Ferruginous hawk (Buteo regalis) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

According to chromosome analysis Buteo regalis is most closely related to the Gray Hawk (B. nitidus), Red-tailed Hawk (B. jamaicensis), Rough-legged Hawk (B. lagopus), White-tailed Hawk (B. albicaudatus), Roadside Hawk (B. magnirostris) and Harris’ Hawk (Parabuteo unicinctus) (Schmutz et al. 1993). Despite their geographical separation, the Upland Buzzard (B. hemilasius), which occurs in central Asia, may be the most closely related species to the Ferruginous Hawk (Bechard and Schmutz 1995). Although there are two subpopulations of the Ferruginous Hawk, one on the east side and one on the west side of the Rocky Mountains, no subspecies have been recognized (Bechard and Schmutz 1995).

Morphological description

The Ferruginous Hawk has broad, long wings with rounded tips and a fan-shaped tail, as well as a robust chest, large head and wide gape (Bechard and Schmutz 1995). It ranges from 56-69 cm in length and from 977-2074 g in mass. Although sexes are similar in plumage, females tend to have more pigmentation on their belly and legs. Females are also larger in mass and in maximum grasp between the toes. Two colour phases occur. In the more common pale morph, hawks have brown upper parts (with extensive orange-cinnamon and white markings on the shoulders and back), white underparts with brown streaks and a white to greyish tail. They have a characteristic “V” on their undersides formed by the dark reddish legs when flying. Other distinctive features include the white “window” in the fully extended primaries during flight, the head, which appears much whiter than other hawks from above and rufous shoulders/back.

The less common dark-phased birds have dark brown plumage (some feathers are edged with cinnamon) and a white or grey tail. Considerable variation occurs within each colour morph; adult morphs have variable proportions of dusky brown and ferruginous feathers on the underside and pale morphs have variable amounts of mostly ferruginous and some light neutral grey feathers in a band across the underside of the wings and belly.