I have been a hawk watcher since my youth in Pennsylvania when I spent fall weekends at Hawk Mountain Sanctuary during the migration of thousands of hawks. Watching a boiling kettle of Broad-winged Hawks circle above always thrilled me. When I came to the west a hawk that I had never seen thrilled me even more when I first saw it, a Ferruginous Hawk. What a cool name I thought and the Latin name, Buteo regalis, reinforced in my mind how grand this raptorial bird is. Described in Birds of the World as the largest Buteo in North America, it sports a wingspan of 4 ½ feet. The upper wing and back feathers are fringed in rufous and the lower belly and underwings are a ferruginous color. Like the Golden Eagle (Aguila chrysaetos), this hawk has feathered legs (tarsi) that are a rusty color.

Ferruginous Hawks occur as a light morph and a dark morph. Light morph birds really show off the rusty feathered legs that contrast with the lighter body color. The tail is whitish at the base with rufous tips. Dark morph birds are often difficult to identify, looking a lot like the dark “Harlan’s” Redtail Hawk.

The white or gray tail and a noticeable white area or “window” in the wing  are good field marks. In flight the wings have a slight uptilt and they will hover at times like a Rough-legged Hawk (Buteo lagopus).

A bird of the North American prairies, grasslands, and sagebrush steppes, its favored food items are prairie dogs, jackrabbits, and ground squirrels. Hunting as a pair, one hawk will patiently stand on the ground next to a prairie dog burrow, waiting for the mammal to emerge and chase it on the ground. The second hawk will finish the hunt with an aerial attack. Historically the Ferruginous Hawk fit into the prairie ecosystem of bison, prairie dogs, black-footed ferrets, and burrowing owls. Early 19th century accounts documented Ferruginous Hawk nests built of bison bones and wool. Today large stick nests are built on cliffs, in trees, and on human made structures such as transmission towers. Modern nests may have supplemental building materials of bleached cow bones lined with large chunks of cow or horse dung. A most interesting behavior! 

Arizona breeding birds are found within the Aubrey Valley and Cliffs Important Bird Area where there is a thriving prairie dog and black-footed ferret population. Ferruginous Hawks breed in central and northern New Mexico, with a high nesting density in the Estancia Valley, a New Mexico Important Bird Area designated for breeding Ferruginous Hawks and wintering raptors. Larger numbers winter in the deserts and grasslands of southern Arizona and New Mexico, often in association with adjacent irrigated agriculture. The Santa Cruz and Lower Gila River valleys in Arizona and the Rio Grande Valley in New Mexico, especially the National Wildlife Refuges and state wildlife areas, are great places to spot this magnificent raptor.  It is this time of year when numbers of birds will be found in one location. I participate in an annual winter raptor count in the desert and farmlands between Phoenix and Tucson. This year my survey team spotted numerous hawks soaring overhead. It was a mixed group of Redtail Hawks and Ferruginous Hawks. Four of the birds were Ferruginous and we could see the wing windows, whitish tail, and the lighter head and chest of the light morph birds hovering. What a show!

Considered a species of least concern globally, Arizona lists the Ferruginous Hawk as a Species of Greatest Conservation Need (AZ). Grasslands restoration and the retention and return of prairie dog populations will benefit this species.