Systematics of the corvids
The scheme of corvids includes the relationships of the family of corvids (Corvidae) both to other groups of birds and the species of this family together. While the body structure, vocalizations and way of life of corvids have been well researched, their systematics has long been controversial.
In the early phase of taxonomy , Carl von Linné placed all known species of corvids in the genus Corvus . Only gradually did more differential concepts prevail, which led to an increasing number of genres being established and recognized. In 1944, Dean Amadon established a comprehensive system of corvids that remained influential for many decades, but hardly corresponded to the actual relationships.
For a long time, the methodology for examining the relationships was limited to plumage features, the superficial shape of the body and beak, and vocalizations. From today's point of view, this resulted in systematics that were hardly applicable, since these characteristics in corvids were mostly the result of convergent evolution and other characteristics such as the structure of the organs were hardly taken into account. Even osteological comparisons usually did not provide clear results, but rather demonstrated the similarity of all corvids. Molecular biological studies that have been able to conclusively illustrate the relationships between the genera have only recently brought clarity . The basis for the current system of corvids is primarily an investigation of various DNA sequences by Per Ericson, Anna-Lee Jansen, Ulf S. Johansson and Jan Ekman from 2005, which combined and supplemented the results of earlier studies.
Comprehensive studies are still lacking for the external systematics and the relationships within the individual genera: there are no systematics based on molecular biology for the genus ravens and crows ( Corvus ) with around 50 species, or for most of the smaller genera. Only the new world jay , especially the blue raven ( Cyanocorax ), have been researched relatively well. Next of kin of the corvids are probably the Strangler (Lanidae), the mud nest crows (Corcoracidae) and the Birds of Paradise (Paradisaeidae). The origin of the corvids is very likely in Southeast Asia, where most of the genera are native.
External system
The corvids are a rather original family of songbirds. Charles Gald Sibley and Jon Edward Ahlquist chose the corvidae in 1990 as a type of Corvida, one of two major lines of development in the Sibley-Ahlquist taxonomy named after them . In the Sibley-Ahlquist taxonomy, the Corvida were opposed to the smaller, sparrow-like Passerida and mainly comprised large, powerful songbirds, most of which are found in Southeast Asia and Australia. Corrections to the Sibley-Ahlquist taxonomy were not lacking in the following: Among other things, it turned out that the Corvida are paraphyletic, i.e. do not include all descendants of a common ancestor. In principle, the basic statement of Sibley's and Ahlquist's study was confirmed insofar as the corvids and closely related families form the sister group of the little Passerida. The ancestor of this group was of Australian origin and colonized Southeast Asia after the Australian continent broke away from Antarctica 53 million years ago and drifted northeast .
The current distribution of corvids suggests that the family originated in Southeast Asia: apart from the evolutionarily very young ravens and crows ( Corvus ), no corvids are found east of the Wallace line , while the most primitive genera of the family can be found all southeast of the Himalayas. The closest relatives of corvids are probably the Strangler (Lanidae). They share some characteristics with the Corvidae, such as the so-called "strangler tooth", the hook-shaped tip of the upper bill, or the composition of the proteins of the albumen . This is also supported by a revision of the Sibley-Ahlquist taxonomy from 2005, which identifies the shrike as a sister group of the corvids. The common closest relatives of these two families are the Australian blue jays (Corcoracidae) and the birds of paradise (Paradisaeidae).
Internal system
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Relationships among recent corvids according to Ericson et al. 2005
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The first fossil forms of corvids appear for the first time in the Miocene : First Miocorvus in the Middle Miocene of France , then later Miopica ( Ukraine ) and Miocitta ( USA ) each in the Upper Miocene. The great variety of forms in Southeast Asia suggests that the corvids were the first to split into different forms: of 25 genera, six occur exclusively in Southeast Asia, and almost all Old World genera can also be found there. DNA studies support this hypothesis: According to this, the most original species of corvids come from Indonesia and the region southeast of the Himalayas .
The most basic group within the corvids consists of the four genera endemic to Southeast Asia: dangling star ( Dendrocitta ), rocket-tailed star ( Crypsirina ), ladder- tailed star ( Temnurus ) and mourning star ( Platysmurus ) as well as mountain crows ( Pyrrhocorax ) with a Palearctic distribution. While the first four genera are all tree and forest inhabitants, the mountain crows represent an initial adaptation to open terrain. They nest in rocks and also occur in high mountains above the tree line.
