30 June

1968 on Center Island. No nests were found; the

population at that time could not have exceeded

100 birds.

MOLT.—The molt sequence of O. I. beali is

graphically demonstrated in Figure 103. From our

collected samples, beali appears to have a larger

percentage of individuals undergoing primary molt

during the prebreeding months (February-May)

than O. I. leucorhoa. Fall primary molt (probably

concerned with immatures) is terminated more

rapidly than in O. I. leucorhoa. Rectrix and body

molt are basically the same in beali and nominate

leucorhoa.

Oceanodroma leucorhoa chapmani Berlepsch

CHAPMAN'S STORM PETREL

PELAGIC DISTRIBUTION.—The pelagic distribution

of this form is little known, and POBSP surveys have

not been informative. Although the race is characterized by the fact that all members have a dark

rump, its presence at sea is difficult to determine

because it is indistinguishable from dark-rumped

birds of both the Coronados and Guadalupe Island

populations present in the same area. Although

we have a considerable number of sightings of darkrumped birds from both the northern cruise areas

and the southern EASTROPAC areas, it is impossible

to assign racial designation to these sightings. An

admixture of collected specimens of dark-rumped,

intermediate, and white-rumped birds of small size

from the eastern Pacific are in most cases definitely

assignable to socorroensis. It is not possible by

measurements to separate definitely all dark-rumped

socorroensis from chapmani. We have collected

few, if any, chapmani at sea. On the basis of the
170

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

limited number of small, dark-rumped specimens

taken, however, it may be that this race winters

much closer to the coast than do beali, leucorhoa,

or socorroensis.

BREEDING BIOLOGY.—This dark-rumped form of

Leach's breeds predominantly or exclusively on the

San Benitos Islands off west-central Baja California.

During a POBSP survey of these islands from 26 to 29

April 1968, birds were plentiful on all three islands.

At that time they were calling from the air, as well

as occupying empty burrows and cavities among

the rocks. No eggs were found. Several adults were

discovered fatally impaled upon the spines of the

rampant cholla cactus (Opuntia sp.). A later June

survey noted 14 such individuals on one slope.

During a 25 to 27 June 1968 survey, most birds

were still calling from empty nest sites; some 20

percent of the population were on fresh to heavily

incubated eggs, but no chicks were found. The

birds occupy every feasible habitat on the islands

for nesting, with possibly the talus slopes and rocky

areas preferred. In these habitats they are in competition for nest sites with the Black Storm Petrel

and Least Storm Petrel (Halocyptena microsoma).

Some chapmani used abandoned Cassin's Auklet

(Ptychoramphus aleutica) burrows, but a number

were noted digging their own burrows. DeLong

(POBSP) records that "despite the apparent weakness

of the bony structure of the legs, they dig with

great fervor and make the soil fairly fly."

The species' nocturnal and secretive nesting

habits make it extremely difficult to arrive at more

than a rough estimate of the population size. For

the June 1968 survey this was set at 50,000 birds

for the island group.

Oceanodroma leucorhoa socorroensis Townsend

SOCORRO STORM PETREL

PELAGIC DISTRIBUTION.—O. I. socorroensis were

found at sea as far north as 35°N and south to

10°N. A considerable number of specimens were

taken southeast of the breeding island of Guadalupe. As socorroensis cannot be distinguished in the

field with any degree of certainty, all records are

based on collected specimens (Figure 104). In late

February 1968 near 10°N, and between 100°W and

110°W, sizeable concentrations of socorroensis were

recorded in mixed flocks composed of Oceanodroma

tethys tethys, Oceanodroma leucorhoa beali, and a

few large specimens that are best referable to O. I.

leucorhoa. No socorroensis were collected below

10°N, although extensive collecting was done

throughout the cruise in these longitudes to 20°S.

The western limits of the pelagic distribution are

unknown. From our evidence, apparently socorroensis does not range as widely from the breeding

grounds, nor as far from the coast, as do beali or

leucorhoa.

TAXONOMY.—This race is the smallest and most

variable in rump color of all forms of leucorhoa in

the Pacific. The characters of greatest use in separating this from other races are wing and bill

length, and the overall slightness of the bill.

Weights, when available, are also useful in demonstrating the small size.

A series of 109 POBSP specimens from the summer

breeding population show a range of wing length

from 135 mm to 150 mm with a mean of 141.89.

Austin (1952) records 25 socorroensis with wing

length ranging from 141 mm to 157 mm, and with

a mean of 148.8 ± .88. Another series of winter

breeding birds composed of POBSP specimens as well

as specimens from the San Diego Natural History

Museum contains 19 males with a wing length

range of 141 mm to 150 mm, and 18 females with

a range of 140 mm to 147 mm. With this overall

range of from 140 mm to 150 mm for both sexes

(although close to the 135 mm to 150 mm range

for summer socorroensis) the winter birds tend to

be slightly larger, although there is complete overlap between winter and summer birds. Considering

all birds of both winter and summer populations

from a sample of 146 birds, the range is 135 mm

to 150 mm. This large sample should totally blanket Austin's sample of 25 birds, but his series shows

considerably larger measurements in both range

and mean. His sample apparently contains both

winter and summer Guadalupe birds and also apparent stragglers (probably of O. I. beali) taken offshore Guadalupe. For example, several obvious

beali (by their worn plumage and measurements)

taken offshore in winter were found in the series

of socorroensis in the San Diego Museum.

The winter breeding population on Guadalupe

of slightly larger birds is in need of considerable

investigation. If this population is sufficiently different to warrant subspecific recognition, the appropriate name would be Oceanodroma leucorhoa
NUMBER 158 171

130° W no"

N

20

10

100

-140°

• 1 Bird

Breeding locality

30"

10

130 120 110 100

FIGLRE 104.—Localities of collected specimens of Oceanodroma leucorhoa socorroensis.

kaedingi. For convenience, I will refer to the win- ing population, socorroensis. Besides their slightly

ter breeding birds as "kaedingi" to differentiate larger size, kaedingi are, in part, further distinthem from the currently recognized summer breed- guishable from socorroensis by rump color. All 37
172

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 105.—Variation in rump color of Oceanodroma leucorhoa socorroensis from Guadalupe

Island.

winter-breeding kaedingi examined are whiterumped, the amount of white ranging from 2

through 4 on a scale of 0 to 5 measuring the amount

of white in the rump. The series of 37 showed the

following scale figures: 2 (14%), 3 (40%); intermediates between 3 and 4 (11%); and 4 (35%). Thus

an average bird of this population would have

rump color of slightly over 3, about comparable to

that of O. I. beali. Summer socorroensis, on the

other hand, have rump color ranging from categories 0 through 5, or from pure dark to pure

white rumps (Figure 105). Austin's (1952:401) statement characterizing rump color of socorroensis,

"rump patch variable, almost always with some

white, but never as much as in typical beali," is

not quite true. As discussed in the breeding biology

section, 90 percent of the birds breeding on Islote

Negro in June 1968 had pure dark rumps. Conversely certain individuals taken off Islote Afuera

have a pure white rump; even the feather shafts are

white (as in Oceanodroma castro), a condition that

rarely occurs in any race of leucorhoa. Obviously

these differences between socorroensis and kaedingi

are insufficient to permit racial designation of most

individuals taken away from the breeding island,

so at present it is useless to attempt to recognize

these two populations as taxonomically distinct.

These differences, however, are neither more nor

less than those displayed by most named subspecies

of leucorhoa. A small- to average-sized O. I. chapmani from the San Benitos Islands would be indistinguishable from a dark-rumped socorroensis

from Guadalupe Island, as would a large chapmani

be indistinguishable from a dark-rumped "willetti"

(=beali) from the Coronados. Unfortunately we

are dealing with populations that show few external

morphological differences. Nevertheless the winter

breeding population at Guadalupe, whether it is

recognized as a distinct race or not, undoubtedly

differs physiologically from the summer population. Despite equalizing ocean temperatures, Guadalupe is at a fairly high northern latitude (29°N)

with a considerable difference between summer and

winter temperatures. The possibility exists that

food items available to the young in the surrounding waters differ considerably between winter and

summer. To my knowledge kaedingi is the only

hydrobatid (besides Oceanodroma tristrami) in the

northern hemisphere that nests in the northern

winter.

BREEDING BIOLOGY.—Oceanodroma leucorhoa socorroensis breeds only on Guadalupe Island, some

200 miles west of Baja California, Mexico. The

POBSP surveys, as well as numerous surveys by Carl
NUMBER 158 173

Hubbs of Scripps Institution of Oceanography and

other parties, have shown that at least the bulk of

the storm petrel population is now restricted to

breeding on tiny offshore islets free of introduced

predators. The two best surveyed among these islets

are Islote Negro and Islote Afuera near the Mexican settlement at the southern tip of the main

island. We have indirect evidence that a sizeable

population may still breed on the main island

proper, but the actual nesting area has not been

discovered.

This race of Leach's has presented some of the

most puzzling problems of all forms studied. Between 22 and 23 June 1968 the populations on

both Islote Negro and Islote Afuera were surveyed.

On Islote Negro the estimated population of several thousand birds, judged by several hundred

handled at the nest sites, was composed almost

without exception of dark-rumped birds. On Islote

Afuera, only about a mile and a half away, we

estimated more than 90 percent of the population

were white-rumped. There appeared to be no morphological difference except rump color between

the two populations. This was inferred not only

from living birds, but from the series of skins collected at the time. Vocalization recordings of individuals from both populations were taken, but

these have not yet been analyzed. Suffice to say that

the field workers could discern no differences in the

calls of the two populations. To complicate matters even more, a series of about 50 birds collected

aboard ship on the night of 28 June immediately

off the southeast coast approximately 10 miles from

these islets, contained individuals with every conceivable rump color from white through completely

dark. Many of these were not in breeding condition,

but a considerable number of birds with intermediate-colored rumps had heavily vascularized brood

patches, indicating that eggs or young were already

present. Had these birds been part of the populations on either Islote Negro or Afuera, it seems certain that they would have been noticed. Hence, this

population was suspected of nesting somewhere on

the main island. Huber spent about eight hours

about the cliffs and among the pines on 29 June,

but found no breeding storm petrels.

No explanation is offered regarding the allopatric distribution on adjacent islets of these populations. That chance would be operative in segregating these color morphs appears to be a mathematical improbability, especially in view of the

number of individuals involved. The total exclusion of an influx of birds of opposing rump colors

can hardly be plausible. For the present, this confusing issue must await a more detailed study.

The nesting stages of the populations on these

islets on 22 and 23 June 1968 were as follows:

Islote Negro: The summer breeding population

on Islote Negro was estimated to be about 4000

birds. Storm petrels were found nesting over the

entire islet, but definite concentrations were found

wherever large masses of volcanic rocks were present, these apparently being the most favored sites.

Lesser numbers were found nesting in soil burrows,

excavated by Black-vented Shearwaters (Puffinus

puffinus opisthomelas) or Cassin's Auklets, and under dense mats of plant material. The storm petrels

themselves also excavated a considerable number

of burrows in the hard-packed soil. The tiny entrance holes to many extensive burrows indicated

that only storm petrels could have dug them.

Varying amounts of plant material in the form

of seed pods or dried stems (usually of the introduced ice plant, Mesembryanthemum sp.) were

used for nest linings. Nests in rocky areas usually

had very little nest lining, the eggs being deposited

on the sparse soil or on the rocks in some cases. The

population on Islote Negro at this time was approaching its egg-laying peak with an estimated 20

percent of the nests containing fresh eggs. Only a

single egg out of about 30 examined showed advanced incubation. The majority of the population appeared to be paired with completed or partially completed nest sites.

An occasional fresh egg was found lying on the

ground outside nest cavities. These were presumably inadvertently kicked out by the shearwaters or

murrelets, both of which utilized the larger nooks,

and rock or soil crevices. Many old storm petrel

eggs, presumably of the winter breeding population, were noted in and about active nest sites. It

appeared that the two populations frequently utilized the same nest sites. This seems reasonable, as

practically every good nest site was occupied by the

summer breeders.

Birds vocalized continuously through the night,

with a calling frenzy shortly after full dark. Most

birds called from burrows; a few called on the

wing.

All birds examined (a minimum of 500) on Islote
174 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Negro had dark rumps. The most white noted on

any bird was a few feathers at the sides of the

rump. In these individuals the feathers were more

gray than glaringly white.

Islote Afuera: Islote Afuera supported about 25

percent fewer birds than Islote Negro. The nesting

cycle was roughly in the same stage, with a somewhat higher percentage of nests with eggs. This

may have been due to the considerably less nest

construction necessary, as the vast majority of birds

on Islote Afuera occupied natural pockets and crevices in the lava rock instead of excavating burrows

in the sparse soil.

At least 90 percent of the birds on Islote Afuera

were white-rumped. Other than rump color, no

differences could be detected between the populations of the two islets. Except for the following records of immatures, we have few data pertaining to

later aspects of the breeding season of O. I. socorroensis. Huey (1930) records a juvenile with considerable down still adhering to the plumage that

came aboard ship about a mile off Guadalupe on

the evening of 27 September 1929, and another with

completely downy underparts that came aboard

ship 28 September, 26 miles north of Guadalupe.

The POBSP found flying young with down on ventral regions sitting around burrows at night on 21

October 1967 on Islote Negro. The latest date for

young of this population is a male juvenile with

completely downy underside that flew aboard a

ship off northeast anchorage, Guadalupe, on 12

November 1954. The three specimens mentioned

above are in the San Diego Museum of Natural

History. From the above records it can be surmised

that young socorroensis leave the islands throughout the fall and hence overlap with the winter

breeding population, at least from September

through November.

Measurements of a series of 20 eggs of the summer breeding populations of Islotes Negro and

Afuera are given in Table 28. Eggs of socorroensis

are white with a wreath of fine reddish brown dots

about the large end. The small size of socorroensis

is reflected in the egg dimensions when compared

to those of other races of Leach's Storm Petrel.

WINTER BREEDING POPULATION (O. /. kaedingi

Anthony).—More confusing is the status of the

winter breeding population that arrives on the same

islets before all the summer breeders leave (see

Hubbs, 1960). No POBSP survey was made during

TABLE 28.—Egg measurements of three subspecies

of Leach's Storm Petrel (Oceanodroma leucorhoa)

(data for O. I. leucorhoa and O. I. beali are from

Palmer, 1962)

Measurement

Length

with SD

(n = 20)

Breadth

with SD

(n = 20)

O. /. leucorhoa O. I. beali O. I. socorroensis

(Bay of Fundy) (NW U. S. coast) (Guadalupe Island)

3S.01±l.06

23.58 ±0.57

S1.46±1.S1

23.21 ±0.78

29.76 ±0.72

22.19 ±0.74

the height of the breeding season of kaedingi, and

we have few specifics pertaining to its cycle. It apparently begins coming to the islets in August, and

thus at least a portion of the two populations overlap, as not all the summer breeders have left the islets by this time. On 21 October 1967 on Islote

Negro, three pairs were noted during a mid-day

survey of the islet. Approximately 30 minutes after

sundown birds began appearing, and within an

hour an estimated 100 birds were calling from the

air and about 400 from rock crevices and burrows.

Previous mention is made of socorroensis juveniles

recorded at this time.

Specimens of juvenile kaedingi in the San Diego

Museum of Natural History indicate the extent of

the breeding season. J. R. Henderson took a threequarters downy young from a burrow on 31 January 1950 and Carl Hubbs collected similarly sized

young under a boulder on Islote Afuera on 11 February 1957. A juvenile with completely downy

belly was taken aboard ship by Hubbs at northeast

anchorage on 1 March 1965. A POBSP survey found

on Islote Negro on 29 April 1967 one large juvenile

with down on the venter. It apparently represented

the last of the 1966-1967 winter season kaedingi.

The June 1968 POBSP survey found about ten fully

feathered chick mummies on Islote Afuera (presumably birds of the winter breeding population). Only

one of these had a dark rump. All previously collected winter birds were white-rumped.

The conditions that cause two or more populations of the same species, or of different species, to

utilize the same geographical area for nesting at

different times of year appear to be the presence

of vast uniform feeding grounds, coupled with very

limited land space for breeding. Much the same
NUMBER 158 175

100

90-

80

70

60-

c

» 50-

£.

40-

30-

20-

10-

New YZAGr I I Old olting Non-molting

FICURE 106.—Seasonal molt stages in Oceanodroma leucorhoa socorroensis.

(See Figure 99 for explanation of symbols.)

situation occurs at islands across the equatorial

Pacific where two or more colonies of the same

species breed on the same island at different times

of the year. This is most noticeable in the Phoenix

and Line groups with the Sooty Terns (Sterna

fuscata) because the colonies are exceedingly large.

However, species that are found breeding all

months of the year, yet with a known changeover

of marked individuals (such as the White Tern,

Gygis alba) must be doing the same thing, only

in a less dramatic way. How these species arrive at

such "shift-work" utilization of an island is little

known, but the factors bringing about such a situation are obvious. Aside from a shortage of actual

physical space on these small islands, and the possibility of insufficient food in the surrounding waters to support the entire population at any one

time of year, the social stresses between individuals

would prohibit reproduction if all birds were to

occupy the same area at one time.

MOLT.—Our samples, except for late summer, are

too small and disjunct in regard to time of year to

be especially meaningful. Data are graphically

demonstrated in Figure 106. For the most part, molt

sequence closely parallels that of O. I. beali.

PREDATION.—Aside from the ever-present danger

to storm petrels posed by the Western Gull' (Larus

occidentalis) (primarily avoided by the strictly nocturnal habits of the hydrobatids), Burrowing Owls

(Speolyto cunicularia) appeared to be the greatest

threat to these small Procellariiformes. In order to

study predation, numerous remains of owl-eaten

storm petrels were collected on Islote Negro during

the April 1968 survey and again during the June

1968 visit. Although little of quantitative value can

be determined from this study because of the windscattered remains, etc., predation was considerable.

In April 1967 a downy young storm petrel was

found, partially eaten, at the end of a burrow, indicating the possibility that the small owls may enter

occupied storm petrel burrows and attack the

young. At least one pair of owls each were noted on
176

130'V 120 110 100

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

90° 80°

130° 120 110° 100° 90° 80°

FIGURE 107.—POBSP sightings of Oceanodroma homochroa.

Islote Negro and Islote Afuera. During June 1968

the owls were largely feeding upon downy young

Xantus' Murrelets (Endomychura hypoleuca), which

were hatching in great numbers and trying to make

their way to water.

Oceanodroma homochroa (Coues)

ASHY STORM PETREL

PELAGIC DISTRIBUTION.—The POBSP records of

this species are few, with low numbers of scattered

sightings from ca. 7°N to 47°N; all sightings are

along the western North American coast (Figure

107). The most pelagic sightings are of two birds

near 13°N about 480 miles from the coast. The

only concentration we recorded was off the Baja

California coast between 28°N and 29°N during

August 1967.

Uncertainty concerning the pelagic range of this

species results primarily from difficulties in sep-
NUMBER 158 177

arating it in the field from closely similar darkrumped Oceanodroma leucorhoa races such as O. I.

chapmani, O. I. socorroensis and O. I. willetti

(— O. I. beali). It probably occurs in rather low

numbers compared with its closely allied forms.

BREEDING BIOLOGY.—A POBSP survey around San

Miguel Island in the Channel Islands off the California coast 14 and 15 May 1968, found small numbers of birds on both Castle Rock and Prince Islet,

all in empty nest cavities in rock crevices among a

colony of Cassin's Auklets. Flight calls of the storm

petrels were heard shortly after full dark, but it was

impossible to make an estimate of the population

size because of the din of surf and calling auklets.

The few birds examined at this time had bare or

defeathering brood patches.

On another survey of San Miguel from 28 May

to 7 June 1968, birds were still courting; one egg

each was found on Castle Rock and Prince Islet.

The maximum estimate at that time was 100 birds

for the San Miguel population. A bright moon at

the time seemed to retard the arrival of the birds

on the islets and reduced their activity. Perhaps the

Western Gulls take advantage of the moonlight to

prey upon these petrels as the Great Black-backed

Gulls (Larus marinus) and Herring Gulls (L. argentatus) prey upon Leach's Petrels in the Bay of

Fundy (Gross, 1935). Gross notes that on moonlit

nights very little storm petrel activity occurs.

In the Coronados Islands Joseph Jehl of the San

Diego Natural History Museum collected a few

Ashy Storm Petrels in a mist net on Center Island

the night of 17 May 1968, but POBSP recorded none

during a 30 June to 1 July 1968 visit. No evidence

of nesting was found on either visit; apparently

very few individuals utilize the Coronados. Orr

(1944) gives an excellent summary of what little is

known of the breeding biology of this species along

the California coast.

From a series of 20 birds collected at San Miguel

Island, two show considerable amounts of whitish

feathers at the sides of the rumps. This is interesting, not only from the standpoint of the relationship of homochroa to leucorhoa, but from the fact

that selection for dark rumps seem to have affected

all hydrobatid forms along the middle western

North American coast (an area of excessively high

gull predation?).

Oceanodroma castro (Harcourt)

HARCOURT'S (or MADEIRAN) STORM PETREL

PELAGIC DISTRIBUTION.—The pelagic range of

Harcourt's Storm Petrel in the Pacific is rather extensive, as indicated in Figures 108 and 109. The

sightings recorded probably represent only a small

fraction of the actual birds seen, as those shown

represent only sightings considered positive. The

more extensively white rump of Harcourt's as opposed to Leach's could often be used to separate

these two forms at close range, but undoubtedly

the majority of birds of this species were recorded

by POBSP personnel only as "unidentified whiterumped storm petrel." Despite the difficulty of distinguishing Harcourt's from other white-rumped

forms (especially Leach's and Wilson's), specimens

of Harcourt's collected at various points throughout the pelagic range lend credibility to the observations.

In the central Pacific birds were recorded commonly south and southwest of the Hawaiian Islands to 4°S, with one sighting south of 8°S. Birds

were also common to the west and northwest of the

Hawaiian Islands and it is likely that the species

ranges beyond the boundaries shown in the northwest sector as birds were observed practically to the

limits of POBSP cruises in that area. Although it cannot be determined from the collected specimens,

central Pacific records probably represent birds

from the Hawaiian population (dubiously distinctive O. c. cryptoleucura).

Harcourt's distribution in the eastern Pacific is

even more extensive than that recorded in the central Pacific. Sightings were recorded from near

Panama west to 120°W and from 25°N to south of

13°S. While it might be logical to assume that eastern Pacific records are attributable to the Galapagos Islands population, we cannot, in fact, assign

origin to them. The species obviously ranges so

widely at sea that sightings at any point could be

of birds from any one of the Pacific breeding stations. Three specimens taken near the Galapagos

are most probably referable to the breeding race of

that island group (O. c. "bangsi"), but as Austin

(1952) demonstrates, none of the named Pacific subspecies of this form are separable.

BREEDING BIOLOGY.—The available breeding data

for this species are summarized by Palmer (1962).

The POBSP was unable to add further information

of its breeding status in the Hawaiian Islands.
NUMBER 158 179

130 W

• 1 bird

• 5 birds

O Specimens collected

20

130° 120° 110° 100° 90° 80°

FIGURE 109.—I»OBSP sightings and specimens of Oceanodroma castro in the eastern Pacific.

court's Storm Petrel during a day of collecting on

25 June 1966 just off Kauai Island near the Waimea

Canyon area, where I saw a considerable number

of birds and collected one specimen, a female with

ovary enlarging, but not yet in breeding condition.

Birds appeared to be both going to and leaving the

island throughout the day, but we could not approach the shoreline closely enough to determine if

the birds went to land. The population on Kauai,

as judged by the number of specimens and sightings, cannot be large.

MOLT.—The data from the ten specimens collected by POBSP are given in Figure 110. Briefly, our

May and June birds collected in the central Pacific,

as well as March birds collected near the Galapagos,

are in new plumage without molt except for terminal stages in the rectrices of the May birds. October and November central Pacific birds are in intermediate primary and body molt with very worn,

but unmolting, rectrices. Oddly enough, a Galapagos bird collected in late July is in exactly the

same stage of primary molt as two November specimens from the central Pacific.

