The blue duck is a type of waterfowl found in New Zealand. Blue ducks are unique in that they do not appear to be related to any other species of duck and exhibit behaviors atypical of other duck species. The scientific name for the blue duck is Hymenolaimus malacorhynchos.
An endemic species, the blue duck lives exclusively in New Zealand. Averaging 21 inches (53 cm) in length, these ducks are blue-gray with brown chest markings. They have yellow eyes, pink bills, and are not strong fliers.
Blue ducks are territorial, and their river habitats often have swiftly moving currents. Unlike many ducks, the blue duck can maneuver in swift rapids and hold onto large rocks while feeding under water. Their diets consist of invertebrates and caddisfly larvae.
Although blue ducks can breed in their first year, most do not begin breeding until they are two years old. Unusual to most duck species, blue ducks appear to mate for life and males take part in caring for the young. Nesting occurs in August through November, and nests are made in caves or crevices in rocks.
The female lays four to seven eggs, which are incubated for about one month. The young are generally black and white, but have a particular sheen that camouflages them while they swim in the water. They also have large feet, disproportionate to their bodies, to aid them in swimming in the strong river currents. Ducklings stay with parents for about eight to ten weeks, then find their own territories, usually nearby. Blue ducks live for about eight years.
The blue duck has several different common names. In addition to "blue," which refers to its coloring, it is also called a mountain duck or torrent duck, because of its habitat. Another common name is the whistling duck, after the male's whistling call.
As of 2010, the blue duck population was approximately 2,000–4,000, and this species was considered endangered. Habitat destruction is the primary cause for the decline, as evidenced by the ducks disappearance from their former lowland habitats. Additional causes include the introduction of new species, such as stoats, and the need to compete for food with the increased population of trout in New Zealand rivers. In 1997, the New Zealand Department of Conservation instituted a Blue Duck Recovery Plan to attempt to save the species. The program has been marginally successful, and although the population still continues to slowly decline, it is mostly stable.