The kittas ( Urocissa ) together with the green star ( Cissa ) form another side branch . They, too, are restricted to Southeast Asia and face a large clade of genera with worldwide distribution as a sister group.
Within this group, there are three major branches: the first comprises the blue magpies ( Cyanopica ) in South Western Europe and Eastern Asia and the holarctic Unglückshäher . Both genera are adapted to more arid habitats than the more native corvids. The second branch is represented by the new world jars . Their ancestors immigrated to North America 8-10 million years ago in the Miocene over a land bridge that existed at that time and was covered with subtropical deciduous forests. In the Pliocene 5.3–3.6 million years ago, they then advanced across the emerging isthmus from Panama to South America.
The third branch splits into two large and relatively young groups: A smaller consists of the Real magpies ( Pica ) on one hand and the Akazienhähern ( Zavattariornis ), the Piapias ( Ptilostomus ) and Saxaulhähern ( Podoces ) on the other. The latter three genera are adapted to steppe to desert-like habitats, while the real magpies prefer moderate, semi-open landscapes. The sister group of these genera consists of the genera of the nutcrackers ( Nucifraga ) and Garrulus, as well as the ravens and crows ( Corvus ), which originated in the Palearctic . Nucifraga and Garrulus are forest inhabitants and are highly adapted to conifers and oaks as food sources. The very young ravens and crows, on the other hand, evolved from a jay-like ancestor who knew how to colonize open and semi-open landscapes. As a result, the ravens and crows differentiated very quickly and advanced into many different habitats such as mountains, deserts, tropical forests, savannahs and human settlements. In this way they also colonized Oceania, Australia, New Zealand and the Caribbean islands; all areas that had not previously belonged to the distribution area of the corvids.
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literature
- Dean Amadon: The Genera of Corvidae and their Relationships. In: American Museum Novitates 1251, January 1944. pp. 1-21.
- Josep del Hoyo, Andrew Elliot, David Christie (Eds.): Handbook of the Birds of the World. Volume 14: Bush-shrikes To Old World Sparrows. Lynx Edicions, Barcelona 2009. ISBN 9788496553507 .
- Per GP Ericson, Anna-Lee Jansen, Ulf S. Johansson, Jan Ekman: Inter-generic Relationships of the Crows, Jays, Magpies and Allied Groups (Aves: Corvidae) Based on Nucleotide Sequence Data . In: Journal of Avian Biology 36, 2005. pp. 222-234.
- Urs N. Glutz von Blotzheim , KM Bauer : Handbook of the birds of Central Europe. Volume 13 / III: Passeriformes. 4th part. AULA-Verlag, Wiesbaden 1993, ISBN 3-89104-460-7 .
- Derek Goodwin : Crows of the World. 2nd Edition. The British Museum (Natural History) , London 1986, ISBN 0565009796 .
- Peter Jeffrey Higgins, John M. Peter & SJ Cowling (Eds.): Handbook of Australian, New Zealand and Antarctic Birds. Volume 7: Boatbill to Starlings . Oxford University Press, Melbourne 2006. ISBN 978-0195539967 .
- Knud A. Jønsson, Jon Fjeldså: A Phylogenetic Supertree of Oscine Passerine Birds (Aves: Passeri) . In: Zoologica Scripta 35, 2006. doi : 10.1111 / j.1463-6409.2006.00221.x , pp. 149-186.
- Steve Madge, Hilary Burn: Crows & Jays. Princeton University Press, Princeton 1994. ISBN 0-691-08883-7 .
- John M. Marzluff , Tony Angell: In the Company of Crows and Ravens . Yale University Press, New Haven and London 2005. ISBN 0-300-10076-0 .
- Richard Meinertzhagen: Introduction to a Review of the Genus Corvus. In: Novitates Zoologicae 33, 1926. pp. 57-121. ( Online )
Individual evidence
- ^ Jønsson & Fjeldså 2006 , p. 152.
- ↑ a b del Hoyo et al. 2009 , p. 494.
- ↑ Jønsson & Fjeldså 2006 , p. 161.
- ↑ a b c d Ericson et al. 2005 , p. 232.
- ↑ Madge & Burn 1994 , p. XVI.
- ↑ del Hoyo et al. 2009 , p. 495.
- ↑ del Hoyo et al. 2009 , p. 505.
- ↑ Glutz von Blotzheim & Bauer 1993 , pp. 1653–1654.
- ↑ del Hoyo et al. 2009 , pp. 515-516.