White-shouldered Ibis Pseudibis davisoni Scientific name definitions

60–85 cm. Large, dark ibis with distinctive blue bare mid hindcrown  and nape down to upper hindneck, spreading round and becoming bold white below ear-coverts to upper throat, forming a complete collar on upper neck, broadest at back, narrowest at front (1 Collar, N.J. and Eames, J.C. (2008). Head colour and sex-size dimorphism in Pseudibis papillosa and P. davisoni. BirdingASIA. 10: 36-40. Close ); dark overall, with blackish, naked head  , dull red legs  , but white patch on lesser wing-coverts very often not visible on standing bird. Male generally larger with a longer bill (1 Collar, N.J. and Eames, J.C. (2008). Head colour and sex-size dimorphism in Pseudibis papillosa and P. davisoni. BirdingASIA. 10: 36-40. Close ). Slightly larger than very similar P. papillosa, with different head pattern (latter has red patch on hindcrown and nape, and lacks white collar), while davisoni is also more robust, has longer neck and legs, and relatively shorter tail, spreading downwards rather than straight, and somewhat downcurved (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ); Thaumatibis gigantea is much larger with uniformly paler, dark-barred head, upper neck, wing-coverts and secondaries. In Borneo, considerable variation in head pattern in this species has been observed (and demands further research), including birds with a cobalt-blue crown and nape (most birds, especially along Mahakam R) (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ); an all bluish-white head apart from a dark mask (mainly along Ratah R) (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ); a broad white nape-patch; a broad white patch from mid-crown to nape; and a crown as in Indochinese birds, with a suggestion of a variably intense facial mask in these types (1 Collar, N.J. and Eames, J.C. (2008). Head colour and sex-size dimorphism in Pseudibis papillosa and P. davisoni. BirdingASIA. 10: 36-40. Close ). Immature has dull brown plumage; head feathered.

Once widespread from Myanmar to SW China and S to Indochina and Borneo, range now much reduced; small remaining population now focused on N Cambodia, with tiny additional numbers in adjacent S Laos and, disjunctly, in S Borneo (mainly along R Mahakam) (4 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila 9: 26–40. Close ).

Similar preferences to those exhibited by T. gigantea, at least in Indochina (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ). Marshes , seasonally flooded areas, abandoned paddyfields (including fallow sites) (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ) and other cultivation, shrub, grasslands and edges of lakes and large rivers; recent sightings in Borneo associated with riverine forests; in Cambodia inhabits dry dipterocarp forests, preferring pools (trapaengs) with greater cover of short vegetation (< 25 cm) and less of boundary enclosed (but shows immediate response to rain, whereafter sightings at trapaengs are scarce and encounters in forest itself increase), and forest sites with greater cover of bare substrate (positively influenced by livestock density) and lower people encounter rate (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ). Compared to T. gigantea, present species is generally found at shorter distances from human settlements throughout the year (8·3 km versus 9·9 km) and at trapaengs in the dry season P. davisoni used drier microhabitats (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ).

Presumably sedentary, but on Borneo most rivers exhibit large fluctuations (short-term and seasonal) in water level and the presence of exposed banks varies considerably, necessitating local movements to adjacent large rivers to access suitable feeding grounds, moving to the upper R Barito or R Apokayan or to the headwaters of the Mahakam’s tributaries (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ). Movements on Borneo may also be predictated by other events; for instance, droughts induced by the 1997–1998 El Niño Southern Oscillation event sparked large-scale forest fires over millions of hectares, especially near rivers, with boat surveys revealing significant changes in abundance and spatial distribution, e.g. ibis encounter rates were higher during pre-El Niño (1992–1996) periods than afterwards (1997–2000) and differed between seasons, with none seen along river sections affected by fires, where encounter rates were previously 2·4 birds/10² km, while encounter rates on those sections not affected by forest fires more than doubled from 2 birds/10² km to 5·6 birds/10² km (7 Sözer, R. and Nijman, V. (2005). Effects of ENSO-induced forest fires and habitat disturbance on the abundance and spatial distribution of an endangered riverine bird in Borneo. Animal Conservation. 8: 27-31. Close ).

Very little known until recently. Old records indicate main food includes grasshoppers, cicadas and grain, with recent unsubstantiated claims of feeding on fruit (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ) and direct observations of amphibians , small invertebrates (large worms, mole-crickets, leeches, insect and beetle larvae), eels, snakes and crabs (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ); at trapaengs in Cambodia, preferentially feeds on amphibians, with T. gigantea primarily selecting eels and otherwise larger prey (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ). Feeds singly , in pairs or in family groups (sometimes flocks of up to 14 (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ), with mean size of such groups in Cambodia being 5·9 ± 15·3 birds) (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ), probing in mud along riverbanks in Borneo (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ), although such habitat is generally shunned in Indochina, at least in the wet season, where even around trapaengs it is T. gigantea that prefers sites with greater expanses of wet mud (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ). In Cambodia, foraging sites include seasonal pools, forest understorey grasslands and fallow rice fields, with terrestrial sites used more following rainfall (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ), and flock size is greater in the wet (non-breeding) season (10·1 ± 25·1 birds) than in the dry (breeding) season (4·1 ± 7·3 birds) (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ), while largest recorded aggregation was 185 individuals just S of Western Siem Pang, Cambodia, in Sept.

