|
|
Laysan Duck Translocation Project November 23, 2004 The residents of Midway Atoll National Wildlife Refuge are always happy to have newcomers to their island, but now they have some very special residents. Twenty endangered Laysan ducks are calling Midway their home. This landmark event, translocating birds to Midway, seeks to create a second wild population of Laysan ducks and is a high priority for the recovery of the species. |
|
The endangered Laysan duck (Anas laysanesis) had the smallest geographical range of any duck species in the world and until now consisted of a single population of approximately 500 birds on Laysan. The duck’s risk of extinction is very high as long as it is limited to a single population. The species’ disappearance from the main Hawaiian Islands was most likely due to the introduction of rats. Mammalian predators, such as mongooses, cats, and rats may be the most important limiting factor in the reintroduction of the duck to other sites. Rats were accidentally introduced to Midway during World War II, but were eliminated from the island in 1997 after the atoll became a National Wildlife Refuge. Midway Atoll NWR is located about 1,250 miles west-northwest of Honolulu. The five-mile diameter atoll was chosen as a reintroduction site because it lies within the presumed prehistoric range of the species, is free of rats and other predators, and provides the logistical feasibility for post-release monitoring of translocated ducks and for habitat restoration. A team of project scientists and managers from the U.S. Fish and Wildlife Service and the U.S. Geological Survey, Pacific Island Ecosystem Research Center, captured 27 birds on Laysan, and selected 20 of these birds to make the 2-day long boat ride to Midway. All personnel on the island worked through the night to capture the birds. The candidate ducks were selected after six months of monitoring. Those that made the trip were chosen based on weight, sex (relatively even male-female ratio), health, age, and family history (a single duckling from each brood). Removal of the 20 birds from Laysan Island was not deemed a threat to the health of that population. The birds were then transported on the “American Islander,” a vessel contracted by the FWS for transport of the ducks and to change out field crews on Laysan. Each bird had its own transport cage, and the ducks had their own private cabin aboard the vessel. During this critical step of the translocation phase, the birds were fed, watered, and treated by USGS veterinarian Dr. Thierry Work. The young ducks have adapted well to their new home on Midway, some have increased their body weights 10-20% since their capture on Laysan. |
 Photo © Susan Middleton 2004 |
FWS staff and volunteers at Midway Atoll NWR spent 18 months preparing the site for the arrival of the ducks. The first step in site preparation was the removal of nonnative ironwood trees and verbesina plants followed by the excavation of nine shallow freshwater seeps. In addition, 1,400 native bunch grass plants that are used by the ducks for nesting were planted at the site. Two separate aviaries were constructed using shade cloth and steel pipes. The aviaries have compartments measuring 100 square feet each. Two ducks occupied each compartment. |
|
Radio transmitters have been attached to each bird so that they can be easily tracked. The birds are being closely monitored with spotting scopes and radio telemetry to prevent disturbance. An additional translocation of 20-30 young ducks is planned for 2005. Laysan ducks are between 15 and 17 inches in length, are brown with a bright green-blue to purple speculum (the distinctive feathers on the secondary wing feathers), and have a white area eye ring. Males have a bluegreen bill with black spots along the upper mandible (bill). The female usually has more white around the head and neck, and has a dull brownish yellow bill. Both sexes have orange legs and feet. The ducks are primarily insect feeders, but may also feed on leaves and seeds.
|
