Bearded vulture
The bearded vulture, also known as the lammergeier and ossifrage, is a very large bird of prey in the monotypic genus Gypaetus. The bearded vulture is the only known vertebrate whose diet consists of 70–90% bone.
Traditionally considered an Old World vulture, it actually forms a separate minor lineage of Accipitridae together with the Egyptian vulture, its closest living relative. It is not much more closely related to the Old World vultures proper than to, for example, hawks, and differs from the former by its feathered neck. Although dissimilar, the Egyptian and bearded vulture each have a lozenge-shaped tail—unusual among birds of prey. It is vernacularly known as Homa, a bird in Iranian mythology.
The bearded vulture population is thought to be in decline; in 2004, it was classified on the IUCN Red List as least concern but has been listed as near threatened since 2014. It lives and breeds on crags in high mountains in Iran, southern Europe, East Africa, the Indian subcontinent, Tibet, and the Caucasus. Females lay one or two eggs in mid-winter that hatch at the beginning of spring.
Etymology
The genus name Gypaetus is from Ancient Greek gupaietos, a corrupt form of hupaietos meaning "eagle" or "vulture". The specific epithet barbatus is Latin meaning "bearded" from barba, "beard". The name "lammergeier" originates from the German word Lämmergeier, which means "lamb-vulture". The name stems from the belief that it attacks lambs. The common name "ossifrage" is derived from the Latin word ossifragus, which literally means "bone-breaking," referring to the bird's diet consisting largely of bone. Ossifragus is also the root word for the osprey, which is within the same order, Accipitriformes, as vultures.Taxonomy
The bearded vulture was formally described in 1758 by Carl Linnaeus in the tenth edition of his Systema Naturae. He placed it with the vultures and condors in the genus Vultur and coined the binomial name Vultur barbatus. Linnaeus based his account on the "bearded vulture" that had been described and illustrated in 1750 by George Edwards who had based his hand-coloured etching on a specimen that had been collected at Santa Cruz near the town of Oran in Algeria. Linnaeus specified the type locality as Africa, but in 1914 this was restricted to Santa Cruz by Ernst Hartert.The bearded vulture is the only species in the genus Gypaetus that was introduced in 1784 by Gottlieb Storr.
Subspecies
Two subspecies are recognised:- G. b. barbatus includes G. b. hemachalanus and G. b. aureus in southern Europe and northwest Africa to northeast China through the Himalayas to Nepal and west Pakistan
- G. b. meridionalis in southwestern Arabia and northeastern, eastern and southern Africa
Description
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 grey, rusty, and whitish in colour. 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 thought to be cosmetic. This colouration comes from dust-bathing or rubbing iron-rich mud on its body. They also transfer the brown colour to the eggs. The tail feathers and wings are dark grey. The juveniles are dark black-brown over most of the body, with a grey-brown breast, gradually attaining more adult-like plumage over successive years; they take five to seven years to reach full maturity, with the first breeding at eight years or older. The bearded vulture is silent, apart from shrill whistles in their breeding displays and a falcon-like cheek-acheek call made around the nest.
Physiology
The acidity of the bearded vulture's stomach acid has been estimated to be around a pH of 1. Large bones are digested in about 24 hours, aided by slow mixing or churning of the stomach contents. Protein retained in the bone matrix makes bones a feasible energy source to that of muscle, with 140g of dry bones containing protein equivalent to 111g of muscle. The high lipid content of bone marrow make fresh bones exceed the energy content of muscle, with fresh bones containing about 108% of the energy of fresh meat by weight. 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.Distribution and habitat
The bearded vulture is sparsely distributed across a vast range. It occurs in mountainous regions in the Pyrenees, the Alps, the Arabian Peninsula, the Caucasus region, the Zagros Mountains and Alborz Mountains in Iran, the Koh-i-Baba in Bamyan, Afghanistan, the Altai Mountains, the Himalayas, Ladakh in northern India, and western and central China. In Africa, it lives in the Atlas Mountains, the Ethiopian Highlands and south from Sudan to northeastern Democratic Republic of the Congo, central Kenya, and northern Tanzania. An isolated population inhabits the Drakensberg in South Africa. It has been reintroduced in several places in Spain, such as the Sierras de Cazorla, Segura and Las Villas Jaén, the Province of Castellón and Asturias. The resident population as of 2018 was estimated at 1,200 to 1,500 individuals.In Israel it is locally extinct as a breeder since 1981, but young birds have been reported in 2000, 2004, and 2016. The species is extinct in Romania, the last specimens from the Carpathians being shot in 1927. However, unconfirmed sightings of the bearded vulture happened in the 2000s, and in 2016 a specimen from a restoration project in France also flew over the country before returning to the Alps.
In southern Africa, the total population as of 2010 was estimated at 408 adult birds and 224 young birds of all age classes therefore giving an estimate of about 632 birds.
In Ethiopia, it is common at garbage dumps tips on the outskirts of small villages and towns. Although it occasionally descends to, the bearded vulture is rare below altitudes of and normally resides above in some parts of its range. It typically lives around or above the tree line which are often near the tops of the mountains, at up to in Europe, in Africa and in central Asia. In southern Armenia, it breeds below if cliff availability permits. It has even been observed living at elevations of in the Himalayas and been observed flying at a height of.
There are two records of bearded vultures from the Alps reintroduction schemes which have reached the United Kingdom, with the first sighting taking place in 2016 in Wales and the Westcountry. A series of sightings took place in 2020, when an individual bird was sighted separately over the Channel Island of Alderney after migrating north through France, then in the Peak District, Derbyshire, Cambridgeshire, and Lincolnshire. The bird, nicknamed 'Vigo' by Tim Birch of the Derbyshire Wildlife Trust, originated from the reintroduced population in the Alps. As these two birds were both released captive birds, not wild, they have been placed in Category E, and not added to the formal British bird list.
Behaviour and ecology
Diet and feeding
The bearded vulture is a scavenger, feeding mostly on the remains of dead animals. Its diet comprises mammals, birds and reptiles, with medium-sized ungulates forming a large part of the diet. It usually disdains the actual meat and typically lives on 85–90% bones including bone marrow. This is the only living bird species that specializes in feeding on bones. Meat and skin only makes up a small part of what the adults eat, but scraps of meat or skin makes up a larger amount of the chicks' diet. 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. Their favoured variants of bones to consume consist of fattier and elongated bones like tarsal bones and tibias. They contain higher levels of oleic acid that is more nutritional for them than smaller bones, which contain less accessible bone marrow. The bearded vulture will crack bones too large to be swallowed by carrying them in flight to a height of 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 in diameter and weighing over, 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 relates to this habit. Less frequently, these birds have been observed trying to break bones by hammering them with their bill directly into rocks while perched. During the breeding season they feed mainly on carrion. They prefer the limbs of sheep and other small mammals and they carry the food to the nest, unlike other vultures which feed their young by regurgitation.
Bearded vultures sometimes attack live prey: perhaps more often than other vultures. Among these, tortoises seem to be especially favoured depending on their local abundance. Tortoises preyed on may be nearly as heavy as the preying vulture. To kill tortoises, bearded vultures fly with them 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 seized predaceously and dropped in flight. Among these are rock hyraxes, hares, marmots and, in one case, a 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. This is unconfirmed, however, and if it does happen, most biologists who have studied the birds generally agree 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 or killed with beating wings by the vulture. When foraging for bones or live prey while in flight, bearded vultures fly fairly low over the rocky ground, staying around high. Occasionally, breeding pairs may forage and hunt together. In the Ethiopian Highlands, bearded vultures have adapted to living largely off human refuse.