Other names : Knob-billed Duck
French name : Canard casqué
Size : 56-76cm. Female considerably smaller than male.
At rest : Unmistakable. Large, heavily-built duck of tropical wetlands, with distinctive two-toned pattern of white head, neck and underparts and glossy black upperparts; at close quarters, dark freckling often visible on head. Male has large fleshy knob at base of bill.
In flight : white of head, neck and underbody contrasts sharply with black underwing and upperparts, although paler rump may be obvious at certain angles.
Lowland tropical swamps, lakes and rivers in open, sparsely-wooded country.
Breeds singly or in groups (harems), usually in tree cavities; the same cavity may be used from year to year. Breeding occurs when climate hot in areas of relatively high rainfall, though this may be unevenly distributed annually, seasonally and locally. Non-breeding frequent in years of poor rainfall.
Widespread throughout tropical Africa, tropical Asia and South America. In Africa it is both resident and a seasonal migrant throughout the continent and Madagascar, avoiding arid and densely-forested regions.
Its movements are not clearly understood apart from being linked with drying-out of wetlands during the dry season, but ringing recoveries indicate that some movements are very extensive (e.g. birds ringed in Zimbabwe recovered in Sudan and Chad).
Three populations are recognised in Africa: one in West Africa, with an estimate of 50,000-80,000 birds, declining; one in Southern and Eastern Africa, with an estimate of 100,000-500,000, stable; and one in Madagascar with an estimate of 25,000-100,000, declining.
January 12th, 2010
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