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Bureau of Land Management
Fish and Wildlife Service
U.S. Department of the Interior

FRED E. LOHRER
ARCHBOLD BIOLOGICAL STAiOIN
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FWS/OBS-82/01
March 1982

MARINE BIRDS OF THE SOUTHEASTERN UNITED STATES
AND GULF OF MEXICO

PART I

GAVIIFORMES through PELECANIFORMES

by

Roger B. Clapp, Richard C. Banks
Deborah Morgan-Jacobs, and Wayne A. Hoffman

Museum Section
United States Fish and Wildlife Service
National Museum of Natural History
Washington, D.C. 20560

Contract No. 14-16-0009-78-917

Project Officers
Cherry Keller/Robin White
National Coastal Ecosystems Team
United States Fish and Wildlife Service
NASA-Slidell Computer Complex
1010 Gause Boulevard
Slidell, Louisiana 70458

This project was sponsored by the
Bureau of Land Management

Prepared for
Coastal Ecosystems Project
Office of Biological Services
U.S. Department of the Interior
Washington, D.C. 20240

The correct citation for this report is:

Clapp, R.B., R.C. Banks, D. Morgan-Jacobs and W.A. Hoffman. 1982. Marine
birds of the Southeastern United States and Gulf of Mexico. Part I.
Gaviiformes through Pelecaniformes. U.S. Fish and Wildlife Service, Office
of Biological Services, Washington, D.C. FWS/OBS-82/01. 637 pp.

PREFACE

Part I of the Marine Birds of the Coastal Southeastern United States is
published by the National Coastal Ecosystems Team to provide a synthesis and
analysis of information about marine birds in this area. Accounts for 39 spe-
cies include information on distribution, abundance, food habits, breeding
ecology, and susceptibility to oil pollution. Selected bibliographies follow
each species account and list additional sources of information.

Any suggestions or questions regarding this report should be directed to:

Information Transfer Specialist
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
NASA-Slidell Computer Complex
1010 Cause Boulevard
Slidell, Louisiana 70458

ABSTRACT

Information on the seasonal distribution and abundance of 39 species of
marine birds of the Orders Gaviiformes, Podicipediformes, Procellariiformes,
and Pelecaniformes that occur off the southeastern shores of the United States
and in the Gulf of Mexico has been compiled and mapped from thousands of
literature citations; in many instances this provides the first synthesis of
knowledge about a species for this area. Information on world-wide distribu-
tion, habitat, food, and various aspects of life history is also summarized.
This information was gathered to assess the possible effects of offshore oil
development on populations of marine birds.

Susceptibility of birds to oil depends not only on their juxtaposition in
time and space, but also on currents, climatic factors, the stage in the life
or annual cycle, and the behavior of the species. Contamination by oil may
result in matted feathers; death may soon follow from chilling or starvation,
or from the toxic effects of oil ingested when the birds attempt to preen
themselves. Oil from feathers may be transferred to eggs by incubating birds
and may greatly reduce reproductive success.

Among the birds covered by this volume, loons and grebes are considered
the most susceptible to oil pollution. Cormorants, pelicans, and boobies are
moderately susceptible and the truly pelagic birds, including most of the
Procellariiformes, are the least susceptible.

Little is known about the occurrence of seabirds off our shores, but our
knowledge is increasing. Recent ornithological studies offshore have revealed
concentrations of species previously thought to occur rarely, if at all. More
than 63% of the Manx Shearwaters ever seen off the southeastern coast were
sighted in the last 5 years (1975-1979) and 37% were seen during the last 2
years (1978-1979) covered by this report. Comparable figures for Wilson's
Storm-petrel are 40% and 26%. Nontheless, observations are limited. Future
trips to locate or count birds should be scheduled when birds are expected to
be present at periods when little previous information was obtained.

Additional research should be conducted on the distribution and status of
birds that use the marine environment. More attention should be directed
toward investigating the status and distribution of pelagic birds, toward
learning the abundance and distribution of marine birds that nest in the
southeastern states, and toward discovering the distribution and status of
birds that are transients or winter visitors in the southeast. Research is
also needed to determine the numbers and proportion of each species that are
being oiled in the southeast so that the effects of oil pollution can be
assessed more adequately.

CONTENTS

Page

PREPACE . . . . . . . . . . . . . . . . 1

ABSTRACT . . . . . . . . . . . . . . . . ii

MAPS . . . . . . . . . . . . . . . . . vii

TABLES . . . . . . . . . . . . . . . . viii

PURPOSE OF REPORT . . . . . . . . . . . . . 1

STUDY %IEA . . . . . . . . . . . . . . . 1

Habitats . .. . . . . . . . . . 1
Climates . . . . . . . . . . . . . . . 3

METHODS . . . . . . . . . . . . . . . . 4

ARRANGEMENT AND CONTENT OF SPECIES ACCOUNTS . . . . . . . 7

Abbreviations . . . . . . . . . . . . . 7
Species Included . . . . . . . . . . . . . 8
Scientific and Vernacular Names . . . . . . . . . 9
General Distribution . . . . . . . . . . . . 10
Distribution in the Coastal Southeastern United States . . . 10
Synopsis of Present Distribution and Abundance . . . . . 13
Habitat . . . . . . . . . . . . . . . 13
Food and Feeding Behavior . . . . . . . . . . 14
Important Biological Parameters . . . . . . . . . 15
Susceptibility to Oil Pollution . . . . . . . . . 16
Species Bibliography . . . . . . . . . . . . 17

OIL POLLUTION AND MARINE BIRDS OF THE SOUTHEASTERN UNITED STATES . . 18

Variability in Species' Susceptibility to Oil Pollution . . . 19
Regional Differences in Oiling and Mortality of Beached Birds . 19
Major Bird kills Following Oil Spills in the Southeastern U.S. . 22
Sources of Variation in Mortality from Oil Pollution . . . . 22
Effects of Oil on Contaminated Birds and Their Eggs . . . . 24
Potential Hazards to Marine Birds from Offshore Oil Production . 25

RECOMMENDATIONS FOR FUTURE RESEARCH . . . . . . . . . 26

Status and Biology of Breeding Species . . . . . . . 26
Distribution and Status of Pelagic Species . . . . . . 27
Distribution and Status of Transient and Wintering Inshore Species 32
Research Needed on Effects of Oil on Southeastern Marine Birds . 33

ACKNOWLEDGMENTS . . . . . . . . . . . . . . 35

Page

SPECIES ACCOUNTS . . . . . . . . . . . . . . 37

GAVIIFORMES

Gaviidae

Red-throated Loon (Gavia stellata) . . . . account . . 37
bibliography . 43

Arctic Loon (Gavia arctica) . . . . . . account . . 48
bibliography . 51

Common Loon (Gavia immer) . . . . . . account . . 58
bibliography . 65

PODICIPEDIFORMES

Podicipedidae

Least Grebe (Tachybaptus dominicus) . . . . account . . 73
bibliography . 75

Pied-billed Grebe (Podilymbus podiceps) . . . account . . 77
bibliography . 84

Horned Grebe (Podiceps auritus) . . . . . account . . 88
bibliography . 99

Red-necked Grebe (Podiceps grisegena) . . . account . . 105
bibliography . 110

Eared Grebe (Podiceps nigricollis) . . . . account . . 118
bibliography . 129

Western Grebe (Aechmophorus occidentalis) . . account . . 137
bibliography . 143

PROCELLARIIFORMES

Diomedeidae

Black-browed Albatross (Diomedea melanophrys) . account . . 148
bibliography . 149

Yellow-nosed Albatross (Diomedea chrysostoma) . account . . 153
bibliography . 154

Procellariidae

Northern Fulmar (Fulmarus glacialis) . . . account . . 157
bibliography . 160

iv

Number Page

16 Dates of occurrence for Western Grebes in the coastal south-
eastern United States. . . . . . . . . . . .. 140

17 Number of dead birds and number and percentage of dead Northern
Fulmars found after major oiling incidents . . . . . . 159

18 Approximate number of Cory's Shearwaters recorded by month for
the coastal southeastern United States. . . . . . . ... 192

19 Dates of occurrence for Cory's Shearwaters in the coastal south-
eastern United States. . . . . . . . . . . . 192

20 Approximate number of Greater Shearwaters recorded by month for
the coastal southeastern United States. . . . . . . ... 202

21 Approximate number of Sooty Shearwaters recorded by month for
the coastal southeastern United States. . . . . . . ... 228

22 Dates of occurrence for Sooty Shearwaters in the coastal south-
eastern United States. . . . . . . . . . . .. 229

23 Weights of Sooty Shearwaters (in grams) . . . . . . . 232

24 Approximate number of Audubon's Shearwaters recorded by month
in the coastal southeastern United States . . . . . . . 264

25 Dates of occurrence for Audubon's Shearwaters in the coastal
southeastern United States. . . . . . . . . . .. 265

26 Hatching success in Audubon's Shearwaters in the Galapagos
Islands. . . . . . . . . . . . . . . .. 267

27 Weights of Audubon's Shearwaters (in grams). . . . . . ... 268

28 Approximate number of Wilson's Storm-Petrels recorded by month
for the coastal southeastern United States. . . . . . ... 287

29 Dates of occurrence for Wilson's Storm-Petrels in the coastal
southeastern United States. . . . . . . . . . .. 288

30 Weights of Wilson's Storm-Petrels (in grams). . . . . . ... 292

31 Approximate number of Leach's Storm-Petrels recorded by month
for the coastal southeastern United States. . . . . . ... 313

32 Weights of Leach's Storm-Petrels (in grams). . . . . . ... 317

33 Dates of occurrence for White-tailed Tropicbirds in the coastal
southeastern United States. . . . . . . . . . .. 340

Trindade Petrel (Pterodroma arminjoniana) .

Cahow (Pterodroma cahow) . . . . .

Black-capped Petrel (Pterodroma hasitata) .

Bulwer's Petrel (Bulweria bulwerii) . . .

Cory's Shearwater (Calonectris diomedea) .

Greater Shearwater (Puffinus gravis) . .

Sooty Shearwater (Puffinus griseus) . . .

Manx Shearwater (Puffinus puffinus) . . .

Audubon's Shearwater (Puffinus iherminieri) .

Little Shearwater (Puffinus assimilis) . .

Hydrobatidae

Wilson's Storm-Petrel (Oceanites oceanicus) .

White-faced Storm-Petrel (Pelagodroma marina)

Harcourt's Storm-Petrel (Oceanodroma castro)

Leach's Storm-Petrel (Oceanodroma leucorhoa)

PELECANIFORMES

Phaethontidae

Red-billed Tropicbird (Phaethon aethereus)

. . account .
bibliography

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bibliography

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bibliography

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bibliography

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bibliography

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bibliography

Page

170
171

173
174

177
179

181
182

184
195

201
214

220
233

239
244

254
269

273
274

277
293

298
299

303
305

307
318

. . account . . 328
bibliography . 330

White-tailed Tropicbird (Phaethon lepturus) . .

Fregatidae

Magnificent Frigatebird (Fregata magnificent) . .

Phalacrocoracidae

Great Cormorant (Phalacrocorax carbo) . . . .

Double-crested Cormorant (Phalacrocorax auritus). .

Olivaceous Cormorant (Phalacrocorax olivaceus). .

Sulidae

Northern Gannet (Sula bassana) . . . . .

Blue-footed Booby (Sula nebouxii) . . . . .

Blue-faced Booby (Sula dactylatra) . . . .

Red-footed Booby (Sula sula) . . . . . .

Brown Booby (Sula leucogaster) . . . . .

Pelecanidae

American White Pelican (Pelecanus erythrorhynchos).

Brown Pelican (Pelecanus occidentalis) . . .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

account . .
bibliography .

LITERATURE CITED . ..

Page

333
344

349
365

372
381

395
411

422
429

432
445

457
459

461
478

481
485

490
502

507
525

539
558

573

MAPS

Number Page

1 Winter Distribution Map for the Red-throated Loon . . . . 38

2 Winter Distribution Map for the Common Loon . . . . . . 59

3 Winter Distribution Map for the Pied-billed Grebe . . . . 79

4 Winter Distribution Map for the Horned Grebe . . . . . 89

5 Winter Distribution Map for the Eared Grebe . . . . . . 119

6 Breeding Range Map for the White Pelican and the
Magnificent Frigatebird . . . . . . . . . . 355

7 Winter Distribution Map for the Magnificent Frigatebird . . . 358

8 Winter Distribution Map for the Great Cormorant . . . . . 378

9 Breeding Range Map for the Double-crested Cormorant and
the Olivaceous Cormorant . . . . . . . . . . 396

10 Winter Distribution Map for the Double-crested Cormorant . . 398

11 Winter Distribution Map for the Olivaceous Cormorant . . . 425

12 Winter Distribution Map for the White Pelican . . . . . 513

13 Breeding Range Map for the Brown Pelican . . . . . . 541

14 Winter Distribution Map for the Brown Pelican . . . . . 542

vii

TABLES

Number Page

1 Number and percentage of beached birds examined and oiled . . . 20

2 Comparison of regional and seasonal variation of beached bird
mortality and incidence of oiling in the eastern United States . 21

3 Approximate percentage of all individuals of ten species of
pelagic seabirds ever recorded in the southeastern United States
from 1975 to 1979 and from 1978 to 1979 . . . . . . . 28

4 Apparent status of some pelagic seabirds in three Atlantic coast
states . . . . . . . . . . . . . . . 29

5 Number of dead birds and number and percentage of dead Red-throated
Loons found after major oiling incidents . . . . . . . 42

6 Number of dead birds and number and percentage of dead Arctic Loons
found after major oiling incidents. . . . . . . . ... 50

7 Number of dead birds and number and percentage of dead Common Loons
found after major oiling incidents. . . . . . . . ... 64

8 Peak concentrations of migrant and wintering Horned Grebes in
the coastal southeastern United States. . . . . . . ... 91

9 Dates of occurrence for Horned Grebes in the coastal south-
eastern United States, exclusive of sightings attributed to
summering birds. . . . . . . . . . . . . .. 93

10 Number of dead birds and number and percentage of dead Horned Grebes
found after major oiling incidents. . . . . . . . .. 98

11 Dates of occurrence for Red-necked Grebes in the coastal south-
eastern United States. . . . . . . . . . . .. 107

12 Number of dead birds and number and percentage of dead Red-necked
Grebes found after major oiling incidents . . . . . . . 111

13 Dates of occurrence for Eared Grebes in the coastal southeastern
United States. . . . . . . . . . . . . .. 125

14 Peak concentrations of wintering Eared Grebes in states bordering
the northwestern Gulf of Mexico. . . . . . . . . .. 125

15 Number of dead birds and number and percentage of dead Eared Grebes
found after major oiling incidents. . . . . . . . ... 129

viii

Number Page

34 Approximate number of White-tailed Tropicbirds recorded by month
for the coastal southeastern United States. . . . . . ... 340

35 Weights of White-tailed Tropicbirds (in grams). . . . . ... 344

36 Observations on breeding by Magnificent Frigatebirds at the
Marquesas Keys, 1969-1979. . . . . . . . . . . .. 356

37 Peak concentrations of Magnificent Frigatebirds in states
bordering the Gulf of Mexico. . . . . . . . . . .. 359

38 Dates of occurrence for Magnificent Frigatebirds in the coastal
southeastern United States. . . . . . . . . . .. 361

39 Approximate number of Magnificent Frigatebirds recorded by
month from North Carolina to Georgia. . . . . . . . ... 362

40 Approximate number of Great Cormorants recorded by month for
the coastal southeastern United States. . . . . . . ... 377

41 Dates of occurrence for Great Cormorants in the coastal south-
eastern United States. . . . . . . . . . . .. 379

42 Number of dead birds and number and percentage of dead Great
Cormorants found after major oiling incidents . . . . . . 382

43 Peak concentrations of wintering and migrant Double-crested
Cormorants in the coastal southeastern United States. . . . ... 400

44 Breeding population estimates for the Double-crested Cormorant. . 402

45 Weights of Double-crested Cormorants (in grams). . . . . ... 410

46 Winter concentrations of Olivaceous Cormorants recorded in
Texas. . . . . . . . . . . . . . . .. 424

47 Peak concentrations of wintering and migrant Northern Gannets
in North Carolina. . . . . . . . . . . . .. 433

48 Peak concentrations of wintering and migrant Northern Gannets
in South Carolina. . . . . . . . . . . . .. 434

49 Peak concentrations of wintering and migrant Northern Gannets
in Georgia. . . . . . . . . . . . . . .. 434

50 Peak concentrations of wintering and migrant Northern Gannets
on the Florida Atlantic Coast. . . . . . . . . .. 435

51 Peak concentrations of wintering and migrant Northern Gannets
in the Florida Keys. . . . . . . . . . . . .. 435

x

Number Page

52 Peak concentrations of wintering and migrant Northern Gannets
on the Florida Gulf Coast. . . . . . . . . . .. 436

53 Peak concentrations of wintering and migrant Northern Gannets
in Alabama. . . . . . . . . . . . . . .. 437

54 Peak concentrations of wintering and migrant Northern Gannets
in Mississippi. . . . . . . . . . . . . . 437

55 Peak concentrations of wintering and migrant Northern Gannets
in Texas. . . . . . . . . . . . . . . . 438

56 Location and size of colonies of the Northern Gannet. . . . ... 439

57 Dates of occurrence for Northern Gannets in the coastal south-
eastern United States. . . . . . . . . . . . 440

58 Weights of Northern Gannets (in grams). . . . . . . ... 444

59 Reports of oiled Northern Gannets from the southeastern United
States. . . . . . . . . . . . . . . .. 445

60 Approximate number of Blue-faced Boobies recorded by month for
the coastal southeastern United States. . . . . . . ... 471

61 Dates of occurrence for Blue-faced Boobies in the coastal south-
eastern United States. . . . . . . . . . . .. 472

62 Mean clutch size of the Blue-faced Booby. . . . . . . ... 474

63 Weights of Blue-faced Boobies (in grams). . . . . . . ... 477

64 Approximate number of Brown Boobies recorded by month for the
coastal southeastern United States. . . . . . . . .. 499

65 Dates of occurrence for Brown Boobies in the coastal south-
eastern United States. . . . . . . . . . . . 500

66 Breeding population estimates for the American White Pelican. .. . 515

67 Peak concentrations of wintering, migrant, and nonbreeding
American White Pelicans in the coastal southeastern United
States. . . . . . . . . . . . . . . .. 518

68 Peak concentrations of nonbreeding Brown Pelicans in the coastal
southeastern United States. . . . . . . . . . .. 548

69 Productivity (young/nest) in the Brown Pelican. . . . . ... 555

70 Weights of Brown Pelicans (in grams). . . . . . . . ... 557

xi

PURPOSE OF REPORT

The purpose of this report is to summarize the status of marine birds in
the southeastern United States and explore the potential effects on these spe-
cies of the development of petroleum resources on the outer continental shelf
(OCS). This entailed a review of available information to:

1) determine where and when marine birds would most likely occur in areas to
be developed for oil and gas production;

2) ascertain which species would be most at risk from oil and ancillary activ-
ities related to the development of oil resources;

3) evaluate the importance of populations in the southeastern United States
in relation to the entire distribution and abundance of the species; and

4) summarize information on the life history of each species, emphasizing
data obtained in the southeast.

This material is presented in a form that enables the Bureau of Land
Management (BLM) to identify aspects of OCS development that might threaten
populations of marine birds and provides information that will allow managers
to make decisions that minimize damage to these populations during the devel-
opment of energy resources.

A corollary objective is to recommend topics for future research in areas
for which information is particularly weak.

STUDY AREA

The study area includes the coastal and offshore waters of the southeast-
ern United States, from the northern border of North Carolina to the border
of Mexico. A wide variety of coastal habitats occurs within this area. Among
them are sandy barrier islands, fresh, salt, and brackish marshes, open beach,
coastal bays, dredge spoil islands, mud-flats, and mangrove islands. The dom-
inant habitats of sections of the coastline will be discussed below.

HABITATS

North Carolina is dominated by a series of fringing barrier beaches be-
hind which lie large estuaries with extensive areas of shallow water and salt
marsh. These fringing islands, called the Outer Banks, are some 20-30 mi
(30-50 km) farther from the mainland than are such islands along other areas
of the Atlantic coast (Warinner et al. 1976). Extensive stands of salt marsh
with deep tidal channels are found south of Cape Lookout, North Carolina,
through South Carolina and Georgia. Almost three-quarters of the salt marsh
acreage along the Atlantic seaboard is found in these three states. The
largest areas of salt marsh on the Atlantic coast are in Georgia which has

193,000 ha (about 477,000 ac), North Carolina with 64,000 ha (158,000 ac), and
South Carolina with 176,000 ha (435,000 ac)(West 1977).

Barrier islands are also very important coastal habitat in these three
states. The land areas of the barrier islands for each state are 120,000 ac
(48,000 ha) in North Carolina, 124,000 ac (49,600 ha) in South Carolina, and
153,000 ac (61,200 ha) in Georgia (Warner 1976) for a total of about 380,000
ac (152,000 ha). The area of water behind these islands becomes smaller to
the south (Warinner et al. 1976). These three states (North Carolina, South
Carolina, and Georgia) respectively have about 266 mi (428 km), 199 mi (192
km), and 98 mi (158 km) of open beach along their barrier islands. In other
parts of the study area (e.g., parts of the Florida Gulf coast) beaches are
few or nonexistent (Woolfenden and Schreiber 1973).

The east coast of Florida is also dominated by a chain of barrier islands
occasionally broken by tidal passes. Typically, these islands are sandy along
their outer perimeters. Large areas of marsh and estuarine swamp lie landward
of these islands (Warinner et al. 1976) and salt marshes gradually give way
to mangrove swamp (Reimold 1977). Much of the Gulf coast of Florida is domi-
nated by salt marshes and mangrove swamps (Warinner et al. 1976). Open beach
is often extensive from Naples on the Florida peninsula north along the pan-
handle to Alabama (Woolfenden and Schreiber 1973). In Alabama, tidal salt
marsh, sandy beaches, and offshore islands are common coastal landforms. Mis-
sissippi's gulfward border consists almost entirely of barrier islands that
have salt marshes in their centers. The shoreline of Mississippi has had
much development of real estate but still contains fresh, salt, and brackish
marshes (Warinner et al. 1976). Only a limited extent of salt marsh is found
from northern Florida to Mississippi. Most marshes are small, disjunct, and
in alluvial pockets protected by bay shores (West 1977).

Louisiana has more marsh and estuarine area than any of the other United
States except Alaska (Warinner et al. 1976) (more than 40% of the coastal wet-
lands in the contiguous United States; Turner and Gosselink 1975). In some
places the marshes extend inland as much as 40-50 km (25-30 mi) (West 1977).
The coastline along the western third of the state is sandy, but the rest of
the area is dominated by barrier islands and marsh that are strongly influ-
enced by the enormous amounts of mud and silt deposited by the Mississippi
River (Warinner et al. 1976). The Louisiana coast is one of the most produc-
tive areas for marine birds in the continental United States and supports
enormous wintering populations of waterfowl.

The coast of Texas makes up a large share of the western shore of the
Gulf of Mexico. Sandy beaches and offshore barrier islands are abundant.
Two semi-landlocked lagoons, the Upper and Lower Laguna Madre, and a large
low-salinity estuary, Sabine Lake, are areas of great importance to wintering
waterfowl. An estimated 78% of the world's population of Redhead ducks win-
ters in the Laguna Madre and 13% of the world's shrimp harvest comes from
Texas waters (Warinner et al. 1976). A limited amount of salt marsh is
present along bay shores enclosed by offshore bars (West 1977).

