Pacific Black Duck
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| Anas superciliosa Gmelin, 1789 |
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The Pacific Black Duck, Anas superciliosa is a dabbling duck found in much of Indonesia, New Guinea, Australia, New Zealand, and 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 Pārera in New Zealand.
This sociable 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 (Rhymer & Simberloff 1996). It feeds by upending, like other Anas ducks.
It has a dark body, and a paler head with a dark crown 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 (Gillespie, 1985). 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.'"
It was assumed that far more mallard drakes mate with Grey Duck females than vice versa based on the fact that most hybrids show a mallard-type plumage, but this is not correct; It appears that the mallard phenotype is dominant, and that the degree to which species contributed to a hybrid's ancestry cannot be determined from the plumage (Rhyner et al. 1994). The main reasons for displacement of the Pārera seem to be physical dominance of the larger mallards, combined with a marked population decline of the Pārera due to overhunting in the mid-20th century (Williams & Basse 2006)
[edit] Gallery
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[edit] References
- BirdLife International (2004). Anas superciliosa. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is of least concern
- Gillespie, Grant D. (1985): Hybridization, introgression, and morphometric differentiation between Mallard (Anas platyrhynchos) and Grey Duck (Anas superciliosa) in Otago, New Zealand. Auk 102(3): 459-469. PDF fulltext
- Heather, Barrie D. & Robertson, Hugh A. (1996): The Field Guide to the Birds of New Zealand. Viking/Penguin, Auckland. ISBN 0-670-86911-2
- Madge, Steve & Burn, Hilary (1987): Wildfowl : an identification guide to the ducks, geese and swans of the world. Christopher Helm, London. ISBN 0-7136-3999-7
- Rhymer, Judith M. & Simberloff, Daniel (1996): Extinction by hybridization and introgression. Annu. Rev. Ecol. Syst. 27: 83-109. DOI:10.1146/annurev.ecolsys.27.1.83 (HTML abstract)
- Rhymer', Judith M.; Williams, Murray J. & Braun, Michael J. (1994). Mitochondrial analysis of gene flow between New Zealand Mallards (Anas platyrhynchos) and Grey Ducks (A. superciliosa). Auk 111(4): 970–978. PDF fulltext
- Williams, Murray & Basse, Britta (2006): Indigenous gray ducks, Anas superciliosa, and introduced mallards, A. platyrhynchos, in New Zealand: processes and outcome of a deliberate encounter. Acta Zoologica Sinica 52(Supplement): 579–582. PDF fulltext
[edit] External links
Categories: Least Concern species | Ducks | Anas | Birds of Australia | Birds of Western Australia | Birds of Indonesia | Birds of New Zealand | Birds of Papua New Guinea | Birds of American Samoa | Birds of Cook Islands | Birds of Fiji | Birds of French Polynesiaa | Birds of Federated States of Micronesia | Birds of Palau | Birds of Samoa | Birds of Solomon Islands | Birds of Tonga | Birds of Vanuatu
