The magnificent Ferruginous Hawk Buteo regalis is North America’s largest “hawk” - with a wingspan averaging around 56″/142.24cm - and during both summer and winter is found in grasslands, deserts, and other open areas with isolated shrubs or trees where less than 50% of the land is under cultivation (during winter, Ferruginous Hawks are often found around colonies of prairie dogs Cynomys sp which make up much of their winter diet). The species occurs in two colour-phases: the pale form - which the three birds below belong to - is by far the most numerous.

The Ferruginous Hawk is a long-distance migrant, many birds breeding in the prairie regions of the US flying to Mexico for the winter. To quote from the informative Ferruginous Hawk.org website: “Much remains to be learned about Ferruginous Hawk migration ecology throughout the extremes of this species range. A coordinated, international study is needed to provide an understanding of how regional ferruginous hawk populations interact throughout the year, and to better understand nesting and winter philopatry of regional populations…The species is currently listed as endangered or threatened in several states, as Vulnerable in Canada, and is protected by the Migratory Bird Treaty Act (Bechard and Schmutz 1995). Identification of winter and breeding destinations from satellite telemetry will provide information on potential man-caused threats that may limit populations, and hawk survival.”

These photos were taken at the Carrizo Plain National Monument, California, on March 2nd 2008.

Adult:
Adults are rusty brown on the upper parts and strikingly pale on the head, neck and underparts with rust on the legs (which are feathered, like the Rough-legged Hawk Buteo lagopus but unlike its close congener the Red-tailed Hawk B. jamaicensis) and some underwing banding formed by rusty tips to many of the underwing coverts. Note the very restricted black tips to the primaries, a useful identification feature on distant birds.

Adult pale form Red-tailed Hawk photographed on the same day: superficially similar but note the dark head,
extensive dark tips to the primaries, the dark bar along the trailing edge of the wing, and the dark patagial bar (the thick dark bar going out from the body across the inner third of the leading/front edge of the wings).

Juvenile:
Juveniles are generally quite similar to adults, but the juvenile light form lacks the rufous legs, back, and underwing covert markings of the adult, and has a lightly banded tail. Note in the images below (which are all of the same bird) the two whitish, adult-type feathers in the centre of the tail with which the bird has already replaced the existing juvenile feathers.

The upperparts of Ferruginous Hawks are wonderful for seeing how feathers arrange themselves in flight: in this photo the almost translucent primaries (which form the pale “window” guide-books refer to) are clearly separable from the darker secondaries, and the pale-centred primary coverts are clearly separable from the darker secondary coverts.

All photos copyright Charlie Moores