Tuesday, November 29, 2016

Swainson's Hawk

All photos copyright Ned Harris

Adult Swainson's Hawk

The Swainson’s Hawk initially suffered from a case of mistaken identity, when a specimen collected in Canada in 1827 and illustrated by William Swainson was confused with the common buzzard (Buteo buteo) of Europe. A nephew of Emperor Napoleon eventually corrected the error: in 1832, while working in Philadelphia, French biologist Charles Lucien Bonaparte identified the hawk as a new species and named it after the original illustrator—although he based his own description on a drawing by John James Audubon.

Juvenile Swainson's Hawk

A classic species of the open country of the Great Plains and the West, Swainson’s Hawks soar on narrow wings or perch on fence posts and irrigation spouts. These elegant gray, white, and brown hawks hunt rodents in flight, wings held in a shallow V, or even run after insects on the ground. In fall, they take off for Argentine wintering grounds—one of the longest migrations of any American raptor—forming flocks of hundreds or thousands as they travel.

Adult Male

Adult Female

Though they can be quite variable, most Swainson’s Hawks are light-bellied birds with a dark or reddish-brown chest and brown or gray upperparts. They have distinctive underwings with white wing linings that contrast strongly with blackish flight feathers. Most males have gray heads; females tend to have brown heads. Dark individuals also occur; these vary from reddish to nearly all black, with reduced contrast on the underwings.

Tomorrow's hawk: Ferruginous

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