Larus

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Larus
Black-headed gull (Larus marinus)

Black-headed gull ( Larus marinus )

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Laridae
Subfamily : Seagulls (larinae)
Genre : Larus
Scientific name
Larus
Linnaeus , 1758
Flying Japanese Gulls ( Larus crassirostris )
Flying Mediterranean seagull (
Larus michahellis ) from above
Lesser black-backed gull (
Larus fuscus ) in shaking flight
A typical collection of large gulls of the genus Larus in different age clothes, here Mediterranean gulls and black-backed gulls
Swimming great gulls
A young Dominican gull is wading for food

Larus is a genus of seagulls that, according to conventional belief, included a large part of all seagull species. After a taxonomic reorganization of the Laridae family and the breakdown of the genera Chroicocephalus , Ichthyaetus , Leucophaeus and Hydrocoloeus after 2005, the genus only contains about 24 medium-sized to very large species. Some of these are very similar. Although more recent research has been able to shed more light on the relationships, primarily through genetic studies, some questions about the internal systematics are still unanswered. Among other things, this affects the species status of some taxa .

Most species of the genus occur in the northern hemisphere. But it is also represented in the southern hemisphere with four species. Most species are common, and some are among the most populous seabirds in their range. Only the Olroggull and the black man gull are endangered or potentially endangered due to their spatially very limited breeding areas in the population.

description

Generic characteristics

The species of the genus Larus are medium-sized to very large, mostly strongly built and not very specialized gulls. The smallest species is the common gull with a body length of 38–45 cm and a wingspan of 100–130 cm , the largest with a body length of 61–78 cm and a wingspan of 145–165 cm the black-headed gull .

The beak of the Larus species is usually relatively strong to massive, high to very high, laterally flat with a bent tip and a clearly pronounced gonys angle . The edge of the beak (Gonys) is curved, the nostril is teardrop-shaped. In adult birds of most species the beak color is yellowish to bright yellow with black and / or red spots or bandages in the area of ​​the front bill. In juvenile plumage beak is dark in all types and brightens up later from the bottom up on flesh-colored.

In many species of adult birds, the eye shows a light, yellowish to whitish iris and a colored orbital ring . When young, the iris is dark in all species and, if typical of the species, does not light up until later.

The run is relatively long and strong, the birds of this genus appear relatively long-legged. The webbed feet are only slightly indented. The leg color of adult birds varies between yellow or greenish yellow, light flesh colors and reddish flesh colors up to black in the black man's gull. The legs and feet of sub-adult gulls are usually flesh-colored to grayish.

All species of the genus show a white head when brood, most a white underside and a white tail. Black caps are generally not found, but in the adult winter plumage the head plumage is more or less extensively streaked with dark feathers. Only in the case of the Simeons, Olrog and Heermann gulls is the head in winter dress brown-black up to the neck.

The coat, back and upper sides of the wings vary between whitish and light gray and dark slate gray to blackish. The trailing edge of the wing is white in most species, the wing tip more or less extensive black. In addition, white wing tips or subterminal fields on the outer wings often contrast . The pattern of the wing tip often offers a characteristic of the species. In the species of the northern polar regions, the black wing areas are lightened up to white in the polar gull .

Differentiation within the genus

The genus can be divided into several groups based on external characteristics. Most species - such as the herring gull and all closely related species (so-called "forms of argentatus-fuscus ") - show the characteristics described above, while others differ in several features.

Common gull and ring-billed gull are relatively small with a relatively fine beak, but otherwise very similar to the argentatus fuscus species.

Four types - black-tailed gull , Belcher's Gull , olrog's gull and Pacific Gull - also show in the adult dress a black Subterminalbinde on the tail feathers, a black hand wing with only very small, white top spots and very extensive red or red-black areas on the front beak.

The male gull differs significantly from all other species. In the adult dress it shows dark plumage on the top and bottom, a red beak with a black tip and black legs.

Identifying features

In addition to the color of the legs and back in the adult dress, important characteristics for determining the species are the size, proportions and the hand swing pattern. The physiognomy , in which the position of the eye to the head side, the expression of the crown and the length of the game before the eye play a role, can be consulted for species identification. For example, the black-headed gull - and especially the male - looks almost "brutal" with a relatively high-lying, relatively small eye and a plump cheek, the Mediterranean gull with a rounded head and a relatively large eye "friendlier", the steppe gull, on the other hand, is average quite flat parting.

The genders hardly differ externally. Males are on average larger with a stronger bill and a flatter crown. These differences are most noticeable in the larger species.

Way of life

The gulls of the genus Larus are predominantly coastal birds, but occur mainly in North America, Middle East and Central Asia as well as in Northern Europe also in large areas inland as breeding birds. Outside of the breeding season, they often roam far inland elsewhere. On the open sea they are almost only to be found in the wake of fishing trawlers or other ships and usually not too far from the coast. Many species prefer rocky coasts or islands as breeding grounds. In the absence of these, however, dunes, lagoons, marshland and estuary landscapes or the like are also accepted. Some species such as the steppe or California gull also breed in arid areas or on river systems. Some northern polar species are breeding birds on the tundra.

