Chapter VII: Part V: , Birds. U.S. Army, Signal Corps, Washington, D.C. Pages (1)

115-196.

Udvardy, M. D. F. 1963. Zoogeographic study of the Alcidae. Pages
85-111 _in_ J. L. Gressitt, ed. Pacific Basin biogeography, a
symposium. Pac. Sci. Congr. Proc. 10.

U.S. Bureau of Sport Fisheries and Wildlife. 1973. Semidi Islands
wilderness report. Semidi Islands, National Wildlife Refuge.
(Unpublished report)

U.S. Department of Commerce. 1964. United States Coast Pilot, No.
9, Pacific and Arctic Coasts, Cape Spencer to the Beaufort Sea.
Coast and Geodetic Survey, Washington, D.C. 330 pp.

Walker, E. P. 1923. Definite breeding record for the Aleutian tern
in southern Alaska. Condor 25:113-117.

Willet, G. 1914. Birds of Sitka and vicinity, Southeastern Alaska.
Condor 16:71-91.

Willet, G. 1918. Bird notes from Forrester Island, Alaska. Condor
20:85.

Williamson, F. S. L., and L. S. Peyton. 1963. Interbreeding of
glaucous-winged herring gulls in the Cook Inlet Region, Alaska.
Condor 65:28.

Status and Distribution of Breeding Seabirds of Southeastern Alaska, British Columbia, and Washington

by

David A. Manuwal

College of Forest Resources
University of Washington
Seattle, Washington 98195

and

R. Wayne Campbell

Provincial Museum
Victoria, British Columbia, Canada

Abstract

Current breeding seabird population estimates,
nest-site preferences, and population changes
are reviewed for southeastern Alaska,
British Columbia, and Washington. There are
19 species of seabirds and a minimum of
216,566 pairs breeding in British Columbia
and Washington. There are limited data on
breeding populations for southeastern Alaska.
Species diversity ranges from 17 species in
Alaska to 15 species in British Columbia and
14 species in Washington. Eighty percent of
all British Columbia seabirds breed on the
east coast of Queen Charlotte Islands and
the northwest coast of Vancouver Island.
The three most numerous species in British
Columbia are the fork-tailed storm-petrel,
_Oceanodroma furcata_ (31.3%); Cassin's
auklet, _Ptychoramphus aleuticus_ (24.6%); and
ancient murrelet, _Synthliboramphus antiquus_
(12.5%). In Washington, 74% (43,274 pairs) of
the seabird population resides on the Olympic
coast; the remaining 26% are in the San Juan
Island area. About 54% of this population
consists of the common murre _(Uria aalge)_ and
rhinoceros auklet _(Cerorhinca monocerata)_.
The rhinoceros auklet and glaucous-winged gull
_(Larus glaucescens)_ make up 97% of the total
seabird population of the San Juan Islands.
About 68% of all seabirds on the northeastern
Pacific coast are nocturnal, burrow or rock
crevice-nesting species. Currently available
population data are inadequate to determine
significant changes in population density for
most species. Suggested topics for future
research are presented.

The purpose of this paper is to discuss the known distribution, habitat, abundance, and status of breeding seabirds of the Alexander Archipelago in southeastern Alaska, the Province of British Columbia, Canada, and the State of Washington.

Even though several studies of the breeding biology of several seabird species in this area have been published, there have been few published surveys of known breeding colonies. In British Columbia the most extensive work has been done by the British Columbia Provincial Museum and the University of British Columbia (Drent and Guiguet 1961). Gabrielson and Lincoln (1959) summarized the available literature on Alaskan birds up to about 1958. Since then, no extensive surveys have been conducted in southeastern Alaska. The U.S. Department of the Interior (1972), in its environmental impact statement for the Trans-Alaska Pipeline, presented additional information on the seabirds of other parts of Alaska. In Washington, there are no published comprehensive surveys except those of Kenyon and Scheffer (1961) and unpublished surveys by the U.S. Fish and Wildlife Service and the University of Washington.

Table 1. _Taxonomic distribution of marine birds breeding
along the Pacific Coast of Washington, British Columbia, and
southeastern Alaska._

------------------------------------------------------------------------
Regions
---------------------------------------
British Southeastern Total
Family Common name Washington Columbia Alaska forms
------------------------------------------------------------------------
Hydrobatidae Storm-petrels 2 2 2 2
Phalacrocoracidae Cormorants 3 3 1 3
Haematopodidae Oystercatchers 1 1 1 1
Laridae Gulls and terns 2 2 3 4
Alcidae Auks, murres, puffins 6 7 9 9
Total 14 15 16 19
------------------------------------------------------------------------

Taxonomic Distribution of Marine Birds

There are 19 species of seabirds that breed along the Pacific coast of southeastern Alaska, British Columbia, and Washington (Table 1). Southeastern Alaska has the largest number (17) of species. Errors in species identification are most likely with the Larus gulls, particularly in southeastern Alaska where the herring gull _(L. argentatus)_ and glaucous-winged gull _(L. glaucescens)_ breed in mixed colonies (Patten and Weisbrod 1974). A similar situation exists in Washington where the western _(L. occidentalis)_ and glaucous-winged gulls intergrade (Scott 1971). Brandt's _(Phalacrocorax penicillatus)_ and double-crested cormorants _(P. auritus)_ are often difficult to identify from the air. This would be a problem in Washington and the southwest coast of Vancouver Island, where the two species are locally sympatric.

Southeastern Alaska

The area under consideration is the 400-km-long Alexander Archipelago (Fig. 1). This complex pattern of islands, bays, and inlets is characterized by extremely high precipitation and typical cool marine temperatures. Average annual precipitation in the Sitka area is 245.4 cm (1931-60), and the average annual temperature is 6.3°C (U.S. Weather Bureau 1974). As a consequence of this cool, humid environment, most of the islands are densely covered with conifers, chiefly Sitka spruce _(Picea sitkensis)_ and hemlock _(Tsuga heterophylla)_, and an almost impenetrable shrub cover composed of salmonberry _(Rubus spectabilis)_, elderberry _(Sambucus callicaipa)_, devil's club _(Echinopanax horridus)_, and three species of _Vaccinium_ (Heath 1915).

There are 16 species of marine birds breeding in the Alexander Archipelago. The major seabird breeding colonies are located at Glacier Bay and at St. Lazaria, Hazy, and Forrester islands (Fig. 1; Table 2). Published surveys of these colonies are available only for St. Lazaria (Willett 1912) and Forrester islands (Heath 1915; Willett 1915). Several authors have reported on seabirds from surrounding areas (Grinnell 1897, 1898, 1909; Swarth 1911, 1922, 1936; Patten 1974). There have been no surveys of seabirds of southeastern Alaska since before the 1940's (J. G. King, Jr., personal communication). However, since census data are available for only two colonies, we discuss them in more detail.

