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 (Ord, 1815)

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Cramp and Simmons (1977-1994), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

300,000

unset

5,300,000 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 fully migratory and travels on a narrow front via specific routes using well-known stop-over sites³ between its Arctic breeding and temperate wintering grounds¹. It arrives on the breeding grounds from early-May to late-June³ (depending on local conditions)² where it breeds well-dispersed⁵ in single pairs¹, occasionally nesting semi-colonially in optimum habitats^{2, 3}. 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^{3, 4}. Family groups leave the breeding grounds from early-September to late-October³ and arrive on the wintering grounds from mid-October onwards³. During this autumn migration some groups may remain at stop-over sites until moved on by cold weather³. The return northward migration occurs from early-March, with the species travelling in small parties that disperse on arrival in the Arctic³. The species is gregarious outside of the breeding season, often gathering into large flocks of hundreds or thousands of individuals on the wintering grounds^{2, 3}. The species forages by day (where undisturbed)¹ and roosts at night on open water². Habitat Breeding The species breeds near shallow pools, lakes¹ and broad slow-flowing rivers^{1, 2} with emergent littoral vegetation and pondweeds (e.g. Potamogeton spp.) connected to coastal delta areas² in open, moist, low-lying sedge-grass or moss-lichen² Arctic tundra¹. It rarely nests in shrub tundra, and generally avoids forested areas². Non-breeding On migration the species frequents shallow ponds², lowland and upland lakes^{2, 3}, reservoirs³, riverine marshes, shallow saline lagoons² and sheltered coastal bays and estuaries³. During the winter it inhabits brackish and freshwater marshes³, rivers, lakes, ponds² and shallow tidal estuarine areas^{1, 2} with adjacent grasslands¹, flooded pastures² or agricultural arable fields^{1, 2} below 100 m⁵. Diet The species is predominantly herbivorous¹, its diet consisting of the seeds, fruits, leaves, roots, rhizomes and stems of aquatic plants (e.g. Potamogeton, Zostera and Glyceria spp.), grasses¹, sedges, reeds (Phragmites and Typha spp.)² and herbaceous tundra vegetation². During the winter the species complements its diet with agricultural grain and vegetables¹ (e.g. potatoes¹ and sugar beet²), and may also take estuarine invertebrates such as molluscs, amphipods (e.g. Corophium spp.) and polycheate worms on tidal mudflats prior to migration². Breeding site The nest is a large mound of plant matter positioned on elevated ground¹ such as a ridge or hummock, often at some distance from feeding pools to reduce to the risk of flooding². 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)². 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 waterfowl⁸. Plowing was found to reduce the amount of shot available to depths of 20-30 cm (below the foraging zone of the species)⁸.

Threats The species is threatened by the degradation and loss of wetland habitats due to drainage² (e.g. for agriculture)⁶, 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 reeds⁶ and eutrophication². Its Arctic breeding habitat is also threatened by oil and gas exploration². 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^{1, 2} and fishing weight ingestion during migration and on wintering grounds². The species suffers from poaching in north-west Europe, is hunted for sport in North America^{1, 2} and is hunted considerably for subsistence throughout its range¹. The species is also susceptible to avian influenza, so may be threatened by future outbreaks of the disease⁷.

References 1. del Hoyo et al. (1992). 2. Kear (2005a). 3. Madge and Burn (1988). 4. Scott and Rose (1996). 5. Snow and Perrins (1998). 6. Grishanov (2006). 7. Melville and Shortridge (2006). 8. Thomas et al. (2001).

Further web sources of information

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

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 (2010) Species factsheet: Cygnus columbianus. Downloaded from http://www.birdlife.org on 30/7/2010

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.

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