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 <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.
The global population is estimated to number c.625,000-750,000 individuals (Wetlands International 2015). The European population is estimated at 50,800-68,900 pairs, which equates to 102,000-138,000 mature individuals (BirdLife International 2015).
The overall population trend is increasing, although several populations have unknown trends (Wetlands International 2015). In Europe the population trend is estimated to be increasing (BirdLife International 2015).
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).
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).
Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. There are currently no known conservation measures for this species in Europe.
Conservation Actions Proposed
The following information refers to the species's European range only: Predator control at breeding sites would help this species locally and the construction of artificial caves may increase local breeding pair numbers (HELCOM 2013). Important areas for this species need to be protected. Environmental impact assessments for new tidal energy schemes should be undertaken.
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J., Malpas, L.
BirdLife International (2018) Species factsheet: Tadorna tadorna. Downloaded from http://www.birdlife.org on 15/12/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 15/12/2018.