The Laysan duck (Anas laysanensis), also known as the Laysan teal, is a dabbling duck endemic to the Hawaiian Islands. Fossil evidence reveals that Laysan ducks once lived across the entire archipelago, but today survive only on Laysan Island. The duck has evolved several behavioral traits linked to the absence of ground-based predators in its habitat; these include freezing or running to escape danger rather than flying, which made the duck vulnerable to hunting by humans, and the pigs, rats and mongooses they brought with them to Hawaii. By 1860, the ducks had disappeared from everywhere except Laysan Island. The introduction of rabbits brought the bird to the brink of extinction in 1912 with twelve surviving individuals. Rabbits were eradicated from the island in 1923 and numbers of Laysan ducks began to rise, reaching 500 by the 1950s. In an effort to ensure the long-term future of this duck, 42 birds were translocated to Midway Atoll National Wildlife Refuge in 2002. These thrived in their new surroundings, and another group were later relocated to Kure Atoll.
The Laysan duck is teal-sized and dark brown, with a prominent white eye-ring. The bill is short and spatulate, dark green with variable black blotching in males, and dull orange with variable black blotching in females. The Laysan duck usually has a ring of fat around its neck. Some males show faint iridescence on the head or neck and have slightly upturned central tail feathers. The wing has an iridescent purplish-green patch (speculum feathers) in both sexes. Leucistism, or extensive white feathering, is common on the head and neck of older birds. The legs and feet are orange, usually brighter in the male. The annual pre-basic molt is complete, and the ducks lose all their flight feathers and become incapable of flight until new feathers grow in. Wild ducks have been known to live to the age of twelve years, and captive birds have lived to the age of eighteen.
Pair formation begins in fall, and nest building begins in spring. The female builds a well-concealed nest on the ground below dense vegetation, especially Eragrostis variabilis bunchgrass. The nest is a shallow bowl lined with dead grass and down feathers. Egg-laying typically occurs from April to August. Average clutch size on Laysan Island is approximately four eggs. The newly established population on Midway lays larger clutches, presumably because of better availability of food. Ducklings are precocious and feed on their own day two after hatching, but are guarded, brooded, and led to foraging sites by the hen for approximately 40 to 60 days.