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 317,000-336,000 individuals (Wetlands International 2016). The breeding population in Europe is estimated at 5,000-6,000 pairs, which equates to 10,000-12,000 mature individuals (BirdLife International 2015). National population sizes have been estimated at c.50-10,000 wintering individuals in China and c.100-10,000 breeding pairs in Russia (Brazil 2009).
The overall population trend is uncertain, as some populations are decreasing, while others are increasing, stable or have unknown trends (Wetlands International 2016). This species has undergone a small or statistically insignificant decrease over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). In Europe the breeding and wintering population is estimated and projected to be decreasing by 50-79% between 2000, when declines are estimated to have begun, and 2038 (three generations) (BirdLife International 2015).
Behaviour This species is fully migratory and travels on a narrow front via specific routes using well-known stop-over sites (Madge and Burn 1988) between its Arctic breeding and temperate wintering grounds (del Hoyo et al. 1992). It arrives on the breeding grounds from early-May to late-June (Madge and Burn 1988) (depending on local conditions [Kear 2005a]) where it breeds well-dispersed (Snow and Perrins 1998) in single pairs (del Hoyo et al. 1992), occasionally nesting semi-colonially in optimum habitats (Madge and Burn 1988, Kear 2005a). After breeding the species undergoes a flightless moulting period lasting for c.30 days between late-June and early-September, gathering in flocks on open waters (Madge and Burn 1988, Scott and Rose 1996). Family groups leave the breeding grounds from early-September to late-October (Madge and Burn 1988) and arrive on the wintering grounds from mid-October onwards (Madge and Burn 1988). During this autumn migration some groups may remain at stop-over sites until moved on by cold weather (Madge and Burn 1988). The return northward migration occurs from early-March, with the species travelling in small parties that disperse on arrival in the Arctic (Madge and Burn 1988). The species is gregarious outside of the breeding season, often gathering into large flocks of hundreds or thousands of individuals on the wintering grounds (Madge and Burn 1988, Kear 2005a). The species forages by day (where undisturbed [del Hoyo et al. 1992]) and roosts at night on open water (Kear 2005a). Habitat Breeding The species breeds near shallow pools, lakes (del Hoyo et al. 1992) and broad slow-flowing rivers (del Hoyo et al. 1992, Kear 2005a) with emergent littoral vegetation and pondweeds (e.g. Potamogeton spp.) connected to coastal delta areas (Kear 2005a) in open, moist, low-lying sedge-grass or moss-lichen (Kear 2005a) Arctic tundra (del Hoyo et al. 1992). It rarely nests in shrub tundra, and generally avoids forested areas (Kear 2005a). Non-breeding On migration the species frequents shallow ponds (Kear 2005a), lowland and upland lakes (Madge and Burn 1988, Kear 2005a), reservoirs (Madge and Burn 1988), riverine marshes, shallow saline lagoons (Kear 2005a) and sheltered coastal bays and estuaries (Madge and Burn 1988). During the winter it inhabits brackish and freshwater marshes (Madge and Burn 1988), rivers, lakes, ponds (Kear 2005a) and shallow tidal estuarine areas (del Hoyo et al. 1992, Kear 2005a) with adjacent grasslands (del Hoyo et al. 1992), flooded pastures (Kear 2005a) or agricultural arable fields (del Hoyo et al. 1992, Kear 2005a) below 100 m (Snow and Perrins 1998). Diet The species is predominantly herbivorous (del Hoyo et al. 1992), its diet consisting of the seeds, fruits, leaves, roots, rhizomes and stems of aquatic plants (e.g. Potamogeton, Zostera and Glyceria spp.), grasses (del Hoyo et al. 1992), sedges, reeds (Phragmites and Typha spp. [Kear 2005a]) and herbaceous tundra vegetation (Kear 2005a). During the winter the species complements its diet with agricultural grain and vegetables (del Hoyo et al. 1992) (e.g. potatoes [del Hoyo et al. 1992] and sugar beet [Kear 2005a]), and may also take estuarine invertebrates such as molluscs, amphipods (e.g. Corophium spp.) and polycheate worms on tidal mudflats prior to migration (Kear 2005a). Breeding site The nest is a large mound of plant matter positioned on elevated ground (del Hoyo et al. 1992) such as a ridge or hummock, often at some distance from feeding pools to reduce to the risk of flooding (Kear 2005a). The species may re-use a nest from the previous year or build a new one, and although it is not colonial, many pairs may nest close together in optimum habitats (e.g. 5-16 pairs per 10 km2 [Kear 2005a]). Management information An experiment carried out in the Sacramento National Wildlife Refuge, California found that in wetland habitats where clay hardpans underlie wetland sediments tilling (plowing) the soil may be an effective means of reducing lead shot availability to waterfowl (Thomas et al. 2001). Plowing was found to reduce the amount of shot available to depths of 20-30 cm (below the foraging zone of the species [Thomas et al. 2001]).
