Habitat

Breeding Range

Major habitat type is arctic and alpine tundra, often along rivers and seacoasts. Climate: polar continental, temperature -30°C to +10°C, annual precipitation 110–260 mm, snow covered 8–9 mo/yr, icebound 9–10 mo/yr. Vegetation: low arctic tundra; dominant species wide-ranging, including sedge (Carex sp.), birch (Betula sp.), willow (Salix sp.), cottongrass (Eriophorum sp.), lichens, and mosses (Cade 1960, Salter et al. 1980, Norment 1985, Poole and Bromley 1988b, Obst 1994). Occasionally in tundra-boreal forest ecotone; small discontinuous stands of spruce (Picea sp.) along drainages, beach strands, and dunes (MacFarlane 1891, Norment 1985, Obst 1994, Brodeur et al. 1995).

Rocky seacoasts, offshore islands, and barrenlands with rocky outcrops near coast, sea level to 500 m, including Greenland, Canadian Arctic Islands, Labrador Coast, Ungava Bay, Hudson Bay, and Bering Sea; particularly near colonial-nesting seabirds or waterfowl. Topography: sedimentary cliffs with volcanic intrusions and sills, basalts, rising above water and rolling or flat terrain (Cade 1960, Poole and Bromley 1988b).

Rivers and some lakes draining through mountains and foothills in tundra or at edge of taiga, sea level to 1,050 m, including Koksoak and George Rivers in Ungava; Horton and Anderson Rivers in Northwest Territories; Firth River in Yukon; Colville, Utokuk, Kukpuk, and Sagavanirktok Rivers in Alaska; and Thelon River and lakes in Mackenzie district (Northwest Territories) (MacFarlane 1891, Cade 1960, White and Cade 1971, Roseneau 1972, Kuyt 1980, Obst 1994, Norment et al. 1999, Ritchie et al. 2003). Topography: river and lake bluffs of unconsolidated marine and nonmarine sediments; sand, silt, clay shale, and glacial till (White and Cade 1971, Norment 1985).

Mountainous terrain above timberline, up to 1,630 m, including Brooks and Alaska Ranges in Alaska (Cade 1960, Swem et al. 1994); British and Richardson Mtns. in Yukon (Platt 1976, Mossop and Hayes 1994); Richardson and Mackenzie Mtns. in Northwest Territories (Shank and Poole 1994); and Atlin region of British Columbia. Topography: escarpments and rocky crags of both sedimentary and volcanic origin (White and Cade 1971, Barichello 1983).

Spring And Fall Migration

Little information; migration and wintering habitat probably similar (see Salter et al. 1980, Johnson and Herter 1989, Sanchez 1993). Juvenile birds radio-tagged in Alaska used coastal and riparian habitats during fall, with multiple birds using the south coast of the Yukon-Kuskokwim Delta (Britten et al. 1995, TLB unpub. data). This area has wide expanses of tidal mud flats and coastal wetlands supporting large numbers of shorebirds, waterfowl, and gulls in the fall (Ernst 1989, B. McCaffery, pers. comm.).

Winter Range

Higher latitudes and elevations probably vacated (unless ptarmigan available, e.g., Denali Park, AK). Often frequent polynyas (open pockets of water) where seabirds congregate in otherwise frozen Bering Sea (Everett et al. 1989) and between Greenland and Canadian Arctic Islands (K. Burnham, unpub. satellite telemetry data). Winter range otherwise similar to breeding habitat for resident birds (Platt 1976, Cade 1982, Nielsen and Cade 1990b).

In north temperate region of the U.S. and Canada, open areas below 1,000 m, particularly in areas where prey (birds) are concentrated, including seacoasts, reservoirs, agricultural areas, grasslands, and shrublands. Topography generally flat or rolling. Substrate and vegetation vary widely with geographic region, including intermountain desert, prairie, river valleys, and human-modified habitats (Wiseley and Pinel 1987, Dobler 1989, Garber et al. 1993, Sanchez 1993).