Buse de Swainson

Swainson's hawk (Buteo swainsoni) is a large bird species in the Accipitriformes order. This species was named after William Swainson, a British naturalist. It is colloquially known as the grasshopper hawk or locust hawk, as it is very fond of Acrididae (locusts and grasshoppers) and will voraciously eat these insects whenever they are available. Their breeding habitat is prairie and dry grasslands in western North America. They build a stick nest in a tree or shrub or on a cliff edge. This species is a long-distance migrant, wintering in Argentina; it has been recorded as a vagrant in neighboring Chile, in the island countries of the Dominican Republic, and Trinidad and Tobago, and in Norway. This species or its immediate predecessor is the ancestor of the Galápagos hawk, as demonstrated by recent research. Then later diverged from the mainland birds perhaps 300,000 years ago, a very short time in evolution. Swainson's hawk is a raptor and a medium-sized member of the genus Buteo. It broadly overlaps in size with the red-tailed hawk (B. jamaicensis), a related species found as a breeding resident almost throughout North America. Swainson's hawk is on average a little shorter in length, long, and weighs a bit less, . However, Swainson's hawk has a slightly longer wingspan at , with more slender, elongated wings, than the red-tailed hawk. Female Swainson's hawks, at an average weight of , are somewhat larger and heavier than males, at an average of . Among standard measurements, the wing chord is , the tail is , the tarsus is and the bill (from the gape) is . In flight, Swainson's hawk holds its wings in a slight dihedral; it tips back and forth slightly while soaring. There are two main color variations. Over 90% of individuals are light-morph; the dark morph is most common in the far west of the range: Light-morph adults are white on the underparts with a dark, reddish "bib" on the chest and a noticeable white throat and face patch. The underwings, seen as the bird soars, have light linings (leading edge) and dark flight feathers (trailing edge), a pattern unique among North American raptors.