The bearded vulture is the only known animal whose diet is almost exclusively bone (70-90%). It lives and breeds on crags in high mountains in southern Europe, the Caucasus, Africa, the Indian subcontinent, and Tibet, laying one or two eggs in mid-winter that hatch at the beginning of spring. Populations are resident.
Distribution and Habitat Edit
The bearded vulture is sparsely distributed across a considerable range. It may be found in mountainous regions from Europe through much of Asia and Africa. In Eurasia, it is found in the Pyrenees, the Alps, the Caucasus region, the Zagros Mountains, the Alborzs, the Koh-i-Baba in Bamyan, Afghanistan, the Altai Mountains, the Himalayas, Ladakh in north India, western and central China, Israel (Where although extinct as a breeder since 1981, single young birds have been reported in 2000, 2004 and 2016), and the Arabian Peninsula. In Africa, it is found in the Atlas Mountains, the Ethiopian Highlands and down from Sudan to northeastern Democratic Republic of the Congo, central Kenya and northern Tanzania. An isolated population inhabits the Drakensbergof South Africa.
This species is almost entirely associated with mountains and inselbergs with plentiful cliffs, crags, precipices, canyons and gorges. They are often found near alpine pastures and meadows, montane grassland and heath, steep-sided, rocky wadis, high steppe and are occasional around forests. They seem to prefer desolate, lightly-populated areas where predators who provide many bones, such as wolves and golden eagles, have healthy populations. In Ethiopia, they are now common at refuse tips on the outskirts of small villages and towns. Although they occasionally descend to 300–600 m (980–1,970 ft), bearded vultures are rare below an elevation of 1,000 m (3,300 ft) and normally reside above 2,000 m (6,600 ft) in some parts of their range. They are typically found around or above the tree line which are often near the tops of the mountains, at up to 2,000 m (6,600 ft) in Europe, 4,500 m (14,800 ft) in Africa and 5,000 m (16,000 ft) in central Asia. In southern Armenia they have been found to breed below 1,000 m (3,300 ft) if cliff availability permits. They even have been observed living at altitudes of 7,500 m (24,600 ft) on Mount Everest and been observed flying at a height of 24,000 ft (7,300 m).
This bird is 94–125 cm (37–49 in) long with a wingspan of 2.31–2.83 m (7.6–9.3 ft). It weighs 4.5–7.8 kg (9.9–17.2 lb), with the nominate race averaging 6.21 kg (13.7 lb) and G. b. meridionalis of Africa averaging 5.7 kg (13 lb). In Eurasia, vultures found around the Himalayas tend to be slightly larger than those from other mountain ranges. Females are slightly larger than males. It is essentially unmistakable with other vultures or indeed other birds in flight due to its long, narrow wings, with the wing chord measuring 71.5–91 cm (28.1–35.8 in), and long, wedge-shaped tail, which measures 42.7–52 cm (16.8–20.5 in) in length. The tarsus is relatively small for the bird's size, at 8.8–10 cm (3.5–3.9 in). The proportions of the species have been compared to a falcon, scaled to an enormous size.
Unlike most vultures, the bearded vulture does not have a bald head. This species is relatively small headed, although its neck is powerful and thick. It has a generally elongated, slender shape, sometimes appearing bulkier due to the often hunched back of these birds. The gait on the ground is waddling and the feet are large and powerful. The adult is mostly dark gray, rusty and whitish in color. It is grey-blue to grey-black above. The creamy-coloured forehead contrasts against a black band across the eyes and lores and bristles under the chin, which form a black beard that give the species its English name. Bearded vultures are variably orange or rust of plumage on their head, breast and leg feathers but this is actually cosmetic. This colouration may come from dust-bathing, rubbing mud on its body or from drinking in mineral-rich waters. The tail feathers and wings are gray. The juvenile bird is dark black-brown over most of the body, with a buff-brown breast and takes five years to reach full maturity. The bearded vulture is silent, apart from shrill whistles in their breeding displays and a falcon-like cheek-acheek call made around the nest.
Like other vultures it is a scavenger, feeding mostly on the remains of dead animals. It usually disdains the actual meat, however, and lives on a diet that is typically 85–90% bone marrow. This is the only living bird species that specializes in feeding on marrow. The bearded vulture can swallow whole or bite through brittle bones up to the size of a lamb's femur and its powerful digestive system quickly dissolves even large pieces. The bearded vulture has learned to crack bones too large to be swallowed by carrying them in flight to a height of 50–150 m (160–490 ft) above the ground and then dropping them onto rocks below, which smashes them into smaller pieces and exposes the nutritious marrow. They can fly with bones up to 10 cm (3.9 in) in diameter and weighing over 4 kg (8.8 lb), or nearly equal to their own weight. After dropping the large bones, the bearded vulture spirals or glides down to inspect them and may repeat the act if the bone is not sufficiently cracked This learned skill requires extensive practice by immature birds and takes up to seven years to master. Its old name of ossifrage ("bone breaker") relates to this habit. More seldom, these birds have been observed to try to break bones (usually of a medium size) by hammering them with their bill directly into rocks while perched. During the breeding season they feed mainly on carrion. They prefer limbs of sheep and other small mammals and they carry the food to the nest unlike other vultures which feed their young by regurgitation.
Live prey is sometimes attacked by the bearded vulture, with perhaps greater regularity than any other vulture. Among these, tortoises seem to be especially favored depending on their local abundance. Tortoises preyed on may be nearly as heavy as the preying vulture. When killing tortoise, bearded vultures also fly to some height and drop them to crack open the bulky reptiles' hard shells. Golden eagles have been observed to kill tortoises in the same way. Other live animals, up to nearly their own size, have been observed to be predaciously seized and dropped in flight. Among these are rock hyraxes, hares, marmots and, in one case, a 62 cm (24 in) long monitor lizard. Larger animals have been known to be attacked by bearded vultures, including ibex, Capra goats, Chamois and Steenbok. These animals have been killed by being surprised by the large birds and battered with wings until they fall off precipitous rocky edges to their deaths; although in some cases these may be accidental killings when both the vulture and the mammal surprise each other. Many large animals killed by bearded vultures are unsteady young, or have appeared sickly or obviously injured. Humans have been anecdotally reported to have been killed in the same way. However, this is unconfirmed and, if it does happen, most biologists who have studied the birds generally agreed it would be accidental on the part of the vulture. Occasionally smaller ground-dwelling birds, such as partridges and pigeons, have been reported eaten, possibly either as fresh carrion (which is usually ignored by these birds) or killed with beating wings by the vulture. While foraging for bones or live prey while in flight, bearded vultures fly fairly low over the rocky ground, staying around 2 to 4 m (6.6 to 13.1 ft) high. Occasionally, breeding pairs may forage and hunt together. In the Ethiopian Highlands, bearded vultures have adapted to living largely off human refuse.
The acid concentration of the bearded vulture stomach has been estimated to be of pH about 1 and large bones will be digested in about 24 hours, aided by slow mixing/churning of the stomach content. The high fat content of bone marrow makes the net energy value of bone almost as good as that of muscle, even if bone is less completely digested. A skeleton left on a mountain will dehydrate and become protected from bacterial degradation and the bearded vulture can return to consume the remainder of a carcass even months after the soft parts have been consumed by other animals, larvae and bacteria.