Black Necked Swan

The black-necked swan's diet is almost entirely vegetarian. It feeds on aquatic plants like Chara, Potamogeton, Typha; algae such as Aphantotece and Rhyzoclonium; and presumably small numbers of aquatic invertebrates. In parts of Chile its principal food is Egeria densa. It forages mostly by immersing its head and neck and by surface feeding, but also upends to reach deeper. In times of drought it has been observed grazing in meadows and pastures.

The black-necked swan is the only member of its genus that breeds in the neotropics and is the largest waterfowl native to South America.

 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.