Sunda white-throated duck
| Sunda white-throated duck | ||||||||||||
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Sunda white-throated duck |
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| Anas gibberifrons | ||||||||||||
| S. Müller , 1842 |
The Sunda white-throated duck ( Anas gibberifrons ), also known as the Indonesian white-throated duck , is a duck bird from the swimming duck tribe . It belongs to the species group of white-throated ducks, which includes the Sunda white-throated duck, the Andaman white-throated duck and the Australian white-throated duck. One of the most striking characteristics of this Indonesian duck species is the very strongly arched forehead. The function of this eye-catching head shape has not been clarified. It is due to an enlargement of the anterior head bones.
The way of life of the Sunda white-throated duck has not yet been adequately researched. This is mainly due to the fact that the Australian white-throated duck is considered to be very similar to this species and research efforts have so far been largely limited to this species.
Appearance
The Sunda white-throated duck should not be confused with other duck species due to its head shape. In terms of plumage, however, it is very similar to the Australian white-throated duck. However, the Sunda White-throated Duck is a bit darker and a bit smaller overall.
Sunda white-throated ducks show neither seasonal dimorphism nor conspicuous sexual dimorphism . In males, the forehead is usually more prominent. The wing mirror is black with a white border. Chest, flank and shoulder feathers are almost black and have a narrow, light-colored hem. The forehead plumage is bushy and arched. In both sexes, the plumage shines bronze. The lower wings are black. The beak is blue-gray. The iris is red, but outside of the breeding season it can also appear brownish. Young ducks resemble adult birds, but their pen and ink drawing is finer, so that they appear less spotted and darker overall. The moulting process has not yet been adequately investigated in free-living Sunda white-throated ducks. In ducks kept in human care, the full moult sets in after reproduction has ended. The ducks are unable to fly for between 23 and 28 days. Young ducks renew their small plumage between the tenth and 24th week of life and the overall plumage between the 24th and 52nd week.
The chicks are brownish on the top of the body. The underside of the body is gray. The parting is black, the face, cheeks, chin and chest are brown. A dark line of color runs behind the eye on the face. There is also a dark ear mark. There is a noticeable bright spot on both sides of the fuselage.
Sunda white-throated ducks are considered to be relatively quiet ducks. However, their vocalizations have not yet been studied very intensively. The female is characterized by a harsh croaking. The male occasionally makes whistling sounds. Sonagrams of this species of duck are not yet available.
Distribution and existence
The distribution area overlaps in places with that of the Australian white-throated duck. Since the Sunda white-throated duck has not yet been adequately researched, the exact distribution is unknown. The Indonesian islands where the Sunda white-throated duck is found include Java , Bali , Lombok , Pulau Jawa, Kalimantan , Sulawesi , Sumba , Flores , Timor and Wetar . It has also been observed in Sumatra . However, it is not certain whether it is part of the breeding bird population there.
The population of the Sunda white-throated ducks was estimated at 10,000 to 100,000 individuals in 2002.
Habitat and food
The Sunda White-throated Duck inhabits wetlands, ponds, and rivers. Large accumulations are found mainly in mangrove swamps.
The diet of the Sunda white-throated duck has so far not been adequately studied. Presumably it resembles that of the Australian white-throated duck. This finds its nourishment by sifting through the water or soft bank mud and rooting in shallow water. She seldom dives. The diet consists mainly of invertebrates.
Reproduction
Little is known about the breeding biology of free-ranging Sunda White-throated Ducks. All findings come from Sunda white-throated ducks kept in human care.
Sunda white-throated ducks breed on the ground, but also adopt brood boxes in captivity. The eggs are elliptical, white in color and have a smooth shell. They measure 49.25 × 35.8 millimeters. The full clutch consists of six to eleven eggs. On average, a clutch has 8.3 eggs. The female breeds alone. The breeding season is 26 to 28 days. Newly hatched chicks weigh an average of 19.4 grams. They fledge at seven to eight weeks of age. They presumably reach sexual maturity after one year.
Human and Sunda White-throated Duck
Influence of humans on the Sunda white-throated duck population
Like all other species of duckbird, Sunda white-throated ducks are hunted on the Indonesian islands. Their meat is regularly offered in markets. This even includes the markets in Jakarta , although the Sunda white-throated duck is only found some distance from Jakarta.
There is insufficient information to adequately determine the threat status of this species of duck. However, their population numbers are very likely to be negatively influenced by extensive deforestation, flaming and other factors that change their habitat.
The subspecies Anas gibberifrons remissa , endemic to the Solomon Islands island of Rennell , has not been detected since 1959. One cause of the extinction is believed to be the importation of tilapia species, which competed with the ducks for food resources.
Keeping in human care
Sunda white-throated ducks, like other white-throated species, have a rather inconspicuous plumage. Accordingly, they are rarely shown in zoos or taken care of by private owners. The species came repeatedly to Europe as an unintended import addition. However, it went largely unnoticed and disappeared again. Sustainable breeding does not exist.
supporting documents
Individual evidence
- ↑ Kear, p. 508
- ^ Kear, p. 568
- ↑ Kolbe, p. 233
- ↑ Kolbe, p. 233
- ^ Kear, p. 567
- ↑ Kolbe, p. 233
- ^ Kear, p. 568
- ^ Kear, p. 568
- ^ Kear, p. 568
- ^ Kear, p. 571
- ^ Kear, p. 568
- ↑ Kolbe, p. 235
literature
- 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
Web links
- Anas gibberifrons in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on 28 February, 2009.
- Videos, photos and sound recordings for Anas gibberifrons in the Internet Bird Collection