WatchList Species Account for Laysan Duck (Anas laysanensis)

Qualifies for the list as a Red List Species

Laysan Duck. Photo: Wikipedia.com

The Laysan Duck, now limited to Laysan Island but which according to subfossil evidence once inhabited many of the main Hawaiian Islands, has the most restricted distribution of any living duck. Laysan Island is only about 370 ha in size, including vegetated and unvegetated areas and a central hypersaline lake which furnishes the duck its invertebrate diet. In the early 20th Century, introduced European rabbits almost completely destroyed the island’s endemic vegetation, causing three or four of the island’s endemics to become extinct and bringing the duck to the brink of extinction. After the rabbits starved to death, the island revegetated and the duck recovered.

Another less serious population decline occurred in 1993-94, apparently due to a drought, a decline in brine flies, and a suspected outbreak of a nematode parasite. The bird is long-lived and has a low reproductive rate. Though able to fly, it is more likely to walk, especially when pursuing brine flies. Brine shrimp also inhabit the central lake. The bird’s need for freshwater is supplied by seeps. Population size is about 500 individuals. Another endangered species, the Laysan Finch, preys on the eggs of the duck. The island is open to human visitation only for official or scientific purposes. A management need is the stabilization of dunes and vegetation to keep the lake from filling up with blowing sand, since the ducks are totally dependent on the lake for their existence.