Blue-billed Duck

The Blue-billed Duck (Oxyura australis) is a diminutive stiff-tailed duck endemic to Australia. Both sexes reach approximately 40 cm in length. The male is notable for its slate-blue bill, which intensifies to a vivid blue during the breeding season, and its deep chestnut plumage that transitions to dark grey outside of this period. The female maintains a consistent black plumage with brown-tipped feathers throughout the year. This species is distinguished by its low profile on the water and its powerful feet, which are well-adapted for swimming and diving.

Identification Tips

Males in breeding plumage exhibit a bright-blue bill, glossy black head and neck, and rich chestnut back and wings. In contrast, non-breeding males and females have a more subdued appearance, with the males sporting grey-speckled black heads and dark grey bodies, and the females displaying dark brown heads with mottled black and light-brown tipped feathers. Juveniles resemble adult females but are paler with a grey-green bill.

Habitat

The Blue-billed Duck favors deep, freshwater swamps with dense vegetation, such as cumbungi reeds, but can also be found in lignum swamps and occasionally large rivers and saline water bodies. They are almost entirely aquatic and exhibit a penguin-like gait on land.

Distribution

This species is widespread across Australia's temperate regions, from southern Queensland through New South Wales and Victoria to Tasmania, and in the south-west of Western Australia. They are most abundant in the Murray-Darling basin.

Behaviour

Outside of the breeding season, Blue-billed Ducks may form large flocks on open lakes or dams. During breeding, they become secretive and wary, diving underwater to escape threats. The male's courtship display is elaborate, involving a series of movements such as rolling, dab-preening, and sousing. Post-mating, males often desert the females who then build nests and incubate the eggs.

Song & Calls

The Blue-billed Duck's vocalizations are infrequent, but when heard, they produce a low quack.

Breeding

Breeding may occur throughout the year, with clutch sizes ranging from 3 to 12 eggs. The female may lay eggs in the nests of other waterbirds, a behavior known as "facultative parasitism." Incubation lasts 26 to 28 days, and the ducklings are relatively independent upon hatching.

Similar Species

The Blue-billed Duck can be confused with other stiff-tailed ducks, but its unique bill coloration during breeding season and its habitat preferences help distinguish it.

Diet and Feeding

An omnivorous species, the Blue-billed Duck sifts mud underwater for small invertebrates, seeds, buds, and fruits of aquatic plants. It has a particular fondness for chironomid larvae and other aquatic insects.

Conservation status

Classified as Least Concern by BirdLife International, the Blue-billed Duck faces threats from habitat degradation due to introduced fish, cattle grazing, salinization, and groundwater changes. Conservation efforts focus on maintaining sustainable water flows and managing salinity. The species is listed as vulnerable in New South Wales and threatened in Victoria.

Relationship with humans

The Blue-billed Duck serves as an indicator species for wetland health. A decline in their numbers can signal ecological issues within freshwater systems, such as salinity and overgrazing impacts.

Other comments

Further research is needed to determine the average lifespan of the Blue-billed Duck in the wild and to validate its effectiveness as an indicator of habitat health.