Habitat
Nonbreeding: pelagic, casually along seacoasts and on inland waters (AOU 1983). Nests in open or alpine tundra, flats with sparse vegetation, and moorlands (AOU 1983). Most often in well-drained upland areas, also in dry tundra in low-lying areas; nest usually on mound or hummock (Johnson and Herter 1989). Nests on the ground in a depression, into which it may scrape small amounts of grass, leaves or moss. May nest among rocks.
Ecology
Pairs defend large territories, but often hunt over an area larger than the territory; in northern Sweden, hunted up to 2.7 kilometers from nuest, usually less than 700 meters (Andersson 1971).
Reproduction
Eggs are laid mainly mid- to late June. Both adults, in turn, incubate 2, sometimes 1-3, eggs for 23-25 days. Hatching was recorded in second week of July on Ellesmere Island. Young are tended by both parents, fledge in 22-28 days, attended by adults for 10-21 days after fledging. Second-hatched chick in most broods usually does not survive (Johnson and Herter 1989).