Oystercatcher
| Oystercatcher | ||||||||
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Oystercatcher ( Haematopus ostralegus ) |
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| Scientific name | ||||||||
| Haematopus ostralegus | ||||||||
| Linnaeus , 1758 |
The oystercatcher ( Haematopus ostralegus ) is a species of bird from the order of the waders, gulls and alken birds ( Charadriiformes ) and the genus of the oystercatchers . It is considered one of the most characteristic birds on the North Sea coast .
It has its greatest distribution in Europe in the Wadden Sea and the coastal interior of the North Sea, where it also bears the joking name of Halligstorch .
Due to its black and white plumage, the oystercatcher is associated with the magpie in many languages , e.g. in Finnish as Meriharakka (sea magpie), in Danish as Strandskade (beach magpie), in Dutch as Scholekster (plaice magpie) or in Russian as Кулик-сорока ( Kulik-soroka , Schnepfen-Magpie).
Appearance
Adult oystercatchers reach a body length of 40 to 45 centimeters and are thus roughly the size of crows . In the brood plumage both the head and the chest, the top of the body and the end band of the tail are plumed black. In the resting dress the black is a little duller and a white throat band can be seen on the sides of the neck. The long, orange-red, slightly flattened beak and the black and white body plumage contribute to the unmistakable appearance of the oystercatcher . The legs, feet and eyes are also red.
Sex dimorphism is only slightly pronounced; on average, the female's beak is slightly longer than that of the male. Overall, the beak length is the best feature for gender differentiation. The body plumage of the young birds is reminiscent of the resting dress. However, the feather hems on the upper side of the body are pale washed out. Their legs are also of a dull gray color and they occasionally show whitish spots on the throat and sides of the neck.
In flight, the oystercatcher, in addition to the white rear back, is characterized by the wide white wing shields and the wide black end border on the tail.
voice
Oystercatchers are very vocal birds. The loud and shrill quiéwiehp is the typical contact call for them. At the hatchery they also let out a shrill qui qui qui qui . This occasionally escalates into a noisy, high-pitched trill that swells up and down. It is also known as the whistle or trill ceremony and occurs particularly often when neighbors or oystercatchers without territorial waters get too close to the limits of the breeding area. One or both breeding birds approach the invading bird with lowered and slightly opened beaks, trilling and whistling in high tones and appearing very excited.
Distribution areas
Breeding areas
Oystercatchers have a large and disjoint breeding area, within which three subspecies are distinguished. The nominate form Haematopus ostralegus ostralegus breeds on almost all European coasts from Iceland and the Arctic coast to the coasts of the Mediterranean , with a focus of distribution on the coasts of the North Atlantic and the North Sea . Inland, this subspecies also breeds in parts of Scotland and Ireland, as well as in Sweden , the Netherlands , Russia and Turkey . While the Baltic Sea population is small, in Central Europe the main focus of distribution is on the North Sea coast and inland near the coast. From there, the birds penetrate deep into the inland, especially along the larger river valleys of the Rhine , Ems , Weser and Elbe , and also breed there. As soon as they are fully fledged, young birds seek out the coast.
The subspecies Haematopus ostralegus longipes breeds in Asia Minor , Western Siberia and in southern central Russia. The subspecies Haematopus ostralegus osculans , on the other hand, is a breeding bird in Kamchatka , China and on the west coast of the Korean Peninsula . Among other things, they were breeding birds in the Saemangeum Wadden Sea , which lies on the South Korean west coast at the mouth of the Dongjin and Mangyung rivers and, at 400 square kilometers, is one of the largest mud flats on earth.
Wintering areas
Oystercatchers are predominantly migratory birds . However, some of the Western European birds remain in their breeding areas or show only slightly pronounced migratory movements. The large flocks that can be seen in the south-west of England during winter are breeding birds in northern England or in Scotland . The breeding birds of southern England, like those of the Wadden Sea, overwinter in the coastal regions that lie between their breeding area and the Iberian Peninsula . To a very small extent, however, they also move as far as Morocco . The populations that live on the coast of Tunisia and Libya in the winter months have their breeding areas in the northwestern Mediterranean and the Adriatic .
Small parts of the Icelandic breeding population remain on the coast of Iceland during the winter. The rest of the Icelandic breeding populations overwinter on the coast of the Irish Sea , where the oystercatchers who breed in the Faroe Islands also gather. Both the Norwegian breeding populations and the birds that breed in the Baltic States and Russia overwinter in the North Sea's Wadden Sea .
