Pond claw
| Pond claw | ||||||||||
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Common pond rail ( Gallinula chloropus ) |
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| Scientific name | ||||||||||
| Gallinula chloropus | ||||||||||
| ( Linnaeus , 1758) |
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The Teichralle ( Gallinula chloropus ), also Teichhuhn called, is a species from the genus of Moorhen (or pond chickens, gallinula ) in the family of Coot (Rallidae). It occurs with at least 16 subspecies in the temperate, subtropical and tropical climates of Eurasia and Africa.
The European breeding population is estimated to be at least 900,000 pairs. In most European countries, stocks are stable. In Germany, however, significant population declines and area losses have been ascertained in recent years, so that the pond rail is currently (from 2006) on the early warning level of the Red List of Endangered Species .
Surname
The scientific species name Gallinula chloropus means "green-footed chicken" and alludes to the color of the legs of this rail. In the German-language ornithological literature, the term "common moorhen" was used in the 19th century. At the beginning of the 20th century it was called "green-footed moorhen" or just moorhen - a name that is still used today. Zoologically more correct is the name pond claw, which is gradually gaining acceptance as the species is a typical representative of the claws .
description
Characteristics of adult birds
The subspecies of the pond claw, which occurs in Europe, is somewhat smaller than a partridge with a body length of about 33 centimeters . The adult birds are dark olive-brown on the upper side of the body, dark gray-black on the head and neck as well as the underside of the body. Males and females look the same, differ only slightly in size and weight. They have a red forehead plate, a red bill with a yellow tip and red eyes. The short tail with a black and white undercover is often stilted upwards. On the underside, the plumage is slate gray, the flanks striped white. Feet and legs are yellowish green; The legs have a red band above the intertarsal joint . The bird is noticeable because it constantly rocks its stilted tail while swimming and nods its head rhythmically.
Chicks and young birds
The newly hatched chicks have a red-orange bill with a yellow tip. In the first few days, they also have a yellowish-white cusp, the so-called egg tooth, at the tip of the upper beak . The front plate is conspicuously red. The downy dress of newly hatched chicks is black with a greenish sheen on the back. A bright blue stripe runs above the eyes like an eyebrow. When young, the pond claw is gray-brown on the top and gray-white on the underside. The chin and throat are also dirty white, with the sides of the neck shimmering a little rusty. In the transition dress between youth dress and the plumage of an adult bird, the head and back are olive brown. The rest of the upper side resembles the resting plumage of adult birds. The base of the beak then gradually begins to turn red. In the spring of the year of birth, the beak is already as red as it is typical for adult birds.
Vocalizations
The most frequently heard call is a kurr or krürr . The alarm calls are short and clipped and are mainly used to warn the young birds. These calls sound different depending on the situation - depending on whether a potential enemy is swimming near, is on land or a bird of prey appears in the sky. Scare calls are also short-syllable. The pond claw's threatening call repertoire also includes a hissing throat sound, which can occasionally be heard when the bird is surprised at the nest or when a conspecific is in the breeding area. It often precedes an attack.
A faint beeping can be heard from the chicks just before they hatch from the egg. They maintain contact with the parent birds with a range of different vocal feel and begging sounds. These sounds are paraphrased with kee-ip , which sounds very shrill in certain situations. Fleeing cubs call out a loud ptili ptili that sounds fearful to the human observer , the more the syllables of which are strung together, the more the young bird feels in danger.
distribution
Pond claws live in Europe, in Asia eastwards to Sulawesi and Sumbawa , in Africa, on Madagascar and the Seychelles , Mauritius and Réunion , on Hawaii and in North and South America. You are missing in Australia.
The subspecies and their distribution
Depending on the author, a different number of subspecies is separated within the very large distribution area. In general, the number of described subspecies has decreased in the course of the 20th century because certain proven differences in color and size are no longer viewed as subspecies characteristics. Engler (2000) assumes 14 proven subspecies and two island forms whose subspecies status is controversial. In addition to the nominate form Gallinula chloropus chloropus , which also occurs in Europe and whose range is shown in more detail in the next section, these are in detail:
- G. c. indica is found in the south of the Arabian Peninsula , in Iraq , Kashmir , southern Tibet , in the south and east of China , in Japan , on the Ryūkyū Islands , Taiwan , Hainandao , in front and rear India , on Sri Lanka , in Burma and in the north from Malacca to Tenasserim .
