Ibis eremita

Identificazione

The northern bald ibis is a large, glossy black bird, 70–80 cm (28–31 in) long with a 125–135 cm (49–53 in) wingspan and an average weight of 1.0–1.3 kg (35–46 oz). The plumage is black, with bronze-green and violet iridescence, and there is a wispy ruff on the bird's hind neck. The face and head are dull red and unfeathered, and the long, curved bill and the legs are red. In flight, this bird has powerful, shallow, and flexible wing beats. It gives guttural hrump and high, hoarse hyoh calls at its breeding colonies, but is otherwise silent.<p>The sexes are similar in plumage, although males are generally larger than females, and, as with other ibises that breed in colonies, have longer bills. The longer-billed males are more successful in attracting a mate. The downy chick has uniformly pale brown plumage, and the fledged juvenile resembles the adult except that it has a dark head, light grey legs, and a pale bill. The unfeathered areas of the young bird's head and neck gradually become red as it matures. Moroccan birds have a significantly longer bill than Turkish birds of the same sex.<p>If the eastern and western populations are considered to be separable subspecies, it is unclear which should be considered to be the nominate (first-named) form, since the first description of this species was based on a now-extinct population from Switzerland which is of unknown race.<p>The northern bald ibis is readily distinguished from its close relative, the southern bald ibis of Southern Africa, by the southern species' whitish face. The northern bald can also be confused with the similarly dark-plumaged glossy ibis, which overlaps its range, but it is larger and stockier than that species. In flight, when the bill and face colouration may not be visible, the bald ibis' less rounded wings and shorter neck give it a different profile from glossy ibis, and its relatively short legs mean that its feet do not project beyond the tail, unlike those of the glossy ibis.

Tassonomia

The ibises are gregarious, long-legged wading birds with long down-curved bills. Along with the spoonbills they form one subfamily within the family Threskiornithidae. The northern bald ibis' closest relative, and the only other member of the genus, is the southern bald ibis, G. calvus, of southern Africa. The two Geronticus species differ from other ibises in that they have unfeathered faces and heads, breed on cliffs rather than in trees, and prefer arid habitats to the wetlands used by their relatives.<p>The northern bald ibis was described and illustrated by Swiss naturalist Conrad Gesner in his Historiae animalium in 1555, and given the binomial name Upupa eremita by Carl Linnaeus in his 1758 Systema Naturae. It was moved to its current genus by the German herpetologist Johann Georg Wagler in 1832. This species has an interesting history of description, oblivion and rediscovery.<p>The species probably split into two distinct populations at least 400 years ago and, since then, the two populations have been diverging morphologically, ecologically, and genetically; nevertheless, the Turkish and Moroccan populations of this ibis are not currently classed as separate subspecies. One consistent difference between the eastern and western birds is a single mutation in the cytochrome b gene of their mitochondrial DNA.<p>Fossils of the northern bald ibis have been found at a Holocene (c. 10,000 years ago) site in southern France, in middle Pleistocene (c. 900,000 years ago) strata in Sicily, and in Pliocene-Pleistocene boundary (c. 1.8 million years ago) deposits on the Mediterranean coast of Spain. What appears to be an ancestral form, Geronticus balcanicus, was found in the late Pliocene of Bulgaria, further illustrating the early widespread presence of this genus in Europe, and suggesting that Geronticus eremita may have originated in southeastern Europe or the Middle East.<p>The genus name, Geronticus, is derived from the Ancient Greek γέρων, meaning old man and refers to the bald head of the aged. Eremita is Late Latin for hermit, from the Greek ἐρημία, meaning desert, and refers to the arid habitats inhabited by this species. The alternative common name waldrapp is German for forest raven, the equivalent of the Latin Corvo sylvatico of Gesner, adapted as Corvus sylvaticus by Linnaeus.

Nome scientifico

Geronticus eremita

Autorità

(Linnaeus, 1758)

Ordine

Pelecaniformi

Famiglia

Threskiornithidae

Genere

Geronticus

Areale e habitat

Unlike many other ibises, which nest in trees and feed in wetlands, the northern bald ibis breeds on undisturbed cliff ledges, and forages for food in irregularly cultivated, grazed dry areas such as semi-arid steppes, and fallow fields. The close proximity of adequate steppe feeding areas to breeding cliffs is an important habitat requirement.<p>The northern bald ibis was once widespread across the Middle East, northern Africa, and southern and central Europe; fossil bones have been found at Solothurn dated to the Mesolithic and Neolithic Periods. It bred along the Danube and Rhone Rivers, and in the mountains of Spain, Italy, Germany, Austria and Switzerland (Gesner's original description was of a Swiss bird), and most probably also in the Upper Adriatic region. It used castle battlements as well as cliff ledges for nesting before vanishing from Europe at least three centuries ago. It is also extinct over most of its former range, and now almost the entirety of the wild breeding population of just over 500 birds is in Morocco, at Souss-Massa National Park, where there are three documented colonies, and near the mouth of the Oued Tamri (north of Agadir), where there is a single colony containing almost half the Moroccan breeding population. There is some movement of birds between these two sites.<p>Religious traditions helped this species to survive in one Turkish colony long after the species had disappeared from Europe, since it was believed that the ibis migrated each year to guide Hajj pilgrims to Mecca. The ibis was protected by its religious significance, and a festival was held annually to celebrate its return north. The Turkish ibis population was centred near the small town of Birecik in the southeast of the country, and during the first half of the 20th century, the Birecik colony maintained a relatively stable population of about 500 breeding pairs, reaching an estimated total population of about 3,000 around 1930. By the 1970s, numbers had drastically declined and a captive breeding program was initiated in 1977 with one adult pair and nine chicks taken from the wild. This program largely failed to revert the decline; there were 400 birds in 1982, five pairs in 1986, and seven pairs in 1987. Only three birds returned from their wintering grounds in 1989, and just one in 1990. The returning birds died before they could reproduce, thus rendering the species extinct in the wild in Turkey as of 1992. Once the wild Turkish population became non-viable, the colony was maintained as a flock which was free-flying for most of the year but caged in autumn to prevent migration.<p>After the demise of the migratory Turkish colony, the northern bald ibis was known to survive in the wild only at the Moroccan sites, although occasional sightings of birds in Yemen, Eritrea, Saudi Arabia, and Israel during the 1980s and 1990s suggested that there was still a colony somewhere in the Middle East. Intensive field surveys in spring 2002, based on the knowledge of Bedouin nomads and local hunters, revealed that the species had never become completely extinct on the Syrian desert steppes. Following systematic searches, 15 old nesting sites were found, one, near Palmyra, was still hosting an active breeding colony of seven individuals. Although the ibis had been declared extinct in Syria more than 70 years earlier, the bird appears to have been relatively common in the desert areas until 20 years ago, when a combination of overexploitation of its range lands and increasing hunting pressures initiated a dramatic decline.<p>The Moroccan breeding birds are resident, dispersing along the coast after the nesting season. It has been suggested that coastal fog provides extra moisture for this population, and enables the ibises to remain year-round. In the rest of its former range, away from the Moroccan coastal locations, the northern bald ibis migrated south for the winter, and formerly occurred as a vagrant to Spain, Iraq, Egypt, the Azores, and Cape Verde.<p>Satellite tagging of 13 Syrian birds in 2006 showed that the three adults in the group, plus a fourth untagged adult, wintered together from February to July in the highlands of Ethiopia, where the species had not been recorded for nearly 30 years. They travelled south on the eastern side of the Red Sea via Saudi Arabia and Yemen, and returned north through Sudan and Eritrea.

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: stabile.

Tendenza della popolazione

stabile