Chroicocephalus
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Portrait of a gray-headed gull ( Chroicocephalus cirrocephalus ) |
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| Eyton , 1836 |
Chroicocephalus is a genus of gulls that wasseparatedfrom the genus Larus after a taxonomic reorganization of the Laridae family after 2005. It includes twelve relatively small to medium-sized gull species. The genus is distributed worldwide, four species are found in the northern hemisphere, the rest of them have their distribution center in the southern hemisphere. One species, the gray-headed gull, is found in both Africa and South America.
The head cap, which is dark in the breeding dress, is characteristic of some species of the genus; in some others it is lighter or only hinted at, in some it is completely absent. The genera Leucophaeus and Ichthyaethus also have dark head caps, so a close relationship between these groups has been assumed. However, genetic studies have shown that this trait is unsuitable for determining family relationships. It is a very original feature of the seagulls that has been preserved in some species but has been discarded in others. This happened several times in the course of tribal history and even very closely related species such as the black-headed gull and the hard-leaved gull can differ in this regard.
The affiliation of the Cape Gull ( Chroicocephalus saundersi ), which differs greatly in some characteristics, to this genus is controversial. Genetic studies suggest that this taxon belongs to its own genus ( Saundersilarus ). However, this has not yet been officially recognized. The two species of herring-headed gull ( Chroicocephalus novaehollandiae ) and red-billed gull ( Chroicocephalus scopulinus ), like the hard-headed gull ( Chroicocephalus hartlaubii ), were considered subspecies of a species for a long time. Today all three taxa are generally granted species status.
description
The species of the genus Chroicocephalus are relatively small to medium-sized, slightly built to moderately strong gulls. The smallest and lightest species is the Bonaparte gull with a body length of 28-30 cm and a weight of 170-230 g , the largest and most powerful with a body length of 44-48 cm and a weight of about 478 g, the Andean gull .
The beak of the Chroicocephalus species is relatively long, slender to medium-strong and not very high, flat on the side with a relatively long tip and a relatively flat gonys angle . The Gonys is only slightly curved to almost straight. The nostril is teardrop-shaped and located on the basal part of the beak. The beak is colored red, brown or black. There are no spots or bandages, and often the tip of the beak is black. The feet and legs are reddish or brown.
Six species of the genus show a dark head cap when brooding. In contrast to other species, this leaves out the back of the head and neck, so that this part remains white. The cap of the gray-headed gull is gray, and that of the hard-leaved gull is indicated as a fine edge. It is absent in the other four species. The eye shows either a light, yellowish to whitish or a brown iris . The narrow, often colored orbital ring is hardly noticeable in many species. In the species with dark head caps, the white lids usually contrast.
The mantle, back and upper sides of the wings are light gray in all species. The wide, white trailing edge of the wing, which is typical of the Larus species, is missing; at most there is a light edge. For this, there is always a white, wedge-shaped field on the distal part of the hand wing, starting at the bow of the wing. The distribution of black in the hand swing pattern varies greatly. Most species have black subterminal or end bands of varying sizes. The underside of the hand wing is mostly blackish to a large extent. The white tail is cut off relatively straight. In immature birds it shows a black band.
Thin-billed gull in breeding plumage
Bonaparte gull
Hardwood gull
Gray-headed gull
Systematics
External system
A large part of all seagull species has long been in the genus Larus 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. the 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:
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Chroicocephalus (including black-headed gull) |
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Saundersilarus (Cape Gull) |
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Hydrocoloeus (Little Gull and Rose Gull) |
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Creagrus (fork-tailed gull) |
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Rissa (including kittiwakes) |
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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
As early as 1959, Martin Moynihan summarized the species listed here as “masked gulls” based on behavioral characteristics and morphology . In 2005, the internal relationships of this group were genetically examined more closely. On the one hand, the monophyly of this group emerged, on the other hand (as previously assumed on the basis of other studies) that two taxa from the northern hemisphere - the thin-billed gull and the Bonaparte gull - split off from the rest of the group relatively early. The rest of them are a group that occurs almost exclusively in the southern hemisphere. An exception is the black-headed gull, which inhabits large parts of the Palearctic , but seems to be related to the group of southern taxa. The probably closely related black-headed black-headed gull, also represented in the northern hemisphere, was not included in the study. The relationships were detailed as follows (names have been updated compared to the study):
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The authors also relate this cladogram to temporal estimates. According to this, the thin-billed and Bonaparte gulls split off about 1.85 million years ago and colonized an ancestor of the southern group in South America. Further radiation then took place in a relatively short time. From South America, Africa and then the northern hemisphere and the Australian area were probably settled between 0.55 and 0.38 million years ago. Another radiation took place here between 0.24 million and 0.13 million years. South America settled in Africa a second time, an assumed 0.07 million years ago. This is where the African subspecies of the gray-headed gull emerged.
species
- Thin-billed gull ( Chroicocephalus genei )
- Bonaparte gull ( Chroicocephalus philadelphia )
- Red-billed gull ( Chroicocephalus scopulinus )
- Herring-headed gull ( Chroicocephalus novaehollandiae )
- Maori gull ( Chroicocephalus bulleri )
- Andean gull ( Chroicocephalus serranus )
- Brown- headed gull ( Chroicocephalus brunnicephalus )
- Patagonian gull ( Chroicocephalus maculipennis )
- Black-headed gull ( Chroicocephalus ridibundus )
- Gray-headed Gull ( Chroicocephalus cirrocephalus )
- Hard-leaved gull ( Chroicocephalus hartlaubii )
- Cape gull ( Chroicocephalus saundersi )
literature
- Andrew D. Given, James A. Mills, Allan J. Baker: Molecular Evidence for recent Radiation in Souther Hemisphere Masked Gulls , The Auk 122/1 (2005), pp. 268-279
- 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
- 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
- Urs N. Glutz von Blotzheim , KM Bauer : Handbook of the birds of Central Europe. Volume 8 / I: Charadriiformes. Part 3, AULA-Verlag, Wiebelsheim 1993/2001, ISBN 3-923527-00-4 , pp. 273-282.
- GS Tuck, H. Heinzel: The sea birds of the world , Paul Parey publishing house, Hamburg / Berlin 1980, ISBN 3-490-07818-7
Web links
Individual evidence
- ↑ Pons et al. (2005), p. Literature and http://www.worldbirdnames.org
- ↑ Given et al. (2005), p. 277f, see literature
- ↑ Pons et al. (2005), see literature
- ↑ a b c d Moynihan (1959), pp. 13f, s. literature
- ↑ a b Dwight (1925), pp. 79f, s. literature
- ↑ Pons et al. (2005), p. 692, s. literature
- ↑ a b Given et al. (2005), see literature