Table 2. _Population estimates of seabirds breeding on St.
Lazaria and Forrester islands, southeastern Alaska_ (data from
Willett 1912 and 1915).

St. Lazaria Island Forrester Island
----------------------------------------------------------------------
Number Percent Number Percent
Bird species of pairs of total of pairs of total
----------------------------------------------------------------------
Fork-tailed storm-petrel 2,000 8.0 10,000 6.0
Leach's storm-petrel 20,000 80.0 50,000 30.0
Pelagic cormorant 150 0.6 150 0.0
Black oystercatcher 4 0.0 50 0.0
Glaucous-winged gull 300 1.2 8,000 4.8
Herring gull 220 0.0
Common murre 300 1.2 20,000 12.0
Pigeon guillemot 150 0.6 300 0.0
Ancient murrelet 20,000 12.0
Cassin's auklet 2,000 1.2
Rhinoceros auklet 75 0.0 20,000 12.0
Horned puffin 12 0.0 1,100 0.7
Tufted puffin 2,000 8.0 35,000 21.0
Total 24,991 166,820

The studies by Willett (1912, 1915) and Heath (1915) provide some base-line information on species composition and abundance with which future studies on St. Lazaria and Forrester islands can be compared (Table 2). The somewhat greater species diversity on Forrester Island is primarily due to its greater size and more suitable soil type for ancient murrelets _(Synthliboramphus antiquus)_ and Cassin's auklets _(Ptychoramphus aleutica)_, species that are absent on St. Lazaria. Storm-petrels (_Oceanodroma_ spp.) are the most numerous species on both islands, but there are proportionately more storm-petrels (88%) on St. Lazaria than on Forrester (36%). On the other hand, there are many large, burrowing alcids on Forrester Island. Nearly a third of the birds on Forrester are rhinoceros auklets _(Cerorhinca monocerata)_, tufted puffins _(Lunda cirrhata)_, and horned puffins _(Fratercula corniculata)_.

The species composition of seabirds breeding on other islands is similar to that found on Forrester and St. Lazaria islands but less abundant. In Glacier Bay, for example, the only population data available are those provided by Patten (1974) for North Marble Island: pelagic cormorants, _Phalacrocorax pelagicus_ (30 pairs); black oystercatchers, _Haematopus bachmani_ (8); herring gulls (7); glaucous-winged gulls (500); common murres, _Uria aalge_ (18); pigeon guillemots, _Cepphus columba_ (60); horned puffins (4); and tufted puffins (30).

At the present time, it is impossible to draw any conclusions about changes in population density and distribution for most of the seabirds breeding in southeastern Alaska. Adequate data are available only for St. Lazaria and Forrester islands where Willet and Heath provided the only early extensive census data for this part of Alaska.

British Columbia

The rugged British Columbia coastline is characterized by 930 km of islands and inlets (Figs. 2, 3). With the exception of the inner southern portion, this coast is mostly uninhabited. The physical characteristics of the offshore islands are similar to those found off the Washington coast. Descriptions of some of these islands and the 15 species of breeding seabirds on them have been given by Drent and Guiguet (1961), Guiguet (1971), and Summers (1974).

A detailed analysis of British Columbia seabirds is not presented here since a more thorough analysis is in preparation by R. W. Campbell and R. H. Drent (manuscript). Instead, we present seabird population estimates available for the Province up to the summer of 1975; Tables 3 and 4 summarize these estimates for the five major portions of coastal British Columbia. The coast of British Columbia contains a myriad of small islands where there may be small numbers of breeding seabirds. Many of these have not been censused and are too numerous to include in Tables 3 and 4.

More than half of the breeding seabirds in British Columbia are found on the east coast of the Queen Charlotte Islands, and the fork-tailed storm-petrel _(Oceanodroma furcata)_ comprises more than half of that total. However, new unpublished data (K. Vermeer) for Triangle Island and the northwest coast of Vancouver Island indicate that the population figures in Table 3 for this area are underestimates. Nevertheless, these two regions have nearly 80% of all the breeding seabirds in the Province. This results from the very large populations of the rhinoceros auklet and tufted puffin on Triangle Island and the fork-tailed storm-petrel, ancient murrelet, and Cassin's auklet on various islands on the east coast of the Queen Charlotte Islands (Table 3).

Continuing surveys of breeding seabirds are being conducted by personnel of the British Columbia Provincial Museum and the Canadian Wildlife Service.

Washington State

_General Environment_

For this report, we have distinguished two major geographical areas in Washington where breeding seabirds are found--the western coast of the Olympic Peninsula and the San Juan Islands, including the Strait of Juan de Fuca.

On the Olympic Peninsula, seabirds breed on the offshore rocks, islands, and precipitous cliffs from Copalis Beach to Cape Flattery (Fig. 4). The offshore rocks and islands throughout this area (except Tatoosh Island) are now included in the Washington Islands National Wildlife Refuge. Most of the larger rocks and islands have dense stands of salmonberry, salal, and grasses, and a few support stands of stunted conifers (Fig. 5); most are inaccessible to man. The adjacent coast is dominated by the Olympic rain forest where the mean annual precipitation is about 337.1 cm (U.S. Weather Bureau 1956, 1965_a_, 1965_b_).

Because the San Juan Islands lie northeast of the Olympic Peninsula and east of Vancouver Island (Fig. 6) they are in a rain shadow; however, because of highly variable topography and aspect, most islands have a diverse assemblage of plant communities (Franklin and Dyrness 1973). Exposed south-facing slopes are occupied by grassland vegetation and frequently by scattered trees, usually _Pseudotsuga menziesii_ and _Arbutus menziesii_. Most of the seabird colonies are located on rather small exposed islands with short, grassy, shrubby vegetation. In general, these islands are not suitable for burrowing species.

Table 3. _Species composition, population estimates, and
distribution of seabirds in British Columbia._[5][6] (+ =
Present.)

