Black duck
| Black duck | ||||||||||||
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male pied duck |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Polysticta | ||||||||||||
| Eyton , 1836 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Polysticta stelleri | ||||||||||||
| ( Pallas , 1769) |
The black duck ( Polysticta stelleri ) is a member of the duck family . She is related to the eider ducks . However, it is assigned to its own genus. Its round head and dainty beak give it the appearance of a green duck .
Black ducks have their main distribution area in the Bering Sea . They occur predominantly in the area of the estuaries of the Arctic rivers. The worldwide population of this duck, which also overwinters in small numbers in the Baltic Sea, decreased by 40 percent in the last half of the 20th century; at the end of the 20th century it was estimated at 220,000 individuals. Outside of the breeding season they gather in large swarms, moulting groups can contain more than 50,000 individuals.
Black ducks are very rare wanderers in Central and Western Europe. A total of 27 spotted ducks were observed on the coast of Mecklenburg-Western Pomerania and Schleswig-Holstein between 1975 and 1997. A group of 65 individuals was seen in Poland in March 1987.
Appearance
Pied ducks have a body length of 43 to 47 centimeters and then weigh 650 and 900 grams. The species has a pronounced sexual dimorphism : the male's head and belly are white to yellow-brown. The back is colored dark. The arm covers are white. The mirror is dark steel blue-green with a wide white end band. In the vicinity of the beak root there is a diffusely delimited light green spot. The eye is surrounded by a black eye spot. Male black ducks also have a wide black neck ring. The black and white shoulder feathers are elongated so that they fall over the folded wings. When resting, the male largely resembles the female and, like them, has yellow and red-brown plumage. The elongated shoulder feathers, however, are clearly bent downwards even in the resting dress. The wings have the same white covers as can be seen in the magnificent dress.
In flight, the wings of the male pinto are conspicuously black and white. Against the background of the white arm swings, the dark mirror looks like a narrow, black bracket.
The female resembles a female mallard , but is darker. The plumage is more yellow and red-brown, as in the female of the eider. A ring under the eyes is clearly visible. The ends of the large blankets and the arm swings are white. Females of the pied duck also have a striking blue and white mirror. It is particularly easy to see in flight.
The chicks have a dark sepia-brown down dress with noticeably thick and relatively long down. The eye area, an eye stripe and the chin and throat are yellowish brown. The underside of the body is dirty white. Otherwise they do not have any light spots. Young, not yet sexually mature pinto ducks have a red-brown coat plumage like the females. The steel-blue mirror is already indicated in the male young ducks. Black feathers can be found in the throat and neck area of the young drakes' first magnificent dress. They still have white-edged feathers on their shoulders and creamy yellow on their chest and flanks. In the second splendid plumage, they already largely resemble the adult male pinto ducks. The transitions between the individual color areas are, however, still diffuse and less clearly drawn. The small and middle arm covers are still gray-brown.
Distribution area and habitat
The range of the species lies in the Arctic between the Russian Taimyr peninsula and Alaska . The main distribution center is east of the Khatanga River . Large populations are found in the delta of the Siberian rivers Lena and Indigirka , for example . The population on the Alaskan coast is small compared to that of the Siberian. Her focus is on Barrow . For the western Palearctic there are a few breeding records for the Kola Peninsula and the White Sea . About five to fifty breeding pairs also breed in northern Norway. Non-breeding black ducks stay in the shelf seas all year round and prefer the estuaries of arctic rivers. The breeding black ducks also live in the open sea outside the breeding season.
During the winter half-year she stays in the North Pacific from Alaska via the Aleutian Islands to Kamchatka . Occasionally during this time it also reaches the northern Japanese coast and migrates along the Canadian coast to the Canadian province of British Columbia . As a stray visitor, she occasionally turns up on Baffin Island , on the Greenland coast or on the St. Lawrencestrom. Black ducks are persistent fliers and occasionally reach northern Europe. The wintering sites include the Norwegian Varangerfjord , the Kola Peninsula, the coast off the Lithuanian city of Palanga and the coast off the Estonian island of Saaremaa . These wintering guests are probably the few black ducks that breed west of the Khatanga river. The number of ducks that winter in the Baltic Sea has increased in recent years. The European winter population is around 7,700 to 20,000 individuals. The black ducks that winter in Norway prefer stretches of coast with a gently sloping profile and usually look for food at a distance of less than 200 meters from the shore. They leave the Norwegian wintering area in May to move back to the breeding areas.
