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Hawaiian Duck's Future Threatened by Feral Mallards

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Hawaiian Duck's Future Threatened by Feral Mallards Hawaiian Duck's Future Threatened by Feral Mallards early 70% of Hawai'i's native N bird species are found nowhere else on Earth, and many of these species are declining or in danger of extinction. Although the Hawaiian Islands were once home to a remarkable diversity of waterfowl, only three species remain-the Hawaiian Goose (Nene), Laysan Duck, and Hawaiian Duck (Koloa mao/i)-all Federally endangered. The Koloa mao/i is the only Hawaiian bird threatened by "genetic extinction" from hybridization with an invasive species-feral Mallard ducks. U.S. Geological Survey (USGS) biologists in Hawai'i are working to find the causes of bird A Hawaiian Duck drake or male from the Island of endangerment and ways to prevent Kaua'i (copyrighted photograph by J. Denny). The extinction of the Koloa mao/i and duck's name in Hawaiian is "Koloa maoli," meaning other threatened birds. "native duck," which distinguishes it from introduced ducks or migratory ducks such as Koloa mapu (Northern Pintail, A. acuta) or Koloa moM (Northern Shoveler, A. clypeata) that winter in the Hawaiian Islands. Inset shows 10-day-old Koloa maoli duckling The Federally endangered Hawaiian from Kaua'i (photograph courtesy of B. l aun). Duck (Anas wyvilliana) ("Koloa maoli" or simply "Koloa" in Hawaiian), is an farming, sport hunting, and pond beauti­ of Hawai 'i, Kaua 'i, and Ni 'ihau. However, endemic species (found nowhere else on fication, but it escaped into the wild and recent evidence shows that even these pop­ Earth) of the Hawaiian Islands. The great­ became "feral." ulations contain Mallard x Koloa hybrids. est current threat to the future of the Koloa Koloa were once common on the main The Koloa is a small dabbling duck is cross-breeding or "hybridization" with Hawaiian Islands. Until recently, scien­ similar in appearance to the Mallard but the introduced Mallard (A platyrlzync!ws). tists believed that more than 2,000 "true" genetically distinct and differing in size, The Mallard was brought to Hawai 'i for Koloa remained, primarily on the islands plumage, and behavior. The Koloa is a deeper, richer brown, more secretive, and about 20 to 30% smaller than the Mallard. The Koloa can be found from sea level to about I 0,000 feet elevation in a diversity of wetland habitats. Habitat-use studies reveal that, in addition to lowlands, the Koloa frequents mountain wetlands and skillfully maneuvers winding river cor­ ridors and forest canopy, where human activity is minimal. However, little else is The greatest threat to the future of the Koloa maoli as a unique species is cross-breeding with the introduced known about the breeding ecology, home Mallard duck (A. platyrhynchos). This photograph shows feral Mallards, including "barnyard ducks," at Wailoa range, movements, or population dynam­ River State Park on Hawai'i. (Photograph by K. Uyehara.) ics of this endangered duck. U.S. Department of the Interior USGS Fact Sheet 2007-3047 U.S. Geological Survey 2007 WHY IS CROSS-BREEDING WITH FERAL MALLARDS THE GREATEST THREAT TO THE FUTURE OF THE KOLOA? When a feral Mallard and a Koloa mate and produce fer­ tile offspring, cross-breeding or "hybridization" occurs. Studies by biologists from many cooperating organiza­ tions, including the U.S. Geological Survey, suggest that interbreeding among these hybrids, Mallards, and Koloa is leading to loss of the Koloa as a unique island species. KAUA'I O'AHU NI"IHAU c-,...,.. "'"" /C" oc-,.. ""'I-t- MAUl EXPLANATION KAHO'OLAWE Photo by A Engtlls D Areas where Koloas once I ived D Predominance of Koloa D Predominance of hybrids • Confirmed hybrids ? Status of hybridization uncertain 0 Jf. Confirmed Mallard female and Koloa male pair 0 100 KILOMETERS Current distribution of Koloa x Mallard hybrids on the main Hawaiian Islands (data from Engilis and others, 2002, and U.S. Fish and W1Jdlife Service). The Greatest Threats-Introduced Spe­ shown that feral Mallards are dominant of this, interbreeding among hybrids, cies and Hybridization ducks, adapted to survive and reproduce Mallards, and Koloa can over generations Introductions of nonnative species can in habitats with human introduced preda­ lead to loss of the Koloa as a unique is­ bring species together that were previ­ tors. They also are well adapted to using land species. ously geographically isolated and had habitats degraded by human activity. separate gene pools. This is particularly These factors may give feral Mallards a Mallards in Hawai'i a problem when "aggressive" introduced competitive edge over native ducks, such Mallard imports to Hawai 'i began in species, such as feral Mallards, come in as the Koloa. the late 1800s for stocking ornamen­ contact with rare native species. When a Mallard and Koloa mate, they tal ponds and farming. In the 1950s Studies in other parts of the world have produce fertile, hybrid offspring. Because and 1960s, hundreds of Mallards were imported from North American game appearance. Although