The black-necked swan's breeding season varies geographically. In the far south of its range it breeds from July to November but ends as early as September in the northern parts. In the Falklands it breeds between August and November. The exact timing of breeding appears dependent on rainfall. The species is believed to form long-term pair bonds. Its nest is a mound of vegetation constructed by both members of a pair on a small islet or partially floating in a reedbed. The clutch size is four to eight eggs. Males guard females during the 34 to 36 day incubation period. Captive nestlings fledged about 100 days after hatch. Vocalization The black-necked swan is mostly silent outside the breeding season. During that time both sexes give a "soft, musical 'Whee-whee-whee' with accent on initial syllable", repeating it to challenge intruders. The call is also used to maintain contact between members of a pair. Males also give "a musical 'hooee-hoo-hoo'." Status and conservation The IUCN has assessed the black-necked swan as being of Least Concern. It has a very large range, and though its population size is not known it is believed to be stable. No immediate threats have been identified. It is widespread and generally common. Large scale hunting in the 18th and 19th centuries extirpated it from much of Chile but it has recolonized those area. Some egg collecting and hunting still occur, however. The species occurs in several protected areas in mainland Argentina, in which country the population is estimated at 50,000. Gallery References Further reading David, N. & Gosselin, M. (2002). "Gender agreement of avian species names." Bull. B. O. C. 122: 14–49. External links Stamps (for Argentina, Brazil, Chile, Falkland Islands, Uruguay) with RangeMap Black-necked Swan photo gallery VIREO black-necked swan Birds of Chile Birds of the Falkland Islands Birds of the Pampas Birds of Patagonia black-necked swan black-necked swan