Southwest Northwest West coast
Straits of coast of coast of of Queen
Georgia and Vancouver Vancouver Charlotte
Bird species Juan de Fuca Island Island Island
Fork-tailed storm-petrel + + 1,050
Leach's storm-petrel 10,000 + 1,800
Double-crested cormorant 1,058 0 0 0
Brandt's cormorant 370 0 0
Pelagic cormorant 2,174 336 3,350 1,456
Glaucous-winged gull 10,123 6,870 600 412
Common murre 16 3,000 0
Pigeon guillemot 1,029 204 250 358
Ancient murrelet 0 0 200
Cassin's auklet + 50,000 +
Rhinoceros auklet 1,200 + 10,000
Tufted puffin 1 154 20,000 190
Total 14,385 19,150 77,200 15,466

East coast Prince Rupert
of Queen to Queen Percent
Charlotte Charlotte Total of
Bird species Island Island birds total

Fork-tailed storm-petrel 97,100 + 98,160 31.3
Leach's storm-petrel 180 750 12,730 4.1
Double-crested cormorant 0 0 2,116 >1.0
Brandt's cormorant 0 0 370 >1.0
Pelagic cormorant 496 12 9,998 3.2
Glaucous-winged gull 866 540 29,534 9.4
Common murre 0 0 3,016 1.0
Pigeon guillemot 1,458 1,650 5,978 1.9
Ancient murrelet 42,150 4 42,354 13.5
Cassin's auklet 26,500 450 76,950 4.6
Rhinoceros auklet 300 200 11,700 3.7
Tufted puffin 0 42 20,388 6.5
Total 169,050 3,648 313,294 81.2

Table 4. _Breeding seabird population estimates for British
Columbia_[7][8]

---------------------------------------------------------------------------
Population Percent
Geographic location estimate of total
---------------------------------------------------------------------------
Straits of Georgia and Juan de Fuca 14,385 9.2
Southwest Coast of Vancouver Island 9,575 6.1
Northwest Coast of Vancouver Island 38,600 24.6
West Coast of Queen Charlotte Island 7,733 4.9
East Coast of Queen Charlotte Island 84,530 54.0
Prince Rupert to Queen Charlotte Strait 1,824 1.2
Total 156,647 100.0

In the Strait of Juan de Fuca, the two most important sites are Smith and Protection islands. Both are composed of glacial deposits and heavy sod that has developed under dense grassy vegetation (Fig. 7). Consequently, these two islands support most of the burrowing seabirds in the region. Unfortunately, both islands have historically been subjected to much human disturbance (Richardson 1961; Manuwal 1974).

The existing information on seabird colonies in both the coastal and San Juan Island areas has been largely derived from aerial surveys by the U.S. Fish and Wildlife Service. These surveys are inherently biased toward surface-nesting species such as gulls and cormorants. Population estimates for guillemots, auklets, storm-petrels, and puffins are less accurate. Some additional information obtained by direct island visitation has been provided by Kenyon and Scheffer (1961), Richardson (1961), Thoresen and Galusha (1971), G. Eddy (unpublished data), and D. A. Manuwal (unpublished data). Although other accounts of Washington seabirds are available, the references listed above are specifically oriented toward population assessment.

_Olympic Peninsula_

Despite the large number of offshore rocks, islets, and islands along the Pacific coast of Washington, significant seabird colonies are present only on about 30 islands. Since Table 5 summarizes the population estimates for 12 species of seabirds breeding on 24 major sites, it represents only the majority and not the total number of breeding seabirds on the Pacific coast of Washington. About 74% of the entire Washington seabird population resides on the coastal rocks and islands.

Major colony sites with more than 2,500 breeding pairs are Grenville Arch, Willoughby Rock, Destruction Island, Cake Rock, Carroll Island, and Bodelteh Island. More intensive censusing, especially of nocturnal burrowing species will undoubtedly raise the population estimates for these and other islands off the coast. About 54% of the total coastal population is composed of the common murre and rhinoceros auklet.

_San Juan Islands_

There are about 86 actual or potential seabird colony sites in this area; 25 (30%) are now considered important. Eleven islands are under Federal protection as National Wildlife Refuges. Part of Protection Island is owned by the Washington State Game Department to protect the largest rhinoceros auklet colony in the State. Most colony sites are on small islands with poorly developed soil which prevents burrowing species from using them. Consequently, the dominant species are surface nesters (such as gulls and cormorants) and rock-crevice nesters (like the pigeon guillemot). In all, about 31,000 seabirds of 7 species breed in the San Juan Island area. Breeding seabird population estimates for 49 of the 86 nesting sites are given in Table 6. Even though this does not represent all the colonies, it covers the most important islands and those islands where there appears to be potential for seabird breeding.

Table 5. _Estimated breeding seabird populations of the outer
coast of Washington_.[9] (Unpublished data from U.S. Fish and
Wildlife Service and University of Washington)

-----------------------------------------------------------------------
Species
-----------------------------------------------------------------------
Storm-petrels Cormorants
-----------------------------------------------------------------------

Fork- Uniden- Double-
Breeding site tailed Leach's tified crested Brandt's Pelagic
-----------------------------------------------------------------------
Copalis Rock -- -- 15 -- -- --
Point Grenville -- -- -- 60 30 80
Grenville Arch -- -- -- 30 20 --
Flat Rock -- -- 30 -- -- --
Split Rock -- -- -- 100 -- --
Willoughby Rock -- -- -- 80 40 15
South Rock -- -- -- -- -- 40
Abbey Islet -- -- -- -- -- 30
Destruction Island -- -- -- -- -- --
Middle Rock -- -- -- -- -- 25
North Rock -- -- -- -- -- --
Alexander Island -- -- -- -- -- 50
Rounded Island -- -- -- -- -- 25
Giant's Graveyard -- -- -- -- -- 10
Quillayute Needles -- -- -- 50 50 50
James Island -- 30 -- -- -- 40
Cake Rock -- 500 -- -- -- 150
Sealion Rock -- -- -- 70 -- 30
Carroll Island -- 3,100 -- -- -- 100
Ball Rock -- -- -- -- -- 50
White Rock -- -- -- -- -- 100
Ozette Island -- -- -- -- -- --
Bodelteh Island 1,900 -- -- -- -- 100
Tatoosh Island -- 25 -- -- -- 100
Total 1,900 3,655 45 390 140 995
-----------------------------------------------------------------------

