Physical Description

Diagnostic Description

Description

Length: 51-63 cm. Plumage: dark brownish grey with broad paler edging to feathers giving scaley appearance; head darker with less scaling; speculum green (blue in the nothern race rueppelli) narrowly edged white, wing linings white. Immature like adult but paler. Bare parts: iris reddish brown; bill bright yellow with a black central patch on culmen; feet and legs black to reddish brown. Habitat: estuaries, but more common on inland waters. <388><391><393>
  • Brown, L.H., E.K. Urban & K. Newman (1982). The Birds of Africa, Volume I. Academic Press, London.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Behaviour This species is mainly sedentary, although the southern African population is more nomadic, undertaking considerable local movements (up to 50 km (Brown, et al. 1982)) with the availability of seasonal wetlands (Brown, et al. 1982, Scott and Rose 1996). It forms huge colonies in the non-breeding season, but disperses to breed at the onset of the rainy season (Brown, et al. 1982). Adults undergo a post-nuptial wing moult three or four months after the peak of the breeding season, rendering them flightless for a period of about four weeks (Johnsgard 1978, Kear 2005b). The species is mainly nocturnal: typically foraging at dusk and after dark whilst remaining sedentary throughout the day (Johnsgard 1978). Habitat This species frequents slow-flowing rivers with pools and adjacent flooded grasslands, permanent and seasonal lakes, streams, marshes, brackish coastal lagoons, artificial reservoirs associated with mining, dams, salt pans, sewage works and the open water of estuaries (del Hoyo, et al. 1992, Hockey, et al. 2005, Kear 2005b). It cannot tolerate highly acidic habitats or those where sodium chloride concentrations are very high, but can tolerate high concentrations of other salts around pH 10 or more (Brown, et al. 1982). It also avoids fast-flowing water (Hockey, et al. 2005). Diet It is omnivorous, with a diet consisting of the fruits, seeds, roots, leaves and stems of aquatic and terrestrial plants, aquatic insects and their larvae (including mayflies, water beetles and grasshoppers) (Hockey, et al. 2005), crustaceans, molluscs and agricultural grains such as maize and sunflower seeds (Brown, et al. 1982, del Hoyo, et al. 1992). Breeding site The nest of this species is situated on the ground and is made of grass, rushes and reed stems (Brown, et al. 1982, del Hoyo, et al. 1992). It is usually protected and screened from above by dense, overhanging vegetation (del Hoyo, et al. 1992) and some nests may have tunnel access through the surrounding grass (Brown, et al. 1982).

Systems
  • Terrestrial
  • Freshwater
  • Marine
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <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 trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
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Population

Population Trend
Stable
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Threats

Major Threats
Pollution is a threat that still needs to be controlled within the species's range to keep the current population stable (Kear 2005b). Hybridisation of the species with the Northern Mallard Anas platyrhynchos represents a threat to the integrity of the species (Hockey, et al. 2005, Kear 2005b, Owen, et al. 2006) because the two species hybridise easily and produce fertile progeny (Owen, et al. 2006). Northern Mallard Anas platyrhynchos was introduced both deliberately and accidentally into the Cape Provinces of South Africa and has since become naturalised (Owen, et al. 2006). Other exotic ducks may associate with the species (e.g. Laysan Teal at Gauteng Province) and these species pose a further potential threat (Owen, et al. 2006). The species is also susceptible to avian botulism, so may be threatened by future outbreaks of the disease (Blaker 1967). Utilisation The species is hunted (Dean and Skead 1989, Little, et al. 1995, Kear 2005b), and although there is no current evidence that such activities pose a threat to the species (Dean and Skead 1989), hunting levels may still need to be controlled in order to maintain current population levels (Kear 2005b). The species is also traded at traditional medicine markets in Nigeria (Nikolaus 2001).
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Wikipedia

Yellow-billed Duck

Swimming at Plettenberg Bay, South Africa

The Yellow-billed Duck (Anas undulata) is a 51–58 cm long dabbling duck which is an abundant resident breeder in southern and eastern Africa.

This duck is not migratory, but will wander in the dry season to find suitable waters. It is highly gregarious outside the breeding season and forms large flocks.

These are Mallard-sized mainly grey ducks with a darker head and bright yellow bill. The wings are whitish below, and from above show a white-bordered green speculum.

Sexes are similar, and juveniles are slightly duller than adults. The north-eastern race is darker and has a brighter bill and blue speculum.

It is a bird of freshwater habitats in fairly open country and feeds by dabbling for plant food mainly in the evening or at night. It nests on the ground in dense vegetation near water. The clutch numbers between six and twelve eggs.

The male has a Teal-like whistle, whereas the female has a Mallard-like quack.

There are two subspecies of the Yellow-billed Duck: A. undulata rueppelli (Northern Yellow-billed Duck) A. undulata undulata (Southern Yellow-billed Duck)

The Yellow-billed Duck is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies. The southern nominate subspecies is declining due to competition and hybridization with feral Mallards (Rhymer 2006).

References[edit]

  • Rhymer, Judith M. (2006): Extinction by hybridization and introgression in anatine ducks. Acta Zoologica Sinica 52(Supplement): 583–585. PDF fulltext
  • Ian Sinclair, Phil Hockey and Warwick Tarboton, SASOL Birds of Southern Africa (Struik 2002) ISBN 1-86872-721-1
  • Madge and Burn, Wildfowl ISBN 0-7470-2201-1
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