King Vulture

Identification

Excluding the two species of condors, the king vulture is the largest of the New World vultures. Its overall length ranges from 67 to 81 cm (26–32 in) and its wingspan is 1.2 to 2 m (4–7 ft). Its weight ranges from 2.7 to 4.5 kg (6–10 lb). An imposing bird, the adult king vulture has predominantly white plumage, which has a slight rose-yellow tinge to it. In stark contrast, the wing coverts, flight feathers, and tail are dark grey to black, as is the prominent thick neck ruff. The head and neck are devoid of feathers, the skin shades of red and purple on the head, vivid orange on the neck, and yellow on the throat. On the head, the skin is wrinkled and folded, and there is a highly noticeable irregular golden crest attached to the cere above its orange and black bill; this caruncle does not fully form until the bird's fourth year.<p>The king vulture has, relative to its size, the largest skull and braincase, and strongest bill, of the New World vultures. This bill has a hooked tip and a sharp cutting edge. The bird has broad wings and a short, broad, and square tail. The irises of its eyes are white and bordered by bright red sclera. Unlike some New World vultures, the king vulture lacks eyelashes. It also has gray legs and long, thick claws.<p>The vulture is minimally sexually dimorphic, with no difference in plumage and little in size between males and females. The juvenile vulture has a dark bill and eyes, and a downy, gray neck that soon begins to turn the orange of an adult. Younger vultures are a slate gray overall, and, while they look similar to the adult by the third year, they do not completely molt into adult plumage until they are around five or six years of age. Jack Eitniear of the Center for the Study of Tropical Birds in San Antonio, Texas reviewed the plumage of birds in captivity of various ages and found that ventral feathers were the first to begin turning white from two years of age onwards, followed by wing feathers, until the full adult plumage was achieved. The final immature stages being a scattered black feathers in the otherwise white lesser wing coverts.<p>The vulture's head and neck are featherless as an adaptation for hygiene, though there are black bristles on parts of the head; this lack of feathers prevents bacteria from the carrion it eats from ruining its feathers and exposes the skin to the sterilizing effects of the sun.<p>Dark-plumaged immature birds may be confused with turkey vultures, but soar with flat wings, while the pale-plumaged adults could feasibly be confused with the wood stork, although the latter's long neck and legs allow for easy recognition from afar.

Taxonomy

Scientific name

Sarcoramphus papa

Authority

(Linnaeus, 1758)

Order

Cathartiformes

Family

Cathartidae

Genus

Sarcoramphus

Range and habitat

The king vulture inhabits an estimated 14 million square kilometres (5,400,000 sq mi) between southern Mexico and northern Argentina. In South America, it does not live west of the Andes, except in western Ecuador, north-western Colombia and far north-western Venezuela. It primarily inhabits undisturbed tropical lowland forests as well as savannas and grasslands with these forests nearby. It is often seen near swamps or marshy places in the forests. This bird is often the most numerous or only vulture present in primary lowland forests in its range, but in the Amazon rainforest, it is typically outnumbered by the greater yellow-headed vulture, while typically outnumbered by the lesser yellow-headed, turkey, and American black vulture in more open habitats. King vultures generally do not live above 1,500 m (5,000 ft), although are found in places at 2,500 m (8,000 ft) altitude east of the Andes, and have been rarely recorded up to 3,300 m (11,000 ft) They inhabit the emergent forest level, or above the canopy. Pleistocene remains have been recovered from Buenos Aires Province in central Argentina, over 700 km (450 miles) south of its current range, giving rise to speculation on the habitat there at the time which had not been thought to be suitable.