- G. c. orientalis lives in the south of Malacca , on Sumatra , Java (island) , Bali , Lombok , Sumbawa , Flores , Kangean , Borneo ( Kalimantan ) and Sulawesi .
- G. c. lozanoi is restricted to the Philippines .
- G. c. guami lives on the Mariana Islands .
- G. c. meridionalis lives in Africa from the tropics to the Cape Province as well as on the two islands São Tomé and Annobón .
- G. c. pyrrhorhoa occurs in Madagascar , Réunion and Mauritius .
- G. c. sandvicensis is native to Hawaii .
- G. c. cachinnans is found in North and Central America , the Bahamas, and the Bermuda and Galapagos Islands .
- G. c. cerceris lives in the Greater and Lesser Antilles .
- G. c. pauxilla is common in northern and western Colombia , western Ecuador and along the north-western coast of Peru .
- G. c. galeata occurs in Uruguay , northern Argentina , Paraguay , Brazil , eastern Bolivia , Guayana , Trinidad and northern Venezuela .
- G. c. garmani is limited in its distribution to the highlands of Peru , western Bolivia , northwest Argentina and northern Chile .
- G. c. correiana is another subspecies living on islands and can be found on the Azores islands Terceira and Faial .
- G. c. seychellarum and G. c. barbadensis are two island forms whose classifications as subspecies are still being discussed. You live in the Seychelles or Barbados .
The distribution of the nominate form Gallinula chloropus chloropus
Gallinula chloropus chloropus is the nominate form of the pond claw described by Carl von Linné in 1758 . Their distribution area extends from Great Britain and the Shetland Islands over southern Norway, southern Sweden and southern Finland and Saint Petersburg , Nizhny Novgorod to Tomsk in western Siberia . It is also represented in the west of the Altai , Kazakhstan , Djungary , Tianshan , Kashmir and western Turkestan . In the south, the breeding area extends over Morocco , the west of the Sahara to the plateau of the Atlas Mountains in Algeria and the north of Tunisia . It is also found as a breeding bird in northeast Libya , in the Nile Delta and in Sinai as well as in Israel , Lebanon , Syria and Iraq .
In Europe the species is a typical inhabitant of the lowlands. The altitude distribution in the mountainous region fluctuates regionally. The breeding sites in central Germany are seldom at altitudes above 600 meters; In Switzerland, on the other hand, the species breeds up to 800 meters above sea level. The highest recorded brood so far took place on Lake Sils at an altitude of 1,800 meters above sea level .
Migratory behavior
Depending on the respective climatic conditions, the pond rail is a migratory , stationary or line bird . In general, it can be said that there are migratory birds under the ponds of the western and central European countries, which cover greater distances to their wintering areas. The proportion of birds for which this is true is higher in Eastern and Northern Europe. Pond reels that breed in Scandinavia overwinter mainly in France as well as in Spain and on the British Isles . Occasionally these breeding birds have also been found in northern Sudan , on the Persian Gulf , in Mali or in Senegal . Pond reels that breed in eastern Germany use an area as a wintering area that stretches from western Germany, the Netherlands , Belgium , Spain, France to Italy . Dutch breeding birds, on the other hand, are mostly short-distance migrants , which often come to Belgium in winter.
British breeding birds are predominantly resident birds for which wintering on mainland Europe has not yet been proven. Little is known about the migration behavior of the Asian subspecies. In the case of European pond reels, which are migratory birds, the migration from the breeding area takes place predominantly in the period from September to November. In suitable areas, pond racks gather to form so-called winter groups. These dissolve before the beginning of spring and move back to their breeding areas from the beginning of March to April. Pond claws fly on their train especially at night.
habitat
The optimal habitat of a pond rail consists of a strongly eutrophic and shallow body of water with a dense reed vegetation on the bank and larger groups of floating leaves on the open water surface. Due to its high adaptability, the species can also be found in waters that do not correspond to this optimal habitat. It also uses smaller pools and water holes with a water surface of 20 to 30 square meters and can be found in peat extraction areas , on sewage fields , along floodplains and slowly flowing rivers as well as clay and gravel pits . Gallinula chloropus is also one of the animal species that has conquered urban areas as a habitat and can be seen there in gardens , parks and zoos if they offer sufficient water. It makes only minor demands on the water quality. The presence of suitable riparian vegetation is more important than this.
