FOOTNOTES:

[2] Present address: U.S. Fish and Wildlife Service, 500 NE Multnomah Street, Portland, Oregon 97232.

[Breeding Distribution and Status of Marine Birds in the Aleutian Islands, Alaska]

by
Palmer C. Sekora [3]

U.S. Fish and Wildlife Service
Kailua, Hawaii

G. Vernon Byrd [4]

U.S. Fish and Wildlife Service
Adak, Alaska

and

Daniel D. Gibson

University of Alaska
Fairbanks, Alaska

Abstract

Seabird population estimates are generally lacking for the 1,800-km-long Aleutian Islands. Only the locations of the larger colonies are known, and for these there are only imprecise estimates of colony sizes and often even of species composition. Changes in the status of several species and populations resulting from geologic and marine actions and from human intrusions are evident. Accounts are given for 25 species of marine birds breeding in these islands.

The 1,800-km-long chain of islands known as the Aleutians provides nesting habitat for various species of marine birds, including three species of Procellariiformes and three of cormorants (Phalacrocorax spp.), one species of gull (Larus glaucescens), both kittiwake species (Rissa spp.), two species of terns (Sterna spp.), and at least 13 species of alcids.

Seabird population estimates of known accuracy are lacking for this isolated area. Locations of larger colonies of breeding seabirds are known, however, and sufficient data are available to place colonies in broad size ranges. Published information on the breeding biology of marine birds is also lacking from the Aleutians, but some studies are under way. The distribution of nesting marine birds away from the nesting cliffs is totally unknown.

Introduced predators, primarily arctic foxes (Alopex lagopus), are now found on nearly every island. Breeding marine bird populations have suffered drastic reductions as a result. They have probably also changed because of natural habitat modifications caused by earthquakes, volcanic eruptions, tidal waves, and marine erosion.

The purpose of this paper is to summarize the known present distribution and status of breeding marine birds in the Aleutian Islands.

Description of the Aleutian Islands

The Aleutian Islands form an arc that separates the Bering Sea and the north Pacific Ocean (Fig. 1). The island chain extends from the tip of the Alaska Peninsula to within 483 km of the Commander Islands of Siberia. The chain contains more than 200 islands—the peaks of a submarine volcanic mountain range. Volcanic activity and earthquakes occur regularly.

Weather is characterized by perpetual overcast, dense summer fog, high-velocity winds, and mild temperatures with low annual and diurnal variations. The sea is ice-free year-round except in extremely cold winters, when the arctic ice pack may reach the extreme northern islands.

The Aleutians are treeless except for a few introduced, stunted spruces. Woody shrubs are restricted to the most northern islands on each end of the Chain. Mosses, lichens, club mosses, and heaths are common ground-cover plants, and taller grasses, sedges, and umbellifers constitute the overstory. Hulten (1960) provided a list of terrestrial plants found in the Aleutians. Amundsen and Clebsch (1971) discussed terrestrial plant ecology at Amchitka, central Aleutians. The marine plant communities around the islands are fairly diverse. Lebednik et al. (1971) described marine algal communities at Amchitka.

The easternmost Aleutian island, Unimak, has a mammalian fauna like that of the Alaska Peninsula, including brown bear (Ursus arctos), caribou (Rangifer tarandus), wolf (Canis lupus), and wolverine (Gulo gulo). West of Unimak, red foxes (Vulpes fulva) occurred historically as far as Umnak, and arctic foxes were apparently on Attu when the Russians came in 1741 (Murie 1959). Except for man and dog, no land mammals occurred between Umnak and Aggatu islands. Arctic foxes, introduced before 1930 for fur farming, still roam almost every island. Norway rats (Rattus norvegicus) were introduced on many islands when ships were wrecked or as a result of military activities during World War II.

Sea otters (Enhydra lutris) have repopulated most of the Aleutians after being nearly extirpated by 1900. Rookeries of Steller's sea lion (Eumetopias jubata) are scattered throughout the Aleutians during summer, and numerous harbor seals (Phoca vitulina) haul out on beaches and offshore rocks.

All five species of Pacific salmon (Oncorhynchus spp.) occur near the islands, and at least four of them (all but O. tshawytscha) spawn in Aleutian streams. Dolly Varden (Salvelinus malma) and three-spine sticklebacks (Gasterosteus aculeatus) are found nearly everywhere there is fresh water. The marine environment provides habitat used by at least 77 species of fish (Isakson et al. 1971). O'Clair and Chew (1971) furnished a recent reference to littoral macrofauna at Amchitka.

About 200 species of birds have been recorded in the Aleutians (Aleutian Islands National Wildlife Refuge, unpublished data). Many of these are windblown stragglers from both North America and Asia; only 59 species breed on the islands. Although seabirds make up less than half (26 species or 44%) of the breeding birds, they may compose more than 90% of the breeding avian biomass.

