Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Pelecaniformes Threskiornithidae

Scientific Name: Thaumatibis gigantea
Species Authority: (Oustalet, 1877)
Common Name(s):
English Giant Ibis
Pseudibis gigantea gigantea Collar and Andrew (1988)
Pseudibis gigantea gigantea Collar et al. (1994)
Pseudibis gigantea gigantea Sibley and Monroe (1990, 1993)
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.
Identification information: 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 grey feathers on hindcrown and hindneck, lacking the dark bands on hindcrown and nape. Also 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 dry forests of the lower Mekong basin during the dry season.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2cd+3cd+4cd;C2a(i) ver 3.1
Year Published: 2013
Date Assessed: 2013-11-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S.
Contributor(s): Buckingham, D., Clements, T., Davidson, P., Duckworth, W., Evans, T., Keo, O., Kim Hout, S., Pollard, E., Rainey, H., Vann, R., Wilson, D. & Wright, H.
Facilitator/Compiler(s): Benstead, P., Calvert, R., Davidson, P., Mahood, S., Peet, N., Symes, A., Taylor, J., Tobias, J., Martin, R
This ibis has an extremely small population, which has undergone an extremely rapid decline as a result of hunting, disturbance and lowland deforestation. It is likely to continue to decline extremely rapidly owing to on-going deforestation and human disturbance. It therefore qualifies as Critically Endangered.

Previously published Red List assessments:
2012 Critically Endangered (CR)
2010 Critically Endangered (CR)
2009 Critically Endangered (CR)
2008 Critically Endangered (CR)
2004 Critically Endangered (CR)
2000 Critically Endangered (CR)
1996 Critically Endangered (CR)
1994 Critically Endangered (CR)
1988 Threatened (T)

Geographic Range [top]

Range Description:Thaumatibis gigantea is mostly confined to northern Cambodia, where it is probably still fairly widespread but extremely rare; with a few birds from the same population observed in extreme southern Laos (BirdLife International 2001). There is a fairly  recent record from Yok Don National Park, Vietnam (Anon 2003). Its historical range spanned southern Vietnam and south-eastern and peninsular Thailand, where it is now extinct. Available data suggest that it has a patchy distribution across Cambodia (T. Clements et al. in litt. 2007). Some areas of high density exist in the Northern Plains, including Preah Vihear Protected Forest and Kulen Promtep Wildlife Sanctuary (with 30-40 nests monitored annually [T. Evans in litt. 2012) and Western Siem Pang IBA (possibly 40 pairs [H. Wright in litt. 2012]). Other areas appear to have relatively low density populations, which may be clustered in some cases (Lomphat Wildlife Sanctuary, Seima Protection Forest [Bird et al. 2007, WCS/FA 2006], Mondulkiri Protected Forest [T. Gray in litt. per T. Evans] and Phnom Prich Wildlife Sanctuary [Claassen and Ou 2007]) (T. Clements et al. in litt. 2007, T. Clements et al. in prep.). Additional recent records have come from Veunsai proposed Protected Forest in Ratanakiri Province and the first observation south of Tonle Sap Lake since the 1920s was made by camera trap in 2011 (L. Perlman per T. Evans in litt.) Further surveys may confirm other localities in suitable habitat areas such as O Yadao Protected Forest and the unprotected areas west of Phnom Prich Wildlife Sanctuary (T. Evans in litt. 2012). A conservative estimate of the number of breeding pairs at the seven locations is given as 5-10 pairs (T. Evans et al. in litt. 2012).

Countries occurrence:
Cambodia; Lao People's Democratic Republic; Viet Nam
Regionally extinct:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):No
Estimated extent of occurrence (EOO) - km2:24700
Continuing decline in extent of occurrence (EOO):Yes
Extreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Recent assessment of the available records suggests a minimum estimate of 115 pairs (40 at each of the two high density sites, 5-10 at each of seven low density sites) (T. Evans, H. Rainey, R. Vann and H. Wright in litt. 2012). This is equivalent to a minimum of 230 mature individuals, and roughly 345 individuals in total.

Trend Justification:  An extremely rapid population decline is suspected to have occurred over the last three generations and is projected to occur over the next three generations, based on information from T. Clements (in litt. 2007), who has commented: "Deforestation scenarios project that Cambodia will lose 50% or more of its forest habitat in the next 25 years, a greater portion of which is expected to be in the lowland areas inhabited by Giant Ibis. For example, recent assessments have shown that Cambodia lost 1-2% of its forest annually during 2002-2006. Giant Ibises are known to be highly sensitive to human disturbance, hence increasing deforestation and habitat fragmentation would have a disproportionate effect on the remaining ibis populations".

