Swainson's hawks are medium-sized buteos, smaller than Red-tailed and Ferruginous hawks.
Plumage beneath varies along a continuum from very pale to nearly black below. Lighter-plumaged birds have a distinct chest band. They have relatively long, pointed wings that contribute to superior flying skills. The dark flight feathers contrast with paler wing lining in all but the darkest birds.
It breeds in the bunchgrass prairies east of the Cascades with the highest concentration in the foothills of the Blue and Wallowa mountains. It prefers open country and has little need for numerous trees since it forages extensively while in flight and may include only the nest tree in its home range.