Current view: Data table and detailed info
Taxonomic note
Asarcornis scutulata (del Hoyo and Collar 2014) was previously placed in the genus Cairina.
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. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
not a migrant |
Forest dependency |
high |
| Land-mass type |
continent
shelf island
|
Average mass |
- |
Population justification: Compiling an accurate global population size estimate for this species is obfuscated by a lack of robust count data from large parts of its range, but evidence of continuing declines from already low numbers (BirdLife International 2001) suggests that the global population size may now be very small. The status in each range state is discussed approximately from west to east / north to south.
India was long-considered this species' stronghold but it is evident that the species occupies considerably fewer sites, and in fewer numbers, than it did three generations ago (BirdLife International 2001, Ahmed et al. 2023). The Indian population was previously estimated to number 300–400 individuals based on surveys in the early 1990s (Choudhury 1996), however is postulated now to be 'far less as the species has lost a significant part of its habitat in the last 25 years' (Ahmed et al. 2023). As evidence, the species has disappeared from several formerly occupied sites (see Figure 2: Ahmed et al. 2023), with no records in recent surveys from, for example, Dibru-Saikhowa National Park and Doomdooma Dangori Reserve Forests, which had 'large populations' of White-winged Duck in the 1990s (Talukdar and Bhattacharjee 1994, Choudhury 1996). Recent surveys found only a total of 24 individual ducks from three forest areas (Ahmed et al. 2023). Rationalising these data into population estimates is difficult in the absence of coordinated counts, but recent observations from even purported strongholds have rarely involved more than 1–2 pairs being seen, and combined with the collapse in the number of sites with recent observations, it is estimated that since counts of the early 1990s, the population in India has declined considerably. The precise number may be uncertain, but the conclusion from the limited evidence above is that the maximum population in India is unlikely to exceed 150 adults. Most plausibly, the Indian population now falls within a band of 50-150 mature individuals.
In Myanmar, data are even more sparse. Nonetheless, recent surveys (2016–2020) found birds persisting along the Chindwin River (and its tributaries) in Sagaing and Kachin, principally at Hukuang and Htamanthi Wildlife Sanctuaries. At Hukuang Valley WS the species remained regularly reported 'on all main streams and oxbow lakes surveyed' (R. Tizard pers. obs., in Chowdhury et al. 2020). Tordoff et al. (2007) suggested that the population of White-winged Ducks here was 'several times greater' than the 10 birds they counted in surveys conducted in 2003–2005, and this is validated by an observation of 19 birds (not all of which, however, were likely to be mature individuals) observed in the Hukaung Valley WS in August 2009 (eBird 2023). The total population in Myanmar is precautionarily estimated at 40–100 mature individuals, accounting for observations of rapid habitat loss and degradation at both wildlife sanctuaries (particularly since 2016: Global Forest Watch 2023) which is likely to have (potentially significantly) reduced numbers since many of these surveys were carried out.
In Thailand, very few wild birds remain. A recent photographed record from Thung Yai Naresuan WS (eBird 2023) indicates that a population probably persists in Thailands remote western forests, but the area of suitable habitat here indicates that this is unlikely to comprise a large population. A recent reintroduction project at Phu Khiao WS is yet to be proven self-sustaining. White-winged Duck is almost certainly extinct in Peninsular Thailand and Peninsular Malaysia. There are no recent records from Viet Nam or Lao PDR, where it is probably extinct (or, if any population does persist, must now be tiny and functionally so) (Timmins et al. in press, eBird 2023).
In Cambodia, the population has declined since a proposed estimate of 100 birds in 2007 (J.C. Eames in litt.) and likely now comprises (potentially far) fewer than 50 mature individuals (S. Mahood in litt. 2023), with no recent records away from Preah Vihear (C. Poole in litt. 2023).
In Indonesia, the population has evidently totally collapsed since BirdLife International (2001) identified 20 then recent (1980–2000) sites on Sumatra, most of which have now been totally denuded of forest. Across the island it is now very rare, with remnant populations confirmed from only Way Kambas National Park (where probably fewer than 20 mature individuals) and the Kampar Peninsula (where similar numbers would probably be an optimistic estimate). There are (few) other localities where the species could still persist (e.g. Berbak National Park); the Sumatran population is estimated here to number 30–60 mature individuals, with the lower estimate of this probably being most accurate. There have been no records from Java for over 50 years (BirdLife International 2001) and here it is assumed extinct.
Combining all these data presents an estimate with considerable uncertainty totalling 165–380 mature individuals, which is rounded to 150–450 here to account for additional uncertainties with the data used, but noting that a population size at the lowest end of this estimate is now probably the most likely.
Trend justification: This species' population is estimated to have declined very rapidly owing to the widespread loss, degradation and disturbance of lowland forest wetland habitats. Remaining populations are small, fragmented and of unknown viability but available data suggest a collapse in both range and abundance over the past three generations (26 years: 1997–2023), including in areas where the extent of suitable habitat hasn't changed, suggesting that this species is particularly prone to fragmentation and stochastic events that are poorly understood. Much of this loss was historical, with the map of all known localities presented in BirdLife International (2001: 413) almost unrecognisable when compared to contemporary distribution maps (cf., e.g., eBird 2023). Nonetheless, recent rapid declines are suspected also. Range states are discussed below approximately west to east / north to south.
