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Buteo swainsoni This species was named after William Swainson, a British naturalist.
This is one of the most colorful members of the hawk family. The head, eyes and underparts are dark brown. A wide chestnut-colored band across the chest contrasts with a white throat and pale belly. The light undersides of the wings contrast with the dark rear half of the flight feathers. A dark morph variety is dark brown except for a light patch under the tail, and a rufous variant is lighter on the underparts with reddish bars. Young of all three varieties are similar to adults but with pale mottling on dark areas and dark mottling on light areas.
An adult Swainson's hawk stands about 18 inches high, has a wingspan of up to 48 inches, and weighs about 3 pounds.
Distribution and Habitat
Swainson's hawks prefer open prairies and dry grasslands. They breed throughout much of western North America, and winter in Argentina.
This species has the longest migration of any North American hawk, with flocks from the northern reaches of the breeding range traveling about 14,000 miles one-way to their wintering grounds. Large flocks begin moving south in August, and begin their return flights in late February.
Unlike most other birds of prey, Swainson's hawks feed primarily on insects, with crickets and grasshoppers being the preferred food. Insects are caught both in flight and on the ground, and the Swainson's hawk is always ready to take advantage of feeding opportunities brought about by farming operations and fire. During the breeding season the diet is supplemented with mice and other small mammals, as well as birds and reptiles.
Most breeding takes place in March and April. Breeding pairs appear to be monogamous for at least one season, with at least some staying together through multiple seasons.
Nest building is typically done by the male. The nest itself is a large mass of twigs and grasses constructed in a tree or on a ledge, sometimes on the ground. It is not uncommon for a breeding pair to return to a nest used in a previous season, with necessary repairs being done by the male. Two to four white eggs, each about 2.25 inches long and 1.8 inches wide and sometimes marked with brown, are laid per clutch. They are incubated solely by the female for 28 to 36 days, with the male bringing food to the female.
Chicks are nearly helpless at hatching. They are fed small, young mammals while growing, and can fly on their own in about four weeks.
Swainson's hawks are not considered a threatened species, except in a few parts of its traditional range where habitat loss and pesticide use have taken their toll.
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This page was last updated on September 25, 2017.