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.
| Population | Male bill length | Female bill length |
|---|---|---|
| Morocco | 141.1 mm (5.55 in) | 133.5 mm (5.25 in) |
| Turkey | 129.0 mm (5.08 in) | 123.6 mm (4.87 in) |
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.
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