Feeding Behavior

May hunt by day or night. In summer, daytime feeding is usually near dawn or dusk. Usually hunts by listening and watching from a perch, swooping down when it locates prey; sometimes hunts by flying low over open areas. Can locate prey by sound, and will plunge into snow to catch rodents more than a foot below the surface.

Eggs

2-5. White. At times, may lay more eggs in years when food is abundant. Incubation is by female only, 28-36 days. Male brings food to incubating female on nest. Young: Female broods young for first 2-3 weeks. Male brings food to nest, and female feeds it to young. Young may climb out of nest and perch in nest tree or nearby trees after 3-4 weeks, are able to fly 1-2 weeks later. In some areas, adult female departs after young fledge, while male remains with them and feeds them for up to 3 months.

Young

Female broods young for first 2-3 weeks. Male brings food to nest, and female feeds it to young. Young may climb out of nest and perch in nest tree or nearby trees after 3-4 weeks, are able to fly 1-2 weeks later. In some areas, adult female departs after young fledge, while male remains with them and feeds them for up to 3 months.

Diet

Mostly small mammals. Feeds mainly on voles in many northern areas; in western United States, pocket gophers may be main prey. Also eats mice, shrews, squirrels, weasels, small birds, rarely frogs.

Nesting

In courtship, male may feed female; members of pair preen each others' feathers. Nest: Usually uses old abandoned nest of other large bird, such as goshawk, raven, Osprey; sometimes nests on top of broken-off snag or stump, rarely on the ground. Site usually 10-50' above ground. A pair may reuse the same nest for several years.