Food and subsistence
Pond claws are omnivores whose food spectrum is primarily determined by their respective habitat. Among other things, they eat the seeds and fruits of marsh and aquatic plants , the buds of willow and poplar trees , tips of grass as well as insects , mollusks and other small animals. The vegetable food predominates. For their search for food, pond rails also use meadows and pastures in the immediate vicinity of bodies of water. Outside the breeding season, the space in which the pond claws look for food expands. They can then occasionally also be observed in gardens, on fields, or on seed and stubble fields that are not in the vicinity of water. They then primarily pick up freshly-raised seeds from winter rye, for example . In gardens they also eat freshly sprouting spinach or cabbage .
The animal diet consists of snails , arachnids , imagines of dragonflies and beetles as well as aphids and various types of beetles. Fish fry and small fish are only exceptionally part of their food spectrum. However, they peck at dead fish that float on the surface of the water. It has also been observed that they eat bird carcasses and occasionally eat eggs from other bird species.
Reproduction and reproductive behavior
Courtship behavior
In migratory birds, pair formation usually begins before the winter groups break up before the beginning of spring. Usually it is the female pond claw that chooses a male as a partner. Fierce fights take place among the females and the winners of these arguments usually choose the males who are particularly well nourished. The nutritional status of the male is taken by the females as an indication of how well they are suitable for later breeding and for territorial defense.
In the case of resident birds under the pond reels, pair formation and courtship often begin as early as October to December and thus much earlier than in the individuals who move to wintering areas. In the case of resident birds, it happens that pairs form that have lived together for several years.
The male swims towards an approaching female in an imposing position and a rhythmic mock pecking against the surface of the water. If the female turns away, the male begins to drive it until it turns around after a short swim and also begins to perform a dummy peck. Chase swimming and mock pecking against the surface of the water, which are part of the pairing behavior, can be repeated up to eight times. A completed pair formation can be recognized by the fact that the two birds do not keep an individual distance from each other and look after each other's plumage.
The nest
In Central Europe, males begin to select suitable nesting sites in their territory at the end of February at the earliest. Nests with three different functions can be built during a breeding season. On the one hand, this includes so-called courtship platforms, which are nest-like structures on land or on solid surfaces just above the water level. Up to five such courtship platforms, which the males occasionally use as a sleeping place during the breeding season, can be created in one area. The actual nest that the clutch takes up is created around a week before the first egg-laying. The vast majority of pairs of pond brackets build two nests before they decide on one. The second nest is very often used later as a resting place for the parent birds. Both sexes are involved in the construction; the nest foundation is mainly built by the male, the lining of the nesting trough is largely done by the female. The nests are not yet completed when the eggs are first laid. The nest is largely completed while the eggs are being laid and during the incubation period, as green plant shoots continue to be inserted into the nest. A large number of the nests have a " canopy " made of plants that protect the nest from being discovered by egg and chick robbers.
In most cases, the male builds at least one resting and sleeping nest for the young birds shortly before they hatch. An old courtship platform often serves as the foundation of such a boy's nest, which is similar in appearance and construction to the casual nests. However, it is erected very quickly, so that it is less stable.
Clutch and young nests are usually well hidden in the bank vegetation. If these nest forms are used on the surface of the water, sedge bulbs , reeds or tree roots or stumps lying in the water serve as anchoring points. As cover plants then serve rushes , Kalmus , bur reed , bulrush , reed canary grass (see Fig.) Or the marsh iris . Occasionally, nests are created above the ground in dense shrubs , in the forks of trees or in climbing plants. Here, too, the nest location is rarely more than 50 centimeters above the ground.
Brood
The beginning of the breeding season varies from region to region. In Central Europe, however, pond rails usually start laying eggs in mid-April, when the nest is not yet ready. The females usually lay their eggs in the evening between 7 and 10 p.m.
