Shelduck
| Shelduck | ||||||||||||
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Shelduck on a salt marsh |
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| Scientific name | ||||||||||||
| Tadorna tadorna | ||||||||||||
| ( Linnaeus , 1758) |
The shelduck ( Tadorna tadorna ) is a species from the family of duck birds , which belongs to the subfamily of demi-geese (Tadorninae). Demi-geese resemble geese in their habitus, but they also have features that are characteristic of real ducks . The term shelduck is found for this species, especially in older literature .
The shelduck occurs in two separate populations that use slightly different habitats. In Europe, the shelduck is a species that lives mainly on the coast. The Asian population lives predominantly on salty and brackish steppe waters. Nevertheless, no subspecies are distinguished for this species.
Surname
The scientific species name tadorna is the Latinized form of the French name for this duck bird. The name shelduck is possibly derived from one of the characteristic features of this species, namely the rust-brown chest band. This would then be similar to the now outdated term brand finch for the carmine pimp . In older literature you can occasionally find the name Fox Goose for this species, as the Shelduck occasionally breeds in fox lairs.
description
Adult birds
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Shelduck reach a body length of 58 to 67 centimeters when fully grown and have a wingspan of 110 to 133 cm. The weight fluctuates a lot. In an investigation in the southwest of the Caspian Sea, the males weighed between 830 and 1500 grams in February. The average weight was 1180 grams. Females were significantly lighter with an average of 813 grams and a weight range of 562 to 1085 grams. The species has a goose-like shape and is unmistakable due to the strikingly contrasting color of the plumage. The color of the plumage gives it a distant resemblance to the shelduck , but the size of the shelduck, its long legs, its posture and its short beak rule out that it can be confused with this duck.
In the magnificent dress of the male, the head and the front neck are slightly iridescent black-green. Starting from the shoulders, a greenish-black longitudinal band runs backwards on each side of the body. A wide red-brown band runs around the front chest and back. Starting from the brown chest, another black band runs to the stomach. The body plumage is otherwise predominantly white.
The feathers of the hand wings and the inner flags of the arm wings are white at their base. Otherwise, the hand swing springs and the inner flags of the arm swing springs are black, while the outside flags of the arm swing springs shimmer with a strong bronze-green shimmer. There are red-brown markings on the lower tail and elbow. The under tail plumage is ocher, and the white tail has a narrow black end band. The clearest distinguishing feature between the two sexes is the red-colored beak hump during the breeding season, which is only formed in the male. Its size varies depending on the size of the testicles. The beak humps back while the female is still brooding, and the beak turns dark red-brown again.
The colors are a little duller in the quiet dress. The transitions from the white body plumage to the rust-brown chest band are then more fluid. The head looks more brown-black than black-green. Isolated white feathers can be seen on the face and throat, which can look like spots. The black belly stripe is only hinted at during this time or it may be missing entirely.
In contrast to most ducks , the shelduck has only a slightly pronounced sexual dimorphism . The females are only up to a third smaller than the males and during the breeding season the plumage of the male is slightly more contrasting than that of the female. In the female, too, the head and front neck shimmer black-green during the breeding season. In the female, however, the red-brown chest band and the black belly stripe are somewhat narrower than in the male and are somewhat weaker in color. When resting, his head appears browner than that of the male. In individual females, the base of the beak is blackish.
The movements of the shelduck in flight are similar to those of the geese. Shelduck usually fly low. Large flocks usually fly in irregular line or arc formations; the average flight speed of shelduck moving over the ground is 95 km / h and can be up to 195 km / h under favorable wind conditions. Flying shelducks are easy to identify because of their white wings with the green mirror and their strikingly contrasting body plumage.
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Down and youth dress
The downy chicks have a very contrasting black-brown-white plumage. Headstock, a stripe running over the neck and back to the rump, as well as the shoulders and the sides of the thighs are black-brown. A dark spot behind and under the eye distinguishes the Dunenküken from those of the rust goose . In newly hatched downy chicks, the beak is pale blue-gray with a pink shade directly at the base of the beak and a yellow-brown nail. Feet, legs and webbed feet are olive gray. By the time the young shelduck fledglings, the beak has turned to light pink. The upper beak is still light gray in the area of the beak tip. The legs are gray-pink, the color of the feet and webbed feet is a little more intense pink.