The populations that overwinter in East Africa , Arabia and western India belong to the longipes subspecies . The subspecies onculans winters in southern China. The southernmost winter occurrences of the oystercatcher are on the West African coast in Ghana . It is not yet known in which regions these birds breed.
The birds begin their migration to the winter quarters after the end of the breeding season. The European breeding populations start migrating from mid-July. These intensify in August and September. The return to the breeding grounds begins at the end of January and continues until April. The return ends later for the birds that breed in Central Asia. The birds follow the coastline on their migration and can only be found inland in exceptional cases.
habitat
The oystercatcher is a foodborne strong attachment to the under tidal influence standing coast . It therefore prefers flat sea coasts and islands, estuaries of streams and rivers. The coastal areas used during the breeding season must have a substrate that allows the nesting trough to be scratched. Among other things, it breeds on rocky, pebble and sandy beaches as well as in primary and secondary dunes. In the Netherlands , in northwest Germany and partly in Great Britain , it can also be found in fields and short-grass meadows during the breeding season, in the inland it is found almost exclusively on wet pastures. Here it prefers to breed on lakes or broad rivers with gravel banks. He colonized the river valleys of the Elbe, Oder, Rhine and Ems, among others. Dredging lakes in gravel pits also fit into his habitat scheme.
Food and food procurement
On the coast, oystercatchers feed primarily on mussels , bristle worms , crabs and insects . The mussel species that make up a large part of its diet include mainly heart , mussel and Baltic flat mussels . They also eat limpets , beach snails and whelks . In the inland , the earthworm is the main food of the oyster fisherman, who is actively captured by worm grunts . In contrast to many coastal birds, the gizzard of the oystercatcher is poorly developed. Due to the technique used to open the food, these birds do not need to crush the shellfish in the gizzard.
During the day, the oystercatcher orientates himself visually when acquiring food. Cockles that are deeper in the silt are probably not detected by the sense of touch , but by slight differences in the structure and color of the soil. These Limikolen orientate themselves by touch, especially at night, and plow through the ground with their beak. With their sense of touch, they can very well distinguish between live mussels and empty shells.
An oystercatcher can swallow small mussels completely. With cockles this is possible up to a diameter of eight millimeters, with mussels up to 12 millimeters.
With larger mussels, the shell is opened to access the meat. Two different techniques are used for this. When the bird pounds open the mussel, tightly closed mussels are first placed on a solid surface that is sometimes several meters away and visited several times in a row and placed there with the flat side up. Then with firmly anchored feet, stiff neck, beak held vertically and closed and rocking in the hip joint, hammering on the mussel until a piece of shell breaks out. The rear sphincter muscle of the mollusk is severed with the hammering. Now the mussel can be pushed open in the shell by turning it a quarter turn and opening the beak slightly. Opening and emptying a mussel rarely takes more than 10 to 15 seconds. Hard shells are occasionally dropped from a height of several meters onto a hard surface in order to open them. The second technique used is to push the beak between the shell halves to injure the sphincter muscle.
With both techniques, the clam meat is systematically chiseled out and shaken free as soon as the clam is open. A single bird only ever uses one of the two techniques. It is learned from the parent birds and perfected through practice. The use of the respective technique leads to different shapes of the beak tip, the tip of the beak is rather blunt in the followers of the first technique, in the followers of the second technique the beak tip is more pointed. With a little practice this can also be seen in the field.
behavior
On the coast, the activity of oystercatchers is extremely tide-dependent - the animals are therefore diurnal and nocturnal. Without the influence of the tides, they are diurnal inland.
Oystercatchers swim well and quite often. Groups of several animals have already been observed from far away from the mainland. The birds probably rest on the water during high tide on dark nights. Injured or not yet able to fly young birds flee from enemies on the water and also dive in the process, whereby they only move underwater by flapping their wings. At a diving depth of 30 to 50 centimeters, the animals can cover distances of up to 15 meters under water.
Outside the breeding season , oystercatchers are very sociable. At the breeding site, however, they can show extremely aggressive behavior. This can go so far that native or alien limicoles are shaken or chopped to death by the breeding bird.
Like a number of other ground-nesting bird also, the oystercatcher trying the nest approaching ground enemies by enticing lure. If a possible predator does not come too surprisingly close to the nest, the breeding bird steals away from it as inconspicuously as possible and taking advantage of the cover in order to distract the predator from the nest by pseudo-breeding or by simulating injuries. If grazing animals such as sheep or cows come too close to the nest, the oystercatcher defends his nest or brood by chopping against these animals.