CLIMATES

The climatic regime, like the landforms, differs widely from one part of
the study area to another. The northeastern portion is the coldest. The low-
est midwinter temperatures along the coast of North Carolina are on the order
of 20F (-7C) and the average daily maximum during midsummer along the ex-
treme southern coast is only 860F (30*C), some 6 degrees less than is usually
recorded in the interior. July is the wettest month and October the driest.
Along the coast, snow and sleet usually fall only once or twice a year, and
are usually associated with northeasterly winds. Prevailing winds in North
Carolina blow from the southwest most of the year and from the northeast in
September and October (Hardy 1974). The weather along South Carolina is sim-
ilar to that in North Carolina but varies somewhat. Average annual tempera-
tures along the coast of South Carolina are about 680F (20C), with an average
daily maximum in July of 880F (31C). Average daily minimums in January range
from 350F (1.70C) in the northeast to 420F (6C) in the southeast. March is
particularly rainy along the coast, and October and November are the driest
months. Prevailing winds in South Carolina are from the southwest and south
in spring and summer, predominantly from the northeast in autumn, and about
evenly split between northeast and southwest in winter (Landers 1974).

The climate in Georgia is characterized by short mild winters and warm
humid summers. The coastal area becomes progressively drier and warmer from
north to south. Peak periods of precipitation occur in winter and early
spring. The average annual rainfall ranges from more than 75 inches (190 cm)
in the extreme northeastern part of the state to about 53 in (135 cm) along
the lower east coast. Average summer temperatures range from about 730F
(360C) in the extreme north to nearly 82F (28'C) in parts of south Georgia.
Average temperature for the three winter months ranges from 410F (5C) in the
north to 560F (13C) on the lower east coast. Areas in northern Georgia have
freezing temperatures during the day for almost a third of the year but those
along the lower coast only have about 10 days that reach 320F (0C) or less
(Carter 1974).

Florida has a wider range of climates than any other state in the south-
east. The climates range from temperate to subtropical in the north to trop-
ical in the Florida Keys. Summers are warm, relatively humid, and long, and
winters are mild and brief. Rainfall is abundant, with peak rainfall on the
peninsula from June to September. Mean annual temperatures range from the
upper 60's (F) in northern Florida to the mid 70's in the south and reach
nearly 780F (26*C) at Key West. Rainfall varies widely from area to area and
from year to year, with most areas usually receiving between 50-65 in (127-
165 cm). The drier Keys have an average annual rainfall of only about 40 in
(100 cm). On the southern part of the peninsula prevailing winds are from
the southeast and east; elsewhere they are more erratic but tend to be from
the north in winter and from the south in summer. Tropical storms frequently
cause great damage; few years pass without a hurricane affecting one part of
the state or another (Bradley 1974).

The Gulf has a maritime tropical climate with mean winter temperatures
of about 70*F (210C) and mean summer temperatures of 840F (29C). Relative
to other parts of the study area, both summer and winter are hot and humid;

humidity is greatest during spring and summer and lowest during late fall and
winter (BLM 1978a). Rain occurs fairly evenly throughout the year along the
eastern and northern Gulf, with a peak from June through August (BLM 1978a).
The peak tends to be later farther east and occurs in August and September
(BLM 1978b). The area becomes progressively wetter from the southwest to the
north and central portions of the northern Gulf. The driest area of the Tex-
as coast extends from Brownsville north to about Corpus Christi, the most
humid from Galveston to the Sabine River (Chaney et al. 1978). Average annual
precipitation ranges from about 69 cm (27 in) at Brownsville to 137 cm (54 in)
at New Orleans (BLM 1978a) and 170 cm (67 in) in Mobile (BLM 1978b).

Tropical storms and hurricanes that often ravage coastal habitats are
regular during late summer and fall and enter the Gulf largely through the
Yucatan Channel and Straits of Florida. Southeasterly winds predominate over
the northern Gulf during the summer. Easterlies are more common during the
winter and prevailing winds from the west and southwest are rare at any time
of year (BLM 1978a).

METHODS

Most of the information was obtained by a standard academic search of
the literature. Additional information on oiling of individual species of
birds and their distribution was obtained through examination of museum spec-
imens, and from interviews with other individuals but the latter was not a
major source. A preliminary exploration of the resources of several informa-
tion retrieval systems on computers was made but the data did not meet our
needs. These sources were particularly weak on information on local distri-
bution of birds, much of which is to be found in regional journals not cov-
ered by computer services; the depth of temporal coverage was also not ade-
quate for the purposes of this study. We agree that visual searches of orni-
thological and other periodicals "proved far more productive from the stand-
point of both numbers of citations and thoroughness of the search," as Bartonek
and Lensink (1978) pointed out in a review and bibliography of the literature
of marine birds of Alaska.

We obtained literature citations primarily by scanning the literature
and by consulting bibliographies in relevant papers. The primary sources for
the journals, books, and papers consulted were the libraries and reprint files
of the Bird Divisions of the Smithsonian Institution, Washington D.C., and
the American Museum of Natural History, New York. Other major sources of in-
formation were the library of the Department of the Interior, the Library of
Congress, and the Bird Library and reprint files of the Patuxent Wildlife
Research Center at Laurel, Maryland. The Welder Wildlife Foundation, Sinton,
Texas, and the library of government publications and reports maintained by
the National Coastal Ecosystems Team, Slidell, Louisiana, were particularly
rich sources of information otherwise difficult to obtain. Unpublished re-
ports and papers were obtained from personnel of the Florida Audubon Society
at Vero Beach, the Florida Game and Freshwater Fish Commission at Gainesville,
and Everglades National Park at Homestead as well as from other individuals
listed in the acknowledgments. Several dozen valuable but unpublished theses

4

were obtained from several educational institutions.

Searches were made of several secondary sources of literature citations.
Literature review sections of major ornithological journals, particularly The
Auk, The Ibis, and Bird-Banding, were especially useful as was Wildlife Re-
view. Other sources of citations consulted extensively were Current Contents,
Oil Pollution Abstracts, and Dissertation Abstracts. Biological Abstracts,
Ecological Abstracts, and The Zoological Record were also consulted but were
less efficient sources of information. All state bird journals dealing with
the southeastern United States (see list below) were scanned in their entirety
or nearly so; these journals, along with American Birds (Audubon Field Notes
in earlier volumes) provided much of the information on local distribution in
each state.

We placed considerable emphasis on recentness of information in the lit-
erature search. A few journals (e.g., Wilson Bulletin, The Auk, Bird-Banding)
were examined for at least 30 years into the past, The Auk from 1930 to the
present. Many other journals, depending on the degree to which they yielded
useful information, were scanned for only a relatively few recent years. We
made a concerted effort to cover the foreign literature as thoroughly as pos-
sible. Most of the species treated in this report have a wide geographic dis-
tribution, and much of what is known of salient aspects of their breeding
biology is found only in foreign periodicals. The linguistic limitations of
the senior author, as well as the temporal and fiscal limitations involved in
the production of this report, precluded full use of this material.

Listed below are the serial publications covered most extensively by di-
rect examination. Where appropriate, listed in parentheses are those areas
of the world that these journals cover most thoroughly.

Acta Ornithologica (Poland, U.S.S.R.)
Alauda (France, French Africa)
Animal Behavior
Ardea (western Europe)
Auk (North America, world)
Behaviour

Biologia (Bratislava)(Seria B)
(Czechoslavakia)
Biotropica
Blue Jay (central Canada)
Bulletin of the British
Ornithologists' Club (world)
California Fish and Game

Canadian Journal of Zoology
Chesapeake Science (Estuaries)
(U.S. Atlantic coast)
Dansk Fugle (Denmark)
Ecology
Ekologia Polska (Poland)

Alabama Birds
American Birds (Audubon Field Notes)
(United States, Canada)
Atoll Research Bulletin
Australian Bird Watcher

Bird-Banding (Journal of Field
Ornithology) (United States)
Bird Study (Great Britain)
British Birds
Bulletin of the Texas Ornithological
Society
Canadian Field-Naturalist

Chat (North and South Carolina)
Condor (North America, neotropics)
Corella (Austalian Bird-Bander)
Dansk Ornithologisk Forenings Tids-
skrift (Denmark)
Elepaio (Hawaii)

El Hornero (Argentina)
Fauna (Oslo) (Norway)
Florida Naturalist
Gerfaut (western Europe, Africa)

Jack-Pine Warbler (Michigan)
Journal of Animal Ecology
Journal of Ecology
Kingbird (New York)
Larus (Yugoslavia, eastern Europe)
L' Oiseau et la Revue Francaise
d'Ornithologie (France, world)

Marine Pollution Bulletin
Maryland Birdlife
Mississippi Ornithological Society
Newsletter
Notornis (New Zealand, Pacific islands)
Ostrich (South Africa)

Oriole (Georgia)
Ornithologische Mitteilungen (world)
Ornis Fennica (Finland, Baltic area)
Proceedings of the Louisiana Academy
of Science
Revue Suisse de Zoologie (Switzerland,
central Europe)

Rivista Italiana di Ornithologia (Italy)
Ring (Europe, world)
Sterna (Norway)
South Australian Ornithologist
Southwestern Naturalist (southwestern
U.S.)

Tori (Japan)
Transactions of the North American Wild-
life and Natural Resources Conference
Die Vogelwarte (western and central
Europe)
Wilson Bulletin (North America, world)
Zoologichesky Zhurnal (U.S.S.R.)

Emu (Australia, New Guinea)
Florida Field Naturalist
Florida Scientist
Ibis (Old World, Africa)

Journal fur Ornithologie (Germany,
world)
Journal of Applied Ecology
Journal of Wildlife Management (N.
America)
Limosa (Netherlands)
Loon (Minnesota)

Louisiana Ornithological Society News
Mississippi Kite
Murrelet (Pacific northwest, Alaska,
western Canada)
Nos Oiseaux (France, western Europe)
Der Ornithologische Beobachter
(Switzerland, middle Europe)

Oikos (Denmark, Scandinavia)
Ornis Scandinavica (Scandinavia,
Finland)
Proceedings of the Annual Conference
Southeastern Association of Game
and Fish Commissioners (southeast-
ern U.S.)

Ringing & Migration (Great Britain,
world)
Suomen Riista (Finland, Baltic area)
Scottish Birds
Soviet Journal of Ecology

Texas Journal of Science
Var Vagelvarld (Sweden)
Vestnik Zoologi (U.S.S.R.)
Western Birds (western U.S.)
Wildfowl
Zeitschrift fur Tierpsychologie

The reprint files of a number of institutions were a particularly fertile
source for some less easily obtainable material. The most useful of these
were the files of the National Fish and Wildlife Laboratory, the Bird Division
of the National Museum of Natural History, the American Museum of Natural His-
tory, and the Bird Library of the Gabrielson Laboratory of Patuxent National
Wildlife Research Center.

In all, about 10,000 citations dealing directly with the species treated
are included in the three parts of this report. The more general articles
found in the Literature Cited sections at the end of each report will probably
contribute at least an additional 1,000 citatons.

ARRANGEMENT AND CONTENT OF SPECIES ACCOUNTS

The species accounts vary in length and in detail depending upon the
quality and quantity of material examined and depending upon the importance
of the species. Species regularly or seasonally abundant in the southeastern
United States are treated in more detail than those that are less abundant or
that occur there only occasionally. Further, those more susceptible to the
effects of oil pollution and oil development are given a more detailed treat-
ment than other birds of equivalent abundance but lesser vulnerability. The
detail and length of the species accounts are also related to the availability
and recentness of monographic works on the species in question, and to the
degree to which information has accrued since the publication of these works.
All but a very few species covered in this volume were monographed by Palmer
(1962), and summaries that primarily emphasized Old World information for sev-
eral species have recently been provided by Cramp et al. (1974, 1977). None-
theless, much of the important information on the distribution and abundance
in southeastern waters and adjacent areas for pelagic species of birds is only
now being obtained. Much new information was published while this report was
being compiled (e.g., Lee and Booth 1979, Lee and Rowlett 1979, Duncan and
Havard 1980, Rowlett 1980). Although we have attempted to make this report
as timely and thorough as possible, we believe it most likely that marked
differences in status for several species of marine birds in the southeast
will be revealed in the next few years.

ABBREVIATIONS

Most of the abbreviations used in the text are in standard use and will
be known to the reader; a few that we use may be less familiar. These are
listed below with a brief indication of their interpretation.

N, S, E, W, (capitalized without period) compass directions
N., S., E., W. (capitalized with period) geographic site designation
(e.g., S. Padre Island)

photogr. photographed Co. County
coll. collected Par. Parish
spec. specimen NWR National Wildlife Refuge
sp./spp. species (singular/plural) WMA Wildlife Management Area
ad. adult St. Park State Park
imm. immature Natl. Park National Park
subad. subadult Natl. Seashore National Seashore
nonad. nonadult

SD Standard Deviation pers. observ. personal observation
ca. circa (about) pers. comm. personal communication
CBC Christmas Bird Count op. cit. (opere citato) in the
ms manuscript work cited
in prep. in preparation subseq. subsequent
prep. preparer et. seq. and the following
comp. compiler cf (confer) compare/see
ed./eds. editor/editors in litt. in the letters (of)

SPECIES INCLUDED

This report includes all but 2 of the 40 species of loons, grebes, alba-
tross, shearwaters, petrels, storm-petrels, tropicbirds, frigatebirds, cormo-
rants, boobies, gannets, and pelicans recorded at least once from the waters
of the coastal southeastern United States. We also include one species, the
Cahow or Bermuda Petrel, that is as yet unrecorded from the area. This spe-
cies was included because it is a rare and severely endangered species whose
nonbreeding range may include the offshore waters of the Atlantic seaboard.

One of the two species excluded from this report is the Black-bellied
Storm-Petrel (Fregetta tropical known only from an 18th century record from
St. Marks, Florida (Howell 1932, AOU 1957); this record has also been attri-
buted to the White-bellied Storm-Petrel (Fregetta grallaria) (Palmer 1962)
and we suspect the validity of the record. The other species excluded is the
Red-footed or Red-legged Cormorant or Shag (Phalacrocorax gaimardi) reported-
ly seen at Galveston, Texas, in December 1946 (Oberholser 1974). Although
marine birds often wander extraordinary distances, this species is otherwise
known only from the coasts of Peru, Chile, and Argentina (Blake 1977); in the
unlikely event that the identification was correct, we suspect that the bird
may have escaped from captivity.

About half the species treated here are strongly pelagic and are rarely
seen from shore. As a result, pelagic species that may be common offshore
are regarded as accidental in state check-lists and regional works. Two spe-
cies that fit this category are the Blue-faced Booby and the Bridled Tern.
Recent studies (Duncan and Havard 1979 ms, 1980; Lee and Booth 1979) have
found these species to be far more abundant in some areas than was previously
thought. Consequently, we have included accounts for some species that have
been infrequently recorded, but which are probably more common than the record
indicates.

The remaining species treated here are coastal birds (e.g., loons, grebes,
cormorants, pelicans) and include one endangered species, the Brown Pelican,
as well as seven species on the current "Blue List", an "early warning" list
that tries to indicate species that may be declining in all or parts of their
range in North America (Arbib 1979). Three species considered herein, the
Common Loon, Red-necked Grebe, and Double-crested Cormorant, are thought to
be decreasing throughout a wide area; all are moderately to highly susceptible
to oil pollution. Two other species with more restricted ranges, the Western

n apesz

unpubl.

unpublished

Grebe and the White Pelican, are also believed to be declining; the former is
strongly susceptible to oiling. The Eared Grebe and Northern Gannet are mar-
ginally blue-listed because of insufficient evidence and are regarded by Arbib
(1979) as species whose status requires clarification. Both are susceptible
to oil pollution.

SCIENTIFIC AND VERNACULAR NAMES

The species accounts are headed by the English and scientific names of
the species, followed by vernacular names in other languages and alternative
English names used in the United States and other English-speaking countries.

Scientific names used for birds follow the revised edition of Peters'
Check-list of Birds of the World (Dorst and Mougin 1979, Jouanin and Mougin
1979, Storer 1979a, 1979b). Widely used alternative scientific names are also
noted. Explanation is made in footnotes where changes in scientific names
have been adopted recently. Ordinal sequence follows that of the AOU Check-
list (1957) as does the sequence of families, with the exception of the Pele-
caniformes for which we follow Dorst and Mougin (1979). Within families,
species are listed in the order given in the revised edition of Volume I of
Peters' Check-list.

Scientific names of other organisms (e.g., plants, fish, crabs, molluscs)
given in the text are either those used in the works cited or are from stand-
ard recent references or regional guides. Scientific names have been supplied
only when we could be certain what species was meant by the vernacular name
used in the original text.

English names follow the ABA Checklist (ABA 1975) except for two species
(Black-browed Albatross and Cahow) included in this volume but not listed in
the checklist. We also use names different from those in the ABA Checklist
for three other species (Trindade Petrel, Harcourt's Storm Petrel, Blue-faced
Booby). These names are all in widespread use and those used by the ABA are
listed here in the section giving alternative vernacular names.

The primary source for most of the non-English vernacular names is the
Nomina Avium Europaearum (Jorgensen 1958); other sources consulted include
Dement'ev and Gladkov (1951a, 1951b), Austin and Kuroda (1953), Edwards (1972),
and Cramp et al. (1977). The abbreviations for the languages and other geo-
graphical English usages appearing in this section are as follows:

DA: Danish IC: Icelandic PR: Portuguese
DU: Dutch IT: Italian RU: Russian
EN: English (Old World) JA: Japanese SAf: South African
FI: Finnish NW: Norwegian SP: Spanish
FR: French NZ: New Zealand SW: Swedish
GE: German PO: Polish US: United States

With few exceptions the foreign language common names are those in the
widest use in the ornithological literature of the countries indicated. In
several instances we have included transliterated names from languages in

which Roman characters are not used (Japanese, Russian). For Japanese names
we have relied on Austin and Kuroda (1953) and for Russian names we have sup-
plied the names used in translations of Dement'ev and Gladkov (1951a, 1951b).

The primary reason for supplying these alternative names is to assist
future literature searches based on retrieval of citations by computer. Some
of the English translations of foreign language names (which are those entered
on computers) imply a different species than the name would normally suggest
to a reader of English or cannot be readily associated with an English name
(e.g., the translation of the Russian common name for Larus ridibundus is
Laughing Gull, a name that in English indicates the North American Larus atri-
cilla). As a result, searches of computer literature systems by scientific
name alone may fail to indicate important notes or papers documenting recent
changes in distribution.

We supply alternative scientific names widely or recently in use as
another aid to searches of literature compiled on computers. The Caspian Tern
appears in recent literature as Sterna caspia, Sterna tschegrava, Hydroprogne
tschegrava, and Hydroprogne caspia as well as with caspius as a variant of
the specific epithet. One computer search we made revealed no less than four
different lists of titles when each scientific name was used as a keyword.
In addition, many of the more regionally oriented foreign language journals,
like those in the United States, fail to list scientific names in the titles
and in usage might cause confusion when computer-based retrieval of ornitho-
logical information is attempted for a wide geographic area. On the other
hand, when the translated foreign name is one of widespread use in English-
speaking countries we have not bothered to list it.

In some instances we have listed more than one vernacular name for a
foreign language; this is particularly true for Spanish, in which vernacular
names may vary considerably from area to area. Our production process did not
allow a highly accurate rendering of foreign words which incorporates charac-
ters or accents. As a result, there are lapses in our orthography, particu-
larly for the Scandinavian languages.

GENERAL DISTRIBUTION

This section is divided into two parts, one giving occurrence in North
America, the other, occurrence elsewhere in the world. Most of this informa-
tion has been taken from standard distributional works, but we have supple-
mented this material where possible with more recent literature. Breeding
and wintering ranges are emphasized in this section, with less information
given on areas of occurrence during migration. Material relating to North
America is more detailed and more complete than for other areas of the world.

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

In this section we present more detailed remarks on distribution in the
southeast. We have incorporated as much recent information through 1979 as

we have been able to obtain. The basis for this section is the most recent
state ornithological handbooks and checklists; it also includes information
from a search through seasonal observations published in American Birds and
state journals, a retrieval of breeding data from the Cornell Nest Records
Scheme, and a number of unpublished manuscripts dealing with distribution in
various sections of the southeast. This section also incorporates informa-
tion on seasonal occurrence, breeding status and numbers, and brief remarks
on habitats used. The emphasis is on coastal areas but in some cases remarks
are also made about status elsewhere in the state. Available data for many
species are often unsatisfactory, incomplete, or extremely scanty. This is
particularly true for transients, either pelagic migrants or common onshore
migrants whose numbers are seldom recorded.

Information is given in order by state from North Carolina to Texas; we
have not listed states in which a species has not been recorded. A varied
treatment was used for Florida; information is usually presented in two sub-
sections, one dealing with the Atlantic coast, the other with the Gulf. We
adopted this style because status of a species may vary considerably from
coast to coast. In some instances we also included a section dealing with
the Keys when status there is different from that on either coast. On occa-
sion, we have subsumed all information under a single entry for the state;
this is the case when a species is known from Florida from only a very few
records.

Some questions about the biology or racial affinities (the latter indi-
cating the general geographic origin of species not breeding in the southeast)
can best or only be determined by an examination of specimens. Answering
these questions would require the assembly of most available specimens in one
place; alternatively, it would require extensive travel to various museums.
Since relatively few specimens of some seabirds have been collected, we have
in many instances listed an abbreviation indicating the museum in which a
specimen from the southeast is, or is said to have been, deposited. Most of
our information comes from scattered reports in both published and unpublished
literature, some from direct examination of specimens. We list below the ab-
breviations used and the names and addresses of the museums indicated.

AMNH American Museum of Natural History, 79th Street & Central
Park West, New York, NY 10024

Auburn U Mus. Auburn University, Auburn, AL 36830

Brev Mus. Brevard Museum Inc., 2201 Michigan Ave., Cocoa, FL 32922

CC Mus. Corpus Christi Museum, 1919 N. Water St., Corpus Christi, TX
78401

CM Charleston Museum, 121 Rutledge Ave., Charleston, SC 29401

FSM Florida State Museum, University of Florida, Gainesville, FL
32611

FSU Florida State University, Department of Zoology, Tallahassee,
FL 32306

FTU Florida Technological University, Department of Biology,
Orlando, FL 32816

LSU Louisiana State University, Museum of Zoology, Baton Rouge,
LA 70803

MGFC Mississippi Game and Fish Commission, State Wildlife Museum,
111 N. Jefferson Street, Jackson, MS 39202

NCSM North Carolina State Museum of Natural History, North Carolina
State University, Raleigh, NC 27611

SFAU Stephen F. Austin State University, Department of Biology,
Nacogdoches, TX 75961

Texas A&I Texas A & I University, Kingsville, TX 78363

Texas A&M Texas A & M University, Department of Wildlife Science, Col-
lege Station, TX 77843

U Ala University of Alabama Museum of Natural History, University,
AL 35486

U Dallas University of Dallas, Department of Biology, Irving, TX 75060

UG University of Georgia Museum of Natural History, Athens, GA
30602

U Iowa University of Iowa, Museum of Natural History, Iowa City, IA
52240

UM University of Miami, Biology Department, Coral Gables, FL
33124

U Mich University of Michigan, Museum of Zoology, Ann Arbor, MI
48109

UNC University of North Carolina at Wilmington, Biology Depart-
ment, Wilmington, NC 28401

USF University of South Florida, Department of Biology, Tampa,
FL 33620

USNM National Museum of Natural History, Washington, D.C. 20560

WWF Welder Wildlife Foundation, Box 1400, Sinton, TX 78387

SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE

This section in the species accounts summarizes information given in the
previous sections, often with additional data on population levels in the
coastal southeastern United States. Some additional information on the world-
wide status of the species may be included, but the amount given varies great-
ly depending on our present knowledge of the species. We also present tabular
information on seasonal occurrence and abundance of the species in the south-
east and indicate where seasonal concentrations have been seen; information
available on these topics is generally limited and the information we present
will point out where further data should be obtained.

