Buse rouilleuse

The ferruginous hawk, (Buteo regalis), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (B. lagopus). The generic name buteo is Latin for 'buzzard'. The specific epithet regalis is Latin for 'royal' (from rex, regis, 'king').. The common name 'ferruginous' means 'rust-colored' or 'reddish-brown'. This species is a large, broad-winged hawk of the open, arid grasslands, prairie and shrub steppe country; it is endemic to the interior parts of North America. It is used as a falconry bird in its native ranges. This is the largest of the North American Buteos and is often mistaken for an eagle due to its size, proportions, and behavior. Among all the nearly thirty species of Buteo in the world, only the upland buzzard (B. hemilasius) of Asia averages larger in length and wingspan. The weight of the upland buzzard and ferruginous broadly overlaps and which of these two species is the heaviest in the genus is debatable. As with all birds of prey, the female ferruginous hawk is larger than the male, but there is some overlap between small females and large males in the range of measurements. Length in this species ranges from with an average of , wingspan from , with an average of about , and weight from . Weight varies in the species relatively restricted breeding range. In the southern reaches of the species breeding range, i.e. Arizona, New Mexico and Utah, males average , in a sample of fifteen, and females average , in a sample of four. In the northern stretches of the breeding range, in southern Canada, Washington, Idaho and North Dakota, the hawks are heavier averaging in males (from a sample of 30) and in females (from a sample of 37). Upland buzzard average weights were intermediate between those body mass surveys, notably heavier than the first and less heavier than the latter one, particularly the sample of 37 ferruginous hawk females place it as the most massive type of Buteo in northern populations.