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White-backed Duck Thalassornis leuconotus

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). 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 (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to 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.

Population justification
The population is estimated to number 12,000-28,000 individuals, roughly equating to 8,000-19,000 mature individuals.

Trend justification
The overall trend is decreasing, although some populations may be stable (Wetlands International 2006).

Ecology
Behaviour This species is partially migratory (Scott and Rose 1996) or semi-nomadic (Kear 2005a), making local dispersive movements during the rainy season (Brown et al. 1982, Madge and Burn 1988) to take advantage of temporary wetlands (Madge and Burn 1988, del Hoyo et al. 1992). The timing of breeding varies geographically although it generally coincides with periods of higher or more stable water levels (del Hoyo et al. 1992). The species breeds in solitary pairs or loose groups (del Hoyo et al. 1992), dispersing after breeding (as water levels drop) to gather in small flocks (Kear 2005a) of 20 to 100 individuals (Brown et al. 1982) on more permanent lakes and marshes (Kear 2005a). The species is crepuscular (Kear 2005a) and obtains its food almost solely by diving (Brown et al. 1982). Habitat The species inhabits quiet shallow freshwater lakes, pools, lagoons (del Hoyo et al. 1992), pans, inland deltas (Brown et al. 1982), flood-plains (Madge and Burn 1988), marshes and swamps (del Hoyo et al. 1992) fringed with abundant emergent and floating vegetation (Brown et al. 1982, del Hoyo et al. 1992) (e.g. reeds, papyrus and water-lilies Nymphaea spp.) (Kear 2005a), generally avoiding very open water (del Hoyo et al. 1992). It also often inhabits forested lakes in Madagascar (Kear 2005a) and may frequent farm impoundments or stock-ponds in other areas (Scott and Rose 1996). Diet Although the species is predominantly herbivorous (taking the seeds and leaves of aquatic plants such as water-lilies Nymphaea spp. and Polygonum spp.) the young may feed on Chironomid insect larvae (del Hoyo et al. 1992). Breeding site The nest is constructed of vegetation either floating on or up to 45 cm above water (Brown et al. 1982) amongst reedbeds (Brown et al. 1982, del Hoyo et al. 1992) or papyrus beds (Brown et al. 1982), or on the ground in waterside vegetation on small islands (Brown et al. 1982, del Hoyo et al. 1992). The species will occasionally use the abandoned nests of grebes or coots as nest bases (Brown et al. 1982, Madge and Burn 1988).

Threats
The species is threatened by the modification of wetlands especially where the native aquatic flora is affected, e.g. through the introduction of herbivorous fish (Kear 2005a), the introduction of exotic plants, deterioration in water quality as a result of deforestation and soil erosion in catchment areas (Scott and Rose 1996), and pollution (Kear 2005a). The species has also declined in Madagascar due to hunting and trapping (Langrand 1990, del Hoyo et al. 1992), and its large eggs are especially prized as food by people living near wetlands (Kear 2005a).

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

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.

Kear, J. 2005. Ducks, geese and swans volume 1: general chapters; species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, U.K.

Langrand, O. 1990. Guide to the birds of Madagascar. Yale University Press, New Haven, USA.

Madge, S.; Burn, H. 1988. Wildfowl. Christopher Helm, London.

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

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

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

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

Recommended citation
BirdLife International (2014) Species factsheet: Thalassornis leuconotus. Downloaded from http://www.birdlife.org on 18/12/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 18/12/2014.

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 Eyton, 1838
Population size 8000-19000 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 10,000,000 km2
Country endemic? No
Links to further information
- Additional Information on this species
- Projected distributions under climate change