Mute swan ( Cygnus olor ) with chicks
|( Gmelin , 1789)|
The Mute Swan ( Cygnus olor ) is a bird art , within the Anatidae (Anatidae) for genus of swans ( Cygnus ), and to the subfamily of geese belongs (Anserinae). As a semi-domesticated bird, it is native to large areas of Central Europe today. He prefers to stay on lakes, park and fish ponds, in shallow sea bays and in winter also on open rivers. The species is named for the black hump at the base of its beak. Swans have few predators in Central Europe. Mute swans are hunted species in Germany , and several thousand are shot every year. A population regulation occurs due to the pronounced territoriality of the swans during the breeding season as well as due to losses in severe winter months.
Adult mute swans
The mute swan can reach a body length of up to 160 centimeters and a wingspan of 240 cm. Adult males usually weigh between 10.6 and 13.5 kilograms, with a maximum of 14.3 kg in males. The body weight of the females remains significantly below and is usually no more than 10 kilograms. This makes the mute swan the largest native water bird in Central Europe and one of the heaviest birds in the world that can fly.
Mute swans often live to be between 16 and 20 years old. The oldest swan ever discovered was found near the Danish port city of Korsør in early 2009 . A ring with the identification “Helgoland 112851” (attached on February 21, 1970 in Heikendorf on the Kiel Fjord) was found on him, which means that he was 40 years old.
Adult birds have uniformly white plumage. It can be distinguished from other swans by its orange-red colored bill with a black tip and root. The black beak hump is most developed in males during the breeding season. Females are also slightly smaller on average, otherwise there is no noticeable sexual dimorphism . The feet and legs are black in both sexes. The eyes are hazel in color.
Mute swans often have their necks curved in an S-shape. During the breeding season, an imposing posture can often be observed in which the neck is strongly bent back, the beak is lowered and the wings are lifted like a sail.
Mute swans moult their plumage once a year. You are then unable to fly for a period of six to eight weeks. In breeding females, moulting begins while the downy chicks are small. The moulting of the males of such successful breeding pairs begins when the flight feathers have grown back in the female.
Downy chicks and young birds
Downy chicks have light silver-gray plumage with a white underside. The beak is black, the feet and legs dark gray. Young birds that are not yet fully grown have dull gray-brown plumage that becomes increasingly lighter in the course of the first year of life. The beak is still gray to flesh-colored, becoming increasingly orange. The brown feathers are gradually lost. The young swans have completely white plumage after they have fully moulted in their second year of life.
The color morphs immutabilis
No subspecies are described for the mute swan. However, a distinction is made between a color morph , which is referred to as immutabilis or " Polish swan ". This color variant has no melanin , so that the downy chicks and young birds appear white. They have pink to yellow feet and legs up to sexual maturity and can be identified by this characteristic. Adult swans of this color variant have light gray to flesh-colored legs. The occurrence of this color variant can be observed more frequently in mute swans breeding in Eastern Europe as well as in swans introduced in the USA and occurs more frequently in female mute swans than in males.
It is considered likely that this color morph was purposefully bred in historical times, as there was a trade in swan skins for a time and the hides of the immutabilis morphs were previously salable. Adult mute swans react more aggressively to the white downy chicks and young birds and these are driven out of the territory earlier than gray-brown young birds. Their mortality rate is therefore higher compared to the normal colored young birds. The Immutabilis variant, however, becomes sexually mature earlier.
Voice and instrumental sounds
Mute swans have an extensive and variable repertoire of voices. However, they are less loud and their calls are less pleasant than those of other swans. Excited swans make a hard, loud hueiarr or kiorr . Their sounds also include a low krr-krr-krr or tru-tru-truu . When a flying predator approaches, a female swan leading the young can hear polysyllabic moaning sounds that can be onomatopoeically described as krrr-wip-wip , chh or a deep chorr . Even after mating, mute swans make gurgling, creaking and whistling noises.
One of the instrumental sounds of the mute swans is the rhythmic throat plunging, during which they gurgling exhale. They show this behavior immediately before mating. Their metallic whirring to singing flight noises are typical of the species, which are missing in whooper and dwarf swans .
Mute swans need a long start-up phase before they can rise into the air. The start of the mute swans is full of power and dynamism. For a while they run across the water and flap their wings. Once they are up in the air, their wings beat slowly and powerfully. However, you only gain altitude very gradually and the flight seems cumbersome overall. The rhythmic flight noise can be heard from afar.
The mute swan was originally found in northern Central Europe , southern Scandinavia , the Baltic states and the Black Sea . In Asia, its occurrence ranges from Asia Minor to northern China . The breeding populations in Western Europe are exclusively due to abandoned and feral birds. The mute swan may also never have been native to some regions of Central Europe.
