Laysan duck  (Anas laysanensis)

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).