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LC
Yellow-billed Duck Anas undulata

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.

Taxonomic source(s)
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Trend justification
The overall population trend is stable, although some populations have unknown trends (Wetlands International 2006).

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).

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).

References
Blaker, D. 1967. An outbreak of Botulinus poisoning among waterbirds. Ostrich 38(2): 144-147.

Brown, L. H.; Urban, E. K.; Newman, K. 1982. The birds of Africa vol I. Academic Press, London.

Dean, W. R. J.; Skead, D. M. 1989. Survival and recovery rates of Yellow-Billed Ducks. Journal of Wildlife Management 53(1): 119-122.

del Hoyo, J.; Elliot, A.; Sargatal, J. 1992. Handbook of the Birds of the World, vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain.

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Hockey, P. A. R.; Dean, W. R. J.; Ryan, P. G. 2005. Roberts birds of southern Africa. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa.

Johnsgard, P. A. 1978. Ducks, geese and swans of the World. University of Nebraska Press, Lincoln and London.

Kear, J. 2005. Ducks, geese and swans volume 2: species accounts (Cairina to Mergus). Oxford University Press, Oxford, U.K.

Little, R. M.; Vester, K. C.; Crowe, T. M. 1995. Temporal and spatial paterns of breeding activity of 12 duck species (Anatidae) in the cape provinces, South-Africa, and their implications for hunting seasons. South African Journal of Wildlife Research 25(1): 17-22.

Nikolaus, G. 2001. Bird exploitation for traditional medicine in Nigeria. Malimbus 23: 45-55.

Owen, M.; Callaghan, D.; Kirby, J. 2006. Guidelines on Avoidance of Introductions of Non-native Waterbird Species. Bonn, Germany.

Scott, D. A.; Rose, P. M. 1996. Atlas of Anatidae populations in Africa and western Eurasia. Wetlands International, Wageningen, Netherlands.

Further web sources of information
Explore HBW Alive for further information on this species

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Butchart, S., Ekstrom, J., Malpas, L.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Anas undulata. Downloaded from http://www.birdlife.org on 28/12/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/12/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Least Concern
Family Anatidae (Ducks, Geese, Swans)
Species name author Dubois, 1839
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 8,460,000 km2
Country endemic? No
Links to further information
- Additional Information on this species
- Projected distributions under climate change