Reproduction
Most oystercatchers breed for the first time in their fourth year of life and can still be sexually active even as young as 36 years of age. Oystercatchers are mostly monogamous , but bigyny does occur. The loyalty to the spouse is very pronounced - there are only very few separations during the lifetime of both partners. However, if one partner dies, the other mate within a few days.
As a nest location, this ground-breeder often chooses slightly elevated sandy beaches outside the mean tidal high water . Inland, fallow and cultivated fields are preferred. More important than the nature of the nest location, however, is that of the food biotope. The birds sometimes breed in sand pits, on construction sites, in the gravel bed of railway lines, on gravel flat roofs, on thatched roofs or in wicker. The nest is just a shallow hollow without a large lining, which is turned with the body into the soft ground.
The female usually lays three eggs; larger clutches are only created by "laying together" two or more females. The oyster fishermen also have so-called mixed spots with other alien waders, terns and gulls, which are also alternately incubated by the two different species. As with all Limikolen, there is only one annual brood. However, if the first brood is destroyed by grazing cattle or by seagulls, there are usually smaller laggards. The incubation period is 26 to 27 days; Males and females breed in equal parts. The young animals are fed by the adult birds.
Bigynistic breeding behavior
Bigynistic breeding groups were observed in a Dutch study. The ratio of monogamous couples to such bigynistic groups is about 1,000 to 25. The bigynistic groups consist of one male and two females. It is noticeable that there are both aggressive breeding groups in which the females compete with one another and those in which they work together. In the aggressive groups, one female defends its own nest and the male defends a small area that includes the nests of the two females. In the cooperating groups, the two females lay their eggs in a nest that is defended by all three birds.
About sixty percent of the breeding groups show aggressive behavior. Their breeding success is not very high and is below that of monogamous couples. This is due to the fact that aggressive actions between the two females occur approximately every two minutes during brood and neither of the two nests is sufficiently incubated. The breeding success is higher in the cooperative groups. The slightly more dominant female mates with the male every three hours, the slightly inferior female about every five hours. At the same time there is mating behavior between the two females. In spite of the cooperative behavior, however, the breeding success with them is less than with monogamous pairs. Their body size is not sufficient to incubate more than four eggs, so that three to four eggs of the common clutch are not hatched. The reason for this behavior is still controversial. One possible cause is that the available breeding places are insufficient. Females that were members of such a breeding group have a higher chance of entering into a monogamous partnership next year compared to unmated females.
Development of the young birds
The development of the young is faster in inland breeding birds than in those which are hatched in coastal regions. The young birds, which did not hatch on the coast, but in the fields inland, break away from the adult birds up to six weeks earlier because they learn more quickly to eat their own food. This is certainly primarily due to the different food spectrum. The main food of the young oystercatchers on the coast are mussels, snails and crabs, which have to be "cracked" before they can be consumed by the animal, for which a fully developed and hardened beak is required. The young birds in the interior have it much easier. Your main food, the earthworm, can be devoured without any effort.
Breeding Success, Mortality, and Age
One month after fledging, 16 percent of the hatched young are still alive. The average age of oystercatchers is 14 to 15 years. Oystercatchers can live to be over 30 years old in captivity. The record so far is held by an animal that was found dead in 1993. Its ringing from 1949 in the Netherlands shows a proud age of 44 years.
Stock size and stock development
The oystercatcher is the only representative of the oystercatcher genus to live in the western Palearctic today . The endemic Canary Island oystercatcher ( Haematopus meadewaldoi ), which used to breed on the eastern Canary Islands La Graciosa , Lanzarote and Fuerteventura , was last reliably detected in the 1940s and has been considered extinct since 1968 .
From the middle of the 19th century, oystercatchers suffered significant populations due to persecution and disturbances at the breeding grounds. The population of these birds has slowly recovered since around 1920 after initial protective measures were initiated. Since the 1930s there has been settlement along the river plains. Among other things, the expansion of grassland management, a decrease in the gathering of oyster fishermen, a decrease in hunting, an increase in prey due to eutrophication and a settlement of agricultural areas have contributed to an increase in the population. In part, this has led to an exponential increase in stocks. In 1955 there were between 8,000 and 12,000 breeding pairs in the Netherlands. At the beginning of the 21st century the breeding population had risen to between 80,000 and 130,000 breeding pairs. One potential source of danger is that 72 percent of the nominate form oystercatchers overwinter in only thirteen areas.