Shelduck that are not yet fully grown are gray-brown on the neck, on the top of the head and on the back. The forehead, parts of the face and the underside of the body are white. The outer flags of the elbow feathers are black-gray. In the female juveniles they are weak and in the males they are more reddish-brown. In their first age, the young birds already largely resemble the adult shelduck. However, the wings still have gray covers, and the frontal hump is poorly developed in young males.
Mauser
In the ganter, the conspicuous red beak hump is already receding while the female is still brooding. The beak then turns dark red-brown. In non-breeding birds, the moulting of the small plumage begins as early as June. In the case of brooding shelduck, it takes place a month later. Shortly after the small plumage moulting begins, the shelduck shed their wings. You will then be unable to fly for a period of 25 to 31 days. For breeding birds this time falls around the month of August. The partial moult of the lesser plumage continues until December. In March the carmine-red frontal cusp appears again in the sexually mature ganter.
Juvenile moulting begins 10 weeks after hatching in young shelduck. In addition to the small plumage, most of the wing covers are also moulted. In December, the young shelducks wear their first old age dress. At this point, both the beak and feet are bright red.
Voice and instrumental sounds
The shelduck's instrumental sounds include a whistling, whirring noise from flight. Similar to ducks, courtship involves a sham cleaning of the plumage, in which the beak creates a rattle on the quills of the wing feathers.
In the breeding area, the shelduck are very call-happy birds. The voices of the two sexes differ significantly. The females call very deep and sonorous. The long, widely audible series of nasal calls "gagagaga" is the call of the female to the male. She is called by both walking and flying females. The call sequence of these "gagaga" sounds is very quick. The female calls out up to twelve syllables per second, so that the call appears almost like a trill. Females that fly up or swim away after a disturbance also call “ak-ak” or excited “egegeg”. The male's calls, on the other hand, are high, whistling and not widely audible. The call of the male is a "tiju-tiju-tirrr-tiju", which is called both in flight and on the ground. The "tirrr" part is a soft trill, the other components of the call are called slowly and emphatically or they are increasing and quickly strung. The calls can be heard particularly often during courtship when the male drives the female in front of him.
distribution
Breeding area
Shelduck breed on the European Atlantic coasts down to the Biscay , beyond that on the coasts of the western Baltic Sea and in the area of the Caspian Sea . There are other, smaller settlements in the west of the Mediterranean. The Asian populations also inhabit rivers and especially wetlands and lakes in semi-deserts and steppes. The Asian distribution area extends from Turkey and the north of the Black Sea via Central Asia to Mongolia and northern China. The southern border of the distribution area runs through Iran and Afghanistan.
In Germany, the shelduck is predominantly a breeding bird in the coastal area and on the islands of the North Sea and the western Baltic Sea . As a breeding bird, it mainly adheres to the sea coast, but also penetrates far inland in search of suitable breeding caves . The expansion into the interior is related to the general population development of this species in Western and Central Europe as well as in Sweden. There are regular breeding occurrences inland, for example, in the sewage fields near Münster (since 1985) and especially on the Lower Rhine (since 1961). It also populated the Elbe up to Dessau.
Outside the breeding season, young birds in particular can be found every now and then on the larger bodies of water all over Germany. Large flocks overwinter in the Wadden Sea of the German-Dutch North Sea coast. Preferred overwintering areas are near Wangerooge and Mellum , in the Jade Bay and on the west coast of Schleswig-Holstein. The main distribution center of the shelduck is in Western Europe. In the huge Asian distribution area, it occurs only as islands.
hikes
In Europe, the shelduck stroke and migratory. It moves almost exclusively at night. The wintering areas of the European population are in the southern North Sea - as long as ice does not form on the Wadden Sea - and the British waters, on the Atlantic coast of France , Spain and Portugal and on the coasts of the western and eastern Mediterranean . As far as the Atlantic coast, mainly juvenile shelduck from Germany, the Netherlands , Belgium and France migrate , while the adult birds for the most part do not migrate beyond the Channel coast and, as long as there is not too severe frost, persist in large numbers in the southern North Sea.
