Blue Duck / Whio

(Hymenolaimus malacorhynchos)

Live: Fiordland and Coromandel in New Zealand.

Habitat: Undisturbed fast-flowing turbulent rivers in mountainous areas.

Diet: Freshwater insects including larvae, bloodworms, aquatic snails, midges and other small flies. They have been reported feeding on berries from streamside coprosma shrubs.

Gestation: 4-9 eggs are incubated by the female for 31-32 days.

Status: Endemic, threatened and protected

General: Once widespread and now restricted due to changes in their environment, e.g. dams, farming, forestry, erosion resulting in increased sedimentation, introduced predators, and species in competition (such as trout).

Male and female are similar in appearance. The general body colour is slate blue-grey. Legs and feet are pale grey, with black joints and webs. As their colour resembles a river boulder, Whio are very well camouflaged.

Each sex has a range of calls, the most notable being the males' 'fee-or' (hence the Maori name).

Active at dawn and dusk, feeding is usually in shallow white water, with the head and neck submerged to scrape insects off the downstream sides of rocks. The ducks may also dive. Territory is around 1km of waterway, which birds will fight to protect, even from fledged young. Whio tend to swim away from danger rather than fly.

Breeding: Generally between August and November.

They nest in hollow logs, tree trunks, vegetation, and other shelter close to stream edges. The nest is a collection of sticks and grasses within reach, lined with down.

The duckling's upper body is mostly dark grey, the lower body white. The face is white with dark stripes through the eyes. The bill is grey-blue, feet yellow-brown.

Parents are very attentive. The female feeds close to the chicks while the male keeps constant guard. As many ducklings are swept away by the water or killed by introduced predators, the mortality rate is high. Two surviving chicks are regarded as a successful breeding season.