Oceanodroma tethys (Bonaparte)

GALAPAGOS STORM PETREL

PELAGIC DISTRIBUTION.—The Galapagos Storm
20

130° 120° 110° 100° 90° 80°

FIGURE 109.—I»OBSP sightings and specimens of Oceanodroma castro in the eastern Pacific.

court's Storm Petrel during a day of collecting on

25 June 1966 just off Kauai Island near the Waimea

Canyon area, where I saw a considerable number

of birds and collected one specimen, a female with

ovary enlarging, but not yet in breeding condition.

Birds appeared to be both going to and leaving the

island throughout the day, but we could not approach the shoreline closely enough to determine if

the birds went to land. The population on Kauai,

as judged by the number of specimens and sightings, cannot be large.

MOLT.—The data from the ten specimens collected by POBSP are given in Figure 110. Briefly, our

May and June birds collected in the central Pacific,

as well as March birds collected near the Galapagos,

are in new plumage without molt except for terminal stages in the rectrices of the May birds. October and November central Pacific birds are in intermediate primary and body molt with very worn,

but unmolting, rectrices. Oddly enough, a Galapagos bird collected in late July is in exactly the

same stage of primary molt as two November specimens from the central Pacific.

Oceanodroma tethys (Bonaparte)

GALAPAGOS STORM PETREL

PELAGIC DISTRIBUTION.—The Galapagos Storm
180 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

October - November

N--3

New 1223Growing L .J Old 1H3 Molting on-molting

FIGURE 110.—Seasonal molt stages in Oceanodroma castro. (See Figure 99 for explanation of

symbols.)

Petrel is one of the few white-rumped species in the

Pacific that can be identified with a fair degree of

certainty under most field conditions. The extremely large, prominent, wedge-shaped white

rump, and alternately fluttering and bouncy flight

are good characters for distinguishing most individuals from Oceanodroma lencorhoa, the species regularly recorded with O. tethys over much of the

latter's pelagic range. When I first encountered

tethys at sea, and l>efore I learned some of its more

subtle characters, I had difficulty making on-thespot distinctions between it and equally small, exceptionally white-rumped O. I. socorroensis. Part

of this difficulty arose from the fact that both forms

were in extremely ragged plumage at the time. It

may be noted that specimens of both races of O.

tethys had medium-gray oil (uropygial) glands, as

opposed to the creamy white oil glands of all races

of O. leucorhoa and of O. castro.

Supposedly, the nominate race (O. /. tethys)

breeds in the Galapagos from April through September^). The POBSP pelagic specimens of this race

are confined to August 1967 and March and April

1968. During the latter period concentrations were

especially prominent in a broad band along the

equator from about 3°N to 2°S between longitudes

97°W and 105°W. August specimens were taken at

12°N, 120°W. A June specimen in the San Diego

Natural History Museum was taken at 15°N,

101 °W. Huey (1952) reports a specimen taken by

J. R. Pemberton in March 1938 at Roca Partida in

the Revilla Gigedo Islands south-southwest of Baja
NUMBER 15* 181

130° W 120

1.01 +

Specimens collected

O. tethys tethys

• lbird

• 5 birds

O. tethys kelsctlli ¥•

120 110 100 90

FIGURE 111.—I*>BSP sightings and specimens of Oceanodroma tethys.

80 70

California (ca. 19°N). In this same publication

Huey reports a male of this race in nonbreeding

condition (testes 3x 2 mm) taken from a colony of

Oceanodroma leucorhoa kaedingi on Guadalupe

Island off Baja California in January 1950. The

bird was found in a nest cavity with a downy young

kaedingi. For whatever reason the bird came to the

island, Hubbs (1960) is incorrect in regarding this

as constituting a breeding record for the Galapagos

Storm Petrel at Guadalupe. I have examined this

specimen at San Diego and, except for a short,

heavy bill and slightly small wing for O. t. tethys, it

corresponds well to that form. This locality, at

roughly 29°N, apparently marks the northern

limit for the nominate race.

The second-named form of this species, O. tethys

kelsalli (Lowe), breeds on the Pescadores and San

Gallan Islands off the coast of Peru. Northernmost

POBSP records of this race are of two individuals

collected on 6 August 1967 at 23°03'N, 118°24'W.

Moffitt (1938) reports 12 specimens collected at

22°30'N, 112°39'W on 22 July 1905 and another

specimen taken at 16°45'N, 110°28'W on 22 September 1933. These birds had traversed northward

through most of the recorded pelagic range of the

nominate race. Our pelagic sight records (Figure
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Primary Rectrix

1 March-2 April

N=36

Body Primary Rectrix

11 August

Body

New E22 Growing C H Old I Molting

FIGURE 112.—Seasonal molt stages in Oceanodroma tethys tethys.

(See Figure 99 for explanation of symbols.)

Ill) cannot be qualified to race as the two named

forms are separable only on mensural differences.

The pelagic ranges of the two races show considerable sympatry.

Other POBSP specimens of O. /. kelsalli were collected in the Gulf of Panama during August 1968

and June and August 1969. Large numbers of O.

tethys were observed in the gulf from August

through November 1968 and June through August

1969. Although only a relatively few specimens

were collected, all are definitely referable to O. t.

kelsalli. On this basis, it is reasonable to assume

that most Gulf of Panama wintering O. tethys are

of the race kelsalli. From November on, tethys is

absent from the Panama gulf waters, when it is apparently replaced by the Black Storm Petrel and

the Least Storm Petrel.

MOLT.—Considerable variation in molt is displayed in two series of O. t. tethys collected at sea.

A series of 36 taken between 1 March and 2 April

falls essentially into two categories:

1. Molting: As shown in Figure 112, 44 percent

of the birds in this sample are molting in both primaries and rectrices. There was no exact correlation

in the progress of molt between these two plumage

areas. A few birds still molting the primaries had

completed their rectrix molt and vice versa. Hence,

although only 44 percent of the sample is involved

in each case, the total number of individuals concerned in these combined categories equaled 50

percent of the sample. In practically every case, primary and/or rectrix molt was accompanied by

body molt.

2. Nonmolting: The remainder of the sample
NUMBER 158 183

(50%) not in primary or rectrix molt, was, for the

most part, in old, but relatively unworn plumage,

indicating that molt had occurred within the previous few months. Definition of plumage condition

in rectrices or remiges of birds not in molt is somewhat subjective. When molting, a distinction is

easily made between new and old feathers, primarily because the feathers being replaced are obviously old and show considerable wear and discoloration.

The majority of birds in both molting and nonmolting categories were adults, judging by gonadal

condition. None was in breeding condition, although several may well be considered either to

have begun gonadal enlargement or retrogression.

The nominate race of O. tethys is supposed to have

a complete postbreeding molt from July through

October (Murphy, 1936:730). It appears from our

sample that the duration of the molt cycle is much

more extensive. If tethys has a molt cycle similar

to races of O. leucorhoa, a large number of birds

would be expected to terminate a molt just prior to

the advent of a breeding cycle.

The small series of five birds collected in August

are all in finishing stages of complete molt, or in

very new plumage. A combination of immatures

and adults is represented, judging by gonads. This

series substantiates Murphy's (1936:730) statement

concerning a postbreeding molt from July through

October, but half of the large series taken in March

and April certainly do not correspond to this pattern. Obviously we need to know the ages and times

of breeding cycles of individual birds before it will

be possible to draw conclusions concerning the molt

cycle of the species.

Oceanodroma hornbyi (Gray)

HORNBY'S STORM PETREL

PELAGIC DISTRIBUTION.—The few POBSP records

of sightings and specimens of this southern hemisphere hydrobatid were recorded in August 1967

in the Peru Current southeast of the Galapagos Islands along the South American coast (Figure 113).

Three specimens taken at 3°38'S, 87°01'W were

adult females with medium fat, ovaries between 3

and 5 mm, granular. I have no data for a fourth

specimen taken south of the above area at 9°29'S,

82°05'W. Murphy (1936:741-743) limits the species

to the Peru Current roughly between Valparaiso,

Chile, and the equator.

The breeding grounds of O. hornbyi are still imprecisely known, but Johnson (1965:108) cites four

points of evidence that strongly indicate it nests

inland along the Chilean and Peruvian coasts.

These are summarized as follows: (1) In 1894, Dr.

Darapsky found a fully grown immature specimen

(with patches of down still adhering) in a hole in

the hills of the coast ranges of the port of Taltal,

in the southern Antofagasta Province (specimen in

the National Museum of Santiago). (2) In 1923,

Wetzel found mummified nestlings in holes in the

canyon of the Loa River at the point where it

crosses the nitrate desert inland from Tocopilla.

(3) Another mummified specimen was found in December 1923 in the nitrate fields of Santa Luisa de

Taltal, 30 miles from the coast at an altitude of

5000 feet. (4) The Koepckes took several specimens

at night in the streets of Lima, Peru. Some of these

had abundant down patches on the abdomen.

Oceanodroma melania (Bonaparte)

BLACK STORM PETREL

PELAGIC DISTRIBUTION.—Abundant observations

of this species were made on POBSP cruises along the

western American coast from about 38°N to the

equator. Sightings below the equator (to 7°S) were

few, as were those in the extreme northern sector

and at extreme distances from the coast (Figure

114). There was a pronounced movement into the

Gulf of Panama during November, which presumably indicates a southward movement after the

breeding season. The species was common in the

gulf area until June, during which time the Least

Storm Petrel was also abundant. Most sightings

along the California coast are summer records, but

a few birds were recorded above 34 °N in December. At sea the Black Storm Petrel is a swift flyer.

During collecting activities off the Baja California

coast, the birds appeared to have no problem in

outdistancing our skiff, which was moving at an

estimated 25 knots.

BREEDING BIOLOGY.—Coronados Islands: During

a POBSP survey on 1 and 2 May 1968, Black Storm

Petrels began coming in over the cove on North

Island precisely at full dark. Their appearance was

in exact correlation with the termination of Western Gull movements and one may be certain that
184 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100 W 80°

20'

N

ltf

10'

S

20'

70° .

20

• lbird

O specimen collected

100 90

FIGURE 113.—POBSP sightings and specimens of Oceanodroma hornbyi.

the timing of these activities is not coincidental.

Storm petrel aerial movements and vocalizations

were most intense during the first few hours after

dark and had essentially stopped by midnight. An

increase in flying birds was noted near the beach at

about 0100; this possibly represented birds leaving

the island. Two characteristic calls were noted: an

aerial call described by most field workers as "puck,

puckaroo," and a variable "twitter" uttered only

from nest cavities. This latter call may continue for

many minutes. The nest sites on North Island were

invariably in deep recesses under large boulders
NUMBER 158 185

130 W

• 1 bird

• 10 birds

• 20 birds

f Breeding localiti

110" 100° 90°

FICURE 114.—POBSP sightings of Oceanodroma melania.

that prevented investigating the nests in most cases.

A few such large "fortresses" harbored more than

one pair. The four to six nests that could be examined at this time contained both members of the

pair, but none had eggs or young. Individuals

taken in a mist net had bare or defeathering brood

patches. During a visit on 30 June 1968, a few birds

were noted on Center Island and a chick, estimated

to be only a few days old, was found on North Island. In the San Diego Natural History Museum a

series of downy nestlings, ranging in size from small

to large, are recorded from the Coronados from 13

August to 5 September.

San Benitos Islands: On a POBSP survey from 26

to 29 April 1968, these petrels were noted coming

in over the islands at night, with a peak of aerial

movements and vocalizations during the first three

hours of darkness. Little activity was noted for the

remainder of the night. No evidence of nesting was

recorded at that time. During a survey from 25 to

27 June 1968, a sample of nest sites examined

showed that birds were on fresh- to medium-incubated eggs, with a few individuals still calling from

as yet empty nest cavities. The preferred nesting

sites of this species seemed to be under large boulders on talus slopes. In some cases Least Storm
186 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Petrels were found nesting in the same burrows

with the Blacks. The Black Storm Petrels were

found on all three islands in the San Benitos group,

with greatest densities on West Island. A population estimate for the island group at that time was

10,000+ birds. A prime mortality factor was the

abundant cholla cacti throughout the nesting area.

Birds flying about in the dark were often impaled

upon the spines; on one slope several Black Storm

Petrels were found dead in this manner (see comparable data on Oceanodroma leucorhoa chapmani).

120 W

' 1 bird

• 5 birds

• 10 birds

O specimen collected

20

120

20

110 100' 70°

FIGURE 115.—POBSP sightings and specimens of Oceanodroma markhami.
NUMBER 158 187

Oceanodroma markhami (Salvin)

MARKHAM'S STORM PETREL

PELAGIC DISTRIBUTION.—Most POBSP pelagic

sightings of this species are in August and September along a broad equatorial front from the South

American coast west through the Galapagos area to

105°W (Figure 115). A group of more northerly

sightings off the coast of Baja California may well

represent erroneous identifications attributable to

the very similar Oceanodroma melania. I doubt if

the two species can be distinguished in the field,

and melania would certainly be the more expected

form in these northern waters. It may be noted,

however, that Murphy (1936:740) cites Loomis

(1918:174) as having recorded markhami at 13°

28'N, 108°52'W, and just south of Cocos Island,

5°33'N, 87°00'W. Two specimens were collected

by POBSP along the South American coast. Both individuals taken on 6 August 1967 at 00°18'N, 81°

51'W were females with small gonads (and oviducts

never used), light fat and heavy contour molt.

The breeding grounds of this species are still unknown. Murphy (1936:739) records several females

with fully formed eggs in the oviducts taken by

Rollo Beck in early June, 75 to 80 kilometers off

the Peruvian coast. He further states that the only

islands off the Peruvian coast not thoroughly investigated were the Hormigas de Afuera, which

because of their exceedingly low elevation seemed

a doubtful nesting site. He suggests the possibility

of their nesting inland in the Andes. Johnson

(1965:107) notes that Carlos Reed collected a specimen on 1 December off Antofagasta, Chile (23°S)

that still had traces of down on the head and abdomen. He also records an immature specimen with

abundant down on the breast and abdomen taken

between Pica and Matilla, some 30 miles inland

from the port of Iquique, Chile.

Oceanodroma tristrami Salvin

SOOTY STORM PETREL

PELAGIC DISTRIBUTION.—The POBSP pelagic sightings of this species are from various positions around

the Hawaiian Islands, with concentrations near the

Hawaiian Leewards (breeding sites), as would be

expected (Figure 116). A disjunct, high-density concentration was also recorded between 44°N and

45°N near 173°W. The latter records may pertain

to tristrami populations from the Bonin or Izu

islands, or possibly to Oceanodroma matsudairae

from the Bonin Islands. It is extremely doubtful if

tristrami could be differentiated from O. matsudairae in the field. No specimens are available to

clarify which of the two species were seen here, but

even if specimens were available, distinctions could

not be made between the Hawaiian and Bonin Island populations of O. tristrami.

BREEDING BIOLOGY.—Sooty Storm Petrels have a

disjunct breeding distribution, with populations at

Torishima in the southern Izu Islands (Austin,

1952), the Bonin Islands, and the Hawaiian Leewards. The specific localities in the Leewards are

Laysan, Pearl and Hermes Reef, and Midway. Richardson (1957:19) mentions the possibility of their

breeding on Necker but gives no details. Bryan and

Green way (1944:96) record the species on Nihoa.

Clapp and Woodward (1968:10) report recent

POBSP records on Kure Atoll and French Frigate

Shoals. The latter cite the collection of three specimens with definitely enlarged gonads on Kure (one

each on 1 January 1964, 1 March 1965, and 12 December 1965). The January 1964 bird was one of

two observed digging a burrow. Two other birds

were observed digging a burrow on 2 April 1964,

and one examined in the field between 30 December 1966 and 5 January 1967 had a completely bare

brood patch. Others were seen on Kure between

November and January during the years 1963 to

1967. Three specimens collected 1 to 3 January

1967 have greatly enlarged gonads. On 14 March

1967, one very small downy chick and another

about three-quarters grown were found in shallow

burrows under the grass on Whale-Skate Island,

French Frigate Shoals. Amerson noted a fledgling

here in early June 1967. I believe it very likely that

the species will eventually be found nesting on

Lisianski Island, which has an extensive habitat

comparable to that which supports a sizable population on Laysan. From this latter island POBSP collected three specimens on 22 October 1966 with

considerably enlarged gonads. Willett (1919) reports egg-laying on Laysan from 1 to 15 January.

Inadequate POBSP winter surveys in the Leewards,

plus the very secretive nature of this storm petrel

on the breeding grounds, make it difficult to obtain

a clear picture of the breeding cycle. From available

data it appears that the species is to be found on
188

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

170 E 180 170 W 160 150

40"

N

30"

20

10

• 1 bird

• 5 birds

•10 birds

^f breeding localities

40

30

20

10"

170' 180* 170* 160' 150

FIGURE 116.—POBSP sightings of Oceanodroma tristrami.
NUMBER 158 189

120 W

120 110 100 90

FIGURE 117.—POBSP sightings of Halocyptena microsoma.

70

the breeding grounds during an extended period

from at least October to May. Apparently December and January are peak egg-laying months; both

young and adults are gone from the islands by midMay.

Halocyptena microsoma Coues

LEAST STORM PETREL

PELAGIC DISTRIBUTION.—At sea this species is

usually distinguishable from other dark-rumped

forms by its tiny size. Although it is normally a

more coastal form, it was sighted by the POBSP as far

as 600 miles off the Mexican mainland. Large numbers are found in the Gulf of Panama during the

winter months (December to April). There appears

to be replacement between this species and Oceanodroma tethys in the Gulf of Panama. Oceanodroma

tethys is very abundant from June to November,

but completely disappears in the latter month

when H. microsoma begins showing up in numbers.

A small number of Black Storm Petrels are, however, present during the time the Least is abundant.

Other than the concentrations in the Gulf of Panama, the majority of POBSP sightings of the Least

Storm Petrel was along the coast of Baja California

and the Mexican mainland (Figure 117).

BREEDING BIOLOGY.—The Least Storm Petrel

breeds on the San Benitos Islands and on various

other islands in the Gulf of California. During a

POBSP survey of the San Benitos on 28 April 1968,

the only Least noted was one that came aboard

ship offshore. During the 25 to 27 June 1968 survey

here, Leasts were abundant on all three islands of

the group. Nesting was primarily restricted to rock

outcrops and talus slopes, and nests were invariably

in rock crevices. Occasionally more than one pair

were found in suitable cavities and some birds were

nesting in the same cavities with the much larger

Black Storm Petrels. A few eggs of the Least were

found, but most of the birds in June were still in

early stages of nest site selection and courting. An
190

SMITHSONIAN CONTRIBUTIONS 1O ZOOLOGY

estimate for Halocyptena during the June survey

was ca. 15,000 birds for the island group. As mentioned in the sections on O. melania and O. I. chapman i, Halocyptena were adversely affected by the

abundant cholla cacti on the islands and several

birds were found impaled on the spines.

On islands in the Gulf of California, the Least

Storm Petrel is frequently mentioned as nesting in

association with the fishing bat (Pizonyx vivesi).

Maya (1969), who studied this bat in the Gulf, felt

that a lizard (Cnemidophorus sp.) preyed upon the

young storm petrels and that the lizards were less

prone to inhabit cavities where the bats lived. On

Isla Partida (in the northern part of the Gulf of

California) R. D. Ohmart (pers. comm.) saw no

predation by the lizards on very small storm petrel

chicks left unattended by their parents during the

daytime. Once after removing an adult storm petrel

from its nest, he saw a large scorpion carry away

the egg. Ohmart did not feel that the presence of

the bat offered any particular advantage to the petrel. It appeared to him that the Least and Black

Storm Petrels and the fishing bat clumped to avoid

excessive heat and gulls, and possibly to gain in

relative humidity. Both eggs and small downy

chicks of the Least Storm Petrel were found on Isla

Partida from 12 to 21 June 1968. Nests were beneath rocks on the ground or in cavities among

rock piles.

Oceanites oceanicus (Kuhl)

WILSON'S STORM PETREL

PELAGIC DISTRIBUTION.—The POBSP pelagic records indicate extremely widespread distribution of

this species in the Pacific, with two decided centers

of abundance (Figures 118 and 119). The equatorial

central Pacific records are practically all confined

to October and November; all are of adults with

somewhat enlarged gonads and very heavy fat, and

in all probability represent birds returning to the

Antarctic breeding grounds. An April specimen

from this area is probably a straggler from an apparent postbreeding migration that moves north

through the Marshall Islands in the spring (Huber,

1971). Our surveys give no clue to northward extent

of this movement, nor to the distribution or activities of the birds between April and October.

Large numbers are recorded in the Peru Current

along the northwestern coast of South America during August. A fair number of stragglers are recorded throughout the eastern Pacific to at least

31°N. In view of this, the various coastal California

records in August (1910, 1935, and 1959) summarized by Nisbet and McCaskie (1960:141) seem not

too unusual considering the species' wide dispersal.

It should be emphasized that the POBSP sight records shown are only those of fairly positive nature;

undoubtedly many more birds were observed which

were recorded only as "unidentified white-rumped

storm petrel."

Oceanites gracilis (Elliot)

GRACEFUL STORM PETREL

PELAGIC DISTRIBUTION.—Most POBSP sightings of

this species were during September near the Galapagos Islands. Other cruises were run about the

islands during other times of the year, especially

March and April, and relatively few birds were

seen. Most of our September sightings were within

a hundred miles of the Galapagos (Figure 120).

Loomis (1918:181) states that "they were never observed far from land, the greatest distance being

about 50 nautical miles." Murphy (1936) has no

record of its breeding, but it has been taken just

offshore of several of the Galapagos Islands and unquestionably breeds there.

The race O. g. galapagoensis obviously restricts

itself to the cold waters of the Peru Current just to

the west of the Galapagos. The nominate race O. g.

gracilis appears to be restricted to the Peru Current

between Valparaiso, Chile, and Santa Elena, Ecuador (Murphy, 1936).

Fregetta grallaria (Vieillot)

WHITE-BELLIED STORM PETREL

PELAGIC DISTRIBUTION.—The primary distribution of this species in the area covered by POBSP

was along 85°W from 06°S to 15°S. Two scattered

sightings were recorded at 09°45'S, 117°43'W, and

02°17'N, 104°W (Figure 121).

Murphy (1936:762) recorded that R. Beck took a

specimen of Fregetta grallaria titan at 04°20'S,
NUMBER 158 191

50°

N

170 E 170°W 160 ISO'o

50

40

20

10

• 1 bird

• 5 birds

O 1 specimen collected

40°

20

10

10

17<r 180° 170° 160° 150°

FIGURE 118.—POBSP sightings and specimens of Oceanites oceanicus in the central Pacific.

(? = doubtful information.)
192

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

• 1 bird

• 5 birds

• 20 birds

O Specimen collected

FIGURE 119.—POBSP sightings of Oceanites oceanictu in the eastern Pacific.

93°30/W on 11 June 1906, and further stated that

no less than ten other examples were seen in the

same vicinity during the next few days. The race

F. g. titan is recorded as breeding at Rapa Island

in southern Polynesia. Whether our sightings pertain to the race F. g. titan, or to the nominate F. g.

grallaria which breeds at Mas Atierra and Santa

Clara of the Juan Fernandez Islands is unknown,

since no specimens were collected.
NUMBER 158 193

70°

20

Bird

Birds

10

90° 80°

FIGURE 120.—POBSP sightings of Oceanites gracilis.

70"

Nesofregetta albigularis (Finsch)

WHITE-THROATED STORM PETREL

PELAGIC DISTRIBUTION.—This species was widely

distributed in the Pacific along equatorial latitudes.

The vast majority of sightings in both the central

and eastern Pacific is confined to areas between

10°N and 10°S (Figures 122 and 123). Concentrations about the Phoenix and Line islands in the

central Pacific are easily referable to the breeding

populations of those areas. The equally great concentrations recorded in the eastern Pacific west of

the Galapagos Islands are of unknown origin, but

most probably from the breeding stations in the

Marquesas Islands and Christmas Island. It should

be pointed out that our data represent a considerable range extension to the known pelagic range.

