Lesser black-backed gull
|Lesser black-backed gull|
Lesser black-backed gull ( Larus fuscus )
|Linnaeus , 1758|
The black-backed gull ( Larus fuscus ) is a species of bird within the gulls (Larinae). Their brood distribution extends from Iceland eastward over large parts of the European coasts to the Taimyr Peninsula in northwestern Siberia . The species is darker on top than the herring gull , to which it is not related as closely as previously assumed. It is more closely related to the steppe gull . Some authors consider the northeastern populations to be a separate species - the tundra gull ( Larus heuglini ). The nominate form occurring in northern and eastern Scandinavia is the darkest and possibly threatened in existence.
The black-backed gull is a migratory bird whose northern populations migrate furthest and sometimes overwinter in the tropical zones of Africa and Asia. Most of the birds from Western Europe already overwinter on the French Atlantic coast and in the Mediterranean.
The herring gull is 49–57 cm in length, smaller and slimmer than a herring gull . The beak is longer, narrower and looks more pointed. It is between 40 and 58 mm long. The wings appear relatively long in flight and relatively narrow, especially in the area of the arm wing. The wing length is between 368 and 456 mm, the wingspan between 118 and 158 cm, the weight between 450 and 1300 g. A sexual dimorphism is not pronounced with regard to the plumage. However, males are larger and more powerfully built. Young herring gulls in Western Europe change to adult dress in the fourth winter (four-year-old gull); the eastern subspecies fuscus , heuglini , taimyrensis and barabensis are three-year-old gulls. In the following, therefore, the characteristics and clothes typical of the Western European subspecies graellsii and intermedius are described, for the other forms see section Internal Systematics .
In the brood plumage the head, chest, neck and belly as well as the underside of the wings, rump and tail are pure white. The color of the upper side is darker than that of the herring gull and, depending on the subspecies, varies between slate gray and velvety black-gray as with the herring gull . Due to the white tips of the wings, the wing shows a white trailing edge that extends continuously to the fifth hand wing. The outer hand wing is black, but in darker birds (see geographic variation ) it usually only contrasts slightly with the rest of the upper side of the wing. Relatively small, white pointy spots and a subterminal field on the outer, tenth and sometimes a smaller one on the ninth hand swing stand out from this. The iris is yellow, the eye is surrounded by a red orbital ring. The beak, like the legs and feet, is yellow and shows a bright red gony spot .
The adult winter dress differs only in the dark dashed lines on the head and neck, in which the face usually remains white. In some birds, however, the head remains completely pure white even in winter. In some, a black mark can be seen in the area of the front bill above the gonys spot.
Juvenile birds appear dark brownish overall. The bill and eyes are black, the feet flesh-colored. The upper side makes a scaly impression due to blackish feather centers and light hems; the rest of the body plumage is dotted with dark brown spots on a light background. On the face, these dotted lines condense into a dark mask. The rump has dark brown banding on a whitish background, which merges into a wide, black tail band. The youth dress is similar to that of the herring gull, but is darker overall and especially in the area of the wings. The wings are blackish, as are the large and middle arm covers. The latter form two narrow, light-colored transverse bands on the upper side of the wing due to the light hems. The bright field in the area of the inner hand wings, which is typical of herring gulls, is mostly missing or less noticeable. The underside of the wing often looks very dark.
Birds in the first winter still show a black beak. The back and shoulder plumage is renewed from October and then contrasts with the worn wing plumage. The new feathers are greyish-brownish with darker markings and narrow, light hems, so that the upper side appears more uniform overall. The head, underside and rump are usually lighter than those of youthful clothes.
In the second winter, the coat, shoulder feathers, middle arm covers and the inner umbrella feathers are already slate gray, while the small and large arm covers are still brownish. The head and underside have lightened further, but still have extensive, dark dashes. The rump is now largely white and contrasts clearly with the tail band that is still present. The beak brightens from the base and at the tip.
Birds in their third winter are already very similar to adult birds, but the beak is not yet fully colored and shows a blackish band in the area of the rear gony . The dotted lines on the head are much stronger. In the area of the gray hand covers of adult birds, there are dark brownish feathers and the legs are still flesh-colored.
The breeding distribution of the black-backed gull is western Palearctic and extends over the coasts of the temperate and subpolar zones in Europe, northern Russia and western Siberia. It includes Iceland, the Faroe Islands and the British Isles . To the south it extends to the north of the Iberian Peninsula . There is a disjoint subpopulation in the Ebro Delta and isolated breeding pairs in Portugal . Eastward the distribution extends to the Taimyr peninsula. Individual breeding records are also available from Senegambia , where the species is otherwise only a winter visitor.