-----------------------------------------------------------------
Species
-----------------------------------------------------------------
Gulls
-----------------------------------------------------------------
Black Glaucous-
oyster- winged Common Pigeon
Breeding site catcher Western western murre guillemot
-----------------------------------------------------------------
Copalis Rock -- 30 -- -- --
Point Grenville -- 165 40 1,100 --
Grenville Arch 1 60 -- 3,000 4
Flat Rock -- -- 60 300 --
Split Rock 1 150 -- 2,100 4
Willoughby Rock -- 150 -- 3,000 --
South Rock -- -- 50 -- --
Abbey Islet 3 -- 50 -- --
Destruction Island 12 350 -- -- 25
Middle Rock -- -- 25 -- 50
North Rock -- -- 25 -- --
Alexander Island 5 -- 225 -- --
Rounded Island -- 25 -- -- 1
Giant's Graveyard -- -- -- 150 --
Quillayute Needles -- -- 150 900 --
James Island -- -- 150 750 40
Cake Rock -- -- 600 300 12
Sealion Rock -- -- 250 -- --
Carroll Island 3 -- 550 -- --
Ball Rock 7 -- 150 -- --
White Rock -- -- 75 250 --
Ozette Island 1 -- 15 -- --
Bodelteh Island 2 -- 300 -- 5
Tatoosh Island -- -- 1,500+ 100 20
Total 35 930 4,215 11,950 161
-----------------------------------------------------------------

-------------------------------------------------------
Species
-------------------------------------------------------
Auklets
-------------------------------------------------------

Tufted
Breeding site Cassin's Rhinoceros puffin Total
-------------------------------------------------------
Copalis Rock -- -- -- 45
Point Grenville -- -- -- 1,475
Grenville Arch -- -- 3 3,118
Flat Rock -- -- -- 390
Split Rock -- -- -- 2,355
Willoughby Rock -- -- 25 3,310
South Rock -- -- -- 90
Abbey Islet -- -- 10 93
Destruction Island -- 10,940 350 11,677
Middle Rock -- -- -- 100
North Rock -- -- -- 25
Alexander Island -- -- 1,550 1,830
Rounded Island -- -- -- 51
Giant's Graveyard 50 150 -- 360
Quillayute Needles -- -- 350 1,550
James Island -- -- 20 1,030
Cake Rock -- 50 1,000 2,612
Sealion Rock -- -- 5 355
Carroll Island 25 250 2,400 6,428
Ball Rock -- -- 750 957
White Rock -- -- 100 525
Ozette Island -- -- -- 16
Bodelteh Island -- -- 750 3,057
Tatoosh Island 25? 25? 30 1,825
Total 100 11,415 7,343 43,274
-------------------------------------------------------

Table 6. _Breeding seabird population estimates for the San Juan
Islands and Strait of Juan de Fuca, Washington, 1973-75_.[10]

A: Double-crested
B: Pelagic
C: Black oystercatcher
D: Glaucous-winged gull
E: Pigeon guillemot
F: Rhinoceros auklet
G: Tufted puffin

------------------------------------------------------------------
Species
------------------------------------------------------------------
Cormorants
----------
Breeding site A B C D E F G Total
------------------------------------------------------------------
Bare Island -- 50 1 120 + -- 2 173
Barren Island -- -- -- -- -- -- -- 0
Battleship Island -- -- -- -- -- -- -- 0
Bird Rocks 30 -- + 320 -- -- -- 350
Cactus Island -- -- 1 -- -- -- -- 1
Castle Island -- -- -- -- 30 -- -- 30
Colville Island -- 40 1 1,000 -- -- -- 1,041
Danger Island -- -- -- 125 7 -- -- 132
Decatur Island -- -- -- -- -- -- -- 0
Eliza Island -- -- -- 3 1 -- -- 4
Eliza Rock -- -- -- 1 -- -- -- 1
Flat Top Island -- -- -- -- + -- -- +
Flower Island -- 17 -- 90 -- -- -- 107
Goose Island -- -- -- 60 -- -- -- 60
Gull Rock -- -- + 125 7 -- -- 132
Gull Reef -- -- -- -- -- -- -- 0
Hall Island -- -- 1 275 -- -- -- 276
Harbor Rock -- -- -- -- -- -- -- 0
Iceberg Island -- -- -- -- -- -- -- 0
Johns Island -- -- 1 -- -- -- -- 1
Long Island -- -- 8 80 -- -- -- 88
Low Island -- -- 1 75 17 -- -- 93
Lummi Rocks -- -- -- 4 -- -- -- 4
Matia Island -- -- -- -- + -- -- +
Mummy Rocks -- -- -- 55 -- -- -- 55
Minor Island -- -- -- 100 -- -- -- 100
O'Neal Island -- -- -- -- -- -- -- 0
Patos Island -- -- -- 20 + -- -- 20
North Peapod Island -- -- 1 220 2 -- -- 223
South Peapod Island -- -- 1 75 2 -- -- 78
Pearl Island -- -- -- -- -- -- -- 0
Pointer Island -- -- -- 58 2 -- -- 60
Protection Island 3 110 3 1,500 30 9,200 35 10,881
Puffin Island -- -- 1 350 15 -- -- 366
Ripple Island -- -- -- -- -- -- -- 0
Sentinel Island -- -- -- -- 10 -- -- 10
Sentinel Rock -- -- 1 -- -- -- -- 1
Skip Jack Island -- -- -- 75 20 -- -- 95
Smith Island -- 20 6 10 30 600 -- 666
Speiden Island -- -- -- -- -- -- -- 0
South Sister Island 2 11 1 131 -- -- -- 145
Middle Sister Island -- -- 1 22 -- -- -- 23
North Sister Island -- -- 2 412 3 -- -- 417
Viti Rocks 29 80 1 387 1 -- -- 498
Waldron Island -- -- -- -- 2 -- -- 2
Williamson Rocks -- 67 1 346 2 -- -- 416
Whale Island -- -- 1 70 -- -- -- 71
White Rock -- -- + 125 13 -- -- 138
Yellow Island -- -- -- -- -- -- -- 0
Total per species 64 395 34 6,234 194 9,800 37 16,758
Percent of total
population 0.4 2.3 0.2 37.2 1.2 58.5 0.2 100.0
------------------------------------------------------------------

The major colony sites with more than 250 breeding pairs are located at Protection and Smith islands, Bird Rocks, Colville Island, Hall Island, North and South Peapod rocks, Puffin Island, North Sisters, Viti Rocks, and Williamson Rocks (Fig. 6). Glaucous-winged gulls are the predominant species on all these islands except Protection and Smith islands, where there are large colonies of rhinoceros auklets. Rhinoceros auklets (65%) and glaucous-winged gulls (32%) make up 97% of the total San Juan Islands seabird population.

Nest-site Preferences

Food supply and availability of nest sites are two critically important factors influencing the distribution and abundance of seabirds. Whereas information on general diet composition is known for most seabird species, we know little about the availability of favored seabird prey. The dynamics of seabird food chains is reviewed elsewhere in these proceedings.