The pied duck uses the tundra as a breeding area. Black ducks migrate north in large flocks from spring to early summer. You will reach the Bering Strait around mid-June . As soon as the breeding areas are ice-free, they begin to reproduce.
Reproduction
Black ducks usually breed on small tundra lakes and ponds. They are mainly to be found in the Bülten and Torfhügel tundra. Occasionally they form small colonies. The largest known colony was located near the Lena River and included 63 nests. The nest, made of grass and dunes, is hidden near the water. In both the Lena Delta and the breeding areas of Barrow, Alaska, black ducks prefer to breed near Spatula skuas . Years with above-average breeding success usually coincide with the gradation years of lemmings .
The spotted duck's clutch usually consists of five to eight eggs, which are light olive in color. If the clutch is lost, the females lay a second clutch, which however only comprises between three and six eggs. The female breeds alone. The incubation period is 26 to 27 days. The male remains close to the female until the start of breeding, but then leaves it to move to the moulting areas. These are sometimes more than 3,000 kilometers away from the breeding areas.
The chicks hatch around mid-July. The female first seeks freshwater with the newly hatched downy chicks. As a rule, the young are abandoned by the adult female before they have fledged.
food
Pied ducks dive well. In the winter months they often look for food closely packed together and often dive in large flocks at the same time. Eighty percent of the time she spends foraging for food is spent on diving. The rest of the time she searches for food. She usually stays underwater for half a minute. The diet consists of crustaceans and molluscs; Mussels are preferred. The gray beak has a soft edge on which is used to scrape invertebrates off the rock or used as a tactile device in dark deep water.
Pied ducks and humans
Influence on the stock
The reasons for the population declines that have been recorded for several decades have so far been insufficiently scientifically investigated. Blue ducks are hunted, even if hunting for this species of duck is not allowed in Russia either. For the Lena Delta, it is estimated that around 1,500 black ducks fall victim to illegal hunting here every year. One possible cause of the population decline is the increasing use of this inhospitable region by humans. The region is examined primarily for its oil and gas reserves. A potential threat to this species of duck is oil spills and this risk has increased because of the increasing development of their habitat. The increasing settlement of humans in their habitat has led to an increase in the number of their predators such as great gulls as well as ravens and crows in this region. Fishing is also a problem for the pinto, as they occasionally get caught in fishing nets and drown.
Keeping in human care
Black ducks are very active in movement and are rarely kept in enclosures because of their susceptibility. In Game Bird Center in Salt Lake City, USA a breeding group was established in the mid-1970s. The world's first breeding of this species of duck was achieved there in 1980. In 1981 the breeding group comprised 30 animals, but the breeding success was always very low. In Europe, the British Wildfowl Trust had already attempted conservation breeding in the 1960s and was the only European owner of this species for a long time. Here, breeding success was completely lacking. The first German breeding was achieved in 1997 by a private owner.
literature
- Hans-Günther Bauer, Einhard Bezzel , Wolfgang Fiedler : The compendium of birds in Central Europe. Everything about biology, endangerment and protection, Vol. 1: Nonpasseriformes - non-sparrow birds . Aula-Verlag, Wiesbaden 2005, ISBN 3-89104-647-2 .
- John Gooders and Trevor Boyer: Ducks of Britain and the Northern Hemisphere . Dragon's World, Limpsfield Surrey 1986, ISBN 1-85028-022-3 .
- Janet Kear (Ed.): Ducks, Geese and Swans (Bird Families of the World; Vol. 6). Oxford University Press, Oxford 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe: The world's ducks . Ulmer Verlag, Stuttgart 1999, ISBN 3-8001-7442-1 .
Individual evidence
- ↑ a b c Janet Kear, p. 691.
- ↑ a b c Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.), P. 121.
- ↑ a b c d Janet Kear, p. 690.
- ↑ a b c d Hartmut Kolbe, p. 296.
- ↑ John Gooders and Trevor Boyer, p. 120.
- ↑ a b Janet Kear, p. 692.
- ↑ Janet Kear, p. 491.
- ↑ John Gooders and Trevor Boyer, p. 118.
- ↑ Hartmut Kolbe, p. 297.
Web links
- Polysticta stelleri in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Videos, photos and sound recordings on Polysticta stelleri in the Internet Bird Collection