JIM WATT / NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION / 2000 Laysan ducks were found dead recently on Midway Atoll.

Rare ducks found dead on Midway Atoll

Wildlife officials are investigating the deaths of more than 100 endangered Laysan ducks at Midway Atoll in the Papahanaumokuakea National Wildlife Monument.

The first dead duck was discovered on Aug. 10 and as of yesterday 106 adult and adolescent bird carcasses were found, according to a news release from the U.S. Fish and Wildlife Service.

No definitive cause has been identified, but officials suspect avian botulism.

"Although we suspect avian botulism, we will not have a confirmed diagnosis" until this week, Matt Brown, acting refuge manager at Midway, said in a news release.

A number of duck carcasses were shipped to the National Wildlife Health Center Honolulu Field Station for further analysis yesterday. Samples will also be sent to the National Wildlife Health Center in Wisconsin to confirm whether avian botulism is a cause of the die-off.

Wildlife officials have added large amounts of fresh water to the areas where the dead birds were found to reduce water stagnation. The carcasses are also being collected and burned to reduce further spread of potential disease.

Avian botulism is caused by a bacteria that produces a toxin when certain conditions, such as stagnant water, warm temperatures and decaying vegetation, are present.

Birds are infected with the disease when they eat toxin-laden invertebrates. While the invertebrates are immune to the toxin, botulism affects the birds, paralyzing their voluntary muscles and leading to drowning or asphyxiation.

The disease is not a threat to humans.

The Laysan duck population at Midway was estimated at 200 birds in December, but has since nearly doubled after a successful fledging.

The remaining population on Laysan Island is about 600 ducks.

"We are naturally upset by this loss which further underscores the need to have Laysan ducks at more than one location in the Hawaiian Islands," Brown said. "We sincerely hope we have seen the worst of this outbreak, and that our Midway population of Laysan ducks will rebound quickly."

The endangered Laysan duck is considered the rarest native waterfowl in the United States and lives only within the Northwestern Hawaiian Islands' Papahanaumokuakea Marine National Monument.