Laysan duck  (Anas laysanensis)

Classified as Critically Endangered (CR) on the IUCN Red List (1), and listed on Appendix I of CITES (3).

The Laysan duck, so-called as it occurs on the Hawaiian island of Laysan, currently has the most restricted range of any duck in the world (4). It is a small, dark duck with orange legs and a prominent white eye-ring. The amount of white around the eye and on the head varies between individuals, and some adult males also have a slight green iridescence to the dark head. The rest of the plumage is dark reddish brown plumage, heavily mottled dark brown, and an iridescent patch of colour on the wings, (the speculum) appears teal green, or blue. Male Laysan ducks have dark green bills, while the female’s is brownish-pale (5) (6).

The Laysan duck, also known as the Laysan teal, is endemic to the Hawaiian Islands, USA. It was once widespread in the Hawaiian Islands, but for the last 150 years, has been restricted to just Laysan Island (7) (8). In 2004 and 2005, a number of Laysan ducks were translocated to two islands of the Midway Atoll National Wildlife Refuge (9).

The Laysan duck selects different habitats during different times of the day. Most adult birds use dense cover and hide in the terrestrial vegetation during the day, while during the evening and at night, it can be found in the central hypersaline lake on Laysan. It favours areas in the lake near freshwater seeps around the shore, especially when raising young ducklings, which are less tolerant of hypersaline conditions. It nests and rests in dense stands of shrubs and grasses (10).

Laysan ducks fly when they wish to each more remote parts of the island, but otherwise, they spending much of their time walking or running along the ground. They rest at midday and begin to feed during the evening and night (11). Laysan ducks feeds principally on brine flies, shrimps, and other invertebrates such as insect larvae and moths, but it also consumes grass seeds, sedge seeds and some algae (12). They have a novel way of catching brine flies; individuals run through swarms of these flies with their bills open and necks stretched out, attempting to trap the flies in the beak (11).

The breeding season of the Laysan duck extends from autumn to spring, (typically April through June) (4). Copulation occurs on land or in water, and the female then builds a nest in dense grasses, where four eggs are usually laid (4) (11).

The limited range and small, single population of the Laysan duck is the greatest ultimate threat to this species’ survival at present, as it makes it is extremely vulnerable to chance events such as disease or severe weather (4). Introduced species are a potential threat to the species persistence; while mammalian predators are not currently a problem on Laysan Island, there is nothing to prevent an accidental introduction and there are no measures in place to deal with the event should it occur (6). Many non-native invertebrates have arrived on Laysan, and while not all are impacting the Laysan duck, some, (such as ants), are possibly affecting the Laysan duck’s food supply as they compete for their terrestrial prey (4). An introduced grass, Cenchrus echinatus, encroached on the native bunchgrass (Eragrostis variabilis) on Laysan Island, reducing important breeding habitat, but this noxious weed was thankfully eradicated from the island (13). Infection with the parasitic nematode worm, Echinuria uncinata, is causing problems for the Laysan duck’s precariously small population (2), and global sea level rise poses a constant threat to all species on the low-lying island of Laysan (4).

The Laysan duck is listed under Appendix I of the Convention on International Trade in Endangered Species (CITES) and so international trade in this species is under tight control (3). Furthermore, Laysan Island and Midway Atoll are under the protection of the United States Fish and Wildlife Service as they are both National Wildlife Refuges (14), and whilst there are no measures to prevent an accidental species introduction, (for example via a ship wreck or unauthorised landing), Laysan Island has a quarantine for authorised visitors (6). Conservation action that has taken place to date includes the eradication of the introduced grass, Cenchrus echinatus (13), as well as the control of other alien plant species that threaten Laysan’s wetlands (Pluchea indica) on Laysan Island, and the successful translocation of wild Laysan Ducks to Midway Atoll National Wildlife Refuge. The translocated ducks have bred successfully, creating an ‘insurance’ population which will reduce the chances of a catastrophic event wiping out the entire species, since it is unlikely that a disaster would strike two islands simultaneously (15).

Proposed future actions include reintroducing the species to other Hawaiian islands (15), restoring or enhancing limited freshwater brood rearing habitat, along with stabilising dunes by planting vegetation, and preventing the accidental introduction of competitor and predator species, particularly new ant species and rats (2). Habitat restoration and introduced predator removal on additional islands with higher elevations are needed since Midway Atoll and Laysan Island are low lying. The Island of Kahoolawe has been proposed as a good site for reintroduction and habitat restoration (6).

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on the Laysan duck see:

• US Fish and Wildlife Service:
  www.fws.gov/Pacific/ecoservices/endangered/recovery/LaysanDuckTeam.htm
• USGS Pacific Island Ecosystem Research Center:
  http://biology.usgs.gov/pierc/Native_Birds/Laysan_ducks.htm
• USFWS (2004) Draft Revised Recovery Plan for the Laysan Duck (Anas laysanensis). U.S. Fish and Wildlife Service, Portland, Oregon.

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org