The mute swan was heavily hunted until the end of the 19th century, so that it was almost only found in the wild in the Baltic Sea region. At the same time, however, there were repeated suspension actions that were carried out in Great Britain well before the 16th century and in Central Europe from around the 16th century. An intensified settlement took place from around 1920. It was not until the 1950s, however, that there was a sharp increase in the population in Central Europe. The remaining stock of mute swans as well as a renewed wilderness of park swans and in some cases also targeted settlements were involved. As the settlement density increased, the area of distribution expanded to the south and southeast. In addition to a temporary complete sparing of the hunt, the failure to harvest eggs, increasing feeding, especially in winter, and a resulting reduction in the escape distance, which has also led to the settlement of busy banks and still waters, have contributed to the increase. Today the mute swan can be found in many ponds , lakes and rivers in the British Isles and in southern Central Europe. Naturalizations were also available in North America , for example in the New York region and in the state of Michigan, as well as in Australia and New Zealand. In New Zealand, where it was first introduced in 1866, it is now found in small numbers in some wetlands, on several rivers and on the seashore. In the early 1990s, the number of mute swans found in New Zealand was less than 200 wild birds.
While Central European birds stay in the area in winter , mute swans migrate from the northern edge of the European area, for example from Scandinavia, and those from Central Asia south in winter. Central Asian mute swans then overwinter in Iran, for example . In the case of the Central European swans, however, moulting takes place. Thousands of swans can be found on the IJsselmeer and they change their plumage there. During this time, the mute swans are unable to fly for a few weeks.
The habitats of mute swans were originally steppe waters, brackish water marshes and slow-flowing rivers. They basically prefer eutrophic shallow lakes. Introduced populations can also be found mainly on shallow lakes and regularly colonize bodies of water in human proximity. They can be found, for example, in sewage, park and fish ponds that are eutrophic to hypertrophic . However, they often stay in sheltered bays on the coastline and on rivers.
The mute swan lives from aquatic plants and the small animals attached to them ( mussels , snails , water isopods ), which it reaches with its long neck under water by gudging. It reaches depths of 70 to 90 centimeters. On land, it also eats grass and cereals. This occurs especially in late winter when the underwater vegetation no longer offers enough food. They especially prefer rapeseed fields. Grassland, on the other hand, is rarely used as a feeding area by swans. The feeding phase begins around three hours after sunrise in winter and only ends when it gets dark. In spring the proportion of aquatic plants in the diet increases again. In summer, the foraging takes place exclusively on bodies of water. Mute swans are unable to prey on animals that swim freely.
The food requirement of the mute swans is very high. During the moult, adult mute swans eat up to four kilograms of aquatic plants. The food requirement of mated females is particularly high. These hardly eat during the breeding phase and therefore have to build up appropriate food reserves.
Mute swans bind for life. They reproduce on land for the first time in their third or fourth year of life. Especially in the breeding season, which begins in March, the male mute swans are very aggressive and defend their territory emphatically against people who are approaching and emit hissing sounds.
The nest is built by both parent birds near the water, on small islands or in shallow water over the course of about ten days. It is a large structure made of sticks, reeds, and cane. The actual nest hollow is only very weakly padded with down. The nest building is initiated by the male, which the female adult bird later joins. A clutch usually consists of five to eight dirty yellow-brown eggs , which are laid about 48 hours apart . In very rare cases, a clutch can contain up to twelve eggs. The breeding season is 35 to 38 days. It mainly breeds the female. The chicks are precocial . Day-old chicks weigh an average of 220 grams.
Both parents look after the young for four to five months until they are fully fledged. Females in particular occasionally carry the downy chicks between their wings on their backs. This protects the downy chicks, among other things, from being stalked by large pike . Parental brood care includes tearing out underwater vegetation that the downy chicks could not reach without the parent birds. The young birds fledge at an age of around 120 to 150 days.
The mortality rate among downy chicks and young birds is very high. Studies in the UK have shown that between 29 and 49 percent of clutches are lost before the chicks hatch. A common cause is human vandalism. The high mortality also persists in the first years of life, so that only about eleven percent of the downy cubs ever breed on their own.
The total population of the mute swan is estimated by the IUCN at 600,000 to 620,000 animals. The species is considered harmless. An estimated population of 250,000 mute swans lives on mainland Europe. Ireland and Great Britain have a total population of 47,000 mute swans. Another 45,000 mute swans can be found in the Black Sea. Between 260,000 and 275,000 mute swans live in West and Central Asia to the Caspian Sea. In East Asia, however, the population is very small. Between 1,000 and 3,000 mute swans live there. There are 14,700 mute swans in North America.
