Circumpolar, north of the tree line, in areas inhabited by lemmings and voles. Nomadic, Following food supply, and will wander regularly in North America as far south in US as line drawn from northern third of Oregon, through northern border of Nebraska, through northern third of Illinois and Indiana, to northern half of New Jersey. In heavy incursion years, vagrants can be found as far south as Florida.
Males are almost pure white, with some birds showing a slight slaty brown flecking.
The larger females are more or less heavily barred with blackish brown, except for pure white face, neck, upper breast, and feet. In summer, on open arctic tundra that is peppered with rocky outcrops in areas usually corresponding to distribution of lemmings and other rodents. In winter, during their southern wanderings, they can be found in prairies, fields, marshes, on beaches, broad river banks, dunes, and even around airports and on golf courses, again depending upon the availability of food. When rodents are scarce, ducks, alcids, and small songbirds are also taken. During winter incursions, they are opportunistic, and will catch any available prey, including the above mentioned species, plus muskrats, grebes, gulls, coots, pheasant, grouse, quail, waders, hawks, smaller owls, and ravens.