The IUCN estimates the total population of the oyster fisherman at 1.1–1.2 million animals and classifies the species as not endangered ( least concern ). In Central Europe , the current fluctuations in stocks are primarily due to persecution, disturbances and habitat changes, on the one hand, and intensive protective measures and dikes, which benefit the oystercatcher, on the other. The trigger for the inland settlement was probably the modernization and intensification of agriculture. Since the mid-2000s, the population in the counties of Grafschaft Bentheim and Emsland, where previously a strong inland population was observed, has declined significantly, with the drastic decline in green areas and the much more intensive management of the remaining grassland areas, combined with increased predator pressure and disturbances the breeding business by walkers, dogs and riders, which are likely to be the main causes. Because of the decline in suitable, undisturbed breeding areas, here, as elsewhere in Lower Saxony, an increase in oyster fish broods on flat roofs can be observed even in cities.
The European countries in which more than 20,000 breeding pairs occur include the Netherlands, Germany, Norway and Great Britain. At the beginning of the 21st century, between 112,000 and 168,000 breeding pairs were breeding in Central Europe. The winter population in Europe is between 900,000 and 1,100,000 individuals. However, oystercatchers are considered to be one of the species that are particularly affected by the effects of global warming. A research team that, on behalf of the British environmental authority and the RSPB, examined the future development of the distribution of European breeding birds on the basis of climate models, assumes that oystercatchers will largely extinguish their breeding populations in Western and Central Europe by the end of the 21st century will come. Svalbard and Novaya Zemlya will then come into question as distribution areas for oystercatchers, but this area expansion in the north cannot compensate for the predicted loss of area in the south.
National bird of the Faroe Islands
In the North Atlantic Faroe Islands , the oystercatcher is the national bird under the local name Tjaldur ([ ˈʧaldʊɹ ]), whose annual return from winter quarters is celebrated by the Faroese on March 12th , the day of the Grækarismessa , as the beginning of spring .
In the song Fuglakvæði , the Faroese national hero Nólsoyar Páll sang this bird in the 19th century, which has since been the symbol of the Faroese striving for independence. He owes this status to his behavior in warning all other animals in case of danger.
The oystercatcher is under strict nature protection in the Faroe Islands. Tens of thousands of pairs breed there. Some specimens also hibernate in the Faroe Islands, but most of them migrate south.
The Faroese language also has a word for the sound that the oystercatcher utters : klipp klipp!
Trivia
Because of their similar appearance, the oystercatcher is also popularly known as the Friesian stork . It is also the logo of the Sea Birds and Nature Conservation Association Jordsand .
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 .
- Peter Colston , P. Burton: Limicolen - All European wader species, identifiers, flight images, biology, distribution. BLV, Munich 1988, ISBN 3-405-13647-4 .
- Simon Delany, Derek Scott, Tim Dodman, David Stroud (Eds.): An Atlas of Wader Populations in Africa and Western Eurasia. Wetlands International , Wageningen 2009, ISBN 978-90-5882-047-1
- Urs N. Glutz von Blotzheim (Hrsg.): Handbook of the birds of Central Europe. Edited by Kurt M. Bauer and Urs N. Glutz von Blotzheim, among others. Vol. 6: Charadriiformes . Part 1. Aula, Wiesbaden ³1999, ISBN 3-89104-635-9 .
- E. Bezzel: birds . BLV, Munich 1996, ISBN 3-405-14736-0
- Helmut Lensing, The oystercatcher (Haematopus ostralegus ostralegus) in the county of Bentheim and the Emsland, in: Study Society for Emsländische Regionalgeschichte (Ed.), Emsländische Geschichte, Vol. 23, Haselünne 2016, pp. 32–57.
Web links
- The oystercatcher at the Wattenmeer eV protection station
- More photos and information in the nature dictionary
- Live webcam at the nest of an oystercatcher in Norway
- Videos, photos and sound recordings of Haematopus ostralegus in the Internet Bird Collection
- Haematopus ostralegus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 20 of 2008.
- Oyster fisherman's feathers
Individual evidence
- ↑ 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. 542
- ↑ 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. 543
- ^ 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. 134
- ^ 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. 135
- ^ 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. 135
- ↑ Bauer et al., P. 418
- ↑ Bauer et al., P. 418
- ↑ Delany et al., P. 49
- ↑ Bauer et al., P. 417
- ^ 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. 164
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