Northern bald ibis

The northern bald ibis, hermit ibis, or Waldrapp (Geronticus eremita) is a migratory Old World ibis found in open areas such as grasslands, rocky mountains, and semi-deserts, often close to running water. This 70–80 cm (28–31 in) glossy black ibis, which, unlike many members of the ibis family, is non-wading, has an unfeathered red face and head, and a long, curved red bill. It breeds colonially on coastal or mountain cliff ledges, where it typically lays two to three eggs in a stick nest, and feeds on lizards, insects, and other small animals. The northern bald ibis was once widespread across the Middle East, northern Africa, southern and central Europe, with a fossil record dating back at least 1.8 million years. It disappeared from Europe over 300 years ago, although reintroduction programmes in the region are underway. In 2019 there were about 700 wild birds remaining in southern Morocco. To combat these low numbers, reintroduction programs have been instituted internationally in recent times, with a semi-wild breeding colony in Turkey which counted almost 250 birds in 2018 as well as sites in Austria, Italy, Spain, and northern Morocco. There are about 2000 northern bald ibises living in captivity. These programmes and the natural growth in Morocco from about 200 birds in the 1990s helped to downlist the northern bald ibis from Critically Endangered to Endangered on the IUCN Red List in 2018. The down-listing of conservation status for the species has been described as controversial decision and not taking fully into account the recent extinction in the wild of the genetically distinct and only long-range migratory population that used to breed in the Middle East and wintering in Eastern Africa. The long-term decline in Europe has been linked to hunting and use as food, especially the fledglings. The slow reproduction means this can cause local extinction.

Taxonomy 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.

The northern bald ibis was described and illustrated by Swiss naturalist Conrad Gessner 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.

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. 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.

Etymology The genus name, Geronticus, is derived from the Ancient Greek γέρων : gérōn, meaning old man and refers to the bald head of the aged. The species name eremita is Late Latin for hermit, from the Ancient Greek: ἐρημία : erēmía, 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.

Description

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. 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.

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. 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.

Habitat and range

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