The black-backed gull is a migratory bird in which some of the northern populations migrate over the more southern ones ( skipping migration ), sometimes covering distances of up to 7500 km.
The winter quarters of the western European birds extend from northwestern France over the Iberian peninsula into the western Mediterranean area, where the species occurs scattered to Sardinia and to the Apennine peninsula, as well as on the west African coast to Nigeria . There the black-backed gull can also be found in smaller numbers along Niger and Benue far inland. While Iceland and the Faroe Islands are completely cleared in winter, more and more birds remain further south in the breeding area. Since the first wanderers were discovered on the North American Atlantic coast in the 1930s, the number of observations there rose sharply in the second half of the 20th century, so that the species is now a rare but regular winter visitor there. As a stray visitor, she even reached the North American west coast. The migration of western birds begins at the end of June, but sometimes continues until November or December. The first returnees arrive at the breeding grounds in February, but the majority only in April.
The birds of the Baltic Sea area ( L. f. Fuscus ) move away in a south-easterly direction. They can then be found on the train and in smaller numbers as winterers in the eastern Mediterranean, in the area of the Arabian Peninsula and in the Horn of Africa . The main wintering areas are, however, further south on the lakes and rivers of East Africa southwards to Botswana , Zimbabwe and Mozambique . Individual birds have also been found in other parts of Africa. Smaller numbers go to the Black and Caspian Seas ; some try to hibernate in the breeding areas, but then move to the southwest when the Baltic Sea freezes, where they reach the North Sea. The migration begins between July and August and reaches its peak in September. They move home between February and the end of June.
The birds of northern and central Russia ( L. f. Heuglini / taimyrensis and L. f. Barabensis ) overwinter mainly on the coasts in the Middle East between the eastern Mediterranean and the west of the Indian subcontinent , the southern edge of the Caspian Sea and the coast of the Horn of Africa. Birds of the questionable subspecies taimyrensis may also winter in East Asia between Japan and Taiwan . The move takes place relatively late from September with the high points in October. The birds return to the breeding areas around May.
The system of the so-called argentatus fuscus form circle , which includes the herring gull as well as the herring gull, is very complex. Due to genetic studies at the beginning of the millennium, however, some light could be shed into the family relationships. The earlier thesis that the white-headed great gulls are a ring species , the chain of shapes of which extends around the North Pole and both ends of which form the herring and herring gull, could at least be partially refuted. There were probably two refuges, from which on the one hand the herring gull and the related species of the black-headed gull , Mediterranean gull and Armenian gull developed, and on the other hand the steppe gull and the black-backed gull and eastwards afterwards Eastern Siberian gull ( Larus vegae ), Kamchatka gull and American herring gull .
The internal systematics of the black-backed gull is partly unclear. Depending on the opinion, between two and six subspecies are recognized. In addition to three European subspecies, based on recent genetic studies, three eastern forms - the tundra gull ( heuglini and taimyrensis ) , which is often regarded as a separate species, and the taxon barabensis , which used to be mostly part of the steppe gull - are assigned to this species. The independent status of the intermedius and taimyrensis forms is particularly controversial . The former is often placed too graellsi , the existence of the latter as an independent taxon is questioned. According to some authors, they could be hybrids between heuglini and the subspecies L. v. birulai the eastern Siberian gull act.
- L. f. fuscus Linnaeus , 1758 - Sweden and north coast of Norway eastwards to the White Sea (only a few there), probably no more occurrences on the Kola peninsula.
- L. f. graellsii Brehm , 1857 - Iberian Peninsula, France, British Isles, Iceland and Faroe Islands.
- L. f. intermedius Schiøler , 1922 - Netherlands to Denmark, southwestern Norway and an isolated population in the area of the Ebro Delta .
- L. f. heuglini Bree , 1876 - from the Kola peninsula eastwards via Novaya Zemlya to the Gydan peninsula , possibly broods already in Finland.
- L. f. taimyrensis Buturlin , 1911 - Taimyr Peninsula east of the Ob .
- L. f. barabensis Johansen , 1960 - Baraba- and Kulunda steppes in the south-western Siberia, to the southeastern Urals.
Geographically varying features
The geographical variation with regard to the coat color is quite pronounced. While birds from Iceland, the Faroe Islands and the British Isles are the lightest ( graellsii ), the darkest ones on the upper side are found in the Baltic Sea region and northeast Scandinavia ( fuscus ). Southeast Scandinavian birds occupy a middle position and are quite constant in color. On the other hand, birds with relatively light backs occur from southwest Denmark westwards. In the Netherlands the variation is very large, here almost all gradations occur, but a relatively dark graellsii type predominates . The populations of northern Russia east of the Kola peninsula and north-western Siberia correspond overall to Lf graellsii , but there is also a clinical (gradual) variation from dark birds in the west to light birds in the east, which mediate to Larus vegae . The form barabensis is close to heuglini in the back coloration .