Of the Asian population, many shelducks overwinter on the Caspian Sea coast. A small number migrated to northern Africa, Iraq, Pakistan, northern India, Bangladesh and southern China.
Mauser train
As with other ducks, but also with the grebes and railings, for example, the shelduck's feathers fall out at the same time during moulting , so that the moulting birds are temporarily unable to fly. The animals must therefore seek out areas that are protected from moulting and also rich in food. By far the most important of these areas, known as moulting centers, is located on the mud flats of the Großer Knechtsand between the Weser and Elbe estuaries and on Trischen , a Schleswig-Holstein bird protection island in front of the Meldorfer Bay. The breeding birds of the entire European population ( England , Ireland , the Netherlands , Denmark , Norway , Sweden , Germany , Poland and the Baltic states) meet at these moulting centers . Even breeding birds from the Camargue migrate across the European inland to the southern North Sea.
During the moulting peak in mid-August, up to 100,000 animals can be found on the Großer Knechtsand. The withdrawal into the moulting area is opened in June, mostly by the not yet sexually mature birds in the second calendar year. Only fourteen days later does the breeding birds moult, which leave their youngsters in kindergartens that are looked after by individual adult birds. The birds evidently move from the breeding areas to the moulting centers by the most direct route. For example, birds from the west of the British Isles do not follow the coast, but cross Great Britain directly, overcoming mountains up to 800 m high.
The first freshly molted shelduck leave the moulting grounds in mid-August. They are distributed in the surrounding areas of the Wadden Sea and some move back to the breeding areas, but many also stay in the southern North Sea until spring. The fact that the Großer Knechtsand offers such an ideal moulting location for the shelduck is primarily due to the large silt and sand banks that are exposed at low tide and because it has calm shallow water zones even when the sea is stormy, so that the animals have enough food at all times in this area protected from humans and predators.
Asian shelducks, on the other hand, spend their moulting season near their breeding grounds.
habitat
The European shelduck can be found mainly on the flat sandy and mudflat coasts as well as the corresponding estuaries; they are only very rarely found on steep or rocky coastlines. During the breeding season, the animals usually stay in bays, bays and estuaries and only in exceptional cases on the free sea coast. In the inland they can also be found at large sewage ponds and sewage fields. The shelduck geese primarily use the mudflats, mud banks in river mouths and shallow water lagoons as feeding habitats. The Asian populations, unlike the European ones, are mainly found on inland lakes. Salty and brackish water and a rich food supply of small organisms are characteristic of these steppe waters.
Food and foraging
The shelduck mainly eats small snails , mussels and worms , and more rarely insects and aquatic plants . The main food in the German Wadden Sea is cockles ( Cardium edule ), while waders ( Hydrobia ulvae ) play an important role on the British North Sea coast and brine shrimp ( Artemia salina ) on the salt lakes of Southeast Europe and Siberia . In addition, algae and, in winter, seeds are eaten in fields.
The shelduck foraging is largely dependent on the tides . The birds look for food when the water is low and rest on sandbanks , dunes or salt meadows when the water is high . Depending on the ebb and flow of the tide, shelducks also look for food during the night. In winter, the time shelducks spend foraging can be up to 14 hours.
When acquiring food, the shelduck sifts through the water of every puddle while walking forward with a sideways pendulum movement of its head, or plows through the water surface while swimming with its beak in order to take in floating food. The maximum water depth in which shelducks can successfully find food is 40 centimeters. At this depth, shelduck immerses their entire upper body in the water. It is characteristic of shelducks that they uncover the mussels hidden in the ground by trampling their feet. This movement is innate and is already shown by one-day dune boys. Downy cubs prefer to eat nereis , which are part of the many bristles, as well as mud shrimp such as Corophium volutator . Usually only fragments of larger shells are left behind as food remains of mussels and snails.
