Black-necked Swan

Identification

The black-necked swan is South America's largest native waterfowl and one of the most striking swans in the world. Adults are 102 to 124 cm long with a wingspan of 135 to 177 cm, with males weighing 4.6 to 8.7 kg and females slightly smaller at 3.5 to 4.4 kg. The plumage is unmistakable: a pure white body contrasts dramatically with a black neck and head, typically marked by a distinctive white stripe behind the eye. A prominent red knob at the base of the bill adds to their elegant appearance. Males and females look identical. Juveniles are grayish rather than white and lack the characteristic red knob until their third or fourth year, making them readily distinguishable from adults.

Range & habitat

Black-necked swans inhabit the southern tier of South America, with their breeding range extending from Tierra del Fuego north through central Chile, Uruguay, and Rio Grande do Sul in extreme southern Brazil. They are year-round residents of the Falkland Islands but withdraw from southern Argentina during winter, dispersing as far north as São Paulo state in Brazil. The species prefers freshwater marshes, swamps, and shallow lakes, as well as brackish lagoons and sheltered coastal sites. On mainland South America, they often inhabit areas near human settlements, though they avoid built-up zones in the Falklands. While typically found at low elevations, non-breeding flocks occasionally reach 900 to 1,250 metres in the Andes of southern Argentina.

Behaviour & diet

Black-necked swans are almost entirely vegetarian, feeding on aquatic plants such as Chara, Potamogeton, and Typha, as well as algae species. In parts of Chile, the aquatic plant Egeria densa forms their principal food source. They forage by immersing their heads and necks, surface feeding, and upending to reach deeper vegetation; during droughts they graze in meadows and pastures. The breeding season varies geographically, occurring from July to November in the far south but ending by September in northern areas, with timing dependent on rainfall. Pairs construct large vegetation mounds on small islets or in floating reeds, typically laying clutches of four to eight eggs. Males guard females during the 34- to 36-day incubation period, with nestlings fledging approximately 100 days after hatching. Outside breeding season, black-necked swans are mostly silent, but both sexes produce soft, musical calls during breeding to challenge intruders and maintain pair contact.

Best time & places to see it

The black-necked swan is widespread and generally common throughout its range, with an estimated population of around 50,000 in Argentina alone. Key locations include Carlos Anwandter Nature Sanctuary on the Cruces River in Chile, which has become an important population center, particularly for photographing large congregations. The Falkland Islands offer year-round viewing opportunities. The breeding season, varying from July to November depending on location and rainfall, offers the best chance to observe pair bonding behaviour and hear their distinctive vocalizations. Winter months may provide opportunities to see larger flocks as birds disperse northward from southern regions.

Photography tips

The striking contrast between white body plumage and black neck makes black-necked swans highly photogenic subjects. Their elegant red knob and white eye-stripe provide excellent focal points for close-up portraits. Wetland habitats with clear water allow photographers to capture reflections, while open water backgrounds emphasize their distinctive colouration. Early morning light during breeding season, when birds are most vocal and active, offers optimal shooting conditions. Nesting birds on floating vegetation present unique compositional opportunities, though photographers should maintain respectful distance to avoid disturbing breeding pairs. The dramatic landscapes of southern South America—from Patagonian lakes to coastal marshes—provide compelling backdrops for environmental portraits.