Ornithological Investigations in the Aleutians

Published ornithological information from the Aleutian Islands is relatively scarce. G. W. Steller, naturalist on Vitus Bering's 1741 expedition to Alaska, was the first person to record ornithological information in the islands (Stejneger 1936). More than a century passed before W. H. Dall (1873, 1874) published the next papers dealing with birds in the Aleutians. In 1878, the U.S. Army Signal Corps sent L. M. Turner to the Aleutians to set up weather stations at several locations. Turner kept notes on birds at various locations in the Aleutians and published two papers (1885, 1886) on his observations. Turner's data (1886) provided the first report based on extended and widespread observations in the area. E. W. Nelson, who replaced Turner, also provided data on birds (Nelson 1887).

In 1906, A. C. Bent came to the Aleutians specifically to look for birds, and he and Alexander Wetmore recorded birds throughout the island chain (Bent 1912). A. H. Clark (1910) provided a valuable record of his observations in the Near Islands. All these workers recorded birds in several locations, but none provided data on more than a very few seabird colonies.

Fig. 1. The Aleutian Islands.

O. J. Murie, U.S. Biological Survey, made the most complete survey of the Aleutians (Murie 1959). He specifically recorded seabird colonies, spending parts of four summers in the area. Murie visited every large Aleutian island and most small ones. He recorded nearly every major colony of cliff-nesting or talus-nesting seabirds known in the Aleutians, but seldom gave sizes of colonies, and separate colonies on a particular island were often not differentiated.

World War II brought several ornithologists to the Aleutians. Cahn (1947), Sutton and Wilson (1946), Taber (1946), and Wilson (1948) provided accounts of birds observed at specific locations. After the war, Fish and Wildlife Service personnel—including I. N. Gabrielson (Gabrielson and Lincoln 1959), K. W. Kenyon (Kenyon 1961), and R. D. Jones (Refuge Narrative Reports 1949-1970)—recorded observations of breeding seabirds at several locations in the Aleutians. Investigations associated with Atomic Energy Commission nuclear testing at Amchitka Island provided the first ecological study of avifauna of an Aleutian island (White et al. 1977). Byrd et al. (1974) provided a list of birds at Adak.

In 1971, the Near Islands were surveyed by U.S. Fish and Wildlife personnel in a Cape Cod dory. In 1972, the Aleutian Islands National Wildlife Refuge obtained a vessel, the Aleutian Tern, which allowed visits to all parts of the island chain. That year, nearly every large island as far west as Buldir was visited, and seabird colonies were mapped. Every island has been visited at least once since 1972.

Methods

In estimating the current status of seabirds in the Aleutians, all available data were considered. Most of the information used, however, is from surveys conducted by the U.S. Fish and Wildlife Service (1970-75, unpublished data). Because these surveys only incidentally included Unimak, Akun, Akutan, Unalaska, and Umnak islands, data for these areas are almost totally lacking. Data for Bogoslof, Adak, Amchitka, Buldir, Agattu, Nizki, Alaid, and Attu are most accurate because fairly intensive investigations have been conducted there since 1970.

The available data are of unknown accuracy. The method used by most investigators who have surveyed areas in the Aleutians for seabird colonies has been to circle islands in a ship or small boat; when a colony was encountered, they simply estimated the number of birds they saw at the time. The accuracy of the estimates is affected by weather, distance from the colony, density of birds, ability and experience of the observer, and other variables. Estimates of kittiwakes and cormorants should be the most accurate, since nests were actually counted. Murres (Uria spp.) are readily visible on the cliffs, but the percentage of breeders on the cliffs at a particular time of day during a particular part of the breeding season is not known. Auklet numbers are perhaps hardest to estimate, since swirling "clouds" of birds are encountered.

Even when the estimates of birds seen are assumed to be accurate, data interpretation is complex. Lack of information on diurnal rhythms adds difficulty to data interpretation. Counts of burrow-nesting birds (e.g., puffins) have been inaccurately interpreted because of the lack of understanding of their nesting ecology. Gulls (Larus spp.), terns, and jaegers (Stercorarius spp.) are not well known since shore parties have seldom investigated island interiors. Nocturnal species (e.g., ancient murrelet, Synthliboramphus antiquus, and storm-petrels, Oceanodroma spp.) are perhaps the least known. Since only crude estimates of colony sizes are available, broad limits are used in this paper to describe known colonies.

Status and Distribution of Breeding Seabirds

Even from the sparse literature available, it is apparent that some seabird populations are now drastically different from those in the Aleutians around 1900. Changes in nesting habitat due to volcanic eruptions, tidal waves, marine erosion, and earthquakes have occurred for centuries, and colonial nesting bird populations have fluctuated accordingly. In addition, native Aleuts used marine birds and their eggs for food and their skins for clothing, but the Aleuts were so diminished in numbers by 1900 that they have had little recent effect on the bird populations.

