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Knob-Billed Duck | Sarkidiornis melanotos
Knobbeleend | Pato crestudo afroasiático
The Knob-billed Duck is a large, black-and-white duck of tropical swamps in Africa and southern Asia, the male of which bears a large black knob on top of the bill. Within the region it is an extremely rare vagrant, known only from Dhofar in southern Oman.
Voice
Largely silent. In the breeding season and when disturbed a soft, low hissing and grunting; on taking off a hoarse krrrk.
Recording: vir joshi — CC BY-NC-SA 3.0 · converted to mono · xeno-canto
Identification
56–76 cm; the male is much larger than the female. The head and neck are white, densely speckled black, the underparts white, with a black stripe along the side of the breast in the male. The back and wings are black with a strong blue-green and bronze gloss. The male has an erect black knob on the bill that swells greatly in the breeding season; the female lacks the knob and is duller. In flight wholly dark, glossy wings without white, against a white belly.
Confusion species
No real confusion in the region. In flight the black and white can recall a Common Shelduck (Tadorna tadorna), but that has white wing coverts and a chestnut breast band. Escaped or feral domestic Muscovy Ducks (Cairina moschata) can be black and white, but have red bare skin around the bill and white wing patches.
Habitat
Freshwater swamps, flooded grasslands, rice fields and temporary pools in wooded savanna, with dead trees for perching and nesting. In Oman it has been seen at a reed-fringed coastal lagoon (khawr) and on a farm with water reservoirs.
Where the bird is most at home, classified by the habitats of North Africa and the Middle East.
Range and movements
An extremely rare vagrant in Oman: in Dhofar at Razat Farm in August 1990 and November 1996, and a single bird that stayed at the East Khawr coastal lagoon near Salalah from late September to mid-November 2024. Its origin, Africa or southern Asia, is uncertain. Beyond the region throughout almost all of sub-Saharan Africa, on Madagascar and in southern and south-east Asia from Pakistan to Myanmar; the South American Comb Duck is now treated as a separate species.
How and when to look
A vagrant in Dhofar is most likely after the summer monsoon, when the lagoons around Salalah are full; check the duck flocks and the dead trees along the reed fringe there in autumn.
Conservation status
Not threatened and widespread in Africa, but declining locally in Asia through wetland drainage and hunting. In Africa it makes large nomadic movements after the rains, which explains the appearance of vagrants far outside its range.
Scientific name
Sarkidiornis melanotos | (Pennant, 1769)
Pennant described the species in 1769 as Anser melanotos; because it was later moved to another genus, the author and year stand in brackets. The genus Sarkidiornis was introduced in 1838 by Eyton. Sarkidiornis comes from the Greek sarkidion, 'small piece of flesh', and ornis, 'bird' — for the fleshy knob on the male's bill. melanotos is from Greek melas, 'black', and notos, 'back', so 'black-backed', for the glossy black upperparts. The specimen the first description was based on came from Sri Lanka.