We have used two kinds of maps to indicate where concentrations of marine
birds have been reported, one dealing with breeding birds, the other with win-
tering populations. Breeding colony maps give an estimate of the number of
breeding birds and indicate the year or period to which this estimate applies.
We used the largest recent estimate instead of a range or mean since estimates
are few and we wished to emphasize areas known to have contained significant-
ly large colonies or concentrations of colonies. Not all data obtained were
plotted because some species occur in so many colonies that it was not feasi-
ble to include them on our maps. These maps may contain some inaccuracies,
and are not intended as an atlas; they are intended primarily to give an over-
view of where concentrations of breeding marine birds occur in the southeast-
ern United States.

The material on which these maps are based is highly diverse. It in-
cludes data from the Cornell Nest Records Scheme and a considerable number of
published and unpublished censuses (e.g., Portnoy 1977, Parnell and Soots 1979
ms). Other data were found in recently published papers and obtained from
local ornithologists.

Most of the winter distribution maps are based on those given earlier by
Bystrak (1974), whose report was based on an analysis of Christmas Bird Counts
for one or more of the years from 1970-1972. We chose 45 of 58 coastal Christ-
mas Bird Counts in the study area and compiled 5-year means for 1973-1977.
In some instances fewer than 5 years of counts were available and the mean is
for a shorter period. We picked the localities to show geographic variation
in numbers and to emphasize where the largest concentrations were found.

These figures should not be construed as indicating the true size of lo-
cal populations. The Christmas Bird Counts varied considerably in the amount
of estuarine, coastal, and marine habitat covered, but we tried to allow for
this by choosing counts that contained the most marine habitat. We realize
that the numbers reported in any given year may not be precise because of the
limitations of Christmas Bird Counts. We intend these maps to serve primarily
as an index of where winter concentrations are most likely to be found and
how this distribution varies throughout the southeast.

HABITAT

This section deals with habitats used by the species, and usually consists

13

of relatively brief remarks dealing with nesting, feeding, and winter and/or
offshore habitats used. These categories are often combined when they are
essentially the same, e.g., when the offshore habitat for a species is also
its feeding or wintering area. As in other sections in the species accounts,
the extent and detail of information reported is related to the relative im-
portance of the species in the southeast. Accidental or vagrant species known
from only a few records are often covered in only a few sentences, whereas
more abundant species usually receive a more detailed treatment--particularly
when recent information is available. Little information can be given for
species that are important components of the avifauna but that have been lit-
tle studied (primarily pelagic species such as the Bridled Tern).

FOOD AND FEEDING BEHAVIOR

We give relatively little data on food habits in southeastern waters,
primarily because little or nothing is known of the diet in this area. This
is particularly true for most of the species covered in Volume I of this re-
port. If the less common species are included, one can state conservatively
that nothing certain is known of the diet in the southeast for well over half
the species discussed. Consequently, we have had to rely on data from other
areas on the assumption that similar foods will be eaten in the southeast.

Here again, the amount of information given varies in relation to the
relative importance of the species in the southeastern marine avifauna and
with the amount of information available. In all cases we give at least a
brief general statement of the types of foods eaten and the primary methods
by which they are obtained. In some instances we include more detailed in-
formation on food habits, briefly abstracting recent studies and indicating
proportions of different varieties of foods eaten. We have summarized food
habits by geographic area for a few species for which much recent information
is available. For species whose food habits have been relatively well docu-
mented, we have pointed out differences in food habits of adults and young,
and have commented on seasonal variation of food habits as well as difference
in foods eaten in different habitats.

The primary information given on feeding behavior is the means by which
the species obtains its food. Many of the terms or phrases used are obvious
(e.g., diving from the surface, plunging from the air); a few are not. Usu-
ally those that are unclear are explained more fully in the species accounts.
We give brief definitions of these terms here, based on terminology used by
Ashmole (1971) and Ainley (1977).

aerial dipping = picking prey from just above or just below the surface of
the water while in flight; this includes the pattering of
storm-petrels in which the feet are used to maintain the
birds aloft. The body may or may not make contact with the
water but usually does not do so to any great degree.

aerial seizing = seizing prey in the air while on the wing; use of this
term suggests that the prey may be some distance above the
substrate; roughly equivalent to the term "hawking".

14

deep plunging = diving into the water a substantial distance to seize
underwater prey.

kleptoparasitism = piracy; stealing food from other birds or organisms. This
includes aerial pursuit in which one bird chases another
and forces the latter to disgorge or drop food, which is
then seized. It also includes such pursuits between two
birds on water or land and harassment by a flying bird of
another on water or land.

plunge diving = a more general term that indicates a bird that dives into
the water from the air to seize prey; it includes deep
plunging, surface plunging, and pursuit plunging.

plunging = plunge diving.

pursuit diving = diving from the surface of the water with pursuit of prey
augmented by the use of wings or feet.

pursuit plunging

diving from the air into the water with subsequent under-
water pursuit of prey.

scoop-feeding = surface seizing as practiced by pelicans.

surface dipping = picking prey from just above or just below the surface of
the water while sitting on the surface of the water; simi-
lar to surface seizing, but implying less contact of the
body with the water and (usually) smaller items of prey.

surface plunging = diving into the water from the air to seize prey but the
bird either does not completely submerge or submerges for
only a very short distance.

surface seizing = taking living or dead prey from the surface of the sea or
just beneath it while the bird swims or floats on the sur-
face.

IMPORTANT BIOLOGICAL PARAMETERS

This section presents basic information to allow biologists to infer the
effects of development of oil resources on populations and to help choose al-
ternative courses of action in the planning of such developments. We include
this information for only about half the species discussed in this report be-
cause we believe that these species are those most likely to be significantly
affected by oil in southeastern waters. Much of the information is derived
from studies conducted outside the southeast, because only a few studies of
the breeding biology of marine birds have been conducted there. This lack of
data is particularly frequent for the species (Charadriiformes) that will be
covered in the third volume in this series.

The data in this section consist of brief summaries of the egg laying

period, mean clutch size, incubation period, hatching success, fledging suc-
cess, age at first breeding and at fledging, mortality of eggs and young (in-
cluding information on renesting), maximum natural longevity, and weight.
Data on egg laying, incubation period, and age at fledging allow estimates of
periods when birds breeding within the study area are most vulnerable to dis-
turbance. Information on mortality and renesting point out those factors
that lower the birds' reproductive success and suggest the potential for re-
covery following a nesting failure. Data on clutch size and hatching and
fledging success allow an estimate of productivity. Detailed life table data
are unavailable for most of the species covered in these reports. Consequent-
ly, we have provided figures for known maximum natural longevity that will in
some instances allow a crude comparison of the total reproductive potential
between species. The maximum natural longevity is given in terms of "esti-
mated minimum age" in years and months following Kennard (1975), and may list
information based on banding in both the United States and Canada and the Old
World. Finally, we include information on weights because this and population
data given elsewhere in the report will allow planners to compare species in
terms of biomass affected as the result of any given oil-related activity.

The quality and quantity of this information vary from species to species
and from topic to topic. Many of the waterfowl treated in the second volume
of this report are among the best-studied wild birds. For such species we
make no attempt to give all the information available, but confine ourselves
to brief summary statements. For many other species, particularly those that
would be more often regarded as seabirds, information is sparse, inadequate,
or completely nonexistent. We have indicated this in each account.

SUSCEPTIBILITY TO OIL POLLUTION

Instances of oiling for a given species are documented to show that the
species can be affected. We have stressed records from southeastern waters.
Data are reported on the number killed in major oiling incidents and the pro-
portion this represented of the total number of all birds killed and identi-
fied to species. We may have missed reports of oiling for some species. Much
of the Old World literature reports oiled birds only by species groups (e.g.,
gulls, ducks) and combines information on individual species in these totals.
Some information may be found in Old World regional periodicals unavailable
in the United States and not covered by computer-based literature retrieval
systems.

This section also refers frequently to an oil-vulnerabity index for birds
in the northeastern Pacific developed by King and Sanger (1979). That publi-
cation, though valuable, has been used with caution because it refers to a
different geographic area with a dissimilar environment and a different (but
strongly overlapping) species complex. We include in this section some of
King and Sanger's index scores, not to indicate the degree of vulnerability
in the southeast (although we often think that it is similar), but rather to
show the degree of vulnerability in another part of the range. The northeast-
ern Pacific area is important to North American populations of a number of
species regularly occurring in the southeast (e.g., Common Loon, Horned Grebe,
Leach's Storm-Petrel) that are at moderate to high risk from oil development

activities in both areas.

In most accounts where we have referred to this index we have supplied
King and Sanger's (1979) interpretation of the index. We give here a summary
of their point scale and its use in determining both degree of danger to a
given species and those adjustments in plans for development that may be re-
quired as a result.

Range of
Scores Interpretation of Index Values

1-20 Very low risk species; ones "where damage or future costs would not
be expected"..."where problems will be fewest".

21-40 Low risk species; those "for which there is a low level of concern"
and which may require consideration for only those parts of a project
that might significantly influence a species.

41-60 Mid-risk species; those that may be adversely affected but not cata-
strophically. King and Sanger (1979) suggest that the status of
these species should be monitored during project development and
that palliative measures be taken if damaging effects are detected.

61-100 High-risk species; those that are almost certain to be adversely af-
fected by oil development activities. These species will need the
most additional research, additional planning for the effects of
disasters, and additional consideration about possible modifications
of projects.

In addition, we provide in this section our estimate of the overall po-
tential effect of oil pollution and the development of oil resources on the
species in the southeast, taking into account the known or suspected relative
vulnerability of the species, its abundance in the southeast, and its abun-
dance elsewhere.

SPECIES BIBLIOGRAPHY

All citations used in the text of the species accounts are included in
the bibliography at the end of this report. Selected references to the spe-
cies treated are found in the species bibliography at the end of each account.
The species bibliography includes citations that provide data on the topics
briefly covered in the text, as well as on other aspects of the distribution
and biology of the species.

These bibliographies are not exhaustive. The emphasis in our species
bibliographies is placed on the ecology and behavior of the species. More
general works and some distributional literature are found in the terminal
section of literature cited. Although some material on taxonomy, parasito-
logy, hybrids, identification, disease, and other subjects, may be included,
we did not specifically search for this material. We covered the world lit-

17

erature because little is known of the biology of most marine birds in the
coastal southeastern United States.

Our search of the literature also stressed recentness of information and
each species bibliography should be relatively complete through at least mid-
1979, our cut-off date for inclusion of references. A few important refer-
ences published subsequently may be included but these may not have been used
in writing the account. We have listed other important papers dealing with
the biology of the species through the early part of the century, but have
been more complete with papers written in English. We include older refer-
ences that are still the major source of information on the species.

The species bibliographies are arranged from present to past with authors
listed alphabetically under each year, rather than the more conventional alpha-
betical and chronological listing used in the Literature Cited. We did so to
make it easier for the reader to find the most recent information on any top-
ic covered by the bibliography.

We have checked all references used in the text portion of the accounts
as well as a large proportion of the remaining references. Some citations
from secondary sources remain unchecked. We estimate that the three volumes
in this series will contain on the order of 10,000 references in the terminal
species bibliographies, and our temporal and fiscal limitations were too great
for us to undertake complete verification of all references included.

OIL POLLUTION AND MARINE BIRDS OF THE SOUTHEASTERN UNITED STATES

With the possible exception of marine turtles, marine birds are the ver-
tebrates most severely threatened by oil pollution and the development of oil
resources. The work of Old World biologists presents clear evidence of severe
and substantial damage to several populations of marine birds.

Specific, detailed information on the effects of oiling and oil spills
on wild birds and their populations in the New World, and especially for the
the southeastern United States, is very limited. In many instances it is un-
known whether any given species has ever been oiled and what effect this may
have had. Systematic gathering of data on the species composition of large
seabird kills following oil spills has been done infrequently in the New World
and systematic surveys of beached birds have only recently begun in the United
States. Further, data on oiling of marine birds are scattered through a di-
verse body of literature. Many distributional notes reporting the first spec-
imen of a species from a geographic locality parenthetically note that the
specimen was oiled. Other information is scattered through regional distri-
butional works and yet more data, which we have not had time to explore fully,
lie in the banding and recovery files of the Bird Banding Laboratory of the
U.S. Fish and Wildlife Service.

In Denmark, oil pollution kills thousands of seabirds each year; most of
these are ducks, but many other species are also involved (Riisgard 1979).
Oil has caused major losses in populations of Common Eiders in the Danish

Waddensea (Joensen 1973), in breeding populations of Common Eiders and Black
Scoters in Holland (Swennen and Spaans 1970), and in populations of the At-
lantic Puffin (Fratercula arctica) in France (Bourne 1976). Oil is also a
major cause of death for Jackass Penguins (Spheniscus demersus) in South
Africa (Randall et al. 1980).

Other losses reported include the death of an estimated 25-50% of the
Common Loons wintering in Shetland after the ESSO BERNICLA oil spill on 30
December 1978 (Stowe and Morgan 1979), and the loss of all Mallards, European
Coots (Fulica atra), and Moorhens (= Common Gallinule, Gallinula chloropus)
following an oiling of the Amer River in the Netherlands. In the latter oil
spill it was estimated that about 88% of the Greylag Geese (Anser anser) and
about 71% of the Bewick's Swans (Cygnus columbianus bewickii) would ultimate-
ly be lost as well (Belterman 1972). Still other examples of major reductions
in avian populations due to oil pollution are given in reviews by Croxall
(1975), Vermeer and Vermeer (1975), Bourne (1968b, 1976), and FAO (1977).

VARIABILITY IN SPECIES' SUSCEPTIBILITY TO OIL POLLUTION

Surveys of beached birds are biased indicators of what proportion of a
population is affected by oiling (Bourne 1976). The proportions of species
found oiled does give some idea of differences in susceptibility between dif-
ferent groups of birds and also suggests the magnitude of the oil pollution
problem for a given area. Such surveys may also provide data on seasonal var-
iation in the incidence and extent of oil pollution. Table 1 gives the per-
centage of beached birds that were oiled in four different areas. Species
such as loons, grebes, auks, and sea ducks are most affected, whereas more
aerial species such as gulls and terns are usually among the least affected.

REGIONAL DIFFERENCES IN OILING AND MORTALITY OF BEACHED BIRDS

Although beached bird surveys in the eastern United States have been con-
ducted for only a relatively short time, the extent of oiling in birds found
dead along the southern Atlantic coast apDears low compared with other areas
in the United States and elsewhere. Only 4% of 400 birdF found dead along
the southern Atlantic coast from January 1976 through Aust 1978 were oiled.
In contrast, oiling occurred in 82% of 667 birds found along the Polish Bal-
tic coast from November 1974 to August 1975 (Gorski et al. 1977), in 26Z of
162 found along Irish coasts from December 1977 to March 1978 (O'Keeffe 1978),
in 79% of 3,431 found on the international beached bird surveys in Nrthwest
Europe in January-March 1975 (Lloyd t976\ ar 1.t2\1 \ 3 sv. s ,i
the California coast in 1975 (Ainley 1976).

Bird mortality per mile of beach also tends to be less in the southeast-
ern United States than in other areas (Table 2). Mortality figures for a
fairly heavily polluted area, the Polish Baltic coast (3.2 birds/km or 5.2/m
Gorski et al. 1977), are considerably higher than for anywhere in thi south-
east. Other areas in northwestern Europe vary considerably in 7coried .;or-
tality during beached bird surveys, but mortalities are usually greater th:in
those found in the southeastern United States. Lloyd (1976) r1uor'-d a range

Table 1. Number and percentage of beached birds examined and oiled (a).

Kinds of birds

Loons (Divers)
Grebes
Albatross
Petrels (b)
Northern Fulmar (c)
Shearwaters
Storm-petrels
Gannets
Cormorants
Brown Pelican
Wildfowl
Phalaropes
Jaegers
Kittiwake
Gulls
Terns
Skimmer
Auks

South-
Great Atlantic Coast
Britain United States

Total % Total %
found oiled found oiled

152 94 114
54 59 14
-- -- 0
337 17 0
-- -- 0
.-- 14
-- -- 0
182 50 6
218 45 6
-- -- 17
1137 76 51
-- -- 0
-- -- 1
-- 0
2448 30 131
.-- 37
6171 80 0
6171 80 0

(a) Data for Great Britain, the south-Atlantic coast of the United States,
the Oregon-Washington coast, and the California coast are from Table 1
in Bourne (1976), Malcolm Simons (in litt.), Table 2 in Harrington-Tweit
(1979), and Table 3 in Ainley (1976), respectively; the periods covered
are 1968-1970, December 1977-August 1978, and mid-winter 1976, respec-
tively. Data for the southeastern coast through 1 December 1977 are
based on surveys from Cape Hatteras, North Carolina to Cape Canaveral,
Florida, thereafter south to Jensen Beach, Florida.
(b) Although Bourne (1976) did not specifically so state, his term 'petrels'
probably indicates all Procellariidae (petrels, shearwaters, fulmars,
etc.), and may have included Hydrobatidae (storm-petrels) as well. His
term 'gulls' probably indicates all Laridae (gulls and terns). For
other material summarized here, 'petrels' refers to Pterodroma, 'shear-
waters' to Puffinus, 'gulls' to Larus, and 'terns' to Sterninae.
(c) Harrington-Tweit pointed out that fulmar mortality and at least half
that of Black-legged Kittiwakes was not due to oil but that most wild-
fowl and alcid mortality was attributable to oil.

Oregon-
Washington
Coast

Total %
found oiled

California
Coast

Total %
found oiled

175
798
8
0?
301
623
40

6=3
38
296
119
8
33
1197

2848

10
5
0

4
22
0

0.5
0
7
3
0
24
2

19

Table 2. Comparison of regional and seasonal variation of beached bird
mortality and incidence of oiling in the eastern United States (a).

Atlantic Coast Atlantic Coast
N of Cape Hatteras S of Cape Hatteras Florida Gulf Coast

Dead Dead Dead
birds/ % birds/ % birds/ %
Dates mile oiled mile oiled mile oiled

SPRING

Mar.-May 1979 -- 51.4 --- 20.0 --- 0.0
Mar.-May. 1978 -- 66.8 (b) 1.58 0.0 -- --
Mar.-May 1977 2.50 5.5 0.95 0.0 0.75 0.0

SUMMER

Jun.-Aug. 1979 4.40 1.2 0.38 5.6 0.53 0.0
Jun.-Aug. 1978 6.37 0.0 1.00 0.0 1.50 0.0
Jun.-Aug. 1977 6.81 0.9 0.14 0.0 --- --

FALL

Sep.-Nov. 1979 0.98 13.4 1.43 0.0 0.59 0.0
Sep.-Nov. 1978 1.05 0.0 1.49 0.0 1.00 5.6
Sep.-Nov. 1977 0.24 0.0 0.60 0.0 1.25 0.0

WINTER

Dec.-Feb. 1978-79 2.19 2.3 1.84 1.1 1.74 0.0
Dec.-Feb. 1977-78 2.70 6.5 2.87 1.4 -- ---
Dec.-Feb. 1976-77 9.33 5.5 1.75 0.0 2.88 0.0

(a) This comparison is based on information provided by the Atlantic and
Gulf Coast Beach Bird Survey Project. These data, while useful, have
sometimes been based on surveys of so few miles of beach that the results
obtained may not be adequately comparable from region to region. Dashes
indicate that we lack data.
(b) This high figure is the result of an oil spill in the Chesapeake Bay in
February 1978.

of 0.17 km (0.3/mi) in part of France to 4.06/km (6.5/mi) in West Germany dur-
ing the winter of 1975. For Great Britain, 1968-70, the average was 1.3 km
(2.1/mi) (Bourne 1976). Reported mortality along the California coast is also
apparently greater than in the southeast; surveys there averaged 3.5 birds/mi
(2.2/km) from 1971 to 1975 (Ainley 1976). The disparity in beached bird mor-
tality rates between California and Europe compared to the southeast may re-

suit partly from differences in prevailing winds and currents. In parts of
North America where prevailing winds blow offshore, most mortality is found
around enclosed inlets. On islands offshore North America and in Northwest
Europe, where prevailing winds carry dying birds (and oil) to shore, chronic
oil pollution and the recorded mortality of marine birds are greater (Bourne
1976).

MAJOR BIRD KILLS FOLLOWING OIL SPILLS IN THE SOUTHEASTERN UNITED STATES

There are few records of large bird kills after oil spills in southeast-
ern waters, and the records that do exist are usually inadequate. A typical
example occurred in late December 1968, when a barge spilled crude oil along
the coast of Wakulla County, Florida. This resulted in "many ducks, snipe
and other birds so covered with oil that they were unable to fly. Smaller
birds were unable to walk in the heavy oil" (CSLP 1969).

We found only two reports of major oil spills in or very near the study
area for which there is even fair information on the number and species of
birds killed. The first of these occurred in early February 1976 in the
lower Chesapeake Bay. About 250,000 gal (950,000 1) of No. 6 fuel oil entered
the bay following the sinking of a barge near the mouth of the Potomac River
(Roland et al. 1977). Subsequent movement of the oil resulted in the wide-
spread contamination of marshes and beaches. Roland et al. (1977) estimated
that 20,000 to 50,000 birds were killed. Horned Grebes accounted for more
than half the dead birds counted; this is one of the largest known losses to
oil for this species. Sea ducks, diving ducks, and Common Loons accounted
for a large share of the rest of the total, but Whistling Swans, Black Ducks,
Canada Geese, Double-crested Cormorants, and other species were also killed.

The second major mortality following an oil spill in the southeast was
in Tampa Bay on the Florida Gulf in mid-February 1970 (Sims 1970). Some 80-
100 tons of Bunker C oil were spilled from the Greek tanker DELIAN APPOLON
when it ran aground and ruptured its hull (Wallace 1970, Clark 1973). Winds
and tide spread the oil to cover more than 100 sq mi (259 sq km) of Tampa Bay.
Sims (1970) estimated that as many as 4,500 birds were handled at cleansing
and rehabilitation stations after the spill, and Clark (1973) suggested that
there may have been as many as 9,000 casualties. Sims (1970) indicated that
the St. Petersburg Audubon Society handled "some 500 Common Loon, 200 Horned
Grebe, 200 Red-breasted Merganser, 2500 Lesser Scaup and 100 other species
including several cormorant, two Mallard, a White-winged Scoter, several
heron, a kingfisher and many small shore birds."

SOURCES OF VARIATION IN MORTALITY FROM OIL POLLUTION

A large number of factors are involved in determining the magnitude of
detrimental effects of oil pollution to marine birds. Birds oiled in cold
weather and cold waters have a much higher fatality rate than do those in
warm weather and warm waters. Even minimal amounts of oil may lead quickly
to death under the stress of a cold environmental regime (Levy 1980), but
birds in warmer areas may well survive the same degree of oiling (R. Clapp,

pers. observe C. Harrison, pers. comm.). Reports from Europe (Bourne and
Bibby 1975, Riisgard 1979) indicate that mortality from oiling is greater
during the winter months than during the summer.