Reproduction
Shelduck are usually monogamous. Their partnership relationship often lasts for several years, although females and males often leave the breeding area at different times for moulting and wintering. In a study of partner loyalty among birds, shelduck had one of the lowest separation rates. Only 2.4 percent of existing couples broke up annually. The pairing takes place in the young bird groups at the beginning of April during the first year of life. Strong local loyalty is the rule with the shelduck. Many nesting sites have been occupied for around thirty years. Only shelducks that can successfully occupy a feeding ground come to breed. These are mostly the healthiest and heaviest animals within a regional population. The occupation of a feeding ground begins in late winter and ends when the chicks hatch. As a rule, female shelduck breed for the first time in their second year of life. Male shelducks that breed for the first time are between four and five years old. Non-breeding shelducks, on the other hand, stay in flocks all year round.
Courtship and nesting place
The courtship starts already in the wintering areas and has its climax in the phase between the occupation of the nesting place and the beginning of the brood. Unmated females are usually courted by several males. Often it comes to flights in a row , in which a flying female up to ten males follow. The courtship of the drake on the ground includes a vertical upward stretching of the head and neck as well as rotating pumping movements that are performed with the head and neck. With shelduck you can see a common malt, which distinguishes it from other geese. Several breeding pairs are found in one place, which is usually a little higher and offers good visibility. There are attacks and sham fights between the couples. The actual mating takes place in the water. It is preceded by beak immersion and sham cleaning by both sexes. The female signals readiness to mate by stretching out flat in the water.
Shelduck are cave breeders and prefer one to two meter long burrows at the end of which they build their nests. They prefer rabbit holes and other holes in the dunes, dams or embankments as nest locations. Shelduck occasionally also breed in holes in the ground under buildings or in the spaces between stone blocks. Shelduck have even been found in inhabited fox burrows. Shelduck and fox maintain for the period of breeding truce . Tubes that are too narrow, such as those found in rabbits' burrows, are scraped out from them. However, shelduck do not create their own burrows. If there are no suitable caves in the breeding area, the shelduck also accept more or less open places under bushes. The actual nest consists of a hollow lined with feathers and pale gray dunes.
The male indicates suitable nesting sites by walking towards them with his head stretched forward. However, the female ultimately chooses the nesting site. The shelduck's nesting area and feeding grounds are usually separate from one another. The nesting sites of several pairs can be close together like colonies, while the feeding grounds are up to 3 km away from the nesting site.
Rearing the young birds
The egg-laying usually begins nine weeks after the nesting site has been reoccupied. The clutch of a female usually contains between seven and twelve eggs. These are smooth-skinned, dull oval and creamy white. The eggs weigh between 75 and 77 grams. If the clutch is lost or the female is disturbed during incubation in such a way that it gives up the clutch, there is usually no additional clutch.
Only the female that develops a brood spot breeds . The female leaves the clutch about three to four times a day to eat and groom. However, the male stays near the breeding female and accompanies it on flights to the feeding grounds. The clutch and the young are defended by both sexes. The threatening gestures are similar to the courtship poses. Males aroused by potential danger show pumping head and neck movements. Very disturbed males rock back and forth with their whole bodies and call out excitedly. If an intruder comes too close, both sexes attack him by running towards him like a goose with bowed head and open beak and, if necessary, biting. Shelducks defend so scrim and boys against dabbling ducks , coots , gulls and even successfully against mammals . The young birds hide in the vegetation in case of danger or dive away on the water. Moulting adult birds dive in danger.
It is also relatively common for several females to mix with up to 50 eggs in one clutch. Even cross-species mixed layers with middle saws are occasionally observed. The incubation begins after the last egg has been deposited; the incubation period is between 29 and 31 days. The chicks hatch largely synchronously. In one study, day-old downy chicks found an average weight of 48.8 grams. At 21 days, the young birds weighed 715 grams. The young can fly after 42 to 44 days. As a rule, they can fledge after their 50th day of life at the latest.
Some of the young birds are looked after by the parent birds until they fled. A large number of the young birds will be abandoned by them before this point in time. These young birds form so-called " kindergartens ", which consist of young birds from different clutches. These kindergartens can count up to 100 young birds. They are often led by adult birds without breeding success. Such foster parents showed no signs of moulting at the end of September. Young shelducks usually reach sexual maturity from the age of 22 months.
