Pacific Black Duck
The Pacific Black Duck (Anas superciliosa) is a dabbling duck found throughout much of Indonesia, New Guinea, Australia, New Zealand, as well as many islands in the southwestern Pacific, reaching to the Caroline Islands in the north and French Polynesia in the east. It is usually called the Grey Duck or Parera in New Zealand.
This gregarious duck is found in a variety of wetland habitats, and its nesting habits are much like those of the Mallard, which is encroaching on its range in New Zealand. It feeds by upending, like other Anas ducks.
It has a dark body, and a paler head with a darkcrown and facial stripes. In flight it shows a green speculum and pale underwing. All plumages are similar. The size range is 54-61 cm; males tend to be larger than females, and some island forms are smaller and darker than the main populations. It is not resident on the Marianas islands, but sometimes occurs there during migration. The now-extinct Mariana Mallard was probably originally derived from hybrids between this species and the mallard, which came to the islands during migration and settled down there.
There are three subspecies of Anas superciliosa: rogersi breeds in Indonesia, New Guinea and Australia, pelewensis on the southwest Pacific islands, and superciliosa in New Zealand. The New Zealand subspecies has declined sharply in numbers, at least in its pure form, due to competition from and hybridisation with the introduced mallard. Rhymer et al. (1994) say their data “points to the eventual loss of identity of the Grey Duck as a separate species in New Zealand, and the subsequent dominance of a hybrid swarm akin to the ‘Mariana Mallard.’”