Oil spilled in colder water remains liquid longer than in warmer water
and is likely to cause more damage as a result. It first forms into a "choc-
olate mousse" water in oil emulsion and then into tar-balls. Although these
forms of oil may present some hazard to the birds encountering them (Bourne
and Bibby 1975), the hazard is apparently much less than with fresh oil.

Bourne (1976) summarized some of the changes in daily, annual, and life
cycles of marine birds that may increase their vulnerability to oil pollution.
Local currents and winds may bring drifting slicks into rafts of birds roost-
ing on the water. Bourne and Devlin (1969) suggested that most mortality
from oiling occurs when roosting or feeding birds are trapped by drifting
slicks.

Breeding populations are particularly susceptible to oil. The loss of
one member of a pair may mean complete loss of their reproductive potential
for that year. Depending on the number of offspring usually produced, this
could mean that every breeding bird killed by oil represents a theoretical
loss to the population of two birds or more. Although this loss may be re-
couped in future generations, most marine birds have relatively low produc-
tivity and their populations may take many years to recover from one severe
oiling incident. Oil in the vicinity of breeding colonies may also diminish
reproductive success in other ways, such as decrease in the hatching success
of contaminated eggs, and by disturbance to the colony resulting from attempts
to control pollution (Bourne 1976).

Bourne also pointed out that marine birds are particularly susceptible
to damage from oil when they are molting. When birds lack their usual insula-
tion, even smaller than usual amounts of oil may lead to death from chilling,
shock, and starvation. Some waterfowl perform a molt-migration in which large
numbers gather away from the breeding ground to renew feathers before continu-
ing migration. Some may molt in late summer, others in the spring just before
their migration north. Birds in such concentrations would be much more like-
ly to die in large numbers than those with normal mobility.

Relatively few observations have been reported on the behavior of birds
encountering oil. Information available indicates that differences in behav-
ior between species may increase or decrease their vulnerability. According
to the ICPB (1960), Long-tailed Ducks (Old Squaw) will choose to land on oil
slicks. If true, this may in part account for some of the very high oil-
related mortalities that have been reported for this diving duck. On the
other hand, Guillemots (Common Murres) dive to escape floating oil but suffer
the risk of emerging into it and thus becoming severely contaminated (Bourne
1968b). Other species may actively avoid oil; Hainard (1959) reported that
some diving ducks (Tufted Duck [Aythya fuligula] and Pochard [A. ferina])
avoided patches of oil floating down a river. Other, more aerial species,
such as gulls (Bourne 1968b) and Manx Shearwaters (Casement 1966), may also
actively avoid at least the thicker, more noticeable oil slicks. Some of
these birds evidently avoid oil when swimming as well; a Herring Gull and a

Black-legged Kittiwake that swam into a patch of floating oil immediately
took flight (Bourne 1968b, Bourne and Devlin 1969).

The number of birds that die following an oil spill is also related to
the type of petroleum that was spilled and how long it has been in the envi-
ronment. Crude oil is less toxic than refined oils (diesel oil, No. 2 fuel
oil, Bunker "C") (Hay 1979), and fresh oil causes more damage than older,
more weathered oils (Bourne and Bibby 1975). Some oils may be innocuous
enough that oiled birds are not killed and are even capable of cleaning their
plumage (Birkhead et al. 1973, Phillips 1974).

The number of deaths from oiling following a spill is not necessarily
related to the amount of oil spilled; large spills may result in relatively
small death tolls, while smaller spills may cause large losses, particularly
when substantial numbers of birds are concentrated in small areas (Croxall
1975, Salomonsen 1979). In addition, large catastrophic oil spills may cause
no greater loss of marine birds than does chronic oil pollution of the envi-
ronment (Nelson-Smith 1973, Croxall 1975, Holmes and Cronshaw 1977).

EFFECTS OF OIL ON CONTAMINATED BIRDS AND THEIR EGGS

The primary effect of oil on birds is a loss of buoyancy and insulation
when the feathers become matted (Szaro 1977). This increases the metabolic
demand to maintain body heat and in cold weather quickly results in chilling.
The increased amount of physical effort to remain afloat also increases the
demand on the body's resources, and death from exhaustion and exposure may
ensue (Bourne 1976). McEwan and Koelink (1973) reported that heat loss of
experimentally oiled Mallards and scaup was 1.7 and 2 times greater than nor-
mal, respectively.

Ingestion of oil as the contaminated bird tries to preen its feathers
will usually cause further harm. A pioneer study by Hartung and Hunt (1966)
showed that ingestion of oil by Mallards and Black Ducks could be followed by
nervous disorders, enlargement of the adrenal cortex, lipid pneumonia, diar-
rhea, and gastrointestinal irritation. A considerable number of experimental
studies conducted on marine birds in the United States have been reviewed re-
cently at length by Albers (1977), Holmes and Cronshaw (1977), Szaro (1977),
Ohlendorf et al. (1978), Eastin and Hoffman (1979), and Stickel and Dieter
(1979). Some of the findings that involve both primary and secondary effects
of oiling are briefly summarized here.

(1) Physiological effects observed that result from ingestion of oil
include dehydration, enteritis, fatty changes in the liver, renal
tubular nephrosis, and reduction in the rates of sodium and water
transfer across intestinal mucosa (various authors in Ohlendorf et
al. 1978);

(2) A relatively low degree of mortality (under unstressed conditions)
was found for adult Mallards that were fed small amounts of oil, but
ducklings were more adversely affected (Stickel and Dieter 1979);

(3) Mallard hens laid only about half as many eggs as usual when fed
diets containing 2.5% South Louisiana crude oil (Eastin and Hoffman
1979, Stickel and Dieter 1979);

(4) Ducklings fed 5% South Louisiana crude oil grew more poorly than
controls, did not develop normal flight feathers, and exhibited
liver hypertrophy and splenic atrophy (Eastin and Hoffman 1979).

Oil, even in miniscule amounts, will severely reduce the hatching suc-
cess of duck, heron, gull, and tern eggs (Eastin and Hoffman 1979, Stickel
and Dieter 1979). As little as 5 microliters of oil reduced hatching of Mal-
lard eggs from 26% (for Prudhoe Bay crude oil) to 90% (for South Louisiana
crude oil; Stickel and Dieter 1979). Toxicity of these and other oils is
greater for less incubated eggs than for those further along in incubation,
and older weathered oils are less toxic than fresh ones. Experimental oiling
of the plumage of incubating gulls has revealed than this will cause signifi-
cant egg mortality when the oiled feathers come in contact with the eggs.
Oiling of eggs also resulted in a significant number of deformed chicks;
deformed bills, incompletely ossified wing or foot bones, abnormally small
liver lobes, and stunting were the most common abnormalities found in these
experimental studies (Stickel and Dieter 1979).

POTENTIAL HAZARDS TO MARINE BIRDS FROM OFFSHORE OIL PRODUCTION

About two-thirds of the oil in coastal waters is derived from runoff and
effluent from terrestrial sources. Tanker operations account for about 26
times more oil than offshore operations in marine waters of the United
States (Ohlendorf et al. 1978), but may account for a disproportionately
large share.of avian mortality to oil. Ohlendorf et al. (1978) suggest that,
for the marine environment, it may be safer to produce oil offshore than to
import it. It seems very likely, however, that onshore habitat change and
loss resulting from the development of facilities related to offshore oil
production will, in the long run, have a more adverse effect on the water-
birds of the southeastern United States than will oil production itself.

Longley and Jackson (1980) have reviewed this problem for brackish marsh
areas. They summarized activities related to oil production and their ef-
fects on the environment and suggested ameliorative measures that may be tak-
en. Effects include direct loss of vegetation and animals (e.g., by dredging,
construction of pipelines and roads), addition of dissolved, particulate, and
toxic materials to the environment, and changes in water flows. The authors
consider changes in water flow the most damaging hazard, one that may result
in complete conversion of a marsh ecosystem. Such an event could be accompa-
nied by a reduction or elimination of the populations of marine birds that
use this habitat for nesting or feeding.

Similar effects are very likely when offshore barrier islands are af-
fected by development of oil and gas resources. Changes in water flow due to
dredging could easily change tidal and current patterns that would destroy
islands used for nesting. Terrestrial access to larger islands may result in
the introduction of predators (e.g., foxes, raccoons) that could eliminate an

entire colony in a season or two. Disturbance engendered by construction
might result in the mass desertion of a traditional breeding area by some
species.

Several recent reports review aspects of human activities that are rele-
vant to development of onshore oil facilities. These reports include the
Mulvihill et al. (1980) detailed review of the effects of shoreline structures
on the coastal environment, Morton's (1976) review of the ecological effects
of dredging, and Buckley and Buckley's (1976, 1977) reviews of the effects of
human disturbance on colonially nesting birds.

Burning of natural gas at elevated flares during oil production is anoth-
er potential hazard because birds migrating at night sometimes come to such
lights. Considerable numbers have been killed at TV towers, lighthouses, and
airport ceilometers (Howe et al. 1978), and it might be expected that the ele-
vated flares would attract and incinerate passing birds. Bourne (1979a) has
recently reviewed the problem and reported that there have been only about
"half-a-dozen second hand" reports of death from this cause during the first
decade of oil development in the North Sea, an area where foggy weather con-
ditions should maximize the phenomenon. After commenting on several specific
instances of relatively severe loss, including one in which "several hundred
storm-petrels" reportedly died, Bourne concluded that "the losses are only an
insignificant proportion of the millions of birds passing through the area..."

RECOMMENDATIONS FOR FUTURE RESEARCH

This report reveals large gaps in the body of knowledge necessary to
deal effectively with problems relating to marine birds and OCS development.
In some areas we know so little that the wise decisions required to maintain
a healthy environment, while exploiting additional sources of energy, are not
likely to be made. Consequently, we have identified below some of the prob-
lems relating to marine birds and oil pollution that we strongly believe most
need attention; we point out both species and geographic areas where informa-
tion is weakest and suggest investigation of some aspects that are poorly
known about the effects of oiling on marine birds.

STATUS AND BIOLOGY OF BREEDING SPECIES

The size of breeding populations of marine birds in the southeast is
still poorly known. When data are available, they were often taken for too
short a period to allow for the annual variation in population size frequent-
ly found in marine birds. Portnoy's (1977) survey of the Louisiana, Alabama,
and Mississippi coasts provides recent data on coastal breeding populations
there, but these data, though useful, are based on observations made in only
a single breeding season. Available information on populations breeding in
the coastal areas of Georgia and South Carolina is inadequate and information
on Florida populations is available only for portions of the state. In addi-
tion, the location and size of breeding colonies of more conspicuous species
(e.g., Brown Pelican, Royal Tern) that occupy relatively few nesting sites,

are better known than those of others (e.g., Double-crested Cormorant, Laugh-
ing Gull, Forster's Tern) whose colonies are more numerous and widely dis-
persed and found in habitats less easily surveyed.

Studies of the breeding biology of many seabird species are only in their
infancy. Information on regional differences in nesting success and chronol-
ogy, degree of annual variation in production of young, factors influencing
nest site selection, determinants of colony location (particularly in relation
to food resources), and other demographic parameters, is necessary for satis-
factory evaluation of the effect of managerial decisions on the well-being of
populations. We urge that such studies should be undertaken over a period of
several years; studies conducted during a single season simply do not provide
enough information for most managerial purposes. As NERC (1977) pointed out,
"...such [long-term studies are] essential as a baseline against which the
results of future studies or environmental impacts can be measured."

Few marine birds of the southeastern United States are well studied in
regard to their breeding biology and ecology in this area and adequate infor-
mation for some of them has never been obtained anywhere. Only seven species
discussed here (Least and Pied-billed grebes, Magnificent Frigatebird, Double-
crested and Olivaceous cormorants, White Pelican, and the endangered Brown
Pelican) breed in the southeast. Of these, the Brown Pelican is the best stud-
ied; two others (Least and Pied-billed grebes) are relatively poorly known but
are probably not seriously threatened by oil pollution. The Olivaceous Cormo-
rant has been investigated in some detail in recent years and the White Peli-
can has been relatively well examined, but only outside southeastern waters.
Very little is known of the two remaining forms, the Magnificent Frigatebird
and the Florida race of the Double-crested Cormorant. The only frigatebird
colony within the United States is off southern Florida, but little informa-
tion has been obtained there. The species has been little studied anywhere
in the world. These birds should not be particularly susceptible to the di-
rect effects of oil pollution, but could be affected by the ancillary effects
of development of petroleum resources on the outer continental shelf. Knowl-
edge of the biology and populations of the cormorant is scant, although this
species is potentially highly susceptible to the effects of oil pollution in
coastal waters and is also one of the most abundant marine birds in the south-
east as a breeding bird, transient, and winter resident. The Double-crested
Cormorant is clearly a species whose status, biology, and movements should be
better known.

DISTRIBUTION AND STATUS OF PELAGIC SPECIES

Our awareness of the distribution and status of pelagic birds is even
more inadequate than that of nesting seabirds. Most of the information on
the occurrence or numbers of some species was obtained during the last 5 years,
and a surprisingly large amount of information was published during the prepa-
ration of this report (1978-79). Table 3 lists ten pelagic species covered in
this volume for which a particularly large proportion of the information on
distributional status in the southeast has been obtained recently.

Present knowledge of the status of pelagic birds in the southeast varies

Table 3. Approximate percentage of all individuals of ten species of
pelagic seabirds ever recorded in the southeastern United States from 1975
to 1979 and from 1978 to 1979.

Percentage Percentage
seen seen
Species 1975-1979 1978-1979

Northern Fulmar 96 92
Trindade Petrel 100 (1 record) 100
Black-capped Petrel 84 68
Manx Shearwater 63 37
Audubon's Shearwater 32 13
Wilson's Storm-Petrel 40 26
Leach's Storm-Petrel 31 8
Red-billed Tropicbird 100 (4 records) 75
White-tailed Tropicbird 30 9
Blue-faced Booby (a) 24 12

(a) Figures for this species are derived from those given in the species ac-
count. Perhaps as many as another 150 birds were seen in the Gulf by
Duncan and Havard since 1975, but details of all these observations are
not available. If this assumption is correct, it means that approximate-
ly 56% of the Blue-faced Boobies reported from southeastern waters were
seen during the last 5 years.

from species to species and from state to state. Goodman and Klose (1978)
stated that the second most important site for U.S. oil development on the
Atlantic outer coastal shelf is in the center of the Georgia Embayment that
extends from about central South Carolina to northern Florida; this is also
the area where the status of marine birds is less well known than anywhere
else along the Atlantic coast. This is particularly true for pelagic spe-
cies, some of which may occur there in very large numbers. We compare (Table
4) the apparent status of the pelagic species covered in this volume in the
northern, central, and southern portions of the southeastern Atlantic coast.
This comparison indicates the lack of data from the central area. Most sur-
veys of offshore waters have been conducted at the northern and southern ends
of this region.

The only pelagic surveys that have been conducted with any thoroughness
or regularity in the southeastern United States are those by David Lee in
North Carolina, by John Johnson in Florida, and by Charles Duncan and Ralph
Havard in Alabama. Surveys elsewhere in the southeast have been infrequent
and informal. Our knowledge of the distribution and numbers of pelagic birds
in the Gulf of Mexico is especially weak and is even less satisfactory than
our knowledge of pelagic distribution off the Atlantic coast. Our lack of

Table 4. Apparent status of some pelagic
states (a).

seabirds in three Atlantic coast

Area of south Atlantic coast

Probable
direction Florida

Species of origin

Black-browed S
Albatross

Yellow-nosed S
Albatross

Northern N
Fulmar

Trindade S
Petrel

Black-capped SE
Petrel

Bulwer's E
Petrel

Cory's E
Shearwater

Greater S
Shearwater

Sooty S
Shearwater

Manx NE
Shearwater

Audubon's SE
Shearwater

Wilson's S
Storm-Petrel

North Carolina

Accidental
summer

..........

Rare
fall-spring

Accidental
summer

Uncommon
spring,fall

Common-Abundant
spring-fall

Common
spring-summer

Abundant
spring-summer

Rare
winter-spring

Common-Abundant
spring-fall

Abundant
spring-summer

Georgia

......... .

Accidental
fall

Uncommon
summer

Accidental
spring

Uncommon

Atlantic Coast

Accidental
fall

Accidental
summer

Uncommon
spring-fall

Accidental (Keys)
spring

Common
summer-fall

Common
summer-fall

Uncommon ?
summer-fall

Rare
all year

Common
summer-fall

Common

summer-fall spring-summer

White-faced
Storm-Petrel

E Rare
fall

..........

Table 4. Continued.

Area of south Atlantic coast

Probable
direction Florida
Species of origin North Carolina Georgia Atlantic Coast

Harcourt's E Accidental .......... Rare
Storm-Petrel summer summer-fall

Leach's N Uncommon? .......... Rare?
Storm-Petrel spring,fall all year

Red-billed SE Accidental .......... Accidental
Tropicbird spring fall

White-tailed SE Uncommon Accidental Uncommon
Tropicbird summer summer spring-summer

Magnificent S,SE Uncommon Rare Uncommon
Frigatebird spring-summer spring-fall fall-spring

Northern N Abundant Common Abundant
Gannet fall-spring fall-spring winter-fall

Blue-faced S,SE .......... .......... Rare
Booby summer-fall

Red-footed SE .......... .......... Rare (Keys)
Booby spring-fall

Brown S,SE .......... .......... Rare
Booby all year

(a) Pelagic species unrecorded from the three areas considered are not listed
but species known primarily from the Florida Keys are included. Only
periods of reported peak abundance are indicated.

knowledge is shown by Duncan and Havard's (1980) study that revealed that the
Blue-faced Booby, until very recently believed rare in the northern Gulf, is
in fact a regular and major part of the pelagic avifauna. Consequently, we
suggest that a survey to determine the status of the pelagic avifauna be con-
ducted over a broad area of the Gulf of Mexico, both because of past exploi-
tation of petroleum resources in this area and because further development
here may be anticipated in the future.

Hope-Jones (1980) remarked that "...a knowledge of the patterns of dis-
tribution and density of seabirds at sea is vital...to help in oilspill con-
tingency planning." We recommend more comprehensive and detailed offshore
surveys of marine birds. Preferably, these should be conducted by boat on
at least a monthly basis and over a carefully chosen grid. Such surveys
should not be less than 2 years in duration because data from any given year
may not be representative of usual conditions and will probably not be ade-
quate for the purposes of appraising the impact of oil development on these
populations.

A useful and inexpensive way of determining the potential effect of oil
development would be to make observations from rigs to determine populations
and species composition of passing transients and to find out what effect-the
rigs have on the behavior of seabirds. (Some species, such as the boobies,
are probably attracted to these platforms, in some instances because the rigs
may be concentrating local food resources.) In areas where the erection of
oil production platforms is contemplated but where none exist nearby, surveys
by boat will probably provide more useful information most rapidly.

International borders are biologically imaginary lines that tend to dis-
tort our knowledge of the distribution of birds. The status of the marine
avifauna of the southern half of the Gulf of Mexico is virtually unknown,
even though this area may be the primary source of several pelagic species
that are common or regular in the northern Gulf. Such species (e.g., Magnif-
icent Frigatebird) spend a substantial portion of their life cycle in U.S.
waters; we need to know the year-round distribution of these species as well
as their breeding localities and their status in the nesting areas in order
to evaluate events that occur while the birds are off our shores. Some spe-
cies that are common to abundant in our offshore waters (e.g., Audubon's
Shearwater, Bridled Tern) probably come from breeding colonies in the Carib-
bean, and still other species are from breeding areas in the Arctic, Europe,
southern South America, and the Antarctic.

Although yet unproven, "foreign" birds may form a large proportion, per-
haps even a substantial majority, of the biomass of marine birds in south-
eastern waters during at least part of the year. This is certainly true if
waterfowl are included. We cannot construct elaborate plans to preserve and
protect avian species in U.S. waters if the species in question are being ex-
tirpated in their native breeding areas. It is likely that many, perhaps
most, of the Blue-faced Boobies in the Gulf of Mexico come from a small cay
off Yucatan some 45 mi (75 km) from the wellhead of the IXTOC I oil spill,
the largest oil spill in history. To our knowledge, this colony was not ex-
amined after the spill.

It would seem the wiser course to know the extent of our wildlife re-
sources before attempting to manage them. We strongly recommend that more
extensive efforts be made to initiate cooperative international surveys of
marine bird populations because marine birds are probably the most cosmopol-
itan of all avian groups. International surveys would not only supply a much
better understanding of the overall status of the species involved, but would
also permit far better insight into the consequences of local managerial de-
cisions on a species throughout its range. Previous efforts along these

lines, particularly with respect to Canada and waterfowl, have been highly
effective in producing the information needed to manage anatid populations.
Similar efforts would also prove fruitful with regard to other taxa of marine
birds.

DISTRIBUTION AND STATUS OF TRANSIENT AND WINTERING INSHORE POPULATIONS

The status and distribution of the transient and wintering inshore popu-
lations is of great importance to planners of oil development in the south-
eastern U.S. and the Gulf of Mexico. Large aggregations of birds are present
at times of year when the climate makes them most susceptible to damage from
oil pollution in coastal areas most likely to be threatened by oil spills.

In this report we document the temporal occurrence of rare species occur-
ring in the southeast, but often little or no information is available for
abundant species that may sometimes provide the bulk of the biomass for mi-
grant or wintering marine birds. Seldom are any useful data available for
estimating the size of these populations, and we do not have reliable infor-
mation on where and when large concentrations may be found. Periods when
transients occur at peak abundance in various areas along the coast are only
generally understood and very little is known of local movements by wintering
populations, whether these be movements to and from roosting and feeding
areas or movements within an area over a more extended period of time. A
better knowledge of the breeding areas from which these large wintering and
transient populations derive, and a more complete awareness of the routes
they follow are also needed for satisfactory management of these wildlife
resources.

Morgan (1980) points out that studies based on banded birds give only
the date and localities where the birds were banded and recovered. The infor-
mation reveals nothing of the pattern of movement of individual populations
in the interim; consequently, we strongly recommend a mass marking program
that involves tagging, staining, or bleaching and banding large numbers of
marine birds. By marking birds from different breeding colonies with differ-
ent colors we might discern which would be most affected by oil pollution in
the southeast. Such a program would also provide useful information about
the timing and size of migration from and through different parts of this
area. Pertinent data on local movements and foraging areas and ranges could
also be obtained simultaneously. If this were done in conjunction with a
program of mass marking of breeding and nonbreeding colonial birds within
the southeast, we could obtain additional valuable insight into the consti-
tution of transient and wintering populations.

Perhaps only three of the species treated in this volume are amenable to
such an approach. One of these is the White Pelican, which nests in a limited
number of colonies and winters in considerable numbers along the Gulf Coast
and in Florida. Another is the Magnificent Frigatebird, that occurs in the
thousands in southeastern waters, but whose area of origin is unknown. A
third species, abundant during migration and winter, and also vulnerable to
to oil pollution, is the Double-crested Cormorant. Peak abundance occurs
when the local race is augmented by large numbers of migrants arriving from

the north. The proportion of local breeders in any wintering population is
unknown because of problems in field identification and it is unclear whether
or how different forms partition the same environment.

