Largest ever count of White-shouldered Ibis

Jonathan C Eames White-shouldered Ibis Pseudibis davisoni, at roost, Western Siem Pang, Cambodia

Cambodian conservationists recently counted the largest number of White-shouldered Ibis Pseudibis davisoni ever recorded. At least 161 were counted; confirming that Western Siem Pang is the single most important site for the species and that the previous global population estimate was an underestimate.

In June, with partial funding from Critical Ecosystem Partnership Fund [1], Birdlife International Cambodia Programme and University of East Anglia (UEA), UK, team conducted a count at well known ibis roost sites in Western Siem Pang Important Bird Area, Stung Treng Province, Cambodia. At Srea Sang Kea, an area comprising of dry deciduous forest and rice fields, the team recorded four flocks leaving their roost, totaling 161 birds.

This is the largest single count of White-shouldered Ibis on record. The total number of White-shouldered Ibis is likely to be even higher than this figure, as many more roost sites are being found in Western Siem Pang. Another 46 birds were counted the same day as the record count, 12 km away at a site named Trapaeng Krous. The counts took place at different times so double counting cannot be ruled out.

Birdlife International’s recently updated 2009 IUCN Red List estimates that the world population of the White-shouldered Ibis is no more than 250 individuals, and possibly as low as 50. UEA PhD student Hugh Wright, who is researching the species at Western Siem Pang and elsewhere in Cambodia said “the population of White-shouldered Ibis in Cambodia probably exceeds the Red List’s highest population estimate, meaning the global population is larger than originally thought.” Previously the highest counts of the White-shouldered Ibis were 70 in 2005 and 108 in 2006, both in Western Siem Pang.

The recent sightings emphasise the international importance of Western Siem Pang, making a strong case for it being the single most important site for the survival of the species.

“Western Siem Pang consistently yields the highest counts of this species anywhere in the world. I am thrilled we have broken our best ever count yet again and delighted too that we are pushing the global population estimate forever upward." said Jonathan C Eames, Programme Manager of Birdlife International in Indochina. "The fact that we can do this and need to revise the global population estimate shows how little we know about this species.  We just don’t know why we have so many White-shouldered Ibis at Western Siem Pang. My hunch is that the species is resident so we are not recording movements of birds from elsewhere. I also believe that cattle and buffalo stocking density is key to understanding the density and abundance of the species.” said Mr. Eames.

Western Siem Pang is home to Cambodia’s 'Big Five'. The site currently supports five Critically Endangered bird species making it unique outside of Cambodia.  The other four are: Giant Ibis Thaumatibis gigantea, White-rumped Vulture Gyps bengalensis, Slender-billed Vulture Gyps tenuirostris, and the Red-headed Vulture Sarcogyps calvus. "The numbers of White-shouldered Ibis and the presence of populations of four other Critically Endangered species, make Western Siem Pang an irreplaceable site we have got to conserve.” Mr. Eames commented further. 

Western Siem Pang is currently unprotected. BirdLife has been active at the site for several years already, undertaking species monitoring and awareness activities. Together with the Forestry Administration, BirdLife are now actively advocating the designation of a Protected Forest covering a large part of the site. At the end of this month UEA will coordinate a nationwide coordinated roost count in Cambodia, in partnership with BirdLife, Wildlife Conservation Society, and World Wildlife Fund. The survey will provide the most accurate count ever of White-shouldered Ibis. “In order to save this species a great deal of research is required to understand its ecology and relationships with local people. As research continues, UEA and its partners hope to provide concrete conservation recommendations for this species." said UEA PhD student Hugh Wright.