Coscoroba Swan – Coscoroba coscoroba (Molina, 1782)

C. coscoroba is the only swan not part of the Cygnus genus, having been shown to descend from the Anatidae family in its own monotypic genus.

Appearance: The Coscoroba Swan is the smallest of all swans, at only 900-1150mm in length (compared to the Trumpeter at ~1800mm). The Coscoroba has white plumage except for black tips on its primaries. It has a short neck with a rounded headshape, featuring feathers that extend well beyond the eyes to cover the face, similar to whistling ducks. They have short broad wings compared to northern migratory swans, and have a short rounded tail (Delacour 1954–64). Coscoroba’s also have a bright red bill that is spatulate and upturned, similar to that of a duck.

Cygnets are mainly grey – white but have dark patterning on the crown, back and wings, unlike all other swan species. They have a grey bill that becomes red by 5 months. They develop adult white plumage by 8 months, with the exception of some flecks of grey feathers on the to of the head.  Sexual maturity is reached at around 3 years.

Voice: Unlike other swan species, notes are noticeably higher in males than in females. Hooting notes are used between paired birds, often with the male sounding first. Immatures give loud chirping calls and trills approached by parents, and give loud aggressive chirping calls when approached by other aggressive swans.

Moult: Moult patterns of wild Coscorobas is unknown but based on captive individuals are assumed to have one moult of body and wing feathers annually. Captive adults in the northern hemisphere have been observed moulting flight feathers in late July-August, whereas in south Brazil this is known to happen in August-November (Nascimento et al. 2001).

Distribution: The Coscoroba Swan is native to South America, seeming to prefer coastal areas. This swan occurs in Tierra del Fuego and Falkland Islands, north through Chile, Argentina and Paraguay to Southern Brazil (Scott, 1972). They tend to breed in southern parts of Argentina and Chile. Little is known of the migratory routes taken by these birds during winter months, but it is thought most that move into Uruguay arrive from Argentina (Vaz-Ferreira and Rilla 1991). The Coscoroba’s range overlaps that of the black-necked swan which occurs in the same regions.

 

Population Year of latest pop. estimate Population size Data types Trend years Trend Trend quality 1% threshold Source
South America 2006 10,000-25,000 Best guess 1982-1992 STA UNK 250 Wet int

From: Wetlands International, 2016. Unpublished information supplied by Wetlands International Specialist Groups, 2006. From: Wetlands International (2016), (1) Unpublished information supplied by Wetlands International Specialist Groups, (2006), (2) Canevari, (1993).

Habitat: Wetland areas including marshes and lakes with well vegetated banks (Fjeldså and Krabbe, 1990).  Permanent freshwater lakes over 8ha in size are considered important for C.coscoroba both in and out of mating season.

 

Protection: CITES appendix II

IUCN Red List Assessment: Least Concern (LC)

Current population trend: Stable

Threats: Human hunting for food. Taken for pets and animal displays. (BirdLife International, 2012)

References

BirdLife International (2012). Coscoroba coscoroba. The IUCN Red List of Threatened Species 2012. Available from: http://www.iucnredlist.org/details/22679866/0 [Accessed 7 March 2016]

Canevari, P. (1993) Unpublished information from Neotropical Wetlands Program.

Delacour, J. (1954–64) The waterfowl of the world. Country Life, London.

del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. (2014) HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions and BirdLife International.

Fjeldså, J. and Krabbe, N. 1990. Birds of the High Andes. Zoological Museum, Univ. Copenhagen, and Apollo Books, Svendborg, Denmark.

Kear, J. (2005) Ducks, geese and swans volume 1: general chapters; species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, U.K.

Nascimento, J.L.X., Flores, J.M., Ataguile, B.S., Koch, M., Scherer, S.B. and Santos, P.J.P. 2001. Biological aspects of the Black-necked Swan (Cygnus melancoryphus) and Coscoroba Swan (Coscoroba coscoroba) in Rio Grande do Sul state, Brazil. Melopsittacus, 4:31–38.

Scott, P. and The Wildfowl Trust 1972. The swans.Michael Joseph, London.

Vaz-Ferreira, R. and Rilla, F. 1991. Black-necked Swan Cygnus melancoryphus and Coscoroba Swan Coscoroba coscoroba in a wetland in Uruguay. Wildfowl Spec. Suppl., 1: 272–77.

Wetlands International (2016) Waterbird Population Estimates. Available from: wpe.wetlands.org [Accessed Friday 5 Feb 2016].