TAXONOMY.—To my knowledge this species does

not vary throughout its considerable range, and no

subspecies have been proposed. Except for Oceanodroma tristrami, N. albigularis is approximately the

largest storm petrel in the Pacific area (Appendix

Table A). Most POBSP specimens are from the Phoenix and Line islands (Christmas Island) populations.

In the Phoenix group, the majority of birds are

of the color morph usually described for the species,

i.e., dark upperparts and chest band, with white

rump, throat and belly. On both Phoenix and McKean islands, however, every conceivable color vari-
194

120 W

10°

N

110° 100

— I —

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

90° 80° 70° „

0°

20

liobclo I..

, Galopogos Itlandi

20°

70° 120 100 90 80°

FIGURE 121.—FOBSP sightings of Fregetta grallaria.

ation between the normal form and totally dark individuals may be found (Figure 124). The "Samoan

Storm Petrel" ("Fregetta moestissima" Salvin),

known from the unique type taken offshore the

Samoan Islands, is considered by Murphy and Snyder (1952) to be nothing more than an entirely

melanistic example of Nesofregetta albigularis. The

appreciably larger dimensions (especially wing)

than those of any specimens from the Phoenix,

Line, Marquesas or New Hebrides islands indicates

it may be from a distinct population, possibly

breeding somewhere in the Samoan Islands. Bourne

(1957) indicates that the unique, all dark specimen

of Fregetta fuliginosa (Gmelin) from Tahiti (specimen subsequently lost) was probably closely allied

to the Samoan form. On Christmas Island about

half the population of Nesofregetta albigularis

shows some dark flecking on the white underparts,

but completely melanistic birds have not been seen.

BREEDING BIOLOGY.—Published data on the

breeding biology of this species is virtually nonexistent and thus I have entered POBSP data in considerable detail in comparison to other species

whose breeding biologies are well known. The

breeding range of Nesofregetta albigularis extends

from the Line Islands (Christmas Island) and Phoenix Islands (Phoenix and McKean islands) in the

central Pacific south to and including the Samoan

Islands (?), Marquesas Islands, Fiji Islands, and the

New Hebrides Islands. The POBSP surveys covered

only the more northern parts of its range, i.e., the

Line and Phoenix islands. Since our surveys were

fairly complete for the Phoenix group, it is unlikely that N. albigularis breeds on islands other

than McKean and Phoenix, although we have several sightings of birds flying over Enderbury Island

(25 to 27 September, and 9 to 10 October 1966). A

specimen was collected on Howland Island on 24

October 1938, but we have no recent sightings.

In the Line Islands, however, islands such as

Maiden and Starbuck are quite large and our coverage was insufficient to rule out the possiblity of

birds breeding in those areas. On Maiden Island

one bird was noted at night on 31 March 1967.

Several islets in the lagoon were not thoroughly

investigated and might be utilized by this species
NUMBER 158 195

180° 170° 160°

FIGURE 122.—POBSP sightings of Nesofregetta albigularis in the central Pacific.

for nesting. Other possible breeding areas are the

Gilbert, Society, Tuamotu and Marshall islands

(King, 1967:42).

The choice of breeding sites on the three central

Pacific islands investigated was much the same.

Areas supporting bunch grass (Lepturus sp.), large

clumps of weeds (Boerhaavia sp.) or Sesuvium, in

combination with an abundance of loose rocks,

were utilized in practically all cases in the Phoenix

Islands. Extensive areas of rocky coral slabs without vegetation, as well as areas of continuous short

grass or small annuals, were avoided. Old fallen

rock walls which were constructed by the early colonists on the Phoenix Islands were often used as
196

130"W 120" 110 100

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

90° 80° 70°.

10

20'

120° 110° 100° 90s 80°

FIGURE 123.—POBSP sightings of Nesofregetta albigularis in the eastern Pacific.

10

-

2

.

0

70°

130°

FICL'RE 124.—Color variation in Nesofregetta albigularis from the Phoenix Islands.
NUMBER 158 197

nest sites, although standing walls devoid of vegetation were much more prone to be utilized by Bulwer's Petrel (Bulweria bulwerii). On Christmas Island most nests on the small islets were under

clumps of overhanging grass (Lepturus), in pockets

in coral rock shelves also usually sheltered by grass,

or in depressions under Sesuvium. Regardless of

nest site, the actual nests were similar in all cases.

The few pieces of nest material (grass, weed stems,

feathers, etc.) invariably present were most likely in

the nest cavities to begin with; such material is

probably manipulated to some extent, but to my

knowledge no material is ever carried into the nests

by the birds. Incubating birds are usually hidden

from view within nest cavities, but an occasional

individual will nest in rocks in such a manner that

it can be seen. Schreiber (POBSP) noted that tails of

incubating birds were often visible in the shallow

nest cavities on the islets in Manulu Lagoon,

Christmas Island. Under large, extensive grass or

weed clumps, the birds usually retreat to the most

concealing portion. The nest cavities may be

slightly enlarged under clumps of vegetation, but I

have never noted any extensive digging performed

by this species. Storm petrels often utilize nest cavities dug out by the abundant Audubon's Shearwater

(Puffinus Iherminieri) on McKean and Phoenix islands.

On Christmas Island the nesting areas are primarily limited to five tiny islets in Manulu Lagoon.

These are separated by expanses of water from the

main island. A few birds nest on the islets of^Motu

Tabu, Motu Upua, and on at least one islet in Isles

Lagoon. Utilization of these retreats is probably a

direct result of feral cat predation on the main island:

From banding and recapture data Schreiber

(POBSP) estimated the total population using Christmas Island in 1967 at 350 to 450 birds, although

this estimate is probably low. Table 29 summarizes

the stage of nesting and nest contents recorded in

Manulu Lagoon by POBSP and others.

From the above data it can be inferred that the

peak egg period on Christmas Island is from September through November, but obviously some portion of the population is nesting at all times of

year. This seasonal spread of nesting apparently

allows a greater number of birds to utilize the

available nesting area than would be possible if

TABLE 29.—Surveys of nesting Nesofregetta albigularis in the Manulu Lagoon area, Christmas Island,

Line Islands

Date

Jan 59

Feb 21

Mar 65

Apr 59

Jun 65

Jul 67

early Aug 67

late Aug 67

Oct 65

Nov 64

early Nov 67

late Nov 67

late Dec 67

Xest contents Source

20 occupied nests (contents?) Gallagher (1960:494)

eggs and young present Murphy (1924:12)

30 nests, eggs and chicks POBSP

1 small, 2 nearly fledged Gallagher (1960:494)

chicks

few nesting POBSP

3 eggs, 1 small downy chick

14 eggs, 3 chicks

21 eggs, 5 chicks

50 (eggs and small chicks)

26 eggs, 5 chicks

54 eggs (including 11

abandoned), 9 chicks

37eggs (including 6 newly

abandoned), 9 chicks

(including 5 dead)

6 eggs, 25 chicks

nesting were limited to a specific time of the year

for all individuals. One adult, with an egg, banded

on 25 August 1967, on Islet # 2 in Manulu Lagoon

was found incubating an egg on Islet # 1 on 28

November 1967. This meager evidence suggests that

the species will renest within the same year, and,

furthermore, a specific nest site is apparently not

adhered to. Another adult in an empty nest cavity

on 29 August 1967 was incubating an egg there on

4 November 1967; yet another incubating an egg

on 17 August 1967 was still incubating on 4 November 1967. The egg in the latter case was probably

infertile, but these examples give an idea of the

extensive periods that the birds spend on the breeding islands.

Our data for the Phoenix Islands are less complete because of the extremely short surveys made,

but the available evidence shows that on McKean

and Phoenix, as on Christmas Island, some portion

of the population is nesting during every month of

the year. Tables 30 and 31 present POBSP data for

McKean and Phoenix islands.

Variation and inconsistencies in the data are due

partly to different observers and to the extremely

inadequate surveys in most cases. It is nonetheless

evident that considerable variation is to be found

on the same island for a given month during different years (Table 30, February 1964 and 1965). Despite these differences, considering the data as a
198

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 30.—POBSP surveys of Nesofregetta albigularis on McKean Island, Phoenix Islands

TABLE 31.—POBSP surveys of Nesofregetta albigularis on Phoenix Island, Phoenix Islands

Date

Number Population

banded estimate Nest contents

6-7 Feb 65 94

16-20 Feb 64 9

17-19 Apr 66

30Apr-lMay66 -

13-15 Jul 68

18-20 Jul 64

23-25 Jul 66

14-30 Oct 68

(thorough

survey)

18-22 Oct 64

24-28 Oct 63

56

13

500

25-30

500 +

1000

1000 adults,

200 eggs,

200 chicks

no data

750

30 adults

100

100 + .7

collected

large number beginning

to nest

no eggs or young found

no eggs

1 egg

sample of 23 nests: 12

eggs, 11 chicks ranging from ca. 4 days

old to fully feathered

no data

10 eggs, few small and

large downy nestlings

1 egg, 3 large chicks

no data

1 egg found

whole, there appears to be a breeding peak on McKean from April through at least July or August,

with a definite low in October and probably later.

For Phoenix Island we do not have data from

monthly surveys in successive years, but certainly

the high nesting populations recorded from October

through December do not correspond to the breeding situation on McKean. This lack of conformity

to a set seasonal or annual cycle has been noted for

most species on the equatorial islands. Our surveys

indicate that the populations on one island appear

to operate independently from those on other islands, regardless of the apparent ecological similarities of the islands or their geographic proximity.

On McKean Island there appears to be a definite

separation in the timing of nesting of Nesofregetta

albigularis and Bulweria bulwerii. This was quite

apparent during two fairly extensive surveys in July

and October 1968. During July, N. albigularis was

definitely undergoing a peak in nesting with an

estimated 1000 adults on the island. Bulwer's Petrel

at that time was for all practical purposes absent

from the island (one adult calling from an empty

nest cavity). During the extensive October survey

only about 30 adult White-throated Storm Petrels

were present on the island with nine nests (3 with

young, 1 with egg, and 5 occupied, but as yet without eggs). Bulwer's Petrel at this time was approaching a peak nesting situation with a very conservaDate

Number Population

banded estimate Nest contents

26-28 Jan 67 - 150 1 fresh egg found

23-26 Feb 64 - 100 no evidence of nesting

14-16 Apr 66 - 300+ nesting

26-30 May 65 35 500 nesting, young present

18-20 Jul 64 56 200-300 eggs and nestlings present

29-30 Sep 65 - 2 no evidence

10-11 Oct 66 - 400(15% 20 eggs, 5 small downy

nesting) young, 5 large downy

young

3-7Nov64 15 100 no data

2-5 Dec 66 - 300(40% 50 eggs, 10 small chicks

nesting)

tive estimate of 1000 birds on the island. The majority of these were calling from empty nest cavities

or from nests with fresh eggs; an estimated five percent had small downy young. Both species tend to

utilize the same nest sites to a high degree, and this

complementary seasonal nesting arrangement apparently affords both populations minimum competitive activity during their respective breeding

periods. Food availability in the nearby ocean may

also be a factor in creating alternating nesting seasons for these similar species.

On the breeding islands, White-throated Storm

Petrels are usually absent during most of the daylight hours (except for those attending to incubation or brooding duties). On several occasions, however, I have seen adults come to nests in full daylight to feed young. This type of behavior is never

performed by any of the small hydrobatids in the

eastern Pacific, since any individual showing itself

during the day would be immediately set upon and

devoured by Western Gulls. The rapidity with

which the gulls attack storm petrels appears to be

the sole reason why storm petrels never appear

overland in daylight hours. In the central Pacific,

however, Nesofregetta appears to be without predators. The frigatebirds (Fregata ariel and F. minor)

were never noted harassing storm petrels, but

seemed to restrict their parasitism to larger birds

such as boobies, shearwaters, and terns.

Adult storm petrels normally come in over the

breeding islands from the ocean from about onehalf to three-quarters of an hour before dusk. This

seems to be the period of greatest activity, during
NUMBER 158 199

FIGURE 125.—Young of Nesofregetta albigularis on McKean Island.

(Photo by C. Douglas Hackman.)

which many individuals may be noted flying back

and forth over potential or actual nest sites. Birds

with active nests seem to circle repeatedly over the

general area of the nest site for some time before

landing, as do individuals obviously searching for

nest sites. When the birds land, they usually do so

ungracefully, falling softly and then awkwardly

crawling over the terrain toward the nest site or

into the nest cavity.

As with other hydrobatids and procellariiforms

in general, Nesofregetta lays only a single egg. Occasionally a bird is found incubating two eggs, but

one is invariably an infertile or abandoned egg

from an earlier nesting. Relative to other storm

petrels, the eggs are large for the size of the bird.

A series of 20 eggs from- Phoenix, McKean, and

Christmas islands show the following measurements: length (mean with standard error) 37.95 it

0.41 mm (SD = 1.85); breadth 27.45 ± 0.18 mm

(SD = 0.82). The eggs have a creamy-white background color, with reddish and lavender dots which

usually form a prominent wreath about the large

end, but are scattered less finely over the entire surface.

The few observations available on marked nests

show that both birds are present in the nest cavity

for some time (days?) before the egg is laid. Copulation probably takes place at the nest site. During

these times and at least during early incubation,

adults utter a soft guttural "grrrrr-grrrrr-grrrrr"

call from the nest cavity. Both sexes incubate, but

the rate of changeover, as well as the length of the

incubation period, is unknown. After the chicks are

a few days old the parents only come to the nest to

feed them. The young hatch blind, but are profusely covered with medium-gray down which is

quite short on the underparts and long on the

dorsum. A chick estimated to be five days old had

down to 20 mm long on the back. I doubt if the

young can use vision in the nest until they are in

the large, fully-feathered stage, since the entire orbital region is completely covered by shaggy down.

When the chicks are approximately two-thirds

grown, they have a definite bi-colored aspect. The

dark and light colors correspond roughly to the

black and white areas of the adults. This bicolored

effect is brought about by the growth of new

feathers beneath the down. As the feather coat progresses, more and more down is shed until only

patches remain about the head, dorsum and flanks

(Figure 125). It is not known how soon the young

leave the island after attaining their juvenal plum-
200

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

age, but apparently it is rather soon, as birds with

traces of down still clinging to the feathers were

noted attempting to fly at night; they were at least

many yards away from any possible nest site (see

comparative data on Oceanodroma leucorhoa socorroensis young).

The White-throated Storm Petrel exhibits a peculiar flight at sea which has not been noted in any

other species of hydrobatid. On many occasions

these birds were seen kicking off waves with considerable force, using their extremely long legs and

spatulate feet. The moment their feet hit the water

surface, the birds instantly change direction and

sharply increase their speed, attesting to the force

applied to the water's surface. The usual procedure

was for the individual to "kick off" a wave, glide

for approximately 20 to 30 seconds and again "kick

off." I have on occasion noted a bird parallel a ship

for a mile or more in this manner. Both Gallagher

(1960) and Schreiber and Ashmole (1970) have

noted birds performing this behavior in the quiet

lagoon on Christmas Island. Wilson's Storm Petrels

often dabble their feet in the water, but this appears to be more of a balancing maneuver than an

actual thrust motion as in Nesofregetta. This mode

of travel might be a means of expending less energy

in equatorial regions where wind is often at a minimum. At any rate, the extremely long tarsi and

spatulate feet of Nesofregetta make possible its

unique locomotory behavior.

Discussion

The hydrobatids form a rather homogeneous

group widely distributed over the Pacific regions.

In many cases their breeding distribution and pelagic movements appear to be random, but undoubtedly reflect patterns that have been dictated

by seasonal abundance and distribution of food

items, interspecific competition, and the need to

occupy the limited breeding areas during favorable

periods. These patterns have undoubtedly undergone considerable fluctuation over time; the present view of the family shows a few exceedingly

abundant forms and many uncommon to rare species. In the Pacific region, individuals of the combined subspecies of Oceanodroma leucorhoa by far

outnumber all other species combined.

The northern breeding forms of O. leucorhoa

show south-north migration patterns and practically

inundate the central and eastern equatorial Pacific

during the nonbreeding season (September-March).

Wilson's Storm Petrel, a strictly southern hemisphere breeder, shows the inverse north-south movements in the western Pacific and along the South

American coast during migration and nonbreeding

season from the Antarctic. Another southern hemisphere breeder (White-faced Storm Petrel) demonstrates an east-west pattern, moving east from its

Australian breeding grounds to the South American coast, thence north along the Peru Current and

west through the Galapagos area with a subsequent

return to the Australian region. Possibly Wilson's

performs more of a circular route in its north-south

movements. A number of forms such as Oceanodroma leucorhoa chapmani, O. I. socorroensis, and

O. homochroa apparently do not move any great

distance from the breeding islands during the nonbreeding season. For many Pacific hydrobatids the

nonbreeding distribution is imprecisely known; for

others the stated breeding grounds are merely conjecture.

At sea most storm petrels are either solitary or

join with members of their own species. In certain

cases two or more species will congregate, often in

response to a temporarily plentiful food supply.

They normally do not mix with other seabird species, even with their nearest relatives, the procellariids. I believe the presence of storm petrels in

mixed feeding flocks of procellariids, terns, boobies,

etc., is usually a random occurrence. On many occasions when I have observed storm petrels in the vicinity of mixed feeding flocks, the hydrobatids appeared to lack the intense feeding interest of the

other species and usually moved out of the immediate area of intense feeding. It should be stressed

that in most cases POBSP observers did not distinguish, in a recorded species association, those members that were actually feeding or traveling together. If members of two or more species were

together at the time of initial sighting, they were

usually recorded as such. The imprecision of these

observations was the result, usually, of the impossibility of detailed notations of individuals in large

mixed feeding or traveling flocks where often hundreds or even thousands of birds were concerned.

In such cases a gross account of numbers was about

the best that could be acquired. Thus the presence

of one or more hydrobatids in the immediate vicinity of a flock would be recorded as positive, al-
NUMBER 158 201

TABLE 32.—Intraspecific sociability (number of

individuals/number of sightings) in species of

Pacific hydrobatids

Species

Oceanodroma castro

O. leucorhoa ... .

O. furcata

O. markhami or

O. tristrami

O. melania

O. homochroa

O hoTnbyi

O. tethys

Halocyptenu microsoma. .

Ocsanites oceanicus

O. gracilis

Pelagodroma marina

Fregetta grallaria

Nesofregetta albigularis . .

Total

Individuals

269

14,355

936

167

465

36

12

1,723

63

443

22

79

10

111

27,140

Sightings

203

9,071

235

121

214

10

7

443

48

66

6

67

8

97

12,574

Ratio of

sociability

1.3

1.6

4.0

1.4

2.2

3.6

1.7

3.9

1.3

6.7

3.7

1.2

1.3

1.1

2.2

though, as I have often stated from personal observations, this is usually not the case.

The amount of intraspecific sociability can be

calculated in a gross manner quite easily from our

data. From Table 32 it is immediately apparent

that individuals of some species are far more prone

to associate intraspecifically than others. Forktailed and Wilson's Storm Petrels commonly associate with other members of their respective species.

On the wintering grounds Leach's Storm Petrels

disperse singly or in very low densities unless a local food source happens to bring large numbers together temporarily. During migration they commonly group and are noted resting on the water in

large rafts. Even with our sightings of migratory

and feeding flocks included, the low sociability ratio of 1.6 for nearly 10,000 sightings (involving over

14,000 individuals) demonstrates their usual solitary nature. Other species, such as the Whitethroated Storm Petrel, show this solitary nature to

a greater degree and are almost invariably noted

singly. For most of the less abundant species, although the available evidence suggests solitary occurrence, we do not have enough observations to

demonstrate their overall social behavior at sea.

The solitary nature of most hydrobatid species

away from the breeding grounds is perhaps necessary because of the foraging behavior (flight low

over the water with a limited area view) to distribute themselves as widely as possible over their

range to take utmost advantage of the widely distributed small organisms which make up their diet.

Members of a species, or of several species, will

gather readily at an unusual, abundant food source

such as an oil slick. At such gatherings I have never

noted either inter- or intraspecific hostile behavior

between individuals, behavior that certainly some

(if not all) species are capable of demonstrating as

witnessed by intraspecific battles over nest sites on

the breeding grounds (Leach's, Least, Black, and

White-throated Storm Petrels).

To my knowledge all members of the Hydrobatidae are strictly surface feeders, that is, they do

not submerge the body beneath the surface of the

water to obtain food. All Pacific species were observed to glean the surface of the water for floating

objects, often with wings held aloft for balance. The

foot dabbling behavior with wings held aloft for

balance in the Wilson's Storm Petrel is well known

and documented. Leach's, Harcourt's, and most especially Least Storm Petrels will hold the wings

aloft in a V formation when feeding over an oil

slick or other concentrated food source. In this respect they appear as so many butterflies on a wet

sand bar. Least Storm Petrels were never noted

dabbling their feet the way Wilson's do. They

usually feed while resting on the water with wings

up until wanting to move. Then with a few quick

wingbeats the bird moves to a new position, usually still holding the wings aloft.

The preceding species accounts provide a basis

for understanding the distribution and abundance

of Pacific hydrobatids and indicate the vast amount

of data yet to be gathered concerning these forms.

While it is unlikely that a program devoted to

pelagic ornithology in the Pacific of the magnitude

of the POBSP will occur again in the near future,

important contributions can be made to existing

knowledge by participation in cruises devoted to

any type of pelagic investigation. The great amount

of information on hydrobatids gathered during the

EASTROPAC cruises is a good example of this.

While it is understandable that we know little or

nothing about the breeding biology of many of the

southern hemispere hydrobatids, it is less explicable

why information of this sort is lacking for most of

the species and subspecies inhabiting the coastal

islands of the western United States and Mexico.
202 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

There is a decided need in these areas for long

range studies with banded birds similar to the investigation of the nominate race of Leach's Storm

Petrel on Kent Island, New Brunswick, Canada,

which was begun by Gross (1935) and continued by

Huntington (1963) and his co-workers.

