Endangered Laysan ducks born at the Midway Atoll National Wildlife Refuge last year are now hatching ducklings of their own, marking the latest milestone in a program to save the nation's rarest native waterfowl.

The newest additions, hatched last week, are the second generation of ducks to be born on Midway after a founding group of 42 birds was moved from Laysan Island in 2004 and 2005.

"We didn't even expect breeding the first year, and they surprised us, and then we thought it would take maybe a year or two for the first generation to nest. It's exciting," refuge biologist John Klavitter said.

Earlier breeding and larger egg clutches by the Midway birds are likely due to less density in the duck population and abundant food and habitat, he said.

"There are fewer ducks, so there's no competition between them and unlimited resources for nesting and foraging," Klavitter said.

The Laysan duck, also known as the Laysan teal, was once widespread across the Hawaiian Islands. By 1857, the birds existed only on 1,000-acre Laysan Island, about 1,250 miles northwest of Honolulu. Slaughter by guano miners and an infestation of rabbits that devastated vegetation left only 11 ducks on the island by 1911.

The species suffered another brush with extinction in 1993, when drought and disease dropped the population to just 50 birds. Today, there are an estimated 600 ducks on Laysan Island.

Federal wildlife officials moved the wild ducks to the Midway refuge after extensive preparation that included creating shallow freshwater seeps and planting native vegetation to provide cover, forage and nesting habitat. Eleven first-generation ducklings survived last year, and two nested this year, producing a total of five offspring.

Federal wildlife biologists report that at least 25 ducklings from eight mothers have hatched this year, and five other ducks are incubating eggs. Not counting the hatchlings, there are 35 Laysan ducks on Midway's Sand Island and 16 on the atoll's Eastern Island.

Klavitter said the Midway birds are laying twice as many eggs as their Laysan cousins, which produce 3.4 eggs per nest.

In addition to observing the ducks' breeding habits, scientists are using radio transmitters to study what kind of habitat they prefer, how far they are ranging from their release site and other behavior.

Since Laysan ducks have no predators and don't migrate, the birds are not strong fliers. "Their life strategy is to stay put," Klavitter said. But last fall, three of the ducks flew about two miles from Sand Island to Eastern Island, visiting for anywhere from a few hours to several days.

"We weren't really expecting that," he said.

Biologists are looking at starting Laysan duck populations on Lisianski Island and Kure Atoll in the next few years.

A potential threat to the success of the relocation program is avian flu, which could arrive via migratory birds returning from Arctic breeding grounds. Klavitter said wildlife biologists at the Midway refuge will be participating in a nationwide migratory bird monitoring program to watch for the disease.

The relocation effort at Midway is led by the U.S. Geological Survey's Pacific Island Ecosystems Research Center and the U.S. Fish and Wildlife Service, with grants and other support provided by the National Fish and Wildlife Foundation, the Friends of Midway Atoll and Britain's Wildfowl and Wetland Trust.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.