Laysan Duck. Photo: Wikipedia.com

More than 120 endangered Laysan Ducks were found dead on Midway Atoll National Wildlife Refuge this August, a big setback for this critically endangered species. Although no definitive cause has yet been identified, avian botulism is suspected.

The endangered Laysan Duck is considered the rarest native waterfowl in the United States and occurs only within the Papahanaumokuakea Marine National Monument in the Northwestern Hawaiian Islands. The species was once widespread across the Hawaii, but by 1860, it had vanished from everywhere but Laysan Island.

Thanks to intensive restoration efforts, including translocations in 2004 and 2005 of birds to Midway, the species has made significant progress. The original Laysan Island population now numbers around 600 ducks, and the Midway population was estimated at 200 birds in December 2007. Successful fledging this year almost doubled that population (Bird Calls, Vol. 12, No. 2), making this latest development a particularly hard blow.

Wildlife officials have added large amounts of freshwater to the areas where the dead birds were found to reduce water stagnation, a factor that causes certain bacteria to produce the toxin which causes avian botulism. For more information, visit http://biology.usgs.gov/pierc/Native_Birds/Laysan_ducks.htm.