Blue-billed Duck

The behaviour of O. australis depends on its breeding cycle. The ducks gather in large flocks on lakes during the winter while not breeding, although some mature adults remain in vegetative swamps and continue to breed. They will also fly more frequently, probably due to the open habitat, and escape threats by flying. While breeding, O. australis is secretive and wary, and it will swiftly and quietly dive under water if threatened, resurfacing a large distance away, rather than escape by flying. The blue-billed duck has a low quack, which is seldom heard. The courting repertoire of the male is very complex and elaborative. It includes such behaviour as rolling the cheek on the back, dab-preening (also sometimes performed by females), and sousing, where the head is thrown into the water in a prone position, and the back arched as if in spasm, with possibly the legs throwing spray above the body. After the courtship ritual, and a vigorous chase, copulation follows with the female completely submerged. The birds then separate and preen themselves. In preparation for laying eggs, the female builds the nest, at which time the male will mostly desert the female.

The blue-billed duck is endemic to Australia's temperate regions. Its range extends from southern Queensland, through New South Wales and Victoria, to Tasmania. The species is also widespread in the south west of Western Australia. O. australis rarely appears on the New South Wales coastline except during times of drought. It is in greatest abundance in the Murray-Darling basin. The blue-billed duck is almost entirely aquatic. While they have been observed on land, they have difficulty walking, exhibiting a penguin-like gait. During non-breeding season, many ducks gather in flocks totalling several hundred, especially juveniles and younger adults, in open lakes or dams in autumn and winter, far from the shore. For the rest of the year, during breeding season, the blue-billed duck prefers deep, freshwater swamps, with dense vegetation including cumbungi Typha orientalis (broadleaf cumbungi) and Typha domingensis (narrow-leaved cumbungi); although it has appeared in lignum swamps in more coastal areas, especially in drier seasons. They have also occasionally been found in large rivers and saline water bodies such as billabongs.

Two substantial land uses combine to have a significant impact on the blue-billed duck. These are: the regulation of wetland ecosystems through drainage, flood mitigation and water harvesting; and vegetation loss due to clearing, overgrazing and salinity. Both result in smaller habitat sizes suitable to water birds. To counteract these impacts, the Department of Environment and Conservation has devised several strategies to increase the blue-billed duck's population. They include retaining sustainable water flows and developing salinity management plans and farm management plans. The Australian population of blue-billed ducks is estimated to be 12 000, although the creation of artificial wetlands such as water treatment works disguise the number occurring in natural wetlands. The blue-billed duck's vulnerable status has been de-listed for the Environmental Protection and Biodiversity Conservation Act 1999, although they are currently recognized as vulnerable in NSW, according to the Department of Environment and Climate Change NSW. The blue-billed duck is listed as threatened on the Victorian Flora and Fauna Guarantee Act (1988). Under this Act, an Action Statement for the recovery and future management of this species has been prepared. In Victoria, the blue-billed duck is also listed as endangered on the 2007 advisory list of threatened vertebrate fauna within the state.