From about 1900 to 1936, arctic foxes were introduced to most of the Aleutians for fur farming. The foxes lived on birds in summer, and some species (e.g., Aleutian Canada geese, Branta canadensis leucopareia) were wiped out wherever foxes were introduced. Ground-nesting and some burrow-nesting seabirds were also drastically reduced or extirpated on many islands.

During World War II the thousands of troops in the Aleutians brought dogs and cats to some of the islands as pets, and many of the animals were set free when the men departed. The military also accidentally introduced Norway rats to some of the islands. Their role in seabird population reductions is unknown.

Figures 2-15 (pages [40]-46) present data on the distribution of populations of birds that have survived the foxes and other introduced predators. An annotated list of seabirds breeding in the Aleutians follows.

Annotated List of Species

Northern fulmar (Fulmarus glacialis)

Northern fulmars breed on only three islands: Buldir (200 pairs), Gareloi (1,500 pairs), and Chagulak (more than 100,000 pairs). Fulmars were apparently much more widespread formerly (Murie 1959; Turner 1886). Introduced foxes were probably involved in the decline.

Fork-tailed Storm-petrel and Leach's Storm-petrel (Oceanodroma furcata and O. leucorhoa)

The distribution of storm-petrels is poorly known due to their nocturnal behavior near the nesting colonies. The presence of birds has generally been noted by finding them aboard ships anchored near islands after darkness. Population estimates are not available for any colonies, so symbols used in Fig. 3 indicate probable numbers of breeding birds. In few cases have active burrows or crevices been discovered. Storm-petrels were formerly much more common. Murie (1959) and John L. Trapp (personal communication) found large numbers of storm-petrel remains in fox dens. Most present breeding colonies are probably confined to offshore islets and fox-free islands.

Double-crested Cormorant, Pelagic Cormorant, and Red-faced Cormorant (Phalacrocorax auritus, P. pelagicus, and P. urile)

Double-crested cormorants breed as far west as the Islands of Four Mountains. The colonies vary in size from a few to 25 pairs. Pelagic and red-faced cormorants nest from Amak to Attu on nearly every island. Relative abundance of the two in mixed colonies varies between areas as well as from year to year. Red-faced cormorants tend to nest in colonies mixed with kittiwakes and murres, but pure colonies also occur. Pelagic cormorants occupy isolated, small colonies, but they also nest with kittiwakes and murres and are often found with red-faced cormorants. By far the densest concentration of cormorants occurs in the Near Islands, especially at Attu, where an estimated 77,000 birds were seen in 1970. In the Aleutians as a whole, red-faced cormorants outnumber pelagic cormorants, and double-crested cormorants make up only a very small percentage of the breeding population.

Parasitic Jaeger (Stercorarius parasiticus)

The distribution of jaegers is poorly known because investigators have spent little time ashore on most islands. Murie (1959) found jaegers on a number of islands, and most of the data in Fig. 5 are his. Population estimates are available only for Amchitka (25 pairs; White et al. 1977) and Buldir (30-40 pairs; G. V. Byrd, unpublished data).

Glaucous-winged Gull (Larus glaucescens)

Glaucous-winged gulls no longer nest on islands where foxes occur except where islands in lakes are available. Most colonies are on offshore rocks or islets and range in size from a few pairs to over 200 pairs, and occasionally more. They are found throughout the Aleutians, but the largest known colonies are at Bogoslof (500 pairs) and Buldir (250 pairs).

Black-legged Kittiwake and Red-legged Kittiwake (Rissa tridactyla and R. brevirostris)

Black-legged kittiwakes breed locally in every major island group, usually mixed with murres and cormorants. The large colonies contain over 25,000 birds, but colonies of less than 50 pairs also occur. Red-legged kittiwakes breed only on Buldir and Bogoslof. They are remnants of a previously more widespread population.

Arctic Tern and Aleutian Tern (Sterna paradisaea and S. aleutica)

Terns breed locally in each island group. Both species occur at Attu, Amchitka, Adak, and Umnak, but only arctic terns are found at Nizki. Factors limiting distribution are unknown. Colonies vary in size from less than 10 pairs to 100 pairs.

Common Murre and Thick-billed Murre (Uria aalge and U. lomvia)

Like kittiwakes, murres are abundant locally. A pure colony of either species is almost unknown, although one species often makes up more than 90% of a colony. Common murres may have been reduced by foxes, since they tend to use sites with less slope than those used by thick-billed murres. At Bogoslof and the Baby islands, the birds use inland, gently sloping areas because there are no foxes. The presence of the lichen (Caloplaca spp.), which according to Tuck (1960) is indicative of bird roosts, on several extensive cliff areas suggests that either murres or kittiwakes, or both, formerly used areas they do not use now.

