Blue Duck

Hymenolaimus malacorhynchos, the whio, is an endemic river duck of New Zealand. It differs from other ducks through its blue-grey plumage and soft rubbery bill tip adapted to scraping rocks. It is slate-blue with a chestnut-speckled breast and a pale pinkish bill. Males give a clear whistle, while females make a rattling growl.

Whio live on clean, fast-flowing rivers in forested mountain catchments of both main islands. Populations are fragmented where predators or degraded rivers persist. They feed on aquatic insect larvae by dabbling and scraping submerged stones. Pairs hold linear river territories throughout the year.

The New Zealand classification is Nationally Vulnerable. The Tongariro River, Whakapapa River and selected reaches near the Heaphy Track are recognised places to look.