Blue duck  (Hymenolaimus malacorhynchos)

The blue duck, as its name suggests, has dusky blue-grey plumage with chestnut markings on the chest. The eyes are yellow and the bill is pale pink in colour; juveniles have a grey bill and eyes (2).

Endemic to New Zealand, the blue duck was previously widespread throughout the country (2). A significant decline has occurred however, and remaining populations are severely fragmented in isolated areas of habitat that remain (4).

Blue ducks are found only in riverine habitats, where the water quality is good and there is bankside vegetation (3).

Nests are located in caves and crevices on the riverbank; females are able to breed in their first year and usually lay a clutch of around six eggs (2). These ducks feed on invertebrates, particularly on caddis fly larvae (2) (4), and the average lifespan is eight years (4).

Habitat loss has been one of the major causes of decline in this species. The clearance and grazing of riverside vegetation has led to the depletion of water quality in many rivers and has restricted the blue duck to less accessible mountainous areas (2). Predation by introduced mammals such as stoats and competition with introduced trout may also have played a part in the decrease and fragmentation of this species' range (2).

The New Zealand Department of Conservation published a Blue Duck Recovery Plan in 1997 in an effort to secure the survival of this species in the wild and to downgrade its current threat status (4). Some of the conservation measures involved include captive breeding and release attempts and the protection of key areas of habitat. Ongoing population monitoring is also a priority in the conservation of this attractive waterbird (4).

• BirdLife International:
  www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=422&m=0
• Adams, J., Cunningham, D., Molloy, J, and Phillipson, S. (1997) Blue Duck (Whio), Hymenolaimus malacorhynchos Recovery Plan. Department of Conservation, New Zealand. Available at:
  www.doc.govt.nz/upload/documents/science-and-technical/TSRP22.pdf

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