Migration

Resident species

Behavior

The king vulture soars for hours effortlessly, only flapping its wings infrequently. While in flight, its wings are held flat with slightly raised tips, and from a distance the vulture can appear to be headless while in flight. Its wing beats are deep and strong. Birds have been observed engaging in tandem flight on two occasions in Venezuela by naturalist Marsha Schlee, who has proposed it could be a part of courtship behaviour.<p>Despite its size and gaudy coloration, this vulture is quite inconspicuous when it is perched in trees. While perched, it holds its head lowered and thrust forward. It is non-migratory and, unlike the turkey, lesser yellow-headed and American black vulture, it generally lives alone or in small family groups. Groups of up to 12 birds have been observed bathing and drinking in a pool above a waterfall in Belize. One or two birds generally descend to feed on a carcass, although occasionally up to ten or so may gather if there is a significant amount of food. King vultures have lived up to 30 years in captivity, though a male transferred from the Sacramento Zoo to the Queens Zoo is over 47 years old. Vivian, a female King Vulture at Cameron Park Zoo in Waco, TX, turned 70 years old in 2022 and is the oldest known King Vulture in an AZA-accredited facility. Their lifespan in the wild is unknown. This vulture uses urohidrosis, defecating on its legs, to lower its body temperature. Despite its bill and large size, it is relatively unaggressive at a kill. The king vulture lacks a voice box, although it can make low croaking noises and wheezing sounds in courtship, and bill-snapping noises when threatened. Its only natural predators are snakes, which will prey upon the vulture's eggs and young, and large cats such as jaguars, which may surprise and kill an adult vulture at a carcass.<p>The reproductive behaviour of the king vulture in the wild is poorly known, and much knowledge has been gained from observing birds in captivity, particularly at the Paris Menagerie. An adult king vulture sexually matures when it is about four or five years old, with females maturing slightly earlier than males. The birds mainly breed during the dry season. A king vulture mates for life and generally lays a single unmarked white egg in its nest in a hollow in a tree. To ward off potential predators, the vultures keep their nests foul-smelling. Both parents incubate the egg for 52 to 58 days before it hatches. If the egg is lost, it will often be replaced after about six weeks. The parents share incubating and brooding duties until the chick is about a week old, after which they often stand guard rather than brood. The young are semi-altricial—they are helpless when born but are covered in downy feathers (truly altricial birds are born naked), and their eyes are open at birth. Developing quickly, the chicks are fully alert by their second day, able to beg and wriggle around the nest, preen themselves, and peck by their third day. They start growing their second coat of white down by day 10 and stand on their toes by day 20. From one to three months of age, chicks walk around and explore the vicinity of the nest, and take their first flights at about three months of age.<p>The king vulture eats anything from cattle carcasses down to corpses of monkeys and other arboreal mammals to beached fish and dead lizards. In densely forested areas, mammals likelyto be included are many of the abundant sloths (Choloepus/Bradypus) whose combined ranges coincide largely with that of this vulture, but elsewhere it has adapted well to domestic livestock. Principally a carrion eater, there are isolated reports of it killing and eating injured animals, newborn calves, and small lizards. Although it locates food by vision, the role smell has in how it specifically finds carrion has been debated. Consensus has been that it does not detect odours, and instead follows the smaller turkey and greater yellow-headed vultures, which do have a sense of smell, to a carcass, but a 1991 study demonstrated that the king vulture could find carrion in the forest without the aid of other vultures, suggesting that it locates food using an olfactory sense. The king vulture primarily eats carrion found in the forest, though it is known to venture onto nearby savannas in search of food. Once it has found a carcass, the king vulture displaces the other vultures because of its large size and strong bill. However, when it is at the same kill as the larger Andean condor, the king vulture always defers to it. Using its bill to tear, it makes the initial cut in a fresh carcass. This allows the smaller, weaker-beaked vultures, which can not open the hide of a carcass, access to the carcass after the king vulture has fed. The vulture's tongue is rasp-like, which allows it to pull flesh off of the carcass's bones. Generally, it only eats the skin and harder parts of the tissue of its meal. The king vulture has also been recorded eating fallen fruit of the moriche palm when carrion is scarce in Bolívar state, Venezuela.

Conservation

This bird is a species of least concern to the IUCN, with an estimated range of 14 million square kilometres (5,400,000 sq mi) and between 10,000 and 100,000 wild individuals. However, there is evidence that suggests a decline in population, though it is not significant enough to cause it to be listed. This decline is due primarily to habitat destruction and poaching. Although distinctive, its habit of perching in tall trees and flying at high altitudes renders it difficult to monitor.

Population trend

declining