Knob-billed Duck

Sarkidiornis melanotos

Wetlands. Iridescent blue above; white below; head speckled black.

Ducks, Geese

Not Endemic

Description

Uncommon to locally common resident. Male much larger than female; distinguished by glossy dark blue upper parts, white underparts, black-speckled head and neck (washed yellow when breeding) and a large fleshy caruncle on forehead and bill. Female duller and lacking caruncle. Immature quite different from adult. In first year (a) has dark brown upper parts, pale buff underparts and distinct eye-stripe; sub-adult (b) is more like female but underparts orange-buff, with heavier spotting on head and neck. Mostly silent. Flocks, often large in the dry season, frequent marshes, temporary bushveld pans, floodplains and estuaries. Often perches in dead trees.

Quick Facts

Bird Family

Most of the region's ducks are either migratory to some extent or locally nomadic, their movements being dictated by food, rainfall and breeding requirements. Many show marked plumage differences between the sexes. Ducks and geese undergo a flightless four-to-eight-week period each year when they moult all their flight feathers simultaneously. The large Spur-winged and Egyptian Geese differ from geese of the northern hemisphere in having longer bills and legs, the African Pygmy-Goose being our only representative of the ‘true' geese. Ducks of the genus *Dendrocygna* (whistling ducks), which include the White-faced and Fulvous whistling ducks, differ from those of other genera in having close-set legs placed well back on the body. This enables them to stand erect and walk without waddling. In addition they show no sexual dimorphism and have whistling voices. In contrast, ducks of the genus *Anas*, often referred to as dabbling ducks, have widely spaced legs placed centrally on the body. This causes them to stand with the body horizontally and to walk with a waddle. They are further typified by quacking voices.