American black duck
American black duck | |
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American black duck in flight | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Anseriformes |
Family: | Anatidae |
Genus: | Anas |
Species: | A. rubripes
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Binomial name | |
Anas rubripes Brewster, 1902
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Synonyms | |
Anas obscura Gmelin, 1789 |
The American black duck (Anas rubripes) is a large
It interbreeds regularly and extensively with the mallard, to which it is closely related. The female lays six to fourteen oval eggs, which have smooth shells and come in varied shades of white and buff green. Hatching takes 30 days on average. Incubation usually takes 25 to 26 days, with both sexes sharing duties, although the male usually defends the territory until the female reaches the middle of her incubation period. It takes about six weeks to fledge. Once the eggs hatch, the hen leads the brood to rearing areas with abundant invertebrates and vegetation.
The American black duck is considered to be a
Taxonomy and etymology
American
Pennant, in Arctic Zoology, Volume 2, described this duck as coming "from the province of New York" and having "a long and narrow dusky bill, tinged with blue: chin white: neck pale brown, streaked downwards with dusky lines."[2] In a typical obscura, characteristics such as greenish black, olive green or dusky olive bill; olivaceous brown legs with at most one reddish tinge; the nape and pileum nearly uniformly dark; spotless chin and throat; fine linear and dusky markings on the neck and sides of the head, rather than blackish, do not vary with age or season.[2]
Description
The American black duck weighs 720–1,640 g (1.59–3.62 lb) and measures 54–59 cm (21–23 in) in length with a 88–95 cm (35–37 in) wingspan.[4] This species has the highest mean body mass in the genus Anas, with a sample of 376 males averaging 1.4 kg (3.1 lb) and 176 females averaging 1.1 kg (2.4 lb), although its size is typically quite similar to that of the familiar mallard.[5][6] The American black duck somewhat resembles the female mallard in coloration, although the black duck's plumage is darker.[7] Males and females are generally similar in appearance, but the male's bill is yellow while the female's is dull green with dark marks on the upper mandible,[8] which is occasionally flecked with black.[9][10] The head is brown, but is slightly lighter in tone than the darker brown body. The cheeks and throat are streaked brown, with a dark streak going through the crown and dark eye.[7] The speculum feathers are iridescent violet-blue with predominantly black margins.[8] The fleshy orange feet of the duck have dark webbing.[11]
Both male and female American black ducks produce similar calls to their close relative, the mallard, with the female producing a loud sequence of quacks which falls in pitch.[12]
In flight, the white lining of the underwings can be seen in contrast to the blackish underbody and upperside.[7][13] The purple speculum lacks white bands at the front and rear, and rarely has a white trailing edge. A dark crescent is visible on the median underwing primary coverts.[13]
Juveniles resemble adult females, but have broken narrow pale edges of underpart feathers, which give a slightly streaked rather than scalloped appearance, and the overall appearance is browner rather than uniformly blackish. Juvenile males have brownish-orange feet while juvenile females have brownish feet and a dusky greyish-green bill.[13]
Distribution and habitat
The American black duck is endemic to eastern North America.[14] In Canada, the range extends from northeastern Saskatchewan to Newfoundland and Labrador.[7] In the United States, it is found in northern Illinois, Michigan, New Jersey, Ohio, Connecticut, Vermont, South Dakota, central West Virginia, Maine and on the Atlantic coast to North Carolina.[7][15]
The American black duck is a habitat generalist as it is associated with tidal marshes and present throughout the year in salt marshes from the
Behavior
Feeding
The American black duck is an omnivorous species[17] with a diverse diet.[18] It feeds by dabbling in shallow water and grazing on land.[17] Its plant diet primarily includes a wide variety of wetland grasses and sedges, and the seeds, stems, leaves and root stalks of aquatic plants, such as eelgrass, pondweed and smartweed.[7][8] Its animal diet includes mollusks, snails, amphipods, insects, mussels and small fishes.[17][18]
During the breeding season, the diet of the American black duck consists of approximately 80% plant food and 20% animal food. The animal food diet increases to 85% during winter.[17] During nesting, the proportion of invertebrates increases.[8] Ducklings mostly eat water invertebrates for the first 12 days after hatching, including aquatic snowbugs, snails, mayflies, dragonflies, beetles, flies, caddisflies and larvae. After this, they shift to seeds and other plant food.[17]
Breeding