The nest-site preferences for seabirds of the northeast Pacific Ocean are given in Table 7, and Table 8 indicates the proportion of seabirds that belong to specific nest-site categories. These preferences, in conjunction with knowledge of the physical characteristics of seabird habitat, permit a partial explanation of the present distribution and abundance of seabirds. For example, if we compare the San Juan Island habitats with those of the Washington coast, it is apparent that there are more cliff-nesting species on the coast. This reflects the physical characteristics of the two habitats. There are few cliffs in the San Juan Islands, and those that exist are very unstable. Colony sites in the San Juan Islands are typically on low, flat islands. Glaucous-winged gulls are the most abundant nesting species there. Coastal islands, on the other hand, are either covered by dense vegetation or are large monolithic chunks of rock with few available flat areas. Population estimates for the Washington coast are heavily biased toward surface nesters, since most of the data have been gathered by aerial surveys. Consequently, the burrow and rock crevice categories are underestimated. The aerial survey is appropriate for only about 43% of the birds nesting on the Washington coast.

Table 7. _Nest-site preference for seabirds breeding from Cape
Fairweather, Alaska, to the Columbia River, Washington._

Nest-site type Bird species

Burrow-rock crevice
Diurnal Pigeon guillemot
Horned puffin
Tufted puffin

Nocturnal Fork-tailed storm-petrel
Leach's storm-petrel
Kittlitz's murrelet
Ancient murrelet
Cassin's auklet
Rhinoceros auklet

Open nests
Flat or slope Double-crested cormorant
Brandt's cormorant
Glaucous-winged gull
Herring gull
Western gull
Black oystercatcher

Cliff face Pelagic cormorant
Common murre
Black-legged kittiwake

Tree branch Marbled murrelet

Northern and southern British Columbia provide another good example of habitat availability as revealed through seabird population estimates. The population data are more comprehensive and have largely been gathered by island visitations. The islands in the northern portion are heavily vegetated and many have well-developed soil into which storm-petrels, auklets, and murrelets can burrow. Indeed, 96% of the seabird population consists of nocturnal, burrow-nesting species. In southern British Columbia, however, there are more open-nest species, particularly glaucous-winged gulls and cormorants.

Overall, 68% of the breeding seabirds found along the northeastern Pacific coast are nocturnal and nest in burrows or rock crevices (Table 8). The most conspicuous nesting birds such as gulls, cormorants, and murres, comprise only 22% of the total population. Consequently, our current estimates of breeding seabirds still underestimate the more secretive, nocturnal, burrow-nesting species.

Table 8. _Proportional nest-site preferences of Pacific coast
seabirds.[11]_

Estimated number of pairs

British Columbia Total
San Juan Washington
Site Northern Southern Islands coast Population

Burrow-rock crevice
Diurnal 1,849 11,334 231 7,504 20,918
Nocturnal 90,347 30,600 9,800 17,070 147,817
Open nests
Flat or slope 909 15,101 6,298 5,755 28,063
Cliff face 982 5,525 395 12,945 19,847

Total 94,087 62,560 16,724 43,274 216,645

Percent of population

British Columbia Total
San Juan Washington
Site Northern Southern Islands coast Percent

Burrow-rock crevice
Diurnal 2.0 18.1 1.4 17.3 9.7
Nocturnal 96.0 48.9 58.6 39.4 68.1
Open nests
Flat or slope 1.0 24.2 37.6 13.3 13.0
Cliff face 1.0 8.8 2.4 30.0 9.2

Population Changes

The available data are inadequate to detect changes in population distribution and density for most species (Table 9). In Washington, for instance, limited unsubstantiated information suggests an overall decline of the double-crested cormorant and tufted puffin in the San Juan Island area. Likewise, there seems to be an increase in glaucous-winged gulls there. In British Columbia, Drent and Guiguet (1961) were able to detect changes in some species. For example, they noted increases in the double-crested cormorant, pelagic cormorant, and glaucous-winged gull. No change was observed in the tufted puffin. Since then, the Brandt's cormorant has established a colony in Barkley Sound (Guiguet 1971). The data in southeastern Alaska are inadequate for all species except, perhaps, the Cassin's auklet which Gabrielson and Lincoln (1959) reported to be declining throughout Alaska. In short, no definitive statements can now be made concerning changes in seabird population numbers.

Species Accounts

Fork-tailed Storm-petrel _(Oceanodroma furcata)_

Storm-petrels are especially difficult to census because they are nocturnal, and the burrows and rock crevices where they breed are often difficult to locate, especially in mixed-species colonies. The census data are inadequate to determine whether there have been changes in population density and distribution. Indeed, the biology of this species is perhaps the least known of the North Pacific colonial seabirds. In southeastern Alaska, this species is outnumbered by at least 5 to 1 by the Leach's storm-petrel _(Oceanodroma leucorhoa)_. The reasons for this are poorly understood. There is some evidence that the numbers of breeding fork-tailed storm-petrels on Forrester Island may fluctuate drastically from one year to the next (Gabrielson and Lincoln 1959).

Leach's Storm-petrel _(Oceanodroma leucorhoa)_

Of the two subspecies of this petrel (_O. l. leucorhoa_ and _O. l. beali_), only _O. l. beali_ is found in southeastern Alaska. The _leucorhoa_ subspecies is more northerly in distribution. Where both fork-tailed and Leach's storm-petrels are sympatric, Leach's predominates; however, this relationship becomes more unpredictable in British Columbia and Washington. This species is undoubtedly widespread in the forested islands of the Alexander Archipelago.

Double-crested Cormorant _(Phalacrocorax auritus)_

The double-crested cormorant apparently does not breed in southeastern Alaska since Willett (1912), Gabrielson and Lincoln (1959), and S. Patten (personal communication) do not report breeding colonies for the area. The largest populations occur in southern British Columbia principally in the Gulf Islands, where 71% of all breeding double-crested cormorants are found (Table 10). According to Jewett et al. (1953), this species was less common in Puget Sound than was Brandt's cormorant, but is certainly not the case today (D. A. Manuwal, unpublished data). The only common cormorants in the San Juan Islands are the pelagic and double-crested species. The double-crested cormorant seems to have declined in numbers on both coastal and inland waters. On the basis of his observations, R. W. Campbell believes that this species is increasing in British Columbia.

Table 9. _Distribution and status of marine birds breeding
along the Pacific coast of Washington, British Columbia, and
southeastern Alaska._ (X = known to breed in the region;? = data
insufficient; + = evidence indicates an overall increase in size
of population; - = evidence indicates an overall decrease in size
of population; 0 = no population change.)