There are other, less pronounced variations in the dimensions, especially in the beak dimensions and weight. Quite high beaks are found in Iceland, the lowest in Northern Norway. Noticeably long in southwest Sweden. In terms of weight, the nominate form is characterized by the lowest average weight, and the two northeastern subspecies that breed in the tundra have the largest average weight.
L. f. fuscus ("Baltic herring gull")
The nominate form , which occurs on the coasts of the Baltic Sea and formerly inhabited parts of the Kola peninsula, is the smallest, darkest and most elegant subspecies. In contrast to others, it is very slender with a smaller, rounder head, finer beak and - due to the long hand wings - when sitting, it is particularly narrow towards the rear. In flight, the wings appear narrow, long and pointed with a relatively short hand wing. The legs are relatively short. The top is almost black in the adult dress and the contrast to the black wing tip is hardly noticeable. The white tips of the outer hand wings are relatively fine and sometimes hardly present when the plumage is worn; only the outermost hand swing shows a white subterminal field. In the plain dress, the head shows only slightly extended, fine dotted lines. The youth dress is very rich in contrast with a dark face mask and often with a lot of white on the upper tail covers. In the first simple dress, the dark top contrasts particularly with the lighter underside. From the first summer onwards, the black feathers of the adult dress penetrate the back. Young birds are colored in the third winter.
L. f. heuglini (tundra gull)
This northern Russian subspecies, which breeds very scattered in single breeding pairs or smaller colonies in the tundra, is larger than the other forms with a body length of 53–70 cm and a wingspan of 138–158 cm (including “ taimyrensis ”). In habit it resembles L. f. fuscus with slender shape, small head, fine bill and short tail; however, the individual variation is very large. The back coloration corresponds to the graellsii / intermedius type, from which it can hardly be distinguished in the field. The hand wing pattern resembles that of the nominate shape with a white subterminal field that is limited to the outermost hand wing and relatively small white tips on the rest. The subadult dresses also resemble the nominate form. A characteristic of this subspecies is that it does not moult into the plain plumage until very late, so it retains the breeding plumage until the beginning of winter.
L. f. barabensis
About this taxon, which was often assigned to the steppe gull, but apparently , according to studies of the mitochondrial DNA , more closely with L. f. heuglini , or L. f. taimyrensis is not well known. Even the distribution data are poor. The breeding area of this seagull, which breeds on steppe lakes in southwestern Siberia, is presumably isolated, but could possibly approach that of the "tundra gull" in the north. A clear determination is not always possible. L. f. barabensis is relatively small and easily built. The color of the top is reminiscent of taimyrensis . In the adult dress it is noticeable that the beak appears four-colored with a red gony spot, a black mark on the upper beak and a whitish beak tip. In this regard, and in terms of the pattern of the hand wing, the taxon is similar to the Armenian gull. The subadult dresses are reminiscent of those of the steppe gull, but the adult dress is already put on in the third winter.
The lesser black-backed gull breeds mainly on the coast, but is found as a breeding bird, especially on the British Isles, in Scandinavia and in the eastern part of its range, in large areas on inland waters and in moors. It breeds in similar places as the herring gull, with which it also socializes, but in contrast to this it prefers flatter terrain with higher vegetation such as heather or bracken . It is only rarely found as a breeding bird on rocky cliffs, here it seems to avoid the presence of the herring gull in particular.
In the British Isles and West Scandinavia, the species is often a breeding bird in overlying bogs , where it nests in heather and cotton grass stands. On Iceland they can also be found in raised bogs and heaths, but also on gravel and lava areas with little vegetation. The subspecies L. f. fuscus breeds on flat islands or skerries near the coast or in inland waters. However, it prefers remote islands and places rich in vegetation; so it also breeds on islands with sparse pine trees.
The tundra gull ( L. f. Heuglinii and L. f. Taymirensis ) breed in open tundra landscapes with swamps and on coastal islands. It also seems to nest more frequently on steep rocky coasts. The subspecies L. f. barabensis colonizes extensive reed stands on steppe lakes and small islands with birch trees.
