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LC
Common Shelduck Tadorna tadorna

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 increasing, 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)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: #http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls#.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
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 global population is estimated to number c.580,000-710,000 individuals (Wetlands International 2006), while national population sizes have been estimated at c.100-10,000 breeding pairs and c.50-1,000 wintering individuals in China and c.1,000 wintering individuals in Korea (Brazil 2009).

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

Ecology
Behaviour Most populations of this species are migratory (although European populations are largely sedentary) and undertake extensive moult migrations to favoured moulting sites after breeding (del Hoyo et al. 1992) (Asiatic breeding populations may also moult near their breeding grounds) (Kear 2005a). The species breeds in single pairs or small groups (Flint et al. 1984, del Hoyo et al. 1992), non-breeders usually remaining in flocks throughout the year (Kear 2005a). After breeding (between July and October) the species moults and becomes flightless for 25-31 days (Kear 2005a), during which it is highly gregarious (Madge and Burn 1988) and may aggregate into large flocks of up to 100,000 individuals or more (del Hoyo et al. 1992, Kear 2005a). Habitat The species shows a preference for saline habitats and frequents mudflats (del Hoyo et al. 1992) and muddy or sandy (Madge and Burn 1988) estuaries (Madge and Burn 1988, del Hoyo et al. 1992) in coastal regions, and occurs inland on saline and brackish lakes in steppe or semi-desert (Madge and Burn 1988). Asiatic populations also occupy freshwater rivers or marshes (Kear 2005a) and other populations utilise freshwater habitats on migration (Flint et al. 1984). Diet Its diet consists predominantly of salt-water molluscs (e.g. Hydrobia spp.) as well as other aquatic invertebrates (e.g. insects, crustaceans and worms), small fish, fish spawn and plant material (del Hoyo et al. 1992) (e.g. algae, seeds and agricultural grain) (Kear 2005a). Breeding site The nest is commonly positioned in a tree-hollow (del Hoyo et al. 1992) up to 8 m above the ground (Kear 2005a) or in a mammal burrow (e.g. of European rabbit Oryctolagus cuniculus) (del Hoyo et al. 1992, Kear 2005a). Rarely nests may also be placed in the open or in dense vegetation up to 1 km from water (Madge and Burn 1988, Kear 2005a). The species will also nest in artificial nest-boxes (Kear 2005a). Management information Studies in Danish coastal wetlands found that the spatial restriction of shore-based shooting was more successful at maintaining waterfowl population sizes than was the temporal restriction of shooting, and therefore that wildfowl reserves should incorporate shooting-free refuges that include adjacent marshland in order to ensure high waterfowl species diversity (Bregnballe et al. 2004). In the outer archipelago of south-west Finland experimental removal (extermination) of the nest predator American mink Neovison vison resulted in an increase in the breeding density of this species (Nordstrom et al. 2002).

Threats
The species is threatened by habitat loss as a result of tidal barrage schemes in Europe (Kear 2005a, Burton 2006). It also suffers predation from American mink Neovison vison on islands (Nordstrom et al. 2002) and is susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006). Utilisation The species is hunted for commercial and recreational purposes in Iran (Balmaki and Barati 2006), and its eggs used to be (and possibly still are) harvested in Iceland (Gudmundsson 1979).

Related state of the world's birds case studies

References
Balmaki, B.; Barati, A. 2006. Harvesting status of migratory waterfowl in northern Iran: a case study from Gilan Province. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 868-869. The Stationary Office, Edinburgh, UK.

Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

Bregnballe, T.; Madsen, J., Rasmussen, P. A. F. 2004. Effects of temporal and spatial hunting control in waterbird reserves. Biological Conservation 119: 93-104.

Burton, N. H. K. 2006. The impact of the Cardiff Bay barrage on wintering waterbirds. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), aterbirds around the world, pp. 805. The Stationary Office, Edinburgh, UK.

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.

Flint, V. E.; Boehme, R. L.; Kostin, Y. V.; Kuznetsov, A. A. 1984. A field guide to birds of the USSR. Princeton University Press, Princeton, New Jersey.

Gudmundsson, F. 1979. The past status and exploitation of the Myvatn waterfowl populations. Oikos 32((1-2)): 232-249.

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

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

Melville, D. S.; Shortridge, K. F. 2006. Migratory waterbirds and avian influenza in the East Asian-Australasian Flyway with particular reference to the 2003-2004 H5N1 outbreak. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 432-438. The Stationary Office, Edinburgh, UK.

Nordström, M.; Högmander, J.; Nummelin, J.; Laine, J.; Laanetu, N.; Korpimäki, E. 2002. Variable responses of waterfowl breeding populations to long-term removal of introduced American mink. Ecography 25: 385-394.

Vahatalo, A. V.; Rainio, K.; Lehikoinen, A.; Lehikoinen, E. 2004. Spring arrival of birds depends on the North Atlantic Oscillation. Journal of Avian Biology 35: 210-216.

Further web sources of information
Detailed species account from Birds in Europe: population estimates trends and conservation status (BirdLife International 2004)

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

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

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

Recommended citation
BirdLife International (2014) Species factsheet: Tadorna tadorna. Downloaded from http://www.birdlife.org on 21/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/08/2014.

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.

Additional resources for this species

ARKive species - Common shelduck (Tadorna tadorna) 0

Key facts
Current IUCN Red List category Least Concern
Family Anatidae (Ducks, Geese, Swans)
Species name author (Linnaeus, 1758)
Population size mature individuals
Population trend Increasing
Distribution size (breeding/resident) 2,200,000 km2
Country endemic? No
Links to further information
- Additional Information on this species