Territorial birds utter loud, hoarse screaming “errrrrrh” or “errrrrroh” and moaning “errh errh errh errh”; also screams mixed with honking “errrrh owk owk owk owk”, more subdued “ohhaaa ohhaaa” and “errrr-ah” and harsh, loud “klioh, klioh” recalling Black Woodpecker (Dryocopus martius) during copulation, becoming more excited and reminiscent of Common Black-headed Gull (Larus ridibundus) as mating continues (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ).

Copulation observed Feb in Borneo (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ), with egg-laying in late Aug and mid Dec suggesting main season there is Sept–Dec (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ); season Feb–Mar in Burma (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ) and Dec–Apr (dry season) in Cambodia (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ). Breeding season in Cambodia may be timed to coincide with receding water levels and increasing substrate exposure, since amphibian concentrations in desiccating mud are the main food source there (9 Wright, H.L., Collar, N.J., Lake, I.R. and Dolman, P.M. (2013). Amphibian concentrations in desiccating mud may determine the breeding season of the White-Shouldered Ibis (Pseudibis davisoni). The Auk. 130(4): 774–783. Close ). Solitary. Nest built in trees , often large emergents, e.g. Koompasia excelsa (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ), in Borneo, sometimes at height of 5–10 m above ground, but two nests in Kalimantan were 30·2 m and 41·5 m above ground, and c. 10 and c. 60 m from rivers, respectively (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ), while in Cambodia breeds in dry dipterocarp forest (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ); nest  constructed of twigs  and fresh leaves, with material continuing to be added (by both sexes) throughout the breeding period (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ); sometimes uses old raptor nest (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ). Clutch 2–4 eggs, apparently pale blue in colour, incubated 28–29 days by female at least and hatch asynchronously (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ); chick  has pale yellow legs and bluish-white nape (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ); nestling period at least 26 days, possibly up to 40 days (on Borneo) (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ); young fed every 1–2 hours by both parents (8 Sutrisno, E., Imanuddin and Rachmady, R. (2009). Preliminary observations of the breeding biology of the Critically-endangered White-shouldered Ibis Pseudibis davisoni in East Kalimantan. Kukila. 14: 32-35. Close ). In 2009, 13 nests were found in Western Siem Pang, Cambodia, of which seven successfully fledged a total of 14 chicks. No other information available about breeding habits, although probably very similar to those of closely related P. papillosa.

CRITICALLY ENDANGERED. BirdLife International estimate the world population at just 650 mature individuals (based on a global population estimate of 731–856 birds in 2010) (10 Wright, H.L., Collar, N.J., Lake, I.R., Norin, N., Vann, R., Ko, S., Phearun, S. and Dolman, P.M. (2012). First census of the White-shouldered Ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia’s protected areas. Oryx. 46(2): 236–239. Close ) within an overall range of 88,900 km². Previously considered Vulnerable, but now uplisted given the paucity of records in the last few decades; however, if the largest surviving populations in Indochina can be effectively protected, might warrant downlisting. There was a record count of 754 birds in Cambodia in September 2012: an increase thought to result from improved knowledge of roost sites rather than an actual population increase; (11 Wright, H. L., Sok, K., Net, N. and Sum, P. (2013). White-shouldered Ibis Pseudibis davisoni population size and the impending threat of habitat conversion. Forktail. 29: 162–165. Close ). This was followed by a count of up to 973 birds in 2013, the highest figure since coordinated counts started in 2009. The global population is now put at c. 1200 birds, of which as many as 97% are in Cambodia.