Systematics

External system

For a long time, the genus Larus comprised a large part of all seagull species and although some attempts at taxonomic reorganization of the Laridae had already been made, a division into several genera only found broader recognition after extensive genetic findings were available in 2005.

As early as 2000, studies of mitochondrial DNA had suggested that the existing definition of the genus was a polyphylum . It turned out that the black-headed gull and related species ("masked species") are not as closely related to the other forms of the genus as assumed. The latter include the herring gull relatives ("white headed species"), the group around the black-headed gulls ("black headed species") and some black-headed forms of the New World (e.g. Aztec gull , "hooded species"). Rather, the species around the black-headed gull are related at the other end of the group of gulls, while the species that had long been placed in their own genera (e.g. the kittiwake , the swallow gull or the ivory gull ) stand between the two groups which is shown in the cladogram as follows:


Chroicocephalus (including black-headed gull)


   

Saundersilarus (Cape Gull)


   

Hydrocoloeus (Little Gull and Rose Gull)


   

Creagrus (fork-tailed gull)


   

Pagophila (Ivory Gull )


   

Xema (swallow gull)



   

Rissa (including kittiwakes)


   


Larus (including herring gull)


   

Ichthyaethus (including black-headed gull)



   

Leucophaeus (including Aztec gull)



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Since not all species were taken into account in 2000, another, much more extensive study was carried out in 2005 with DNA samples from all 53 species of gulls recognized at the time. Although not all phylogenetic conditions could be clarified in it, several well-separated groups emerged. Although some of these had already been identified as subgenera in the 20th century , some surprising findings emerged about the exact composition of these groups. As a result, the authors of the study suggested that some of the genera established in the 19th century, which were only recognized as subgenus names, be taken up again and that the existing genus Larus be divided into the genera Chroicocephalus (e.g. black-headed gull), Ichthyaethus (e.g. . B. Pallas's Gull ), Hydrocoloeus ( Gull ) and Leucophaeus (z. B. dolphin gull ) break down, or only the "white-headed types" ( "white headed species") in the genus Larus to leave. Some institutions like the International Ornithological Congress , the American Ornithologists 'Union , the British Ornithologists' Union, and the South American Classification Committee have already followed suit.

Internal system

Within the group of the "white-headed" seagull species, the DNA findings showed that apparently some more or less homogeneous groups split off before the argentatus fuscus shape circle emerged, as can be seen in the following cladogram:

 "White-headed species" 
 Species with a dark tail band 

Simeon's gull ( Larus belcheri )


   

Olroggull ( Larus atlanticus )


   

Japanese gull ( Larus crassirostris )


   

Black-billed Gull ( Larus pacificus )


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 Species without a dark tail band 

Common gull ( Larus heermanni )


   

Common Gull ( Larus canus )


   

Ring- billed gull ( Larus delawarensis )


   

Western gull ( Larus occidentalis )


   

Yellow-legged gull ( Larus livens )


   

Kamchatka Gull ( Larus schistisagus )


   

Iceland Gull ( Larus glaucoides )


   

Thayer gull ( Larus thayeri )


   

Ice gull ( Larus hyperboreus )


   

American herring gull ( Larus smithsonianus )


   

California gull ( Larus californiacus )


   

Bering Gull ( Larus glaucescens )


   

Dominican gull ( Larus dominicanus )


   

Steppe gull ( Larus cachinnans )


   

Lesser black-backed gull ( Larus fuscus )


   

Armenian Gull ( Larus armenicus )


   

Black-headed gull ( Larus marinus )


   

Herring gull ( Larus argentatus )


   

Mediterranean seagull ( Larus michahellis )


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The first of the branching groups includes four species with a dark tail band, the distribution of which extends from Japan through Australia and South America. In addition to the dark tail band, they show a dark iris, a very extensive, simple spot in the area of ​​the front bill and little or no white markings on the predominantly black hand wing - that is, features that are only present in the other Larus species in juvenile dress and therefore were already considered "primitive" by some authors before the genetic findings. It is unclear whether these species are closely related. The genetic investigations assign them a phylogenetically quite original position within the genus, but do not necessarily indicate that they form a monophylum . Among these species, the Olroggull ( Larus atlanticus ) was long regarded as a subspecies of the Simeon's gull ( L. belcheri ) and was only described as a separate species in 1958.

The next branch contains only the strongly deviating one, since in the adult dress predominantly dark, black-legged and red-beaked Heermanni gulls ( L. heermanni ) from Baja California . Due to the similarity with the gray gull ( Leucophaeus modestus ), a close relationship was often assumed in the past, and a relationship with other dark and also subtropical species such as the white-eyed and hemprich gull was assumed. However, genetic findings suggest a convergent development .

