Eyebrow duck
| Eyebrow duck | ||||||||||||
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Eyebrow duck |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Anas superciliosa | ||||||||||||
| Gmelin , 1789 |
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The eyebrow duck ( Anas superciliosa ) is a duck bird that is counted among the swimming ducks. The division of this species into three subspecies has meanwhile been separated again. DNA research has suggested that there is not enough difference between the three subspecies described earlier to warrant a division into subspecies.
The species occurs exclusively in Australasia. The IUCN classifies the species as not endangered ( least concern ).
Appearance
general characteristics
The eyebrow duck is a large species of swimming duck. It reaches a body length between 54 and 61 centimeters, of which two thirds are attributable to the trunk. The wingspan is 80 to 100 centimeters. Overall, it is a large, sturdy duck with a long head and beak in relation to its size. What is striking about the eyebrow duck is the high-contrast head fletching. The vertex is black, over the eye there is a clearly demarcated eye stripe that is curved downwards in the shape of a crescent. A second fine stripe (so-called beard stripe) runs at the lower end of the face.
Swimming eyebrow ducks lie high in the water. They are able to fly up from the surface of the water very quickly, with the wings plunging into the water when they first flap their wings. They fly with a flat wing beat, while a loud whistling sound can be heard as an instrumental sound. They come ashore frequently and move about with ease. Your body is parallel to the ground when you run.
feather dress
As is characteristic of many other tropical duck species, this species does not show any conspicuous sexual dimorphism , but some characteristics , such as voice and behavior, allow an exact determination of the sexes even when observing the field. The headstock, which is almost black in males, is often brown in females. The female is also usually a bit smaller. The chin and throat are grayish white in both sexes. The body plumage is predominantly gray-brown. Due to the narrow, light hems, the body's plumage appears clearly scaled. The beak is solid dark gray to gray green with a black nail. The feet are yellow-green. Young ducks resemble adult birds, but are striped on the underside of their bodies. This is particularly evident on the chest.
The chicks are dark brown on the headstock and on the back. The face is yellow and streaked with both eyes and beard. The ventral side is yellowish. The spots on the back are similar to those of the mallard chicks.
The moulting takes place with varying intensity throughout the year. Most eyebrow ducks are newly molted at the beginning of the breeding season. The peak of the moult is from December to March.
Possible confusion
The eyebrow duck has many similarities in appearance and behavior with the mallard , which is also widespread in New Zealand due to the introduction of this species in the 19th and early 20th centuries and is also common in Australia, at least in more densely populated regions in the southeast . There is a possibility of confusion between the females of both species and the mallard's drake in simple dress.
In addition, the eyebrow duck can be confused with a few species of ducks native to Australia and New Zealand. The Australian shoveler is smaller and slimmer and has a much larger bill. There is a resemblance especially between the females of both species and when the males of the shoveler wear their simple dress. The monkey duck has a uniform black-gray patterned plumage. There is also a possibility of confusion with the mane goose when it is wearing its resting dress. The distinguishing feature of this goose is the lack of stripes on the face, the brown head and the spotted chest.
Distribution area
The eyebrow duck can be found in Australia, New Guinea, the Indonesian islands to the south of Sumatra, Sulawesi and Halmahera. Their distribution area extends to New Zealand and reaches the Solomon Islands in the north. Fiji, Tonga and Samoa are also settled by it. The distribution area thus extends from the equator to the subantarctic.
In New Zealand the stocks are very strongly hybridized with the imported mallard. These intermediate hybrids are also found on the adjacent islands. The first hybrids between eyebrow ducks and mallards were reported as early as 1917. As early as 1992, 40 percent of the eyebrow ducks living in New Zealand were considered mixed with mallards. The mallard population in New Zealand is estimated to be over five million individuals. In contrast, the New Zealand population of eyebrow ducks is only between 10,000 and 100,000 individuals.
In Australia, the population is estimated at 500,000 individuals.
habitat
The eyebrow duck is a very adaptable species of duck that inhabits a wide range of wetlands. It is often found in wetlands with high water levels and dense vegetation. In doing so, it only uses existing bodies of water. She prefers shallow waters. It is much rarer on saltwater lakes. During dry periods, however, they are often found in estuaries, coastal lagoons, salt marshes and the tidal areas of rivers. In New Zealand they can also be found in the mountains or in densely forested regions. It is rare today in agricultural and densely populated areas, which may be due to the introduction of the mallard to New Zealand.