The eggs have a fine-grained, firm shell that is smooth and has a faint sheen. They have a yellowish-brown to gray-beige base color, have chestnut brown to blackish-purple spots and weigh about 20 grams. The clutch consists of five to eleven eggs. Pond rails often breed a second time and, under optimal conditions, also lay a third clutch. The second and third clutch, however, each contain fewer eggs. In addition to the losses due to predators (see below), there are also clutch losses mainly due to storms in which the eggs lie in the water for too long, so that they cool down so much that the embryos die.
The eggs usually start to incubate before the clutch is complete. The breeding period is between 19 and 22 days, and both parent birds are involved in the breeding. According to the latest research, the males breed predominantly at night, and their share in the breeding business is greater than that of the female. The separation between the two parent birds takes place without any recognizable ceremony.
Eggs from Moorhen are already in the nests of partridges , Bless Coot , ruddy ducks and black-headed gulls were found. However , it is not yet sufficiently proven whether pond claws purposefully cause brood parasitism .
The chicks
Two to two and a half days before the chick has freed itself from its egg, a first small crack appears in the shell. This is followed by further cracks over the course of the next day, all of which are regularly distributed along the air chamber of the egg. From the time you can first see the chick's beak through a small hole in the egg shell, it takes about two to eighteen hours before the chick has fully hatched. The chicks or dune young often stay in the nest for one to three days before they leave it for the first time. However, you can swim independently from the first day of life. The chicks can also dive from the age of five. They are able to hide under water and on aquatic plants. Only the head protrudes out of the water to the eye region. From the 10th day of life they can look for food independently.
Both parent birds are involved in raising and caring for the chicks. The female incubates nor the remaining egg, then it is the male who takes care of the boys and possibly the boy's Nest hudert . If there is a subsequent brood, which can begin eight to ten days after the last chick hatches, it is also the male who leads the chicks. The chicks are fed by the adult birds holding their beak slightly to the side in front of the tip of the boy's beak. This ingests the food by pecking at the parent's lower beak.
The development to a young bird
Between the 20th and 21st day of life, the color of the head that was typical for the chick gradually disappears. On the 28th day of life the young birds have completely lost their downy clothing; the feet are now gradually turning green. Between the 31st and 45th day of life, the wings and wing covers gradually develop. From the 45th day of life, they are usually no longer fed by their parents. At 49 days the young birds are fully grown and can already fly a little. The growth of the hand and arm wings as well as the tail is not completed until the 60th day of life, so that only then do they have their full ability to fly. The juvenile moult is in the 15th to 18th week of life.
Defense of the breeding ground
Pond racks defend their immediate breeding area against conspecifics as well as against other animals. Defense requires a very broad repertoire of actions. A gray heron approaching the nest is threatened by a pond claw, for example, first with its head stretched forward and wings open, and would then run or swim threateningly towards the gray heron. Conflicts between gray herons and pond claws occur regularly, and the pond claw often manages to keep gray herons - which the chicks would eat - away from the nest. The pond claw shows a similar behavior towards mute swans . Sometimes she even jumps on her head or neck.
Pond claws also show a similarly aggressive behavior towards birds of the same size or smaller. Ducks attack them regularly when they get too close to the young birds or the clutch. There are also several cases in which pond claws killed the chicks of other bird species. This is done by hoeing on the head and neck, as well as trying to push the other birds underwater. The pond claw also shows an extremely aggressive behavior towards humans, especially during the incubation of the eggs. During nest inspections, ornithologists have been hissed at ponds with threatening noises and occasionally their fingers have been bitten.
Predators
The following are the species of animals that are typical predators in Europe.
Pike are one of the species that the pond claw chicks regularly devour. However, adult pond claws only occasionally fall victim to very large pike, as demonstrated by findings in the stomachs of pike. The catfish is likely to pose a threat to the pond rails in a similar way.