-----------------------------------------------------------------------------
British
Washington Columbia
---------------- ---------------
Family and species Common name Presence Status Presence Status
-----------------------------------------------------------------------------
Hydrobatidae
_Oceanodroma furcata_ Fork-tailed X ? X ?
storm-petrel
_O. leucorhoa_ Leach's storm-petrel X ? X -
Phalacrocoracidae
_Phalacrocorax auritus_ Double-crested X - X -
cormorant
_P. penicillatus_ Brandt's cormorant X ? X 0
_P. pelagicus_ Pelagic cormorant X ? X +
Haematopodidae
_Haematopus bachmani_ Black oystercatcher X ? X +
Laridae
_Larus glaucescens_ Glaucous-winged gull X + X +
_L. occidentalis_ Western gull X ? X ?
_L. argentatus_ Herring gull
_Rissa tridactyla_ Black-legged
kittiwake
Alcidae
_Uria aalge_ Common murre X ? X -
_Cepphus columba_ Pigeon guillemot X ? X +
_Brachyramphus
marmoratus_ Marbled murrelet X ? X ?
_B. brevirostris_ Kittlitz's murrelet
_Synthliboramphus
antiquus_ Ancient murrelet X ?
_Ptychoramphus aleuticus_ Cassin's auklet X ? X ?
_Cerorhinca monocerata_ Rhinoceros auklet X ? X +
_Fratercula corniculata_ Horned puffin
_Lunda cirrhata_ Tufted puffin X - X 0
Total species 14 15
-----------------------------------------------------------------------------

---------------------------------------------------------------------
Southeastern
Alaska
----------------
Family and species Common name Presence Status
---------------------------------------------------------------------
Hydrobatidae
_Oceanodroma furcata_ Fork-tailed X ?
storm-petrel
_O. leucorhoa_ Leach's storm-petrel X ?
Phalacrocoracidae
_Phalacrocorax auritus_ Double-crested
cormorant
_P. penicillatus_ Brandt's cormorant ?
_P. pelagicus_ Pelagic cormorant X ?
Haematopodidae
_Haematopus bachmani_ Black oystercatcher X ?
Laridae
_Larus glaucescens_ Glaucous-winged gull X ?
_L. occidentalis_ Western gull
_L. argentatus_ Herring gull X ?
_Rissa tridactyla_ Black-legged X ?
kittiwake
Alcidae
_Uria aalge_ Common murre X ?
_Cepphus columba_ Pigeon guillemot X ?
_Brachyramphus
marmoratus_ Marbled murrelet X ?
_B. brevirostris_ Kittlitz's murrelet X ?
_Synthliboramphus
antiquus_ Ancient murrelet X ?
_Ptychoramphus aleuticus_ Cassin's auklet X -
_Cerorhinca monocerata_ Rhinoceros auklet X ?
_Fratercula corniculata_ Horned puffin X ?
_Lunda cirrhata_ Tufted puffin X ?
Total species 16
---------------------------------------------------------------------

Brandt's Cormorant _(Phalacrocorax penicillatus)_

Brandt's cormorant is the least abundant of the three cormorant species that nest in the study area. Washington is at the northernmost edge of the breeding distribution of this species. Only one more northerly colony exists, on Sartine Island off Vancouver Island (Vermeer et al. 1976). Brandt's cormorant comprises about 85% of the cormorant population in Oregon (U.S. Fish and Wildlife Service, unpublished data). However, in Washington it is only about 9% and in British Columbia 3% of the total cormorant population.

Table 10. _Estimated seabird populations breeding
from Cape Fairweather, Alaska, to the Columbia River,
Washington._[12][13][14] (? = present in unknown
numbers; - = inadequate data.)

-----------------------------------------------------------------------------
Northern Southern San Juan Washington Total all
British British Islands coast regions
Columbia Columbia

Bird species Population Population Population Population Population
-----------------------------------------------------------------------------
Fork-tailed
storm-petrel 49,080 ? 0 1,900 50,980
Leach's
storm-petrel 1,365 5,000 0 3,655 10,020
Double-crested
cormorant 0 1,058 64 390 1,512
Brandt's cormorant 0 185 0 140 325
Pelagic cormorant 982 4,017 395 995 6,389
Glaucous-winged gull 909 13,858 6,234 4,215 25,216
Western gull 0 ? 0 930 930
Common murre 0 1,508 0 11,950 13,458
Pigeon guillemot 1,733 1,256 194 161 3,345
Ancient murrelet 21,177 0 0 0 21,177
Cassin's auklet 13,475 25,000 0 100 38,575
Rhinoceros auklet 5,250 6,000 9,800 11,415 27,065
Horned puffin 0 0 0 0 0
Tufted puffin 116 10,078 37 7,343 17,574
Total 94,087 67,960 16,724 43,194 216,566
--------------------------------------------------------------------------

-----------------------------------------------------------------------------
Northern Southern San Juan Washington Total all
British British Islands coast regions
Columbia Columbia

Bird species Percent Percent Percent Percent Percent
-----------------------------------------------------------------------------
Fork-tailed
storm-petrel 52.2 - - 4.4 23.5
Leach's
storm-petrel 1.5 8.0 - 8.5 4.6
Double-crested
cormorant - 1.7 >0.1 >0.1 >0.1
Brandt's cormorant - >0.1 - >0.1 >0.1
Pelagic cormorant 1.0 6.4 2.4 2.3 3.0
Glaucous-winged gull 1.0 22.2 37.3 9.8 11.6
Western gull - - - 2.2 >0.1
Common murre - 2.4 - 27.7 6.2
Pigeon guillemot 1.8 2.0 1.2 >0.1 1.5
Ancient murrelet 22.5 - - - 9.8
Cassin's auklet 14.3 40.0 - >0.1 17.8
Rhinoceros auklet 5.6 >0.1 58.6 26.4 12.5
Horned puffin - - - - -
Tufted puffin >0.1 16.1 >0.1 17.0 8.1
---------------------------------------------------------------------------

Comparing information in Jewett et al. (1953) with the current situation, it is apparent that there has been a drastic change in the distribution and probably in the numbers of this species in Washington. Today, there are no Brandt's cormorant colonies in the San Juan Islands or Strait of Juan de Fuca. Yet Jewett et al. (1953) reported colonies at Bellingham Bay and on Lopez and Matia islands. We have observed juvenile Brandt's cormorants in the San Juan Islands during the summer. This species may be particularly susceptible to human disturbance, since all three areas listed above are heavily used in the summer for recreation.

Pelagic Cormorant _(Phalacrocorax pelagicus)_

The distribution of breeding colonies of the pelagic cormorant is strongly determined by the availability of the steep cliffs on which it constructs its nest. This is the only common cormorant in southeastern Alaska. Throughout its extensive range, this species is generally found breeding in small numbers. Nothing is known about fluctuations in its numbers in Alaska.

