BIODIVERSITY OF WESTERN SIEM PANG
BIRDS
forest areas. Two protected areas, Preah Vihear Protected Forest and Kulen Prumtep Wildlife Sanctuary, appear to have similar and perhaps even more favourable habitat (500 trapeangs within 40 km2 in one sector), as well as documented large populations of Giant Ibis (Relatively consistently 20 or more, and up to 41 nests are found annually in this combined area (WCS unpublished data); and a ball park estimate being upwards of 200 birds in these two areas (Keo Omaliss in litt. 2012)). Of the other protected areas likely supporting significant Giant Ibis populations suitable habitat is relatively extensive in Mondulkiri Protected Forest and Lomphat WS, but data are lacking on the current status of the species in both, while in Phnom Prich WS and Seima Biodiversity Conservation Area suitable habitat is largely localised and unlikely to support populations as significant as that in Western Siem Pang (Timmins and Ou Ratanak 2001, R J Timmins pers. comm.). The recent discovery of Giant Ibis in the Sre Ambel valley of the coastal southwest of Cambodia (Keo Omaliss in litt. 2012) essentially does not change the conclusions of Tordoff et al. (2005), and nor is it likely to significantly change the global conservation status of the species (see Timmins and Sechrest in press). The species ecology is poorly known, but scant evidence suggests that birds may be relatively sedentary throughout the year. Larger groupings seem rare, with monitoring teams, D. Buckingham and R. J. Timmins largely recording singles, duos or trios. The largest number of birds recorded in a day is 16 (J C Eames pers. comm.). Both R. J. Timmins and D. Buckingham both independently concluded from the location of survey records, clearly at times representing different groups of birds, present at times within one kilometre of each other, that densities along the O Khampha and O Cheangheang could be relatively high, with perhaps groups every few km or less. Within the central plains it is far less clear to what extent birds might range, but this presumably depends to some extent on the density and seasonality of trapeangs in various sectors. Giant Ibis are wet season breeders, but there has never been a concerted effort to find and monitor nests within Western Siem Pang. The only information on breeding appears to come from a single nest that was found and monitored during the wet season of 2010. One chick successfully fledged from this nest. In addition two juveniles were seen, by the monitoring team, with a pair of adults in early December 2009 at Trapeang Chhouk, and begging juveniles were reported by the SSG at this location also in late 2011 (BirdLife monitoring team, H L Wright pers. comm.). A begging juvenile was photographed being fed by an adult at Trapeang Thlork on 13 March 2010 (J C Eames pers comm.). Giant Ibis appears to be somewhat more wary, and potentially sensitive to disturbance, than White-shouldered Ibis and several observers have noted that the species is recorded less often from forest areas frequented by people, despite the presence of apparently suitable feeding habitat, both in Western Siem Pang (Buckingham and Prach Pich Phirun 2006, D Buckingham pers. comm., H L Wright pers. comm.) and from other dry forest areas (R J Timmins pers. comm., Keo Omaliss in litt. 2012). In Western Siem Pang Giant Ibis have a range of feeding habitats at both trapeangs and streams, and has been flushed from the Sekong river (J C Eames pers. comm.). At trapeangs they commonly feed at the wet muddy margins but sometimes in deep water (where a featherless head is an advantage) (J. C. Eames in litt. 2011). Trapeangs with tall and extensive vegetation that have no or very few open patches seem to be avoided (D Buckingham pers. 70
comm.), but the range of trapeang types and microhabitats that they utilise appears to be more extensive than that of Whiteshouldered Ibis (H L Wright pers. comm), and for instance they do readily use trapeangs with extensive tall vegetation where grazing and wallowing have created openings allowing birds access and they also forage in water covered substrates. They also extensively forage in viels, especially during the wet season (R J Timmins pers. comm., H L Wright pers. comm., Keo Giant Ibis found poisoned at Trapeang Svay Toych on Omaliss in litt. 2012). Along 11th January 2009. Photo: BirdLife. streams (including the Sekong) they appear to favour muddy banks, especially those covered in worm casts, but have also been observed foraging on sandy bars and shoals (R J Timmins pers. comm., D Buckingham pers. comm.). Observations suggest that during their breeding season, when the forest is wet, they prey to a large extent on the numerous earthworms that frequent the forest floor (H L Wright pers. comm.). During the dry season they have been observed feeding on eels and frogs (Box 8) at trapeangs (J. C. Eames in litt. 2011), and also crabs and leeches extracted from wet sticky mud (H L Wright pers. comm.). Observations elsewhere suggest that they also feed on insects, such as grasshoppers, which become seasonally abundant in viels and trapeangs vegetation during the wetter periods of the year (R J Timmins pers. comm.). The species apparent sensitivity coupled with its reliance during the dry season on localised trapeang and stream habitats, places the species at potentially severe risk from the increasing human use of these same habitats within Western Siem Pang (Timmins 2011, Wright 2011).
White-shouldered Ibis Pseudibis davisoni (Critically Endangered) White-shouldered Ibis was once widely but patchily distributed across much of Thailand, Laos, south and central Vietnam and Cambodia, parts of Myanmar and Borneo, and southwest Yunnan, China, but declined dramatically during the 20th century. Habitat loss has been compounded by hunting of adult birds, eggs and chicks for food, and disturbance, leading to the loss of secure feeding, roosting and nesting areas. The species is extinct in Thailand and China and there are no recent records from Myanmar, and it is almost certainly extinct as a breeding species in Vietnam and probably also in Laos. Breeding birds now only occur in northern and eastern Cambodia and East Kalimantan, Indonesia (BirdLife International 2010). Probably 90% of the existing population is in Cambodia, and within Cambodia, one of the most important sites is Western Siem Pang (Table 1.1.). White-shouldered Ibis distribution 71