A boldly-patterned, unmistakable bird, the black-necked swan (Cygnus melancoryphus) is a charismatic inhabitant of wetlands in southern South America (2)(4). This majestic waterbird is easily distinguished by its immaculate white body plumage that contrasts sharply with a velvety black neck and head (2)(5)(6). The bill is a blue-grey colour with a conspicuous, scarlet-coloured, double-lobed knob, known as a caruncle, sitting at the base (5). A thin white line surrounds the eyes and stretches along the sides of the crown to the rear of the head (6). The male and female black-necked swan are similar in appearance, although the female is typically slightly smaller, but the juvenile lacks the caruncle, has a more brownish-black neck and head, and has varying amounts of greyish-flecked and brownish-tipped feathers (2)(5)(6). Like other swans, the black-necked swan is amongst the largest of waterbirds, with a long neck and bulky body borne on relatively short, set-back legs. It is a strong flier that is capable of long-distance migrations and speeds of up to 50 miles hour, but it is not very mobile and quite ungainly on land (7)(8). While most swans are known for their loud calls, the black-necked swan has a soft, musical whistling note that is repeated often, especially during flight (8).
The black-necked swan’s diet consists almost entirely of aquatic vegetation, which it collects from below the water surface using the long, extended neck to reach food on pond bottoms, and the bill to filter-out smaller food items. Insects and fish eggs may also be consumed, and it may even come onto land to graze upon terrestrial plants (2)(5)(8).
Social and gregarious for much of the year, during the breeding season the black-necked swam becomes territorial and aggressive (8). It breeds from July to August and mates for life, with large nests constructed from vegetation in reedbeds close to the water’s edge on small islets, or less preferably on land (2)(8). Four to seven eggs are incubated by the female for around 36 days and the chicks are tended to by both adults (2). The young, vulnerable hatchlings stay close to their parents, occasionally even riding on the parents’ backs, and stay with the parent birds for up to a year, only separating at the start of the following breeding season (5)(7).
The black-necked swan is found in southern South America, ranging from the Falkland Islands and Tierra del Fuego, northwards to central Chile, Paraguay and southern Brazil (2)(5). It is also an occasional visitor to the Antarctic Peninsula and the Juan Fernández Islands (5).
Throughout its range, the black-necked swan is considered to be a relatively common species lacking any major threats to its survival (2)(9). It is generally not a hunting target, but was once eradicated from parts of Chile due to such exploitation for food and for its down, which is used in clothing and bedding, although populations have now recovered to recolonise these areas (2)(8). It is, however, threatened in parts of its range by wetland drainage and by decreases in water quality as a result of industrial activity (2)(4). In addition, contrary to many bird species in South America, which are generally negatively impacted by El Niño events, the increased rainfall associated with these events benefits the black-necked swan, as it is able to colonise newly formed wetlands and temporarily expand its range (10)(11).
Although not the target of any known conservation measures, the black-necked swan is likely to have benefited from a number of conservation measures aiming to maintain or restore natural habitats within its range, such as those undertaken on the Falkland Islands (12). It is also found at a number of designated Ramsar Sites, with the Ramsar designation recognising the sites’ conservation, ecological and scientific value and the importance in preserving them (4)(13).
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Slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.
A natural phenomenon that happens every 4 to 12 years, and lasts for several months, when upwelling of cold, nutrient-rich water does not occur. This causes the warming of ocean surface water off the western coast of South America and causes die-offs of plankton and fish. It also affects Pacific jet stream winds, altering storm tracks and creating unusual weather patterns in various parts of the world.
To keep eggs warm so that development is possible.
Describes an animal, a pair of animals or a colony that occupies and defends an area.
Lopetegui, E.J. et al. (2007) Emigration and mortality of black-necked swans (Cygnus melanocoryphus) and disappearance of the Macrophyte Egeria densa in a Ramsar Wetland Site of Southern Chile. Ambio, 7: 607-609.
Chester, C.R. (2008) A Wildlife Guide to Chile: Continental Chile, Chilean Antarctica, Easter Island, Juan Fernández Archipelago. Princeton University Press, New Jersey.
Blake, E.R. (1977) Manual of Neotropical Birds. Volume 1: Spheniscidae (Penguins) to Laridae (Gulls and Allies). University of Chicago Press, Chicago and London.
Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
Vilina, Y.A., Cofré, H.L., Silva-García, C., García, M.D. and Pérez-Friedenthal, C. (2002) Effects of El Niño on abundance and breeding of black-necked swans on El Yali wetland in Chile. The International Journal of Waterbird Biology, 25: 123-127.
Schlatter, R.P., Navarro, R.A. and Cort, P. (2002) Effects of El Niño Southern Oscillation on numbers of black-necked swans at Río Cruces Sanctuary, Chile. The International Journal of Waterbird Biology, 25: 114-122.
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