The status of several other species that winter inshore is poorly under-
stood and needs elaboration. The loons and grebes, all highly vulnerable to
oil pollution, are probably the species most threatened from oil in the south-
eastern United States. Among the four species that are regular to abundant
in at least some part of the marine waters of the southeast, two (Common Loon
and Eared Grebe) are "blue-listed" (Arbib 1979); i.e., they are thought to be
declining in all or part of their range. Two other species (Red-necked Grebe
and Western Grebe) are rare to uncommon and are also on the Blue-list; the
Western Grebe breeds only in North America. Because these species are poten-
tially threatened or endangered, survey and census of their populations fol-
lowed by continued monitoring would seem worthwhile. A more accurate deter-
mination of critical periods of migration and areas of concentration also
seems desirable.

RESEARCH NEEDED ON EFFECTS OF OIL ON SOUTHEASTERN MARINE BIRDS

It is our firm opinion that attempted rehabilitation of oiled birds
following a major pollution incident is largely a waste of time, money, and
other resources. As Philip Stanton (1977) of the Wildlife Rehabilitation
Center put it, "the time has come for the public to realize that cleaning,
rehabilitating, and returning oil-covered birds to the wild is often not the
wisest investment of their tax dollar." The group working on ecological re-
search on seabirds on the other side of the Atlantic is evidently of the same
opinion, stating that "since the results of attempts to rehabilitate oiled
birds are so poor, it may be more profitable to expend efforts at preventing
birds from becoming polluted" (NERC 1977).

We consider it desirable however, to salvage these birds to find out
precisely what birds were oiled and to obtain information that will allow for
more prudent responses to future spills. Although there have been many major
efforts to "save" oiled birds, these have resulted in little information that
would aid in planning responses to subsequent incidents. On the other hand,
there have been exceedingly few instances in which any systematic attempt has
been made to determine the full effects of a spill on local populations of
marine birds. As Nelson (1977) stated, "documentation of the effects of the
spill is a vital postspill responsibility"; consequently, we recommend that
every attempt be made to determine which species were affected and how many
of each species died.

Obtaining this information is not easy. Even if some notion is obtained
regarding which species were oiled by a given spill, counts of dead or contam-
inated birds (or both) may not indicate how severely a species was affected.
One reason is that there is seldom adequate information on the number of birds
that were present in an area before contamination. As a result, even a rela-
tively accurate estimate of the number of birds killed will not reveal how
badly local populations may have been damaged.

Assuming that the populations of each species inhabiting an area that
becomes oiled were known, it would still be difficult to predict how many
birds may be or were affected. For example, the time of passage of an oil
slick through an area may be critical in determining the degree of contami-
nation and mortality experienced by each species. During the contamination
of the Firth of Forth in February 1978, the oil apparently passed near the
main feeding area for waterbirds at night; consequently, there was a propor-
tionately greater loss of night feeding Greater Scaup and Pochard (Aythya
ferina) than there was of Common Goldeneye and Common Eider, most of which
had moved elsewhere to roost (Campbell et al. 1978).

The proportion of birds found oiled or dead after a pollution incident
also may vary widely between species, depending on the habitats used and the
habits of the birds. The probability of finding most oiled birds that roost
or loaf onshore but near their offshore feeding areas is certainly much
greater than it is for finding those that spend all or most of their time
offshore and that, following oiling, might simply sink from sight never to
be seen again.

Further, wind and current patterns offshore as well as movements by the
birds themselves could take most of the victims of an oil spill far from where
they were oiled long before anyone noticed their plight. Levy (1980) analyzed
the sort of oil found on dead or moribund birds in Atlantic Canada and sug-
gested that Herring and Great Black-backed gulls obtained near Sable Island,
Nova Scotia, had been contaminated by oil from the ARGO MERCHANT spill on Nan-
tucket Shoals, some 840 km (522 mi) away. In another instance a badly oiled
Pochard flew 7 km (4.4 mi) inland before becoming incapacitated (Campbell et
al. 1978).

In some parts of Europe and on the west coast of the United States, pre-
vailing winds bring victims of oiling to shore. On the Atlantic Seaboard, in
contrast, winds take oiled birds out to sea. It is impossible to make a sat-
isfactory comparison of the extent of damage from oil pollution incidents
between these areas. Likewise, estimates of mortality from beached bird sur-
veys in Europe cannot be used to predict the incidence of mortality along the
western coasts of the Atlantic. At best, they only suggest that damage to
wild birds from oil on the U.S. east coast may be underestimated.

Despite all these difficulties in obtaining unbiased data, we would
still recommend that a better effort be made to monitor and publish reports
of the effects of oil spills on marine birds. Much of the information needed
to answer questions relating to oil pollution and marine birds in the south-
eastern United States would be available if such efforts had been made in the
past.

We also recommend that more attention be paid to monitoring the long term
and background effects of oil pollution in the southeast. One of the better
and less expensive ways in which this may be accomplished would be a periodic
censusing of birds found dead along the beaches. This lends some objective
basis to speculations about the effects of oil pollution on marine birds, and
also provides information about unusual or increasing mortality from other
causes (e.g., pesticides). Over time, this may serve as an early warning in-

dictator of where serious problems in wildlife conservation might arise. Such
surveys are being conducted presently in the eastern United States by the At-
lantic and Gulf Coast Beached Bird Survey Project, but the area covered in
some regions (e.g., 2 mi of the Texas coast [Simons, pers. comm.]) is so small
that the information obtained may have little importance.

Many of the biases previously discussed above, in regard to oil spills,
may also be applied to censuses of beached birds. An increasing rate of mor-
tality resulting from another source, such as pesticides, might lower relative
incidence rates for oiling and thus obscure patterns of mortality from that
source. Nevertheless, changes in the number of individuals of a species found
dead, and in the incidence and degree of oiling from year to year, should pro-
vide far more of the information needed to make decisions that would prevent
or palliate deteriorating environmental conditions. Bourne (1979b) recently
criticized North American work on marine birds and oil pollution (although
not challenging the validity of the research per se), stating that ".....work
on oil pollution, which is a simple issue of documenting the effects of human
carelessness, is wandering off in search of obscure biochemical effects unde-
tectable in nature which appear to be significant mainly as an excess for work
in laboratories....". We do not entirely concur with his viewpoint, but we
do feel that relatively more emphasis should be placed on determining the
extent of the oil pollution problem than on discovering how it is caused.

ACKNOWLEDGMENTS

Many people have contributed to this report in a variety of ways. Gene
W. Blacklock allowed us to use his unpublished manuscript on the occurrence
and status of the birds of Padre and Mustang Islands and supplied us with un-
published material on the Texas Colonial Waterbird Census. Lovett E. Williams
also supplied us with unpublished information on Florida birds, as did William
B. Robertson, Jr. and Herbert W. Kale, II. Charles D. Duncan gave us access
to unpublished data on distribution of marine birds in the Gulf of Mexico.
We much appreciate their contributions.

We are also grateful to Malcolm M. Simons, Jr., Director of the Atlantic
and Gulf Coast Beached Bird Survey Project, who supplied us with unpublished
data on incidence of oiling and mortality on birds along the Atlantic and
Gulf coasts.

The library staff of the Smithsonian Natural History Museum was especial-
ly helpful in obtaining copies of most of the theses and many of the papers
that make up the files upon which this and the companion reports are based;
Carolyn S. Hahn, Amy E. Levin, and Jack F. Marquardt were unusually helpful
in this regard. Agnes C. Nalley also aided us in finding and obtaining lit-
erature in the Bird Library of the Gabrielson Laboratory of Patuxent National
Wildlife Research Center.

Linda A. Hollenberg helped assemble species bibliographies and the lit-
erature files and Robin White provided some useful and much-needed editing.
Initial versions of the maps were prepared by Martha B. Hays and completed

by the staff of the National Coastal Ecosystems Team, Slidell, Louisiana;
much painstaking typing of preliminary and final draft material was accom-
plished by Gwynn S. Leonard and Helen L. Harbett. We thank William C. White
whose technical knowledge was of great help in the production of this report.
Illustrations interspersing the text were prepared by Charlotte I. Adamson.
We thank all for their efforts.

Others supplied unpublished manuscripts or copies of papers, journals,
or reports that would have otherwise been very difficult to obtain and often
provided guidance on areas where additional information could be acquired.
Others read and made valuable comments on preliminary versions of the manu-
script. For these and other services, we thank David G. Ainley, W. R. P.
Bourne, Francine G. Buckley, Danny Bystrak, W. Frank Cobb, Jr., Elisabeth
Cummings, R. Michael Erwin, Patrick J. Gould, Craig S. Harrison, Jerome A.
Jackson, Cherry Keller, M. Kathleen Klimkiewicz, Mary K. LeCroy, David S.
Lee, Jim Lewis, Peter J. Morgan, Steven A. Nesbitt, Storrs L. Olson, Ralph S.
Palmer, Jill Parker, Emilie Payne, Allan R. Phillips, Chandler S. Robbins,
Ralph W. Schreiber, Larry R. Shanks, David M. Smith, George E. Watson, III,
Claudia P. Wilds, David B. Wingate, Donald W. Woodard, and Richard L. Zusi.

RED-THROATED LOON

(Gavia stellata)

[DA: Rodstrubet Lom, DU: Roodkeelduiker, EN: Red-throated Diver, FI: Kaakkuri,
FR: Plongeon catmarin, GE: Nordseetaucher, Sterntaucher; IC: Lomur, IT: Stro-
laga minor, JA: Abi, NW: Smalom, PO: Nur rdzawoszyi, PR: Mergulhao, RU: (Red-
cropped Loon), SP: Somorgujo Garganta Roja, Colimbo chico; SW: Smalom]

GENERAL DISTRIBUTION

North America The Red-throated Loon breeds on Arctic tundra from Labra-
dor to western Alaska, including all of the major Canadian Arctic islands, the
major islands of the Aleutians, and Kodiak Island south to northern Vancouver
Island. It winters south on the Pacific coast to northern Baja California,
and on the Atlantic coast commonly to North Carolina and uncommonly to Florida
(Pearse 1946, AOU 1957, Palmer 1962). It is distinctly uncommon in the Gulf
of Mexico, but has been recorded in all the southeastern United States bor-
dering the gulf.

World Distribution The breeding distribution is holarctic, primarily in
tundra lakes and ponds. In the Palearctic this loon breeds in coastal Green-
land, Iceland, Spitzbergen, Franz Joseph Land, the Faroes, Orkneys, and Shet-
lands, in northern Scotland, northwestern Ireland, most of Norway, Sweden, and
Finland, and in the U.S.S.R. from the Gulf of Bothnia east across northern
Russia and Siberia to Kamchatka and Sahkalin Island. It winters south in
Europe to Spain and Portugal, sparsely in the Mediterranean, in the Black Sea,
and on the Pacific coast of Asia south to Hainan Island (AOU 1957, Palmer 1962,
Cramp et al. 1977).

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

Red-throated Loons are common in winter on the Carolina coasts, fairly
common on the Georgia coast, and uncommon on the Atlantic coast of Florida
(Map 1). They are very uncommon in the Gulf of Mexico, but have been recorded
in all the Gulf States.

North Carolina Red-throated Loons are common winter residents in salt-
water areas but are rare inland. Occasionally, large concentrations are re-
ported, such as the 500 seen from the ferry between Ocracoke and Cedar islands,
30 November 1974 (Teulings 1975a). There are a few records of summering birds
(Teulings 1970b, 1971d, 1972a, 1973d). Fall migration seems to be primarily
in late October and November (Teulings 1971a, 1973a, 1974a, 1976a).

South Carolina Red-throated Loons are common in winter. A concentration
of "over 1,000 Red-throated Loons were counted" at the mouth of the Edisto
River, Charleston County, 10 March 1962 (Burton 1970). They are recorded in-
land only occasionally (Sprunt and Chamberlain 1949, Burton 1970).

Winter Distribution Map for --- I nu-InnuRIEU LUun
Southeastern United States / 4 '
BIRDS PER 10 PARTY-HOURS
E Less than 0.1 S
0.1-0.5 L- 0 _
0.5-2
More than 2 .-,
(Adapted from Bystrak, 1974) 1 ---
INDIVIDUALS OBSERVED DURING
CHRISTMAS BIRD COUNTS, 1973-1977
(ARITHMETIC MEAN) i
(c Number of individuals .__ ---
O Less than one individual --- FAYETTEVILLE s-01C0IK
SNone observed T

013

DALLAS 2

T E X A S

Georgia Burleigh (1958) called the Red-throated Loon a "rare winter vis-
itant", but his estimates of seabird abundance on the Georgia coast are uni-
formly lower than those of others to the north and south. Denton et al.
(1977) called it fairly common in winter. In recent years, there have been
several reports of migrants inland (Teulings 1973a, 1974a, 1976a).

Florida Atlantic Coast This loon is uncommon but regular on the Atlan-
tic coast of Florida (Sprunt 1954, Stevenson 1978, Kale 1979 ms a). It is
casual on the Florida Keys (Edscorn 1978, Stevenson 1978, 1979).

Florida Gulf Coast Red-throated Loons are much rarer on the west coast
of Florida than on the east coast. There have been about eight reported on
or near the Gulf coast since 1970 (Stevenson 1975, 1977, 1978; Hamilton 1976).

Alabama Imhof (1976b) called Red-throated Loons "rare" in winter in
Alabama on the basis of about 16 sight records, and gave extreme dates of
1 November and 1 May. Purrington (1977) and Imhof (1978) provide additional
records.

Mississippi The status of Red-throated Loons in Mississippi seems to be
similar to that in Alabama, i.e., a rare winter visitor. There are now eight
records for the state (Hamilton 1979).

Louisiana Lowery (1974) listed four Louisiana records, all in the period
from December to March.

Texas The Red-throated Loon is decidedly rare in Texas. Oberholser
(1974) listed four specimens and sight records for 13 locations (multiple
sightings at some localities are probable). In recent years, this bird has
appeared nearly every year at a few favored localities, notably the Texas
City Dike, Galveston County, and Rockport and Aransas Pass, Aransas County
(Webster 1970b, 1971c, 1974b, 1975b, 1976b, 1976c, 1977b).

SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE

Breeding Red-throated Loons breed on the shores of small lakes and ponds
across the tundra of North America, Eurasia, Greenland, Iceland, and Spitz-
bergen, as well as in Scotland, the Faroes, and the Aleutian Islands. Their
breeding range extends south into boreal forest areas in western North America
and probably elsewhere. Estimates of the world population are not available.

Winter Red-throated Loons winter along coasts from the southern portions
of their breeding range south to Baja California and Hainan Island in the Pa-
cific, to the Florida Keys and the Iberian Peninsula in the Atlantic, and to
the Baltic, Black, and northern Mediterranean seas (Cramp et al. 1977).

Migration The main migration route for Red-throated Loons wintering in
the southeast is along the Atlantic coast (Palmer 1962). The route taken by
the small numbers wintering in the Gulf is unknown. Scattered records inland
along the Mississippi River suggest there may be a very limited overland mi-
gration. These loons begin arriving off South Carolina by mid-October and

are off Florida by mid-November. Departure from the latter area occurs in
late March and April (Palmer 1962).

HABITAT

Nesting Red-throated Loons breed on freshwater lakes and ponds, usually
in treeless areas (Cramp et al. 1977), although Pearse (1946) described a nest
site in forested terrain. They can use smaller ponds than other loons, and
may even breed on ponds of less than I ha (Bundy 1976). The nest is placed
in grass, sedges, or other low vegetation along the margin of an island or
along the shore of a pond or lake (Bundy 1976, Petersen 1976).

Feeding Red-throated Loons breeding on small ponds fly to larger bodies
of fresh or saltwater to feed. At other times of year they feed in ponds,
lakes, estuaries, and nearshore areas of the oceans. They probably restrict
themselves to waters where they can dive to the bottom.

Winter and Offshore These loons winter almost exclusively on saltwater,
and are found inland much less frequently than other loons (Palmer 1962). A
majority of the inland records from the southeast appear to be of transients.
Red-throated Loons tend to occupy shallower water in winter than Arctic or
Common loons (Palmer 1962, W. Hoffman pers. observe ) but they probably move
to deeper areas of bays and inlets at night.

FOOD AND FEEDING BEHAVIOUR

Red-throated Loons mainly eat fish. Cramp et al. (1977) listed their
foods as a variety of pelagic (cod, herring, sprat), demersal gobiess, stickle-
backs), and benthic (flounders, sculpins) marine fishes, in addition to such
freshwater fish as trout, roach (Rutilus), dace, and perch. In Arctic Canada,
Davis (1972) reported that food brought to young birds included capelin, blen-
nies (Lumpenus), sand lances (Ammodytes), trout, and sculpins. Cramp et al.
(1977) also listed fish spawn, frogs, crustaceans, molluscs, insects, and
annelids in the diet.

Red-throated Loons feed primarily by pursuit diving. Their feet and oc-
casionally their wings are used for propulsion (Cramp et al. 1977). They
occasionally feed on the surface where they seize their prey.

IMPORTANT BIOLOGICAL PARAMETERS

Egg Laying In western Alaska (Petersen 1976) and Quebec (Johnson and
Johnson 1935), egg laying took place from late May into June. In the Shetland
Islands, Bundy (1976) reported laying from mid-May to mid-June, 1973-74.

Mean Clutch Size Most nests of the Red-throated Loon contain two eggs,
although one or three eggs are sometimes found. In 63 nests in the Shetlands,
Bundy (1976) reported a mean of 1.8 eggs. In a 3 year study (1967-69) on the
McConnell River, Northwest Territories, Davis (1972) found that the annual

SUSCEPTIBILITY TO OIL POLLUTION

Loons are highly susceptible to oiling, although they are often poorly
represented on beached bird counts. Tanis and Morzer Bruyns (1968) reported
seeing hundreds of oiled Red-throated Loons in the North Sea "sinking irre-
trievably at sea", but very few of them washed up on the adjacent beaches.
They have appeared in small numbers in oiled bird counts from European and
American beaches (Table 5). More may be oiled than this table indicates be-
cause most reports of oiling combine the several species of loons under one
heading.

Peterson (1942) reported four oiled Red-throated Loons from Oregon Inlet,
North Carolina, early in World War II when German submarines sank ships that
subsequently spilled oil.

King and Sanger (1979) give an Oil Vulnerability Index of 49 to this spe-
cies, indicating that they considered these loons a "mid-risk" species in the
Pacific Northwest.

Table 5. Number of dead birds and number and percentage of dead Red-
throated Loons found after major oiling incidents.

Number
Number of dead Percentage
of oiled Red- of Red-
dead throated throated
Area Dates birds Loons Loons Source

San Francisco Bay
area, California

Island Beach,
New Jersey

Mar. 1937

Jan. 1945

North-central Kat- Jan.-Feb.
tegat, Denmark 1962

Southeast Kent,
England

N. Sjaelland,
Denmark

North Sea coast,
Denmark

winters of
1963-64 to
1965-66

Feb.-Mar.
1965

1965-1966

Northeast England Jan. 1966

397 (a) 14 3.53 Aldrich
1938

92 (b) 10 10.87 Kramer and
Kramer 1945

1,723 (a,b) 6 0.35 Joensen
1972a

509 (a) 10 1.96 Gibson
1966

2,340 (a) 44 1.88 Joensen
1972a

803 (a) 43 5.35 Joensen
1972a

12 1.49 Parrack
1967

Table 5. Continued.

Number
Number of dead Percentage
of oiled Red- of Red-
dead throated throated
Area Dates birds Loons Loons Source

Pagham Harbour Jan.-Feb. 91 (a,c) 2 2.20 Phillips
area, W. Sussex, 1967 1967
England

Tay Estuary, Scot- Mar.-Apr. 1,168 (c) 6 0.51 Greenwood
land 1968 and Keddie
1968

N. Sealand, Feb.-Mar. 2,376 (a) 1 0.04 Joensen
Denmark 1969 1972b

Northeast Britain Jan.-Feb. 10,992 (a,b) 69 0.63 Greenwood
1970 et al. 1971

S. Kattegat, Den- Dec. 1970- 2,311 (a) 1 0.04 Joensen
mark Jan. 1971 1972b

San Francisco Jan. 1971 3,221 (a,c) 64 1.99 Smail et
Bay, California al. 1972

Djursland-Anholt, Mar. 1971 239 1 0.42 Joensen
Denmark 1972b

North-central Mar. 1972 4,759 (a) 26 0.55 Joensen and
Kattegat, Denmark Hansen 1977

Waddensea, Den- Dec. 1972 9,151 (a) 23 0.25 Joensen and
mark Hansen 1977

(a) Total includes only those birds identified to species.
(b) Total includes some birds that were not oiled.
(c) Total includes both live and dead oiled birds.
(d) This figure represents birds brought to cleaning/receiving stations.

BIBLIOGRAPHY

1980

Reimchen, T. E. and S. Douglas. 1980. Observations of loons (Gavia immer
and G. stellata) at a bog lake on the Queen Charlotte Islands. Can.
Field Nat. 94: 398-404.

1978

Bundy, G. 1978a. Possible polygamy by Red-throated Divers. Brit. Birds 71:
179-181.

Bundy, G. 1978b. Breeding Red-throated Divers in Shetland. Brit. Birds 71:
199-208.

Merrie, T. D. H. 1978. Relationship between spatial distribution of breeding
divers and the availability of fishing waters. Bird Study 25: 119-122.

Weber, W. C. 1978. Red-throated Loon sightings on Ship and Horn islands,
Mississippi. Mississippi Kite 8: 10-11.

1977

Bergman, R. D. and D. V. Derksen. 1977. Observations on Arctic and Red-
throated loons at Storkersen Point, Alaska. Arctic 30: 41-51.

1976

Bundy, G. 1976. Breeding biology of the Red-throated Diver. Bird Study 23:
249-256.

Muller, H. 1976. "Wasserlugen" beim Sterntaucher (Gavia stellata) sowie
allgameine Bemerkungen zum "Wasserlugen." Vogelwelt 97: 68-71. [In
German.]

Norberg, R. A. and U. M. Norberg. 1976. Size of fish carried by flying Red-
throated Divers Gavia stellata (Pont.) to nearly fledged young in nesting
tarn. Ornis Fenn. 53: 92-95.

Petersen, M. R. 1976. Breeding biology of Arctic and Red-throated loons.
M. S. thesis, Univ. Calif./Davis. 55 pp.

Sage, B. L. 1976. Breeding success of Red-throated Divers on Hascosay.
Brit. Birds 69: 409.

1975

Cyrus, D. P. 1975. Breeding success of Red-throated Divers on Fetlar. Brit.
Birds 68: 75-76.

Falk, L. F. 1975. Loons on Middle Atlantic Region Christmas counts. Del-
marva Ornithol. 10: 9-11.

Gloe, P. 1975. Feindverhalten von Sterntauchern (Gavia stellata) ausserhalb
der Brutzeit an Land. Ornithol. Mitt. 27: 215-217. [In German.]

1974

Jakobs, B. and M. Jakobs. 1974. Zum Verhalten des Sterntauchers (Gavia
stellata) am Nest. Ornithol. Mitt. 26: 169-172. [In German.]

44

1973

Meltofte, H. and T. Korboe. 1973. [The occurrence of divers Gaviidae at
Blavand, 1963-71.] Dan. Ornithol. Foren. Tidsskr. 67: 109-114. [In
Danish with English summary.]