Breeding Success, Mortality, and Age
The nest density has a significant influence on how many young birds in a clutch can fledge. In nests in colonies, downy chicks usually hatch from only 25 to 50 percent of the eggs. The low breeding success is probably due to the fact that densely packed nests are often disturbed by other breeding pairs. With less disturbed nests, the breeding success can be up to 90 percent. According to a Scottish study carried out over 13 years, around 35 percent of the hatched downy chicks fledged. This corresponded to a breeding success of one young bird per breeding pair per year. The main predators of the young shelduck include herring and black-headed gulls as well as crows and foxes. Unfavorable weather conditions also lead to high mortality rates.
The adult shelduck death rate is 20 percent per year. The average life expectancy is 4.5 years. The oldest shelduck, whose age could be reliably determined due to its ringing, was 14.5 years old.
Stock size and stock development
Reliable information on the size of the population is relatively easy to determine for shelduck, since outside of the breeding season they often gather in large flocks at traditional moulting and wintering sites.
The number of shelducks fell sharply, especially towards the end of the 19th century. In its Finnish and northern Swedish breeding grounds, it completely disappeared. The shelduck is now protected all year round in most of the northern and central European countries. Thanks to these protective measures, the species has increased significantly and has been expanding its range into the interior for several decades. As early as 1983, between 6,000 and 9,000 pairs were breeding in the Netherlands. For 1985 the population in Germany was estimated at 10,000 breeding pairs. According to the figures published by ornithologist Janet Kear in 2005, 300,000 hibernate annually in north-western Europe, 80,000 in western Asia, the Caspian Sea and the Middle East, 75,000 on the Black Sea and the Mediterranean, between 25,000 and 100,000 in central and southern Asia and in East Asia 100,000 to 150,000 shelduck. The stocks in Europe and on the Caspian Sea are increasing. The population increase in northwestern Europe is estimated at 50 percent for the period 1973-1993. There is evidence that population growth stalled between 1987 and 1996. Forecasts of the distribution development based on climate models assume that the shelduck will largely disappear as a breeding bird in Central Europe by the end of the 21st century because it will no longer find suitable habitats here. According to these forecasts, the distribution area will expand further north and Iceland and parts of Fenno Scandinavia will be colonized by this species.
supporting documents
literature
- Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds. Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 .
- T. Bartlett: Ducks And Geese - A Guide To Management. The Crowood Press, 2002, ISBN 1-852236507
- John Gooders and Trevor Boyer: Ducks of Britain and the Northern Hemisphere , Dragon's World Ltd, Surrey 1986, ISBN 1-85028-022-3
- Hartmut Kolbe: The world's ducks. Ulmer Verlag 1999, ISBN 3-8001-7442-1
- Erich Rutschke: The wild ducks of Europe - biology, ecology, behavior , Aula Verlag, Wiesbaden 1988, ISBN 3-89104-449-6
Web links
- Tadorna tadorna in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 18 of 2008.
- Videos, photos and sound recordings of Tadorna tadorna in the Internet Bird Collection
- Age and gender characteristics (PDF; 1.2 MB) by J. Blasco-Zumeta and G.-M. Heinze (eng.)
- Shelduck feathers
Individual evidence
- ↑ a b c d e f g Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0198546459 , p. 420
- ↑ The syllable brand appears in some animal and plant names in the sense of "burned" and indicates that the appearance is speckled with black or that part of the body is black. It is for such a reason that Brandknabenkraut and Brandfuchs have their names. Carl von Linné saw in the German name a reference to a life of this duck bird in the surf. In this case, however, the name would not be appropriate, because shelduck avoid the surf. Cf. Viktor Wember: The names of the birds in Europe - meaning of German and scientific names , Aula-Verlag, Wiebelsheim 2007, ISBN 978-3-89104-709-5 , p. 81
- ↑ Viktor Wember: The names of the birds in Europe - meaning of German and scientific names , Aula-Verlag, Wiebelsheim 2007, ISBN 978-3-89104-709-5 , p. 82
- ↑ Kosmos, Volume 69, 1973
- ^ Roy Brown, John Ferguson, Michael Lawrence, David Lees: Federn, traces and signs of the birds of Europe , 3rd edition, Aula-Verlag, Wiesbaden 2003, ISBN 3-89104-666-9 , p. 248
- ↑ a b c d e Hartmut Kolbe: The duck birds of the world. Ulmer Verlag 1999, ISBN 3-8001-7442-1 , p. 142
- ↑ a b c d e f Einhard Bezzel: BLV Handbuch Vögel , BLV Verlagsgesellschaft, Munich 1996, ISBN 3-405-14736-0 , p. 112
- ↑ Rutschke, pp. 322 and 323
- ↑ Collin Harrison and Peter Castell: Field Guide Bird Nests, Eggs and Nestlings , HarperCollins Publisher, revised edition from 2002, ISBN 0007130392 , p. 68
- ↑ Hans-Heiner Bergmann; Hans-Wolfgang Helb; Sabine Baumann; The voices of the birds of Europe - 474 bird portraits with 914 calls and chants on 2,200 sonograms , Aula-Verlag, Wiesbaden 2008, ISBN 978-3-89104-710-1 ; P. 73. This source was used for the onomatopoeic description of the voices.
