Hawaii duck
| Hawaii duck | ||||||||||||
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A pair of Hawaiians ( Anas wyvilliana ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Anas wyvilliana | ||||||||||||
| Sclater , 1878 |
The Hawaiian Duck ( Anas wyvilliana ) is a bird art from the family of ducks (Anatidae). It is endemic to Hawaii and is called Koloa Maoli there. The species is endangered, the population is estimated at 2200 to 2500 individuals. Genetic studies have shown that it is in birds to hybrids between Laysan Duck ( Anas laysanensis ) and Mallard ( Anas platyrhynchos to act). Hybridization probably took place around 11,000 years ago.
features
The rather small species of duck has mostly dark brown plumage and a length of 44 to 51 centimeters. The beak of the males is olive green with dark markings on the upper beak. The wings are mostly paler than the rest of the body, the wing mirrors are emerald green to violet blue. A darker morph of the males as well as all females show a speckled brown plumage, with a slightly reddish color on the breast, as well as a dark beak with dark yellow to orange colored markings. A lighter morph of males has green markings on the head and neck and reddish markings on the chest.
distribution and habitat
Originally found on all Hawaiian islands with the exception of Lānaʻi and Kahoʻolawe , today there is only an autochthonous occurrence on Kauaʻi . It comprises 80 percent of the total stock. The populations on the other islands were created through resettlement from rearing and are usually very small. Between 1975 and 1982 200 individuals were settled on the main island of Hawaii. Small populations are also found on Oahu , where 326 birds were reintroduced between 1958 and 1982, and Maui , where twelve were released in 1989.
The Hawaiian duck lives in the wetlands of the Hawaiian Islands from sea level up to 3000 m.
Way of life
The Hawaiian duck looks for its food in shallow, marshy waters that are no deeper than 13 cm. The taro fields also served as a habitat, but their number has fallen sharply due to the reduced production of the food plant, also known as taro . The ducks are omnivores and feed on snails, dragonfly larvae, worms, grass seeds, algae and leaves of aquatic plants.
The Hawaiian duck builds their nests on the ground near the body of water. The female lays eight to ten eggs. Hatching takes place all year round, but the duck shows increased breeding activity from January to May. The exact length of the breeding season until the chicks hatch in the wild has not been adequately investigated, but is less than 30 days.
The clutches and the chicks are endangered by imported and introduced predatory animals and rodents such as dogs , cats , mongooses and rats .
Danger
Around a third of the coastal wetlands have been drained in the past 110 years . The flood control changed the hydrology in the breeding areas of the Hawaiian duck. Introduced plants such as batis , water hyacinths and red mangroves also reduced the open water and bank areas. The Hawaiian duck was also hunted on a large scale, so that in 1949 only 520 individuals could be counted.
Now that protected areas have been created, the greatest threat to the conservation of the species is currently from hybridization with the mallards, which were introduced mainly from the North American continent . Since the late 19th century, and especially in the 1950s and 1960s, hundreds of mallards, including various bred breeds, were introduced to be released for hunting or kept as pets. Many of these ducks feral and mingled with the native Hawaiians. As with most ducks, the hybrids are reproductive and various crosses and backcrosses occur. Most of the ducks on the island of Oahu are now hybrids. Import restrictions for mallards were introduced in the late 1980s. It was not until 2002 that birds imported into Hawaii were completely banned. The main reason for this was not the protection of species, but the danger of the introduction of West Nile viruses , which birds can transmit to humans.
Individual evidence
- ↑ Audubon's WatchList 2002-2006 in taxonomic order by geographic region. ( Memento of the original from November 30, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF, English; 36 kB)
- ^ The Hawaiian Duck appears to be of hybrid origin 2015 HBW Alive
- ↑ a b Koloa Maoli or Hawaiian Duck ( Memento of the original from June 15, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Fact Sheet, Hawaii's Comprehensive Wildlife Conservation Strategy, Department of Land and Natural Resources, Honolulu, October 2005 (PDF, English; 223 kB)
- ↑ Kimberly J. Uyehara, Andrew Engilis Jr. and Michelle Reynolds: Hawaiian Duck's Future Threatened by Feral Mallards. USGS Fact Sheet 2007-3047, 2007 (PDF, English; 5.9 MB)
Web links
- PE Baker et al (2010): Species factsheet: Anas wyvilliana . BirdLife International , accessed November 29, 2010 .
- Koloa Maoli or Hawaiian Duck (PDF; 223 kB) . In: C. Mitchell, C. Ogura, DW Meadows, A. Kane, L. Strommer, S. Fretz, D. Leonard & A. McClung: Hawaii's Comprehensive Wildlife Conservation Strategy . Department of Land and Natural Resources. Honolulu 2005, Hawaii.
- Anas wyvilliana inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2013. Retrieved February 2, 2014.