Eider
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Eider pair ( Somateria mollissima ) |
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| Somateria mollissima | ||||||||||||
| ( Linnaeus , 1758) |
The Common Eider ( Somateria mollissima ) is a bird art that the family of ducks belongs (Anatidae). It is a large, bulky-looking sea duck that lives on the arctic coast of the Atlantic and Pacific. In Europe, it occurs mainly in Scandinavia. The breeding population on the North Sea coast is much smaller. In summer, however, large flocks of non-breeding eider ducks can be found in the Wadden Sea, which are joined by large flocks of moulting birds in late summer.
The German-language name of this duck became established through the down trade. Both the name for the bird and its feathers (eiderdown) are borrowed from the Icelandic æðr . In German usage it is sometimes referred to as the Eidergans or St. Cuthbertsente (see Northumberland coat of arms). The Latin name of the species Somateria mollissima indicates the soft and warming down of this duck species. Somateria is made up of two Greek words. Soma means "body" and Erion means "down", while the Latin adjective mollissima means "very soft". Translated, the scientific name means "very soft down body" .
description
With an average body length of 58 centimeters, the eider is slightly larger than a mallard and has an average body weight of 2.2 kilograms. Males of this species of duck usually get older, larger and heavier than females. The duck looks clumsy and clumsy on land, but it is a good swimmer and diver who can cope well with rough seas. Due to the high beak root, which goes directly into the forehead, the head of the eider looks wedge-shaped. This makes it easy to distinguish it from other duck species, as this profile only occurs in this duck species. During the flight, the eider can be clearly recognized by its sturdy shape, its thick and short neck and its striking head shape.
The eider shows a clear sexual dimorphism in the plumage . The breeding dress of the male bird, which, like all ducks, is called drakes , is predominantly white on the back and chest. The plumage on the chest is slightly tinged with pink. The belly, the flanks, the middle of the rump , the tail, the upper and lower tail and the top of the head are feathered black. On the nape of the neck, however, the plumage is light moss green. The neck feathers are slightly elongated so that they form a small hollow. The beak of the drake is yellow-green in the magnificent dress, otherwise blue-gray to green-gray. The outer arm wings are black, the inner ones are white and curved like a sickle. The male, on the other hand, wears dark brown plumage as a resting dress, which is interspersed in places with white plumage. The banding of the plumage is, however, a little less noticeable than in the females.
Throughout the year, the female wears inconspicuous dark to yellowish-brown plumage through which dense black plumage bands run on the body. The neck and head, on the other hand, are more monochrome brown. The plumage there has only a fine, brown-black dash. Its plumage resembles the females of many other duck species, but its striking head shape makes it easy to identify as an eider. The beak of the eider is greenish in color in the drake, that of the female eider is dark green. The tip of the beak is lighter and has a broad and horny tip. The eye color is brown in both sexes.
Young birds of both sexes resemble the females in their plumage. However, they are slightly darker in their plumage color and less strongly banded. Young drakes wear the fully developed splendor of the male in the 3rd or 4th year of life. Even in their splendid dress of the 2nd year of life, however, they clearly show the black and white contrast that is typical for adult drakes. At this point there are still feathers with a yellow-brown edge in the head and neck area. Parts of the dorsal plumage are still black-brown.
Distribution and existence
The eider is found along the northern coasts of Europe , North America and eastern Siberia . It breeds from the Arctic to the temperate climate zones , in Europe to the south about to the Wadden Sea and north-western France . On the North American Atlantic coast, the breeding area extends as far as Maine , on the Pacific the breeding area extends to southern Alaska . The focus of the breeding area of the eider ducks is on Iceland , where about 450,000 pairs breed, and on the Baltic Sea, where up to 600,000 pairs gather to breed. The eider duck uses small rock islands and skerries, overgrown or wooded islands, sheltered and quiet bays with flat banks as breeding grounds. The North American population is estimated at 750,000 to 1 million pairs. The IUCN estimates the total population of the eider at 2.5 to 3.6 million animals and classifies the species as "not endangered".