The species is threatened by the degradation and loss of wetland habitats due to drainage (Kear 2005) (e.g. for agriculture [Grishanov 2006]), petroleum pollution, peat-extraction, changing wetland management practices (e.g. decreased grazing and mowing in meadows leading to scrub over-growth), the burning and mowing of reeds (Grishanov 2006) and eutrophication (Kear 2005). The north-west European population is thought to be particularly sensitive to land-use change as well as climate change due to its narrow breeding distribution across the Russian high Arctic and its high dependency on a small number of stop-over sites during spring and autumn migration (Nagy et al. 2012). In the Far East declines have been recorded owing to decreases in submerged vegetation, possibly as a result of eutrophication and changes in hydrology brought about by dam construction (Cong et al. 2011, Carboneras and Kirwan 2016). Its Arctic breeding habitat is also threatened by oil and gas exploration (Kear 2005). The species is threatened by mortality from oil pollution (oil spills) in moulting and pre-migrational staging areas, from collisions with powerlines, and from lead poisoning as a result of lead shot (del Hoyo et al. 1992, Kear 2005) and fishing weight ingestion during migration and on wintering grounds (Kear 2005). The species suffers from poaching in north-west Europe, is hunted for sport in North America (del Hoyo et al. 1992, Kear 2005) and is hunted considerably for subsistence throughout its range (del Hoyo et al. 1992). The species is also susceptible to avian influenza, so may be threatened by future outbreaks of the disease (Melville and Shortridge 2006).
Conservation Actions Underway
CMS Appendix II. EU Birds Directive Annex I (subspecies found in Europe). Bern Convention Appendix II. Category A(2) of the African Eurasian Waterbird Agreement (AEWA). Possible race jankowski included in CITES II (Carboneras and Kirwan 2016). Listed in the Red Data Book of Russia (2000) under the category rehabilitating species. Part of its breeding areas and stop-over sites in Russia are protected as nature reserves. In spring, at least 60% of the Europe-northern Russia flyway population passes through the Dvinskoi sanctuary in the south-east corner of the White Sea. Natura 2000 network protects some of the key staging and wintering wetlands in the EU, but most feeding sites are on arable and grasslands outside of these sites. In all European range countries it is protected from direct persecution by national law. In Estonia and Lithuania active site management programmes are in place for this species at key stop-over sites. Important wintering sites are managed in the U.K. (by the RSPB and WWT) and in the Netherlands. The EU's environmental and nature conservation financial instrument LIFE has co-financed several targeted demonstration and best practice projects in countries such as Finland, Latvia and the Netherlands, aimed at the conservation of coastal inlets and wetlands which are habitats used by the species. Monitoring of populations and breeding success in most countries within its European range and intensive research on its ecology has been carried out in the Netherlands and at various stop-over sites in recent decades (Nagy et al. 2012).
Conservation Actions Proposed
The protected status of the species across its European range should be maintained. Key stop-over and wintering sites should be maintained and, if necessary, restored, ensuring suitable aquatic macrophyte availability through managing water levels and water quality. In addition, measures should be implemented to prevent the negative impacts of infrastructure and industrial development by avoiding key sites, or by mitigating any potential negative impacts in the absence of alternative locations. Where necessary, develop and implement emergency plans by companies involved in the exploitation and transportation of petrochemicals on the flyway to reduce mortality in case of accidents. Monitoring and research of population changes and demographic parameters should continue and dead bird surveillance should be expanded to cover the entire flyway of the species. Introduce compensatory payments and other site management measures and increase efforts to reduce illegal shooting (Nagy et al. 2012).
Text account compilers
Butchart, S., Ekstrom, J., Malpas, L. & Ashpole, J
BirdLife International (2019) Species factsheet: Cygnus columbianus. Downloaded from http://www.birdlife.org on 13/12/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/12/2019.