A fascinating problem awaiting study is the elucidation of the relationships and interactions of

winter and summer breeding populations of Leach's

Storm Petrel on Guadalupe Island. A second problem is to account for the clumping of completely

dark hydrobatids along the California and Baja

California coasts. In the Hydrobatidae, where

white patterning is widespread, the lack of this

color in so many forms (four species and three

subspecies) common to this area can hardly be coincidental. The factor of predation by the various

gull species (especially the Western Gull) is probably only part of the reason. The dark rump color

predominates in all forms of hydrobatids along the

coast of Japan also, possibly for the same reasons.
Appendix

Measurements of POBSP-collected specimens of Pacific hydrobatids

(number of specimens in parentheses, linear characters in millimeters, weights in grams)

TABLE A.—Various Pacific hydrobatids

Characters

and

measurements

WlNC

Range

Mean w/SE

SD

TAIL

Range

Mean w/SE

SD

CULMF.N

Range

Mean w/SE

SD

TARSUS

Range

Mean w/SE

SD

WEIGHT

Range

Mean w/SE

SD

Oceanodroma

liomochroa

(20)

133-145

138.40 ±.65

2.91

(20)

79-89

83.10 ±0.67

3.01

(20)

13.10-15.10

14.10±0.11

0.50

(20)

21.50-23.70

22.46 ±0.14

0.63

(20)

33.3-42.4

36.90 ±0.51

2.27

O.castro

(6)

148-159

O.t.kelsalli

(36)

127-141

O.t.kelsalli

(4)

119-128

i:>2.00±1.73 133.39±0.49 124.50±2.02

4.24

(6)

71-75

72.33 ±0.61

1.51

(6)

14.40-15.80

14.85 ±0.22

0.55

(6)

21.50-22.50

22.00±0.15

0.36

(6)

40.5-45.0

42.67 ±0.68

1.66

2.92

(42)

58-67

62.26 + 0.30

1.91

(41)

10.60-14.00

12.40 ±0.09

0.60

(42)

20.00-23.60

22.02 ±0.13

0.86

(26)

21.0-33.0

25.48 ±0.61

3.12

4.04

(4)

56-61

59.25 ±1.11

2.22

(4)

10.90-12.00

11.73 ±0.28

0.55

(2)

20.25-21.00

20.75 ±0.25

0.35

O.melania

(47)

163-180

O.tristrami

(13)

175-195

Halocyptena

microsoma

(11)

114-123

171.96±0.55 183.15 ±1.70 118.45 ±0.98

3.75

(44)

82-94

88.41 ±0.47

3.10

(45)

14.00-16.10

15.22 ±0.07

0.48

(46)

29.00-33.30

31.48±0.14

0.96

(44)

50.0-67.0

58.95 ±0.56

3.69

6.14

(13)

109-118

3.24

(11)

52-60

113.54 ±0.83 57.00 ±0.80

2.99

(13)

16.30-18.30

17.36±0.18

0.65

(13)

25.10-28.60

27.38 ±0.28

1.02

(10)

58.4-94.0

82.53 ±3.04

9.62

2.65

(11)

9.60-11.60

10.72±0.17

0.57

(11)

19.10-22.10

21.00 ±0.26

0.85

(11)

18.2-21.7

20.47 ±0.34

1.11

Oceanites

oceanicus

(8)

148-156

Nesofregetta

albigularis

(21)

175-193

152.50±1.07 186.38±1.16

3.02

(8)

70-76

72.00 ±0.73

2.07

(7)

11.90-13.00

12.50±0.17

0.44

(8)

33.40-35.60

34.24 ±0.26

0.72

(7)

35.0-39.0

36.71 ±0.47

1.25

5.30

(21)

89-107

97.48 ±1.11

5.10

(20)

15.70-18.00

16.63±0.13

0.57

(21)

40.00-46.60

43.07 ±0.42

1.91

(19)

57.0-70.0

62.84 ±0.%

4.17

203
204

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE B.—Oceanodroma leucorhoa leucorhoa

Characters

and

measurements

WlNC

Range

Mean w/SE

SD

TAIL

Range

Mean w/SE

SD

CULMEN

Range

Mean w/SE

SD

TARSUS

Range

Mean w/SE

SD

WEICHT

Range

Mean w/SE

SD

Central Pacific (at sea)

males

(43)

144-161

153.60 ±.57

3.72

(52)

76-92

83.35 ±.42

3.05

(54)

15.10-17.50

16.01 ±.07

.52

(54)

22.00-25.10

23.48 ±.10

.75

(48)

29.0-49.0

38.73 ±.63

4.34

females

(31)

148-166

155.19 ±.82

4.56

(42)

77-93

84.33 ±.50

3.24

(41)

15.00-16.90

16.02 ±.07

.46

(41)

22.10-25.10

23.58 ±.10

.63

(37)

31.0-54.0

40.86 ±.78

4.74

Eastern Pacific (at sea)

males

(23)

140-162

151.57 ±1.22

5.86

(37)

67-87

81.84 ±.66

4.00

(35)

13.70-17.10

16.00±.ll

.63

(35)

20.00-25.00

23.61 ±.17

1.00

(30)

25.2-55.1

44.03 ±1.25

6.85

females

(12)

144-162

152.08 ±1.73

5.99

(36)

73-95

84.00 ±.72

4.34

(36)

13.30-17.00

15.89±.12

.74

(36)

21.40-25.10

23.74 ±.16

.98

(35)

24.0-57.5

43.17±l.O2

6.03

North Pacific (breeding)

males

(4)

149-158

153.75±1.89

3.77

(4)

82-89

86.00 ±1.47

2.94

(4)

15.00-16.50

15.78 ±.32

.63

(4)

21.70-24.10

23.20 ±.56

1.12

fe vi ales

(6)

153-167

157.67 ±2.03

4.97

(4)

78-89

82.25 ±2.36

4.72

(6)

15.00-16.50

15.62 ±.23

.56

(4)

23.80-25.00

24.20 ±.28

.57

Total

(119)

140-167

153.68 ±.45

4.89

(175)

67-95

83.43 ±.28

3.72

(176)

13.30-17.50

15.97 ±.04

.598

(174)

20.00-25.10

23.59 ±.06

.84

(150)

24.0-57.5

41.35 ±.47

5.77

TABLE C.—Oceanodroma leucorhoa beali

Characters

and

measurements

WING

Range

Mean w/SE

SD

TAIL

Range

Mean w/SE

SD

CULMEN

Range

Mean w/SE

SD

TARSUS

Range

Mean w/SE

SD

WEIGHT

Range

Mean w/SE

SD

Eastern Pacific (at sea)

males

(33)

136-155

145.61 ±.78

4.48

(60)

71-86

79.17 ±.45

3.51

(56)

14.20-16.70

15.43 ±.08

.59

(61)

20.00-25.00

22.81 ±.13

1.03

(53)

32.00-52.00

40.93 ±.65

4.91

females

(34)

139-159

146.09 ±.75

4.36

(66)

71-89

79.95 ±31

4.15

(59)

14.00-16.60

15.44 ±.08

.65

(64)

20.00-25.10

22.70 ±.16

1.26

(56)

29.00-53.00

40.13 ±.67

5.03

California &

males

(30)

142-155

147.40 ±.71

3.87

(20)

73-85

79.00 ±.71

3.17

(24)

14.00-16.10

15.03 ±.11

.52

(21)

21.50-24.40

22.69 ±.16

.75

Alaska (breeding)

females

(26)

143-155

148.81 ±.65

3.31

(18)

74.5-85.9

78.57 ±.68

2.90

(23)

14.20-15.50

14.87 ±.08

.40

(18)

22.00-24.00

22.94 ±.12

.53

Coronados

males

(15)

144-154

148.80 ±.78

3.03

(6)

77-78

77.67 ±.21

.52

(14)

14.40-16.20

15.21 ±.14

.54

(6)

21.50-22.70

22.07 ±.20

.50

(6)

34.00-38.00

36.33 ±.76

1.86

(breeding)

females

(17)

139-155

148.65 ±1.01

4.18

(9)

81-84

82.44 ±.34

1.01

(17)

13.50-16.00

14.99±.14

.58

(9)

21.00-22.80

22.28 ±.19

.58

(9)

32.00-37.00

34.11 ±.51

1.54

Totd\

(155)

136-156

147.24 ±.33

4.15

(179)

71-89

79.45 ± .27

3.63

(193)

13.50-16.70

15.26 ±.04

.61

(179)

20.00-25.10

22.72 ±.08

1.03

(124)

29.00-53.00

39.85 ±.45

5.04
NUMBER 158 205

TABLE D.—Oceanodroma leucorhoa chapmani

Characters and

measurements

WING

Range

Mean w/SE

SD

TAIL

Range

Mean w/SE

SD

CULMEN

Range

Mean w/SE

SD

TARSUS

Range

Mean w/SE

SD

WEIGHT

Range

Mean w/SE

SD

San Benitos (breeding)

males females

(45)

140-150

145.44 ±.37

2.48

(39)

74-82

77.33 ±.37

2.29

(45)

14.00-16.00

15.16±.08

.57

(40)

20.00-23.50

21.73±.ll

.72

(39)

29.00-39.00

33.97 ±.35

2.18

(40)

144-153

148.28 ±.39

2.44

(39)

74-85

78.62 ±.38

2.36

(41)

14.50-16.50

15.47 ±.07

.48

(39)

20.00-24.00

22.23 ±.13

.80

(39)

30.00-42.00

35.59 ±.46

2.90

Total

(85)

140-153

146.78 ±.31

2.83

(78)

74-85

77.97 ±.27

2.40

(86)

14.00-16.50

15.31 ±.06

.55

(79)

20.00-24.00

21.97 ±.09

.80

(78)

29.00-42.00

34.78 ±.30

2.68

TABLE E.—Oceanodroma leucorhoa socorroensis

Characters

and

m easu vements

WING

Range

Mean w/SE

SD

TAIL

Range

Mean wySE

SD

CULMEN

Range

Mean w/SE

SD

TARSUS

Range

Mean w/SE

SD

WEIGHT

Range

Mean w/SE

SD

Eastern Pacific (at sea)

males

(20)

131-150

142.05 ±.92

4.12

(20)

67-81

73.05 ±.92

4.14

(21)

13.00-15.20

14.02 ±.12

.54

(22)

18.30-22.10

20.52 ±.19

.90

(14)

25.20-40.00

32.71 ±1.13

4.23

females

(26)

134-153

142.46 ±.77

3.90

(28)

68-81

74.43 ±.58

3.05

(26)

12.90-15.00

13.88±.ll

.54

(28)

18.80-21.90

20.40 ±.15

.77

(16)

28.0-42.0

33.32 ±.97

3.89

Guadalupe

males

(68)

134-146

141.07 ±.33

2.73

(44)

68-79

73.73 ±.42

2.81

(45)

13.00-15.50

14.20 ±.11

.74

(45)

19.00-22.80

20.52 ±.13

.89

(66)

24.00-44.00

31.41 ±.43

3.46

/. (summer breeding)

females

(49)

136-150

142.71 ±.46

3.22

(38)

68-80

74.29 ±.48

2.98

(39)

13.30-1550

14.08 ±.09

.56

(38)

19.00-22.30

20.23 ±.13

.81

(45)

22.40-42.10

32.29 ±.56

3.76

Guadalupe I. (winter breeding)

" kaedingi"

males

(22)

140-150

144.68 ±.59

2.75

(18)

70-82

77.72 ±.75

3.20

(18)

13.50-15.90

14.82±.13

.56

(18)

21.00-23.00

22.09 ±.15

.62

(7)

22.80-43.80

32.70 ±3.52

9.32

females

(20)

140-147

143.70 ±.72

2.34

(17)

73-84

78.24 ±.67

2.77

(17)

14.00-15.60

14.82 ±.11

.43

(17)

20.90-23.50

22.02±.15

.60

(4)

22.40-37.50

29.80 ±3.56

7.12

Total

(205)

131-153

142.38 ±.23

3.31

(165)

67-84

74.79 ±.27

3.51

(166)

12.90-15.90

14.23 ±.05

.67

(168)

18.30-23.50

20.75 ±.08

1.04

(152)

22.40-44.00

31.71 ±.34

4.16
Red-tailed Tropicbird {Phaethon rubricauda)*

Patrick J. Gould, Warren B. King, and Gerald A. Sanger

Introduction

The material contained in this report is a summary of all at-sea observations of Red-tailed Tropicbirds (Phaethon rubricauda) gathered by the

Pacific Ocean Biological Survey Program (POBSP)

in the central and eastern Pacific Ocean. Humphrey (1965) has given a general summary of the

objectives of this program, while Gould (pp. 1-5,

herein) has summarized the areas surveyed, the

methods and materials used in obtaining and analyzing the data, and has acknowledged all personnel who have taken part in the gathering of the

data. The reader is referred to the latter paper for

a more complete account of these activities. Literature records and data obtained from POBSP island

surveys are included as general background information.

Pelagic observations began in August 1963

and continued through November 1968. During this

time over 2200 Red-tailed Tropicbirds were recorded during 2968 days (over 21,500 hours) and

more than 208,000 miles of diurnal observations.

SUMMARY OF PUBLISHED PELAGIC DISTRIBUTION.—

Red-tailed Tropicbirds are typically wide ranging,

solitary, and highly pelagic seabirds. Individuals

have been recorded from 39°N to almost 38°S, and

from about 300 miles off the western American

coasts (extreme southern California to Chile) to

southeastern Australia, Formosa, and Honshu, Japan. Population estimates for the central Pacific

Patrick J. Gould, Department of Zoology, University of Arizona, Tucson, Arizona 85721. Warren B. King, International

Council for Bird Preservation, Smithsonian Institution, Washington, D. C. 20560. Gerald A. Sanger, National Marine

Fisheries Service, Northwest Fisheries Center, 2725 Mont lake

Blvd. East, Seattle, Washington, 98112.

• Paper Number 84, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D. C. 20560.

islands visited by the POBSP indicate total numbers

in that area to be in excess of 31,000 birds (Table

33).

The appendix table summarizes significant published pelagic observations. Only birds specifically

noted as Phaethon rubricauda are included in this

list. A number of sightings of "tropicbirds" or

"Phaethon sp." are omitted, as are those suggesting

any uncertainty in identification. Despite these precautions, it is possible that some of the included

sight records were in error since immature Redtailed Tropicbirds resemble Red-billed Tropicbirds (Phaethon aethereus).

In general, Red-tailed Tropicbird sightings are

widely scattered across the tropical and subtropical

Pacific. Birds have been seen in higher latitudes

in the far western Pacific than in the far eastern

Pacific. Austin and Kuroda (1953:315) list six

specimen records for Honshu, Japan, the northernmost from 39°N, 142°E. In the southern hemisphere, Hindwood (1955) lists several records from

New South Wales (ca. 28°S to 30°S), and the adjacent ocean. Falla, et al. (1967:59-60) speculate that

this species may penetrate the Tasman Sea. Peter

Harper (pers. comm.) confirms this with a sighting

of two birds at 42°S. In contrast, the highest eastern

Pacific latitude sightings recorded are at Guadalupe

Island, ca. 29°N (Kaeding, 1905) and 12°S

(Bourne and Radford, 1961:22). The POBSP records

extend the known range of the species in the eastern

Pacific to 31 °N and to 24°S.

BREEDING PHENOLOGY.—The breeding cycle of individual Red-tailed Tropicbirds in the central Pacific is annual, but the cycles for any given population may be extended or irregular. On most islands,

birds have been recorded at some stage of breeding

activity during all months. In the northwestern

Hawaiian Islands breeding activity begins in late

206
NUMBER 158 207

TABLE 33.—Recent maximum population estimates1

 of Red-tailed Tropicbirds for central

Pacific islands visited by the POBSP

Location

HAWAIIAN ISLANDS

Kure

Midway

Pearl and Hermes Reef

Lisianski

Laysan

Gardner Pinnacles

French Frigate Shoals *

Necker

Nihoa

Kaula

Lehua

WAKE ATOIX

JOHNSTON ATOLL

MARSHALL ISLANDS

Taongi

Bikar

Eniwetok

Taka

Jemo

Erikub

LINE ISLANDS

Palmyra

Christmas

Jarvis

Maiden

Starbuck

PHOENIX ISLANDS

Canton

Enderbury

McKean

Birnie

Phoenix

Hull

Sidney

Gardner

HOWLAND

BAKER

Number

2,500

7,500

165

3,000

4,000

50

225

200

500

common

500

20

110

525

125

150

25

3

1

20

8,000

2,000

40

10

10

1,000

500

50

175

3

4

4

130

20

1

 High count for one day of breeding and displaying adults.

1

 Includes breeding and displaying adults and chicks.

March when a few eggs are laid, but May and June

appear to be the principal months of egg-laying.

Chicks have been recorded in all months but are

most common in July and August. Maximum numbers of adults have been recorded between April

and September; numbers then diminish rapidly to

a low in December and January.

On Johnston Atoll, the population follows the

same breeding pattern except that it is about one

or two months ahead of the Northwest Chain. The

egg-laying peak is in late March, and chicks are

present from late April through August. The maximum population occurs in May, and numbers diminish after July.

In the Phoenix and Line groups the breeding cycle is similar to that of the Leewards but may be

somewhat later. On some islands egg-laying peaks

are decidedly variable. The breeding cycle of birds

in the Marshall and Gilbert islands has not been

documented. On Wake Island breeding occurs

mainly from March through July or August.

Behavior

Definitions of special terms used in this section

are as follows: a "sighting" refers to one or more

birds observed together and acting as a unit; a

"flock" is considered to be the association of five or

more individuals; a "mixed" flock or sighting is

one that contains more than one species; a "pure"

flock or sighting is one that contains only one species, "BPS (birds per sighting)" is a good index of

the gregariousness or flocking tendency of a species.

In this section all data, except when specifically

stated otherwise, were collected under the following conditions: (1) at sea (including areas immediately offshore), (2) within about one mile of the

ship, (3) in the central Pacific, (4) from 1964

through 1966. Within these parameters 1574 Redtailed Tropicbirds and 1323 Red-tailed Tropicbird

sightings were recorded (Table 34).

Red-tailed Tropicbirds are among the most solitary of seabirds. Of all individuals seen, 73.2 percent

(87.2 percent of all sightings) were alone. The BPS

ratio was 1.19 (Table 34) as compared with Sooty

Terns (Sterna fuscata) and Wedge-tailed Shearwaters (Puffinus pacificus) which had BPS ratios of

12.79 and 4.56, respectively (derived from Tables 2

and 17). Further, only 4.5 percent of all individuals

(4.4 percent of all sightings) were associated with

other seabirds. Table 35 gives the frequency with

which Red-tailed Tropicbirds were associated with

other species of seabirds. The infrequency of such

associations can best be explained by tropicbird
208

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 34.—Frequency of Red-tailed Tropicbirds in the central Pacific Ocean,

1964-1966

Birds per sighting

1

2

3

4

5

6

7

Total

Sightings

(No.)

1153

118

37

7

4

2

2

1323

Total sightings Birds

<%) (No.)

87.2

8.9

2.8

0.5

0.3

0.15

0.15

(mean number ol

1153

236

HI

28

20

12

14

1574

birds per sighting:

Total birds

(%)

73.2

15.0

7.0

1.8

1.3

0.8

0.9

1.19)

behavioral patterns, particularly those connected

with feeding.

Red-tailed Tropicbirds are regularly attracted to

ships, which they often follow for ten or fifteen

minutes and occasionally for an hour or more.

This, in itself, would decrease the chances of observing them in association with other species, since

most other species are not ship followers. The major attraction of the ship is apparently the flying

fish scattered by its approach. Tropicbirds circle

above or behind the ship at estimated heights averTABLE 35.—Frequency of Red-tailed Tropicbird

sightings associated with other seabirds, 1964-1966

Seabird species

Sterna fuscata

Puffinus pacificus

Phaethon Upturns

Pterodroma externa ..

Pterodroma nigripennis

Fregata species

Anous stolidus

Bulweria bulwerii ... .

Gygis alba

Sula dactylatra

Sula sula

Oceanodroma leucorhoa

Puffinus griseus

Puffinus puffinus

Puffinus nativitatis . . .

Pterodroma alba

Peterodroma neglecta

Sterna lunata

Catharacta skim

Stercorarius pomarinus

Sightings

(No.)

Sightings

32

24

14

11

10

9

5

5

4

4

3

3

2

2

2

1

1

1

1

1

2.4

1.8

1.1

0.8

0.8

0.7

0.4

0.4

0.3

0.3

0.2

0.2

0.2

0.2

0.2

0.1

0.1

0.1

0.1

0.1

aging 40 meters (n = 307 sightings, range 3 to ca.

250 m). While circling, their heads are held downward, bill pointing toward the water. When a fish

is spotted they half-fold their wings and drop to the

water in a controlled dive, often changing direction

to compensate for movement of the fish. In 17 recorded instances diving heights ranged from 10 to

50 meters (average of 25 m).

Unlike the feeding behavior of most seabirds in

our study area, all Red-tailed feeding was accomplished only by the "plunge to surface" and "direct

to prey air dive" methods described by Ashmole

and Ashmole (1967:70-71). We have one record of

possible "contact dipping" (see below), but in this

instance the bird may have lost sight of the fish and

pulled out of the dive before hitting the water since

it was not noted to have captured a fish. The following examples are taken directly from POBSP field

notes:

CONTACT DIPPING?

15 August, 1964. 1818 Hours. Anonymous. ". . . another dive

from 100 feet just skimmed surface of water."

PLUNGE TO SURFACE

09 January 1965. 0715 Hours. Warren King. "2 birds. Birds

were feeding, dropping into water from 40 feet or so,

breaking their fall slightly with their wings and steering

as well. Did not appear to go below surface. Wings

somewhat extended a split second after impact keeping

birds on surface."

DIRECT TO PREY AIR DIVE

07 February 1964. 0844 Hours. Patrick Gould. "1 bird made

at least 6-10 dives, 2 from at least 100 feet up. Bird

half closed its wings, steering with wings, did not break

fall, completely submerged in water with great splash,
NUMBER 158 209

•

HIGH |

3 YEAR I

LOW |

| HIGH I3YEAR

3 YEAR I AVERAGE

SUNRISE SUNSET

FU.URE 126.—Hourly densities of Red-tailed Tropicbirds in the central Pacific, 1964-1966. Number of hours of observation per time period ranged from 183.7 at 0400 to 1151.6 at 1500. Total

hours of observation equal 15,962.0.

but did not remain in water for longer than 2 seconds.

A series of shorter dives were also made. One bird, after

starting its dive, altered its direction to more of an

incline and spiraled down, evidently keeping the fish in

sight at all times. It was noted to check itself in middive several times but this appeared to be due to movement of prey rather than trying to reduce speed."

The above feeding habits are probably incompatible with the feeding habits of other species in

mixed flocks where the birds are concentrated and

swirling in circles over the food. A diving bird

would not be able to keep a fish in sight or avoid

swirling birds. Although boobies (Sula) use the

"direct to prey air dive" when by themselves, they

apparently always switch to "dipping" or "surface

dive" when in mixed flocks. Tropicbirds are apparently not as versatile as boobies, and, even when

attracted to mixed feeding flocks, generally remain

on the periphery.

Red-tailed Tropicbirds have been recorded at all

hours of the day but are most commonly observed

in the morning. Peak numbers occurred around

1000 hours (Figure 126). Nocturnal density figures

are low due to the difficulty in seeing and identifying single birds at night. Most birds were active,

but 14.2 percent of all individuals recorded were

sitting on the water. Many of the birds were apparently roosting on the water and were flushed by the

approaching ship.
210 SMITHSONIAN CONTRIBUTIONS TO ZOOLOCY

TABLE 36.—Measurements (in mm) of Red-tailed Tropicbirds from the central

Pacific

Area and source Sample size Range Mean Standard error

Laysan (Stager, 1964)

Northwestern Hawaiian Islands and

Johnston Atoll (POBSP)

At sea, N of 10°N (POBSI>)

At sea, 4°N-10°N (POBSP)

At sea, S of 4°N (POBSP)

Line and Phoenix (POBSP)

Marquesas, Tuamotus, Society, etc. (Stager,

1964)

Laysan (Stager, 1964)

Northwestern Hawaiian Islands and

Johnston Atoll (POBSP)

At sea, N of 10°N (POBSP)

At sea, 4°N-10°N (POBSP)

At sea, S of 4°N (POBSP)

Line and Phoenix (POBSP)

Marquesas, Tuamotus, Society, etc. (Stager

1964)

7

22

79

12

18

21

7

7

21

77

12

17

21

Wing

307-322

301-329

287-343

307-344

315-350

310-345

320-344

Exposed

58-63

50-66

57-69

59-65

61-67

59-68

length

313

316

316

320

329

334

330

culmen

61

61

62

62

63

63

_

1.5

1.4

3.4

2.5

2.1

-

_

0.6

1.0

0.6

0.4

0.6

62-70 66

Specimen Records

Two races have been recognized in the central

Pacific. Phaethon rubricauda rothschildi (Mathews)

breeds on the northern islands, including Johnston

Atoll, Wake, and the northwestern Hawaiian Islands. A larger form, P. r. melanorhynchos Gmelin

breeds on islands farther south, including the Marquesas, Line, Phoenix, Tuamotu, and Society islands. Wing length and exposed culmen are the

major distinguishing criteria. These races appear

to represent parts of a broken cline of increasing

size from north to south. Our measurements (Table

36) show that birds from northern islands (Johnston

Atoll and the northwestern Hawaiians) have shorter

average wing and exposed culmen lengths than

birds from Line and Phoenix islands. These in

turn apparently have shorter average exposed culmens (Stager, 1964) than birds from farther south

and east (Marquesas, Tuamotus, and Society islands).

Specimens have been taken at sea in every month

of the year and along all commonly used POBSP

cruise tracks. Greatest numbers were collected from

June through November, the period, also, when

the greatest number of sightings was recorded.

Specimens collected at sea in the central Pacific

were divided into three groups for analysis: (1)

those collected north of 10°N, (2) those collected

between 10°N and 4°N, and (3) those collected

south of 4°N (Table 37). Birds collected north of

10° N agree in mensural characteristics with those

of the northwestern Hawaiian population. Birds

collected south of 4°N are larger than those from

the northwestern Hawaiian population areas but

slightly smaller than birds from the southern islands. Birds collected in the intermediate zone are

intermediate in their measurements, but fall closer

to the northern population.

