Black-headed gull
| Black-headed gull | ||||||||||||
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Black-headed gull in summer dress |
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| Chroicocephalus ridibundus | ||||||||||||
| ( Linnaeus , 1766) |
The black-headed gull ( Chroicocephalus ridibundus , Syn . : Larus ridibundus ) is a species of gull . This small species of seagull inhabits large parts of the northern Palearctic from Iceland and Ireland to Kamchatka . Black-headed gulls breed in the silting zones of larger bodies of water, especially inland, but for some time now also increasingly on coasts. The species is a frequent breeding bird in northern Central Europe and also spends the winter in large numbers in Central and Western Europe.
description
With a body length of 35–39 cm and a wingspan of 86–99 cm, this species is the smallest representative of the real seagulls that regularly breeds in Central Europe (regardless of the terns). Males are larger and heavier than females. In the example had Switzerland wintering males a wing length mm from an average of 319.1, females reaching an average of only 300.7 mm and winter birds in Zurich had a weight of an average of 324.2 g (males) g vs. 283.2 (females ).
In the magnificent dress that exists from around the beginning of March to July , the head is dark black-brown, the eyes are narrowly rimmed with white, although this edge is not closed in front. The back, the upper and lower wing-covers and the upper side of the arm and inner hand wings are light gray; the rest of the trunk and tail are white. The outer hand wings are predominantly white, they show a black end band and narrow black edges on the inside of the inner flag . Only the outermost hand wing has a narrow black border on the outer edge of the outer flag. This creates a wide white wedge on the upper side of the wing, which is bordered by dark; in flight, this feature can often be used to identify species from a great distance. The beak and legs are red. The iris is dark brown.
In the plain dress , only the eye region and the ear area are diffuse blackish in color, the red beak has a blackish tip.
In youth clothing , the head, coat, shoulder and umbrella feathers as well as the middle wing covers are brownish sand-colored. The tail is pure white at the base and shows a broad, sharply defined dark brown end band. The beak is pink to orange with a black tip; the legs are colored in the same way. At the age of two the birds are colored.
Vocalizations
The courtship calls most frequently uttered in the colonies both during the day and at night are rowed croaking like "rä grä grä-krää, kräähh". Outside the breeding season at feeding places a sharp, penetrating “kriiiärr” can be heard in many variations, as well as a short and sharp “kik”. It got its Latin name because its reputation is reminiscent of a mocking laugh. The German name comes from the literal translation from Latin.
distribution and habitat
The distribution area of the black-headed gull covers large parts of the northern Palearctic from Iceland and Ireland to Kamchatka . Single pairs breed irregularly on the Newfoundland coast . In Central Europe, the focus of the occurrence is in the coastal lowlands. The black-headed gull is the most common breeding bird in the Wadden Sea. It is represented on the German North Sea coast with more than 57,000 couples.
During the breeding season, the species populates silting zones of larger bodies of water, especially inland, but for some time also increasingly on coasts; mainly still waters, less often larger rivers with low flow speeds are inhabited. In winter, cheap food habitats of all kinds are sought out, including short-grass meadows, arable land, rubbish dumps, sewage treatment plants, ports and bodies of water in cities. In recent decades, the black-headed gull has also appeared in cities, increasingly far away from water, in squares, in pedestrian zones and in similar places.
Systematics
No subspecies are recognized for the black-headed gull.
nutrition
The food is taken from the low search flight over the water or the ground, in a shaking flight or in a dive, depending on the offer, but often also while walking. In addition, prey in shallow water or on muddy floors is scared off by trampling. Flying insects are also preyed on in the air; after all, black-headed gulls parasitize conspecifics and other birds by trying to steal chunks of food from them.
The food spectrum of the black-headed gull is accordingly very broad and includes both vegetable and animal components, with the latter usually predominating. The diet mainly includes earthworms , polystyrene , crustaceans , a wide variety of insects, small fish as well as grains and other plant seeds, regularly also small vertebrates, live or as carrion. They are regular ship followers in the shrimp fishery. They also follow tractors working on farmland, where they eat the earthworms exposed by the use of machines. In the winter months in particular, rubbish is disposed of in rubbish dumps and human food remains of all kinds, especially bread in cities. The nutritional requirement of an adult individual is about 142 grams per day. If black-headed gulls feed mainly on earthworms, they need a fresh weight of 165 to 220 grams.