Outside the breeding season, the black-backed gull can be found on coastal and inland waters, in estuary landscapes , in ports and on tropical lagoons . In contrast to the herring gull, it is less tied to the littoral and more often found in the pelagic . It usually occurs only in small numbers as a kleptoparasite on landfills . It only occurs there in larger numbers when other large gulls are missing. Resting and sleeping places are often on large, well-arranged inland lakes or on the sandy beaches of Wadden islands.
The food spectrum of the black-backed gull consists of small fish such as the Atlantic herring , marine invertebrates such as swimming crabs, nestlings and eggs of birds, carrion, fishing waste, small rodents, earthworms, insects and berries.
As a result of increased food competition with other species such as the herring gull since the 1960s, the proportion of marine animals in the diet has increased significantly. Since the lesser black-backed gull often looks for food in the open sea, fish waste from cutters is of particular importance to them. For example, a moratorium on driftnet fishing in the western Mediterranean issued by the UN in 1991 meant that the species had to switch to other food sources and was now increasingly found in landfills, in olive groves and on rice fields. This had a direct impact on the breeding success.
In contrast to the herring gull and the Mediterranean seagull, the lesser black-backed gull is a more agile flier, which covers longer distances faster with its narrower wings. Fish are often captured at sea diving shock from the search flight from 10-12 m in height out, wherein the bird in a 45 ° angle about 8 down flies m, shaking decelerates down abuts and completely submerged. At landfills, the species tends to steal food from other seagulls rather than looking for it itself. In the nominate form, however, it can be observed that it avoids other seagulls and searches for food in deeper waters. In the intertidal zone, the black-backed gull is more likely to pick up visible food than to look for it in the seaweed or under stones.
Herring gulls usually breed in colonies and are occasionally associated with the herring gull. She reaches sexual maturity at the earliest at the age of three. She leads a monogamous seasonal marriage, whereby it comes to re-breeding due to the loyalty to the breeding site. The nest is usually built on the ground, but also on buildings and is laid out with plant parts from the area and seaweed. Laying begins at the end of April with a peak in May. The clutch consists of two to three eggs, which are laid about two days apart. The incubation period is 26 to 31 days. Both parent birds are involved in the brood. The young birds are able to fly at around 35 to 40 days. The average breeding success varies between 0.75 and 1.5 fledgling young birds per breeding pair and year.
The total European population is estimated at 300,000 to 350,000 breeding pairs at the beginning of the 21st century. In Great Britain there are about 114,000 breeding pairs, Norway has between 30,000 and 40,000 breeding pairs and in Iceland between 23,000 and 35,000 breeding pairs breed. The brood population in Central Europe is between 83,000 and 103,000 pairs. The Netherlands has around 58,500 to 72,000 breeding pairs and Germany between 23,000 and 29,000 breeding pairs.
As with a number of other seagull species, there have been significant increases in populations and area expansions in Central Europe, for example, since the 1920s. The reason for this is increased protection against disturbances at the breeding site, reduced egg collection, less hunting and improved feeding conditions in the breeding and wintering areas.
- Klaus Malling Olsen, Hans Larsson: Gulls of Europe, Asia and North America , Helm Identification Guides, Christopher Helm, London 2003 (corrected new edition from 2004), ISBN 978-0-7136-7087-5
- JM Collinson, DT Parkin, AG Knox, G. Sangster, L. Svensson: Species boundaries in the Herring and Lesser Black-backed Gull complex . British Birds 101 (7), 2008, pp. 340-363.
- Urs N. Glutz von Blotzheim , KM Bauer : Handbook of the birds of Central Europe . Volume 8 / I: Charadriiformes. 3rd part: snipe, gull and alken birds. AULA-Verlag, ISBN 3-923527-00-4 .
- Josep del Hoyo , Andrew Elliott, Jordi Sargatal (eds.): Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions 1996, ISBN 978-84-87334-20-7 , p. 611.
- 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 .
- Larus fuscus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 9 of 2009.
- Videos, photos and sound recordings of Larus fuscus in the Internet Bird Collection
- Lesser black-backed gull feathers
- Lesser black-backed gull catches and eats pigeons , Hyde Park and Kensington Gardens, London (Youtube video)
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- Eiler T. Lehn Schiøler: Nogle Tilføjelser og Bemærkninger til Listen over Danmarks Fugle . In: Dansk Ornithologisk Forenings tidsskrift . Volume 16, No. 1/2 , ISSN 0011-6394 , p. 1-55 .
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- Daniel Oro: Effects of trawler discard availability on egg laying and breeding success in the lesser black-backed gull Larus fuscus in the western Mediterranean , Marine Ecology Progress Series, Vol. 312, 1996, pp. 43-46
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- Bauer et al., P. 614