Data Zone
Justification of Red List category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence under 20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (under 10,000 mature individuals with a continuing decline estimated to be over 10% in ten years or three generations, or with a specified population structure). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (over 30% decline over ten years or three generations). For these reasons the species is evaluated as Least Concern.
Population justification
The global population size is estimated at 90,000-340,000 individuals (Wetlands International 2023), which equates to 60,000-227,000 mature individuals. The overall population trend is suspected to be decreasing over three generations (25.89 years) (Wetlands International 2023).
Trend justification
.
Occurs throughout sub-Saharan Africa and Madagascar and from India to southern China, and south in SE Asia to Viet Nam, Thailand and Cambodia.
Behaviour This species is an intra-African migrant (Hockey et al. 2005) undertaking poorly-understood (Brown et al. 1982, del Hoyo et al. 1992, Hockey et al. 2005) seasonal movements in relation to water availability (Brown et al. 1982, del Hoyo et al. 1992). It breeds during the wet season in single pairs or small groups (Brown et al. 1982, del Hoyo et al. 1992) (harems [Brown et al. 1982]), and outside of the breeding season usually occurs in small parties of up to 30-40 individuals (Madge and Burn 1988). Large flocks also gather in the dry (non-breeding) season (Brown et al. 1982) on suitable waters (Madge and Burn 1988), but these break up and disperse to breeding grounds at the onset of the rains (Brown et al. 1982). Habitat This species inhabits grassy ponds or lakes in savanna, open woodlands along large rivers and lakes (Johnsgard 1978), swamps (del Hoyo et al. 1992), marshes, floodplains, river deltas (Brown et al. 1982, Kear 2005a), flooded forest, pastures and rice-paddies (Kear 2005a) and occasionally sandbars and mudflats (Johnsgard 1978). Diet Its diet consists largely of vegetable matter, including the seeds of grasses and sedges, the soft parts of aquatic plants (e.g. water-lilies [Brown et al. 1982]), agricultural grain (e.g. rice, corn, oats [Johnsgard 1978], wheat and groundnuts [Hockey et al. 2005]) as well as aquatic insect larvae and locusts (Johnsgard 1978, Brown et al. 1982, del Hoyo et al. 1992). Breeding site The species nests close to water (Brown et al. 1982, Madge and Burn 1988, Kear 2005a), building rough structures of twigs and coarse grass (del Hoyo et al. 1992) in large hollow tree cavities (Madge and Burn 1988, Kear 2005a), between 7 and 12 m high (Brown et al. 1982), or in holes in the walls of isolated buildings (Madge and Burn 1988) (or other cavities with a floor diameter of c.200 mm [Kear 2005a]). It may also use the abandoned nests of other bird species, such as Hamerkop Scopus umbretta (Brown et al. 1982, Madge and Burn 1988, Kear 2005a), or nest on the ground (del Hoyo et al. 1992) in the shelter of tall grass or on tree stumps (Johnsgard 1978). When the species is tree nesting, the same cavity may be used from year to year (Brown et al. 1982).
The species is threatened by hunting (del Hoyo et al. 1992) (e.g. in Madagascar [Kear 2005a]), habitat destruction (Kear 2005a) (e.g. from deforestation [del Hoyo et al. 1992]), and indiscriminate use of poison in rice-fields (del Hoyo et al. 1992). The species has declined in the Senegal Delta following the damming of the Senegal River (which has resulted in habitat degradation and loss from vegetation overgrowth, desertification processes and land conversion to agriculture [Triplett and Yesou 2000]). This species is also susceptible to avian influenza, so is potentially threatened by future outbreaks of the virus (Gaidet et al. 2007).
64-79 cm. A large, heavy and highly distinctive white and grey-black waterbird with a black speckled white head and neck. Males possess a large fleshy knob which protrudes above the bill; females lack the knob. Similar species. Comb Duck, S. sylvicola, was formerly included with the present species and differs in glossy black rather than grey flanks, differently shaped comb in males and is also smaller.
Text account compilers
Rutherford, C.A.
Recommended citation
BirdLife International (2024) Species factsheet: Knob-billed Duck Sarkidiornis melanotos. Downloaded from
https://datazone.birdlife.org/species/factsheet/knob-billed-duck-sarkidiornis-melanotos on 27/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 27/11/2024.