The marsh harrier , which uses a similar habitat, is one of the typical pond claw hunters . For the North Frisian island of Föhr , it has been shown that high marsh harrier populations and the chances of a young bird to reach the second year of life are negatively correlated : In the years when there is a high density of these birds of prey , hardly a chick experiences the second Age. The hawk and the white-tailed eagle are also among the birds of prey that regularly strike pond claws as prey. Common buzzards and peregrine falcons also occasionally catch pond claws. Among the owls , it is the eagle owl that most often catches pond claws. Where the area of distribution is covered with the snowy owl , it also hunts pond claws. However, include only occasional hunters of Moorhen tawny owl , forest and short-eared owl . Gull species like herring gull and black-headed gull are also such occasional hunters. Chicks are particularly endangered by them, but adult pond claws that are weakened can also fall victim to them. Little owls and black-headed gulls can only prey on chicks.
The pond claw also has a large number of predators among mammals. Hedgehogs , weasels and wild boars will eat the eggs when they can reach them. Brown rats , raccoon dogs , pine marten , ermine , mink , otters and feral cats and dogs also eat the chicks and occasionally beat adult birds.
It is rather bizarre that a pond claw was once almost a victim of common toads . Engler (2000) points to a case in which an adult male was fished out of a pond with toads clinging to its neck and head, thereby choking the bird. The cause of this unusual incident is the pronounced clinging reflex of the male frogs during the spawning season .
Behavior towards predators
When an enemy approaches, pond claws usually flee into the dense bank vegetation and stay there until they feel safe again. If they are on land, they usually flee continuously or using the so-called running flight . Escape in flight is rare.
If the birds are in the water, they flee either swimming, diving away or also in flight. They fly up more often than on land to take cover in the riparian vegetation. Immersion and, if necessary, swimming away underwater as camouflage behavior is mainly used against people who are airborne and people. They use aquatic plants as cover and dive so deep with their bodies that only their heads are above the water. If there is no covering vegetation, they submerge completely, whereby they cling to the ground or underwater plants and can remain there for up to two minutes. The ascent is slow.
Life expectancy
Based on the findings of ringed pond rails, we know that wild birds can live up to eight years. However, according to the ornithological inspection of Helgoland and Radolfzell , only about every ninth bird is older than two years.
For adult birds there are two seasons when they are particularly endangered by predators. During the breeding season, when the animals are less alert due to courtship and territorial defense, they are often struck by predators. Their mortality is even greater during the winter months, when the vegetation offers them insufficient protection. Severe winters with long periods of frost also weaken the birds, so that local populations can collapse.
Inventory and inventory development
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There are only rough estimates for the size of the European breeding population, it is estimated at a minimum of 900,000 and a maximum of 1,700,000 pairs, of which up to 180,000 breed in Central Europe. The populations are stable in most countries; only in Germany, Croatia, Estonia and Latvia has a negative population trend been found in recent years. In the Lake Constance area between 1980/81 and 1990/91 the population decreased by 60% and in the greater Bonn area between 1975 and 1990 by 55%. Overall, however, the trend is mixed; While for some regions such as the Lahn-Dill district in Hesse , the island of Rügen and the district of Dithmarschen it is reported that an increasing number of breeding sites that have been occupied for many years are no longer populated, in other regions the breeding population remained constant. Larger short-term fluctuations in stocks in Central and Western Europe are primarily due to high losses in severe winters. Long-term declines, however, are primarily due to habitat loss, disruption from various leisure activities and increasing competitive pressure from blow ramps .
literature
- Einhard Bezzel: FSVO manual birds. BLV Verlagsgesellschaft, Munich 1996, ISBN 3-405-14736-0 .
- Helmut Engler: The pond claw. Westarp Sciences, Hohenwarsleben 2000, ISBN 3-89432-347-7 .
- Franz Müller: Wildlife information for the hunter. Volume 2: Game birds. Verlag Norbert Kessel, Remagen 2006, ISBN 3-935638-60-4 .
Web links
- Gallinula chloropus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
- Videos, photos and sound recordings of Gallinula chloropus in the Internet Bird Collection
- Age and gender characteristics (PDF; 5.7 MB) by J. Blasco-Zumeta and G.-M. Heinze (eng.)
- Feathers of the pond claw
Individual evidence
- ^ List of species of birds in Germany. (pdf) DO-G , accessed on January 2, 2020 .
