White-shouldered ibis (Pseudibis davisoni)

As its common name suggests, this large, blackish ibis has a contrasting white patch on the inner forewing, or ‘shoulder’, although this is often concealed on standing birds ⁽²⁾. The head is naked and dark, with a distinctive pale, bluish-tinged collar, and a long, downward-curving bill ⁽²⁾. Immature birds have a dull brown plumage and, unlike their parents, a feathered head ⁽³⁾.

Also known as

Davison’s ibis.

Size

Size: 75 – 85 cm ⁽²⁾

Very little is known about the white-shouldered ibis, its diet or life-history patterns ⁽³⁾. This bird is thought to feed singly, in pairs or in family groups ⁽³⁾, and has been reported stalking for long periods around recently burnt patches of grassland ‘looking into cracks of the soil for small reptiles’ ⁽⁴⁾. This bird has also been observed foraging on gravel banks and mud banks for small items of prey ⁽⁴⁾. Old records indicate that the main food items include grasshoppers, cicadas and grain ⁽³⁾.

The available evidence suggests that this species breeds between February and July, although the breeding season may vary with location. While some ibis species breed in large colonies, the white-shouldered ibis is believed to be a solitary nester ⁽⁴⁾. Nests are built in trees at a height of five to ten metres above ground, and two to four eggs per clutch is thought to be normal ⁽³⁾.

Having declined significantly from much of its former range during the course of the 20th Century, the white-shouldered ibis is now confined to just a few sites in southern Vietnam, extreme southern Laos, northern Cambodia and East Kalimantan in Indonesian Borneo ^{(2) (4)}. The species is extinct in Thailand and no recent records exist from Myanmar (where there is some possibility of confusion between this species and the Black Ibis Pseudibis papillosa in historical records) ^{(2) (4)}. Fewer than 250 mature individuals are thought to remain ⁽²⁾.

Found in lakes, pools, marshes and slow-flowing watercourses in open, level, lowland forest, often subject to seasonal flooding, as well as sparsely wooded, dry or wet grasslands, paddyfields and other cultivation, and wide rivers with sand and gravel bars ⁽²⁾ 3).

Classified as Critically Endangered (CR) on the IUCN Red List 2007 ⁽¹⁾.

The white-shouldered ibis has been left with an extremely small, fragmented, vulnerable population of fewer than an estimated 250 mature individuals, after having suffered dramatic declines as a result of deforestation, drainage of wetlands, hunting and disturbance. Much of the species’ historical decline is due to habitat loss through logging of lowland forest and drainage of wetlands for agriculture (most of the Mekong floodplain in southern Laos has been converted to rice-paddy), livestock-grazing, grass-harvesting and development. Habitat destruction has been compounded by hunting for food and human disturbance, which now pose the greatest threats to the species ⁽²⁾.

The white-shouldered ibis is legally protected in Indonesia, Myanmar and East Malaysia ⁽⁴⁾, and occurs in several protected areas, including Cat Tien National Park, Vietnam, where it probably breeds, Ang Trapeang Thmor, Cambodia, and Xe Pian National Biodiversity Conservation Area (NBCA) and Dong Khanthung proposed NBCA, Laos ⁽²⁾. BirdLife International's Cambodia Programme Office is working with relevant government departments to promote Western Siem Pang as a protected area, a site that supports the only known potentially viable population (up to 70 individuals) of white-shouldered ibis in mainland Southeast Asia, and which contains three other Critically Endangered birds. In partnership with local communities, ongoing public awareness campaigns are being conducted in Laos and Cambodia to educate people about the status of these bird populations, discourage persecution and establish activities to prevent further population declines ⁽⁵⁾. The governments of Laos and Vietnam are also having notable success in controlling gun ownership, which is apparently benefiting populations of large waterbirds in some areas, and may be helping the white-shouldered ibis ⁽⁴⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on the white-shouldered ibis see:

• BirdLife International. (2001) Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.

Colonies

A group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds.

1. IUCN Red List (May, 2008)
   http://www.iucnredlist.org
2. BirdLife International (November, 2006)
   http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3799&m=0
3. del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World – Ostrich to Ducks. Vol. 1. Lynx Edicions, Barcelona.
4. BirdLife International. (2001) Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.
5. BirdLife International: Record counts of threatened ibis (November, 2006)
   http://www.birdlife.org/news/news/2006/01/white-shouldered_ibis.html