Eighteen specimens (all but three either immature or subadult) were collected at sea in the eastern Pacific (Table 37). These show the same tendency for larger birds to be found in southern latitudes, and smaller birds to be found in northern

latitudes. Two specimens in the United States National Museum (USNM 212164, 212165), collected

at 10°N, 130°W, conform in size, as expected, to the

population from the northwestern Hawaiian Islands.

Exceptions to the above pattern do occur. Seven
NUMBER 158 211

TABLE 37.—Measurements (in mm) of POBSP specimens from the eastern Pacific,

latitudes south to north (SA = subadult, IM = immature, AD=adult)

Area

24°14'S, 75°27'W

24°14'S, 75°27'W

24°14'S. 75°27'W .

23°45'S, 75°45'W

23°45'S, 75°45'W .

23°45'S, 75°45'W .

17°02'S. 106°46'W

16°34'S. 107o01'W

14°08'S, I08°26'W

14°00'S, 104°58'W

13°2rS, 108°53'W

9°57'S, 112°23'W

2

O

S1'S, 118°50'W

l°05'N, 11

8

c

08'N, 1

8°08'N, l

13O41'N, 112°20'W

31°39'N, 123°22'W

Date Age Sex Wing length Exposed oilmen

22

22

22

22

22

22

15

15

16

4

16

23

27

21

3

3

11

13

Apr

Apr

Apr

Apr

Apr

Apr

Mar

Mar

Mar

Mar

Mar

Aug

Feb

Mar

Nov

Nov

Feb

Feb

65

65

65

65

65

65

68

68

68

67

68

67

68

68

67

67

67

67

SA

SA

SA

SA

SA

SA

IM

AD

IM

SA

IM

SA

AD

IM

SA

SA

SA

AD

9

9

S

S

9

$

9

9

9

9

9

9

9

9

9

9

9

330

320 (worn)

314

332

329

312

321

334

332

344

339

323

321

334

318

322

328

310

68

66

69

68

64

68

68

68

66

63

70

65

63

64

63

61

62

59'

* Banded on Kure Atoll.

TABLE 38.—At-sea recoveries of banded Red-tailed Tropicbirds (AD=adult,

SA=subadult, L=local, N = nestling)

Location

Kure

Kure

Kure

Midway

Midway

Laysan

Christmas

Jarvis

Jarvis

Jarvis

Enderbury

Banding

Date

14 Oct 64

1 Apr 64

15 Oct 64

14 Feb 64

27 Jul 65

10 Sep 67

21 Nov 64

15 Nov 64

16 Nov 64

15 Nov 64

2 Oct 65

Age

L

AD

N

AD

AD

AD

N

N

N

N

N

Location

31°39'N, 123°22'W

4°40'N,154°20'W

38°30'N, 178°30'W

125 mi SW Midway

33°O2'N, 154°34'W

15°00'N, ln'SCW

1°57'N,177°26'W

0°22'S, 178°38'W

1°17'N,177°44'W

0°38'N,176°35'W

7°3O'S, 170°49'W

Recovery

Date

13 Feb 67

30 Nov 67

28 Apr 70

10 Jul 64

15 Nov 66

27 Feb 68

17 Sep 66

15 Oct 66

10 Dec 66

7 Feb 66

1 Dec 66

Age

AD

?

?

AD

AD

?

AD

AD

AD

SA

SA

Sex

9

?

?

?

?

?

9

9

$

S

Elapsed

Months

28.0

8.0

66.4

6.9

15.6

5.6

21.9

23.0

25.1

14.7

14.0

Miles

3300

2,000

600

125

1 3 0

3,100

1.200

1,060

1,060

975

270

exceptionally large birds (wing=335-342 mm, exposed culmen = 64-69 mm) were collected north of

10°N and are referable to P. r. melanorhynchos.

The northernmost location was at 17°52'N, 166°

20^ . Two each were taken in April and September and three in November. Conversely, two exceptionally small birds (wing=315-319 mm, exposed

culmen = 62-62 mm) have been taken south of 4°N

and are referable to P. r. rothschildi. The southernmost location was at 00°21'S, 178°38/W. One each

was collected in April and October.

There is no way of proving the island of origin

of a bird collected at sea unless it was banded as a

nestling. It is reasonable, however, to assume that

most birds collected north of 10°N originated on

northern islands because of the agreement in measurements between island and at-sea specimens. On

the same basis we can assume that the birds collected south of 4°N most likely originated on the

southern islands. It thus appears that Red-tailed

Tropicbirds, especially young, disperse widely at

sea, but tend to remain within the latitudinal range

of their respective populations.

Six specimens, assigned by us to P. r. melano-
212

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

rhynchos and collected off northern Chile (three at

23°45'S, and three at 24°15'S), represent a considerable extended range to the southeast for this species. One bird, originally banded as a local on

Green Island, Kure Atoll, and collected off northern Baja California (31°39'N, 123°22'W), represents a northeast range extension. Its measurements

conform to the P. r. rothschildi population.

Eleven banded birds have been recovered at sea

(Table 38). Although the sample size is small, these

recoveries support the preceding arguments that

birds disperse widely but tend to remain within

the latitudinal boundaries of their respective populations. The Kure bird recovered at 04°40'N appears to be an exception; however, this latitude is

approximately at the southern border of the Equatorial Countercurrent, which is the dividing line

between several northern and southern seabird distribution patterns.

Molt

Molt in Red-tailed Tropicbirds appears to take

place nearly continuously except when individuals

are within a breeding cycle. Not one individual of

57 adult birds collected on many islands of the

central Pacific, including the Hawaiian, Line, Phoenix, and Marshall groups and Johnston and Howland islands, was molting remiges or rectrices, although several birds showed light body contour

feather molt.

The juvenal appearance, characterized by heavy

black vermiculations over the entire dorsal surface,

a black suffusion spreading into the vanes, both dorsally and ventrally, from the black dorsal shafts of

the larger primaries, excluding the outermost,

short, white central rectrices and a blackish bill,

changes within 15 months, probably starting with a

complete annual molt, to a distinctive subadult

form which probably persists (on the basis of two

specimens, 15 and 16 months, respectively) well

into the second year, when it is gradually replaced

by the typical adult form. Subadults have white

backs and rumps, flecked with black, but the vermiculations on head and nape remain. The primary vanes become entirely white, the shafts remaining black dorsally. The central rectrices elongate, although not to the extent of adults, and get

the first hint of reddish pigment. The bill becomes

increasingly yellow, excluding the base which remains dark. Between 15 or 16 months and 23

months all black spots have disappeared from the

dorsal surface except the central portion of the

vanes of the longest secondaries which remain black

in all age classes. The black vermiculations of head

and nape remain only at the bases of feathers of

this area and are masked by white, which condition

persists in adult birds. The central rectrices are red

but possibly not as long as those of breeding birds.

It may be possible to distinguish some third year

birds from older birds by their orange rather than

red bills (the nares remain dark even in breeding

birds) and by the retention of black spots in a few

dorsal secondary coverts, often well hidden. Otherwise, they are indistinguishable from breeding

birds. Our sample in this age class is four birds, 23,

24, 26, and 29 months. Most do not breed until at

least four years, possibly older. Thus, there is a

period of at least one year when birds have adult

appearance but do not breed.

Because the breeding cycles of populations are

not precisely synchronized, but extend in some

cases nearly year-round, and because there is evidently some mixing at sea of populations from the

southern and northern hemispheres, some of the

birds collected in any given month at sea are undergoing flight feather molt. In only 4 months

(June, August, September, and December) were

more than one-half of adults taken at sea not molting remiges and rectrices. Subadult and immature

birds (those with at least some black vermiculations

on their backs) molt almost continuously. Only 5

of 54 immature or subadult birds (9.3 percent) were

molting neither remiges nor rectrices, whereas 27

of 81 adults (32.5 percent) had no rectrix or remex

molt. All 18 birds collected in the eastern Pacific

(Table 37), 3 adults and 15 subadults or immatures,

were undergoing molt of flight feathers.

The pink flush that appears in the plumage of

some adult birds is evidently not tied directly to

breeding. Eight of 81 (9.9 percent) adult birds

taken at sea had a pink flush; only 2 of these were

not molting flight feathers.

REMEX MOLT.—Remex molt proceeds outward

from the carpal joint toward the outermost primary, and inward along the secondaries toward the

body. Secondary molt will not be considered further here. Primary molt can occur at one locus, or

at 2 or 3 loci simultaneously.
NUMBER 158

number of loci

0 (no molt)

1

2

3

number of specimens

34

52

41

8

percent of

total specimens

25.2

38.5

30.4

5.9

135 100.0

Because the innermost primaries were often difficult to identify on the specimens, and, therefore,

molt of Remiges 1 or 2 might have been overlooked, some specimens recorded molting at 1 or 2

loci might have been molting actually at 2 or 3

loci. Of those birds molting at 2 or 3 loci, the mean

number of feathers between loci was 3.3 (range 0-

6). Remex molt is usually symmetrical.

number of feathers

between loci

0

1

2

3

4

5

6

number of

occurrences

6

2

8

13

13

13

2

RECTRIX MOLT.—Red-tailed Tropicbirds usually

have 14 rectrices, including the two red elongate

central feathers, although 9 of 135 specimens taken

at sea (6.7 percent) had 16 rectrices, one apparently

had only 12 and 2 seemed to have 15.

Growth and replacement of the two central rectrices is apparently continuous. Even among breeding birds, otherwise not molting, one of the central

rectrices is usually shorter than the other and is

growing. Because molt of the central rectrices is

evidently not part of the normal molt cycle, it will

not be considered further here.

Rectrix molt is usually completed before remex

molt. Of 40 adults and 26 subadults or immatures

number of loci

0 (no molt)

1

2

S

4

number of

specimens"

150

83

34

1

1

percent of

total specimens

56.1

30.9

12.6

.2

.2

269b 100.0

* Each side is considered independently because rectrix molt

is frequently asymmetrical.

b

 The rectrices on one side of one specimen had been damaged to the extent that molt determination was impossible.

213

that were not molting rectrices, 13 adults and 21

subadults or immatures had not yet finished remex

molt. Only one adult and one immature of 135

specimens had completed remex molt but not rectrix molt. Rectrix molt usually proceeds from one

or two loci (see bottom of column 1).

Of those birds molting at two or more loci, the

mean number of feathers between loci was 2.1

(range 0-4).

number of feathers

between loci

0

1

2

3

number of

occurrences

S

9

14

8

5

It was not possible to determine the sequence of

rectrix molt, nor was there any obvious correlation

between the stages of remex and rectrix molt.

Distribution and Abundance

Figures 130-141 summarize the observations of

Red-tailed Tropicbirds made by POBSP in the central and eastern Pacific between 1963 and 1968.

Data from January (Figure 130), for example, are

taken from all years in which observations were

made that month. Each day's observations are expressed in terms of birds per mile of observation,

and are located on the maps at the position of the

ship at noon (open circles). Areas of equal density

were contoured to show relative abundance in different parts of the ocean and in different months.

Where single line oceanic transects prevented accurate contouring, contours were extended an arbitrary distance on either side of the cruise track,

just enough to indicate the densities encountered

along the track.

An annual pattern of pelagic occurrence is evident in the monthly distribution maps. In order to

examine this pattern more closely, the absolute density of Red-tailed Tropicbirds (birds per 100 mi2

)

was determined for each month, for each of four

broad latitudinal bands between 30°N and 20°S

(20°-30°N, 10°-20°N, 0°-10°N, 0°-20°S).

CENTRAL PACIFIC.—The Red-tailed Tropicbird

was present throughout the pelagic central Pacific

during all months. Abundance in the region was

generally low in late winter and spring and high in

summer and fall (Figure 127a). As is the case with
214

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

J A N FEB MAR APR MAY JUN JUL AUG SEP O C T NOV DEC

MAXIMUM ISLAND POPULATION

o

o

oc 3.

Q.

a

ac

CQ

2.5

1.5

.5

«- Sfi o - - - - .

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

FIGURE 127.—Absolute density of Red-tailed Tropicbirds (birds per 100 square miles) in 10°

wide latitudinal zones: A,B, in the central Pacific; c, in the eastern Pacific.

most other seabirds, the pelagic distribution of

Red-tailed Tropicbirds is greatly affected by the

breeding cycle. Adults tend to remain near breeding islands while breeding, particularly in the early

stages (i.e., egg-laying and incubation). This was

reflected in the differences in abundance observed

between the latitudinal bands of 20°N to 30°N

and 10°N to 20°N (Figure 127a). The former area

encompasses the major breeding islands, and most

cruises within this area remained relatively close to

land. In contrast, the latter area includes only one

small breeding location (Johnston Atoll), and most

cruises within the area were far from land. The

only months when densities in the 20°N to 30°N

area were greater than those of 10°N to 20°N were

in June through August, when peak numbers occurred on the breeding islands. In the 10°N to

20° N zone, densities were relatively high from

September through November; the July peak can

be explained by one day of observation near Johnston Atoll, when density was high (.18 birds per

mile). Figure 1276 shows a typical annual cycle
NUMBER 158 215

BREEDING

i ^ i .. i ~ i n S O NDJFMAMJJAS'O'N'D'J' F

FIGURE 128.—Diurnal abundance of Red-tailed Tropicbirds in a pelagic area near Howland

Island.

110° 120° 130° 140° 150° 160° 170°t 180° I7O°W 160° 150° 140° 130° 120° 110° 100° 90° 80° 70°

110° 120° 130° 140° 150° 160° 170°E 180° 170°W 160° 150° 140° 130° 120° 110° 100° 90° 80° 70°

FIGURE 129.—Range of the Red-tailed Tropicbird (Phaethon rubricauda) in the Pacific Ocean.

Dark lines indicate the location of the 22°C isotherm in summer (after Muromtzev, 1958).
216 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

for a relatively small pelagic study area, 50 miles

off Johnston Atoll.

The absolute density (birds per 100 mi2) of the

species was calculated for a pelagic area near Howland Island for the period September 1965 through

February 1967 (Figure 128). Peak numbers (1.9

birds/100 mi2) occurred in October 1966, immediately following the Howland Island breeding season. Relatively high numbers (1.2 birds/100 mi2

)

also occurred in August 1966, during the breeding

season.

EASTERN PACIFIC.—Although our data are incomplete for the eastern Pacific, the species was present

each month observations were made. Observations

were made in all months except April, May, and

December (Figure 127c).

WESTERN PACIFIC.—The Red-tailed Tropicbird

apparently occurs in the southwestern Pacific more

commonly during the southern summer than during other seasons. Of the 24 records from the

southwestern Pacific in the appendix for which

there are definite dates, 18 were from October

through March. Sorensen (1964) states that this

species occurs year-round in the Kermadec Islands,

but most abundantly from October through May.

Environmental Factors

It was noted that this species ranges to higher

latitudes in the western Pacific than in the eastern

Pacific (see Appendix). This is probably explained

by the fact that the Kuroshio and East Australian

Currents carry relatively warm water to relatively

high latitudes in the western Pacific.

The range of this species, as indicated in Figure

129, generally parallels the summer surface water

isotherms of ca. 22°C in both the north and south

Pacific (Muromtzev, 1958, figs. Ill, 112). Similarly,

the distribution of surface salinity in the Pacific

Ocean (Muromtzev, 1958, fig. 134) suggests that the

species does not range into waters with salinities

less than 33.5-34.0%o in the northern hemisphere

and less than 35.O2U in the southern hemisphere.

Its range appears limited to the waters between

the bounds of the north and south subtropical

convergences.

It is apparent from the preceding documentation

of the northern and southern subspecies that transequatorial movements are minimal. It seems

possible that the rich equatorial current region,

especially the countercurrent, acts as a restraint to

bihemispheric movement of the subspecies, i.e.,

because of the increased abundance of food in the

equatorial region, birds flying north from the

south Pacific would have no reason to continue

northward beyond the equatorial current region,

and the same would apply to northern birds flying

south. The pattern of distribution noted in the

February map (Figure 131) may possibly be explained by this.

Discussion

The Red-tailed Tropicbird has an extremely

wide pelagic range, which includes virtually all of

the tropical and subtropical Pacific. It generally

ranges to higher latitudes in the western Pacific

(30°-35°N) than in the eastern Pacific (20°-25°N).

Although there is little direct supporting evidence,

it seems probable that most of the population stays

within latitudes of less than ca. 30° in both hemispheres, but that individual birds occasionally

wander to higher latitudes, or are carried there by

storms.

It is apparent from our specimen data that a

strong tendency exists for birds breeding on southern islands to remain in more southern latitudes,

although they may disperse widely within these

areas. Racial mixing in pelagic areas, however, does

occur and individuals may be found far north or

south of the usual range of their respective populations.

The distribution and abundance of Red-tailed

Tropicbirds in the central Pacific appears to be

generally correlated with the breeding season. The

period (June through August) of maximum abundance and closest proximity to land in the northern

part of their range corresponds to the breeding

season in the Hawaiian Islands. Minimum abundance is found immediately following the dispersal

of fledged young from the breeding grounds, and

birds are absent from the vicinity of the islands

the rest of the year. Peak abundance occurred at

sea near Howland Island immediately following

the breeding season.

Although our data from the eastern tropical

Pacific do not cover all months, there appear to be

peaks in abundance in both winter (February) and

summer (August). The winter peak possibly contains some central Pacific breeders; the pelagic oc-
NUMBER 158 217

turrence of the species in the central Pacific is at a month that POBSP cruises were conducted, these

low ebb at this time. Our data suggest that pre- being all months except April, May, and December,

breeders are more likely to visit the eastern Pacific Thus, it seems quite probable that the species octhan breeding age birds. Birds were seen each curs in the eastern tropical Pacific year-round.
218 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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Appendix

Summary of published data on Red-tailed Tropicbird distribution

Location

EAST-CENTRAL PACIFIC

30° N, 132°W

Guadalupe I., Mexico

Clipperton I., Mexico

8°N, 119°W to Manzanilla,

Mexico

Manzanilla, Mexico to9°S,

120°Wtoca.5°N, 139°W

6°N,82°W

0°26'N, 98°36'W

0°07'N( 87°50'W

l°10'S, 100°S7'W

3°58'S,91°15'W

4°02'S, 110°31'W

5°15'S, 113°W

8°03'S, 133°36'W

SOUTHEAST PACIFIC

12°S, 100°W

Easter I.

CENTRAL PACIFIC

30°N, 150°W

27°19'N,172°25'W

22°N, 165°W

17°44'N, 159°56'W

7°N,166°W

7°46'S, 167°16'W

8°40'S, 136°54'W

Nuku Hiva, Marquesas

Near Marquesas

SOUTH-CENTRAL PACIFIC

13°37'S, 177°18'W

Near Suva, Fiji

27°06'S, 177°41'E

28°18'S, 177°01'E

29°12'S, 178°28'E

Kermadec I.

NORTHWEST PACIFIC

Honshu, Japan

Date

no date

23 Jul 1897

19 Aug 1958

1-19 Oct 1955

24 Oct-20 Nov 1955

2 Jan 1963

22 Nov 1957

2 Apr 1950

28 Feb 1947

1 Apr 1950

22 Nov 1957

10 Nov 1960

30 Sep 1928

25 Apr 1960

Dec 1968

26 Jul 1959

24 Aug 1960

28 Apr 1945

20 Jul 1959

4 Nov 1960

31 Oct 1928

1 Oct 1928

2 Oct 1928

Dec 1955

24 Jul 1959

31 May 1959

13 Dec 1928

9 Dec 1928

11 Dec 1928

all year

May 1907; 1885;

20 Nov 1934:

Remarks

seen continuously around ship

1 specimen

1 specimen (adult $)

infrequent

singles and pairs frequently seen

1

1

1

1

1

3

1, possibly 4 others

6 in 3 sightings

1 on board ship

fair numbers, breeding

1 seen close for 1 \/z hrs.

6

3

1

1

1

1

a few

none

1

1

1

3 in 2 sightings

1

most from Oct to May

4 records are for spent, "probably

storm-driven birds"

Source

Mdrzer Bruyns, 1965:63

Kaeding, 1905:109

Stager, 1964:360

King and Pyle, 1957:36

• • • • • •

Morris in Bourne, 1965:29

Gibson, 1960:16

Laird, 1951:177

Fleming, 1950:172

Laird, 1951:177

Gibson, 1960:16

Semple in Bourne and Radford,

1962:21

Jespersen, 1933:216

Harrison in Bourne and Radford,

1961:21

Johnson, et al., 1970:535-536

Agnew in Bourne and Radford,

1961:22

Wilhoft, 1961:261

Cogswell, 1946a:48

Wilhoft, 1961:261

Morzer Bruyns, 1965:63

Jespersen, 1933:216

„ „

„ „

King and Pyle, 1957:36

Wilhoft, 1961:261

Peakall, 1960:201

Jespersen, 1933:216

.. ..

„ „

Sorensen, 1964:73

Austin and Kuroda, 1953:315

230
NUMBER 158 231

Summary of published data on Red-tailed Tropicbird distribution—Continued

Location

Linschoten I.

WEST-CENTRAL PACIFIC

West Pacific

Western tropical Pacific

Taiwan

25°26'N,124°18'E

19°09'N,120°05'E

15°N, 160°W-l°S, 148°W

10°N, 150°-120°W

Mariana and Caroline I.

Palau I.

SOUTHWEST PACIFIC

Thursday I.

15°30'S, 159°45'E

17°57'S, 169°52'E

23°28'S, 127°31'W

24°40'S, 164°W

25°13'S> 130°28'W

26°16'S, 161°24'E

26°15'S, 176°56'W

28°20'S, 140°45'W

3O°55'S, 155°17'E

32°H'S, 155°07'E

33°25'S, 162°45'E

33°27'S, 157°1O'E

33°3O'S, 165°53'E

New Zealand

Northern New South Wales,

Australia

Port Kembla, N.S.W., Australia

coastal N.S.W.

Tasman Sea

18°16'S, 151°21'W

9°53'S, 161°28'W

2O°57'S, 158°58'W

Date

1917; 30 Mar

1951; no date

14 Aug 1906

no date

Aug 1945-Mar 1946

21 May 1937

30 May 1929

22 May 1929

4-5 Dec 1955

1-19 Oct 1955

no date

28 Oct 1960

18 Mar 1929

Jun 1951

10 Dec 1957

9 Jul 1948

11 Mar 1947

2 Dec 1948

19 Dec 1957

14 Mar 1947

29 May 1955

20 Dec 1957

24 Feb 1929

27 Jan 1929

29 Jan 1929

26 Jan 1929

1877, 1936, 1942

17 Jun 1945

13 Nov 1955

12 Jan 1955

no date

18 Oct 1928

24 Oct 1928

21 Oct 1928

Remarks

1 observed, may be more common

than supposed

4 widely scattered sightings

6 sightings from 66 to 195 mi from

land

1 offshore

1

1

singles and pairs frequently seen

infrequently seen

uncommon throughout most of Micronesia, may be a resident only

in the northern Marianas

1

1

1

2 approached from direction of New

Hebrides

3 birds in 2 sightings

1

several off Pitcairn I.

1

1

no details

1

1

2

3

1

only 3 records

hurricane-driven bird, 120 mi from

coast, at altitude of over 1000 ft

1

bird found dead

may penetrate area as far as 38°S

1

2 in 2 sightings

a few

Source

Clark, 1910:42

MacDonald and Lawford, 1954:22

Dixon and Starrett, 1952:270

Hachisuka and Udagawa, 1951b: 124

Jespersen, 1933:216

" "

King and Pyle, 1957:36

Baker, 1951:71

Morzer Bruyns, 1965:63

Jespersen, 1933:216

MacDonald and Lawford, 1954:22

Gibson, 1960:18

Fleming, 1950:175

Fleming, 1950:172

Fleming, 1950:181

Gibson, 1960:18

Fleming, 1950:172

King in Bourne, 1964:28

» . . . . i,

Jespersen, 1933:216

.. ..

