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 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.
The global population is estimated to number > c.180,000 individuals (Wetlands International 2015). The population in Russia has been estimated at c.10,000-100,000 breeding pairs and c.1,000-10,000 wintering individuals (Brazil 2009). The European population is estimated at 25,300-32,800 pairs, which equates to 50,600-65,500 mature individuals (BirdLife International 2015).
The overall population trend is uncertain, as some populations are decreasing, while others are increasing, stable or have unknown trends (Wetlands International 2006). In Europe the population size is estimated to be increasing (BirdLife International 2015).
Behaviour This species is predominantly migratory (del Hoyo et al. 1992) and travels over land making brief stop overs (Snow and Perrins 1998). It breeds from mid-May in solitary pairs with well-defined territories (del Hoyo et al. 1992) (non-breeders remaining in flocks separate from breeding pairs) (Kear 2005a). Adults undergo a post-breeding moult period between late-July and early-August when they become flightless for c.30 days (Kear 2005a) (5-6 weeks) (Scott and Rose 1996), males starting to moult before the females (Kear 2005a). 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 congregations (Kear 2005a). After moulting the species begins to migrate south from late-September to October (the precise timing determined by weather conditions) (Kear 2005a) and arrives on the wintering grounds by October or November (Madge and Burn 1988). The species departs for the breeding grounds again from March to April (Kear 2005a) or early-May (Madge and Burn 1988). Outside of the breeding season the species is highly sociable, migrating in small flocks or family groups (Madge and Burn 1988) and congregating into flocks of up to 300-400 individuals in the winter (Johnsgard 1978, Madge and Burn 1988). The species roosts on areas of open water adjacent to its feeding areas (Madge and Burn 1988). Habitat Breeding The species breeds on islands in or along the banks of shallow freshwater pools, lakes, slow-flowing rivers (del Hoyo et al. 1992), marshes, swamps and bogs (Kear 2005a), showing a preference for habitats with abundant emergent vegetation (Kear 2005a) and reedbeds (Johnsgard 1978) in taiga (coniferous forest) zones (Johnsgard 1978, Kear 2005a), birch forest zones (Johnsgard 1978) and shrub/forest tundra (Kear 2005a) (generally avoiding open tundra) (Johnsgard 1978, del Hoyo et al. 1992). Non-breeders may also be found in flocks (Kear 2005a) along sheltered coasts (del Hoyo et al. 1992) on estuaries, lagoons and shallow bays during this season (Snow and Perrins 1998). Non-breeding On migration the species frequents lakes, estuaries and sheltered coasts (Kear 2005a). It traditionally winters on freshwater lakes and marshes (Kear 2005a), floodlands (Snow and Perrins 1998), brackish lagoons and coastal bays (Kear 2005a) although low-lying coastal agricultural land (del Hoyo et al. 1992) and wet pastures (Snow and Perrins 1998) are now used increasingly (Kear 2005a). Diet The species is predominantly herbivorous (del Hoyo et al. 1992), its diet consisting of the leaves, stems and roots (Johnsgard 1978) of aquatic plants (e.g. algae and Zostera, Ruppia and Potamogeton spp.), grasses (del Hoyo et al. 1992), sedges and horsetails (Equisetum spp.) (Kear 2005a). During the winter the species also takes agricultural grain, vegetables (e.g. potatoes and turnips (Johnsgard 1978)) and acorns (del Hoyo et al. 1992), and on the breeding grounds young birds often take adult and larval insects (Johnsgard 1978) (e.g. emerging chironomids) (Kear 2005a). Adults may also supplement their diet with marine and freshwater mussels (Kear 2005a). Breeding site The nest is a large mound of plant matter (del Hoyo et al. 1992) built on dry ground or in reedbeds (Johnsgard 1978) on small islands in or along the edges of lakes, pools or rivers (Madge and Burn 1988). The same nest mound may be used over several years although it is often repaired and new material is added (Kear 2005a). 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) (Larsen and Clausen 2002).
The species is threatened by habitat degradation and loss (such as the reclamation of coastal and inland wetlands) (Kear 2005a) especially in the Asian part of its breeding range (del Hoyo et al. 1992). Threats to its habitats include agricultural expansion (Kear 2005a), wetland drainage for irrigation (Ma and Cai 2002, Kear 2005a), overgrazing by livestock (e.g. sheep) (Ma and Cai 2002, Kear 2005a), vegetation cutting for winter livestock feed (Ma and Cai 2002), the development of roads (Ma and Cai 2002, Kear 2005a), mining (Ma and Cai 2002) (e.g. strip mining of sediment) (Gardarsson 2006), hydroelectric dam construction, disturbance from tourism (Ma and Cai 2002) and chronic oil pollution from oil exploration (Nikolaeva et al. 2006), exploitation (Ma and Cai 2002) and transportation (Nikolaeva et al. 2006). The species may suffer heavy losses from future oil spills (Nikolaeva et al. 2006), flying accidents (Kear 2005a) (such as collisions with overhead lines (Kear 2005a) or wind turbines (Larsen and Clausen 2002)), poisoning (Kear 2005a) from lead shot ingestion (Spray and Milne 1988) and natural disasters such as droughts or heavy snowstorms (Ma and Cai 2002), and is susceptible to avian influenza, so may be threatened by future outbreaks of the disease (Melville and Shortridge 2006). The species is also threatened by hunting (del Hoyo et al. 1992, Ma and Cai 2002, Kear 2005a), nest destruction and by subsistence egg collecting (Gudmundsson 1979, Ma and Cai 2002, Nikolaeva et al. 2006).
Conservation Actions Underway
Bern Convention Appendix II. EU Birds Directive Annex I. CMS Appendix II. In the U.K., the species is listed as Amber on the national Red List (Eaton et al. 2009).
Conservation Actions Proposed
Key sites should be identified and protected by legislation against all forms of development and habitat alteration. Strict legislation should also be enforced with regards to oil drilling and transportation. Power lines should be made more visible or moved and careful assessment made during planning of wind farm construction. Protection from hunting and persecution should also be implemented and enforced.
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J., Malpas, L.
BirdLife International (2021) Species factsheet: Cygnus cygnus. Downloaded from http://www.birdlife.org on 20/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/10/2021.