The endangered Hawaiian duck, or koloa, the only remaining endemic duck on major Hawaiian islands, is threatened with genetic extinction due to crossing with wild mallards. This led to the creation of hybrid forms of koloa. But new research has found that the genetic diversity of koloa is high and conservation efforts on Kauai Island have been successful.
Caitlin Wells, a Colorado State University scientist, conducted the research as a postdoctoral fellow at the University of California, Davis. This study is the culmination of two decades of research led by scientists at the University of California, Davis; US Fisheries and Wildlife Service; University of Texas, El Paso; Wright State University; Oregon State University; and the state of Hawaii's Forestry and Wildlife Division.
The study results offer hope for existing conservation efforts with koloa and other endangered birds worldwide.
"The persistence of an endangered native duck, wild mallard and several hybrid swarms on major Hawaiian islands" will be published Nov. 18 in Molecular Ecology, and Wells is the lead author.
A charismatic duck, located mainly on Kauai
Wells described the koloa as a "small charismatic brown duck", similar to a female mallard duck.
"The fact that koloa on Kauai is pure and has a lot of genetic variation are two really positive things that came up in this study," said Wells.
Andy Engilis, co-author of the study and curator of the UC Davis Museum of Wildlife and Fish Biology, said this study is critical in the fight to save the koloa from extinction. He has been involved in Hawaiian duck conservation and research efforts since the late 1980s.
"This study lays the groundwork for a new chapter in koloa recovery, a new trajectory of recovery and exclusion of endangered species," he said.
Kimberly Uyehara, a biologist at the Kauai National Wildlife Refuge Complex and co-author of the study, said the results were significant.
"They open new doors to the field of possible koloa recovery actions," she explained.
The largest population of koloa is on Kauai, where the team found very few hybrid birds. On the other islands, however, all birds were hybrids or wild teals.
Historically, koloa existed on major Hawaiian islands, but disappeared from all islands except Kauai and Niihau in the late 1960s due to habitat loss, predator introduction and unregulated hunting. Soon after, wildlife managers began setting up captive breeding programs on Oahu, Hawaii, and Maui to reestablish koloa. Unfortunately, the mallards were never removed on these islands, resulting in rapid hybridization.
This research study was conducted, in part, to determine the genetic composition of koloa in Kauai. Previously, wildlife managers and conservationists raised concerns that even the Kauai refuges contained hybrid ducks.
The research project involved a huge bird bandage project
The research team studied 425 koloa, mallards and hybrids of Hawaiian island populations, gathering more than 3,300 bird genetic data points. The project involved a huge bird bandage project, led by collaborators from the State of Oregon and the Hanalei National Wildlife Refuge. Team members collected blood samples from hundreds of birds before releasing them back into the wild.
The researchers also collected genetic data from koloa carcasses recovered after botulism outbreaks, particularly in the Kauai population. All specimens and samples are archived at the UC Davis Davis Museum of Wildlife and Fish Biology.
"We used many tissue samples from rescued birds that unfortunately died from these disease outbreaks," said Wells.
Previously, wildlife managers had thought that if they left the koloa hybrids alone, the birds would eventually return to pure koloa on their own.
"That's not what we found out," Wells explained. "If you don't have pure koloa parents that outnumber wild mallards, you won't have reductions in those hybrid proportions."
Why preserve koloa?
The recovery of endangered koloa is important because the bird is endemic to the Hawaiian Islands.
"Their recovery can be seen as a beacon of hope for the many dozens of critically endangered birds found on the islands," said Engilis. Researchers also point out that their recovery is important because of their unique evolutionary history.
"If the environment changes due to climate change, there is a lot of potential for koloa to evolve on its own, given the genetic diversity we have seen," said Wells.
Species hybridization is a complicated conservation issue. Sometimes it can threaten an animal's unique gene pool that is well adapted to its environment. In other cases, where a species is inbred, it may be the right move to add more genetic diversity to a population.
"But here is a case where we have enough individuals with sufficient genetic variation in koloa and we also genetically identify hybridizing species," she said. "It seems very clear that we can separate those going forward."
What follows for koloa conservation
Wells said the team's research provides insight into successful conservation management and the ability to recover this species.
"These efforts may one day lead to koloa being removed from the endangered species list," she said.
Additional study co-authors include Philip Lavretsky (University of Texas at El Paso), Jeffrey Peters (Wright State University), Jeffrey DaCosta (Boston College), Michael Sorenson (Boston University), Stephen Turnbull (US Department of Land). Hawaii) and Natural Resources), Christopher Malachowski and Bruce Dugger (Oregon State University) and John Eadie (University of California, Davis).