Northern Prairie Wildlife Research Center
STATUS: Fairly common in the West, rare in the East.
HABITAT: Inhabits open country, from barren areas to open coniferous forests, primarily in hilly and mountainous regions, but also in rugged deserts, on the plains, and in tundra. Prefers large trees with large horizontal branches and cliffs for roosting and perching. In the West, often moves down from the mountains onto the plains and valleys for winter.
SPECIAL HABITAT REQUIREMENTS: Elevated nest sites, especially cliffs, that are isolated from human disturbance and are close to hunting areas.
NEST: Usually nests on cliff ledges, preferably overlooking grasslands, but also nests in trees or on the ground. In the western mountains, nests at elevations of 4,000 to 10,000 feet above sea level. May use the same nest year after year, or pairs may use alternate nests in successive years.
FOOD: An opportunist; hunts for a variety of prey by soaring over open country or by sighting prey from perch. Feeds primarily on mammals (mainly lagomorphs), but also marmots, prairie dogs, ground squirrels, weasels, woodrats, skunks, and mice, rarely on larger mammals. Also eats grouse, pheasants, owls, hawks, rock doves, magpies, and other birds, as well as rattlesnakes and some carrion.
REFERENCES: DeGraff et al. 1980, Heintzelman 1979, Jollie 1943, McGahan 1968, Snow 1973, Terres 1980.