Reproduction
Black-headed gulls are sexually mature at the age of two, but they usually only breed in the fourth calendar year. Black-headed gulls lead a monogamous seasonal marriage. Due to their loyalty to the breeding site, mating with the partner bird of the previous year is possible.
Black-headed gulls breed in colonies that usually contain 10–1000 pairs, but in which less than 10 and up to a maximum of 21,000 pairs can breed. The nests are mainly created by or floating on the water in dense, but not too high vegetation, but often also on unusual structures such as tree stumps, house roofs, rafts and the like. The nests are a minimum of 70–100 cm apart. The nest is occasionally just a hollow in the sand or peat delimited by a few blades of grass, but mostly a 20–50 cm wide structure made of coarse, approximately 30–50 cm long plant stalks from the area. It is mostly built by the male.
In Europe, eggs are laid mainly from mid to late April, only in southern and western Central Europe also in early April. The start of laying is usually highly synchronized within a colony, the majority of the eggs are laid within 14 days. The clutch usually consists of three eggs, rarely two and very rarely just one egg. Eggs from Upper Swabia measured an average of 52.0 mm × 36.7 mm, the dimensions from other areas of the distribution area are very similar. The eggs are very variably dark spotted and dashed on a predominantly brown to olive green background. Both partners incubate, the incubation period is 22 to 23 days.
The young birds are place stools, so they stay at the breeding site and can fledge after about 26–28 days. They are fed by both parent birds. At the begging sounds of the young birds, the parent birds usually choke food out onto the ground. Then the chunks are held up to the young birds with the beak. Slightly older young birds also pull food from their parent birds' throats. The fledglings are constantly huddled until they are seven days old, but then only at night. They are able to fly from their 26th to 28th day of life and are independent at around 35 days of age. The oldest ringed birds were 28, 30 and more than 32 years old.
hikes
The black-headed gull is, depending on the geographic location of the occurrence, a stationary bird or a line bird, partial migrant , short- distance or rarely long-distance migrant . The withdrawal from the breeding areas begins at the end of May with the non-breeders and unsuccessful breeding birds; From the end of June, successful breeding birds and juveniles also leave the colony and disperse to nutrient-rich places in the area. The actual move begins in August. The winter quarters are usually reached at the beginning of October, but the departure can extend into December.
Wintering takes place predominantly in the temperate to subtropical zone of the Palearctic, to a lesser extent further south; The southern limit of wintering is in the west of East Africa , further east of South India, the Malay Peninsula and Indonesia . In Europe, the main wintering area is limited to the north and east by the 0 ° C January isotherm ; between the 0 ° C and −2.5 ° C January isotherms, winter populations usually only persist in cities due to intensive feeding. The home migration in Central Europe begins in mid-February, the main migration takes place in early to mid-March.
Existence and endangerment
Inventory development
The black-headed gull suffered drastic populations in the course of the 19th century due to the loss of habitat in natural silting zones and running waters as well as direct persecution. The stocks only increased towards the end of the 19th century. There was a considerable increase in stocks throughout Europe and, in some cases, significant area expansions. For example, Iceland was populated by black-headed gulls from 1911 and Spain from 1960. At least in Germany, however, there was also a concentration of black-headed gull colonies on the remaining wetlands and coastal regions. The overall positive population trend continued into the 1970s and led, for example, to the fact that the breeding pair population in the Netherlands rose from 18,000 to 35,000 breeding pairs in 1925 to 200,000 breeding pairs in 1978. In Austria, where fewer than 200 pairs were breeding in 1935, there were between 6000 and 8000 pairs between 1975 and 1981. It is generally assumed that the Central European brood population doubled in the period 1960 to 1975 alone . The highest levels were reached in the 1970s and 1980s. Since then, very different population trends have been observed regionally. Overall, the population decreased by around 10% between 1990 and 2000. In Germany, the total decreased by more than 25 percent between 1988 and 1999. Individual colonies show very drastic declines. At Dümmer , a shallow lake in the north German lowlands, the population decreased from more than 5,000 breeding pairs in 1985 to fewer than 50 in 2004, and on Baltrum , where 9,000 breeding pairs were breeding in 1998, only 100 breeding pairs were counted in 2003.