This species is common in both British Columbia and Washington; nesting sites are of the same type as those in Alaska except in the San Juan Islands, where 200-300 birds nest on cliff faces composed of glacial deposits. Here, there is frequent nest loss due to slippage off the cliff face; this loss is especially severe on Smith and Protection islands. There do not appear to be any changes in the distribution of pelagic cormorants, but an accurate assessment of abundance is impossible from the data currently available.

Glaucous-winged Gull _(Larus glaucescens)_

The glaucous-winged gull is the characteristic gull of southeastern Alaska and British Columbia. In Washington, it is the dominant gull in the San Juan Island area but interbreeds with the western gull on the Washington outer coast from Tatoosh to Copalis Beach (Scott 1971). In Alaska, it is widely distributed and locally abundant on Forrester Island, St. Lazaria, and throughout Glacier Bay (S. Patten, personal communication). The biology of this species has been extensively studied in the southern part of its range, especially by Vermeer (1963) and James-Veitch and Booth (1954). The only study of the breeding biology of this species in southeastern Alaska is by Patten (1974) for Glacier Bay. Glaucous-winged gulls are apparently increasing in British Columbia (R. W. Campbell, unpublished data) and in Washington (T. R. Wahl, personal communication). This increase is undoubtedly a result of the proximity of breeding colonies to garbage dumps and commercial fishing fleets in both Canada and the United States. Little is known about changes in populations of gulls in southeastern Alaska.

Western Gull _(Larus occidentalis)_

The western gull is the common breeding gull of the Washington outer coast; however, there is increased interbreeding with glaucous-winged gulls northward from Destruction Island to Tatoosh Island. The percentage of glaucous-winged gulls steadily increases until Vancouver Island and the Strait of Juan de Fuca, where western gulls are rare. Population estimates of gulls on the outer coast of Washington are derived primarily from aerial flights. This makes identification of gulls difficult, and in view of the amount of interbreeding, it is probably impossible to classify many of the breeding gulls as to species. Western gulls appear to be increasing in the Grays Harbor area (G. D. Alcorn, personal communication).

Herring Gull _(Larus argentatus)_

The herring gull is typically found in inland Alaska but can be found uncommonly along the coast of southeastern Alaska, where it often forms mixed colonies with glaucous-winged gulls. These two species apparently hybridize where they are sympatric (Williamson and Peyton 1963; Patten and Weisbrod 1974; Patten 1974).

Black-legged Kittiwake _(Rissa tridactyla)_

The black-legged kittiwake is found only in the northern portions of southeastern Alaska. It apparently is a common breeding bird in Glacier Bay National Monument (S. M. Patten, Jr., personal communication). No population estimates are available for this species other than that it is locally abundant.

Common Murre _(Uria aalge)_

Common murres are common in southeastern Alaska and the coast of Washington but breed only in small numbers in British Columbia and are absent in the San Juan Islands. Since this species usually prefers cliffs or the tops of inaccessible rocks, they are probably limited by island topography in British Columbia, and are most certainly so limited in the San Juan and Gulf Island groups.

In Alaska, common murres breed in unknown numbers in Glacier Bay and in large numbers on St. Lazaria, Forrester, and the Hazy islands. No data on population changes are available for any of the three regions.

Pigeon Guillemot _(Cepphus columba)_

The pigeon guillemot is common throughout the region from Cape Fairweather to Washington. Even though it is not truly colonial, it may be locally abundant where there are suitable nest sites. Since these nest sites are usually difficult to find, population estimates are seldom accurate, usually being conservative. It is evident that guillemots appear to be small in number when compared with other seabirds nesting at major colony sites in the north Pacific region (Table 10). This disparity may be exaggerated by the difficulty of censusing guillemots.

Marbled Murrelet _(Brachyramphus marmoratus)_

Since the marbled murrelet has been found to nest in coniferous forests (Binford et al. 1975), traditional census techniques are unsuitable. This species is common in southeastern Alaska (Gabrielson and Lincoln 1959), in British Columbia (Drent and Guiguet 1961), and in Washington (Jewett et al. 1953).

Kittlitz's Murrelet _(Brachyramphus brevirostris)_

The difficulties in assessing breeding populations of Kittlitz's murrelet are the same as those for the marbled murrelet. This species nests on the ground at high elevation near the coast (Bailey 1973). The largest concentrations are in the vicinity of Glacier Bay National Monument (Gabrielson and Lincoln 1959). They are not found breeding in Washington or British Columbia.

Ancient Murrelet _(Synthliboramphus antiquus)_

Ancient murrelets appear to be locally common throughout southeastern Alaska. Their presence is probably strongly dependent upon a suitable soil in which to excavate burrows. The only available population estimates are those by Willett (1915) for Forrester Island (Table 1). Censusing this species is especially difficult because its burrows are easily confused with those of Cassin's auklet. There are no studies of this species in southeastern Alaska; however, it has been well studied in the Queen Charlotte Islands to the south by Sealy (1975).

Cassin's Auklet _(Ptychoramphus aleuticus)_

A synthesis of literature and unpublished observations led Gabrielson and Lincoln (1959) to conclude that Cassin's auklet has greatly decreased in numbers and is not abundant anywhere in Alaska. They also concluded that the colony on Forrester Island (Table 1) was the only well-documented colony in southeastern Alaska. Fishermen in the southeastern Alaska area occasionally see this species (M. E. Isleib, personal communication), but it is apparently still uncommon though more widespread than just Forrester Island. The nocturnal habits and burrowing in dense vegetation makes censusing this species very difficult. Nothing is known about the ecology of this species in Alaska.

Rhinoceros Auklet _(Cerorhinca monocerata)_

Rhinoceros auklets seem to be found breeding only on islands where there is a well-developed soil in which to excavate their extensive burrows. From the limited evidence available, it appears that the largest rhinoceros auklet populations probably are to be found in southeastern Alaska. Willett (1912) found a very large population on Forrester Island (Table 2), and the species has been found in the summer in the Barren Islands east of Kodiak Island (E. P. Bailey, personal communication). More intensive surveys of the Alexander Archipelago will probably reveal other populations of this species.

This species is less common in British Columbia than either Alaska or Washington. A possible reason for this is lack of suitable nesting areas. In Washington, the two largest colonies are at Protection Island in the Strait of Juan de Fuca and Destruction Island on the outer coast. Smaller numbers exist on other coastal islands and on Smith Island in the Strait of Juan de Fuca. The Smith Island colony is an interesting one since it appears that early human disturbance in the late 19th or early 20th century eliminated the species from the island. In their discussion of Smith Island, Jewett et al. (1953) made no mention of auklets, only of puffins and guillemots. Couch (1929) did not record the species in 1925. The colony now numbers about 600 pairs.