Pigeon Guillemot (Cepphus columba)

This species has been noted near almost every island that has been visited. Nesting under beach boulders and driftwood, the birds only occasionally are found in large concentrations (near Great Sitkin more than 4,000 birds were seen in 1971). Murie et al. (1937) summed up the distribution of pigeon guillemot accurately: "Each island has its meager quota of these birds, nesting unobtrusively among the rocks but never assembled in any really large groups." Estimates of populations may be extremely inaccurate because the diurnal rhythm of the pigeon guillemot is unknown.

Marbled Murrelet and Kittlitz's Murrelet (Brachyramphus marmoratus and B. brevirostris)

Nests of neither species have been located in the Aleutians, but nesting of both is suspected at Adak, Unalaska, and Unimak, where specimens of Kittlitz's with brood patches or eggs in the oviduct have been collected in nearshore waters. Courtship has been recorded in marbled murrelets (Byrd et al. 1974).

Ancient Murrelet (Synthliboramphus antiquus)

The distribution of this species is very poorly known, since it is nocturnal near nesting colonies. Murie (1959) wrote, "This is one of the species that undoubtedly has greatly declined in recent years, as a result of increase of the blue-fox industry." The leading of downy young to sea by the adults is a very noisy process and foxes could easily take large numbers. Also, these murrelets nest in fairly shallow burrows which foxes could dig out easily. Birds were recorded near islands in every group during surveys from 1972 to 1975, but workers seldom went ashore to determine if they were nesting. In Fig. 12, the only basis for designating most of the areas marked as colonies is the presence of birds during breeding season (15 May-1 July).

Cassin's Auklet (Ptychoramphus aleuticus)

This is another species that was more common before the fox was introduced. Cassin's auklet now seems to occur only locally, but these nocturnal birds are probably often overlooked. They are known only from Buldir, Umnak, and the vicinity of Oglodak.

Parakeet Auklet (Cyclorrhynchus psittacula)

This auklet, which nests under beach boulders, in burrows, and in rock crevices, seems to use a greater variety of breeding sites than do the other auklets. The largest known colony is at Chagulak, where an estimated 10,000 were seen in 1972. Smaller colonies are found as far west as Buldir.

Crested Auklet, Least Auklet, and Whiskered Auklet (Aethia cristatella, A. pusilla, and A. pygmaea)

Aethia nest primarily in rock crevices of talus slides. Such habitat occurs locally in each major island group except the Near Islands. Least auklets outnumber crested auklets in the Aleutians, and whiskered auklets are far less common than either. Estimates of populations are probably grossly inaccurate because of the difficulty both in estimating the number of birds in the milling flocks observed and in interpreting the estimates after they are obtained.

Horned Puffin and Tufted Puffin (Fratercula corniculata and Lunda cirrhata)

Horned puffins favor rock crevices in talus slides and cliff faces for nesting, whereas tufted puffins are primarily burrow nesters. The historical distribution of the two species was probably based on availability of nesting sites, so tufted puffins were more widespread and numerous. However, in areas where extensive talus slopes are available, horned puffins reached high densities. Predation by introduced foxes may have altered the distribution of tufted puffins, which now nest primarily on fox-free islets just offshore from the larger islands where foxes occur. The distribution of horned puffins may not have been altered significantly, since they are relatively free from fox predation in their rock crevices.

Recommendations

A complete survey of the Aleutian Islands has not been done. This should be done, by methods that will provide accurate population estimates. Life history information is needed on almost all species, and data should be gathered on selected populations to determine trends. Information on winter distribution should also be compiled. The effects of introduced predators should be evaluated quantitatively, and if control measures are needed, effective, humane methods should be devised and implemented.

Acknowledgments

The authors are grateful to the following Fish and Wildlife Service personnel who helped collect previously unpublished data used in this paper: E. P. Bailey, C. S. Craighead, C. P. Dau, M. H. Dick, G. J. Divoky, R. Martin, J. L. Trapp, G. W. Watson, and C. M. White. Most of the data were collected from the deck of the Aleutian Islands National Wildlife Refuge research vessel Aleutian Tern. Captain George Putney is acknowledged for his peerless seamanship and constant encouragement; he also contributed observations of birds.

The maps were adapted from a master supplied by Elaine Rhode, Public Affairs Office, U.S. Fish and Wildlife Service, Anchorage; she also suggested the use of squares to display data. C. M. White graciously made his in-press manuscript available. W. B. Emison, R. J. Gordon, and J. L. Trapp kindly made their field notes available, and Trapp helped compile data. Most of the funds for the surveys in 1971-75 were provided by the U.S. Fish and Wildlife Service.

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