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:230Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:Yes
No. of subpopulations:3-10Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No
No. of individuals in largest subpopulation:1-89

Habitat and Ecology [top]

Habitat and 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 (trapaengs). Its diet comprises a variety of invertebrates, crustaceans, eels, small amphibians and reptiles. It frequently feeds in soft mud, but forages on all substrates at trapaengs. It nests in trees, with a preference for large Dipterocarpus (Keo 2008), generally more than 4 km from human habitation (Keo 2008). Females almost always lay two eggs per clutch in the wet season (Keo et al. 2009). Pools and seasonally flooded grassland with earthworm mounds are important in the breeding season, from June to September (Keo 2008). It appears to be largely resident, but apparently wanders widely in response to local disturbance and seasonal water-levels. Generally territorial, the species remains in pairs or small family groups year-round. However, in the dry (non-breeding) season it may be found in small flocks of up to seven individuals or more (H. J. Rainey in litt. 2012).

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):8
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): It has declined as a result of hunting, wetland drainage for agriculture and deforestation. It relies on seasonal pools, which in the past were perhaps maintained by the now much depleted megafauna. Clearance of very large areas of lowland dry forest, including parts of the Northern Plains (Preah Vihear Protected Forest, Kulen Promtep Wildlife Sanctuary) and other areas (Lomphat Wildlife Sanctuary, Western Siem Pang IBA) where the species occurs, for agro-industry including rubber, cassava, wood pulp and teak plantations, has recently emerged as the greatest threat to this species. Generally the human population is increasing within the range of this species mostly through immigration from other provinces in Cambodia. Subsequent expansion of agricultural land and increasing hunting pressure and disturbance at feeding sites is causing the loss of breeding habitat for the species (An Dara 2008, Clements et al. in prep.). The species appears to be very sensitive to human disturbance (An Dara 2008), particularly during the dry season when both birds and humans are concentrated around available waterholes rendering much apparently suitable habitat unusable. 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 success (Keo 2008), a theory supported by a study which found that the number of young fledged per nest was 50% higher for protected nests (Keo et al. 2009). A prolonged drought in the 2009-2010 dry season appeared to dramatically lower the breeding success of Giant Ibis, by approximately 50%; climate change may therefore pose a long-term threat to the persistence of this species (H. Rainey in litt. 2012).

Conservation Actions [top]

Conservation Actions: Conservation Actions 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. Giant Ibis is depicted on public awareness materials in Laos and Cambodia as part of an on-going 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 without (Keo 2008). Most of the protected areas that the species occurs in have ongoing site-based protected area management projects with government and NGOs cooperating to raise funds and implement protection. Ongoing community nest protection activities are taking place in the Northern Plains where local community members are paid to protect Giant Ibis and other waterbird nests. This not only removes a primary threat to the population, but instils local ownership and pride in the charismatic large waterbirds in this landscape. This has stabilised Giant Ibis numbers and increased the populations of other species. Ecotourism projects in the Northern Plains landscape (Tmatboey, O Koki and Prey Veng) and marketing of certified wildlife-friendly agricultural produce ("Ibis Rice") should also benefit this species. 'Giant Ibis Transport' has taken on the role of Species Champion agreeing to provide $51,000 of funding over the next three years.

Conservation Actions Proposed
Improved commitment to conserve protected areas in Cambodia is required by all stakeholders to stabilise the giant ibis population. Advocacy with the Cambodian government to raise the profile of the ecological needs of Cambodia’s national bird will help improve protection of the large undisturbed areas of deciduous dipterocarp forest that this species requires. Conduct further surveys to locate and quantify remaining populations in Laos and Cambodia. Investigate its breeding requirements (including breeding season foraging ecology), 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 wildlife. Ensure some pools remain wet during the dry season (e.g. by preventing people from draining them for fishing, and also potentially managing pools to increase their depth) (Keo 2008). Protect and install anti-predator belts on all nest-trees, and protect potential nest-trees (Keo 2008). Monitor the abundance of frogs, eels and mole-crickets in the dry season (Keo 2008), and the impact that local harvesting of frogs may have on prey abundance (H. Wright in litt. 2012). Assess longer-term risk from climate change (T. Evans in litt. 2012).