1972

Davis, R. A. 1972. A comparative study of the use of habitat by Arctic
Loons and Red-throated Loons. Ph. D. thesis, Univ. W. Ontario/Guelph,
ON. xix and 290 pp.

1971

Bylin, K. 1971. [Courtship and calls of the Red-throated Loon Gavia stel-
lata.] Var Fagelvarld 30: 79-83. [In Swedish with English summary.]

Davis, R. A. 1971. Flight speed of Arctic and Red-throated loons. Auk
88: 169.

Norberg, R. A. and U. M. Norberg. 1971. Take-off, landing and flight speed
during fishing flights of Gavia stellata (Pont.). Ornis Scand. 2: 55-67.

1968

Lindberg, P. 1968. Nagot om Storlommens (Gavia arctica L.) och Smalommens
(Gavia stellata L.) ekologi. [On the ecology of the Black-throated
Diver (Gavia arctica) and the Red-throated Diver (Gavia stellata).]
Zool. Revy 30: 83-88. [In Swedish with English summary.]

Simkin, D. W. 1968. Red-throated Loon nesting in northern Ontario. Can.
Field Nat. 82: 49.

von Braun, C., A. C. Hessle and S. Sjolander. 1968. Smalommens (Gavia stel-
lata L.) beteende under ungvardnadstiden. [Behavior of the Red-throated
Diver (Gavia stellata L.) when caring for the young.] Zool. Revy 30:
94-95. [In Swedish with English summary.]

1966

Hall, A. B. and G. P. Arnold. 1966. Brief observations on a pair of Red-
throated Divers (Gavia stellata) nesting in East Greenland. Dan. Orni-
thol. Foren. Tidsskr. 60: 141-145. [In English with Danish summary.]

1956

Sutton, G. M. and D. F. Parmalee. 1956. On the loons of Baffin Island.
Auk 73: 73-84.

1954

Pearse, T. 1954. Further notes on Red-throated Loons nesting on Vancouver
Island, British Columbia. Condor 56: 308-309.

45

1952

Gudmundsson, F. 1952. Islenzkir fuglar II. Lomur (Colymbus stellatus Pon-
topp.). [Icelandic Birds II. The Red-throated Diver (Colymbus stellatus
Pontopp.)]. Natturufraedingurinn 22: 76-77. [In Icelandic with English
summary.]

Harle, D. F. 1952. Red-throated Diver taking off from the ground. Brit.
Birds 45: 331-332.

1946

Pearse, T. 1946. The nesting of the Red-throated Loon on Vancouver Island,
British Columbia. Condor 48: 262-264.

1941

Brandt, M. 1941. Uber das Brutvorkommen der Silbermowe (Larus argentatus
omissus) und des Sterntauchers (Colymbus stellatus) im Ostbaltikum.
J. Ornithol. 89: 257-267. [In German.]

1940

Brandt, M. 1940. An den Brut staten des Nordseetauchers in Lettland. Beitr.
Fortpfl. Vogel 16: 135-139. [In German.]

1937

Keith, D. B. 1937. The Red-throated Diver in North East Land. Brit. Birds
31: 66-81.

1935

Johnson, R. A. and H. S. Johnson. 1935. A study of the nesting and family
life of the Red-throated Loon. Wilson Bull. 47: 97-103.

Serle, W., Jr. 1935. Mortality amongst young Red-throated Divers. Brit.
Birds 29: 181-182.

1934

Vasvari, N. 1934. Die Bedeutung der Magensteine (Gastrolithe) bei den See-
tauchern (Columbus). [The importance of gastroliths in the divers (Col-
ymbus)]. Proc. VIIIth Intern. Ornithol. Congr., Oxford 1934: 730-743.
[In German.]

1931

McWilliam, J. M. 1931. On the breeding of the Black-throated and Red-throated
divers in south Argyllshire. Scott. Nat. 1931: 161-164.

1929

Stevenson, J. 1929. Red-throated Loon in northern Illinois. Auk 46: 529.

1923

Huxley, J. S. 1923. Courtship activities in the Red-throated Diver (Colym-
bus stellatus Pontopp.), together with a discussion of the evolution of
courtship in birds. J. Linn. Soc. Lond. (Zool.) 35: 253-292.

1922

van Oordt, G. J. and J. S. Huxley. 1922. Some observations on the habits
of the Red-throated Diver in Spitsbergen. Brit. Birds 16: 34-36.

ARCTIC LOON

(Gavia arctica)

[DA: Sortstrubet Lom, DU: Parelduiker, EN: Black-throated Diver, FI: Kuikka,
FR: Plongeon lumme, Plongeon arctique; GE: Polartaucher, Prachttaucher; IC:
Glitbrusi, IT: Strolaga mezzana, JA: 0-hamu, NW: Storlom, PO: Nur czarnoszyi,
PR: Mergulhao, RU: (Black-cropped or Striped Loon), SP: Somorgujo Artico,
Colimbo artico; SW: Storlom, US: Pacific Loon]

GENERAL DISTRIBUTION

North America The Arctic Loon breeds from St. Lawrence Island and Alaska
east to Baffin Island and the west coast of the Ungava Peninsula, and south
to the Alaska Peninsula, northern Mackenzie, northern Alberta and Manitoba,
and northwestern Ontario (Hudson Bay). It winters on the Pacific coast from
coastal southern Alaska to southern Baja California and Sonora (AOU 1957,
Palmer 1962, Storer 1979a). Arctic Loons are regular but rare in winter on
the New England coast (Griscom 1943), and very rare in the southeastern states.

World Distribution The form G. a. arctica breeds across Arctic Eurasia
from Scandinavia to the Lena River, where it is replaced by G. a. viridigul-
aris. The latter breeds eastward to the Bering Sea and western Alaska. The
species winters in the Baltic and on the Atlantic and North Sea coasts of
Europe from northern Norway to the Bay of Biscay, in the Adriatic, Aegean,
Black, and Caspian seas (Vaurie 1965, Cramp et al. 1977), and in the Pacific
south to Japan (Storer 1979a).

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

The Arctic Loon is a rare but perhaps regular winter visitor in the south-
east. We have substantiated records from Florida and coastal Texas. There
are also a number of sight records from Texas, two from Alabama, and one from
North Carolina. We have not listed the Texas sight records because many of
them clearly could have been small Common Loons.

North Carolina There is one sight record:

1974 17 Feb. 1 seen Ocracoke, Pamlico Co. Teulings 1974b

Florida We have four specimen records of Arctic Loons from Florida.

1959 2 Nov. 1 found dead Palm Beach, Palm Beach Langridge 1960
(USNM #431142) Co.

Taxonomic note: Some authors have treated the form G. a. pacifica of north-
eastern Siberia and North America as a distinct species, but we follow the
taxonomic treatment of Storer (1978).

1971 14 Dec.

1975 20 Apr.

1976 12 Apr.

1 coll.

1 found dead

1 found sick

Alabama There are two records:

1975 27-31 Dec. 1 seen

1977 31 Dec.

1 seen

Wakulla River, Wakulla
Co.

Dry Tortugas, Monroe
Co.

Indian Rocks Beach,
Pinellas Co.

Oak Mountain St. Park
Lake, Shelby Co.

Gulf Shores, Baldwin
Co.

Mississippi There is one sighting of a bird thought to
cies.

1976 13 Nov.

1 seen

Stevenson 1972

Kittleson 1976

Hopkins and
Woolfenden
1977

Imhof 1975b,
1977b

Hamilton 1978

be of this spe-

Sardis Lake, Sardis Co. Purrington
1977

Texas We know of one coastal Texas specimen (and one from inland) and
of about 15 sight records from the coast. Many of the latter are merely
based on size and may be misidentified Common Loons. In winter plumage,
Arctic Loons are extraordinarily difficult to distinguish from small Common
Loons, and the Texas records fail to report the characters most useful in
identification.

1963 28 Mar.

1 specimen

Rockport, Aransas Co.

HABITAT

Nesting Arctic Loons nest on lakes and ponds, usually in tundra, moor-
lands, or other essentially treeless habitat. They tend to use larger ponds
than Red-throated Loons, apparently because they are heavier bodied and need
more room for a take-off (Petersen 1976).

Feeding Arctic Loons, like other loons, feed entirely in the water. In
the breeding season they usually feed on their breeding ponds, but may move
to nearby lakes to feed (Davis 1972, Petersen 1976). In winter they move al-
most exclusively to salt water.

Winter and Offshore Wintering Arctic Loons occur in estuaries, lagoons,
and in the ocean within a few km of shore. They may range a little farther
offshore than Common or Red-throated loons (Baltz and Morejohn 1977).

Blacklock
1978 ms

FOOD AND FEEDING BEHAVIOR

Arctic Loons feed by pursuit diving and occasionally by surface-dipping.
They eat mostly fish, but also take a variety of invertebrates and occasion-
ally plant material (Palmer 1962).

SUSCEPTIBILITY TO OIL POLLUTION

Arctic Loons are vulnerable to floating oil, but their rarity within the
southeast greatly reduces the potential for significant oiling mortality in
that area. They show up regularly in small numbers on European beached bird
surveys (Table 6). Loons are not identified to species in all reports of
bird mortality resulting from oiling, and many loons are apparently carried
away by currents or sink in deep water rather than wash ashore. King and
Sanger (1979) give an Oil Vulnerability Index of 58 to this species in the
Pacific Northwest.

Table 6. Number of dead birds and number and percentage of dead Arctic
Loons found after major oiling incidents.

Number Number Percent-
of oiled of dead age of
dead Arctic Arctic
Area Dates birds Loons Loons Source

San Francisco Bay
area, California

Mar. 1937

North-central Kat- Jan.-Feb.
tegat, Denmark 1962

North Sea coast,
Denmark

TORREY CANYON (c)
oil spill, SW
Britain

Bornholm, Denmark

N. Sealand, Den-
mark

Northeast Britain

S. Kattegat,
Denmark

1965-1966

Mar. 1967

Jan.-Feb.
1968

Feb.-Mar.
1969

Jan.-Feb.
1970

Dec. 1970-
Jan. 1971

397 (a) 2 0.50

1,723 (a,b) 70 4.06

Aldrich
1938

Joensen
1972a

803 (a) 7 0.87 Joensen
1972a

1,223

466 (a)

2,376 (a)

10,992 (a,b)

2,311 (a)

1 0.08 Bourne et
al. 1967

3 0.64 Joensen
1972a

2 0.08

Joensen
1972b

3 0.03 Greenwood
et al. 1971

4 0.17 Joensen
1972b

Table 6. Continued

Number Number Percent-
of oiled of dead age of
dead Arctic Arctic
Area Dates birds Loons Loons Source

San Francisco Bay, Jan. 1971 3,221 (a,c) 21 0.65 Smail et
California al. 1972

Djursland-Anholt, Mar. 1971 239 8 3.35 Joensen
Denmark 1972b

North-central Mar. 1972 4,759 (a) 14 0.29 Joensen and
Kattegat, Denmark Hansen 1977

Waddensea, Den- Dec. 1972 9,151 (a) 4 0.04 Joensen and
mark Hansen 1977

AMOCO CADIZ spill, Mar. 1978 3,770 (a,e) 58 1.54 Hope Jones
NW France and Chan- et al. 1978
nel Islands

(a) Total includes only those birds identified to species.
(b) Total includes some birds that were not oiled.
(c) This sample is from a spill that was believed to have killed more than
30,000 seabirds.
(d) This figure represents birds brought to cleaning/recieving stations.
(e) Total includes both live and dead oiled birds.

BIBLIOGRAPHY

1980

Andersson, A., P. Lindberg, S. G. Nilsson and A. Pettersson. 1980. Stor-
lommens Gavia arctica hacknings framgang i Svenska sjoar. [Breeding
success of the Black-throated Diver, Gavia arctica, in Swedish lakes.]
Var Fagelvarld 39: 85-94. [In Swedish with English summary.]

Bruner, A. 1980. First fall record of Arctic Loon in Indiana. Indiana
Aud. Q. 58: 61-62.

Eckert, K. R. 1980. The Arctic Loon in Minnesota: a revised look at its
status and identification. Loon 52: 59-61.

Grenmyr, U. and J.-A. Sundin. 1980. Storlommens forekomst langs Norrlands-
kusten. [The number of breeding Black-throated Divers, Gavia arctica,
along the coast of North Sweden.] Var Fagelvarld 39: 100-101. [In
Swedish with English summary.]

Bundy, G. 1979. Breeding and feeding observations on the Black-throated
Diver. Bird Study 26: 33-36.

Petersen, M. R. 1979. Nesting ecology of Arctic Loons. Wilson Bull. 91:
608-617.

Tessen, D. D. 1979. Arctic Loon--Ozaukee County, November 1, 1978-4:15 p.m.
Passenger Pigeon 41: 140.

1978

Abraham, K. F. 1978. Adoption of Spectacled Eider ducklings by Arctic Loons.
Condor 80: 339-340.

Dennis, R. H. 1978. [Letter on] Field identification of Black-throated Diver
in winter. Brit. Birds 71: 225-226.

Enquist, M. 1978. Storlommons Gavia arctica beteende under varen i Bravi
ken. [Behavior of the Black-throated Diver in Braviken during spring.]
Var Fagelvarld 37: 325-332. [In Swedish with English summary.]

Faanes, C. and R. Faanes. 1978. Third Wisconsin record of the Arctic Loon.
Passenger Pigeon 40: 412-413.

Fitzpatrick, J. 1978. [Letter on] Field identification of Black-throated
Diver in winter. Brit. Birds 71: 226.

Jackson, S. 1978. [Letter on] Diving methods of Great Northern and Black-
throated divers. Brit. Birds 71: 317.

Merrie, T. D. H. 1978. Relationship between spatial distribution of breeding
divers and the availability of fishing waters. Bird Study 25: 119-122.

Nilsson, S. G. and A. Pettersson. 1978. Det svenska Storlombestandets stor-
lek. [An estimate of the population size of the Black-throated Diver
Gavia arctica in Sweden.] Var Fagelvarld 37: 251-253. [In Swedish with
English summary.]

Schipke, R. and G. Creutz. 1978. Ubersommende Prachtaucher Gavia arctica
(L.). [Arctic Loon Gavia arctica (L.).] Beitr. Vogelkd. 24: 171-173.
[In German.]

Sjolander, S. 1978. Reproductive behavior of the Black-throated Diver Gavia
arctica. Ornis Scand. 9: 51-65.

Storer, R. W. 1978. Systematic notes on the loons (Gaviidae: Aves). Brev-
iora No. 448: 1-8.

1977

Abbott, J. M. 1977. Arctic Loon at Assateague Island, Virginia, in April
1976. Raven 48: 25-26.

52

Bergman, R. D. and D. V. Derksen. 1977. Observations on Arctic and Red-
throated loons at Storkersen Point, Alaska. Arctic 30: 41-51.

Hopkins, L. and G. E. Woolfenden. 1977. Fourth record of the Arctic Loon
from Florida. Fla. Field Nat. 5: 12.

Imhof, T. A. 1977b. Arctic Loon, a new species for Alabama. Am. Birds 31:
378.

Nilsson, S. G. 1977. Adult survival rate of the Black-throated Diver Gavia
arctica. Ornis Scand. 8: 193-195.

Vermeer, K. 1977. Some observations on Arctic Loons, Brandt's Cormorants
and Bonaparte's Gulls at Active Pass, British Columbia. Murrelet 58:
45-47.

1976

Bolduc, D. 1976. Arctic Loon on Lake Harriet. Loon 48: 184-185.

Kittleson, B. C. 1976. Third record of the Arctic Loon from Florida. Fla.
Field Nat. 4: 17.

Petersen, M. R. 1976. Breeding biology of Arctic and Red-throated loons.
M. S. thesis, Univ. Calif./Davis. 55 pp.

1975

Dunker, H. 1975. Sexual and aggressive display of the Black-throated Diver
Gavia arctica (L.). Norw. J. Zool. 23: 149-163.

Gordon, S. 1975. First days in the life of a Black-throated Diver. Scott.
Birds 8: 319.

Imhof, T. A. 1975b. Arctic Loon, new species for Alabama. Ala. Birdlife
23: 16.

McNicholl, M. K. 1975. Arctic Loon "checking" nest. Auk 92: 393-394.

1974

Dunker, H. 1974a. Observasjoner av populasjonstetthet hos Storlom, Gavia
arctica L., i Rogen-omradet, ostre Femundsmarka, i 1967 og 1971. [Ob-
servations on the population density of the Black-throated Diver, Gavia
arctica L., in the Rogen Area, eastern Femundsmarka, in 1967 and 1971.7
Fauna 27: 11-16. [In Norwegian with English summary.]

Dunker, H. 1974b. Habitat selection and territory size of the Black-throated
Diver, Gavia arctica (L.), in South Norway. Norw. J. Zool. 22: 15-29.

Hatler, D. F. 1974. Bald Eagle preys upon Arctic Loon. Auk 91: 825-827.

Lehtonen, L. 1974. Zur individuellen Erkennung des Prachttauchers Gavia a.
arctica im Brutklied. Ornis Fenn. 51: 117-121. [In German with English
summary.]

McIntyre, A. E. and J. W. McIntyre. 1974. Spots before the eyes, an aid to
identifying wintering loons. Auk 91: 413-415.

Robertson, I. and M. Fraker. 1974. Apparent hybridization between a Common
Loon and an Arctic Loon. Can. Field Nat. 88: 367.

Schuz, E. 1974. Uber den Zug von Gavia arctica in der Palaarktis. Ornis
Fenn. 51: 183-194. [In German with English summary.]

1973

Arnold, K. A. and J. C. Henderson. 1973. First specimen of Arctic Loon from
Texas. Auk 90: 420-421.

Dunker, H. and K. Elgmork. 1973. Nesting of the Black-throated Diver, Gavia
arctica (L.) in small bodies of water. Norw. J. Zool. 21: 33-37.

1972

Davis, R. A. 1972. A comparative study of the use of habitat by Arctic Loons
and Red-throated Loons. Ph. D. thesis, Univ. W. Ontario/Guelph, ON. xix
and 290 pp.

Hohn, E. 0. 1972. Arctic Loon breeding in Alberta. Can. Field Nat. 86: 372.

Schwilling, M. D. 1972. Arctic Loon taken from Wilson Reservoir. Kansas
Ornithol. Soc. Bull. 23: 13-14.

1971

Carlson, C. W. 1971. Arctic Loon at Ocean City, Maryland. Md. Birdlife 27:
68-72.

Davis, R. A. 1971. Flight speed of Arctic and Red-throated loons. Auk 88:
169.

Easterla, D. A. and F. Lawhon. 1971. First specimen of Arctic Loon from
Missouri. Auk 88: 175.

Pynnonen, A. 1971. On the interspecific aggressiveness of the Black-throated
Diver Gavia arctica. Ornis Fenn. 48: 133-134.

1970

Jones, R. N. and M. Obbard. 1970. Canada Goose killed by Arctic Loon and
subsequent pairing of its mate. Auk 87: 370-371.

Lehtonen, L. 1970. Zur Biologie des Prachttauchers, Gavia a. arctica (L.).
[Biology of the Black-throated Diver, Gavia a. arctica (L.).] Ann. Zool.
Fenn. 7: 25-60. [In German with English summary.]

Peck, G. K. 1970. First Ontario nest records of Arctic Loon and Snow Goose.
Ont. Field Biol. 24: 25-28.

1968

Butler, R. W. 1968. Display of Black-throated Divers on sea. Brit. Birds
61: 224-226.

Lindberg, P. 1968. Nagot om Storlommens (Gavia arctica L.) och Smalommens
(Gavia stellata L.) ekologi. [On the ecology of the Black-throated Diver
(Gavia arctica L.) and the Red-throated Diver (Gavia stellata L.).]
Zool. Revy 30: 83-88. [In Swedish with English summary.]

Sjolander, S. 1968. Iakttagelser over Storlommens (Gavia arctica L.) etol-
ogi. [Observations on the ethology of the Black-throated Diver (Gavia
arctica L.).] Zool. Revy 30: 89-93. [In Swedish with English summary.]

1967

Lensink, C. J. 1967. Arctic Loon predation on ducklings. Murrelet 48: 41.

1965

Easterla, D. A. 1965. Arctic Loons invade Missouri. Condor 67: 544.

Lehtonen, L. 1965. [On the migration and the occurences at the beginning of
the breeding season of Gavia arctica.] Ornis Fenn. 42: 76-89. [In Fin-
nish with German summary.]

1960

Langridge, H. P. 1960. Arctic Loon at Palm Beach. Auk 77: 351.

1956

Sutton, G. M. and D. F. Parmalee. 1956. On the loons of Baffin Island.
Auk 73: 78-84.

1955

England, M. D. 1955. Unusual nest of Black-throated Diver. Brit. Birds
48: 276.

1954

Schuz, E. 1954. Vom Zug der westsibirischen Population des Prachttauchers
(Gavia arctica). Vogelwarte 17: 65-80. [In German.]

1950

Grote, H. 1950. Zur Kenntnis des Prachttauchers (Colymbus arcticus L.).
[Breeding biology of Gavia arctica L.] Zool. Garten 17: 87-90. [In
German.]

1948

Robinson, M. G. 1948. Behavior of Black-throated Diver. Brit. Birds 41: 27.

1947

Thomson, J. M. 1947. The display of the Black-throated Diver. Brit. Birds
40: 90.

1944

Bodenstein, G. and E. Schuz. 1944. Vom Schliefenzug des Prachttauchers.
Ornithol. Monatsber. 52: 98-105. [In German.]

1943

Griscom, L. 1943. Notes on the Pacific Loon. Bull. Mass. Audubon Soc. 27:
106-109.

Pennie, I. D. 1943. Display of a Black-throated Diver. Brit. Birds 37: 18.

1938

Kleinschmidt, 0. 1938. Irisfarbe und Federwechsel der alten Prachttaucher.
[Iris color and molting of an old Artic Loon.] Falco 34: 11-12. [In
German.]

Vasvari, N. 1938. Die Bedeutung der Magensteine (Gastrolithe) bei den See-
tauchern (Colymbus). [The importance of gastroliths in the divers (Col-
ymbus).] Proc. VIIIth Internatl. Ornithol. Congr., Oxford 1934: 730-743.
[In German.]

1931

McWilliam, J. M. 1931. On the breeding of the Black-throated and Red-throated
divers in south Argyllshire. Scott. Nat. 1931: 161-164.

1925

Lonnberg, E. 1925. Nagra ord om Storlommen och dess slaktinger. [The Arctic
Loon and its relatives.] Fauna Flora 1925: 3-9. [In Norwegian.]

1924

von Zedlitz, 0. G. 1924. Aus der Kinderstube schwedischer Brutvogel. Beitr.
Fortpfl. Biol. Vogel. 1: 4-6. [In German.]

56

1922

von Zedlitz, 0. G. 1922. Ein Beitrag zur Bilolgie von Co arctics.
[A contribution to the life history of C b arcticus.] J. Ornithol.
70: 419-423. [In Gemane 1

1913

von Zedlltz, 0. G. 1913. Ein Bietrag zur Biologie des Prachttauchers, Urin-
ator arcticus L. [A contribution to the biology of the Black-throated
Diver, Gavia arctica L.] J. Ornithol. 61: 178-188. [In Geran.]

Oiled Comon Loon on beach, Beacon Island, North Carolina.
Photograph by R. B. Clapp.

