White-shouldered Ibis

Appearance

The plumage is brownish-black, with glossy blue-black wings and tail, and a bare slate-black head that has also been reported as blue or white. A conspicuous neck collar comprising a bluish-white band of bare skin that is broader at the back and narrower at the front extends from the chin around to the nape at the base of the skull. The pale blue is most easily detectable at close range, although this collar may sometimes be completely white.

The adult stands 60–85 cm tall, with males being slightly larger and having slightly longer bills than females. Its only available biometrics are measurements from a single unsexed specimen originating from the 19th century, that include a wing length of 419mm, culmen length of 197mm, tarsus length of 83mm and tail length of 229mm.

Range and habitat

Other sites in Cambodia that hold considerable numbers of white-shouldered ibis include Kulen Promtep Wildlife Sanctuary, Lomphat Wildlife Sanctuary and the central section of the Mekong River. Thailand was once the stronghold for this species, but no official records of its occurrence have been made here since 1937. The white-shouldered ibis is a lowland specialist and has been observed in various habitats among them dry dipterocarp forest, margins of seasonal pools (these pools are known locally as "trapaengs") interspersed within forest, fallow rice fields, shrubby grasslands, forested lakesides and river margins, gravel and shingle banks at low river levels, sandbanks at wide rivers and, on the Sekong river, sandy islands.

In the last case for example, the relatively large subpopulations in Lomphat Wildlife Sanctuary and at the unprotected section of the Mekong River could be threatened with proposed dams and encroaching human settlement. Lomphat Wildlife Sanctuary is also an example region particularly threatened by economic land concessions, through that extensive development could substantially reduce suitable habitat.

Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.

Diet and breeding

Unlike other sympatric wading birds, the white-shouldered ibis is largely terrestrial in its foraging strategy and has not been seen foraging in open water. It preferentially forages in muddy seasonal pools covered with short vegetation less than 25 cm high, on the ground in dry dipterocarp forest preferentially with bare underlying substrate, in fallow rice fields, and more occasionally in river channels with large extents of mud and sand.

Even so, it forages almost exclusively at seasonal pools during the breeding season, probably due to high densities of refuge-seeking prey residing between the frequent cracks in the dry mud and hence high availability of food to feed to chicks. With its highly maneuverable, penetrative downcurved bill, the white-shouldered ibis is well adapted to probing into the cracks potentially harbouring concealed prey. The white-shouldered ibis is a solitary breeder.

In crisis

It is native to small regions of Southeast Asia, and is considered to be one of the most threatened bird species on this part of the continent. The white-shouldered ibis is considered one of the most threatened birds of SE Asia. The largest threats to populations of this species are habitat conversion such as wetland drainage for agricultural developments such as plantations, unsustainable rural development, changing land management through land concessions, and infrastructural developments.

The majority of roosting individuals censused in Cambodia (where the largest known populations occur) during the wet season (about three quarters) have been found to occur outside protected areas, revealing an unfortunate spatial mismatch between important roosting sites and these protected areas. This may be especially likely considering the local extinction or dramatic decline of many wild ungulate species whose role in ibis habitat creation and maintenance has been largely taken over by human-reared ungulates with equivalent functions.

White-shouldered Ibis is Critically Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.

Sources

Written for this catalog from the English Wikipedia article on White-shouldered Ibis, Wikidata item Q941864. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.