- ↑ Bauer et al., P. 74
- ↑ a b c d e Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0198546459 , p. 421
- ↑ Bezzel, p. 113
- ↑ Klaus Janke / Bruno P. Kremer: The Watt: Habitat, Animals and Plants , Franckh, Stuttgart 1990, ISBN 3-440-06035-7 , p. 94
- ↑ Gooders and Boyer, p. 20
- ↑ Martin Flade: The breeding bird communities of Central and Northern Germany - Basics for the use of ornithological data in landscape planning . IHW-Verlag, Berlin 1994, ISBN 3-930167-00-X , p. 544
- ↑ Rutschke, p. 323
- ↑ a b c d e f g h i j k l Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0198546459 , p. 422
- ↑ Rutschke, p. 324
- ↑ Gooders and Boyer, p. 19
- ↑ Gooders and Boyer, p. 19
- ↑ Rutschke, p. 324
- ^ Roy Brown, John Ferguson, Michael Lawrence, David Lees: Federn, traces and signs of the birds of Europe , 3rd edition, Aula-Verlag, Wiesbaden 2003, ISBN 3-89104-666-9 , p. 119
- ^ Joan Roughgarden : Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley 2004, ISBN 0-520-24073-1 , p. 55
- ↑ Rutschke, p. 325
- ↑ Rutschke, p. 325
- ↑ Kolbe, p. 143
- ^ Roy Brown, John Ferguson, Michael Lawrence, David Lees: Federn, traces and signs of the birds of Europe , 3rd edition, Aula-Verlag, Wiesbaden 2003, ISBN 3-89104-666-9 , p. 104
- ↑ Collin Harrison and Peter Castell: Field Guide Bird Nests, Eggs and Nestlings , HarperCollins Publisher, revised edition from 2002, ISBN 0007130392 , p. 68
- ↑ Rutschke, p. 326
- ^ Hamburger Abendblatt - Hamburg: Burgfrieden among animals . ( Abendblatt.de [accessed on February 4, 2018]).
- ↑ Rutschke, p. 326
- ^ Roy Brown, John Ferguson, Michael Lawrence, David Lees: Federn, traces and signs of the birds of Europe , 3rd edition, Aula-Verlag, Wiesbaden 2003, ISBN 3-89104-666-9 , p. 104
- ↑ Rutschke, p. 325
- ↑ According to Rutschke, the maximum number of eggs is 15 eggs, s. P. 326
- ↑ Rutschke, p. 326
- ↑ Kear gives an average egg weight of 79.8 grams with a weight range of 65 grams to 92.5. 100 eggs were weighed.
- ↑ Rutschke, p. 326
- ↑ Gooders and Boyer, p. 20
- ↑ Rutschke, p. 326
- ↑ Kear, p. 422. The study by IJ Patterson from 1982 is cited : The shelduck, a study in behavioral ecology , Cambridge Univ. Press
- ^ Brian Huntley, Rhys E. Green, Yvonne C. Collingham, Stephen G. Willis: A Climatic Atlas of European Breeding Birds , Durham University, The RSPB and Lynx Editions, Barcelona 2007, ISBN 978-84-96553-14-9 , P. 75