A very complicated mechanism of population regulation can be observed in mute swans. This is a density-dependent inventory regulation. Although mute swans increased significantly in Central Europe after the Second World War, there is no longer any further growth, although the increasing winter feeding has reduced the loss during the winter half-year.
The population-regulating effect is, among other things, the high proportion of adult and therefore sexually mature mute swans that do not breed. The proportion of adult birds in many populations makes up more than 50 percent of the adult animals. This is partly due to increased food competition. In regions with a very high density of swans, the individual swans are often not optimally fed and do not have the physical condition that is necessary to brood. Another factor is that many mute swans need a large breeding territory and not all swans can fight for one.
In some places, mute swans also breed in colonies. These are predominantly the semi-domesticated stocks. However, the breeding success of these colony-breeding populations is low. On average over several years, individually breeding mute swans raise 2.6 young per brood. In colony breeding pairs, however, only 0.9 young swans grow on average. The clutch size is almost identical with 5.6 and 5.2 eggs respectively. The low breeding success of colony-breeding mute swans is partly due to the high loss of eggs caused by the great unrest among the mute swans. Constantly dealing with mute swans breeding in the neighborhood will break many eggs. At the same time, the mortality rate among the hatched colony breeders is significantly higher than among individually breeding pairs, since their nest location is in less optimal locations. This is particularly noticeable in windy summers, when the death rate of young swans in colonies is particularly high due to the weather. Young swans from breeding colonies are often in a poorer nutritional state than those from single brooders. Because of this, fewer colony juveniles survive their first winter.
In addition to hunting (see below), there are a number of other dangers for mute swans. Natural deaths occur in harsh winters. Cases of lead poisoning from lead shot and fishing lead have been detected. There are accident victims on power lines through approaches. There are also deaths from diseases, including botulism .
In the past there were clutch losses through human egg collection and deliberate clutch destruction for stock control. Due to human interference, the clutch can be abandoned. Fluctuations in the water level in the breeding water can also lead to a loss of eggs.
In Germany, the mute swan is subject to hunting law and can usually be shot from November 1st to February 20th of the following year. Individual federal states such as Thuringia and Hesse as well as the city states of Bremen, Hamburg and Berlin do without a hunting season. In Austria, too, the mute swans are among the hunted animal species . In Switzerland, on the other hand, mute swans may only be hunted with special permits if they cause damage. Several thousand mute swans are shot in Germany every year. Apparently there are currently no nationwide shooting figures. In Bavaria, 657 mute swans were included in the route list in the 2010/11 hunting year. In Schleswig-Holstein there were 676 mute swans on the route list in the 2010/11 hunting year. In the hunting years 2008/09 and 2009/10 473 and 752 mute swans, respectively, were listed in the hunting route of Schleswig-Holstein. Usually such as B. in Schleswig-Holstein mute swans can only be hunted with a bullet.
In the route list also each case Wild contain (Todfund without hunting action). The proportion of game birds on the hunt varies greatly. In the hunting year 2010/11 z. B. the hunting route in Schleswig-Holstein 22 percent fall game.
In Central Europe, nature conservation demands that the mute swan be abandoned because of the risk of confusion with whooper swan and dwarf swan . Since Central Europe is of great importance as a resting area for whooper swans and dwarf swans, accidental shooting of these species should be ruled out.
Mute swan and human
In Great Britain the mute swan had royal status since 1186 at the latest and the first swan master was appointed in 1361. In 1482, a law passed by parliament, the Act of Swans , stipulated that only landowners above a certain size of their property were allowed to keep swans. Of the original 900 owners, only three are left: the Venerable Society of Dyers, who mark the beaks with a notch during the annual swan count, the Swan-Upping in July, the Venerable Society of Vintners, which gives their swans two notches, and the monarch who owns all unmarked animals. Nowadays, all of this is only of ceremonial importance. The royal possession of swans does not apply to the Orkney and Shetland Islands , where the Udal Law , which goes back to the Vikings , according to which swans are publicly owned.
Since 1971, the mute swan has had further protection under the Creatures and Forest Law Act .
In Hamburg, the mute swan is viewed like a heraldic animal. It is always associated with the Alster and can be clearly seen in the Alster-Touristik GmbH logo . There is a "swan father" who has been looking after the Alster swans since the 17th century . His tasks include catching the swans of the Alster and the surrounding canals in autumn, bringing them to their winter quarters, the Eppendorfer mill pond, supplying them with food and releasing them again in spring.
Protected since 1926, the mute swan was raised to the rank of national bird in Denmark in 1984 after a survey.
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