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 is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds 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.

Family/Sub-family Anatidae

Species name author (Linnaeus, 1758)

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Cramp and Simmons (1977-1994), Sibley and Monroe (1990, 1993)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

180,000

unset

17,100,000 km²

No

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour This species is predominantly migratory¹ and travels over land making brief stop overs⁶. It breeds from mid-May in solitary pairs with well-defined territories¹ (non-breeders remaining in flocks separate from breeding pairs)². Adults undergo a post-breeding moult period between late-July and early-August when they become flightless for c.30 days² (5-6 weeks)⁵, males starting to moult before the females². Non-breeding individuals moult at the same time as breeders, but whilst breeding pairs tend to moult in their breeding territories non-breeders moult in large congregations². After moulting the species begins to migrate south from late-September to October (the precise timing determined by weather conditions)² and arrives on the wintering grounds by October or November³. The species departs for the breeding grounds again from March to April² or early-May³. Outside of the breeding season the species is highly sociable, migrating in small flocks or family groups³ and congregating into flocks of up to 300-400 individuals in the winter^{3, 4}. The species roosts on areas of open water adjacent to its feeding areas³. Habitat Breeding The species breeds on islands in or along the banks of shallow freshwater pools, lakes, slow-flowing rivers¹, marshes, swamps and bogs², showing a preference for habitats with abundant emergent vegetation² and reedbeds⁴ in taiga (coniferous forest) zones^{2, 4}, birch forest zones⁴ and shrub/forest tundra² (generally avoiding open tundra)^{1, 4}. Non-breeders may also be found in flocks² along sheltered coasts¹ on estuaries, lagoons and shallow bays during this season⁶. Non-breeding On migration the species frequents lakes, estuaries and sheltered coasts². It traditionally winters on freshwater lakes and marshes², floodlands⁶, brackish lagoons and coastal bays² although low-lying coastal agricultural land¹ and wet pastures⁶ are now used increasingly². Diet The species is predominantly herbivorous¹, its diet consisting of the leaves, stems and roots⁴ of aquatic plants (e.g. algae and Zostera, Ruppia and Potamogeton spp.), grasses¹, sedges and horsetails (Equisetum spp.)². During the winter the species also takes agricultural grain, vegetables (e.g. potatoes and turnips⁴) and acorns¹, and on the breeding grounds young birds often take adult and larval insects⁴ (e.g. emerging chironomids)². Adults may also supplement their diet with marine and freshwater mussels². Breeding site The nest is a large mound of plant matter¹ built on dry ground or in reedbeds⁴ on small islands in or along the edges of lakes, pools or rivers³. The same nest mound may be used over several years although it is often repaired and new material is added². Management information A study carried out at a wintering site in Denmark found that large wind turbines (towers 68 m high with blades 66 m in diameter, blades sweeping the heights of 35-101 m) pose less of a collision risk to the species than wind turbines of a medium height (towers 45 m high with blades 48 m in diameter, blades sweeping the heights of 21-69 m)¹².

Threats The species is threatened by habitat degradation and loss (such as the reclamation of coastal and inland wetlands)² especially in the Asian part of its breeding range¹. Threats to its habitats include agricultural expansion², wetland drainage for irrigation^{2, 13}, overgrazing by livestock (e.g. sheep)^{2, 13}, vegetation cutting for winter livestock feed¹³, the development of roads^{2, 13}, mining¹³ (e.g. strip mining of sediment)¹⁰, hydroelectric dam construction, disturbance from tourism¹³ and chronic oil pollution from oil exploration⁸, exploitation¹³ and transportation⁸. The species may suffer heavy losses from future oil spills⁸, flying accidents² (such as collisions with overhead lines² or wind turbines¹²), poisoning² from lead shot ingestion¹¹ and natural disasters such as droughts or heavy snowstorms¹³, and is susceptible to avian influenza, so may be threatened by future outbreaks of the disease⁷. The species is also threatened by hunting^{1, 2, 13}, nest destruction and by subsistence egg collecting^{8, 9, 13}.

References 1. del Hoyo et al. (1992). 2. Kear (2005a). 3. Madge and Burn (1988). 4. Johnsgard (1978). 5. Scott and Rose (1996). 6. Snow and Perrins (1998). 7. Melville and Shortridge (2006). 8. Nikolaeva et al. (2006). 9. Gudmundsson (1979). 10. Gardarsson (2006). 11. Spray and Milne (1988). 12. Larsen and Clausen (2002). 13. Ma and Cai (2002).

Further web sources of information

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

The Wildfowl and Wetland Trust (WWT) - Species Account

Text account compilers Stuart Butchart (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Cygnus cygnus. Downloaded from http://www.birdlife.org on 10/2/2010

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