Oliver, 1955:195

Hindwood, 1947:57

Gibson and Sefton, 1956:198

Hindwood, 1955:160

Falla.etal., 1967:59-60

Jespersen, 1933:216
Recoveries of Banded Laysan Albatrosses (Diomedea immutabilis)

and Black-footed Albatrosses (D. nigripes)*

Chandler S. Robbins and Dale W. Rice

Introduction

This paper summarizes the distribution of at-sea

recovery records of banded Laysan Albatrosses

{Diomedea immutabilis) and Black-footed Albatrosses (D. nigripes). Both species now nest primarily in the leeward Hawaiian Islands, and both

roam over the north Pacific Ocean, covering essentially the entire area from Japan to the continental

United States and from the vicinity of the Aleutian

Islands south to about 20° N. Maps showing the

breeding sites and the total marine range for both

species (prepared by E. M. Reilly, Jr.) have been

published in Volume 1 of (he Handbook of North

American Birds (Palmer, 1962). Although these

maps indicate the known limits of occurrence, they

do not attempt to show concentration areas, seasonal changes in distribution or abundance, or

differences in distribution of the various age classes.

More than two dozen papers have been published summarizing observations at sea of one or

both species of albatross in various parts of the

north Pacific Ocean—primarily along the American

and Japanese coasts and along the main transPacific shipping lines. Unfortunately, these publications have been limited both geographically and

seasonally and only two papers (Shuntov, 1968;

Fisher and Fisher, 1972) have come close to bracketing the entire range of either species.

Chandler S. Robbins, Migratory Bird and Habitat Research

Laboratory, United States Bureau of Sport Fisheries and

Wildlife, Laurel, Maryland 20810. Dale W. Rice, Northwest

Fisheries Center, Marine Mammal Division, Sand Point

\'SA, Building 192, Seattle, Washington 98115.

•Paper Number 101, Pacific Ocean Biological Survey Program, Smithsonian Institution, Washington, D.C. 20560.

Shuntov (1968) gave summer and winter maps

for each species, showing concentration areas, normal range, and the area within which each species

is rare. Fisher and Fisher (1972) summarized the

geographic occurrence at sea of Laysan Albatrosses

based on a combination of 109 recoveries of birds

they had banded, 53 published records of birds

banded by others, and 113 sight records. They

pointed out four regions in which Laysan Albatrosses tend to congregate. They described seasonal

shifts in concentrations, and they attempted to explain distribution and movements in relation to

turbulences, eddies and currents, water temperatures, and food supply. Our findings, based on a

much larger sample of banded birds, both Laysan

and Black-footed Albatrosses, show a more orderly

distribution pattern, both for adults and for the

various age classes of subadult birds.

ADVANTAGES OF USING BANDING RECOVERIES.—The

use of recoveries of banded birds as a means of

showing geographic range at various seasons and

for various age groups has several distinct advantages over compiling published data from sight

observations. The age of the great majority of

banded birds is known, permitting mapping of

distribution and relative abundance by age group.

Except for a very short period in the first season

at sea, there is no way to distinguish birds of the

year from older birds by means of sight observations. Recovery records are accumulated over many

years, thanks to the long life span and the long

period over which both species have been banded

in good numbers. This prevents abnormalities of

weather, human activities, or bird distribution

from unduly affecting the total picture. All portions of the oceanic range are included in the re232
NUMBER 158 233

covery reports, even though there is geographic

and probably seasonal variation in intensity of

recapture effort. For a comparative study of the

distribution of these two species, the use of banding recoveries offers a fairly uniform means of

sampling populations throughout the area in which

both species range.

LIMITATIONS OF BANDING RECOVERIES.—The principal biases involved in using banding recovery

data relate to geographical differences in human

contact with the birds and in reporting rate. Since

most of the at-sea recoveries of banded albatrosses

have come from fishing vessels, the recoveries are

concentrated in those locations that are most heavily used for fishing—especially longline tuna sets.

Variation from month to month and from year to

year in fishing activity also greatly influences human contact with albatrosses. Unfortunately, accurate figures on relative fishing effort throughout

the north Pacific are not available on a monthly

basis, year by year. If they were, this would permit

mapping recoveries per unit of fishing effort and

result in a more meaningful analysis of albatross

distribution than is presently possible. Nevertheless, Japanese longline fishing effort is well distributed over most of the north Pacific as shown by

Rothschild and Uchida (1968:21), and as reflected

in the recovery records that have been obtained.

Changes in geographic concentrations of albatrosses

may very well be related to similar changes in distribution and abundance of the commercial fishery

resource, so the centers of concentration of the

birds may actually be localized in the areas where

the greatest fishing activity takes place. Shuntov

(1968:1064) concluded that "albatrosses are most

numerous in waters with an increased biological

productivity."

Banding recoveries generally cannot be used to

describe the extreme geographical limits of a bird's

range, because only a small percentage of the birds

banded are recovered. Thus the areas where a species is common are much better represented by recovery records than are the marginal portions of

the range. This paper, therefore, deals primarily

with seasonal changes in the centers of populations

of the various age groups rather than with records

of individual birds.

The Black-footed Albatross has a more varied

diet than the Laysan, is more readily attracted to

fishing vessels (and other boats) and so is much

more likely to be captured at sea. Thus, recovery

rates cannot be used to compare abundance of one

species with the other in any region of interest.

Differences in the ratio of Laysan to Black-foot

recoveries from one part of the range to another,

however, can be used to show geographic differences in relative abundance. Furthermore, differences in the distribution of the various age classes

can readily be detected, since it is unlikely that

there are any geographical biases that would favor

selective capture of one age class over another.

Birds in their first three or four years, especially

Laysan Albatrosses, appear to be more susceptible

to capture than fully adult birds, but this holds

true in all parts of their range. The recovery rate

for Laysan Albatrosses reached a strong peak in

their second summer, while the highest recovery

rate for Black-footed Albatrosses occurred in their

third summer.

BANDING HISTORY.—The first Laysan Albatrosses

were banded by F. C. Hadden at Midway Atoll in

1937, and the first Black-footed Albatrosses, by

George C. Munro at the same location in 1940.

Banding continued on a small scale through 1952,

largely under the auspices of George Munro and

the Hawaii Audubon Society, with several hundred

albatrosses banded at Midway in most years. Some

335 adults were banded by Johnson Neff and

Philip A. DuMont of the U.S. Bureau of Sport

Fisheries and Wildlife in 1954.

The great majority of the banding of both species was done during the period 1956-1969. During

1956-1967, the U.S. Bureau of Sport Fisheries and

Wildlife, at the request of the U.S. Navy, conducted studies on albatrosses on Midway and some

of the other leeward Hawaiian Islands to obtain

information on albatross biology and habits that

could be used in reducing the hazard of birds to

aircraft at Midway. And during the period 1963-

1969, the Pacific Ocean Biological Survey Program

of the Smithsonian Institution included an extensive banding program on all the major nesting

islands of the Laysan and Black-footed Albatrosses.

Nearly all of the banded birds were tagged in

their nesting colonies in the leeward Hawaiian

Islands, but four of them were captured and banded

at sea, and one was banded on Torishima Island,

Japan. The great majority were banded on the

Midway Islands (28°13'N, 177°20'W), but there

are also a few recoveries from albatrosses banded at
234 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 39.—Manner of recovery of Laysan and Black-footed Albatrosses

Action

Shot

Caught on fish hook

or net

Caught and released

with band

Caught by hand ... .

No information

Found dead

Miscellaneous ... .

Total

Young

11

121

6

6

22

22

2

190

Laysan

Adult

17

22

2

3

12

2

1

59

Albatross

Total

28

143

8

9

34

24

3

249

Percent

11.2

57.4

3.2

3.6

13.7

9.6

1.2

99.9

Black-footed Albatross

Young

19

68

3

9

7

19

6

131

Adult

18

72

17

4

16

19

6

152

Total

37

140

20

13

23

38

12

283

Percent

13.1

49.5

7.1

4.6

8.1

13.4

4.2

100.0

Kure Atoll, about 90 miles west of Midway, and

68 from birds banded on islands in the Hawaiian

Islands National Wildlife Refuge (French Frigate

Shoals, Laysan, Lisianski, and Pearl and Hermes

Reef), between Midway and the main Hawaiian

Islands. The nesting islands on which the recovered albatrosses were banded extend in nearly a

straight line from 23°40'N, 166° lOW to 28°20'N,

178°10'W, a distance of about 1000 nautical miles.

SOURCE OF DATA.—The recovery records on

which this paper is based are from the files of the

Bird Banding Laboratory of the U. S. Bureau of

Sport Fisheries and Wildlife at the Office of Migratory Bird Management in Laurel, Maryland.

Although the great majority (73%) of the birds

discussed in this paper were banded by the authors

(54%), and by POBSP personnel (19%), 76 of the

recoveries are from birds banded by H. I. Fisher

and assistants (Fisher and Fisher, 1972), 37 were

banded by R. R. Sheehan, 28 by E. Kridler, 21 are

from bandings by George Munro and his collaborators of the Hawaii Audubon Society, and from

1 to 8 each are from bandings by 13 other individuals. This analysis includes recovery records processed through August 1972.

Summarized herein are 324 recoveries of Laysan

Albatrosses from 165,890 birds banded from 1937

through 1969, and 399 recoveries of Black-footed

Albatrosses from 48,727 birds banded from 1940

through 1969. Since tens of thousands of birds from

these banded samples are still alive, including some

individuals from nearly all years of banding, the

figures given here cannot be used to compute final

recovery rates.

Although most of the banding recovery records

specified the date and the latitude and longitude

of recapture, some oceanic records had to be omitted because of insufficient data. Also omitted were

all recaptures on the various nesting islands.

MANNER OF RECAPTURE.—The principal means

of recovery of banded albatrosses at sea is by fishermen who capture the birds on baited hooks or

in nets. The large majority are taken on longline

tuna gear; a typical set (Rothschild and Uchida,

1968) contains 2000 hooks on 120 kilometers of

line. As shown in Table 39, more than 50 percent

of a sample of more than 500 recoveries received

for each species were reportedly obtained by this

means. Many of the birds listed in other categories,

e.g., found dead, caught by hand, caught and

released with band, and no information, probably

also were taken on fish hooks or in nets. It is apparent from Table 39 that both species are equally

susceptible to being recovered in the various manners listed. Thus, although the Black-footed Albatross more frequently comes in contact with man

through its habit of following ships, there is no

apparent bias in favor of one species or the other

being taken by fishing gear rather than by other

means.

Both adult and young Black-footed Albatrosses

appear to be equally susceptible to being recovered

by each of the listed categories, with the possible

exception of the first. The manner of recovery of

young Laysan Albatrosses is very similar to that of

Black-footed Albatrosses. Adult Laysans, however,

are much less frequently reported as captured in
NUMBER 158 235

nets or on hooks, and a higher proportion of these

birds were obtained by shooting.

Figure 142 shows the monthly distribution of

recoveries at sea of the Laysan and Black-footed

Albatrosses combined, according to manner of recovery. The top line shows all birds caught on fish

hooks or in nets. The bottom solid line shows the

recoveries of birds that were shot, and the dashed

line shows birds recovered by all other means.

It is apparent from Figure 142 that fishermen

encounter albatrosses most frequently in the months

of May, June, July, and August, and least frequently in September, October, and November.

The largest numbers obtained through shooting

were in May, June, September, and October; and

almost none were shot in December, January, and

February. The seasonal distribution of birds obtained by other methods so closely parallels the

graph for birds that were caught on fish hooks

that the fishing industry probably accounts for most

of the birds reported by "other" means.

ACKNOWLEDGMENTS.—We wish to thank Eugene

Kridler of the U.S. Bureau of Sport Fisheries and

Wildlife for his cooperation not only on the Midway studies, but also for making available his banding recoveries from the Hawaiian Islands National

Wildlife Refuge (French Frigate Shoals, Lisianski,

and Pearl and Hermes Reef). Other Bureau collaborators who contributed materially to the banding of these albatrosses were Karl W. Kenyon, Dr.

John W. Aldrich, Cdr. E. P. Wilson, Edward J.

O'Neill, Dr. Paul A. Stewart, Norman E. Holgersen, John Waters, Willis C. Royall, Jr., Johnson

Neff, and Philip A. DuMont.

Navy and Coast Guard personnel not only provided the necessary logistical support, but also

assisted in many other ways. Cdr. Glenn Wilson,

Lt. Ralph Stockstad, James L. Priest, Lt. Kenneth

C. Balcomb, and Marvin L. Cunningham banded

albatross chicks in our study plots in years when

we were not present at the proper season.

Mrs. Blanche A. Pedley of the Hawaii Audubon

Society went to considerable effort to supply banding data from the Society's files in order to complete the official records of birds banded by George

Munro and Miss Grenville Hatch.

Personnel from the Pacific Ocean Biological Survey Program of the Smithsonian Institution under

the direction of Dr. Philip S. Humphrey conducted

intensive banding during the period 1963-1969 and

FISH HOOKS

AND NETS

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

FIGURE 142.—Manner of recovery of banded Laysan and

Black-footed Albatrosses at sea.

also cooperated closely with us in many ways. One

hundred thirty-nine recoveries used in this report

were from birds banded by them.

We are indebted to Harvey I. Fisher for checking

nesting albatrosses on our study plots at times

when we could not be on Midway, and for the use

of recoveries of birds banded by him and included

in his publication (Fisher and Fisher, 1972).

We also acknowledge with thanks the following

banders, each of whom contributed one or more

recovery records to this study: Fred C. Hadden,

Richard C. Harlow, J. H. Scarlett, R. Sheehan,

Eric E. Smith, Yamashina Institute for Ornithology,

and Dr. C. F. Yocom.

We appreciate the fine international cooperation

of Dr. Y. Yamashina of the Yamashina Institute for

Ornithology and Dr. Tatsuo Udagawa, both of

Tokyo and of A. Vinokurov and T. Shevareva of

the Centre of Ringing in Moscow. Through their

efficient processing and reporting recovery information, actual dates and exact positions of nearly all

western Pacific recaptures were made available.

We thank Brian Sharp and Jay M. Sheppard

of the Bird Banding Laboratory for providing

copies of banding recovery records, and Rosemary

O'Loughlin and Nancy Mullis for assistance in
236

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

locating some original recovery letters for confirmation of locations and dates. Danny Bystrak prepared the final maps.

We also thank Mr. Warren King, Mrs. Herbert

Church, and Mr. Gerald Sanger of the Smithsonian

Institution's POBSP for their many helpful suggestions regarding this manuscript.

General Patterns of Distribution

The following summary of the nesting cycle of

both species is condensed from Rice and Kenyon

(1962b:564-566). The nesting birds arrive on the

islands in the latter half of October (Black-footed

Albatross) and first half of November (Laysan Albatross). Egg-laying occurs primarily in the latter

half of November (Black-footed) and from November 20 to January 5 (Laysan), and incubation requires about 65 days. Early in the incubation

period the female, and then the male, is away at

sea for about three weeks at a time. As incubation

progresses, each mate's turn on the egg becomes

progressively shorter as does the distance they can

travel from the island. For the first 12 to 24 days

after hatching, the chick of each species is attended

by a parent, the male and female changing place

at intervals of about two days. Both parents then

leave the chick and forage independently; a parent

returns to feed the chick at an average interval of

one and one-half days to two days. Departure from

the island of both young and adults of both species

takes place primarily in June but departure of the

Laysan continues into July.

Our studies with both species, and those by

Fisher and Fisher (1969) on the Laysan Albatross,

have shown that one-year-old birds do not return

to the nesting islands, but remain continuously at

sea. By the end of their second winter at sea, a

very few individuals of each species return to their

natal islands in April. With increasing age these

nonnesting birds return to their islands in larger

numbers, and earlier and earlier in the season

(largely in March for the 3- and 4-year-olds and as

early as February or January for the older birds).

In order to determine the distribution patterns

of the albatrosses during the periods they are away

from the nesting islands, recoveries for each species

were plotted on a monthly basis for birds in their

first, second, third, and fourth years at sea and for

adults. First-year recoveries were of birds from time

of fledging until the following May.

Recoveries of Laysan Albatrosses occurred largely

during the period December through July, with a

peak of adult birds (40%) in May and June and a

peak of young birds (31% of the year's recoveries)

in June of the year after fledging.

Recovery records of the Black-footed Albatross

at sea are strongly clustered around the months of

March through August. Half (50%) the recoveries

of birds in their second, third, and fourth years

of life were reported in June and July, and the

peak of reporting of adult recoveries (45%) was in

the months of March, June, and July. The fewest

recoveries for both young and adults were obtained

in the months of November and December.

LAYSAN ALBATROSS.—Banding recoveries (Figure

143) indicate that young Laysan Albatrosses spend

their first summer primarily between 40° N and

45° N and that they range all the way from Japan

east to at least 172°W. More than half of the recoveries of Laysan Albatrosses during their first summer (summer of fledging) came from within 300

miles of the east coast of northern Japan. One bird

(band number 767-77884, banded as a chick by

Robbins on 30 March 1965, at Sand Island, Midway) was found dead on 11 September 1965, on San

Cristobal Island (10°15'S, 161°16'E), furnishing the

first record for the British Solomon Islands. This is

the only Laysan Albatross recovery from south of

the equator. Comparison of Figures 143 and 147

shows that the distribution of young Laysan Albatrosses during their first summer is quite different

from the distribution of adults during the same

months. Half of the recoveries of adults came from

north of 45°N, while only two birds in their first

summer were recovered north of 45 °N.

Laysan Albatrosses tend to be more widely scattered in their first four or five winters (December

through March), than at a later age. Four of the 43

first-winter recoveries (Figure 143) were from east

of the 180th meridian, as were 6 of the 17 thirdwinter recoveries (Figure 145). In contrast, there

was only one winter recovery east of the 180th

meridian for birds in their sixth winter or older,

even though the entire chain of nesting islands is

situated east of the 180th meridian. As was true in

the summer months, the records for the first winter

were concentrated off the coast of Japan, with half

of the recoveries coming from within 600 miles of

Japanese shores.
NUMBER 158 237

Recoveries during the second summer (Figure

144) were concentrated off the east coast of northern Japan, and it appears that birds of this age

stay much closer to shore than either first-year birds

or birds older than three years. All of the 55 recoveries of birds in their second summer occurred

west of 160°E.

Recoveries for the second winter at sea (Figure

144) were few in number (13), but they also were

all from west of 160°E. There was more overlap

between the summer and winter range of birds in

their second calendar year of life than in other

years.

Third-year recoveries (Figure 145) were similar

to second-year recoveries except that the birds appeared to scatter farther out to sea and were not

so concentrated near the Japanese coast. This was

especially true of birds in their third winter at sea,

because they ranged all the way east to 134°W.

Fourth- and fifth-year birds (Figure 146) tended

to range farther northeast in summer than did

younger birds during the same months. The summer season distribution of adults was still farther

to the northeast, with half of the birds north of

48°N and with the heaviest concentration off the

western Aleutian Islands.

As shown in Figure 147, at-sea recoveries of adult

Laysan Albatrosses lay almost entirely (90%) west

of the 180th meridian. The recoveries indicate

very little overlap between summer and winter

range. During the summer (May through 5 October), all but five of the recoveries came from north

of 40°N; while during the winter months (December through March), all except two recoveries

were from south of 40°N. The summer recoveries

were fairly uniformly distributed between northern

Japan and the Aleutian Islands, except for a concentration of records from the immediate vicinity of

the Aleutians. The winter recoveries of adults were

all from the area between Japan and their breeding islands in the leeward Hawaiian chain. In addition to the summer and winter recoveries, there

were widely scattered recoveries for the intervening

months of April, October, and November.

BLACK-FOOTED ALBATROSS.—After leaving their

nesting islands in June and early July, young Blackfooted Albatrosses scatter both eastward and westward to within a few hundred miles of the coasts

of North America and Japan. All of the nine firstsummer recoveries fell between 35°N and 45°N

(Figure 143).

In the first winter, the birds shift southward.

Nine of the 14 recoveries were between 30°N and

35°N, and the recoveries appeared to be slightly

more clustered than they were during the summer

season. One concentration was half way between

Japan and Midway; the other was close to the

shores of California and Baja California. There

was only one first-winter recovery in the vicinity of

the Hawaiian chain. The banding recoveries indicate a strong eastward shift in the population by

the second summer (Figure 144). All but 5 of the

31 recoveries came from the eastern half of the

north Pacific and half of these came from within

about 200 miles of Canada and the United States

(exclusive of Alaska). The principal concentration

of coastal recoveries of birds in their second summer extends from 30° N to 47 °N (13 out of 15 recoveries from south of Alaska).

Recoveries of birds taken in their second and

third winters (Figures 144, 145) suggest a shift toward the central Pacific. The total numbers involved, however, are admittedly very small (14

birds in their first winter, 6 in their second, and 8

in their third).

A decided northward trend in summer distribution with increasing age is indicated. The heaviest

single concentration in the third summer (Figure

145) was along the United States coast between

40°N and 51 °N; 24 recoveries were reported from

here as compared with 4 farther south and 1 farther north along the coast.

By the fourth summer (Figure 146), only 7 of

the 15 coastal recoveries were in the 40°N to 48°N

range; one was farther south, and 8 farther north

off Canadian and Alaskan shores.

The Black-footed Albatross has a greater distributional range than the Laysan both in latitude

and in longitude. It tends to winter farther south

than the Laysan and to be concentrated in winter

in the central portion of the north Pacific Ocean.

Recoveries of adults (Figure 148) within 1000 miles

of the Japanese coast in winter were just about

equal to the number within the same distance of

the North American coast at this season.

Summer recovery records of banded adults also

were quite uniformly distributed throughout the

north Pacific Ocean, except for concentrations

within 200 miles of the coasts of Japan, Alaska,
238 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

British Columbia, Washington, and Oregon. The

numbers of recoveries of adult birds east and west

of the 180th meridian were similar.

The separation of summer and winter records is

nearly as clear cut as for the Laysan Albatross.

There were only three summer recoveries of adult

Black-footed Albatrosses south of 30° N, and except

for five recoveries close to the California coast,

there were only two winter recoveries north of

35°N. The "winter" bird recovered at 50°N was

taken on 25 March 1966 and was actually an early

spring migrant. The other "winter" bird, at 37°N,

was taken on 9 December 1950 and could well have

been a late migrant.

A similar comparison may be drawn for birds in

their first four years. There was only one summer

recovery (out of 20) south of 35°N in the western

Pacific, and only six (out of 86) in the eastern Pacific. There was only one winter record north of

40°N.

Concentration Areas

LAYSAN ALBATROSS.—Shuntov (1968) showed two

concentration areas for the Laysan Albatross in

summer, as depicted in our Figure 149, and three in

winter (Figure 150). The banding recoveries show

the same summer concentration area extending east

from northern Japan; this is occupied primarily by

young birds near shore and older ones farther to

the northeast. The concentration that Shuntov pictures in his winter map along the south edge of the

western Aleutian Islands is a major feeding area for

adult Laysan Albatrosses in summer. There are no

winter banding recoveries from the vicinity of the

Aleutians. There are relatively few recoveries for

Shuntov's concentration zone between Kamchatka

and the western Aleutians, but several from a small

concentration of adult birds off the south tip of

Kamchatka. Figures 87, 88, 89 show the principal

concentration area of Laysan Albatrosses in July,

August, and September, a period in which sampling

effort is low and only 16 banding recoveries of

adults are available. First- and second-year birds

summer to the south of this concentration area.

The winter banding recoveries are strongly clustered between Japan and the nesting islands. This

zone includes Shuntov's western concentration and

the southern half of the large one south of Kamchatka. A large concentration of wintering firstyear birds occurs southeast of Japan as a southward

extension of his westernmost concentration.

Fisher and Fisher (1972) reported the concentration areas off Japan and the western Aleutians as

well as two others which neither Shuntov (1968,

figs. 4, 6), Sanger (p. 134 ff, herein), nor we consider

important: one off the west coast of British Columbia and the United States (from which there are

only four banding recoveries), and one around the

eastern end of the Hawaiian Islands (two recoveries). These surely must be of minor importance as

compared with the concentrations reported by

Shuntov (1968).

