Description
The Zone-tailed Hawk is a fairly large but slender Buteo hawk. Grown birds are 46 to 56 cm (18 to 22 in) in length with a wingspan of about 117–140 cm (46–55 in). The Zone-tailed is comparable in length and wingspan to common large Buteos found to the north such as Swainson's and Red-tailed Hawk, but may weigh considerably less. Their body mass can range from 565–1,080 g (1.25–2.4 lb). In measurements, the sexes are close in size, but the female, at an average of 900 g (2.0 lb), is much heavier and bulkier than the male, at an average of 637 g (1.40 lb). Among standard measurements, the wing chord is 36.5–46 cm (14.4–18 in), the fairly long tail is 19.4–23.5 cm (7.6–9.3 in) and the tarsus is 6.7–7.8 cm (2.6–3.1 in).
The adult plumage is mostly blackish. The notable exception is that the flight feathers are barred with lighter gray, which can appear solid silver-gray from a distance. The tail has three or four bands (the "zones" of the common name), white from below and light gray from above, of which the one second from the tip is particularly broad and conspicuous. The cere and legs are yellow, the lores are light gray and a light touch of white may be seen on the face. Immatures are similar except for small white spots on the breast and tails with narrow gray and black bands and a broad dark tip. The Zone-tailed Hawk adults resemble the Common Black Hawk but are distinctly more slender in flight and overall small, and they have more white bars on the tail. Other Buteo hawks in their dark phase, especially the Broad-winged Hawk, may appear similar but often have more silvery coloration on the wings and are broader-winged.
The call is a loud scream, a somewhat typical Buteo call, dropping in pitch at the end, kra kree-kree-kree-kree. In at least some birds, there is an abrupt rise in pitch (like a break to a falsetto voice) in the middle and an equally abrupt drop back down. They are most often heard vocalizing when engaging in breeding displays at the beginning of the mating season. When disturbed at the nest, they may utter a long, lower-pitched raaaaauu.
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