White-winged Duck
Asarcornis scutulata
白翅栖鸭
Introduction
The White-winged Duck (Asarcornis scutulata) belongs to a monotypic genus with evolutionary ties to diving ducks in the genera Netta and Aythya. Its historical range extended from northeastern India through Southeast Asia to the Indonesian islands of Java and Sumatra. The current distribution is restricted to fragmented populations in northeastern India and Sumatra. This species inhabits dense tropical forests near rivers, swamps, and slow-moving waterways. It remains hidden during daylight hours and forages primarily after dusk. The IUCN lists this species as Endangered.
Description
This is one of the largest living duck species, comparable in size to steamer ducks but more slender. Adults measure 66-81 cm in length with an impressive wingspan of 116-153 cm. Males weigh 2.94-3.9 kg while the smaller females range from 1.95-3.05 kg. The most striking feature is the contrast between the dark body and the whitish head and neck. Males display a dull yellowish bill with blackish mottling on the head and upper neck, white lesser median coverts, inner edges of tertials, and bluish-grey secondaries. In flight, the white wing-coverts create a distinctive contrast against the darker wings. Females are notably smaller and typically show denser mottling on the head and upper neck. Juveniles appear duller overall with browner plumage throughout.
Identification
This species is most readily identified by its large size combined with the striking contrast between its dark body and whitish head and neck. In flight, the white wing-coverts provide an unmistakable field mark, appearing as a bright panel against the otherwise dark wings. The combination of forest habitat and nocturnal habits helps distinguish it from other large waterfowl in its range. The species' preference for dense, wooded wetlands and its secretive behavior further set it apart from more conspicuous duck species.
Distribution & Habitat
Historically widespread across northeastern India, Bangladesh, Southeast Asia, Java, and Sumatra, this species has disappeared from Java and is now extinct in Malaysia. Current populations are confined to northeastern India (particularly eastern Assam and Arunachal Pradesh), Laos, Thailand, Vietnam, Cambodia, Burma, and Sumatra. The largest remaining populations are found in protected areas including Dibru-Saikhowa National Park, Dihing-Patkai Wildlife Sanctuary, Nameri National Park, and Way Kambas National Park. The species inhabits stagnant or slow-flowing natural and artificial wetlands within or adjacent to evergreen, deciduous, or swamp forests, occurring from lowlands below 200 meters up to 1,400 meters in elevation.
Behavior & Ecology
A strictly nocturnal feeder, this species emerges after dark to forage in the quiet waters of swamps, rivers, and wetlands. Its diverse diet includes seeds, aquatic plants, grains, rice, snails, small fish, and insects. The ducks depend heavily on forested wetlands for roosting and nesting, typically selecting natural tree cavities as nest sites. They are frequently observed along canal banks in plantation areas where overhanging trees provide shade, cover from predators, and secluded feeding opportunities. The species tends to remain in small groups and is known for its secretive, wary behavior.
Conservation
Classified as Endangered on the IUCN Red List, this species faces multiple severe threats including ongoing habitat loss from draining of swamps and rivers, destruction of hollow trees that provide essential nesting sites, hunting for food and egg collection, and disturbance from human activities. The population was estimated at only 800 individuals in 2002, with roughly 450 in India, Bangladesh, and Burma combined, about 200 distributed across Laos, Thailand, Vietnam, and Cambodia, and approximately 150 on Sumatra. The species is listed on CITES Appendix I, and conservation efforts include captive breeding programs and habitat protection in key areas including pulp and paper company plantations in central Sumatra that temporarily provide suitable habitat between harvests.
Culture
This duck holds the distinction of being the state bird of Assam, India, where it serves as a symbol of the region's unique and threatened wetland ecosystems. Beyond this official recognition, the species appears in limited folklore and cultural traditions among local communities in its range. Conservation efforts have received international attention, including captive breeding programs in England that have contributed to understanding the species' husbandry requirements, though these programs have faced challenges with avian tuberculosis in captive populations.
Source: Wikipedia · CC BY-SA 3.0
Taxonomy
- Order
- Anseriformes
- Family
- Anatidae
- Genus
- Asarcornis
- eBird Code
- whwduc1
Distribution
northeastern India to southeastern Asia (rare), Sumatra, and (formerly) Java
Data Sources
CBR Notes: IUCN红色名录等级由EN升为CR
Species description from Wikipedia, licensed under CC BY-SA 3.0.
Taxonomy data from AviList 2025.