Red-billed duck
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Red-billed duck |
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| Anas erythrorhyncha | ||||||||||||
| Gmelin , 1789 |
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The red-billed duck ( Anas erythrorhyncha ) is an African duck bird that is counted among the swimming ducks. In Africa, this species of duck is probably one of the most populous.
Appearance
General characteristics and likelihood of confusion
The red-billed duck is a medium-sized duck. It reaches a height of 43 to 48 centimeters. The red beak and the strikingly light cheeks and throat, which contrast with the dark head cap and the dark neck, make them unmistakable in their natural range. From a distance it can be confused with the Hottentot duck, whose range overlaps that of the red-billed duck in many regions of Africa. However, the Hottentot duck is significantly smaller and its cheeks are light brown and the beak - apart from the black beak nail - is lead gray throughout. In Madagascar, flying red-billed ducks can be confused with the rare amber duck . However, this has a white wing mirror , while the red-billed duck has a cream-colored one.
Details of the appearance
Red-billed ducks show neither a seasonal dimorphism , nor is there a conspicuous sexual dimorphism in this species . Males are only slightly larger. However, there is a clear difference in voice between the two sexes. The males give a low whirring sound while the females creak and croak.
The body plumage is overall gray-brown. The shoulder and scapular feathers are dark chocolate brown. The body feathers all have a light hem, so that the plumage appears as a whole scaly. The underside of the body is darker than the chest and torso. The tail is relatively short. The lower wings are dark. The wing mirror is wide and framed by a narrow, dark band. The beak is conspicuously bright red, the ridge of the upper beak is dark brown to black brown. The legs are gray, the eyes brown. In the males, the plumage is a bit more contrasted overall during the breeding season. They then appear a little more scaled. Young ducks largely resemble the adult red-billed ducks, but their plumage is a little more dull and their beak is more pink. The full moult takes place after the brood has ended. Red-billed ducks are unable to fly for 24 to 28 days.
The chicks are dark brown on top and pale yellow on the underside. The face is pale; the yellow cheeks, on the other hand, are striking. The chicks have a conspicuous eye rein and a dark ear mark.
Distribution area
The distribution area of the red-billed duck is the south and east of Africa and Madagascar. The distribution area extends from Ethiopia and Sudan in the north to Angola and the Cape Province in the South African Republic. The red-billed duck is predominantly a resident bird. However, some populations also migrate when conditions deteriorate in the wetlands they use. Ringed birds have been found up to 2,191 kilometers from the ringing location. In southern Africa, five percent of all recovered birds were more than 1,000 kilometers from the ring location. However, it is considered likely that there is no migration between the southwestern and eastern populations. The migration movements of the populations in the south tend to be along the West African coast. The red-billed duck does not seem to breed very often in Madagascar, although it is a quite common bird in Madagascar. From this it is concluded that red-billed ducks keep migrating from East Africa to Madagascar. The fact that the species migrates within its range is also proven by reports of random visitors. For example, a small group of red-billed ducks stayed in the area of Kibbutz Ma'agan Micha'el in Israel from June to July 1968 .
Duration
The red-billed duck is a common duck in many areas of its range. Often it is even the most common species of duck. This also applies to Madagascar, where their number is declining due to extensive habitat changes. The population is estimated at 500,000 to one million red-billed ducks in South Africa, 100,000 to 300,000 ducks in East Africa and around 15,000 to 25,000 ducks in Madagascar.
Habitat, food and general behavioral characteristics
The habitat of the red-billed duck are shallow lakes, wetlands, water retention basins, cattle troughs and floodplains. The waters it uses are all eutrophic. In Madagascar they can also be found on small rivers. She also uses rice fields to forage. Outside of the breeding season, they can be seen in large flocks made up of several thousand ducks. It is often also associated with other species of duck.
Red-billed ducks look for their food mostly by rooting, occasionally grazing on land. They also use agriculturally grown plants as food and can be found in fields at night. Most of the food consists of aquatic plants as well as seeds, roots and invertebrates. Seeds of Panicum play a large role in their diet. While animal food plays an important role in many duck species, especially at the beginning of the breeding season, and a lack of it has a negative effect on the reproductive rate (for example in the case of the Eurasian pintail ), red-billed ducks also reproduce with food that is only a small part of invertebrates , but consists to a large extent of millet. This allows the species to reproduce even in semi-arid areas and to reproduce in years with little rainfall.
Reproduction
The red-billed duck has no conspicuous courtship repertoire. One of the most striking courtship gestures of the swimming male is a head movement in which the head is thrown backwards. The beak remains horizontal to the water surface. While moving the head, the male calls geee in quick succession .
Red-billed ducks breed in all months of the year. Changing water levels trigger the reproductive instinct. The brood stimulation evidently builds up very quickly. In southern Africa, the peak of reproduction falls in the months of October to May. In the more western Cape Province, the peak of reproduction falls between August and October.
The nests are built in the plant belt of the waters and are located in the immediate vicinity of the bank. The choice of nesting place and nest building are done by the female alone. The male is only a passive companion. The eggs are oval, have a smooth shell and are light brown to cream in color. A full clutch has an average of ten eggs; However, clutches with five to twelve eggs are also common. The laying interval is 24 hours. Eggs are usually laid in the early morning. The female breeds alone. The breeding season is 25 to 28 days. The chicks are led by the female alone. The males form small moulting societies during this time. The young ducks are able to reproduce after a year.
Keeping in human care
The red-billed duck is not a very common enclosure bird. This is mainly due to the fact that with the South American Bahamian duck there is a very similarly colored duck bird, which is preferred by ornamental poultry keepers because of its slightly more contrasting plumage and its more spirited behavior.
The red-billed duck was first shown at London Zoo in 1850. It was first seen in the Berlin Zoo in 1882. The enclosure population existing in Europe is not considered to be very large, but it is apparently stable and not endangered by inbreeding depression .
supporting documents
Individual evidence
- ↑ Kolbe, p. 244
- ↑ Kear, p. 588
- ↑ Kolbe, p. 243
- ↑ Kolbe, p. 244
- ↑ Kear, p. 588
- ↑ Kear, p. 588
- ↑ Kear, p. 588
- ^ Kear, p. 589
- ↑ Kolbe, p. 244
- ↑ Kolbe, p. 244
- ^ Kear, p. 590
- ↑ Kolbe, p. 245
- ↑ Kolbe, p. 244
literature
- Janet Kear (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe: The world's ducks . Ulmer Verlag, 1999, ISBN 3-8001-7442-1
Web link
- Anas erythrorhyncha inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved February 6, 2014.