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.