The eyebrow duck is considered a resident bird, provided that the water it inhabits is permanent and does not dry out during the dry season. However, part of the population is also found in temporarily existing floodplains and migrates far in different directions when these dry out. In dry periods, the Australian eyebrow ducks show great migratory movements. These migratory movements are well documented by the recoveries of ringed birds. Of the birds ringed in Griffith in New South Wales, Australia, 23 percent of the 396 recovered birds were discovered more than 200 miles from the ringing location. Six of the birds had reached Tasmania and two of the recoveries were from northern Queensland. There is evidence that they even migrated from the Australian continent to islands in the Southwest Pacific during this period.
Food and diet
The eyebrow duck is predominantly a herbivore. The seeds of aquatic and bank plants are of great importance. She sifts through the surface of the water. It also digs in deeper waters. Occasionally one can also watch her graze on land. During the resting phase, she either sits on the water or sits on tree trunks lying in the water. It also occasionally steals food from the Australian bog duck and other species (so-called kleptoparasitism ).
Food intake usually takes place at the beginning of the night and at dawn.
Reproduction
Eyebrow ducks enter into long-standing, monogamous relationships that are likely to last until one of the two partner birds dies. Of 24 females observed in Canberra, Australia over a period of five years, five were with the same drake during the entire observation period. In six females, a pair population could be occupied for three years, in seven for four years. Only once was it observed that a male raised offspring with another female in the next year.
In the southeast of Australia the eyebrow ducks breed from July to December. Sometimes clutches can still be found in February. The breeding season is similarly extended in New Zealand. Insufficient data are available for the islands colonized by the eyebrow duck.
The nesting site is chosen by the female. The search is part of courtship behavior and the female is often accompanied by the male. Usually the nest is found in tree hollows, occasionally the abandoned nests of other water birds are also used. The eyebrow ducks rarely breed on the ground. The nest is built from the material that is in the immediate vicinity. The nesting trough is padded with lots of gray down. The eggs are elliptical, have a smooth, shiny shell. The color is creamy white. The full clutch contains an average of nine eggs. However, clutch sizes between seven and 12 eggs are normal. Clutches that contain more than twelve eggs usually come from several females. But there is no evidence of brood parasitism as a reproductive strategy. Small clutches indicate that the female was disturbed during oviposition. They are usually not incubated.
The laying interval is one day. The eggs are usually laid in the early morning. The female breeds alone. The breeding season averages 29 days with a range of 26 to 32 days. The male stays close to the female at the beginning of the breeding season. Often the couple bond then loosens; however, some males remain close to the female until the end of the breeding season. The females interrupt brood about twice a day and usually leave the nest alone for less than two hours. Only during the last two days of incubation does the female no longer leave the clutch. If the clutch is lost, the female will usually lay another clutch after two weeks. A second clutch occurs about eight weeks after the brood has successfully reared. Two clutches per year are characteristic of eyebrow ducks. But there is at least one evidence that eyebrow ducks raised three clutches in one reproductive period.
The chicks are led by the female alone. The female can distinguish her brood very well from that of other eyebrow ducks. Chicks that have lost touch with their family unit and are trying to join another duck family are often killed by the strange female eyebrow.
Keeping in human care
Eyebrow ducks have been kept in human care since the second half of the 19th century. The zoo in Berlin first showed this species of duck in 1874. Today, however, they are rarely seen in European and North American zoos. They are considered to be problem-free in keeping. However, it is necessary to keep the eyebrow ducks in small enclosures and aviaries so that they do not hybridize with mallards.
literature
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press , Oxford 1990, ISBN 0195530683
- Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0-19-854645-9
- Hartmut Kolbe : Die Entenvögel der Welt , Ulmer Verlag 1999, ISBN 3-8001-7442-1
Individual evidence
- ↑ a b c Kear, p. 534
- ^ Higgins, p. 1320
- ^ Higgins, p. 1321
- ^ Higgins, p. 1321
- ^ Higgins, p. 1333
- ^ Kear, p. 535
- ^ Higgins, p. 1321
- ^ Higgins, p. 1323
- ^ Kear, p. 536
- ^ Higgins, p. 1323
- ^ Higgins, p. 1325
- ^ Higgins, p. 1325
- ↑ a b c d Kear, p. 537
- ↑ Kear, p. 217
Web links
Web link
- Anas superciliosa inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved February 6, 2014.