White-tailed Hawk, Buteo albicaudatus
White-tailed Hawks are found in tropical or subtropical environments across the Americas. This bird is a large bird of prey species. It is close to the size of the related Swainson’s and Red-tailed Hawks. The average measurements of this bird fall a little bit ahead of the first and a little bit behind the latter. It can be up to 17 to 24 inches in length, and its wingspan can be up to 46 to 56 inches. A body mass of 1.9 to 2.7 pounds was recorded in B. a. hysopodius and 1.91 to 2.2 pounds in B. a. colonus. Amongst standard measurements, the wing chord is 15 to 18.2 inches, the tail is 7.6 to 8.7 inches and the tarsus is 3.1 to 3.6 inches. Mature birds are grey above and white below on the rump, with faint pale grey or brownish barring. It has a short tail that is white with a skinny black band near the end that is obvious when it is in flight. A rusty-red shoulder patch is just as characteristic when the bird is sitting with its wings closed. The wings are dark above, admixed with grey coloring near the bases of the blackish primary remiges (located on the posterior side of the wing). The underwing is whitish, with indistinguishable brownish barring on the underwing coverts that reaches out onto the flanks and thighs. The iris is hazel, the cere (a waxy structure covering the base of their bill) is pale green, the beak is black with horn coloring at the base, and the feet are yellow with black talons.
Immature birds are a little darker than the adult birds; they might appear almost black in faint light, in particular individuals which have barely any white below. The lining on the wing has obvious black and white spots. Immature birds do not have the rusty-red shoulder patch that the adults have. The tail changes from brown with dark bars to grayish with a hazy dark band as the birds get closer to being mature. Their calls are a high pitched cackling ke ke ke, with a twinkling quality that reminds some people of the bleating of a goat or the call of the Laughing Gull. The White-tailed Hawk is difficult to confuse with any other birds, except that in the Southern Hemisphere winter, the younger birds are sometimes mistaken for the migrant Red-backed Hawks.
There are only three subspecies that are known. One is the Buteo albicaudatus hypospodius; it lives in coastal Texas and the Rio Grande Valley through Middle America to northern Columbia and western Venezuela. It’s intermediate in size and coloration and there are no dark morphs. The second being Buteo albicaudatus colonus, and it lives in eastern Columbia to Surinam south to the mouth of the Amazon River, stretching into the Caribbean. It is small and pale. The dark morphs are ashy grey all over, except for the tail and underwing coverts; they are sometimes widely marked rufous on the underside. Immature dark morphs are sometimes black all over, except for their tail. And finally, the Buteo albicaudatus albicaudatus, which lives in the southern Amazon Rainforest to central Argentina. It is large and dark colored; the throat is usually black (except in western Argentina). The dark morph seems to be blackish above, and blackish brown below.
This White-tailed Hawk can be found anywhere from Coastal Texas and the Rio Grande Valley to central Argentina as well as many of the Caribbean Islands, however, its mostly the southern ones. The preferential habitat consists of semi-open regions up to 2,000 feet above sea level, with few trees to hinder its flight. It’s not a migratory bird, though some populations may make some regional movements when the food source is scarce. These birds like to perch on bushes, trees, telephone poles or even stand around the ground, as well as to soar. In general, though, it prefers arid habitat and rarely spends time in very rainy settings. Though it will disappear from unacceptable locations after habitat fragmentation, it has a broad range and isn’t considered to be a globally threatened species by the IUCN.
Its preferred hunting technique is to hover and watch the surroundings for signs of potential prey, gliding to another place when they cannot find anything. Their diet varies with their environment, but rabbits make up the majority of it in southern Texas. Lizards around 12 inches in length or more are the preferred prey in the Dutch West Indies. Other animals such as cotton rats, snakes, frogs, arthropods, and smallish birds like passerines or quails are also eaten; it will steal chickens when no other food source is available. In the open cerrado of Brazil, mixed-species feeding flocks of birds will react to a White-tailed Hawk with nearly as much of alarm as they do when seeing such dedicated predators of birds such as the Aplomado Falcon. The Hawk is also known to eat carrion and to gather with other birds at brushfires to catch small animals that are fleeing from the flames. In the tropics, the Hawks rank amongst the main predators of small monkeys known as marmosets.
Breeding couples of these birds build nests made out of freshly broken twigs, most often of thorny plants 1.5 to 5 meters above the ground on top of a tree or yucca, preferably one growing in a high location giving good visibility from the nest. The inside of the nest is cushioned with dried grasses and other find materials; green mesquite twigs or other aromatic plants are often put in the nest too, maybe to put off parasites. Like many Accipitridae, the White-tailed Hawks dislike abandoning a nest site, and nests built up over the years can thus reach sizes of up to three feet across. Their eggs are white, sometimes lightly spotted with lavender or brown; between one and three (usually two) are laid per clutch. When approached on the nest, the adults will get airborne and watch the intruder from above, unlike related hawks, which usually wait much longer to flush and then begin an unwavering attack.
Image Caption: White-tailed Hawk. Credit: Rick elis.simpson/Wikipedia (CC BY-SA 3.0)