BLACK-FOOTED ALBATROSS.—The summer banding recoveries may exaggerate the importance of

the coastal waters as concentration areas for Blackfooted Albatrosses, but these recoveries are in close

agreement with Figures 73, 74, and 75. Shuntov's

(1968) summer distribution map (Figure 151)

shows major concentrations along the 40th parallel

west of Midway and through much of the eastern

Pacific. The banding records do not detect these

areas as being of any special significance, but show

heavy concentration zones only in the offshore area

from the Aleutians to northern California as

mapped by Shuntov. Banded birds also were concentrated off the coast of northern Japan in an

area not considered especially important by Shuntov. Quite possibly the large concentrations along

and to the south of the 40th parallel are undersampled by banding recoveries, because no more

birds have been reported from there than from

farther north.

The winter banding recoveries match well with

that part of Shuntov's map (Figure 152) that lies

south of 40°N. By including November records in

his winter map, Shuntov included a considerable

area north of 40° N that we do not consider as winter range. Otherwise, the principal differences are

a greater spread of banding recoveries to the west

of Midway, extending fully halfway to Japan, fewer

recoveries northeast of the Hawaiian chain, and

fewer along the south side of the chain.

Statistical Analysis of Geographic Range

The recovery records of each species were

grouped by months and by age of the birds, and

the mean, standard deviation, and standard error

were computed to determine which of the apparent
NUMBER 158

TABLE 40.-

239

-Mean position, standard deviation, and sample size of Lay&an Albatross band recoveries by

age and month (positions based on fewer than five records are in parentheses)

Month

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

1

-

-

(42.3°N-172.3°W)

-

1

42.18°N-151.91°E

2.95 7.86

15

44.60° N-l 47.54 °E

5.34 6.35

5

43.95°N-170.89°E

7.13 33.60

8

(39.83°N-143.87°E)

4.54 3.65

3

36.64°N-144.97°E

2.58 5.95

10

32.23°N-149.91°E

2.30 7.53

13

32.38°N-159.94°E

3.96 23.51

13

29.29°N-150.83°E

3.12 15.07

7

(48.45°N-156.38°W)

1.59 27.50

4

38.54°

3.95

41.05°

3.17

39.88°

2.59

(39.55°

5.30

(45.35°

1.20

41.32°

1.21

(40.05°

1.06

35.94°

1.65

(32.90°

5.52

(33.5°

-

(30.0°

_

(49.0°

-

2

N-148.03

5.04

11

N-147.16

5.72

24

N-l 47.67

4.41

17

N-147.00

4.67

2

N-l 49.25

3.61

2

N-l 44.78

3.33

6

N-146.50

4.95

2

N-l 46.43

6.57

9

N-l 42.50

2.12

2

N-l 35.7°

_

1

N-16O.O0

_

1

N-145.O0

-

1

°E

°E

°E

°E)

°E)

°E

°E)

°E

°E)

E

)

E

)

E)

Year at sea

42.36°

6.45

(39.43°

0.78

(43.17°

1.26

(46.45°

5.30

(33.0°

-

(36.82°

1.35

33.18°

3.33

(32.30°

1.73

(32.40°

2.52

(24.7°

-

3

N-156.56°E

17.13

5

N-144.80°E)

2.13

3

N-151.40°E)

7.29

3

-

N-165.10°E)

17.11

2

-

N-l 39.4 °E)

-

1

N-147.02°E)

3.10

4

N-158.17°E

23.34

6

N-l 70.35 °W)

30.71

4

N-147.20°W)

13.37

3

N-171.0°W)

-

1

4 and 5

44.64°N-166.10°E

6.52 9.57

5

43.39°N-164.31°E

3.42 30.72

8

-

(42.7°N-144.0°E)

-

1

(46.0°N-151.8°E)

-

1

(34.17°N-151.00°E)

11.26 6.38

3

(42.60°N-152.13°E)

4.68 1.40

3

(35.85° N-147.25°E)

0.21 8.41

2

-

(3O.17°N-159.7O°E)

2.52 26.34

3

(30.10°N-158.20°E)

5.37 19.09

4

(32.10° N-l 54.02° E)

6.62 26.54

4

6+

45.93° N-l 71.68°

6.24 19.36

22

47.89° N-168.43°

5.01 8.11

18

45.90° N-174.700

4.29 35.92

5

45.39° N-150.490

4.99 11.42

8

(47.10°N-176.33°

10.67 33.90

3

(47.55° N-l 72.80°

7.36 29.18

4

(37.52°N-160.30°

5.05 15.51

4

36.76°N-160.18°

4.45 13.31

5

35.36°N-145.12°

2.33 9.67

8

29.82°N-157.10°

1.00 12.14

6

33.46° N-157.660

5.82 21.68

10

40.00°N-176.60°

10.98 24.06

8

E

E

E

E

E)

E)

E)

E

E

E

E

E

differences in distribution were merely the result of

small sample size and which differences were statistically significant. Although the sampling technique (recoveries of banded birds) was far from

ideal from the statistical point of view, it was conducted the same way for all age groups of both

species, and should provide a valid means of portraying differences in distribution as a function of

age and season.

When broken down by years of age, many sample

sizes for a given month are of ten or fewer individuals (Tables 40, 41). Starting with these small samples for each age and each month, comparisons

were made with adjacent months and adjacent

years. Whenever the distribution was found to be

similar, other months or other years were included

to provide larger samples. These larger samples in

turn gave more critical comparisons between other

years and other seasons.

The largest sample for each species (with the exception of a few individual months) was the birds

of breeding age. This sample of adults, therefore,

was used for comparison with birds of the younger

age groups.

LAYSAN ALBATROSS.—Adult Laysan Albatrosses

were significantly farther north (p < .05) during
240

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 41.—Mean position, standard deviation, and sample size of Black-footed Albatross band recoveries

by age and month (positions based on fewer than five records are in parentheses)

Month

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

1

_

_

(39.5°N-177.7°W)

_ _

1

40.40°N-157.90°E

1.56 11.10

5

(40.77°N-165.53°W)

2.35 31.12

3

(39.40°N-167.25°E)

2.26 15.20

2

(35.2°N-171.7°E)

1

(33.3O°N-157.43°E)

130 16.90

3

(31.73°N-176.73°W)

135 4753

S

(36.8°N-124.0°W)

-

1

29.46°N-158.60°W

4.96 37.82

7

(40.20°N-135.77°W)

6.93 20.07

3

Year at sea

2

(365°N-141.0°E)

_

1

40.08°N-127.92°W

6.58 9.77

8

38.09°N-135.51°W

4.89 22.04

10

47.01 °N-172.19°W

12.18 34.95

8

(48.68°N-138.85°W)

6.92 20.18

4

(40.2°N-150.8°E)

-

1

(35.2°N-171.7°E)

-

1

(32.30° N-l 74.40° W)

0.71 22.06

2

-

(31.75°N-150.00°W)

2.47 0.71

2

(27.75°N-170.80°E)

6.01 2.83

2

(31.3°N-166.0°E)

-

1

3, 4, and 5

46.51 °N-147.95°W

8.87 30.07

15

45.15°N-1S2.34°W

7.18 20.83

21

45.05°N-134.06°W

5.87 22.96

31

46.89°N-160.80°W

6.38 43.11

8

48.94°N-147.32°W

4.89 3252

8

4S.42°N-169.28°E

8.93 32.36

5

(48.4°N-125.0°W)

-

1

-

31.30°N-159.08°W

7.71 22.87

5

(29.4°N-156.4°W)

-

1

33.14°N-176.00°W

3.98 42.14

5

(26.5°N-1753°W)

-

1

6 +

41.07°N-157.11°W

9.51 33.13

26

43.15°N-164.79°W

6.31 40.14

34

44.67°N-153.S7°W

5.51 37.05

42

46.66°N-162.46°W

5.63 34.58

25

48.97°N-166.32°W

7.62 31.80

9

41.16°N-149.94°W

10.56 28.67

12

(29.18°N-172.70°W)

8.95 17.71

4

32.62°N-179.77°E

4.18 13.28

6

30.63°N-173.31°E

2.66 15.76

14

29.91 °N-178.84°W

5.08 23.65

13

30.31°N-174.90°W

638 29.65

28

36.08°N-152.40°W

7.92 35.30

16

the months of May through August than from December through March. The 3- to 5-year-old birds

were significantly farther north from May through

November than from December through April.

Birds in their second year were significantly farther

north from June through November than from December through March.

The only statistically significant latitudinal difference among age classes of the Laysan Albatrosses

occurred in the month of May when adults were

farther north than birds in their second year of life.

There was a consistent trend, however, for birds in

their second year to be farther south than birds in

their third to fifth years, and for these in turn to be

farther south than the adults. This trend was noted

in the months of January, February, March, May,

June, and December. Sample sizes for one or more

of the age groups were insufficient to show any

trend for July, August, and November. Only in the

principal migration months of April, September,

and October did one of the three age classes not

conform to this general observation. This is in

marked contrast to the Black-footed Albatross, in

which there was not a single month when the mean

position in latitude increased progressively within

these three age categories.
NUMBER 158 241

BLACK-FOOTED ALBATROSS.—Adult Black-footed

Albatrosses were significantly farther north (p <

.05) from May through October than they were in

January through March, and significantly farther

north from June through September than from November through April. Birds in their third and

fourth years were significantly farther north from

May through July and September and October

than they were in February and March, and birds

in their second year were found significantly farther

north from June through October than in January

and March. There were too few records for many

of the other months. All age classes showed a high

degree of variability in latitude during the northward migration in the month of April, and to a

lesser extent during the southward migration in

October and November (when the small sample

size also made it difficult to draw conclusions).

The only significant differences in latitude for

different age classes in the Black-footed Albatrosses

were between first-year and adult birds in the

months of July, August, and September and between second-year and adult birds in the month of

July. In each of these cases the younger birds were

distributed significantly farther south (p < .05)

than adults.

The small number of significant differences

found does not mean that there are not differences

in distribution, but only that with the present

small sample sizes no other differences could be

confirmed as statistically significant.

Black-footed Albatrosses in their first year at sea

stayed significantly farther toward the western Pacific in July and August than did birds in any older

age group.

No significant differences in longitude were

found between the 2-year-old and the 3- and 4-yearold birds.

Significant differences in longitude were found

between adults (6 years and more) and 3- and 4-

year birds for the months of February, June, and

July. In each case, the adult birds were found farther west than the 3- and 4-year-olds.

In the Black-footed Albatross, birds in their third

to fourth year occur, on the average, farther north

than the adults in the months of January, February,

April, May, June, July, September, October, and

November. Only in March and August were the

adults farther north (insufficient data for December).

Comparison of Distribution of Laysan and

Black-footed Albatrosses

Despite the geographical and temporal biases inherent in the way in which albatrosses are recovered and reported, there are certain comparisons

that can be drawn between the ranges of the two

species (as long as both species are recovered in the

same general fashion). The most striking difference

between the recovery patterns of the Laysan and

Black-footed Albatrosses is the very heavy concentration of Laysan Albatross records within 1000

miles of the Japanese coast as compared with the

more uniform distribution of Black-footed Albatross records throughout the north Pacific Ocean.

Botli species demonstrate a strong tendency to wander both to the east and the west in their first eight

to ten months at sea. By the end of the first winter,

the two species begin to separate into distinct patterns. The Laysan Albatross moves strongly toward

the Japanese coast and the Black-footed Albatross

shows a less pronounced tendency in the opposite

direction.

Using the 180th meridian as the dividing line,

90 percent of the Laysans recovered spent their first

winter in the west and 50 percent of the Blackfooted Albatrosses spent their first winter in the

east. From the second year on, more than 90 percent

of the Laysan recoveries (all seasons) came from

the western half of the Pacific Ocean, and a similar

percentage of the Black-foots in their second, third,

and fourth summers came from the eastern half.

By the time the albatrosses reach breeding age

(generally 7 or more years of age for the Laysan

and 5 or more for the Black-footed), the geographic

separation during the summer months dissolves,

but the pelagic distribution patterns during the

winter (the breeding season) remain fairly distinct.

Although both species nest on the same islands, and

in about the same relative abundance even at both

ends of their breeding range, the great majority of

winter recoveries of Laysans were from west of

160°E, while most recoveries of Black-foots were

from east of this line. Nearly all winter recoveries

of Laysans were from north of 30°N, whereas more

than half of the winter recaptures of Black-foots

were south of 30°N. Both species are well distributed west of the 180th meridian in the summer

months, but nearly all of the summer recoveries
242 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

from east of the 180th meridian were of Blackfooted Albatrosses.

Comparative distribution of the two species at

sea throughout the year is summarized in Figures

153 through 164 where the hatching covers the

area represented by one standard deviation from the

mean latitude and longitude of all banding recoveries for the month. This is the range within which

two-thirds of the population is to be expected. On

each map, the range of the Laysan Albatross is centered to the left of that of the Black-footed Albatross. The maps show dramatically those months in

which one or both species is confined to a relatively

small area as compared with those months when

records are scattered over a large portion of the

north Pacific Ocean.

Maps for birds in their first summer and autumn

at sea were prepared by combining two months in

order to increase the sample size. Thus, Figure 165

shows combined records for the months of July and

August, and Figure 166 shows September and October. The November (Figure 167) and December

(Figure 168) maps are based on Laysan Albatrosses

in their first, second, third, and fourth years, and

Black-footed Albatrosses in their first and second

years, because there was no apparent difference between years and because the samples were very

small.

Mean recovery positions of adults of each species

are summarized by two-month periods (each month

weighted equally) in Figure 169. The large dots indicate positions based on 10 or more recoveries for

each month; the small dots are based on fewer than

ten in one or both months. Note the similarity between the patterns for the two species, even though

separated by 30° of longitude. A similar chart for

Laysan Albatrosses published by Fisher and Fisher

(1972), apparently was based on a mixture of banding recoveries (birds of all ages) and sight observations. Their sample would seem too small to be

representative.

Recovery positions of adults of the two species

were compared statistically on both a monthly and

seasonal basis by means of the "t" test. The winter

(December through March) distribution of adult

Laysan Albatrosses was significantly different (p <

.05 for latitude, p < .01 for longitude) from that

of adult Black-footed Albatrosses for the same

period; mean positions were 34.3°N, 153.3°E for

the Laysan (n = 29) and 30.3°N, 178.5°W for the

Black-footed (n = 53). Recovery positions in early

summer (May through July) also differed significantly (p < .05 for latitude, p < .01 for longitude) ; mean positions were 47.3°N, 167.5°E for

the Laysan (n = 45) and 43.5°N, 164.9°W for the

Black-footed (n = 84).

No difference could be detected between the distribution of recoveries from birds banded at Midway and Kure, at the west end of the leeward Hawaiian chain, and birds banded farther east at

Pearl and Hermes Reef, Lisianski, Laysan, and

French Frigate Shoals.

Discussion

The Laysan and Black-footed Albatrosses together utilize almost the entire Pacific Ocean north

of the tropics. Their distribution is limited by the

land masses of Japan, and the Asian and North

American continents, and by a line that follows

the continental shelf in the Bering Sea. Cone (1964:

83) has shown that albatrosses are incapable of sustained flight in calm air, so they could not survive

long in equatorial waters of the central Pacific.

Although Laysan and Black-footed Albatrosses

nest on the same islands, and although there is almost complete overlap in their total oceanic ranges,

each species has its own distinctive distribution pattern within its range, with significantly different

centers of population, month by month.

The pelagic ranges of the adults of both species

most closely coincide in February, when they are

making the shortest and most frequent foraging

trips to provide food for the newly hatched young.

Ranges expand in March as trips become longer

and as chick mortality relieves some of the adults

from "domestic" duties. Northward migration of

the nonbreeding adults in April and May gives a

wide distribution pattern, which contracts on the

summer feeding areas in June. The northward migration in June and July of the adults at the close

of the breeding season is hardly sampled by the

banding recoveries; it probably takes place rapidly

and through waters that are not being heavily used

by the fishing fleets.

The greatest northward penetration occurs in

September. The southward movement takes place

gradually during October and November, and by

December both species are within commuting

range of their nesting islands.
NUMBER 158 243

Young birds of both species during their first

summer and fall remain largely south of the range

of the adults at those seasons. In the first winter,

young Laysans remain closer to Japan than do the

adults. In their next four summers (Table 40, Figure 170), the average population center shifts gradually east-northeast from Japanese waters to the

adult summering area in waters south of the Aleutian Islands. There is also a tendency to move

slightly northward as each summer progresses.

It is not until January, February, and March of

the third winter at sea that there is a strong movement away from Japanese waters. This coincides

with the first return of many of these birds to their

natal islands in the month of March.

We have no explanation for the tendency of

young Black-footed Albatrosses to fly toward Japan

when they first leave their natal islands. Most of

these young birds seem to favor waters west of the

180th meridian through their first summer and fall,

though they spend subsequent summers and winters in the eastern half of the Pacific. The central

Pacific, which is the major wintering area of adult

Black-footed Albatrosses, is relatively clear of firstwinter birds.

In their second through fifth summers, Blackfooted Albatrosses remain closer to the Pacific

coast of the United States and Canada than do the

adults; and as each summer progresses they shift

gradually northward (Table 41).

In October and November, the majority of the

band recoveries of subadult Black-footed Albatrosses of all ages come from the western Pacific

(west of the 180th meridian). Recovery records are

too few to permit comparison of winter ranges of

the various age groups.
244 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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Literature Cited

Ahlstrom, E. H., J. L. Baxter, J. D. Isaacs, and P. M. Roedel

1967. Report of the CalCOFI Committee. California Cooperative Oceanic Fisheries Investigations Reports,

11:5-9.

American Ornithologists' Union

1957. Check-list of North American Birds. 5th edition,

xiii + 691 pages. American Ornithologists' Union.

Amerson, A. B., Jr.

1969. Ornithology of the Marshall and Gilbert Islands.

Atoll Research Bulletin, 127:viii + 348.

Anonymous

1960. A Straggler of Puffinus pacificus to Fukui. Tori,

15(76):263.

Anthony, A. W.

1898. Avifauna of the Revillagigedo Islands. Auk, 15(4):

311-318.

1900. Nesting Habits of the Pacific Coast Species of the

Genus Ruffinus [sic]. Auk, 17(3):247-252.

Arnold, L. W.

1948. Observations on Populations of North Pacific Pelagic Birds. Auk, 65 (4):553-558.

Aronoff, A. E.

1960. Some Observations on Birds of Torishima. Tori,

15(76) :269-279.

Ashmole, N. P.

1963a. The Biology of the Wideawake or Sooty Tern

Sterna fuscata on Ascension Island. Ibis, 103b (3):

297-364.

1963b. The Regulation of Numbers of Tropical Oceanic

Birds. Ibis, 103b (3) :458-473.

1965. Adaptive Variation in the Breeding Regime of a

Tropical Sea Bird. Proceedings of the National

Academy of Sciences, 53(2):311-318.

Ashmole, N. P., and M. J. Ashmole

1967. Comparative Feeding Ecology of Sea Birds on a

Tropical Oceanic Island. Yale Peabody Museum of

Natural History Bulletin, 24:v+131.

Austin, O. L., Jr.

1952. Notes on Some Petrels of the North Pacific. Bulletin

of the Harvard Museum of Comparative Zoology,

107 (7) :391-407.

Austin, O. L., and N. Kuroda

1953. The Birds of Japan, Their Status and Distribution.

Bulletin of the Harvard Museum of Comparative

Zoology, 109 (4):280-637, 1 plate.

Bailey, A. M.

1927. Notes on the Birds of Southeastern Alaska. Auk,

44(l):l-23.

Bailey, R.

1968. The Pelagic Distribution of Seabirds in the Western

Indian Ocean. Ibis, 110(4) :493-519.

Baker, R. H.

1951. The Avifauna of Micronesia, its Origin, Evolution,

and Distribution. University of Kansas Museum of

Natural History Publication, 3(1): 1-359.

Barkley, R. A.

1962. A Review of the Oceanography of the Central Pacific Ocean in the Vicinity of the Line Islands. 37

pages. [Multilithed by the Biological Laboratory,

Honolulu, of the Bureau of Commercial Fisheries,

United States Fish and Wildlife Service].

Blake, E. R.

1953. Birds of Mexico, xxix + 644 pages, illustrations and

maps. Chicago: University of Chicago Press.

Bourne, W. R. P.

1957. The Sooty Petrel of Latham, Fregetta fuliginosa.

Bulletin of the British Ornithologists' Club, 77:40-

42.

1959. Notes on Sea Reports Received 1958-1959. Sea Swallow, 12:6-17.

1964. Observations of Sea Birds. Sea Swallow, 16:9-40.

1965. Observations of Sea Birds. Sea Swallow, 17:10-39.

1966. Observations of Sea Birds. Sea Swallow, 18:9-39.

Bourne, W. R. P., and M. C. Radford

1961. Notes on Observations of Seabirds Received during

1960. Sea Swallow, 14:7-27.

1962. Observations of Sea Birds. Sea Swallow, 15:7-27.

Brattstrom, B. H., and T. R. Ho well

1956. The Birds of the Revilla Gigedo Islands, Mexico.

Condor, 58(2): 107-120.

Bryan, E. H., Jr., and J. C. Greenway, Jr.

1944. Contributions to the Ornithology of the Hawaiian

Islands. Bulletin of the Harvard Museum of Comparative Zoology, 94(2):79-142.

Budinger, T. F., L. K. Coachman, and C. A. Barnes

1964. Columbia River Effluent in the Northeast Pacific

Ocean, 1961, 1962: Selected Aspects of Physical

Oceanography. University of Washington, Department of Oceanography Technical Report, 99:1-78.

California Marine Research Committee

1963. CalCOFI Atlas of 10-Meter Temperatures and Salinities 1949 through 1959. California Cooperative

Oceanic Fisheries Investigations Atlas Number 1.

Campbell, R. W., and D. Stirling

1968. Notes on the Natural History of Cleland Island,

British Columbia, with Emphasis on the Breeding

Bird Fauna. British Columbia Provincial Museum

Report for 1967, pages 25-43.

Chapin, J. P.

1954. The Calendar of Wideawake Fair. Auk, 71 (1) :1-15.

Cheng, T-h.

1955. [Record of the Distribution of Chinese Birds]. Volume 1, 240 pages. Peiping. [Translated from the

Chinese.]

272
NUMBER 158 273

Clapp. R. B., and P. W. Woodward

1968. New Records of Birds From the Hawaiian Leeward

Islands. Proceedings of the United States National

Museum, 124(3640): 1-39.

Clark, A. H.

1910. The Birds Collected and Observed during the

Cruise of the United States Fisheries Steamer "Albatross" in the North Pacific Ocean, and in the Bering, Okhotsk, Japan, and Eastern Seas, from April

to December, 1906. Proceedings of the United States

National Museum, 38 (1727) :25-74.

Cogswell, H. L.

1946a. Bird Study Aboard a Transport to the Western

Pacific, Elepaio, 6(7):46-48.

1946b. Bird Study Aboard a Transport to the Western

Pacific Elepaio, 6(8):53-54.

1946c. Bird Study Aboard a Transport to the Western

Pacific Elepaio, 6 (9) :62-63.

Cone, C. D., Jr.

1964. A Mathematical Analysis of the Dynamic Soaring

Flight of the Albatross with Ecological Interpretations. Virginia Institute of Marine Science Special

Scientific Report, 50:1-104.

Davidson, M. E. M.

1931. On the Breeding of Puffinus chlororhynchus in the

Tonga Group. Condor, S3 (5) :217-218.

DeAngelis, R. M.

1968. Typhoons of the Western North Pacific, 1967.

Mariners' Weather Log, 12 (3) :7S-79.

1969. Typhoons of the Western North Pacific, 1968.

Mariners' Weather Log, 13 (3) :9S-98.

Delacour, J.

1966. Guide des Oiseaux de la Nouvelle-Caledonie et de

ses Dependances. 172 pages, 4 plates. Neuchatel:

Delachaux et Niestle.

Delacour, J., and E. Mayr

1946. Birds of the Philippines, xv+309 pages. New York:

MacMillan Company.