The breeding habitat includes alkaline marshes, acid bogs, lakes, ponds, rivers, marshes, brackish marshes and the margins of estuaries and other aquatic environments in northern Saskatchewan,
Nest sites are well-concealed on the ground, often in uplands. Egg clutches have six to fourteen oval eggs,[11] which have smooth shells and come in varied shades of white and buff green.[19] On average, they measure 59.4 mm (2.34 in) long, 43.2 mm (1.70 in) wide and weigh 56.6 g (0.125 lb).[19] Hatching takes 30 days on average.[11] The incubation period varies,[19] but usually takes 25 to 26 days.[22] Both sexes share duties, although the male usually defends the territory until the female reaches the middle of her incubation period.[22] It takes about six weeks to fledge.[22] Once the eggs hatch, the hen leads the brood to rearing areas with abundant invertebrates and vegetation.[22]
The American black duck interbreeds regularly and extensively with the mallard, to which it is closely related.[23] Some authorities even consider the black duck to be a subspecies of the mallard instead of a separate species. Mank et al. argue that this is in error as the extent of hybridization alone is not a valid means to delimitate Anas species.[24]
It has been proposed that the American black duck and the mallard were formerly separated by habitat preference, with the American black duck's dark plumage giving it a selective advantage in shaded forest pools in eastern North America, and the mallard's lighter plumage giving it an advantage in the brighter, more open
In captivity studies, it has been discovered that the hybrids follow Haldane's rule, with hybrid females often dying before they reach sexual maturity, thereby supporting the case for the American black duck being a distinct species.[23][28]
Nest predators and hazards
The apex nest predators of the American black duck include American crows, gulls and raccoons, especially in tree nests.[17] Hawks and owls are also major predators of adults. Bullfrogs and snapping turtles eat many ducklings.[17] Ducklings often catch diseases caused by protozoan blood parasites transmitted by bites of insects such as blackflies.[17] They are also vulnerable to lead shot poisoning, known as plumbism, due to their bottom-foraging food habits.[17]
Status and conservation
Since 1988, the American black duck has been rated as
The United States Fish and Wildlife Service has continued to purchase and manage habitat in many areas to support the migratory stopover, wintering and breeding populations of the American black duck.[14] In addition, the Montezuma National Wildlife Refuge has purchased and restored over 1,000 acres of wetlands to provide stopover habitat for over 10,000 American black ducks during fall migration.[14] Also, the Atlantic Coast Joint Venture has been protecting the habitat of the American black duck through habitat restoration and land acquisition projects, mostly within their wintering and breeding areas.[14] In 2003, a Boreal Forest Conservation Framework was adopted by conservation organizations, industries and First Nations to protect the Canadian boreal forests, including the American black duck's eastern Canadian breeding range.[14]
References
- ^ . Retrieved 13 July 2022.
- ^ JSTOR 4069311 – via Biodiversity Heritage Library.
- ISBN 978-1-4081-2501-4.
- ^ a b "American Black Duck". www.allaboutbirds.org. 2011. Archived from the original on 2017-02-17. Retrieved 2017-06-29.
- ISBN 978-0-8493-4258-5.
- ISBN 978-1-4200-6444-5.
- ^ ISBN 9781885106209.
- ^ ISBN 9780198610090.
- ISBN 9781469625652.
- ISBN 9780792253143.
- ^ ISBN 9781584657491.
- ^ "American Black Duck". The Cornell Lab - All About Birds. Retrieved 20 December 2019.
- ^ ISBN 9781408135235.
- ^ ISBN 978-1400831517.
- ^ a b c d e U.S. Department of the Interior, National Park Service (2007). Cape Cod National Seashore (N.S.), Hunting Program: Environmental Impact Statement. pp. 83–84.
- ISBN 9781610912297.
- ^ ISBN 9780811726818.
- ^ ISBN 9781561643356.
- ^ ISBN 9781421407517.
- doi:10.2173/bow.ambduc.01. Archived from the originalon 2016-03-25. Retrieved 2017-06-30.
- ^ ISBN 9781898918004.
- ^ ISBN 9781453531921.
- ^ ISBN 978-0-19-518323-8.
- ^ S2CID 24144598.
- ISBN 9780691129662.
- JSTOR 2423425.
- PMID 28569026.
- doi:10.1139/z04-169.
- ^ Anonymous (2007). Lake Umbagog National Wildlife Refuge (N.W.R.), Conservation Plan: Environmental Impact Statement. pp. 142–143.
- ^ Rhymer, Judith M. (2006). "Extinction by hybridization and introgression in anatine ducks". Acta Zoologica Sinica. 52 (Supplement): 583–585. Archived from the original (PDF) on 2013-12-03.
- .
- ISBN 9781847979704.
- ISBN 9780080924991.
- ^ Wintersteen, Kyle (2013-03-01). "Black Ducks in Peril". American Hunter. Archived from the original on 2016-03-26. Retrieved 2013-03-02.
External links
- American Black Duck Species Account – Cornell Lab of Ornithology
- "American Black Duck media". Internet Bird Collection.
- American Black Duck photo gallery at VIREO (Drexel University)
- Interactive range map of Anas rubripes at IUCN Red List maps