Several recent sightings in Borneo, mainly along middle reaches of R Mahakam and its tributaries, E Kalimantan, where probable flock of 12 reported in 1989 and total of 134 individuals observed in 1994–1997 (prior to 1989 there were just 15 records in Borneo of which six were in the 1980s and several were perhaps unreliable) (2 Sözer, R. and van der Heijden, A.J.W.J. (1997). An overview of the distribution, status and behavioural ecology of White-shouldered Ibis in East Kalimantan, Indonesia. Kukila. 9: 126-140. Close ); however, no subsequent surveys in this region, although species has apparently declined more recently. In SE Asia no recent authenticated records until June 1991, when three birds seen in Nam Bai Cat Tien National Park, Vietnam (12 Robson, C. R., J. C. Eames, Nguyen Cu, and Truong Van La (1993). Birds recorded during the BirdLife/Forest Birds Working Group expedition in Vietnam. Forktail 9:89–119. Close ) (see Family Text ), with another record there in Dec 1994 (13 Dymond, J.N. (1998). Birds in Vietnam in December 1993 and December 1994. Forktail. 13: 7–12. Close ) and two records in Mekong delta in Mar and Aug 1999 (14 Buckton, S. (1999). Around the Orient: Important population of Sarus Crane found. Bull. Oriental Bird Club. 30: 24-25. Close ), but probably at best only a rare non-breeding visitor there now, with no records since the 1990s (10 Wright, H.L., Collar, N.J., Lake, I.R., Norin, N., Vann, R., Ko, S., Phearun, S. and Dolman, P.M. (2012). First census of the White-shouldered Ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia’s protected areas. Oryx. 46(2): 236–239. Close ); in Laos, where species has undergone major decline having been very common in parts of the country in mid-20th century, two records, in Mar 1993 and May 1995 (15 Thewlis, R. M., R. J. Timmins, T. D. Evans, and J. W. Duckworth (1998). The conservation status of birds in Laos: a review of key species. Bird Conservation International 8(Supplement):1–159. Close ), but none since (10 Wright, H.L., Collar, N.J., Lake, I.R., Norin, N., Vann, R., Ko, S., Phearun, S. and Dolman, P.M. (2012). First census of the White-shouldered Ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia’s protected areas. Oryx. 46(2): 236–239. Close ). Previous suggestion that species might persist in Cambodia confirmed in 1999 by observation of one near Trapeang Thmar (16 Pitches, A. (1999). Around the Orient: Cranes benefit from Khmer Rouge legacy. Bull. Oriental Bird Club. 30: 20. Close ), rapidly followed by sighting of 20 together in S Kampong Thom province (17 Kohler, M. (2000). Conservation Fund: Survey for Sarus Crane and other threatened bird species in southern Kampong Thom province, Cambodia. Bull. Oriental Bird Club. 31: 15–16. Close ); at present, breeding population of at least 108 (perhaps 142) individuals (and 262 birds overall) (5 Wright, H.L., Collar, N.J., Lake, I.R., Vorsak, B. and Dolman, P.M. (2012). Foraging ecology of sympatric White-shouldered Ibis Pseudibis davisoni and Giant Ibis Thaumatibis gigantea in northern Cambodia. Forktail. 28: 93–100. Close ), occurs in Western Siem Pang Important Bird Area, in N of country (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ), and national population estimated at minimum of 523 birds based on co-ordinated roost census in 2009–2010, with protected areas such as Kulen Promtep Wildlife Sanctuary, Lomphat Wildlife Sanctuary, Mondulkiri Protected Forest, Phnom Prich Wildlife Sanctuary and Seima Protection Forest also harbouring populations, but only 25·9–28·4% occur in legally protected areas (10 Wright, H.L., Collar, N.J., Lake, I.R., Norin, N., Vann, R., Ko, S., Phearun, S. and Dolman, P.M. (2012). First census of the White-shouldered Ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia’s protected areas. Oryx. 46(2): 236–239. Close ). In Thailand, where formerly occurred in central plains, peninsula and once extensive marshes of far north, no confirmed records since 1937, and now considered extinct; probably also lost from Sarawak (Malaysia) and Myanmar. Species never considered abundant; drainage and conversion of wetlands for agriculture on unrestrained scale throughout SE Asia must have had serious effects, and species’ largest known populations occur within unprotected landscapes, threatened by habitat conversion and changing land management through land concessions and unsustainable rural development (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ); succession of prolonged wars in region also likely to have contributed to decline, when hunting for food may also have affected the species’ numbers (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ). Habitat loss compounded by hunting of adults, eggs and chicks, and disturbance, leading to loss of secure feeding, roosting and nesting areas, while hunting pressure is exacerbated by fact that their primary habitats appear also to be a focus for people (but may now be less of a threat in Cambodia following education initiatives and confiscation of weapons) and poisoned baits affect some populations. Hunting may not be a serious threat in East Kalimantan, but fishing through poisoning and electro-fishing may negatively impact the population. Shy nature of species and limited amount of survey work carried out in much of range suggest might be more common than is thought. Research in Cambodia—where Western Siem Pang, currently the most important site, is unprotected and plantations will convert the majority of habitat by 2020, and proposed dams threaten Lomphat Wildlife Sanctuary and the unprotected central section of Mekong R, which also faces encroaching human settlement (10 Wright, H.L., Collar, N.J., Lake, I.R., Norin, N., Vann, R., Ko, S., Phearun, S. and Dolman, P.M. (2012). First census of the White-shouldered Ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia’s protected areas. Oryx. 46(2): 236–239. Close )—indicates that conservation strategies for this ibis must consider range of habitats, not only seasonal wetlands, and should incorporate extensive grazing and associated burning practices of local communities (6 Wright, H.L., Buckingham, D.L. and Dolman, P.M. (2010). Dry season habitat use by critically endangered white-shouldered ibis in northern Cambodia. Animal Conservation. 13(1): 71-79. Close ).