Birds from the northernmost breeding areas, for example from Spitzbergen , migrate to the temperate latitudes for winter, where they can form large flocks in suitable coastal waters. They winter with it in the southern regions of the range of this bird. The southern populations, however, are largely resident birds .
In winter, the eider regularly appears in small numbers even at a great distance from the sea on the larger alpine lakes. Since the 1970s there have been a few birds here. At Lake Zell in the province of Salzburg , brood evidence was even obtained in 1972. In Switzerland , too , the eider is a breeding bird in exceptional cases. In 1988 the eider duck brooded for the first time on Lake Zurich , and in the following years there were further broods on Lake Neuchâtel , Lake Lucerne and Walensee .
Lifestyle and diet
The sociable eider is one of the diurnal ducks with a pronounced ability to dive. It mainly lives on mussels up to a size of 40 millimeters and also eats snails , crustaceans and - in contrast to other duck species - fish . On the North Sea coast it mainly uses the mussel beds . Inland, the eider also eats the naturalized triangular clams . Vegetable food does not play a major role in this duck. However, the female also eats vegetables during the breeding season and particularly takes in the plants that grow near the nest.
The eider ducks catch mussels either by searching the tidal flats or by submerging them in the water. With the help of its powerful beak, it is able to tear off mussels from their base or to dig for them in the tidal flats. She also searches washed-up seaweed for aquatic insects , mussels and snails. The eider duck usually dives for clams to a depth of six meters and stays underwater for a little over a minute. She uses her wings to move underwater. Individual observations suggest that the eider can also reach much deeper seabeds. Dives at depths of up to 50 meters have already been observed.
The mussels are eaten with the shells. They are cracked in their strong gums; The duck then excretes the shell fragments as spits. The salt ingested with food is released again via the salt glands in the forehead. The eider specifically uses the tide changes to search for food in those marine regions that would not be accessible to them at high tide.
Reproduction
Courtship behavior
The females of the eider duck reach sexual maturity in their second year of life. However, only some of the two-year-old females are already brooding. The drakes, on the other hand, do not take part in courtship until they are three years old. Only then is the plumage of the adult drake largely developed. The drakes begin their courtship in December. Only in late winter do the females also take part. It is a social ball in which up to 10 males gather near one female. Young, not yet sexually mature drakes often stay in the vicinity of such courting drakes and are already showing their first courtship behavior.
During courtship, the male calls out a soft, muffled two- to three-syllable "ahoo" or hu-huúuu , which can be heard over the mudflats or the water. Young males do not yet have this reputation. Their call sounds hoarse and is onomatopoeic with gro-gro-ó . The female responds to the male's courtship calls with a gocking “goggoggoggog” and a creaking “krrr” .
The drake shows a characteristic body movement during courtship calls, which is sometimes described as " a bow backwards ". The drake leans its head far back and arches its chest. Usually several males court a female. Typical courtship postures of drakes include imposing swimming, in which the head is slowly turned from right to left, as well as stretching the body out of the water, in which the wings are spread backwards.
The female signals her willingness to mate by lying flat on the water. To mate, the drake swims on the duck, pushing it almost completely under the water and biting its neck with its beak. The pairing itself only takes a few seconds.
When they arrive in the breeding area, the majority of the females are mated. A couple is usually only bonded for one year. The locally loyal females mate occasionally with the same drake again in the next year when it returns to the same territory.
Brood
Eiders breed individually or in small groups. Often, however, there are also larger colonies in the breeding areas. For example, colonies of up to 1,000 pairs occur in Iceland. There can be two to three nests per square meter in suitable places. Eider ducks avoid steep banks, craggy rocks and places exposed to the wind. If the bank rises gently, the colonies are sometimes several hundred meters away from the coastline, so that the nests cannot be reached by the water even during floods.
The nest location depends on the respective local conditions. In breeding grounds without vegetation, the female builds the nest between the rubble. The nest is then nothing more than a shallow hollow that is sheltered from the wind. If there is herbaceous vegetation or bushes, the nests are in their protection. Occasionally the female also uses old seagull nests as a nesting place. Eider ducks also build their nests under the protection of trees on wooded islands. Eider ducks regularly use their old breeding grounds again, which affects the vegetation in their breeding area. Due to the detached duck droppings, the areas around the nests are herbaceous or overgrown with dwarf shrubs.
