Hawaiian Duck

Anas wyvilliana

U.S. Fish & Wildlife Service
  • ANATIDAE
  • Swans, Geese, Ducks
  • 2,200

A very shy, dark brown duck, the Hawaiian Duck is in danger from both loss of wetland habitat and genetic swamping through interbreeding with feral Mallard Ducks. Most pairs breed year-round near mountain streams, ponds, agricultural fields, and river valleys. Once an inhabitant of all the Hawaiian islands except Lanai, it later became restricted to Kauai and Niihau but has been reintroduced to Oahu, Hawaii, and Maui.

Identification
A close relative of the Mallard (Anas platyrhynchos), the Hawaiian Duck looks quite similar to certain plumages of the Mallard. It is dark with orange legs and its call is higher-pitched than that of the Mallard. Males show two types - one with dark green crown and nape and reddish flush to the breast, and the other a more mottled brown, resembling the female. Females are smaller than the Mallards. Hybrids between the two species display a variety of combinations of parental characteristics.

Distribution and Population Trends
Although its range covers elevations from sea level to 8,000 feet and it occupies coastal swamps, freshwater ponds, bogs, forest swamps, streams and marshy areas, this duck is fairly sedentary. The total population numbers betwee 2,200-2,525 individuals, with 80% found on the islands of Kauai and Niihau. The largest population occurs at the Hanalei National Wildlife Refuge on Kauai. The remainder have been re-introduced to the islands of Oahu, Hawaii, and Maui. At higher elevations on Mauna Kea on Hawaii where there are no Mallards, there is now a sedentary population of pure Hawaiian Ducks.

Ecology
The species feeds on grass seeds and other vegetation, crustaceans, insects and nematodes. Most pairs breed year-round (with a peak between January and May) near mountain streams where they lay up to 10 eggs in a down-filled ground nest.

Threats
Hybridization with feral Mallards is the main concern for this species. Loss of wetlands by drainage and alien plant encroachment, and predation on the young by introduced predators (cats, dogs, rats, pigs, mongoose) are also important considerations.

Conservation
This species was hunted through 1925 at which point measures were taken to bring hunting under control. The species was first listed as Endangered under the Endangered Species Preservation Act in 1967. The creation of waterfowl refuges has helped conserve key habitat. In particular, the 917-acre Hanalei National Wildlife Refuge on Kauai is perhaps the most important refuge for the species. In locations like the Hanalei National Wildlife Refuge control of introduced predators is an important management tool to increase nest success of Hawaiian Ducks. Several projects have been initiated by Ducks Unlimited and other organizations in recent years to restore wetlands, particularly at higher elevations where Mallards do not occur. In 2001, a Safe Harbor Agreement was signed between the Umikoa Ranch, the U.S. Fish and Wildlife Service, and Hawaii's Department of Land and Natural Resources under which the ranch owners agreed to restore and maintain 180 acres of habitat for 20 years at the high elevation ranch on the island of Hawaii. This habitat is expected to be used by Hawaiian Ducks and other species. Hawaiian Ducks continue to be bred in captivity and have been used for reintroductions on Oahu, Hawaii, and Maui. In addition to the measures described here, BirdLife International recommends vigorously controlling Mallards and hybrids to allow genetic continuation of the pure species.

What Can You Do?
Join Hawaii Audubon Society. A chapter of National Audubon, the Hawaii Audubon Society works to protect and educate people about Hawaii's birds. For more information visit http://www.audubon.org/chapters/hawaii-audubon-society .

The Endangered Species Act has helped protect the Hawaiian Duck and made it possible to learn critical information about its biology. Audubon continues to work to ensure that this vital legislation is being used to protect our publicly-owned wildlife resources. Check out http://policy.audubon.org/ to learn of the latest news about the Endangered Species Act and how you can help. To learn more about other species protected under this legislation, visit: http://endangered.fws.gov/

U.S. National Wildlife Refuges provide essential habitat for the Hawaiian Duck, and a great number of other species throughout the U.S. and its territories. Unfortunately, the refuge system is often under-funded during the U.S. government's budgeting process. To support  U.S. National Wildlife Refuges, consider purchasing a duck stamp which helps to fund wetland habitats in refuges:  http://www.fws.gov/duckstamps/

References
Birdlife International. 2000. Threatened Birds of the World. Lynx Edicions, Barcelona.

BirdLife International (2006) Species factsheet: Anas wyvilliana,Hawaiian Duck http://www.birdlife.org/datazone/speciesfactsheet.php?id=436

Ehrlich, P.R., Dobkin, D.S., and D. Wheye. 1992. Birds in Jeopardy. Stanford University, Stanford, CA.

Madge, S., and H. Burn. 1988. Waterfowl: An Identification Guide to the Ducks, Geese, and Swans of the World. Houghton Mifflin, Boston.

Pratt, H.D., P. L. Bruner, and D. G. Berrett. 1987. The Birds of Hawaii and the Tropical Pacific. Princeton University Press, Princeton, NJ.

Shallenberger. R.J. 1984. Hawaii's Birds. Hawaii Audubon Society, Honolulu, HA.