Short-tailed Hawk - Description

Description

The Short-tailed Hawk is a small buzzard. Males average smaller than the females, but the size difference is slighter than in most birds of prey and the sexes are indistinguishable in the field. Length can range from 37 to 45 cm (15 to 18 in), wingspan from 80–103 cm (31–41 in) and body mass from 342 to 625 g (12.1 to 22.0 oz). Among standard linear measurements, the wing chord is 26.5–34 cm (10.4–13 in), the tail is 13–18 cm (5.1–7.1 in) and the tarsus is 5.5–6.2 cm (2.2–2.4 in). It has broad rounded wings, the tips of which are curved upwards while soaring, and a broad tail that despite the bird's name is of average length for a buteo in proportion to the body. Its call is a high-pitched scream similar to other buzzards.

One of the most interesting things about this bird is the melanistic "black" phase – this species occurs in two colour morphs, with no intermediates. The dark form predominates in Florida, where it is known as "little black hawk". The light form is common elsewhere in the species' range. In most of the North American buteos – e.g. the Red-tailed Hawk (B. jamaicensis) and Swainson's Hawk (B. swainsoni) – melanistic individuals are known, although wholly black plumage is comparatively rare. Only in the North American population of Buteo brachyurus does it seem to be the prevalent form.

The adult light morph has dark brown upperparts. The underparts are white, except that the tail and flight feathers are grey barred with dark. The immature is similar to the adult but the face is streaked rather than white, and the tail bands are of equal width, whereas the adult has a broad bar near the tail tip. The light morph is considered unmistakable when seen well in flight, due its blackish back and hood in contrast to an otherwise largely white underside.

The adult dark morph has black-brown upperparts and underparts, apart from the tail and flight feathers, which are grey barred with dark as in the light morph but possibly with darker grey. The young bird has the same tail pattern as the light-morph immature, and the underparts are spotted with white. Differentiating the dark morph from other dark morph Buteos is difficult, especially from the closely related Broad-winged Hawk.

For a long time, it was thought that the dark phase of the present bird was a distinct species Buteo fuliginosus. For example, when Robert Ridgway discussed the Short-tailed Hawk collected at Oyster Bay, Lee County, Florida by W. S. Crawford on January 28, 1881, the question whether or not the black birds were of the same species as the light ones was not yet settled.