Monday, February 20, 2012

>Buteo albicaudatus (White-tailed Hawk)

White-tailed Hawk

White-tailed Hawk
Adult at Salvador Zoo, Ondina, Salvador, Bahia, Brazil
Conservation status
Scientific classification
(or Accipitriformes, q.v.)
Species:B. albicaudatus
Binomial name
Buteo albicaudatus
Vieillot, 1816
The White-tailed Hawk (Buteo albicaudatus) is a large bird of prey species found in tropical orsubtropical environments across the Americas.


Averaging 21–23 in (53–58 cm) in length with a wing span of around 4 ft (1.2 m),the super White-tailed Hawk is a large, stocky buteo hawk. Adult birds are grey above and white below and on the rump, with faint pale grey or rufous barring. The short tail is white with a narrow black band near the end that is conspicuous in flight. A rusty-red shoulder patch is just as characteristic when the bird is sitting with wings closed. The wings are dark above, admixed with grey near the bases of the blackish primary remiges. The underwing is whitish, with indistinct brownish barring on the underwing coverts that extends onto the flanks and thighs. The iris is hazel, the cere is pale green, the beak is black with a horn-colored base, and the feet are yellow with black talons.
Immature birds are somewhat darker than adults; they may appear nearly black in faint light, in particular individuals which have little white below. The wing lining is conspicuously spotted black-and-white; the rusty shoulder patch is absent in younger birds. The tail changes from brown with several dark bars to greyish with a hazy dark band as the birds approach maturity. The bare parts are colored much like in the adult.
Its call is a high-pitched cackling ke ke ke..., with a tinkling quality that reminds some of the bleating of a goat or the call of the Laughing Gull.
The White-tailed Hawk is hard to confuse with any other bird, except that in the Southern Hemisphere winter, young birds are sometimes mistaken for migrant Red-backed Hawks.


Three subspecies are known:
Intermediate in size and coloration. No dark morph.
Small and pale. Dark morph is ashy grey all over, except for the tail and underwing coverts; sometimes extensively marked rufous on the underside. Dark-morph immatures are sometimes black all over, except for the tail.
Large and dark; throat usually black (except in western Argentina). The dark morph appears blackish above, blackish-brown below.

Distribution and ecology

Adult B. a. hypospodius at Laguna Atascosa National Wildlife Refuge, Texas, USA
The White-tailed Hawk can be found anywhere fromcoastal Texas and the Rio Grande Valley to central Argentina as well as many Caribbean islands, although mostly the southern ones. For habitat it prefers open or semi-open regions up to 2,000 ft (c. 600 m) ASL, with few trees to hinder its flight. It is not a migratory bird, though some populations may make regional movements when food is scarce. It likes to perch on bushes, trees, telephone poles or even stand around on the ground, as well as to soar. Generally, it prefers aridhabitat and rarely occurs in very rainy locales.
Though it will disappear from unsuitable locations after habitat fragmentation, it has a wide range and is not considered to be a globally threatened species by the IUCN.
Its preferred hunting technique is to hover and observe the surroundings for signs of potential prey, gliding to another place when nothing is found. The diet of the White-tailed Hawk varies with its environment. Rabbits make up the majority of the hawk's diet in southern Texas, while lizardsof 12 in (30 cm) in length and more are the preferred prey in the Dutch West Indies. Other animals such as cotton ratssnakesfrogs,arthropods (especially grasshopperscicadas and beetles), and smallish birds such as passerines or quails are also eaten; it will snatchchickens when no other source of food is available. In the open cerrado of Brazilmixed-species feeding flocks will react to a White-tailed Hawk with almost as much alarm as they do when seeing such dedicated predators of birds as the Aplomado Falcon.The White-tailed Hawk is also known to feed on carrion and to gather with other birds at brushfires to catch small animals fleeing the flames.
Breeding pairs of White-tailed Hawks build nests out of freshly broken twigs, often of thorny plants, 5–15 ft (1.5–5 m) or more above the ground on top of a tree or yucca, preferably one growing in an elevated location giving good visibility from the nest. The nest's interior is cushioned it with dried grasses and other fine materials; green twigs of mesquite or other aromatic plants are often placed in the nest too, perhaps to deter parasites. Like many Accipitridae, White-tailed Hawks do not like to abandon a nest site, and nests built up over the years can thus reach sizes of up to three feet (1 m) across. The eggs are white, often lightly spotted with brown or lavender; between one and three (usually two) are laid per clutch. When approached on the nest, the adults will get airborne and observe the intruder from above, unlike related hawks, which usually wait much longer to flush and then launch a determined attack.

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