57

COMMON LOON

(Gavia immer)

[DA: Islom, DU: IJsduiker, EN: Great Northern Diver, FI: Amerikan jaakuikka,
FR: Plongeon imbrin, GE: Eistaucher, IC: Himbrimi, IT: Strolage maggiore,
NW: Islom, PO: Nur lodowiec, PR: Mergulhao, RU: (Arctic Loon), SP: Somorgujo
Comun, Colimbo grande; SW: Islom, US: Black-billed Loon]

GENERAL DISTRIBUTION

North America Common Loons breed in Arctic and boreal areas from Alaska
and northern Canada south to northern New England, the Great Lakes region,
Minnesota, Washington, and casually to California. They are absent from most
of the Canadian Arctic islands, but do breed on Baffin Island.

They winter mainly in coastal areas. In the Pacific, they winter from
the Aleutians east and south to northern Baja California, and in the Atlantic
from Labrador south to Florida and Texas. They occur much less commonly in-
land on large lakes and rivers (AOU 1957, Palmer 1962).

World Distribution In addition to their North American range, Common
Loons breed in much of coastal Greenland and throughout Iceland. They winter
in coastal Europe from Lapland south through the North Sea, around the Brit-
ish Isles to Spain and Portugal, to the Atlantic coast of Morocco, and to the
Azores (Vaurie 1965, Cramp et al. 1977).

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

Common Loons winter along the Atlantic and upper Gulf coasts, and are
regular but less common on the Texas coast and in southern Florida (Map 2).
Imhof (1977b) commented that the "northern Gulf Coast from the mouth of the
Mississippi R. to St. Mark's Refuge [Florida] probably winters more than
10,000 loons"; the great majority of these are Common Loons.

North Carolina Common Loons are common winter visitors along the coast
(Pearson et al. 1942) but in recent years they have also been frequenting
large inland impoundments (LeGrand 1978). They are normally dispersed along
the coast but are occasionally seen in large concentrations, such as the
1,000 observed in the Cape Lookout Bight 8 March 1973 (Teulings 1973b), and
the mixed flock of 5,000 Common and Red-throated loons reported near Ocracoke
Island on 19 December 1970 (Teulings 1971b). Occasionally, nonbreeders have
summered along the coast (Teulings 1972d) as well as inland.

South Carolina These loons are common in winter on the coast from mid-
October to mid-May. They are much less common inland, and occur there mainly
on migration (Sprunt and Chamberlain 1949). In recent years they have become
more common on the piedmont impoundments, with counts as high as 47 at Lake
Greenwood (Teulings 1977b), and 30 on Lake Murray (LeGrand 1977a).

Winter Distribution Map for -- COMMON LOON
Southeastern United States
BIRDS PER 10 PARTY-HOURS
1I 71Less than 0.1
___- / -1 i0.1-0.5
W0.5-2
s ^ ~More than 2 \
(Adapted from Bystrak, 1974) -
INDIVIDUALS OBSERVED DURING--'
CHRISTMAS BIRD COUNTS, 1973-1977 '---
(ARITHMETIC MEAN)
co Number of individuals --
Less than one individual > O ~ W\
FAYETTEVILLE
None observed I.-

- Til >, \ "? h-\

.DALLAS 4

T E X A S / ---- l "- I
-.... i i i f \,.,,-, T. 25

MMW

Mississippi Delta. Reports in American Birds since 1970 (Webster 1970b, 1971a,
1972b, 1973b, 1975b, 1976b) indicate a sharp decline in loon numbers since the
mid-1960's. It is not clear whether this represents a shift in wintering area
or a real population decline.

SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE

Breeding Common Loons breed largely in the subarctic portion of the
Nearctic (AOU 1957, Cramp et al. 1977). No population estimate is available.

Winter This loon winters primarily along coasts, but is also found in-
land on the Great Lakes (Palmer 1962) and other large water bodies. Through-
out most of the southeastern United States the Common Loon is a regular winter
resident (Map 2). It is apparently less common in the Florida Keys and on
the Texas coast than elsewhere in the southeast.

Migration In the southeast, fall migration seems to be concentrated in
October and November. Earlier records exist (e.g., Edscorn 1975, 1978), but
many of these refer to the occasional summering nonbreeders. Spring migration
is much more protracted. It is well underway in March (Williams 1973), but
many loons are still in the area in May. Loons on their wintering grounds
apparently wait in spring until their breeding habitat is available and ice-
free, and then migrate rapidly (W. Hoffman pers. observ. in Oregon, Washing-
ton, and Alaska; Petersen 1976). Thus, birds from the more southern parts of
the breeding range might migrate in March, but birds breeding farther north
may wait until late May, or even June, to begin their migration. Inland mi-
grations do not seem to follow particular routes (Palmer 1962).

HABITAT

Nesting Common Loons nest solitarily on freshwater lakes in boreal for-
est and tundra areas. They choose lakes that are large enough for easy take-
off and that have adequate food supplies (Olson and Marshall 1952). They
prefer to nest on small islets (Palmer 1962).

Feeding While breeding, Common Loons apparently feed mostly in their
nesting territories on freshwater lakes. In the winter they frequently defend
feeding territories, but may join into rafts when not feeding (McIntyre 1978a).
They feed in bays, inlets, lagoons, and nearshore areas of the ocean (B. King
1976, Baltz and Morejohn 1977, McIntyre 1978a, and W. Hoffman, pers. observ.).

Winter and Offshore Common Loons in winter are normally marine but re-
main within a few kilometers of shore. They regularly use enclosed harbors
and inlets. Bent (1919) referred to groups of wintering loons "sometimes far
out at sea", but this does not seem to agree with more recent observations.

FOOD AND FEEDING BEHAVIOR

Common Loons feed mainly on fish, but also eat crustaceans, insects, and

molluscs. Olson and Marshall (1952) found the fish Perca, Pomoxis, Lepomis,
Micropterus, Stizostedion, Leucicthys, Esox, Ameiurus (Ictalurus), and uniden-
tified catostomids and cyprinids in loon stomachs from Ontario and the Great
Lakes States. Munro (1945) found that on British Columbia lakes without fish,
loons could subsist on aquatic snails, insects, amphipods, and corixids. Veg-
etation is sometimes present in quantity in loon stomachs, but it may serve
a mechanical rather than nutritive function.

In winter, loons seem to eat mostly fish and decapod crustaceans. Loons
attempting to swallow flatfish and other large prey are a common sight on the
Oregon coast and elsewhere (Munro 1945, McIntyre 1978b, W. Hoffman pers. ob-
serv.). Palmer (1962) summarized earlier reports of food habits on salt water.
Fish eaten were "rock cod; flounder; sea trout (Salmo); herring (Clupea); surf
fish (Cymatogaster aggregatus); killifish (Fundulus heteroclitus); menhaden
(Brevoortia patronss; sculpin (Leptocottus armatus)."

Common Loons feed primarily by pursuit diving but also occasionally pick
at items on the surface. They are excellent divers and may stay submerged for
over 2 minutes. Kinnear (1978) recorded nine dives of one loon, averaging 90
seconds each, with rest periods of 20-40 seconds.

IMPORTANT BIOLOGICAL PARAMETERS

Egg Laying Olson and Marshall (1952) reported that nesting in Minnesota
took place in June. Other studies indicate that newly laid clutches may be
found in early or mid-May (Palmer 1962).

Mean Clutch Size Most clutches contain two eggs. Clutches of one are
frequent, of three, rare (Palmer 1962). The average of 47 Minnesota clutches
was 1.55, but all may not have been complete when checked (Olson and Marshall
1952).

Incubation Period The incubation period is 29 days (n = 2) (Olson and
Marshall 1952).

Hatching Success Olson and Marshall (1952) reported that 1 of 19 one-
egg nests and 15 of 22 two-egg nests succeeded. The sample of one-egg nests
may have included nests in which one egg had already been removed by a pred-
ator. It is also not clear whether the hatching of one egg of a two-egg
clutch is considered success.

Fledging Success In Minnesota, 21 young of 42 breeding pairs survived
until 1 September (Palmer 1962).

Age at Fledging Olson and Marshall (1952) estimated 10-11 weeks to
flight. They cited Wilson (1929) to the effect that young hatched in late
May were not on the wing until late August. However, Wilson's comments are
vague and it is not clear that he followed individuals for that period.

Age at First Breeding According to Palmer (1962), there is "no evidence

birds breed until at least 2 years old". There are however, no published
records for age of first breeding based on marked birds.

Mortality of Eggs and Young Munro (1945) noted two fertile eggs that
failed to hatch, and also noted two cases of nest desertion following discov-
ery. Olson and Marshall (1952) considered predation (by crows, ravens, Her-
ring Gulls, mink, otter, and muskrats) and desertion to be the main causes
of nest failure. Desertion frequently followed human disturbance, but also
occurred in areas of heavy beaver or muskrat activity. Olson and Marshall
(1952) thought that early mortality of young was partly due to predation,
weakness of one of the chicks, and human interference.

Renesting In the southern portions of their range, Common Loons regular-
ly renest following loss of a clutch (Bent 1919). Olson and Marshall (1952)
found 15 replacement clutches, and reported four pairs of loons that laid
third clutches after losing their first two.

Maximum Natural Longevity A bird banded in Ontario was found dead in
New Jersey at an estimated minimum age of 7 years, 10 months (Clapp et al.
1979 ms).

Weight (in grams) Six summer adult males in Minnesota averaged 3,510,
and eight females, 3,000. These males ranged from 2,520 to 4,200, and the
females from 1,600 to 3,860 (Olson and Marshall 1952; original data in pounds
and ounces).

SUSCEPTIBILITY TO OIL POLLUTION

Loons are among the birds most vulnerable to oiling, which may cause
considerable local mortality (Palmer 1962). They do not appear in large num-
bers on beached bird surveys (Table 7). They sleep on the water, and have a
flightless molt period during late winter. There are at least three reasons
why significant mortality of loons might be missed. First, on a worldwide
basis, loon populations are much smaller and tend to be more dispersed than
the auks and sea ducks that make up the bulk of reported oiling mortality.
Second, loons may not seek shore as quickly when oiled, and thus are more
likely to die in the water than are most other nearshore birds. Third, loons
are less buoyant than other seabirds, and heavily oiled loons are more likely
to sink upon death than similarly oiled ducks, auks, or other seabirds.

Indications of apparent low impact, such as the low loon totals on Euro-
pean beached bird surveys are probably not indicative of the actual vulnera-
bility of loons. Combined data for three periods (1970-71, 1972-73, 1975)
included only 65 loons out of 6,388 birds (Lloyd 1976, Croxall 1977).

There have been several instances of notable loon mortality from petro-
leum in the southeastern United States and Gulf of Mexico. Many beached Com-
mon Loons were reported from North Carolina (Peterson 1942) and Florida
(Longstreet 1953-55). More recently, approximately 225 Common Loons were
found dead or dying on beaches at St. Augustine, St. Johns County, Florida,
between 12 and 20 January 1974 (Stevenson 1974). F. White et al. (1976) ex-

63

amined 124 of the dead loons found that winter; 76 (61%) had been oiled. The
source of this oil was unknown.

In 1970, 10,000 gallons of Bunker C oil was spilled in Tampa Bay, Flor-
ida, and a slick of approximately 100 sq mi quickly formed. Because the spill
occurred in a sheltered bay in fairly calm weather, and in an urban area, a
large volunteer bird rescue and cleaning force was mobilized the day after
the spill. Oiled birds were retrieved from the water by people wading from
beaches and by boat. Approximately 500 Common Loons, a major fraction of the
winter population, passed through the cleaning stations. Most were released
shortly after cleaning, but survival was probably low. It is important to
note that the circumstances of the spill, and the very quick response to it,
allowed a much better assessment of the vulnerability of these birds than is
usually possible. The seasonal reports in American Birds reported lower than
normal numbers of Common Loons in the Tampa Bay area in subsequent winters
(Woolfenden 1973, Edscorn 1974, Stevenson 1974, 1977), presumably the result
of that mortality. King and Sanger (1979) give an Oil Vulnerability Index of
45 to this species in the Pacific Northwest.

Table 7. Number of dead birds and number and percentage of dead Common
Loons found after major oiling incidents.

Number Number Percent-
of oiled of dead age of
dead Common Common
Area Dates birds Loons Loons Source

Island Beach,
New Jersey

North-central
Kattegat, Denmark

Southeast Kent,
England

Northeast England

Pagham Harbour
area, W. Sussex,
England

TORREY CANYON (d)
oil spill, SW
Britain

Jan. 1945

Jan.-Feb.
1962

winters of
1963-1964
to 1965-1966

Jan. 1966

Jan.-Feb.
1967

Mar. 1967

92 (a) 7 7.61 Kramer and
Kramer 1945

1,723 (a,b)

2 0.12

Joensen
1972a

509 (b) 39 7.66 Gibson 1966

2 0.25 Parrack
1967

91 (b,c) 1 1.09 Phillips
1967

1,223 1 0.08 Bourne et
al. 1967

805

Table 7. Continued.

Numbers Number Percent-
of oiled of dead age of
dead Common Common
Area Dates birds Loons Loons Source

Tay Estuary, Mar.-Apr. 1,168 (c) 5 0.43 Greenwood
Scotland 1968 and Keddie
1968

Northeast Britain Jan.-Feb. 10,992 (a,b) 16 0.15 Greenwood
1970 et al. 1971

Off Eastern Feb.-Apr. 1,276 (b,c) 12 0.94 Brown et
Canada 1970 al. 1973

San Francisco Bay, Jan. 1971 3,221 (b,e) 28 0.87 Smail et
California al. 1972

Chesapeake Bay, Feb. 1976 8,385 (b) 195 2.33 Roland et
Virginia al. 1977

AMOCO CADIZ spill, Mar. 1978 3,770 (b,c) 66 1.75 Hope Jones
NW France and et al. 1978
Channel Islands

(a) Total includes some birds that were not oiled.

Total includes
Total includes
This sample is

only those

birds identified to species.

both live and dead oiled birds.
from a spill that was believed to have killed more than

30,000 seabirds.
(e) This figure represents birds brought the cleaning/receiving stations.

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Loon. Wilson Bull. 65: 213.

1952

Gudmundsson, F. 1952. Islenzkir fuglar I. Himbrimi (Colymbus immer Brunn.).
[Icelandic birds I. The Great Northern Diver (Colymbus immer Brunn.).]
Natturufraedingurinn 22: 44-45. [In Icelandic with English summary.]

Manville, R. H. 1952. Loons in the Huron Mountains. Jack-Pine Warbler 30:
52-53.

Olson, S. T. and W. H. Marshall. 1952. The Common Loon in Minnesota. Univ.
Minne. Mus. Nat. Hist. Occas. Pap. No. 5. vi and 77 pp.

1951

Olson, S. T. 1951. A study of the Common Loon, Gavia immer sp., in the
Superior National Forest of northern Minnesota. M. S. thesis, Univ.
Minnesota.

Preston, F. W. 1951. Flight speed of the Common Loon (Gavia immer). Wilson
Bull. 63: 198.

1950

Yeates, G. K. 1950. Field notes on the nesting habits of the Great Northern
Diver. Brit. Birds 42: 5-8.

1949

Hebard, F. V. 1949. Lesser Loon in Georgia. Oriole 14: 23.

Ulmer, F. A., Jr. 1949. An albino Common Loon. Auk 66: 195.

1948

Rand, A. L. 1948. Summer flocking of the Loon, Gavia immer (Brunnich).
Can. Field Nat. 62: 42-43.

1947

Rand, A. L. 1947. Geographical variation in the loon, Gavia immer (Brunnich).
Can. Field Nat. 61: 193-195.

Schorger, A. W. 1947. The deep diving of the loon and Oldsquaw and its
mechanism. Wilson Bull. 59: 151-159.

1945

Munro, J. A. 1945. Observations of the loon in the Cariboo Parklands, Brit-
ish Columbia. Auk 62: 38-49.

1944

Buchanan, F. W. 1944. Notes on molting time of loons and grebes. Wilson
Bull. 56: 116.

Counce, C. C. 1944. A captive Common Loon. Kentucky Warbler 20: 30.

1938

Vasvari, N. 1938. Die Bedeutung der Magensteine (Gastrolithe) bei den See-
tauchern (Colymbus). [The importance of gastroliths in the divers
(Colymbus).] Proc. VIII Intern. Ornithol. Congr., Oxford 1934: 730-734.
[In German.]

1935

Black, C. T. 1935. Common Loon in Illinois in July. Auk 52: 74.

Wetmore, A. 1935. The Common Loon in the Florida Keys. Auk 52: 300.

1930

May, J. B. 1930. Simultaneous loss of primaries in prenuptial molt of loon.
Auk 47: 412-414.

Tyrell, W. B. 1930. Peculiar actions of the loon (Gavia immer). Auk 47: 238.

1929

Wilson, F. N. 1929. The loon at close range. Bird-Lore 31: 95-108.

1928

Wilson, F. N. 1928. Hunting loons with a camera. Bird-Lore 30: 171-177.

1925

Lincoln, F. C. 1925. Loons and Horned Grebes in pound nets. Proc. Biol.
Soc. Wash. 38: 88.

1924

Brewster, W. 1924. The loon on Lake Umbagog. Bird-Lore 26: 309-314.

Townsend, C. H. 1924. Diving of loons and grebes. Auk 41: 20-41.

1923

Brown, C. A. 1923. Loon nests. Bird-Lore 25: 316-317.

Kennard, F. H. 1923. Notes on the diving of loons. Auk 40: 119-120.

Robinson, H. W. 1923. Dive of the Great Northern Diver. Brit. Birds 17: 64.

71

Sims, R. J. 1923. The Common Loon. Bird-Lore 25: 167-175.

1921

Anthony, A. W. 1921. A loon (Gavia immer) caught on a fishing line. Auk
38: 269.

Bagg, A. C. 1921. An oil-soaked loon (Gavia immer) at Watch Hill, R.I.
Auk 38: 594-595.

Bishop, L. B. 1921. Description of a new loon. Auk 38: 364-370.

1920

Allen, W. E. 1920. Behavior of loons and sardines. Ecology 1: 309-310.

1915

Dunlop, E. B. 1915. Notes on the Great Northern Diver. Brit. Birds 9:
142-147.

1874

Boardman, G. A. 1874. A loon-atic on ice. Forest & Stream 3: 291.

LEAST GREBE

(Tachybaptus dominicus)

[SP: Zambullidor chico, US: Mexican Grebe, Santo Domingo Grebe]

GENERAL DISTRIBUTION

North America The Least Grebe is resident from southern Texas south
through eastern Mexico to Central America. It breeds also in southern Baja
California and Sonora, once in southeastern California and has wandered to
Arizona. The status of the northern form is poorly known (AOU 1957, Palmer
1962).

World Distribution Other subspecies of the Least Grebe breed in the
Caribbean, in the southern Bahamas, Greater Antilles, Trinidad and (formerly)
Tobago, and in South America south to western Peru, Bolivia, northern Argen-
tina, Uruguay, and southern Brazil (Bond 1971, Blake 1977, Storer 1979b).

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

Least Grebes have been reported in three of the southeastern states
(Florida, Louisiana, and Texas), but Texas is the only state in which they
occur regularly.

Florida Least Grebes have been reported from Florida three times, but
documentation for its natural occurrence in the state is still inadequate.

1966- 4 Dec.-
67 22 Mar.

1970 27 Nov.

1976 13 Jan.

1 seen

1 seen

1 reportedly
found dead

Lake Ariana and Saddle
Creek Park, Polk Co.

on duck pond, Crandon
Zoology Park, Miami

discarded by zoo
attendant, Miami

Agey 1967

Robertson 1971

Stevenson 1976

Louisiana The Least Grebe has been recorded only twice in Louisiana.

1947 14 Dec.

1 male, coll.
(LSU 10604)

shot in lake,
Baton Rouge

Lowery and
Newman 1950b,
Lowery 1974

Taxonomic note: This species is listed as Podiceps dominicus in most refer-
ences (e.g., AOU 1957), but has recently been transferred to Tachybaptus
(Storer 1976, 1979b).

1978 1-18 Dec. 1 seen Mud Lake and near Eyster 1978,
Holly Beach, Cameron Hamilton 1978
Par.

Texas In Texas, the Least Grebe is a local resident, recorded primarily
from the southeastern portion of the state. It is locally common to uncommon
near the central and lower coasts (Calhoun to Cameron counties), and scarce
along the coast to the north.

SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE

The Least Grebe is resident throughout its range, but it is evidently
capable of local and occasional long distance dispersal. The species has a
broad neotropical distribution, occurring throughout much of Central and
South America, and in the Caribbean. In the southeastern United States it
occurs and breeds regularly only in southeastern Texas.

HABITAT

Nesting Least Grebes nest solitarily, sometimes forming loose aggrega-
tions, and build floating nests on ponds, lakes, or ditches. At least some
vegetation is needed to anchor the nest, but nests may be found well away
from shore in open water or near shore either within or without emergent vege-
tation. In Texas, these grebes occur predominantly in small bodies of fresh
water (Oberholser 1974). They prefer to nest in small intermittent ponds and
roadside ditches and readily change nesting areas when these are lost to envi-
ronmental changes (P. James in Palmer 1962, Storer 1976).

Winter and Offshore Least Grebes winter in the same freshwater habitat
in which they breed and apparently seldom occur offshore in coastal areas.

FOOD AND FEEDING BEHAVIOR

Unusually little information is available on the food habits of Least
Grebes in the United States (or elsewhere). That available for the United
States results largely from the examination of five stomachs collected in
Hidalgo County, Texas, in December 1937 (Cottam and Knappen 1939). All stom-
achs contained only insects, with aquatic beetles and bugs comprising nearly
90% of the diet. The only other insect group of any importance was the nymphs
of Odonata.

More recently, Storer (1976) reported on the stomach contents of eight
birds, five from Guatemala in April and May and three from Veracruz and Cam-
peche, Mexico, in March and April. Insects, particularly ants, predominated
in the Guatemalan birds, but fish bones, shrimp, and one crab were also found.
In the Mexican birds, insects were again found most frequently. Crayfish,
shrimp, and six "large, hairy spiders" also were found.

Gross (1949) also reported that adults and young in Cuba fed upon aquatic

insects, crayfish, and shrimp-like crustaceans. Young in the Rio Grande Val-
ley, Texas, were fed almost entirely on the larvae of damselflies and dragon-
flies (Odonata) (P. James in Palmer 1962).

Least Grebes evidently feed primarily by diving beneath the surface. In
a 3.6 ha, 2 m deep pond in Costa Rica, diving times ranged from 8.7 to 14.7
sec with a mean of 12.5 (n = 23) (Jenni 1969). A variety of other feeding
methods are also used. Birds may feed by submerging only the head and neck,
by picking food from the surface or emergent vegetation, and by seizing in-
sects from the air (Storer 1976). Storer also reported an unusual technique
in which a grebe dove below the surface and emerged to snap at a passing drag-
onfly. Least Grebes are also known to use the activities of other species
inobtaining food. In Costa Rica, Paulson (1969) watched four Least Grebes
closely follow a flock of domestic Mallards, dive among them, and apparently
feed on fish or invertebrates disturbed by the ducks. Least Grebe feeding
rates increased and decreased concomitant with the presence and absence of
the Mallards.

SUSCEPTIBILITY TO OIL POLLUTION

We have not found evidence that shows this species is directly affected
by oil. Although the Least Grebe belongs to a group of diving birds often
severely afflicted by oil pollution, its rare occurrence in waters likely to
be involved in oil spills make it considerably less vulnerable than other
grebes. Further, its occurrence in the southeastern United States is ex-
tremely limited.