The breeding season is from the beginning of April to mid-May, depending on the region and weather conditions. The female usually lays four to six greenish-gray eggs in the nesting hollow, which is padded with belly down. The laying interval is 24 hours. If there are more than nine eggs in the nest, there are usually multiple clutches, which are common in eider ducks and other ducks and demi-geese that breed in colonies . If the female leaves the eggs during brooding, she covers them with down to reduce heat loss. Females, startled by disturbances, spray feces over the eggs when they fly. The eggs are incubated for a period of 25 to 26 days exclusively by the female, who fasts during this time. During this time the male stays near the nest. It even restricts food intake during this time, so that the drakes lose body weight. If the brood is sufficiently advanced, however, the males migrate to the moulting sites.
The young birds are led by the female after hatching. Swimming on the sea, the female looks after the young birds until late summer. This tour time is around 65 to 75 days. During this lead time there is often socialization with several families, which dissolve again as soon as the young birds are able to fly.
Migratory behavior
Eider ducks are relatively true to their location, some of which also overwinter in their breeding grounds. However, the majority of the population uses separate moulting and wintering roosts, with mostly only short distances being drawn.
For moulting, the birds move to their moulting roosts after breeding, many birds can then be found in the Wadden Sea, for example. The eider ducks, which are only able to fly to a limited extent, prefer areas in which they are largely undisturbed. Your escape distance from people increases during this time from normally 100 to 300 meters to 500 to 1,000 meters. The moulting move is therefore due to the fact that they need large resting areas. Coastal areas in which they otherwise stay, but which do not offer them sufficient opportunities to retreat, are avoided by the eider ducks during this time. The eider ducks now also use some of the larger alpine lakes as quarters for their moulting. During this time, eider ducks can also be seen on Lake Constance, for example , where up to a hundred birds congregate. Occasionally, the moulting quarters also serve as a wintering place - for example in the Wadden Sea. Occasionally, however, they seek out separate wintering quarters from October to November, from which they return to their breeding grounds from February to March. The birds that breed on Iceland and Svalbard reach their breeding grounds between April and May.
Predators and other natural causes of death
In the northernmost regions of their range, the snowy owl and the arctic fox are among the predators of the eider. In the more southerly distribution areas the eagle owl , the white-tailed eagle and the red fox are among the species that are able to kill the heavy duck.
Chicks and eggs are also endangered by seagulls and various corvids ( e.g. carrons , hooded crows and common ravens ). The young birds are also at risk from infestation with parasites , some of which have specialized in the eider as an intermediate host. For example, many of the fledglings suffer from flukes , which weaken the fledglings and sometimes even kill them. Eider ducks can also mass extinct if the sea coasts freeze in severe winters and the eider ducks are no longer able to reach the mussels on the sea floor.
Subspecies
In the large distribution area of the eider, six subspecies are distinguished, with transitional and mixed populations making the exact delimitation of the subspecies difficult:
- Somateria mollissima mollissima is the nominate form and has its breeding area in northwest Europe.
- S. m. faeroeensis is the smallest subspecies of the eider and can only be found on the Faroe Islands . The female of this subspecies is a little darker in color.
- S. m. borealis is the subspecies in which the male has an orange-yellow bill and the plumage of the female is more reddish-brown in color. This subspecies is mainly found in the Arctic North Atlantic.
- S. m. dresseri differs from the other subspecies in that it has a broad and rounded beak tip. This subspecies lives in the region from Labrador to Maine .
- S. m. sedentaria lives in Hudson Bay ; the female is noticeable for its gray-brown plumage.
- S. m. v-nigrum is found in the North Pacific region from the New Siberian Islands to Arctic Canada . It is the largest subspecies in which adult drakes have a wide, black V-mark on their chin and throat.
