- Anas wyvilliana
Identification
44–51 cm (17¼-20 in)
- Mottled brown overall plumage
- Darker tail
- Dusky head and neck with faint eyering and eyeline.
- Orange legs and feet
- Speculum is greenish-blue
- Bill: Olive green in males; drab tinted dull orange in females
Immature males sometimes have dark greenish head.
Similar Species
This species is smaller and darker than female or eclipse male Mallards from which they also differ in having a mostly dark bill with olive tones. Males lack the Mallard's curled outer tail-feathers. Hawaiian Duck undertail coverts are mottled and their flanks are usually more boldly patterned. When visible the speculum is greenish-blue rather than deep blue. Hybrids with feral Mallards in Hawaii can be difficult to identify but are reported to be rare on Kauai; more common elsewhere.
Distribution
Hawaiian Islands: (Kauai and Oahu)
The most pure population of Hawaiian Duck is found on the island of Kaua‘i. Birds of questionable purity (Mallard hybrids) were re-introduced to the other main Hawaiian Islands over decades. Most "hawaiian ducks" commonly reported from low elevation areas of these islands are Mallard hybrids.
It is possible that a tiny wild population persisted on Hawaii Island in upper elevation streams and ponds on the mountains of Mauna Kea and Kohala before the re-introduction efforts, and remnants of this elusive population still exist.
Taxonomy
This is a monotypic species[1].
Habitat
Lowland wetlands, river valleys, and mountain streams. They nest near reservoirs, or in ditches and streams in sugar cane plantations. They may be found at heights up to 2400 m.
Behaviour
Diet
Their diet consists of vegetation such as algae, rice, grass, leaves and seeds, from wetland plants, also earthworms, dragonflies, molluscs, insects, and other aquatic invertebrates.
Breeding
Nests are a feather lined grass bowl. The clutch consists of 2-10 white or buff eggs.
Vocalisation
Female quacking similar to that of Mallard, but weaker, and calls less often. Male call is a single, soft quack.
Movements
Generally sedentary, although some inter-island movements noted.
In Culture
The Hawaiian name is Koloa.
References
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
- del Hoyo, J., Collar, N. & Kirwan, G.M. (2020). Hawaiian Duck (Anas wyvilliana). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/467121 on 1 February 2020).
- BirdForum Member observations
- Wikipedia contributors. (2020, January 10). Hawaiian duck. In Wikipedia, The Free Encyclopedia. Retrieved 07:27, February 3, 2020, from https://en.wikipedia.org/w/index.php?title=Hawaiian_duck&oldid=935137869
- BirdLife International 2017. Anas wyvilliana (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2017: e.T22680199A112386802. https://dx.doi.org/10.2305/IUCN.UK.2017-1.RLTS.T22680199A112386802.en. Downloaded on 01 February 2020.
- Engilis Jr., A., K. J. Uyehara, and J. G. Giffin (2002). Hawaiian Duck (Anas wyvilliana), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.694
- Pratt, H.D., Bruner, P., and Berrett, D.G. (1987) A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press.
- Pyle, R.L., and P. Pyle. 2017. The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status. B.P. Bishop Museum, Honolulu, HI, U.S.A. Version 2 (1 January 2017) http://hbs.bishopmuseum.org/birds/rlp-monograph/
Recommended Citation
- BirdForum Opus contributors. (2024) Hawaiian Duck. In: BirdForum, the forum for wild birds and birding. Retrieved 28 April 2024 from https://www.birdforum.net/opus/Hawaiian_Duck
