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Anas laysanensisLaysan duck

By Peter Herbst

Geographic Range

The Laysan Duck originally resided along all of the Hawaiian archipelago but within the past two hundred years has found its range greatly diminished. At the current time the Laysan Duck can only be found on the small, 900-acre, island (Laysan Island) that is under the protection of the US Fish and Wildlife Service.

Habitat

Grouped among the Dabbling ducks such as the Mallard, the Laysan Duck prefers land habitats to aquatic and aerial habitats. The Laysan Duck is normally observed along the coast of Laysan Island or around the inland lake found on the island. This is where they reside year round. Studies of DNA in duck bones throughout the Hawaiian Islands have shown that the Laysan Duck's range once included the entire Hawaiian Archipelago before the mass extinctions that occurred in that region after Polynesian colonization between 400 and 600 AD.

Physical Description

Average weights for this long-lived duck vary with its age. An individual at age 14 can weigh 98.1 grams while an individual at age 45 can weigh 402.0 grams. There is little difference between the plumages of males and females. Both are dull, dark brown with distinctive white eye rings and white feathering on head and neck. The main difference lies with bill coloring: the male bill is yellowish green with black spotting, while the female bill is dull orange. The Laysan Duck has strong wings that allow it quick take offs but not prolonged flight. The Laysan Duck spends most of its time on its legs dabbling into the water and on land for food.

  • Range mass
    98 to 402 g
    3.45 to 14.17 oz

Reproduction

Copulation occurs on land during the late fall and winter. Nesting occurs after this with the female building a nest in a well-concealed location. Four eggs are laid usually between April and August but sometimes as early as February and as late as November. The species' overall success has been diminished by human intrusions especially because its reproductive rate is naturally low. Organizations that wish to increase the duck's population size are currently breeding the ducks in captivity.

  • Average eggs per season
    4

Lifespan/Longevity

Behavior

The Laysan Duck is rarely observed swimming or flying and spends about 10 percent of its time each day walking or running on the ground. During midday the ducks rest and they come out to feed on the island's highlands during the evening and night. Vocalizations are similar to that of a mallard but are rarely heard except during courtship. Male ducks fighting for mates are observed pulling at each other's breast feathers.

Communication and Perception

Food Habits

The main food staple for this species is macroinvertebrates. The Laysan Duck is not a diver or swimmer and merely dips its head into the water to feed on aquatic plants, seeds and snails. They also do some filter feeding for moth larvae and pupae. A peculiar method of feeding that has been observed in this species is its tendency to run through swarms of adult brine flies with its neck extend and mouth open in order to trap the flies in its mouth. The climate in the Pacific Ocean undergoes little seasonal variation and therefore migration by this duck to follow food is unnecessary, as supplies stay constant year round.

Economic Importance for Humans: Negative

Their refuge is an area of high economic value to developers.

Conservation Status

The population bottomed at 150 recently in 1993 following a drought in the region. Their present numbers are up to 600, which is considered a success on the part of the US Fish and Wildlife Service. Currently the Laysan Island is now a refuge for these birds, but has been maintained loosely as a Bird Sanctuary since 1909.

Contributors

Peter Herbst (author), University of Michigan-Ann Arbor.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

visual

uses sight to communicate

References

Browne, Robert A, Curtice R. Griffin, Paul R. Chang, Mark Hubley and Amy E. Martin. 1993. Genetic Divergence among populations of the Hawaiian Duck, Laysan Duck and Mallard. The Auk 110(1). Washington D.C. 1993 p. 49-56.

Laysan Duck: Species Profile. http://www.tnc.org/infield/species/oldprofiles/lasanduck/laysanduck.htm. 10/20/97.

Exploring with New Technologies http://www.consci.tnc.org/library/pubs/rptcard/duck.htm. 10/20/97.

Moulton, Daniel W. and Ann P. Marshall. 1996. Anas laysanensis: Laysan Duck. The Birds of North America No. 242.

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