Wildlife officials have released 22 endangered Laysan ducks on Midway Atoll in the second year of an effort to establish a permanent wild breeding population on an island other than the one from which they get their name.

The birds, sometimes called Laysan teal, are the most rare waterfowl in the northern hemisphere, and the effort to establish a second home for them is designed to ensure that a one-island catastrophe doesn't drive the species extinct.

Biologists dug ponds on Midway and planted them with native species the birds are known to use, in preparation for the arrival of the first group of young birds last year. More than 10,000 hours of work were done to prepare the island, all under the direction of Midway Atoll National Wildlife Refuge biologist John Klavitter. The first group of ducks has bred actively, growing from 20 individuals to 33.

"This critical second translocation will allow us to double the founding population at Midway, improve the sex ratio, and release birds in newly restored habitat on (Midway's) Eastern Island," said Michelle Reynolds, project leader for the Laysan duck translocation.

This year's birds were healthy, young animals collected Oct. 4 at Laysan. They were carried to Laysan on the motor vessel American Islander, where they were cared for by veterinarian Thierry Work. They arrived at Midway on Oct. 7, where they were observed in aviaries before being released during the middle of October.

Sixteen birds were released on Eastern Island and six on Sand Island, where last year's birds are. Because the first-year Sand Island population has more males than females, the team released five females and just one male on Sand Island.

The translocation project is a joint effort of the U.S. Fish and Wildlife Service, the U.S. Geological Survey's Pacific Island Ecosystem Research Center, the state Division of Forestry and Wildlife, the National Fish and Wildlife Foundation, and the British Wildfowl and Wetlands Trust.

For bird lovers, a project to restore an extremely rare population to the wild is a big deal.

"I never imagined I'd see free-living Laysan teal. It has been a highlight of my career to help ensure this species will continue to exist," said Nigel Jarrett, an aviculturist for the Wildfowl and Wetlands Trust, who has been camping on Eastern Island with colleague Jimmy Breeden, monitoring the ducks.

They report that all the released ducks, which are fitted with transmitters so they can be tracked, appear to be swimming and foraging normally.

Fossil records show that Laysan ducks were once found on most of the Hawaiian islands, including the main Islands. They disappeared from islands where rats were introduced, but survived on Laysan, which remained rat-free. In 1911, when rabbits on Laysan denuded the island, the duck population dropped to an all-time low of 11 birds. The rabbits were removed, and the ducks now number about 500 there.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.