In addition to habitat losses such as melioration or a targeted increase in the water level in wetlands as well as siltation, destruction of siltation zones and increased use of reed areas, the causes of local population declines are a large-scale decline in food, especially during the rearing time of the nestlings. This is mainly due to the intensification of agriculture. The reduction of open landfills and changes in the fishing industry also play a role in some regional trends.
Current inventory and inventory forecasts
BirdLife International gives the world population for 2002 with 7.3–11.0 million individuals and the population in Europe for around 1990–2003 with 1.5–2.2 million pairs. The largest populations in Europe have Russia with 200,000–500,000 pairs, Belarus with 180,000–220,000 pairs and Germany with 137,000–167,000 pairs (estimate for 1995–1999). Between 1998 and 2000, the Netherlands had 132,000–137,000 breeding pairs and Poland between 110,000 and 120,000 breeding pairs. The IUCN currently considers the species to be harmless (“ least concern ”) despite the slight decline in the population .
The black-headed gull is one of the species that could be particularly affected by possible climate change. A research team that, on behalf of the British Environmental Protection Agency and the Royal Society for the Protection of Birds, examined the future development of the distribution of European breeding birds on the basis of climate models assumes that the range of the black-headed gull will shrink considerably by the end of the 21st century. According to these forecasts, large parts of today's distribution area in Western Europe would no longer offer suitable habitats. The Central European distribution area could also become significantly more fragmented. According to these models, an expansion of the distribution area would only take place to a very small extent, even if Novaya Zemlya , the extreme north of Norway and Russia and parts of Svalbard come into question as a new distribution area of this species.
literature
- Hans-Günther Bauer, Einhard Bezzel , 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 .
- E. Bezzel: Compendium of the birds of Central Europe. Nonpasseriformes - non-singing birds . Aula, Wiesbaden, 1985, ISBN 3-89104-424-0 , pp. 526-531.
- Lars Svensson , PJ Grant, K. Mullarney, D. Zetterström: The new cosmos bird guide. Kosmos, Stuttgart 1999, ISBN 3-440-07720-9 , pp. 170-171.
Web links
- Larus ridibundus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed October 13 of 2008.
- Videos, photos and sound recordings of Larus ridibundus in the Internet Bird Collection
- Age and gender characteristics (PDF; 2 MB) by J. Blasco-Zumeta and G.-M. Heinze (Eng.)
- Black-headed gull feathers
Individual evidence
- ↑ Urs N. Glutz von Blotzheim, Kurt M. Bauer: Handbuch der Vögel Mitteleuropas , Volume 8 / I, Charadriiformes (3rd part) Schnepfen-, seagull and alkenvögel. Aula, Wiesbaden, 1999, ISBN 3-923527-00-4 , p. 278
- ^ Lars Svensson, Peter J. Grant, Killian Mullarney, Dan Zetterström: Der neue Kosmos Vogelführer . Kosmos, Stuttgart 1999, ISBN 3-440-07720-9 , p. 170.
- ↑ Linné, Systema naturae, 12th ed., Vol. 1, Stockholm, 1766, p. 225. Can be viewed at http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=PPN362053367&IDDOC= 219599 .
- ↑ Klaus Mörike: Interpretation and origin of the name of the black-headed gull . Journal for Ornithology, 112 (1971), pp. 317-322.
- ^ Künnemann, Gad: Salt meadows . Isensee Verlag 1997, ISBN 3-89598-414-0 , p. 122.
- ↑ a b Bauer et al., P. 587.
- ↑ Urs N. Glutz von Blotzheim, Kurt M. Bauer: Handbuch der Vögel Mitteleuropas , Volume 8 / I, Charadriiformes (3rd part) Schnepfen-, seagull and alkenvögel. Aula, Wiesbaden, 1999, ISBN 3-923527-00-4 , p. 321.
- ↑ Bauer et al., P. 588.
- ↑ a b c Bauer et al., P. 585.
- ↑ Larus ridibundus . In: BirdLife International 2004: Detailed species account from Birds in Europe: population estimates, trends and conservation status (pdf, engl.)
- ↑ Bauer et al., P. 586.
- ^ 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. 213.