the chances of a Resolving the Feral Mallard Dilemma in farms to stock some hunting areas in Koloa and barnyard duck directly hybrid­ Hawai'i the Hawaiian Islands. Unlike "resident" izing in the wild are very small, many Removing the feral Mallard threat in feral Mallards, which are thought to be scientists have raised concerns about the the Hawaiian Islands is recommended the descendants of such domestic stock, large numbers of abandoned domestic by the U.S. Fish and Wildlife Service's migratory Mallards that occasionally stop ducks found on public water bodies and (FWS) draft recovery plan for the Koloa. over or winter in the Hawaiian Islands are the possibilities that these ducks harbor However, even biologists have trouble rare, not in breeding condition, and do bird and human diseases. distinguishing between Koloa, feral Mal­ not pose a threat to Koloa. In the late I 980s, the Mallard was lards, and hybrids in the field, because In addition to the "true" Mallard, placed on the State of Hawai'i's List the size and plumage of hybrids can there are Mallard domestic breeds or of Restricted Animals for importation, vary greatly. To help with this problem, "barnyard ducks." They come in various which allows exceptions for research and scientists at the University of California shapes, sizes, and colors and can breed exhibition. In 2002, the Hawai'i Depart­ at Davis and the U.S. Geological Survey with and are the same species as the Mal­ ment of Agriculture placed an embargo (USGS) are developing techniques to lard. Common Mallard breeds found in on all birds shipped to the islands (with more accurately differentiate duck types. Hawai'i include the Pekin, Khaki Camp­ some exceptions, for example, fertile bell, Blue Cayuga, Rouen, and Indian eggs) to protect the public from West Nile Hope for the Future of the Koloa Runner. Barnyard ducks are bred for Virus. However, the Mallard continues to Koloa conservation involves not characteristics such as egg production or reproduce and be sold in the State. only gathering scientific data but also THE GLOBAL FERAL MALLARD THREAT Worldwide, native ducks are vulnerable to invasion and hybridization with feral Mallards, particularly when already in jeopardy from habitat loss and introduced mammalian predators. The Mallard occurs naturally in the Northern Hemisphere, but because of its popularity, people have transported it to areas where it was not previously found. Mallard introductions have caused conflicts with native duck populations throughout the world. In New Zealand, descendants of game-farm Mallards, estimated to number 4 to 5 million, are responsible for the near extmction of the New Zealand Grey Duck. In South Africa, Mallards intro­ duced by farmers and waterfowl collectors now threaten both the African Black Duck and Yellow-billed Duck. Photo H. Stiver Photo by C.D. Roderick WHAT STIU NEEDS TO BE DONE TO ENSURE THE FUTURE OF THE KOLOA? Research • Determine range, behavior, and abundance of Koloa, feral Mallards, and their hybrids in Hawaii. • Estimate the extent of hybridization between these species. • Develop practica l techniqu es for differentiating Koloa, Mallards, and their hybrid s. Planning • Develop a Koloa Conservation Plan to address the feral Mallard problem and use re search re sults to guide ma nagement actions. Recommendations • Inform the public about the feral Mallard threat to Hawai'i's endemic ducks. • Ensure new stocks of Mallards and closely related ducks that threaten Koloa are not imported. • Humanely remove existing feral Mallards and hybrids from the wild and prevent additional releases of captive Mallards. informing the public and policymak­ exemptions for licensed shooting preserves Recommended Reading ers about the feral Mallard threat and and dog training), requires proper caging Engilis, A., Jr., and Pratt, T.K., 1993, Status developing humane methods for threat for permitted ducks, and prohibits sale of and population trends of Hawaii's native removal. The Koloa is protected by the Mallards to anyone not properly permitted. waterbirds, 1977- 1987: Wilson Bulletin, v. Federal Endangered Species Act, but Fortunately, once feral Mallards are 105, p. 142-158. Mallard x Koloa hybrids are not. removed, Hawai'i's isolated, island envi­ Engilis, A., Jr., Uyehara, K.J., and Giffin, J.G., Feral duck control programs in other ronment may provide natural barriers to 2002, Hawaiian Duck (Alias wyvillialla), regions have made significant strides reinvasion. The FWS describes the Koloa ill Poole, A., and Gill, F. , eds., The birds toward conserving native duck popula­ as having "a high potential for recovery." of North America, No. 694: Philadelphia, tions, providing conservation models Although little is known about the Koloa, The Birds of North America, Inc. for Hawai 'i to follow. In Florida, for it may be resilient in facing many of the Florida Fish and Wildlife Conservation Com­ example, feral Mallards threaten the threats that have extinguished other native mission, 2004, A conservation plan for the native Mottled Duck, and the State Fish Hawaiian birds.
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