Dement'ev, G. P., and H. Gladkov, editors

1951. [Birds of the Soviet Union.] Volume 2, xi+553

pages. Jerusalem: Israel Program for Scientific

Translations [1968]. [Translated from Russian.]

Dixon, K. L., and W. C. Starrett

1952. Offshore Observations of Tropical Sea Birds in the

Western Pacific Auk, 69 (3):266-272.

Dodimead, A. J., F. Favorite, and T. Hirano

1963. Review of Oceanography of the Subarctic Pacific

Region. International North Pacific Fisheries Commission Bulletin, 13:1-195.

Edgar, A. T.. F. C. Kinsky, and G. R. Williams

1965. The Kermadecs Expedition, 17-25 November, 1964.

Notornis, 12(l):S-43.

Falla, R. A.

1962. A Wedge-tailed Shearwater in New Zealand. Notornis, 9(8):278-279.

Falla, R. A., R. B. Sibson, and E. G. Turbott

1967. A Field Guide to the Birds of New Zealand and

Outlying Islands. 254 pages, 18 plates. London: Collins.

Fisher, H. I.

1967. Body Weights in Laysan Albatrosses, Diomedea

immutabilis. Ibis, 109(3) :373-S82.

1971. The Laysan Albatross: Its Incubation, Hatching

and Associated Behaviors. The Living Bird, 10:19-

78.

Fisher, H. I., and J. R. Fisher

1972. The Oceanic Distribution of the Laysan Albatross,

Diomedea immutabilis. Wilson Bulletin, 84(l):7-27.

Fisher, H. I., and M. L. Fisher

1969. The Visits of Laysan Albatrosses to the Breeding

Colony. Micronesica, 5(1):17S-221.

Fleming, C. A.

1950. Some South Pacific Sea-bird Logs. Emu, 49 (3): 169-

188.

Fredrich, L. A.

1961. An Occurrence of the Laysan Albatross on the

Northwest Coast of Oregon. Condor, 63 (6) :506.

Friedmann, H., L. Griscom, and R. T. Moore

1950. Distributional Check-list of the Birds of Mexico,

Part 1. Pacific Coast Avifauna, 29:1-202, 2 plates.

Frings, H., and M. Frings

1961. Some Biometric Studies on the Albatrosses of Midway Atoll. Condor, 63(4):304-312.

Gabrielson, I. N., and S. G. Jewett

1940. Birds of Oregon, xxx+650 pages, 1 color plate, 97

photographic plates, 1 map. Corvallis: Oregon State

College.

Gabrielson, I. N., and F. C. Lincoln

1959. The Birds of Alaska, xiii+922 pages, 12 plates.

Washington:Wikllife Management Institute.

Gallagher, M. D.

1960. Bird Notes from Christmas Island. Pacific Ocean.

Ibis, 102(4):489-502.

Gibson, J. D.

1960. Sea-bird Log—Sydney to Cape Town and Panama

to Sydney. Emu, 60(1): 11-19.

Gibson, J. D., and A. R. Sefton.

1956. Red-tailed Tropicbird at Port Kembla, N1W.

Emu, 56(3): 198.

Gilford, E. W.

1913. Expedition of the California Academy of Sciences

to the Galapagos Islands, 1905-1906, VIII: The

Birds of the Galapagos Islands, with Observations

of the Birds of Cocos and Clipperton Islands (Columbiformes to Pelecaniformes). Proceedings of the

California Academy of Sciences, series 4, 2(1): 1-132,

7 plates.

Goddard. M. T., and K. A. Hindwood

1951. Sea-birds and Cyclones: Some Interesting New

South Wales Records. Emu, 51 (2) : 169-171.

Godfrey, W. E.

1966. The Birds of Canada. 428 pages, 69 plates. Ottawa:

National Museum of Canada.

Gould, P. J.

1967. Nocturnal Feeding of Sterna fuscata and Puffinus

pacifxcus. Condor, 69(5):529.

Gould, P. J., and W. B. King

1967. Records of Four Species of Pterodroma from the

Central Pacific Ocean. Auk, 84(4) :591-594.
274 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Grinnell, J., and F. S. Daggett

1903. An Ornithological Visit to Los Coronados Islands,

Lower California. Auk, 20(1) :27-37.

Grinnell, J., and A. H. Miller

1944. Distribution of the Birds of California. Pacific

Coast Avifauna, 27:1-608, 1 plate.

Gross, W. A. O.

1935. The Life History Cycle of Leach's Petrel (Oceanodroma leucorhoa leucorhoa) on the Outer Sea Islands of the Bay of Fundy. Auk, 52 (4) :383-399.

Hachisuka, M., N. Kuroda, N. Kuroda, T. Mishima, H.

Morioka, T. Udagawa, and Y. Yamashina

1958. A Handlist of the Japanese Birds. 4th and revised

edition, 264 pages. Tokyo: Ornithological Society

of Japan.

Hachisuka, M., and T. Udagawa

1951a. Contributions to the Ornithology of Formosa. Quarterly Journal of the Taiwan Museum, 3:187-280.

1951b. Contributions to the Ornithology of Formosa. Quarterly Journal of the Taiwan Museum, 4:1-180.

Hamilton, W. J., Ill

1958. Pelagic Birds Observed on a North Pacific Crossing.

Condor, 60(3): 159-164.

Hanna, G. D.

1926. Expedition to the Revillagigedo Islands, Mexico, in

1925. General Report. Proceedings of the California

Academy of Sciences, series 4, 15(1): 1-113, 10

plates.

Harrison, P. P. O.

1962. Sea Birds of the South Pacific Ocean. 144 pages, 5

plates, 1 map. Narberth: H. G. Walters.

Hindwood, K. A.

1947. Occurrence of the Red-tailed Tropicbird in Southeastern Australia and Tasmania. Emu, 47 (1) :57.

1955. Red-tailed Tropicbird in South-eastern Australia.

Emu, 55:160-161.

Hindwood, K. A., K. Keith, and D. L. Serventy

1963. Birds of the South-West Coral Sea. Division of

Wildlife Research Technical Paper, 3:1-44. Australia: Commonwealth Scientific and Industrial Research Organization.

Holmes, R. T.

1964. Notes on Occurrence of the Laysan Albatross near

the California Coast. Condor, 66 (4) :3O2-3O3.

Howell, A. B.

1920. Habits of Oceanodroma leucorhoa beali Versus O.

socorroensis. Condor, 22(l):41-42.

Hubbs, C. L.

1960. The Marine Vertebrates of the Outer Coast. Systematic Zoology, 9(3-4):134-147.

Huber, L. N.

1971. Notes on Migration of Wilson's Storm Petrel

(Oceanites oceanicus) near Eniwetok Atoll, Western Pacific Ocean. Notornis, 18(l):38-42.

Huey, L. M.

1930. Notes on the Habits and Plumage of Young Kaeding Petrels. Condor, 32(l):68-69.

1952. Oceanodroma tethys tethys, a Petrel New to the

North American Avifauna. Auk, 69(4) :460-461.

Humphrey, P. S.

1965. An Ecological Survey of the Central Pacific. Smithsonian Year 1965: Annual Report of the Smithsonian Institution for the Year Ended June 30,

1965, 24-30. Washington, D.C.

Hundley, M. H.

1962. Galapagos .. . las Islas Encantadas, Part 1. Florida

Naturalist, 35 (4): 109-114.

Huntington, C. E.

1963. Population Dynamics of Leach's Petrel, Oceanodroma leucorhoa. Proceedings of the J3th International Ornithological Congress (Ithaca) 1962:701-

705.

Hutchinson, G. E.

1950. Marginalia: Wideawake Fair. American Scientist,

58:612-619.

Jenkins, J. A. F.

1962. Sooty Tern in New Zealand Waters. Sea Swallow,

15:33-34.

Jespersen, P.

1933. Observations on the Oceanic Birds of the Pacific

and Adjacent Waters. Videnskabelige Meddelelser

Dansk Naturhistorisk Forening, 94:187-221.

Jewett, S. G., W. P. Taylor, W. T. Shaw, and J. W. Aldrich.

1953. Birds of Washington State, xxxii + 767 pages, 12

plates, 1 map. Seattle: University of Washington

Press.

Johnson, A. W.

1965. The Birds of Chile and Adjacent Regions of Argentina, Bolivia, and Peru. Volume I, 398 pages.

Buenos Aires: Platt Establecimiento Graficos S. A.

Johnson, A. W., W. R. Millie, and G. Moffett

1970. Notes on the Birds of Easter Island. Ibis, 112(4):

532-538.

Joint Typhoon Warning Center

1965. Typhoons of the Western North Pacific, 1964. Mariners' Weather Log, 9(3):79-86.

1966. Typhoons of the Western North Pacific, 1965. Mariners' Weather Log, 10(3):73-78.

1967. Typhoons of the Western North Pacific, 1966. Mariners' Weather Log, ll(3):75-82.

Jones, M. E.

1965. Birds Seen during a Voyage from Balboa to Japan

and the East Coast of Malaya. Sea Swallow, 17:66-

72.

Kaeding, H. B.

1905. Birds from the West Coast of Lower California and

Adjacent Islands. Condor, 7(4): 105-111.

Kenyon, K. W.

1950. Distribution of Albatrosses in the North Pacific and

Adjacent Waters. Condor, 52(3):97-103.

Kenyon, K. W., and D. W. Rice

1958. Homing of Laysan Albatrosses. Condor, 60 (1) :3-6.

King, J. E., and R. L. Pyle

1957. Observations of Sea Birds in the Tropical Pacific.

Condor, 59 (1) :27-39.

King, W. B.

1967. Seabirds of the Tropical Pacific Ocean: Preliminary Smithsonian Identification Manual, xxxii+126

pages, 11 plates. Washington: Smithsonian Institution.
NUMBER 158 275

1970. The Trade Wind Zone Oceanography Pilot Study,

Part VII: Seabird Observations March 1964 to June

1965. United States Department of Interior Special

Scientific Report—Fisheries, 586:vi+136 pages.

King, W. B., and P. J. Gould

1967. The Status of Newell's Race of the Manx Shearwater. The Living Bird, 6:163-186,

King, W. B., G. E. Watson, and P. J. Gould

1967. An Application of Automatic Data Processing to

the Study of Seabirds, I: Numerical Coding. Proceedings of the United States National Museum,

123(8609): 1-29.

Kuroda, N.

1954. On the Classification and Phytogeny of the Order

Tubinares, Particularly the Shearwaters (Puffinus).

179 pages. Tokyo: Herald Company, Limited.

1955. Observations of Pelagic Birds of the Northwest Pacific. Condor, 57 <5):29O-3OO.

1960. Analysis of Sea Bird Distribution in the Northwest

Pacific Ocean. Pacific Science, 14 (1) :55-67.

1963. A Winter Sea-bird Census between Tokyo and

Kushiro, Hokkaido. Miscellaneous Report of the

Yamashina Institute for Ornithology and Zoology,

3 (4) :227-238.

Laird, M.

1951. Notes on the Birds Observed During a TransPacific Sea Voyage. Emu, 50(3): 175-178.

Lane, S. G.

1967. Sooty Tern Recovery in the Philippines. Australian

Bird Bander, 5 (3) :57.

La Touche, J. D. D.

1934. A Handbook of the Birds of Eastern China. Volume

2, part 5: 401-496, 2 plates. London: Taylor and

Francis.

Leveque, R.

1964a. Notes sur la Reproduction des Oiseaux aux lies

Galapagos. Alauda, 32(l):5-44, (2) :81-96.

1964b. Notes on Ecuadorian Birds. Ibis, 106 (1) :52-62.

Leveque, R., R. I. Bowman, and S. L. Billeb

1966. Migrants in the Galapagos Area. Condor, 68 (1) :81-

101.

Loomis, L. M.

1918. A Review of the Albatrosses, Petrels, and Diving

Petrels. Proceedings of the California Academy of

Sciences, series 4, 2(2): 1-187, 17 plates.

MacDonald, J. D., and P. A. Lawford

1954. Sight Records of Birds in the Pacific Compiled from

the Bird Log Kept during the Recent Cruises of the

H.M.S. Challenger. Emu, 54(l):7-28.

Martin, E. W.

1938. The Petrels of Castle Rock, Del Norte County,

California. Condor, 40 (6) :260.

Martin, P. W.

1942. Notes on Some Pelagic Birds of the Coast of British

Columbia. Condor, 44(l):27-29.

Mathews, G. M., and T. Iredale

1921. A Manual of the Birds of Australia. Volume 1,

xxiv+279 pages, 36 plates. London: H. F. and G.

Witherby.

Maya, J. A.

1969. The Natural History of the Fish-eating Bat, Pizonyx vivesi. Unpublished Ph.D. dissertation, University of Arizona, Tucson, Arizona.

McAllister, T.

1954. The Laysan Albatross (Diomedea immutabilis) on

the Oregon Coast. Auk, 71 (2) :211.

McHugh, J. L.

1950. Increasing Abundance of Albatrosses off the Coast

of California. Condor, 52(4): 153-156.

1955. Distribution of Black-footed Albatrosses, Diomedea

nigripes, off the West Coast of North America,

1949 and 1950. Pacific Science, 9(4) :375-381.

McLellan, M. E.

1926. Expedition to the Revillagigedo Islands, Mexico, in

1925, VI: The Birds and Mammals. Proceedings of

the California Academy of Sciences, scries 4, 15(11):

279-322.

Miller, L.

1940. Observations of the Black-footed Albatross. Condor,

42(5):229-238.

1942. Some Tagging Experiments with Black-footed Albatrosses. Condor, 44 (1) :3-9.

Millie, W. R.

1963. Brief Notes on the Birds of San Ambrosio and San

Felix Islands, Chile. Ibis, 105 (4) :563-566.

Moffitt, J.

1938. Two Southern Petrels in the North Pacific. Auk,

55(2):255-259.

Morzer Bruyns, W. F. J.

1965. Birds Seen during West to East Trans-Pacific Crossing along Equatorial Counter-current around Latitude 7°N, in the Autumn of 1960. Sea Swallow, 17:

57-66.

Morzer Bruyns, W. F. J., and K. H. Voous

1965. Night Feeding by Sooty Tern (Sterna fuscata).

Ardea, 53 (1-2) :79.

Motoda, S., and T. Fujii

1956. Report from the "Oshoro Mara" on Oceanographic

and Biological Investigations in the Bering Sea and

Northern North Pacific in the Summer of 1955.

Hokkaido University Faculty of Fisheries Bulletin,

6(4) :280-297.

Murie, O. J.

1959. Fauna of the Aleutian Islands and Alaska Peninsula. United States Department of Interior, Fish

and Wildlife Service. North American Fauna, 66:

xiv+406 pages.

Muromtzev, A. M.

1958. [The Principal Hydrological Features of the Pacific

Ocean.] 417 pages. Jerusalem: Israel Program for

Scientific Translations [1963]. [Translated from

Russian.]

Murphy, R. C.

1924. Birds Collected During the Whitney South Sea Expedition, II. American Museum Novitates, 124:1-13.

1936. Oceanic Birds of South America. 2 volumes, 1245

pages, 72 plates, 15 colored plates. New York:

American Museum of Natural History.

1951. The Populations of the Wedge-tailed Shearwater
276

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

(Puffinus pacificus). American Museum Novitates,

1512:1-21.

1958. The Vertebrates of "Scope". (November 7-December 16, 1956). United States Department of Interior

Special Scientific Report—Fisheries, 279:101-111.

Murphy, R. C, and J. P. Snyder

1952. The "Pealea" Phenomenon and Other Notes on

Storm Petrels. American Museum Novitates, 1596:

1-16.

Nakamura, T.

1963. Distribution of the Black-footed Albatross (Diomedea nigripes) in the North Pacific Ocean. Miscellaneous Report of the Yamashina Institute for

Ornithology and Zoology, 3 (4) :2S9-246.

Nelson, B.

1968. Galapagos: Islands of Birds, xx+338 pages, 57

photographs, 1 map. London: Longmans, Green and

Company, Limited.

Nisbet, I. C. T., and R. G. McCaskie

1960. Wilson Petrel off the California Coast. Condor,

62(2): 141.

Norris, A. Y.

1967. Seabird Observations from the South-west Pacific in

the Southern Winter. Emu, 67 (1-2) :33-55.

Oliver, W. R. B.

1955. New Zealand Birds. 2nd edition, 661 pages, 12

plates. Wellington: A. H. and A. W. Reed.

Orr, R. T.

1944. The Nesting Season of the Ashy Petrel. Condor,

46(3): 125-126.

Osborn, P. I.

1911. Collecting Socorro and Black Petrels in Lower

California. Condor, 13(1):31-S4.

Palmer, R. S., editor

1962. Handbook of North American Birds. Volume 1.

vii+567 pages, 7 plates. New Haven: Yale University Press.

Peakall, D. B.

1960. Ocean Transit, California to Capetown via Australia. Emu, 60(3): 197-202.

POBSP (Pacific Ocean Biological Survey Program)

1963-1969. Unpublished reports and field notes. 96 volumes. Department of Vertebrate Zoology, National

Museum of Natural History, Smithsonian Institution, Washington, D.C.

Poole. F.

1966. Birds of the North Pacific Sea Swallow, 18:71-74.

Powell, D. E., D. L. Alverson, and R. Livingstone, Jr.

1952. North Pacific Albacore Tuna Exploration . . . 1950.

United States Department of Interior, Fish and

Wildlife Service, Fisheries Leaflet, 402:1-56.

Rand, A. L., and E. T. Gilliard

1967. Handbook of New Guinea Birds, x + 628 pages, 76

illustrations, 5 plates. London: Weidenfeld and

Nicolson.

Reid, J. L., G. I. Roden, and J. G. Wyllie

1958. Studies of the California Current System. Pages 27-

57 in Progress Report, 1 July 1956 to 1 January

1958. California Cooperative Oceanic Fisheries Investigations.

Rice. D. W., and K. W. Kenyon

1962a. Breeding Distribution, History and Populations of

North Pacific Albatrosses. Auk, 79 (3) :365-S86.

1962b. Breeding Cycles and Behavior of Laysan and Blackfooted Albatrosses. Auk, 79(4) :517-567.

Richardson, F.

1957. The Breeding Cycles of Hawaiian Sea Birds. Bernice

P. Bishop Museum Bulletin, 218:1-41.

Riehl, H.

1954. Tropical Meteorology, x+392 pages. New York:

McGraw-Hill Book Company.

Robbins, C. S.

1966. Birds and Aircraft on Midway Islands: 1959-63 Investigations. United States Department of Interior,

Special Scientific Report—Wildlife, 85:1-63.

Rothschild, B. J., and R. N. Uchida

1968. The Tuna Resources of the Oceanic Regions of the

Pacific Ocean. In D. Gilbert, editor, The Future of

the Fishing Industry of the United States. University

of Washington Publications in Fisheries, new series,

4:19-51.

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 the Area.

Murrelet, 46(1): 1-6.

1970. The Seasonal Distribution of Some Seabirds off

Washington and Oregon with Notes on Their

Ecology and Behavior. Condor, 72(3):339-S57.

1972. The Recent Pelagic Status of the Short-tailed Albatross (Diomedea albatrus). Biological Conservation,

4(3):189-193.

Schreiber, R. W., and N. P. Ashmole

1970. Sea Bird Breeding Seasons on Christmas Island, Pacific Ocean. Ibis, 112(3):363-394.

Seckel, G. R.

1962. Atlas of the Oceanographic Climate of the Hawaiian Islands Region. United States Fish and Wildlife Service, Fisheries Bulletin, 193(61):371-427.

1970. The Trade Wind Zone Oceanography Program,

Part VIII: Sea-level Meteorological Properties and

Heat Exchange Processes, July 1963 to June 1965.

United States Department of Interior, Special Scientific Report—Fisheries, 612: iv+129.

Sette, O. E.

1955. Consideration of Midocean Fish Production as Related to Oceanic Circulatory Systems. Sears Foundation, Journal of Marine Research, 14 (4) :398-414.

Shelton, P. S.

In prep. The Natural History of Johnston Atoll, Central

Pacific Ocean. Atoll Research Bulletin.

Shuntov, V. P.

1968. Some Regularities in Distribution of Albatrosses

(Tubinares, Diomedeidae) in the Northern Pacific.

Zoologicheski Zhurnal, 47(7): 1054-1064. [In Russian

with English summary.]

Sincock, J. L., and G. E. Swedberg

1969. Rediscovery of the Nesting Grounds of Newell's

Manx Shearwater {Puffinus puffinus newelli), with

Initial Observations. Condor, 71 (1) :69-71.
NUMBER 158 277

Slud, P.

1964. The Birds of Costa Rica. American Museum of

Natural History Bulletin, 128:1-430, 2 plates, 1

map.

Sorensen, J. H.

1964. Birds of the Kermadec Islands. Notornis, 11(2) :69-

81.

Stager, K. E.

1958. A Record of the Laysan Albatross from Southern

California. Condor, 60 (6) :404-405.

1964. The Birds of Clipperton Island, Eastern Pacific.

Condor, 66(5): 357-371.

Starrett, W. C, and K. L. Dixon

1946. The Scarcity of the Black-footed Albatross in Parts

of Its Known Range. Condor, 48(6):268-271.

Storer, R. W.

1960. Evolution in the Diving Birds. Proceedings of the

12th International Ornithological Congress (Helsinki), 1958:694-707.

Sverdrup, H. U., M. W. Johnston, and R. H. Fleming

1942. The Oceans, Their Physics, Chemistry, and General

Biology. x+1087 pages, 7 charts. New York: PrenticeHall, Incorporated.

Szijj, L. J.

1967. Notes on the Winter Distribution of Birds in the

Western Antarctic and Adjacent Pacific Waters.

Auk, 84 (3) :366-378.

Thompson, D. Q.

1951. Notes on Distribution of North Pacific Albatrosses.

Auk, 68(2):227-235.

United States Naval Oceanographic Office

1964. Sailing Directions for the Pacific Islands, Volume 1.

Hydrographic Office Publication, number 82, 2nd

edition, xv + 453 pages, 1 chart.

United States Navy

1956. U. S. Navy Marine Climatic Atlas of the World,

Volume II: North Pacific Ocean. NAVAER 50-IC529. xviii + 275 charts.

Vaurie, C.

1965. The Birds of the Palearctic Fauna. (Non-Passeriformes). xx + 763 pages. London: H. F. and G.

Witherby, Limited.

Watson, J. B.

1908. The Behavior of Noddy and Sooty Terns. Carnegie

Institution of Washington Publication 103, Tortugas Laboratory Paper, 2:187-255.

Watson, J. B., and K. S. Lashley

1915. An Historical and Experimental Study of Homing.

Carnegie Institution of Washington Publication

211, Department of Marine Biology Paper, 7:7-60.

Wetmore, A.

1965. The Birds of the Republic of Panama, Part I—

Tinamidae (Tinamous) to Rynchopidae (Skimmers). Smithsonian Miscellaneous Collections, 150:

iv + 483, 1 plate.

Wilbur, H. M.

1969. The Breeding Biology of Leach's Petrel, Oceanodroma leucorhoa. Auk, 86(3) :433-442.

Wilhoft, D. C.

1961. Birds Observed during Two Crossings of the Pacific

Ocean. Condor, 63 (3) :257-262.

Willett, G.

1915. Summer Birds of Forrester Island, Alaska. Auk,

32(3):295-305.

1919. Notes on the Nesting of Two Little-known Species

of Petrel. Condor, 21 (2) :60-61.

Wyrtki, K.

1966. Oceanography of the Eastern Equatorial Pacific

Ocean. Oceanography and Marine Biology, 4:33-36.

N.D. Summary of the Physical Oceanography of the

Eastern Pacific Ocean. University of California Institute of Marine Resources. I.M.R. reference 65-10,

UCSD-34:99-lll.

Yamashina, Y.

1942. Birds of the Seven Islands of Izu. Tori, 11(53-54):

191-270.

Yocom, C.

1947. Notes on Behavior and Abundance of the Blackfooted Albatrosses in the Pacific Waters off the Continental North American Shores. Auk, 64(4):507-523.

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