Horned Puffin _(Fratercula corniculata)_

Although the horned puffin is one of the most abundant seabirds in other parts of Alaska, it is much less abundant in the southeastern portion. In addition to the information discussed by Sealy (1973), it now appears that this species may breed as far south as Triangle Island, British Columbia (K. Vermeer, personal communication; D. A. Manuwal, personal observation). Here, as on Forrester Island, it is greatly outnumbered by the tufted puffin. No data are available on the breeding or status of this species in the study area.

Tufted Puffin _(Lunda cirrhata)_

The tufted puffin is found breeding on scattered islands throughout the region. The largest known colonies are on Forrester Island, Alaska, Triangle Island, British Columbia, and Carroll Island, Washington. It is notably absent from most of the gulf and San Juan Islands. Even though puffins have apparently never been numerous in the San Juan Islands, their population has noticeably declined during the past 35 years. For example, Jewett et al. (1953) reported a colony of 50 pairs on Bare Island in 1937, but in 1973 only 2 pairs were counted (D. A. Manuwal, unpublished data). Likewise, in 1915 there were more than 250 pairs on Smith Island, but by 1916 there were only 75 pairs (Jewett et al. 1953). The decline is attributed to rapid erosion of the glacial-deposit cliffs. There are no puffins on Smith Island today, and the largest colony in the Puget Sound area is the 35 pairs on Protection Island (D. A. Manuwal, unpublished data).

Discussion

The total minimum estimate of the breeding seabird populations of British Columbia and Washington is 216,500 pairs (Table 10). No comprehensive estimates are available for breeding seabirds of southeastern Alaska. It is likely, however, that the number of breeding seabirds in the Alexander Archipelago may be equal to (or exceed) the populations of both British Columbia and Washington. Data are desperately needed from that area. Of the total seabird population in the study area (Table 10) 43% reside in northern British Columbia. The Washington State population represents 28% of the total. Fork-tailed storm-petrels comprise almost 25% of all the breeding seabirds in the area under consideration. The Cassin's auklet is the next most numerous species (18% of the total).

It is apparent that current data are, for the most part, inadequate for assessing anything but catastrophic changes in seabird breeding colonies. This inadequacy is due to inadequate censusing because of excessive reliance upon aerial surveys; in the past, this has often been a result of insufficient funding.

Of the several threats facing seabird populations, none may be as important as oil pollution. A general review of this subject is presented elsewhere by Vermeer and Vermeer (1975). It is apparent from this review that the most vulnerable species are those that dive beneath the sea surface, including all the alcids and cormorants breeding along the coast that are discussed in this paper. This group makes up almost 60% of all the breeding seabirds in this area. Unfortunately, our knowledge of several of these species is scanty and our current census techniques are unsuitable for most of these birds.

Studies of the changes in seabird numbers have been made in other oceans. For example, in Great Britain (Bourne 1972_a_, 1972_b_; Harris 1970), eastern Canada (Nettleship 1973), and the Atlantic coast of the United States (Kadlec and Drury 1968), two major trends seem apparent. First, there is an overall decline in alcid and tern numbers. The decline in auks may be due to their extreme vulnerability to oil pollution (Bourne 1972_a_, 1972_b_; Vermeer and Vermeer 1975). The Atlantic puffin, however, may be suffering the additional effects of gull cleptoparasitism (Nettleship 1972). Secondly, there seems to be an increase in gull populations on both sides of the Atlantic, particularly the herring gull and black-legged kittiwake.

Compared with the Atlantic coast of North America and northern Europe, the data base for seabird populations of the Pacific coast is poor. The fragmentary evidence now available indicates that there may be small population increases in the western and glaucous-winged gulls and range extensions of the Brandt's and double-crested cormorants and of the rhinoceros auklet (Scott et al. 1974). Whether these changes represent actual population increases or displacements remains unclear. The remote locations of most of the large Pacific seabird colonies may provide unofficial protection from human interference. Intensive surveys are needed to establish base-line inventories in these areas.

As a consequence of this first comprehensive review of the status of breeding marine birds of the northeast Pacific coast of North America, we recommend the following future research topics as necessary for the conservation of this great international resource.

• Seabird colony census techniques should
be refined since almost 68% of the seabirds
in this area are nocturnal and nest in burrows.
The present reliance on aerial censusing,
although economical, is inadequate to
census most breeding seabird populations;
more on-site surveys are needed. For surface-nesting
species and diurnal, burrowing
species, studies on species specific activity
cycles are needed so that census data
can be corrected for birds not observed at
the colony. For nocturnal, burrowing
species seasonal burrow occupancy rates
must be determined so that burrow counts
can be corrected for inactive burrows.

• Comprehensive surveys should be made
every 3-5 years.

• In 1980 a coordinated breeding bird survey
of the entire Pacific coasts of Mexico,
Canada, and the United States should be
conducted.

• Specific islands where key populations
exist should be carefully monitored for
subtle changes in population density or
species composition.

• Increased study of the breeding biology of
seabirds should be carried out so that base-line
reproductive characteristics can be
determined.

• Detailed studies of the effects of human
disturbance should be made, especially for
species that breed near large coastal cities
or marine recreation areas.

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FOOTNOTES:

[5] Data are minimum estimates of pairs and do not include breeding sites with less than 100 birds.

[6] Does not include the black oystercatcher, marbled murrelet, and western gull.

[7] Estimates only for colonies of 100 or more birds.

[8] Estimates are in number of pairs.

[9] Estimates are number of pairs.

[10] Estimates are numbers of pairs.

[11] Data for southeastern Alaska were inadequate to enable estimates of breeding pairs.

[12] Population estimates are minimum and represent numbers of pairs.

[13] Does not include the following species for which population estimates are lacking: black oystercatcher, herring gull, black-legged kittiwake, marbled murrelet, Kittlitz's murrelet.

[14] Data for southeastern Alaska were inadequate to enable estimates of breeding pairs.

THE BIOLOGY AND ECOLOGY OF MARINE BIRDS IN THE NORTH

Trophic Relations of Seabirds in the Northeastern Pacific Ocean and Bering Sea

by

David G. Ainley

Point Reyes Bird Observatory
Stinson Beach, California 94970

and

Gerald A. Sanger[15]

National Marine Fisheries Service
Marine Mammal Division
Seattle, Washington

Abstract