Classifications [top]

1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
suitability: Suitable season: resident major importance:Yes
4. Grassland -> 4.6. Grassland - Subtropical/Tropical Seasonally Wet/Flooded
suitability: Suitable season: resident major importance:Yes
5. Wetlands (inland) -> 5.5. Wetlands (inland) - Permanent Freshwater Lakes (over 8ha)
suitability: Suitable season: resident major importance:Yes
5. Wetlands (inland) -> 5.7. Wetlands (inland) - Permanent Freshwater Marshes/Pools (under 8ha)
suitability: Suitable season: resident major importance:Yes
14. Artificial/Terrestrial -> 14.1. Artificial/Terrestrial - Arable Land
suitability: Suitable season: non-breeding major importance:No
1. Land/water protection -> 1.1. Site/area protection
2. Land/water management -> 2.1. Site/area management
2. Land/water management -> 2.2. Invasive/problematic species control
4. Education & awareness -> 4.3. Awareness & communications

In-Place Research, Monitoring and Planning
  Action Recovery plan:No
  Systematic monitoring scheme:Yes
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
  Occur in at least one PA:Yes
  Invasive species control or prevention:No
In-Place Species Management
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:No
In-Place Education
  Subject to recent education and awareness programmes:Yes
  Included in international legislation:No
  Subject to any international management/trade controls:No
1. Residential & commercial development -> 1.1. Housing & urban areas
♦ timing: Ongoing ♦ scope: Minority (<50%) ♦ severity: Rapid Declines ⇒ Impact score: Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing: Ongoing ♦ scope: Majority (50-90%) ♦ severity: Rapid Declines ⇒ Impact score: Medium Impact: 7 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.3. Agro-industry farming
♦ timing: Ongoing ♦ scope: Majority (50-90%) ♦ severity: Rapid Declines ⇒ Impact score: Medium Impact: 7 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.3. Livestock farming & ranching -> 2.3.2. Small-holder grazing, ranching or farming
♦ timing: Ongoing ♦ scope: Minority (<50%) ♦ severity: Slow, Significant Declines ⇒ Impact score: Low Impact: 5 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.1. Hunting & trapping terrestrial animals -> 5.1.1. Intentional use (species is the target)
♦ timing: Ongoing ♦ scope: Majority (50-90%) ♦ severity: Rapid Declines ⇒ Impact score: Medium Impact: 7 
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

5. Biological resource use -> 5.2. Gathering terrestrial plants -> 5.2.2. Unintentional effects (species is not the target)
♦ timing: Ongoing ♦ scope: Minority (<50%) ♦ severity: Slow, Significant Declines ⇒ Impact score: Low Impact: 5 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

6. Human intrusions & disturbance -> 6.3. Work & other activities
♦ timing: Ongoing ♦ scope: Majority (50-90%) ♦ severity: Rapid Declines ⇒ Impact score: Medium Impact: 7 
→ Stresses
  • 2. Species Stresses -> 2.2. Species disturbance

7. Natural system modifications -> 7.2. Dams & water management/use -> 7.2.11. Dams (size unknown)
♦ timing: Future ♦ scope: Minority (<50%) ♦ severity: Rapid Declines ⇒ Impact score: Low Impact: 4 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats

♦  Food - human
 Local : ✓   National : ✓ 

Bibliography [top]

An Dara. 2008. Agricultural expansion and its effects on breeding habitat of Giant Ibis Pseudibis gigantea in Kulen Promtep Wildlife Sanctuary, northern Cambodia. MSc Thesis, Tokyo University of Agriculture and Technology, Department of International Environmental and Agricultural Science.

Anon. 2003. Endangered species rediscovered in Yok Don National Park, Dak Lak province. The Babbler: BirdLife in Indochina 2(2): 12-13.

BirdLife International. 2001. Threatened birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, U.K.

Claassen, A. H.; Ou, R. 2007. A stream and wetland survey of southwestern Phnom Prich Wildlife Sanctuary and adjacent areas, with a focus on large waterbirds. WWF Greater Mekong,Cambodia Country Programme., Phnom Penh.

IUCN. 2013. IUCN Red List of Threatened Species (ver. 2013.2). Available at: (Accessed: 13 November 2013).

Keo, O. 2008. Ecology and conservation of the Giant Ibis Thaumatibis gigantea in Cambodia. BirdingASIA 9: 100-106.

Keo, O.; Collar, N. J.; Sutherland, W. J. 2009. Nest protectors provide a cost-effective means of increasing breeding success in Giant Ibis Thaumatibis gigantea. Bird Conservation International 19(1): 77-82.

WCS/FA. 2006. Threatened Species of the Seima Biodiversity Conservation Area. Wildlife Conservation Society - Cambodia Program, and Forestry Administration., Phnom Penh, Cambodia.

Citation: BirdLife International. 2013. Thaumatibis gigantea. In: The IUCN Red List of Threatened Species 2013: e.T22697536A49599895. . Downloaded on 09 October 2015.
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