Egyptian Vulture - Behaviour and Ecology

Behaviour and Ecology

The Egypian Vulture is usually seen singly or in pairs, soaring in thermals along with other scavengers and birds of prey, or perched on the ground or atop a building. On the ground, they walk with a waddling gait. They feed on a range of food, including mammal faeces (including those of humans), insects in dung, carrion, vegetable matter, and sometimes small animals. When it joins other vulture species at a dead animal, it tends to stay on the periphery and waits until the larger species to leave. Wild rabbits (Oryctolagus cuniculus) form a significant part of the diet of Spanish vultures. Studies suggest that they feed on ungulate faeces to obtain carotenoid pigments responsible for their bright yellow and orange facial skin. The ability to assimilate carotenoid pigments may serve as a reliable signal of fitness.

Egyptian Vultures are mostly silent but make high-pitched mewing or hissing notes at the nest and screeching noises when squabbling at a carcass. Young birds have been heard making a hissing croak in flight. They also hiss or growl when threatened or angry.

Egyptian Vultures roost communally on large trees, buildings or on cliffs. Roost sites are usually chosen close to a dump site or other suitable foraging area. In Spain, summer roosts are formed mainly by immature birds. The favourite roost trees tended to be large dead pines. The number of adults at the roost increases towards June. It is thought that breeding adults may be able to forage more efficiently by joining the roost and following others to the best feeding areas. Breeding birds that failed to raise young may also join the non-breeding birds at the roost during June.

The breeding season is in spring. During the beginning of the breeding season, courting pairs soar high together and one or both may make steep spiralling or swooping dives. The birds are monogamous and pair bonds may be maintained for more than one breeding season and the same nest sites may be reused each year. The nest is an untidy platform of twigs lined with rags and placed on a cliff ledge, building, or the fork of a large tree. Old nest platforms of eagles may also be taken over. Nests placed on the ground are rare but have been recorded in subspecies N. p. ginginianus and N. p. majorensis. Extra-pair copulation with neighbouring birds has been recorded and may be a reason for adult males to stay close to the female before and during the egg laying period. Females may sometimes associate with two males and all three help in raising the brood. The typical clutch consists of two eggs which are incubated in turns by both parents. The eggs are brick red with the broad end covered more densely with blotches of red, brown, and black. The parents begin incubating soon after the first egg is laid leading to asynchronous hatching. The first egg hatches after about 42 days. The second chick may hatch three to five days later and a longer delay increases the likelihood that it will die of starvation. In cliffs where the nests are located close to each other, young birds have been known to clamber over to neighbouring nests to obtain food. In the Spanish population, young fledge and leave the nest after 90 to 110 days. Fledged birds continue to remain dependent on their parents for at least a month. Once the birds begin to forage on their own, they move away from their parents' territory; young birds have been found nearly 500 km away from their nest site. One year old European birds migrate to Africa and stay there for at least one year. A vulture that fledged in France stayed in Africa for three years before migrating north in spring. After migrating back to their breeding areas, young birds move widely in search of good feeding territories and mates. The full adult plumage is attained in the fourth or fifth year. Egyptian Vultures have been known to live for up to 37 years in captivity and at least 21 years in the wild. The probability of survival in the wild varies with age, increasing till the age of 2 and then falling at the age of 5. Older birds have an annual survival probability varying from 0.75 for non-breeders to 0.83 for breeding birds.

Healthy adults do not have many predators, but human activities pose many threats. Collisions with power lines, hunting, intentional poisoning, lead accumulation from ingesting gunshot in carcasses, and pesticide accumulation take a toll on populations. Young birds at the nest are sometimes taken by Golden Eagles, eagle owls, and red foxes. Only rarely do adult birds attempt to drive away predators. Young birds that fall off of cliff ledges may be preyed on by mammalian predators such as jackals, foxes and wolves.

The nominate population, especially in Africa, is known for its use of stones as tools. When a large egg, such as that of an ostrich or bustard, is located, the bird walks up to it with a large pebble held in its bill and tosses the pebble by swinging the neck down over the egg. The operation is repeated until the egg cracks from the blows. They prefer using rounded pebbles to jagged rocks. This behaviour, first reported by Jane Goodall in 1966, has however not been recorded in N. p. ginginianus. Tests with both hand-reared and wild birds suggests that the behaviour is innate, not learnt by observing other birds, and displayed once they associate eggs with food and have access to pebbles. Another case of tool-use described from Bulgaria involves the use of a twig as a tool to roll up and gather strands of wool to use for lining the nest.