The ferruginous hawk (ferruginous = from Latin ferrum – iron, ferrgin-, iron rust, iron-rust color – reddish-brown), Buteo regalis (Latin, royal hawk), 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).

Source: Wikipedia