Photo © Kim Hosen, Merrimac Farm, Nokesville, Virginia

Black Vulture Coragyps atratus

Description: The American Black Vulture is a very large bird of prey, measuring 65 centimeters (25.5 in) in length, with a 1.5-meter (5 ft) wingspan and a weight of 2-2.75 kilograms (4.5-6 lb). Its plumage is mainly glossy black. The head and neck are featherless and the skin is dark gray and wrinkled. The iris of the eye is brown and has a single incomplete row of eyelashes on the upper lid and two rows on the lower lid.

The legs are grayish white, while the two front toes of the foot are long and have small webs at their bases. The feet are flat, relatively weak, and are poorly adapted to grasping; the talons are also not designed for grasping, as they are relatively blunt.

The nostrils are not divided by a septum, but rather are perforate; from the side one can see through the beak.

The wings are broad but relatively short. The bases of the primary feathers are white, producing a white patch on the underside of the wing's edge, which is visible in flight. The tail is short and square, barely reaching past the edge of the folded wings.

Habitat: Black Vultures are very common in towns and all kinds of settled, partially cleared, and open country.

It is also found in moist lowland forests, shrublands and grasslands, wetlands and swamps, pastures, and heavily degraded former forests. Preferring lowlands, it is rarely seen in mountainous areas.

It is usually seen soaring or perched on fence posts or dead trees. They are mainly absent from extensively forested zones.

Its range includes the southern United States, Mexico, Central America and most of South America. It is usually a permanent resident throughout its range, although birds at the extreme north of its range may migrate short distances, and others across their range may undergo local movements in unfavorable conditions.

In South America, its range stretches to central Chile and Argentina. It also is found on the islands of the Caribbean.

Breeding: The timing of American Black Vultures' breeding season varies with the latitude at which they live. In the United States, birds in Florida begin breeding as early as January, for example, while those in Ohio generally do not start before March.

Pairs are formed following a courtship ritual which is performed on the ground: several males circle a female with their wings partially open as they strut and bob their heads.

They sometimes perform courtship flights, diving or chasing each other over their chosen nest site.

The American Black Vulture lays its eggs on the ground in a wooded area, a hollow log, or some other cavity, seldom more than 3 meters (10 ft) above the ground. While it generally does not use any nesting materials, it may decorate the area around the nest with bits of brightly colored plastic, shards of glass, or metal items such as bottle caps.

Clutch size is generally two eggs, though this can vary from one to three. The smooth, gray-green, bluish, or white shell is variably blotched or spotted with lavender or pale brown around the larger end.

Both parents incubate the eggs, which hatch after 28 to 41 days. Upon hatching, the young are covered with white down. Both parents feed the nestlings, regurgitating food at the nest site.

The young remain in the nest for two months, and after 75 to 80 days they are able to fly skillfully.

Behavior: It soars high while searching for food, holding its wings horizontally when gliding. It flaps in short bursts which are followed by short periods of gliding. Its flight is less efficient than that of other vultures, as the wings are not as long, forming a smaller wing area.

In comparison with the Turkey Vulture, the American Black Vulture flaps its wings more frequently during flight. It is known to regurgitate when approached or disturbed, which assists in predator deterrence and taking flight by decreasing its takeoff weight.

Like all New World Vultures, the American Black Vulture often defecates on its own legs, using the evaporation of the water in the feces and/or urine to cool itself, a process known as urohydrosis.

Because it lacks a syrinx, the American Black Vulture, like other New World Vultures, has very few vocalization capabilities. It is generally silent, but can make soft hisses and grunts.

The American Black Vulture is gregarious, and roosts in large groups. In areas where their ranges overlap, the American Black Vulture will roost on the bare branches of dead trees with groups of Turkey Vultures.

The American Black Vulture generally forages in groups; a flock of Black Vultures can easily drive a Turkey Vulture, which is generally solitary while foraging, from a carcass.

Like the Turkey Vulture, this vulture is often seen standing in a spread-winged stance. The stance is believed to serve multiple functions: drying the wings, warming the body, and baking off bacteria. This same behavior is displayed by other New World vultures, Old World vultures, and storks.

Diet: In natural settings, the American Black Vulture eats mainly carrion. In areas populated by humans, it may scavenge at garbage dumps, but also takes eggs and decomposing plant material and can kill or injure new-born or incapacitated mammals.

Like other vultures, it plays an important role in the ecosystem by disposing of carrion which would otherwise be a breeding ground for disease.

The American Black Vulture locates food either by sight or by following New World Vultures of the genus Cathartes to carcasses. King Vultures and American Black Vultures, which lack the ability to smell carrion, follow them to carcasses.

It is aggressive when feeding, and may chase the slightly larger Turkey Vulture from carcasses. The American Black Vulture also occasionally feeds on livestock or deer.

It is the only species of New World vulture which preys on cattle. It occasionally harasses cows which are giving birth, but primarily preys on new-born calves.

In its first few weeks, a calf will allow vultures to approach it. The vultures swarm the calf in a group, then peck at the calf's eyes, or at the nose or the tongue. The calf then goes into shock and is killed by the vultures.

Interesting Facts: The droppings produced by American Black Vultures and other vultures can harm or kill trees and other vegetation.

The American Black Vulture can be held in captivity, though the Migratory Bird Treaty Act only allows this in the case of animals that are injured or unable to return to the wild.

It receives special legal protections under the Migratory Bird Treaty Act of 1918 in the United States, by the Convention for the Protection of Migratory Birds in Canada, and by the Convention for the Protection of Migratory Birds and Game Mammals in Mexico.

In the United States it is illegal to take, kill, or possess American Black Vultures and violation of the law is punishable by a fine of up to US$15,000 and imprisonment of up to six months.

Written by Sarko Sarkodie

Source(s):
“Turkey Vulture.” Wikipedia: The Free Encyclopedia. 25 May 2009. 29 May 2009. Brown, Bill, Brown, William L., and Hilty, Steven L.
A guide to the birds of Colombia. Edition: illustrated. Published by Princeton University Press, 1986.