Justification This ibis has an extremely small, declining population as a result of hunting, disturbance and lowland deforestation. It is likely to continue to decline owing to deforestation and human disturbance. It therefore qualifies as Critically Endangered.

Family/Sub-family Threskiornithidae

Species name author (Oustalet, 1877)

Taxonomic source(s) Sibley and Monroe (1990, 1993)

Synonyms Pseudibis gigantea Sibley and Monroe (1990, 1993), Pseudibis gigantea Collar et al. (1994), Pseudibis gigantea Collar and Andrew (1988)

Identification 102-106 cm. Huge, dark ibis. Adult is mostly dark with naked, greyish head and upper neck, dark bands on hindcrown and nape and pale greyish wing-coverts and secondaries with dark cross-bars. Juvenile has short black feathers on hindcrown and hindneck, shorter bill and brown eyes (dark red on adults). Similar spp. White-shouldered Ibis Pseudibis davisoni is smaller and uniformly darker with whitish collar and white patch on inner wing-coverts. Voice Repeated, loud, ringing a-leurk a-leurk at dawn and dusk. Hints Search remote permanent wetlands in the Mekong floodplain during the dry season.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

200

decreasing

24,700 km²

No

Range & population Pseudibis gigantea is confined to northern Cambodia, where it is probably still fairly widespread but extremely rare; with a few birds surviving in extreme southern Laos, and a recent record from Yok Don National Park, Vietnam¹. Its historical range spanned southern Vietnam and south-east and peninsular Thailand, where it is now extinct. Available data suggests that it has a patchy distribution across Cambodia². Some areas of high density exist (Preah Vihear Protected Forest and probably Siem Pang), whilst other areas appear to have relatively low density populations, which may be clustered in some cases (Kulen Prumtep Wildlife Sanctuary, Seima Biodiversity Conservation Area and probably Phnom Prich Wildlife Sanctuary)². Systematic surveys have yet to be done in the Mondulkiri Protected Forest and Lomphat Wildlife Sanctuary - the latter in particular may support higher densities². Together, this data suggests a minimum estimate of 100 pairs (20-30 at each of the two high density sites, 5-10 at each of seven low density sites)². Further surveys might be expected to confirm other localities in suitable habitat areas, particularly in Lomphat Wildlife Sanctuary, the O Te lowlands and adjacent deciduous dipterocarp forest².

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Singles, pairs or small parties occur in marshes, pools, wide rivers and seasonal water-meadows in open, predominantly deciduous, dipterocarp lowland forest, although it seems to be dependent on soft mud around seasonal pools (trapeangs). Its diet comprises a variety of invertebrates, crustaceans, small amphibians and reptiles. It frequently feeds in soft mud, but also forages on dry substrates. It nests in trees, with a preference for large Dipterocarpus³, generally more than 4 km from human habitation³. Pools and seasonally flooded grassland with earthworm mounds are important in the breeding season³. It appears to be largely resident, but apparently wanders widely in response to local disturbance and seasonal water-levels.

Threats It has declined as a result of hunting, wetland drainage for agriculture, and deforestation. It relies on seasonal pools, which in the past were created by the now much depleted megafauna. The species appears to be very sensitive to human disturbance, particularly during the dry season when birds are concentrated around available waterholes, and this is almost certainly the greatest threat, rendering much apparantly suitable habitat unusable. There are plans to clear large areas of lowland dry forest, including Western Siem Pang IBA where the species occurs, for teak plantations. Nest predation by common palm civet Paradoxurus hermaphroditus and/or yellow-throated marten Martes flavigula on two occasions in 2004 suggest that loss of nestlings to mammalian carnivores might be a significant constraint on breeding success³.

Conservation measures underway It occurs at least seasonally in Xe Pian National Biodiversity Conservation Area (NBCA) and Dong Khanthung proposed NBCA, Laos, and Lomphat Wildlife Sanctuary, Preah Vihear Protected Forest and Kulen Prumptep Wildlife Sanctuary in Cambodia. It is depicted on public awareness materials in Laos and Cambodia as part of an ongoing campaign to reduce hunting of large waterbirds. A predator-exclusion experiment in 2005-2006 found that nests with predator-exclusion devices (a smooth, hard plastic belt fixed around the base of the nest tree) were more likely to survive than those without³. Ecotourism projects in the Tmatboey region should benefit this species as well as White-shouldered Ibis.

Conservation measures proposed Conduct further surveys to locate and quantify remaining populations in Laos and Cambodia. Investigate its breeding requirements, demography and seasonal movements. Establish further protected areas encompassing large tracts of habitat found to support populations of the species, including strict protection of suitable permanent wetlands, especially in the dry season. Consolidate and promote further public awareness initiatives to reduce hunting of large waterbirds and wetland disturbance. At key sites, designate some suitable pools as for use only by ibises. Ensure some pools remain wet during the dry season (e.g. by preventing people from draining them, and potentially artificially managing pools by increasing their depth)³. Protect and install anti-predator belts on all nest-trees, and protect potential nest trees³. Monitor abundance of frogs, eels and mole-crickets in the dry season³.

References Birdlife International (2001). 1. Anon (2003). 2. T. Clements et al. in litt. (2007). 3. Keo (2008).

Further web sources of information

Fully detailed species accounts from the Threatened birds of Asia: the BirdLife International Red Data Book (BirdLife International 2001), together with new information collated since the publication of the Red Data Book

Text account compilers Phil Benstead (BirdLife International), Pete Davidson (BirdLife International), Simon Mahood (BirdLife International), Nic Peet (BirdLife International), Andy Symes (BirdLife International), Joe Tobias (BirdLife International)

Contributors David Buckingham, Tom Clements (Wildlife Conservation Society), Pete Davidson (BirdLife International), Will Duckworth (Wildlife Conservation Society), Tom Evans (Wildlife Conservation Society), Omaliss Keo (University of East Anglia), Seng Kim Hout, Edward Pollard (Wildlife Conservation Society), Duncan Wilson

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International), Andy Symes (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Thaumatibis gigantea. Downloaded from http://www.birdlife.org on 9/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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