The Ferruginous Hawk is an open-country species that inhabits grasslands, shrubsteppes, and deserts of North America, nesting in 17 states in the United States and 3 provinces in Canada. This hawk avoids montane forests, aspen (Populus) parkland, and habitats recently altered by agricultural cultivation. Before the elimination of bison (Bison bison) in the west, its nests were often partially constructed of bison bones and wool. Today, this hawk uses nesting substrates ranging from cliffs, trees, utility structures, and farm buildings to haystacks and relatively level ground.
The primary prey of the Ferruginous Hawk are rabbits (Lepus spp.), ground squirrels (Spermophilus spp.), and prairie dogs (Cynomys sp.). Populations and the reproduction of this hawk can fluctuate with the availability of these prey. In winter Ferruginous Hawks typically aggregate where ground squirrels and especially prairie dogs are numerous. They are “sit-and-wait” hunters, and groups of 5 to 10 birds will often perch in and around prairie-dog towns.
A. C. Bent's ( Bent 1937b ) description of the Ferruginous Hawk, written almost 60 years ago, captures the essence of this raptor: a “splendid hawk, the largest, most powerful, and grandest of our buteos, a truly regal bird. One who knows it in life cannot help being impressed with its close relationship to the Golden Eagle (Aquila chrysaetos), which is not much more than a glorified buteo. Both species have feathered tarsi, both build huge nests on cliffs and in trees, and both lay eggs that are very similar except in size; food habits, flight, behavior, and voice of the two are much alike.”