Wednesday, April 9, 2008

Laysan teals ascendant at Midway

They say there are more Irish in America than in Ireland.
Same thing could happen with Laysan teal on Midway.
(Photos: Top, an adult Laysan teal flaps at the ocean's edge at Midway Atoll. Credit: USGS photo by Jimmy Breeden. Bottom, Michelle Reynolds, Jimmy Breeden and Matt Brown inspect a teal's leg band at Midway. Credit: USFWS photo by Pete Leary.)
This small native duck, once well distributed throughout the Hawaiian archipelago, until recently had its only surviving wild population on the island that gives it its name—Laysan, a sandy island in the middle of the Papahānaumokuākea Marine National Monument that has a central super-salty lake and several small fresh-water seeps.
In 2004 conservation scientists moved a flock of the ducks or teals from Laysan to Midway, where several shallow ponds had been dug to support the birds. The goal was to protect the species from extinction by a natural catastrophe that might destroy the Laysan population.
Nobody anticipated how well the birds, whose scientific name is Anas laysanensis, would take to their new home.
Forty-two birds were translocated. Within two years, there were more than 100 of them. By 2007, the third year, the population was up to 200.
“If this growth rate continues, the size of the Midway population could surpass the source population before 2010,” says a paper in the Zoological Society of London's journal, Animal Conservation. It is entitled “Translocation and early post-release demography of endangered Laysan teal.”
The paper was jointly produced by representatives of the U.S. Geological Survey's Pacific Islands Ecosystem Research Center, the Hawai'i Cooperative Studies Unit, and the U.S Fish and Wildlife Service. The authors are Michelle Reynolds, Nathaniel Seavy, Mark Vekasy, John Klavitter and Leona Laniawe.
The project's organizers recognize that moving the birds from one isolated low island to another isolated low island a few hundred miles away isn't perfect protection, but it's something.
“Like Laysan's, Midway's population is vulnerable to catastrophes such as tsunamis, hurricanes, accidental introduction of rats or other predators and disease. However, with the exception of global sea level rise, it is unlikely that disasters will strike both atolls simultaneously. Thus, two populations provide some degree of insurance against catastrophic events,” the authors said.
At Midway, the birds showed that they are fully capable of thriving in new locations, and will adapt to new environments, taking advantage of new foraging opportunities. But they do need some fresh water—primarily for the chicks—some vegetative cover and enough food to eat.
But the success at Midway doesn't mean the movement of Laysan ducks is easy. They disappeared from all the other islands where they existed, in the face of habitat change, predators and other problems.
And a previous attempt at relocation failed. That involved the 1967 movement of birds to Pearl and Hermes Atoll, just to the southeast of Midway. Those birds died in a year.
What happened at Pearl and Hermes, an atoll with very small sandy islets that can be quite bare, may have been the result of an absolutely inadequate habitat for the birds.
“We suspect that the small number of founders, limited land area and low elevation susceptible to storm surge, plus the marginal habitat contributed to the disappearance of Laysan teal translocated to Southeast Island of Pearl and Hermes Atoll in 1967-1968,” the authors wrote.
Researchers hope to move other populations of the ducks to other islands, to further protect the species. The Midway experiment suggests that as long as there's fresh water, cover and enough food, in the absence of predators, they should do fine.
© 2008 Jan W. TenBruggencate