White-winged Duck (Asarcornis scutulata)

[order] ANSERIFORMES | [family] Anatidae | [latin] Asarcornis scutulata | [authority] S. Muller, 1842 | [UK] White-winged Duck | [FR] Canard a ailes blanches | [DE] Weissflugel-Moschusente | [ES] Pato de Jungla | [NL] Witvleugelboseend

Subspecies

Genus

Physical charateristics

Large, dark, forest duck with contrasting whitish head and upper neck. Males have mostly dull yellowish bill, blackish mottling on head and upper neck, white lesser and median coverts and inner edges of tertials and bluish-grey secondaries. In flight, white wing-coverts contrast with the rest of the wings. Females are smaller and usually have more densely mottled head and upper neck. Juvenile is duller and browner.

Range

Oriental Region : Southeast Asia, Sumatra. Cairina scutulata was historically widely distributed from north-east India and Bangladesh, through South-East Asia to Java and Sumatra, Indonesia. It has undergone a dramatic decline such that, its population is now estimated at c.1,000 individuals, comprising 200 in Laos, Thailand, Vietnam and Cambodia, 150 on Sumatra, Indonesia, 450 in India (chiefly Assam and Arunachal Pradesh) and Bangladesh and in the “low hundreds” in Myanmar following the identification of a significant population numbering tens of individuals in the proposed Hukuang Tiger Reserve.

Habitat

It inhabits stagnant or slow-flowing natural and artificial wetlands, within or adjacent to evergreen, deciduous or swamp forests, on which it depends for roosting and nesting, usually in tree-holes. Although lowlands (below c.200 m) provide optimum habitat, it occurs up to 1,400 m, especially on plateaux supporting sluggish perennial rivers and pools

Reproduction

Breeding generally seems synchronised with seasonal rainfall such that laying occurs in the late dry season and hatching occurs in the early wet season, which, in the north of the species?s range, begins in May. In India, breeding activity starts in February/March and lasts until the end of July. The White-winged Duck usually nests in tree holes, forks and hollows. The tree species used vary with availability and nest cavities have been recorded 3?12 m from the ground. Four of the six nests found were in tree cavities, while the others were on the ground, one of the latter underneath a fallen tree-trunk at the water?s edge. Clutch and brood sizes in India range from one to 15. Broods recorded in Thailand were much smaller, containing an average of five young (range 3?7). The observation of more than two birds with ducklings might indicate either post-fledging brood-merging in the species, multiple clutches laid in single nest cavities (which seems possible given the large brood sizes recorded) or that helpers assist the breeding pair. Indeed broods at Way Kambas were watched being accompanied by helpers and even individually by different females at different times. The female incubates overnight, while the male roosts nearby and approaches at dawn to escort he to foraging grounds for the first few hours of the day; he then accompanies her back to the nest and returns to his roost until late afternoon, when he again visits and accompanies her on a foraging trip, the birds returning to their original positions for the night towards dusk. When the male returns to the nest with the female (i.e. late morning and dusk) he perches in the nest tree for a while or flies about nearby until she is settled, a behaviour which helps in the detection of nests. Although ducklings have occasionally been observed with both parents, they are more usually accompanied by a single parent, presumably the female.

Feeding habits

The species feeds in wet grass areas and shallow pools, shallow, stagnant or slow-flowing streams, ponds, swamps or ricefields. Its diet includes seeds, vegetation, fish and other animal matter. In
Bangladesh, it has been observed foraging mainly on aquatic snails (Vibira sp.), but also on
vegetation (specifically Hydrila), fish (c.15 species), spiders and insects; and it is clear that birds will exploit local abundances of particular foods, whether animal or vegetable.

Video White-winged Duck

httpv://www.youtube.com/watch?v=JHZDaIjDXzQ

copyright: puiparinya

Conservation

This forest duck is listed as Endangered because it has a very small and fragmented population which is undergoing a very rapid and continuing decline as a result of loss of and disturbance to riverine habitats.
Its decline is largely attributable to the destruction, degradation and disturbance of riverine habitats including loss of riparian forest corridors. The resultant small, fragmented populations are vulnerable to extinction from stochastic environmental events, loss of genetic variability, disturbance, hunting and collection of eggs and chicks for food or pets. Hydro-power development, inappropriate forest management, and pollution are more localised threats. It may be particularly susceptible to loss of large trees with nesting holes

Migration

The species is presumably resident, although short movements in response to
dry weather and water conditions are frequently recorded: the drying of small upland
watercourses tends to result in an increase of records from larger watercourses in the nearby
lowlands

Distribution map