Human and eider
Hunting and other human influence
Hunting the eider is permitted in the Scandinavian countries with the exception of Iceland and in Russia . Sometimes it is hunted very heavily there. In Norway, however , the large breeding areas of the eider are now protected. It was partially protected in Iceland in 1786 and fully protected since 1847.
In addition to hunting, nestlings and chicks are lost when eider ducks are disturbed by humans. This applies above all to the coastal sections that are used heavily for tourism . Eider ducks also suffer from pesticide pollution of the seas . The Netherlands, for example, was populated by eider ducks from 1925. The population grew relatively quickly to 6,000 individuals, but then collapsed due to pesticide pollution. In oil spills , it is one of the species that die in large numbers due to plumage pollution and deprivation of food. In 1970, for example, 30,000 eider ducks were killed in an oil spill in the Kattegat .
Northumberland heraldic bird
One of the best known colonies of eider ducks is found in the Farne Islands off Northumberland , United Kingdom . The birds nesting there were the subject of one of the oldest bird protection laws in the world, which St. Cuthbert passed in 676 AD, hence the name St. Cuthbert's duck comes from. Today around 1,000 pairs of ducks breed on these islands. Since Saint Cuthbert is the patron saint of Northumberland, the eider became the heraldic animal of this county. Eider ducks are sometimes called Cuddy's ducks there, as Cuddy is the nickname for Cuthbert.
Economic use
The eider is the supplier of the eider down , which has a high heat storage capacity . For a long time, eiderdown was considered to be the best material that could be used to fill duvets. A targeted commercial exploitation of this eiderdown began as early as the 10th century.
Until the middle of the 20th century, eiderdown was one of Iceland's most important export items. Even today, the eider is of greater economic importance there due to this down. Pillows and duvets are filled with the soft and warm down. The harvest of this down is quite compatible with the protection of species, since normally the feathers are used with which eider ducks pad their nests and these feathers can be harvested after the young ducks have left the nest. A down nest weighs on average only around 20 grams. Cleaning the down from parts of plants is a time-consuming work that takes hours. Only about 1.5 grams of usable down per nest remain after this cleaning process, so that around 700 nests are harvested to obtain one kilogram of tradable eiderdown.
Keeping eiders
Eider ducks are increasingly kept in enclosures due to the attractive brood dress of the males. They are peaceful birds that get along well with other waterfowl. For their wellbeing, however, these ducks need sufficiently deep ponds with clean water.
Individual evidence
- ↑ Kluge, Etymological Dictionary, entry "Eider"
- ↑ Rutschke, p. 278
- ↑ Rutschke, p. 279
- ↑ Rutschke, p. 280
- ↑ Klaus Janke / Bruno P. Kremer: The Watt. Habitat, Animals and Plants, Stuttgart: Franckh 1990, p. 93, ISBN 3-440-06035-7
- ↑ a b Rutschke, p. 281
- ↑ a b 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. 65 and p. 66
- ↑ a b Rutschke, p. 282
- ↑ a b Gooders and Boyer, p. 110
- ↑ Stephen Moss: Birds Britannia, Why the British fell in love with birds , HarperCollins Publisher, London 2011, ISBN 978-0-00-741344-7 , p. 72 and p. 73
- ↑ a b Sale, p. 115
literature
- Franz Robiller: Lexicon of bird keeping. Landbuch, Hannover 1986. ISBN 3-7842-0322-1
- Eckart Pott : Birds by the Sea. Landbuch, Hannover 1987. ISBN 3-7842-0364-7
- Steve Madge : water fowl. An identification book of the swans, geese and ducks of the world. Paul Parey, Hamburg and Berlin 1989, ISBN 3-490-19018-1 .
- T. Bartlett: Ducks And Geese - A Guide To Management. Crowood, Marlborough 1986, 2002. ISBN 1-85223-650-7
- 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, Stuttgart 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
- Richard Sale: A Complete Guide to Arctic Wildlife , published by Christopher Helm, London 2006, ISBN 0-7136-7039-8
Web links
- Somateria mollissima in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 4 of 2009.
- Videos, photos and sound recordings about Somateria mollissima in the Internet Bird Collection
- Eider duck feathers