In India, a lack of recent data make difficult an attempt to calculate plausible rates of decline, but the previous estimate made in the 1990s that the country hosts 300–400 mature individuals seems unreconcilable with recent observations (see Population Size justification). Here the population is thought to have declined by 50–90% over the past three generations, with an urgent need to work out population numbers at each remaining site, particularly the species' two Indian strongholds: Nameri Forest and Dihing–Patkai (eBird 2023, Ahmed et al. 2023).
In Myanmar, declines since 1997 are even less understood, with most sites identified in BirdLife International (2001) with confirmed records from only pre-1980. Nonetheless, many of these sites probably were occupied three generations ago, with records from this era lacking due to a lack of survey effort. If this is the case, the species has probably declined rapidly too, with almost no suitable habitat away from the country's north. Nonetheless, this assumption is hard to test. More recently, deforestation rates in the species' stronghold in the Hukaung Valley have been high (Hansen et al. 2013, Papworth et al. 2017, Global Forest Watch 2023) and declines are assumed to be continuing, despite this region's critical importance.
In Thailand, White-winged Duck had already declined considerably by the late 1990s, but even then persisted locally in Peninsular Thailand, and at Phu Kradung and Nam Nao National Parks, and (naturally) at Phu Khieo Wildlife Sanctuary. It has since disappeared from these three areas, although a reintroduction project at the last-named has begun. Rates of decline over the past three generations are difficult to determine in Thailand; they are likely to have been steep (>70%) but involving a low number of individuals. In Lao PDR has declined rapidly, probably to extinction, in the past three generations. In the late 1990s White-winged Duck was still known to occur on the Nakai Plateau and in the Xe Kong/Bolaven Plateau region (albeit in small numbers), as well as Dong Kanthung (Duckworth et al. 1999). Evans et al. (1997) estimated population sizes of 6–24 adults on the Nakai Plateau and 15–45 in Champasak and Attapu provinces, suggesting a total population of 21-69 mature individuals at that time. The species is now probably extirpated in Lao PDR, or has a population so small that it is unlikely to be functional (Timmins et al. in press). In Cambodia the population size in the 1990s is poorly known, but up to 2007 the country was thought to host up to 100 birds (J. Eames in litt. 2007). The population has declined rapidly since then (estimated here at 50–90%) and likely now comprises (potentially far) fewer than 50 mature individuals (S. Mahood in litt. 2023), with no recent records away from Preah Vihear (C. Poole in litt. 2023). In Viet Nam, has probably been extirpated within in the last three generations although even by the 1990s it was known from only Cat Tien National Park, where birds reportedly persisted until 2005; there have been no more recent records (eBird 2023).
In Indonesia, declines have evidently also been very rapid. BirdLife International (2001) estimated then that Sumatra hosted 150, but it is probable that this was an underestimate (certainly if 150 mature individuals was correct, it indicates a then island-wide density considerably lower than that in suitable habitat observed now). Although it is difficult to backcast population sizes, it is possible that up until the 1990s, the island hosted 2–3 times this number given the area of undisturbed lowland forest still present at that time, of which more >85% has since been cleared (Global Forest Watch 2023). There are no recent records made (or areas of suitable habitat) on the western side of the island, where BirdLife International (2001) identified several occupied localities. The species likely went extinct on Java more than 50 years ago (BirdLife International 2001).
In the counterfactual scenarios used here, the global population size of this species three generations ago is suspected of having been c.800–1,400 mature individuals, with declines over the same period calculated as approximately 40–90%. This previous population size estimate is similar to those made previously, but may in fact be overly pessimistic for the abundance of the species at that time. For example, Evans et al. (1997) thought the global population was probably 'a few thousand', while Callaghan et al. (1998) thought the non-Indonesian population alone numbered 1,000–5,000 birds. Consequently, while rates of declines over the past three generations are thought to lie within the band of 40–90%, the best estimate is placed at the top end of this band (70–90%), to reflect the very high likelihood that the population size (and range) of this species has collapsed over the past two decades.
Future rates of decline are highly uncertain, but it is apparent that protected areas alone are not sufficient in preventing localised extinctions of this species, which may be highly susceptible to fragmentation as well as threats that can permeate ineffective or poorly managed protected areas. Declines in all parts of its range are thought to be ongoing, so it is difficult to imagine how they may slow in the future. Certainly, if future rates of decline match those over the past 20 years, the species will soon be on the precipice of extinction. Rates of continuing decline are therefore set at the same rates of past ones (i.e. 40–90%, with a best estimate of 70–90%).
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
Recommended citation
BirdLife International (2024) Species factsheet: White-winged Duck Asarcornis scutulata. Downloaded from
https://datazone.birdlife.org/species/factsheet/white-winged-duck-asarcornis-scutulata on 19/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 19/12/2024.
