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Endemic to Laysan Island in the Hawaiian Island chain, survival of this nocturnal, teal-sized duck once rested on a single surviving female. From that precarious position, the species has slowly increased but remains highly vulnerable. It eats a specialized diet of macro-invertebrates, the principal one being the brine fly. This species is highly sedentary, and vulnerable to drought.
If you see a small, teal-like duck with white around the eye, foraging in the night on the hypersaline lake in the middle of Laysan Island, count on it being the Laysan Duck! Sexes look similar but the female usually quacks and the male usually whistles.
The species is found only on Laysan Island which is more than 200 kilometers from the next nearest island and was originally though to have occurred nowhere else. More recent studies of fossil bones have shown that the species was once found throughout the Hawaiian Islands and likely disappeared following the settling of the islands by the Polynesians. The species hovered on the brink of extinction between 1905 and 1930 when the population dropped to seven individuals and a single female. This decrease was largely due to a combination of hunting by guano mine workers and plume hunters followed by the introduction of European rabbits, which nearly wiped out all of Laysan Island's vegetation. As a result of this radical habitat degradation, three of the island's four endemic land birds went extinct. Lack of vegetative cover permitted erosion and blowing sand partially filled in the lake. The rabbits all subsequently starved to death, at which point the island began to revegetate. By 1987, the Laysan Duck's numbers were up to 500, but six years later there was a drought that drove the lake's water level down, causing die-offs of the brine flies that are their principal food item, and the population dropped by 50%. Since then it has slowly come back, and currently numbers 375-500 individuals. It is a strong flyer, but uses its wings sparingly and does not migrate or even show seasonal movements.
It feeds on insects, especially brine flies, moths, terrestrial spiders and marine crustaceans. Although it occupies a hyper-saline lake, it spends the majority of its time near the freshwater seeps that feed the lake from the shore. Its nest is concealed in dense vegetation around the edges of the lake. Clutches are small and the reproductive rate is low. Reproductive success is largely dependent on brine fly population levels.
Food shortages - especially during droughts - are currently the main threat to this species, which struggles to maintain a viable population. Non-native insects (ants) are competing for their food, and introduced plant species threaten their nesting habitat. The endangered Laysan Finch has learned to eat the Laysan Duck's eggs, and may be a significant egg predator. Rising sea level may also prove to be a concern.
Laysan Island is legally protected as part of the Hawaiian Islands National Wildlife Refuge. Currently there are no introduced predators on the island and USFWS is responsible for preventing future introductions. The USFWS published a Laysan Duck Recovery Plan in 1982. Snow fences have been installed in strategic locations to prevent further erosion and loss of sand into the lake. Individuals of the species were taken into captivity in the 1950's and the species initially bred quite well so that there are hundreds of Laysan Ducks in captive-breeding facilities in various parts of the world. There is some concern that the small initial numbers of individuals involved is now resulting in inbreeding depression problems in some captive populations. Birdlife International recommends establishing a new population on a suitable island to increase chances of species survival and this recommendation has been investigated by U.S. Geological Survey researchers. This idea has been bolstered by the finding using paleontologic evidence that Laysan Ducks once occurred throughout the Hawaiian Islands.
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/states/hi/
The Endangered Species Act has helped protect the Laysan 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://www.audubon.org/campaign/ 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/
The Hawaiian Islands National Wildlife Refuge provides essential habitat for the Laysan Duck, and a great number of other species. Unfortunately, the refuge system is often under-funded during the U.S. government's budgeting process. To learn more about how you can help gain much needed funding for U.S. National Wildlife Refuges, visit: http://www.audubon.org/campaign/refuge_report/
Birdlife International. 2000. Threatened Birds of the World. Lynx Edicions, Barcelona.
BirdLife International (2006) Species factsheet: Anas laysanensis, Laysan Duck http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=437&m=0
Ehrlich, P.R., Dobkin, D.S., and D. Wheye. 1992. Birds in Jeopardy. Stanford University, Stanford, CA.
Moulton, D.W. and A. P. Marshall. 1996. Laysan Duck (Anas laysanensis). In The Birds of North America, No. 242 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.
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.