Tuesday, May 19, 2015

Native Hawaiian ducks repopulating the island chain

Okay, not much cuter than a mama duck and her ducklings.

Laysan ducks, the most geographically isolated duck species in the world, has now leapfrogged across the Hawaiian archipelago, from its Laysan home to Midway in 2004 and last year to Kure Atoll.

(Image: Laysan duck and her clutch. Credit: DLNR.)

Laysan ducks, Anas laysanensis, which are sometimes called Laysan teals, were once found throughout the Hawaiian Islands, up and down the chain from the high islands to the tiny atolls to the northwest. 

But under pressure from humans, other predators like rats, habitat loss and other issues, they finally were only present on Laysan. Laysan is a sandy island with a central marsh that’s located about halfway up the archipelago from Kauai to Kure.

The species is currently the rarest species of duck in the northern hemisphere, with the smallest range of any 

In 1911, under pressure from introduced predatory rats and from rabbits that ate much of the island’s vegetation, the population at Laysan was down to 20 birds. But with rabbit and rat removal, the population began expanding. 

Eventually, with numbers on Laysan at several hundred birds, wildlife officials felt the population was healthy enough to try to develop new populations. The risk of the entire population being on one small island was too great. 

The first move was to take a bunch of the birds and shift them to Midway, where wildlife officials are stationed and could keep an eye on them. 

And here at RaisingIslands, we take some small credit for the survival of these birdies. We were aboard the voyaging canoe Hokule`a in 2004, before Laysan ducks were transplanted from Laysan to Midway. 

The crew of the canoe dug up plants of the native sedge, makaloa, which ducks particularly like. We transported the plants aboard the canoe as it sailed up the Hawaiian archipelago, and we delivered them to Midway, where they were planted alongside ponds dredged for the benefit of the ducks.

That original transplanting of ducks to Midway had its problems, from disease to tsunami, but 11 years later, the Midway flock of Laysan ducks is doing well. Here is a 2007 RaisingIslands post on the duck boom.

In 2008, a botulism outbreak killed many of the Northwestern Hawaiian Islands ducks, including a quarter of the Midway population.

Today, the population of Laysan ducks on Midway is in the neighborhood of 400 birds. They’re doing so well that 28 of the Midway birds were transplanted last year to Kure Atoll, the westernmost island in the Hawaiian archipelago. 

As occurred with Midway, the transfer followed the removal of rats, the digging of ponds and the transplanting of native plants to the island, to provide the ducks with the best habitat possible. 

The translocation was a joint project of the state Department of Land and Natural Resources' Division of Forestry and Wildlife, the U.S. Fish and Wildlife Service's National Wildlife Refuge System, the U.S. Geological Survey, Hawaii Wildlife Center, Kure Atoll Conservancy and Papahānaumokuākea Marine National Monument,. (The Monument is managed by the NOAA, USFWS, and the State of Hawai’i._

And the ducks have done well on Kure.

“We documented that all 28 founder birds translocated to Kure in the fall of 2014 had survived six months after their translocation and release,” said Cynthia Vanderlip, Kure Atoll state wildlife sanctuary manager. 

In the spring season of 2015 on Kure, the 28 birds produced 19 ducklings, bringing the population to more than 40—an auspicious beginning.

“Everyone working on this project to help save an endangered species is thrilled that this reintroduction may reduce extinction risk of this rare Hawaiian endemic duck. We all feel like proud parents,” Vanderlip said.

You can see a video of the ducks here.

Here is the state Department of Land and Natural Resources’ press release on the ducks and ducklings. 

© Jan TenBruggencate 2015

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