BIBLIOGRAPHY

1978

Eyster, M. B. 1978. Least Grebe in Louisiana. La. Ornithol. Soc. News 81: 3.

1976

Storer, R. W. 1976. The behavior and relationships of the Least Grebe.
Trans. San Diego Soc. Nat. Hist. 18: 113-126.

1975

Storer, R. W. 1975. The status of the Least Grebe in Argentina. Bull. Br.
Ornithol. Club 95: 148-151.

Storer, R. W., W. R. Siegfried and J. Kinahan. 1975. Sunbathing in grebes.
Living Bird 14: 45-56.

1974

Jenni, D. A. and R. D. Gambs. 1974. Diving times of grebes and Masked Ducks.
Auk 91: 415-417.

1969

Jenni, D. A. 1969. Diving times of the Least Grebe and Masked Duck. Auk
86: 355-356.

Paulson, D. R. 1969. Commensal feeding in grebes. Auk 86: 759.

1967

Agey, H. N. 1967. Notes on sightings of what appears to be the Least Grebe
(Colymbus dominicus). Fla. Nat. 40: 101.

1963

James, P. 1963. Freeze loss in the Least Grebe (Podiceps dominicus) in
Lower Rio Grande Delta of Texas. Southwest. Nat. 8: 45-46.

Meitzen, T. C. 1963. Additions to the known breeding ranges of several
species in south Texas. Auk 80: 368-369.

1957

Zimmerman, D. A. 1957. Display of the Least Grebe. Auk 74: 390.

1950

Lowery, G. H., Jr. and R. J. Newman. 1950b. The Mexican Grebe, Colymbus d.
brachypterus, at Baton Rouge, Louisiana. Auk 67: 505-506.

1949

Gross, A. 0. 1949. The Antillean Grebe at central Soledad, Cuba. Auk 66:
42-52.

1947

McMurry, F. B. 1947. Least Grebe breeding in California. Condor 49:
125-126.

1939

Cottam, C. and P. Knappen. 1939. Food of some uncommon North American birds.
Auk 56: 138-169.

1899

Chapman, F. M. 1899. Description of two new species of Colymbus dominicus
Linn. Bull. Am. Mus. Nat. Hist. 12: 255-256.

PIED-BILLED GREBE

(Podilymbus podiceps)

[DU: Dikbekfuut, FR: Grebe a bec cercle, GE: Bindentaucher, SP: Zambullidor
Pico Pinto, Maca picopinto; SW: Svartvitnabbad dropping]

GENERAL DISTRIBUTION

North America Pied-billed Grebes breed from central and southern British
Columbia, central-southern Mackenzie, Alberta, Saskatchewan, Manitoba, central
Ontario, southwestern Quebec, southern New Brunswick, Prince Edward Island,
and Nova Scotia south throughout North America with the exception of northern
Maine. They are local in occurrence in many areas (AOU 1957, Palmer 1962).

The northernmost populations are migratory, and winter in ice-free waters
from southwestern British Columbia south through southwestern Idaho and west-
ern Utah, east through southern New Mexico and central Texas to Georgia, thence
north to Chesapeake Bay and the Delmarva Peninsula (Palmer 1962). Scattered
individuals occasionally winter in open waters throughout much of the breeding
range.

World Distribution Pied-billed Grebes also breed and are apparently res-
ident throughout the West Indies and south from Central America through most
of South America to Chile and southern Argentina (Bond 1971, Blake 1977).
They occur casually in the southern Yukon, James Bay, the Gulf of St. Lawrence,
and Newfoundland (Godfrey 1966), and are accidental in Labrador, Baffin Island,
Britain, Ireland, and the Azores (Godfrey 1966, Cramp et al. 1977, Dunbar et
al. 1979).

DISTRIBUTION IN THE COASTAL SOUTHEASTERN UNITED STATES

North Carolina Pied-billed Grebes occur throughout the state all year,
but the largest numbers are found along the coast from September through May
(Wray and Davis 1959). They breed most commonly toward the coast, almost
strictly below the Fall Line (LeGrand 1977b). Coastal areas from which cer-
tain evidence of breeding has been obtained include (from north to south)
Bertie, Dare, Craven, Pamlico, Onslow, New Hanover, and Brunswick counties
(Pearson et al. 1942, Wray and Davis 1959, Lewis 1970, Teulings 1971e).

As in other areas of the southeast, this grebe breeds during an extended
period. In the coastal area, eggs have been reported from 26 May through 26
August (Pearson et al. 1942, Lewis 1970), and juveniles have been observed
from 10 June through 24 July (Lewis 1970, Teulings 1971e). It seems likely
that further observations will reveal a nesting season extending from April
through September.

The status of Pied-billed Grebes during migration is largely unknown,
and there is little numerical information on transient or wintering popula-

tions. Examination of recent Christmas Bird Count figures (Map 3) shows that
Pied-billed Grebes occur regularly in winter in North Carolina, but only in
moderate numbers.

South Carolina Pied-billed Grebes are considered common throughout the
year (Sprunt and Chamberlain 1949), but little information is available on
either numbers present or on breeding biology. Along the coast, they have
been recorded breeding in at least Beaufort and Charleston counties; eggs
have been found from 11 April through 7 June. Young have been noted at Hunt-
ington Beach State Park on 18 July (Teulings 1971e). Pied-billed Grebes win-
ter along the coast in small to moderate numbers (Map 3).

Georgia These grebes breed locally throughout the Coastal Plain and in
the Appalachian Valley (Denton et al. 1977), but nest only very rarely along
the coast and even then apparently only in fresh water. Pied-billed Grebes
are common migrants and winter residents throughout Georgia. Peak abundance
in or near coastal waters occurs from late August or September until late
April (Tomkins 1958, Teal 1959). The number present along the coast in win-
ter is relatively small. Sixteen Christmas Bird Counts held at Sapelo Island
from 1958-68 (R. E. Hamilton 1969) and 1973-77 reveal a range of 0-18 birds
seen, with a mean of 6.8.

Florida Atlantic and Gulf Coasts Pied-billed Grebes breed on fresh-
water ponds throughout Florida, but are apparently more common in the north-
ern portion of the state (Howell 1932, Sprunt 1954). Most breeding occurs
from mid-April to early September (Sprunt 1954), but recent observations of
partly grown young in early January and early February (Stevenson 1970, 1974),
as well as a report of an incubating bird in late September (Edscorn 1974),
suggest that breeding may occur in every month of the year. Little is known
of transient or wintering populations, but the species is considerably more
common during the winter (Map 3), indicating an influx of migrants from the
north. It is an abundant winter resident on the Gulf coast (at Pensacola)
with the largest number present from late September through mid-April (Weston
in Howell 1932). In coastal areas, summer or winter, most birds are found on
freshwater impoundments or ponds and not on salt water itself.

Alabama In Alabama these birds occur widely throughout the year and are
common along the coast from about late August through early May. They breed
locally, with about half of the certain breeding records from Baldwin County
near the coast. For the state as a whole, eggs have been reported from late
April to mid-May and dependent young from mid-May to early August (Stewart
1970, Imhof 1976b).

Mississippi Pied-billed Grebes are found throughout Mississippi in all
seasons, but few details are known about seasonal abundance and breeding dis-
tribution. Along the coast this grebe is most abundant in the fall and winter
months, and it has been found breeding near Gulfport on at least one occasion
(Burleigh 1944).

Louisiana These grebes are at least moderately common locally all year
in Louisiana, but are most abundant from early October to early April (Ober-
holser 1938, Lowery 1974). Near the coast they breed in both fresh and brack-

Winter Distribution Map for -- 1 PIED-BILLED GREBE
Southeastern United States

BIRDS PER 10 PARTY-HOURS
Less than one
1-5 S_______
5-20
MMore than 20
(Adapted from Bystrak, 1974) ...
INDIVIDUALS OBSERVED DURING
CHRISTMAS BIRD COUNTS, 1973-1977
(ARITHMETIC MEAN)

SNumber of individuals

SLess than one individual

None observed

33

PH I
40 GE27 3 ON
35 1 58 115
11

626 16

198 77

31

140 71
SANI

mA xTAscosA

ish impounded waters (Chabreck 1963). At Rockefeller Wildlife Refuge, bor-
dered on the south by the Gulf of Mexico, Chabreck found new nests from early
May through late August 1961. Dependent young were present from at least May
through early September. Because young from eggs laid in late August would
not result in fledged young for well over a month, dependent young are prob-
ably present at least into October.

Texas Pied-billed Grebes are found in Texas year-round and may be found
breeding in any month. Eggs have been recorded from March to late August,
and small young have been reported from early February through mid-January
(Oberholser 1974, Webster 1974c). According to Oberholser, however, most
breeding occurs from March through September.

This grebe is common to fairly common (Map 3) along the coast in winter
(Oberholser 1974), with the greatest numbers present (on at least the south-
ern coast) from September through March (Blacklock 1978 ms).

SYNOPSIS OF PRESENT DISTRIBUTION AND ABUNDANCE

Breeding Pied-billed Grebes breed throughout much of North, Central,
and South America, and in the West Indies. They occur throughout the south-
eastern United States, but apparently breed less commonly in the more south-
ern parts of this area. Smaller numbers are present during the breeding per-
iod which, for most areas, occurs from about April through August, but which
may be considerably more extended at the more southern localities (e.g., Flor-
ida and Texas).

Migration and Winter More northerly populations of the Pied-billed Grebe
are migratory in whole or in part, while those to the south tend to be resi-
dent. Throughout the southeast, numbers present become greater as migrants
and winter visitors add to resident populations. Occurrence in coastal waters
apparently becomes disproportionately greater during migration and winter,
but detailed data documenting this are lacking.

Winter is the only period when this mostly solitary species may be found
in relatively large aggregations. Flocks on inland waters in Florida have
numbered as many as a thousand, and flocks of 100 or more are not uncommon
(Sprunt 1954). On coastal waters, a maximum of 65 birds were reported for
Dauphin Island, Alabama, on 18 December 1971 (Imhof 1976b). Periods of maxi-
mal abundance for various southeastern states in standard reference works are
listed below:

North Carolina: September through May
Georgia: late August/September through late April
Florida-Gulf: late September through mid April
Alabama: late August through early May
Mississippi: October through March
Louisiana: early October through early April
Texas: September through March

HABITAT

Nesting Pied-billed Grebes nest solitarily and prefer fresh water,
standing or moving, with well vegetated shores and ample emergent vegetation.
At least some open water is required. They may breed on ponds, sloughs,
flooded areas, in marshy areas of lakes and rivers, and occasionally on estu-
arine waters where tidal influence is weak (Palmer 1962, Cramp et al. 1977).

These grebes prefer to nest in shallow water. In Manitoba, 31 nests
were in water that averaged 35.5 cm deep. Mean distance of 25 nests from
shore was 5.3 m, and from open water was 1.3 m. Bulrush (Scirpus) and cattail
(Typha) was the dominant plant cover for approximately 98% of the 53 nests
found (Sealy 1978). Those nesting in prairie pothole marshes near Ruthven,
Iowa, also nested in shallow water; 76.8% of 138 nests were in depths of 30
in (76 cm) or less. Mean distance from the nest to open water was 25.8 ft,
but 54.3% of the nests were more than 100 ft from shore (Glover 1953). In
North Dakota, 82 nests were found in depths ranging from 11 to 37 in and aver-
aging 25 in (63 cm) (R. Stewart 1975).

On an impoundment in Louisiana, most nests (52%) were in open water, the
rest (46%) in small stands of wiregrass (Spartina patens). Distance to the
nearest stand of dense emergent vegetation averaged 60 m (range = 1-183 m)
(Chabreck 1963).

In North Dakota, all 48 Pied-billed Grebe nests found by Faaborg (1976)
were in seasonal or semi-permanent bodies of water, 29 of them on relatively
small ponds (3 ha or less). These grebes also choose relatively small bodies
of water in eastern Washington. Yocum et al. (1958) reported that 80% of all
broods found were on potholes 1 to 5 acres in size.

Feeding Pied-billed Grebes feed in their nesting and winter habitats.

Winter and Offshore Most birds winter in habitats similar to those used
during the breeding season, but they often occur in more exposed areas. Some
use brackish estuarine waters, and an even smaller proportion use salt water,
where they prefer sheltered ocean inlets (Palmer 1962, Cramp et al. 1977).

FOOD AND FEEDING BEHAVIOR

Little specific information has been reported on the food habits of the
Pied-billed Grebe in the southeastern United States. Howell (1928) reported
that a single stomach collected in Alabama contained the remains of two or
three fishes and two crayfish, and Palmer (1962) noted that leeches were the
principal source of food during the breeding season in South Carolina.

Papers by Wetmore (1924) and Munro (1941) contain most of the available
detailed information on the diet of the Pied-billed Grebe. Wetmore (1924)
reported the stomach contents of 174 grebes collected at various localities
and at different times of year. Fish (24.2% by volume), crustaceans (31.1%),
and insects (46.3%), primarily aquatic forms, made up most of the diet.
Among the crustaceans, crayfish (Cambarus, Potamobius) were frequently repre-

sented, and Heteroptera and Coleoptera were predominant among the insect forms
taken. Spiders, snails, and small frogs were taken infrequently.

Wetmore (1924) presented little information on seasonal or geographical
variation in food habits, but noted that fish were eaten only in small quan-
tities from May to August, during the nesting season. He also remarked that
consumption of damselflies and dragonflies (Odonata), representing only 8% of
the diet overall, was much greater in July and August, when these insects con-
stituted 34% of the diet.

Munro (1941) commented on the diet of the Pied-billed Grebe in British
Columbia, basing his remarks primarily on the contents of eight stomachs.
Fish was the major item of diet for adults and larger young, while the stom-
achs of three downy young contained mostly Odonata. He stated that nymphs of
Odonata and aquatic insects were the principal summer foods in waters where
fish were not present.

Pied-billed Grebes feed primarily by diving and pursuing their prey under
water. Other feeding techniques may be used, but we have found little infor-
mation on this point. Street (in Miller 1942) reported that an adult was seen
swimming with only the head submerged, but did not see whether any food was
obtained as a result. Pied-billed Grebes observed in shallow water in Florida
used paddling movements of their feet to stir up sediment and bring prey into
view (B. King 1974a).

Duration of foraging dives has been measured by several observers.
Bleich (1975) timed 154 dives on two small California lakes with water depths
from 2-5 m and found that dives averaged 7.6 sec (range = 1-15). Distance
moved during these dives averaged 3.7 m (range = 0-12 m). Heintzelman and
Newberry (1964) reported that two individuals at Brigantine NWR in New Jersey
had average diving times of 12.7 sec (n = 4, range = 9-17) and 9.4 sec (n =
10, range = 6-9), but information was not given on either habitat or depth
of water.

Pied-billed Grebes have reportedly used the foraging behavior of other
species to obtain food. Leck (1971) observed these grebes and Snowy Egrets
(Egretta thula) foraging together in a canal at Chincoteague NWR in Virginia.
He suggested that this association was mutually advantageous, because the ac-
tivities of each provided greater opportunities for prey capture by the other.
Somewhat similar observations were made by Mueller et al. (1972) on a feeding
association of three Pied-billed Grebes, a Snowy Egret, and a Louisiana Heron
(Hydranassa tricolor) at a small freshwater pond in North Carolina. These
observations suggested that more advantage accrued to the grebes than to the
herons.

IMPORTANT BIOLOGICAL PARAMETERS

Egg Laying The nesting period of the Pied-billed Grebe varies consider-
ably according to locality over its extensive range. Nests may be initiated
in North America as early as April and as late as June, and the nesting season
may extend to July or August, or even later. May is probably the peak breed-

ing month in the United States. The time of nesting in the southeastern
states has been detailed above in the discussions of the individual states.

Mean Clutch Size In a number of studies, average clutch size ranged
from 4.3 (Wolf 1955) to 7.3 (Chabreck 1963), and the number of eggs found in
individual nests ranged from 2 (Glover 1953) to 11 (R. Stewart 1975). In
Minnesota, seven eggs were most frequent (Sealy 1978). Data from Louisiana
(Chabreck 1963) suggest that mean clutch size decreases as the nesting season
progresses.

Incubation Period Limited information suggests that the normal incuba-
tion period is about 23 days (Deusing 1939, Palmer 1962).

Hatching Success Studies in Idaho, Iowa, and Louisiana revealed a high
degree of success, with 90-97% of the eggs hatching in successful nests, i.e.,
those in which some young hatched (Glover 1953, Wolf 1955, Chabreck 1963).

Fledging Success Data on fledging success in terms of young fledged per
egg, per nest, and other measures, are virtually unavailable for this species.
Often the only information available is a strong suspicion that a particular
nest fledged at least some young. On this basis, Chabreck (1963) reported that
96 of 107 (89.6%) nests examined in a Louisiana impoundment produced young.
In south Texas, young were produced in 78.3% (n = 23) and 91.7% (n = 12) of
nests observed in 1957 and 1958, respectively (Cottam and Glazener 1959 in
Chabreck 1963).

Age at Fledging Unknown (Palmer 1962).

Age at First Breeding Unknown (Palmer 1962).

Mortality of Eggs and Young In British Columbia, Iowa, and Louisiana,
nests were primarily lost to the effects of wind, rain, storm, and fluctuating
water levels (Munro 1941, Glover 1953, Chabreck 1963). Egg loss may also be
caused by predation by other waterbirds nesting in the same area. Jerome
Stoudt saw an American Coot (Fulica americana) pecking at the eggs in a Pied-
billed Grebe nest, and on further inspection found all eggs opened and the
contents gone from one or two (Burger 1974). Mammals may also be important
predators; Glover (1953) estimated that 25% of nest loss in Iowa in 1948 was
due to predation by Raccoons (Procyon lotor).

Renesting Pied-billed Grebes are indeterminate layers (Fugle and Roth-
stein 1977) and may replace lost clutches, but our information on this point
is inadequate. The extent to which they are multi-brooded appears to be
poorly known. In at least one instance, a pair in Pennsylvania is known to
have produced two broods (Miller 1942).

Maximum Natural Longevity No data are available.

Weight (in grams) Few data are available on weights of Pied-billed
Grebes. The most adequate information, provided by Storer (in Palmer 1962),
is as follows:

5 adult male 485-559
3 adult female 281-435
20 immature male 282-556
13 immature female 189-389

SUSCEPTIBILITY TO OIL POLLUTION

The preference of Pied-billed Grebes for habitats less likely to receive
the brunt of oil pollution, as well as their tendency to occur solitarily or
in small groups, make it unlikely that a major proportion of a wintering pop-
ulation will be lost as the result of an oil spill. One Pied-billed Grebe
was among more than 3,000 birds found after an oil spill in San Francisco Bay
in 1971 (Smail et al. 1972).

BIBLIOGRAPHY

1980

Ryan, M. R. and P. A. Heagy. 1980. Sunbathing behavior of the Pied-billed
Grebe. Wilson Bull. 92: 409-412.

1979

Ackerman, R. A. and M. Platter-Rieger. 1979. Water loss by Pied-billed Grebe
(Podilymbus podiceps) eggs. [Abstract only]. Amer. Zool. 19: 921.

Dunbar, J., S. Curtis and R. Cardno. 1979. Pied-billed Grebe in Grampian.
Brit. Birds 72: 329.

1978

Sealy, S. G. 1978. Clutch size and nest placement of the Pied-Billed Grebe
in Manitoba. Wilson Bull. 90: 301-302

1977

Fugle, G. N. and S. I. Rothstein. 1977. Clutch size determination, egg size
and egg-shell thickness in the Pied-billed Grebe. Auk 94: 371-373.

Scott, C. M. 1977. Food stealing behavior in the Ring-billed Gull. Bull.
Okla. Ornithol. Soc. 10: 33.

Urquhart, L. A. 1977. Pied-billed Grebe in Kircudbrightshire. Scott. Birds
9: 297-298.

1976

Faaborg, J. 1976. Habitat selection and territorial behavior of the small
grebes of North Dakota. Wilson Bull. 88: 390-399.

N Age Sex

Ranee

1975

Bleich, V. C. 1975. Diving times and distances in the Pied-billed Grebe.
Wilson Bull. 87: 278-280.

1974

Burger, J. 1974. Breeding adaptations of Franklin's Gull (Larus pipixcan)
to a marsh habitat. Anim. Behav. 22: 521-567.

King, B. 1974a. "Foot-paddling" behavior of Pied-billed Grebes. Brit.
Birds 67: 439.

1973

McCowan, M. 1973. Pied-billed Grebe nesting observations. Blue Jay 31:
97-98.

1972

Mueller, H. C., M. G. Biben and H. F. Sears. 1972. Feeding interactions be-
tween Pied-billed Grebes and herons. Auk 89: 190.

1971

Leck, C. F. 1971. Cooperative feeding in Leucophoyx thula and Podilymbus
podiceps (Aves). Am. Midl. Nat. 86: 241-242.

1969

Post, W. 1969. Breeding birds of Williston Bay. Chat 33: 83-84.

Zusi, R. L. and R. W. Storer. 1969. Osteology and myology of the head and
neck of the Pied-billed Grebes (Podilymbus). Misc. Publ. Mus. Zool.
Univ. Mich No. 139. 49 pp.

1968

Kleiman, J. P. 1968. A late nesting of the Pied-billed Grebe in Monroe
County. Jack-Pine Warbler 46: 15.

Ladhams, D. E. 1968. Diving times of grebes. Brit. Birds 61: 27-30.

1967

Mather, J. R. 1967. Pied-billed Grebe in Yorkshire. Brit. Birds 60: 290-295.

Ladhams, D. E., R. J. Prytherch and K. E. L. Simmons. 1967. Pied-billed
Grebe in Somerset. Brit. Birds 60: 295-299.

Simmons, K. E. L. 1967. Pied-billed Grebe behaviour. Brit. Birds 60:
530-531.

Storer, R. W. 1967. Pied-billed Grebe behaviour. Brit. Birds 60: 531-532.

1965

Prytherch, R. J. 1965. Pied-billed Grebe in Somerset: a bird new to Great
Britain and Ireland. Brit. Birds 58: 305-309.

1963

Chabreck, R. H. 1963. Breeding habits of the Pied-billed Grebe in an im-
pounded coastal marsh in Louisiana. Auk 80: 447-452.

McAllister, N. M. and R. W. Storer. 1963. Copulation in the Pied-billed
Grebe. Wilson Bull. 75: 166-173.

1961

Storer, R. W. 1961. Observations of pellet-casting by Horned and Pied-
billed grebes. Auk 78: 90-92.

1958

Short, H. L. and D. E. Craigie. 1958. Pied-billed Grebes mistake highway
for water. Auk 75: 473-474.

Yocum, L. F., S. W. Harris and H. A. Hanson. 1958. Status of grebes in
eastern Washington. Auk 75: 36-47.

1957

Leavitt, B. B. 1957. Water Moccasin preys on Pied-billed Grebe. Wilson
Bull. 69: 112-113.

1956

Atkeson, T. Z., Jr. 1956. Pied-billed Grebe nesting records from the Ten-
nessee Valley. Ala. Birdlife 4: 6.

Laughlin, R. M. 1956. Unusual behavior of a Pied-billed Grebe (Podilymbus
podiceps). Auk 73: 134

1955

Wolf, K. 1955. Some effects of fluctuating and falling water levels on
waterfowl production. J. Wildl. Manage. 19: 13-23.

1954

Cuthbert, N. L. 1954. Pied-billed Grebe taking flight from land. Wilson
Bull. 66: 272-273.

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