Posted on: Friday, July 1, 2005
Laysan ducks spreading wings on Midway Atoll
By Jan TenBruggencate
Advertiser Science Writer
Laysan ducks are staging a stunning population explosion on Midway Atoll's Sand Island, where five of six female birds nested this season and three so far have produced 13 surviving chicks.
Two more females are still sitting on eggs, and based on the earlier results this season, they could double the island's duck population in its first nesting season.
Wildlife biologists are cautious but ecstatic about the activity. Twenty of the endangered ducks, also called Laysan teal, were shipped to the Midway Atoll National Wildlife Refuge, 1,250 miles northwest of Honolulu, eight months ago from their home island to create a backup population in case the ducks on Laysan are destroyed by storm, alien predators or some other disaster.
The transplanted birds were only 2 to 3 months old. Researchers knew they were unlikely to mate and nest until mid-2006, but the ducks surprised them.
"On Laysan, they almost never nest until their second year," said Michelle Reynolds, conservation biologist with the U.S. Geological Survey's Pacific Islands Ecosystem Research Center. Additionally, each nest contained nine to 10 eggs, compared with the three to four eggs normally found in Laysan nests.
The Midway Duck Translocation Project started eight years ago, when scientists began looking for a way to ensure that a passing hurricane or tsunami did not wipe out the species on low, sandy Laysan.
Not long before that, new fossil evidence showed there once had been Laysan ducks throughout the Hawaiian archipelago and in many different habitats.
The birds survived on isolated Laysan and Lisianski in the Northwestern Hawaiian Islands, but disappeared on Lisianski a century ago when rabbits denuded the island and sandstorms filled its only lake. Laysan's salty lake survives, along with a few freshwater seeps that ducklings need to survive. But the habitat is limited. Reynolds said Laysan's carrying capacity may be no more than 600 birds, and in dry years, few ducklings survive due to lack of fresh water and food.
Midway, where rats were exterminated in the 1990s, was identified as a potential new home for the birds. Conservation crews dug a series of shallow ponds that reached fresh water. A sedge called makaloa, favored by Laysan's ducks, was brought to Midway and planted. The crew of the Hokule'a voyaging canoe brought some makaloa to Midway during its sail through the archipelago last year, and another batch was brought by a research ship.
Reynolds said it's difficult to judge the sex of ducklings, and last year's flock ended up being 14 males and six females. One male died in an attack by an albatross, but 19 birds are alive.
First-year nesting females often have trouble nesting and raising their young. The first nest on Midway produced just a single duckling that died after a few days. But that female produced a new clutch and is sitting on at least five eggs, Reynolds said.
Duck researchers, seeking to increase the potential genetic diversity of the population, hope to bring 30 young ducks to Midway this year. Field biologist Jimmy Breeden is watching this year's nests on Laysan to select the young birds that will join their Midway cousins.
The Midway ducks are being cared for by U.S. Fish and Wildlife Service refuge biologist John Klavitter and U.S. Geological Survey biologists Mark Vekasy and Leona Laniawe.
Scientists already are looking into further sites for re-establishing the animals. They plan later to put ducks on Eastern Island within Midway Atoll, where two ponds have been dug and makaloa has been established.
Another favored site for translocation of ducks is Lisianski, the sandy island 140 miles west of Laysan and the last place the birds naturally occurred other than Laysan itself.
