Bird of the Week: Whio

White-water specialists

By Cushla McCaughey

The whio is an ancient species of duck found only in New Zealand.

Evolving in isolation millions of years ago, whio have several unique features. Male and female are alike in plumage. They also lack the iridescent bar of wing feathers usual on other ducks. Most duck species feed and breed on the calm waters of lakes and wetlands.

Whio inhabit boulder-strewn rivers where each pair claims and vigorously defends its own territory all year round.

Streamlined head, heavy body and extra large feet enable whio to feed in fast flowing water. Unusually forward-set eyes allow whio to scan the rocks for food. A rubbery flap overlapping the lower bill assists in scraping algae, insect larvae and freshwater snails from the rock surfaces. Blue-grey plumage merges perfectly with the river boulders as the birds feed, facing upriver with head and neck submerged

Close-knit families

Whio have strong pair bonds and both parents take an active role in caring for their young. The nest is just a heap of sticks and grasses, usually close to the water’s edge, where spring floods may sweep them away.

The creamy white eggs are incubated by the female, with her mate standing guard nearby. She leaves the nest briefly to feed with him at dawn and dusk. They stay close together, calling softly to each other. These calls are quite distinct for the territorial cry of the male from which the Maori name, “whio”, derives.

Ducklings hatch already equipped with over-sized feet. They can leap up on rocks, paddle against strong currents or scoot across the surface of the water. The adult male moves from rock to rock on the watch for predators, while the female feeds nearby.

Any threat of danger sends the family swimming swiftly away downriver, a line of bobbing ducklings with a parent at either end. Whio were once as common as the ten dollar notes which feature them.  Now fewer than 2,000 breeding pairs remain. From every brood of 6 or 7 ducklings, only one may survive.