The Raja Shelduck or Radjah Shelduck (Tadorna radjah), also known as the Burdekin Duck in Australia, is a species of shelduck. Placed in the genus Tadorna, it differs markedly in external morphology, and mtDNA cytochrome b sequence data suggests its status should be reinvestigated. The genus name Tadorna comes from Celtic roots and means "pied waterfowl", essentially the same as the English "shelduck".
Both the male and female of the species are mostly white, with dark wing-tips and a distinctive "collar" of dark feathers. Seen from above in flight the birds have green bands on the tops of their wings. The female has a harsh rattle and the male has a breathy, sore-throat whistle.
The Radjah Shelduck inhabits the mangrove forests and coastline of New Guinea and Australia. In Australia, its primary range is coastal tropical northern Australia, from central Queensland through northern Northern Territory (including Kakadu National Park) to the Kimberley in Western Australia.
The species prefers the brackish waters of mangrove flats and paperbark tree swamps, but will visit freshwater swamps, lagoons, and billabongs further inland during the wet season.
The Raja Shelduck forms long-term pair-bonds, and is usually encountered in lone pairs or small flocks. During the wet season the males commonly become very irritable, and have been observed attacking their mates.
The diet consists mainly of mollusks, insects, sedge materials and algae. Pairs start searching for nesting sites during the months of January and February. They nest close to their primary food source, often in the hollow limbs of trees, which makes habitat destruction a particular issue.
The Raja Shelduck does not use nesting materials except for some self-supplied down feathers. Egg-laying is usually done by May or June, but depends on the extent of the wet season. The clutches range from 6 to 12 eggs. Incubation time is about 30 days.
The Raja Shelduck is listed as a protected bird in all states of Australia and penalties exist for harming or disturbing them.