By DickDaniels (http://carolinabirds.org) (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) -
Australia. Much of Australia including Tasmania but absent from eastern Western Australia and western South Australia and also regions of the north.
Like all other ducks in captivity they are not generally kept in secure confinement and they may stray. Apparantly quite hardy in Britain and could possibly survive without assistance.