Waterbird Migration Near the Yukon and Alaskan Coast of the Beaufort Sea: I. Timing, Routes and Numbers in Spring

Аннотация

Radars, systematic visual observations from the coast, and aerial surveys were used to study migration near the Yukon (1975) and Alaskan (1977-78) coasts of the Beaufort Sea. Conspicuous eastward migration of loons, brant, seaducks, jaegers and glaucous gulls occurs along the icebound coast, and in the Yukon some eastbound species (especially brant) concentrate coastally. Overall, however, eastward migration is predominantly broad-front with little coastal concentration. Most eiders and perhaps most oldsquaws, the commonest waterbirds, fly east offshore where there is more open water. Westward migration is much less conspicuous visually; swans, geese and pintails are the main groups seen. However, radar shows extensive broad-front westward flights, probably largely of shorebirds. Most spring migration, both east and west, is from 15 May to 20 June, with the coastal peak (25 May-15 June) apparently being later than that offshore. Some coastal migrants land on river water that overflows onto nearshore ice in early June. Some waterbirds bypass the largely ice-covered Alaskan Beaufort by flying northeast across interior Alaska and/or northwestern Canada from the Pacific ocean to the Canadian Arctic. These overland migrants include some yellow-billed and arctic loons, brant and jaegers; probably most Thayer's gulls; and probably some oldsquaws, Sabine's gulls, arctic terns and other species.

Key words: waterbirds, migration, Beaufort Sea, Alaska, Yukon, radar, aerial surveys, seawatches, leads, leading lines