The other branches include the relatively small species common and ring-billed gulls as well as the closely related species western and yellow-legged gulls, which are very similar to the other Larus species. All four species occur in North America, only the common gull is also distributed in the Holarctic . A split into an American ( L. brachyrhynchus ) and a Palearctic species has been proposed, but genetic studies to confirm this are not yet available.

argentatus fuscus shape circle

Since the first half of the 20th century, special scientific attention has been paid to the species around the herring gull and herring gull, which is composed of numerous, quite similar taxa that are predominantly circumpolar to the north and differ in the adult dress through different shades of gray in the back color and differ in the color of the legs. Before genetic findings revealed the complex relationships, there were numerous controversial views on the systematics, taxonomy and history of this group.

After Jonathan Dwight had made a first comprehensive attempt at a species classification in 1925, Boris Stegmann questioned these results in 1936 and summarized many of the species recognized by Dwight as Larus argentatus . He took the view that the various forms were subspecies that had spread out in a ring around the North Pole and mixed in their adjacent distribution areas partly at the edges. According to this theory, the two forms argentatus and fuscus met in Europe at both ends of the chain of distribution and formed "good" species in the classical sense. This theory was taken up, changed, refined and expanded by numerous authors.

In 1942 Ernst Mayr formulated the theory of the ring species based on this example . He assumed that, starting from the Caspi region, an archetypal form of the white-headed great gull had spread in three directions - one of them in the direction of the Arctic Ocean . From here one branch would have spread to the west and developed the dark shapes above, but a second would have spread to the east and across the Bering Strait to North America. The light-backed forms that were created in this way would then have crossed the Atlantic and appeared in Europe as populations of the herring gull ( argentatus and argenteus ), which could no longer reproduce with the black-backed gull ( fuscus ).

However, genetic evidence from 2003 shows that the ring species model does not apply here. In addition to the refuge in the Caspian region, there was probably a second one in the northern Atlantic. In the course of the expansion from the latter, the black-headed gull developed in the west (previously mostly not included in the scenario), in the central Atlantic and Mediterranean areas the forms atlantis and michahellis (Mediterranean gull) as well as argentatus (herring gull) to the north and armenicus (Armenian gull to the north of the Mediterranean) ). From the Caspi region, however, there was a spread northwards and later westwards ( fuscus ) and eastwards. The eastern chain of forms does indeed extend - according to Mayr's assumption - across the Bering Strait to the east of North America. A spread across the Atlantic to Europe apparently never took place. The circle of shapes does not close at the ends, as previously assumed. And if this step could still take place in the distant future, an important condition of the ring species model has not yet been met.

If these results are included in the system, a breakdown of the herring gull into a European ( argentatus ) and an American species ( smithsonianus ) is essential. The species status of the East Siberian form vegae is still unclear . But it is evidently closer to smithsonianus than argentatus . The taxon "White-headed gull" established in the 1990s is therefore also paraphyletic and is now divided into the Mediterranean gull ( L. michahellis ) and Armenian gull ( L. armenicus ), which are closely related to the herring gull, and the steppe gull ( L. cachinnans) ), which is more closely related to the lesser black-backed gull. The affiliation of the forms barabensis and mongolicus from Central Asia is still controversial .

species

literature

  • J.-M. Pons, A. Hassanin, P.-A. Crochet: Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers . Molecular Phylogenetics and Evolution, Volume 37, Issue 3, December 2005, pages 686-699 doi : 10.1016 / j.ympev.2005.05.011
  • Martin Moynihan : A Revision of the Family Laridae (Aves) , American Museum Novitates No. 1928, American Museum of Natural History, New York 1959, PDF
  • Jonathan Dwight: The gulls (Laridae) of the world; their plumages, moults, variations, relationships and distribution , Bulletin of the American Museum of Natural History, Vol. 52, Art. 3, pp. 63-401, New York 1925, PDF
  • Dorit Liebers, Peter de Knijff and Andreas J. Helbig : The herring gull complex is not a ring species , The Royal Society 271, London 2004, pp. 893-901
  • 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
  • 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
  • Jürgen Haffer : Systematics and taxonomy of the Larus argentatus species group. In: 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 .
  • GS Tuck, H. Heinzel: The sea birds of the world , Paul Parey publishing house, Hamburg / Berlin 1980, ISBN 3-490-07818-7

Web links

Commons : Larus  - collection of images, videos and audio files
  • Larus on the IUCN Red List of Threatened Species.

Individual evidence

  1. Pons et al. (2005), p. Literature and http://www.worldbirdnames.org/
  2. a b c Moynihan (1959), pp. 18f, s. literature
  3. a b Dwight (1925), p. 77, p. literature
  4. Olsen / Larsson (2003), p. 128, s. literature
  5. Olsen / Larsson (2003), p. 18, s. literature
  6. Pons et al. (2005), p. 692, s. literature
  7. a b Pons et al. (2005), p. 695, s. literature
  8. inter alia Moynihan (1959), p. 20, s. literature
  9. Pons et al. (2005), p. literature
  10. Olsen / Larsson (2003), s. literature
  11. ^ Haffer in Glutz v. Blotzheim, s. literature
  12. a b Liebers et al. (2004), p. literature