Gadwall

The gadwall is a medium dabbling duck 47–58 cm long with a 78–85 cm wingspan. Breeding males are intricately patterned grey with a black rear, chestnut wing coverts and brilliant white speculum; females are mottled brown but differ from female mallards through a smaller dark-edged orange bill and the same white wing patch. The restrained plumage and quiet calls can make resting birds easy to overlook (Wikipedia, general species account).

Widespread across temperate Eurasia and North America, it winters south into subtropical regions and occurs in Vietnam as a visitor. Gadwalls use shallow lakes, marshes, reservoirs and sheltered coastal wetlands, dabbling for leaves, stems and seeds of aquatic plants and taking some invertebrates. They also steal vegetation brought up by diving birds. Females conceal nests in dense ground cover and incubate seven to twelve eggs for about 24–27 days (Wikipedia, general species account).