The Ferruginous Hawk is the largest Buteo species in North America, with a wingspan of nearly 1.5 meters. It is an open-country species that inhabits grasslands, shrub-steppes, and deserts of North America, nesting in 17 states within the United States and 3 provinces in Canada. The Ferruginous Hawk uses natural nesting substrates, such as cliffs and trees, and anthropogenic structures, such as oil and gas infrastructure, transmission towers, and even haystacks. If elevated sites are absent, it will also build its nest on relatively level ground. Before the elimination of the American bison (Bison bison), Ferruginous Hawk nests were often partially constructed of the bones and wool of bison.
The primary prey of the Ferruginous Hawk are jackrabbits (Lepus spp.), ground squirrels (Urocitellus spp.), and prairie dogs (Cynomys spp.), and populations and reproduction can fluctuate with the availability of these prey. During winter, the species typically aggregates where ground squirrels and especially prairie dogs are numerous. The Ferruginous Hawk is a “sit-and-wait” hunter, and individuals often perch in and around prairie dog towns.
Named in 1884 by George Robert Gay (1), Arthur Cleveland Bent’s (2) description of the Ferruginous Hawk 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; the food habits, flight, behavior, and voice of the two are much alike.”
In recent decades, Ferruginous Hawk populations have been declining in parts of the species' range. The steepest declines have occurred in Canada, which led to the species being federally listed as Threatened in 2010 (3), but migration and North American Breeding Bird Survey (BBS) counts have also indicated declines in the U.S. (4, 5). Continued loss and fragmentation of North American grassland and shrubland systems by agriculture, energy development, and invasive plant species, underscores the need to understand how land management influences habitat quality and demography of the Ferruginous Hawk. For example, a demographic assessment for Alberta and Saskatchewan related vital-rate parameters, such as nest density and productivity, to variation in habitat characteristics like prey densities (6). Long-term monitoring programs are important for identifying population trends, but local or regional research that associates land management with habitat quality and vital-rate parameters is critical to understand mechanisms responsible for population growth and decline. The rapid growth of wind energy development presents a major area of uncertainty regarding fatalities and displacement from habitat, and will require long-term studies to understand potential impacts.