The Ferruginous Hawk—North America’s largest hawk—is often mistaken for an eagle due to its size. The word “ferruginous” derives from the Latin word for iron, referring to the rusty brown of the species’ light color morph. (There is also a less-common dark morph).
ABC’s Dan Casey, our Northern Rockies Conservation Officer, is an admirer. “I have been observing the same pair—one light morph and one dark—nesting on a small prairie hillside north of Cutbank, Montana, for five years or more.”
Along with the Rough-legged Hawk, the Ferruginous is the only American hawk to have legs feathered all the way to the toes, an adaptation that may help preserve heat on the windy, often frigid plains where it makes its home. The feathering may also protect it from the bites of rodent prey.
Although populations of the Ferruginous Hawk are currently stable, Dan says that a new threat is emerging. “One of the highest known densities of Ferruginous Hawks is along the Kevin Rim, just south of the Alberta border in north-central Montana. This is an area threatened by profuse wind turbine development.” Siting of wind turbines is a key concern of ABC’s Bird-Safe Wind Program.
Other threats to the species include habitat loss due to agricultural expansion and pest management programs directed at prey species such as prairie dogs. These programs may reduce the food supply and poison the hawks directly when they eat animals killed by rodenticides.
Along with prairie dogs, rabbits and ground squirrels are important prey for the birds, and they raise larger broods in years when these mammals are abundant. In winter, one place the birds can be found is Mexico’s Chihuahuan desert grasslands, where ABC is working to conserve the endangered Worthen’s Sparrow.