US most endangered duck, Laysan duck, breeding success
13/01/2007 00:00:00Laysan duck
- Translocation has emerged as a key conservation tool in the recovery of endangered species on islands. It has been especially useful for restoring species where they formerly occurred after introduced predators have been removed or damaged habitats have been repaired.
- The Laysan duck was listed as endangered in 1967 because of its small population size (less than 500 birds), small geographic range (approx. 4 sq. km), and dependence upon a fragile ecosystem.
- Laysan ducks are small with multicoloured brown feathers, a white eye-ring, and orange legs and feet. Most active at night, the birds are famous for their interesting foraging behaviour, a ‘fly chasing sprint’ across the mudflat in Laysan Island’s interior. The ducks are primarily insect feeders, but also feed on seeds. The females hide their nests in dense vegetation and care for ducklings that can walk and feed the day of hatching.
- The effort to establish a second population on Midway Atoll NWR has been a collaborative effort led by the U.S. Geological Survey’s Pacific Island Ecosystems Research Centre and the U.S. Fish and Wildlife Service. This collaborative effort is a model for application of research for species recovery. The research should provide excellent information for how to further increase the Laysan duck’s population and distribution, and may serve as the model for translocations of other species. The non-profit groups, National Fish and Wildlife Foundation, Friends of Midway, and the U.K.’s Wildfowl and Wetland Trust have provided research and conservation support to the agencies.
- Until 1995, the Laysan Duck was believed to be endemic – that is, found nowhere else – to its namesake atoll, Laysan Island, but in 1995 bones found on many of the islands revealed that the duck probably inhabited all of the island chain. The species’ disappearance from the main Hawaiian Islands was most likely due to the introduction of rats. Introduced mammalian predators (such as rats and mongoose) may be the most important factor preventing successful reintroduction of the Laysan duck to other sites. The Hawaiian duck, koloa maoli (Anas wyvilliana), is the only other endemic duck species still found in Hawaii
Beginning in 2004, 42 ducks were reintroduced to the NWR as an experimental conservation action to increase the rare duck's geographic distribution, and to reduce its risk of extinction. With the translocated population more than doubling in just 2 years, researchers are now optimistic that the project will help contribute to the long-term survival for the nation's most endangered duck species.
‘These island teal do not migrate or disperse from Laysan Island, so we translocated birds by ship to restore the species to a larger range’ explained USGS field biologist Mark Vekasy. Now, Laysan ducks are found on 3 islands for the first time in hundreds of years, and are flying between two islands at Midway Atoll.
The re-establishment of a second or ‘insurance’ population at Midway Atoll reduces the risk of extinction from a catastrophe striking Laysan Island, also part of the Hawaiian Islands NWR. The effects of a hurricane, tsunami, new diseases (like avian flu), or the accidental introductions of harmful plants and animals could easily cause the extinction of Laysan duck since they occurred as a single, small population.
‘Biologists have monitored 38 nests with radio telemetry this year, and we are observing interesting differences in reproductive effort between the source (Laysan) and Midway populations’, said Dr. Michelle Reynolds, USGS, Project Leader for the translocation. The translocated ducks are breeding at an earlier age, and are laying more eggs than ducks observed on Laysan, suggesting that the food or habitat on Laysan Island is limited. In contrast, Midway Atoll, with its relatively low-density duck population, has abundant habitat and food available, possibly stimulating greater reproductive effort.
‘The breeding response of the ducks to the restored habitat at Midway affirms the hard work that the USGS, the US Fish and Wildlife Service and volunteers have put into this project,’ said Reynolds.
