Ravens and crows

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Ravens and crows
Common raven

Common raven

Systematics
Subclass : New-jawed birds (Neognathae)
Order : Passerines (Passeriformes)
Subordination : Songbirds (passeri)
Superfamily : Corvoidea
Family : Corvids (Corvidae)
Genre : Ravens and crows
Scientific name
Corvus
Linnaeus , 1758
Arch raven
Flying hooded crow
Trail of a crow in the snow

Raben and crows together form the genus Corvus in the family of crows (Corvidae). The larger representatives are called "ravens", the smaller ones as "crows". However, this is not a taxonomic classification. The genus includes 42 species that are distributed almost worldwide and are only absent in South America. In Europe the common raven , the carrion crow ( carrion crow and hooded crow) and the rook occur. As a naturalized neozoon, the golden crow has also been breeding in the Netherlands since the late 1990s .

Raben and crows are among the largest species within the order of the Sperlingsvögel : The two main representatives of the genus are the thick-billed raven ( Corvus crassirostris ) and Raven ( Corvus Corax ) each to a length between 60 and 70 cm and a body weight of up Can reach 1.5 kg and are therefore the largest passerine birds of all.

etymology

The term Crow is in almost all Indo-European languages an onomatopoeic name that their typical vocalizations mimics: . Ahd krâwa , . Mhd KRA , kraeje , Kreie or krowe , Old Slavonic Kraja .

Rabe (ahd. Hraban , mhd. Rabe ) is related to Dutch raaf , English raven and old Icelandic hrafn . The word comes from the onomatopoeic root ker , which imitates scraping or scratching noises; also rake and croak are associated with it. Like the crow, the raven was called a "croaker".

features

Ravens and crows are strongly built birds, their sturdy legs have long running bones . The front of the legs is covered with horn scales while the back is smooth. Many species have developed very long and highly arched beaks, of which the ore raven is by far the largest. A pronounced sexual dimorphism does not exist in terms of plumage or size. Females of a species are usually slightly smaller than males, but there is always an overlap between female and male body measurements.

Basically, the entire body with the exception of the beak and legs is feathered down from the running bone. Small parts of the face are only feathered in some species. As is typical of the entire family, ravens and crows have nasal feathers that cover the upper beak. However, they are differently pronounced: In the white-necked raven ( Corvus cryptoleucus ), for example, they cover more than half of the beak, while the closely related rook ( Corvus frugilegus ) no longer has any beak plumage in its old age.

Gray to black plumage tones dominate, only a few species have white markings. There are exceptions, however: The old crow ( Corvus tristis ), a crow that is conspicuously white and gray as a young bird, only loses its light feathers almost completely with age and then appears uniformly black. The feathers of the Salvadoran crow have a white feather base. The feathers are black only from the middle. In living birds, this feather base is visible when strong winds blow the feathers apart.

distribution and habitat

The genus Corvus is distributed almost worldwide and is only absent in South America, where the blue ravens ( Cyanocorax ) occupy their ecological niche . East of the Wallace Line they are the only corvids . Corvus is a young genus and not only spread throughout the Palearctic , but also advanced to southern Africa and Australia, where corvuses had not previously existed. They also settled the sub-Antarctic and even reached remote islands such as the Hawaiian archipelago and New Zealand .

Seasonal migration behavior is only shown by some species in the northern hemisphere , while the species in the tropics and subtropics are mostly stationary or line birds . The rook populations of northern latitudes, for example, regularly migrate south in winter. In recent decades, however, their migration distance has decreased noticeably, which is probably due to an improved food supply in the breeding regions. The same applies to many other species of corvids, whose migratory behavior is a reaction to food sources dwindling in winter. The predominantly carnivorous common raven ( Corvus corax ) does not depend on seasonal food and therefore not only thrusts further north than all other species, but can also stay on the rocky cliffs of Greenland in the arctic winter .

Ravens and crows are very adaptable and use very different habitats. In this genus there are jungle and mountain dwellers as well as rock, cave and tree nesters. Their adaptability is due to a lack of specialization. Since ravens and crows are very undemanding when it comes to their food choices and their intelligence also makes it difficult to access food, they can survive in a variety of different habitats. Some species that met humans early in their evolutionary history became successful cultural successors . The Indian glossy crow ( Corvus splendens ) has gone the furthest of all species: It has completely given up its original habitat and is now only found near human settlements, from where it even displaces larger ravens and crows.

food

rook

Ravens and crows use a very diverse range of food, which includes both animal and vegetable food. However, not all species are equally omnivorous . The common raven , for example, is a pronounced carnivore and scavenger. Since ravens and crows are opportunistic when searching for food and prefer to use available or abundant food, the proportions of certain food sources in the food can vary regionally and seasonally. In addition, they are very curious and test every unknown object for its usability. This is due to the fact that rubber rings are often found in the stomach of rooks , which birds thought of as pieces of meat because of their consistency.

Ravens and crows show great ingenuity when it comes to getting food. Hooded crows in Finland , for example, have learned to pull the unguarded fishing lines of ice fishermen out of their holes in order to then eat the fish hanging on them. Straight-billed crows , in whose diet long- horned beetle larvae play a major role, first process leaf stalks with great care, and then treat the wood-dwelling larvae with them until they bite into the stalk and can be pulled out of their feeding passages by the crow. In seabird colonies nesting on rocky cliffs, common ravens use various strategies to get hold of eggs and young birds. If breeding pairs fail in guillemot colonies, the resulting gaps are used immediately. The common raven ends up in this gap and harasses one of the directly neighboring breeding birds until it gets up and attacks the raven. The raven backs away. When the guillemot wants to return to its nest, the raven grabs it by the leg and pulls it over the edge of the nest. Both fall, but the raven is more agile in the air, catches itself faster and can grab an egg or chick with its beak and fly away. Breeding kittiwakes are attacked in a similar way , here common ravens throw tufts of grass at the breeding birds in order to drive them away from the nest. Kleptoparasitism is also common. American crows wait for gray squirrels to fetch food from a garbage can inaccessible to the crows and then chase it away from them. Flocks of ravens and crows can chase away larger birds of prey from carcasses or they can be distracted collectively in order to steal lumps of prey from them. Ravens and crows, especially common ravens, kill significantly more lambs in Germany than wolves.

intelligence

American crow

Ravens and crows are some of the most intelligent birds. For example, in experiments they show the ability to plan complex actions. When hiding food, they show both great memory skills and the ability to empathize with others. A raven seems to know that a food hiding place is only safe if it is not watched while hiding. In addition, ravens show an amazing learning behavior (making tools, using road traffic to crack nuts and fruits, picking up nuts run over by drivers at red lights). Shortly after the behavior was observed in an individual, it was also observed within a radius of several kilometers from the site of discovery. This is interpreted as evidence of quick learning ability. Often they are seen as companions of wolves or other predators, to participate in the rift or to steal.

In 2006, a team led by Heather Cornell at the University of Washington found through experiments with masks that the American crows on the university campus were able to remember attackers. They also passed this knowledge on. In the immediate vicinity, 60% of the crows react to the attacker's mask after just two weeks. In a subsequent study it could be shown that this knowledge about the danger was even passed on to the offspring. The crows of the next generation also recognized the mask, which was actually unknown to them, as a danger.

In 2012, in an experiment with New Caledonian crows, Alex Taylor of the University of Auckland found out that the birds have the ability to infer a hidden cause of an observed phenomenon. The crows established a connection between a stick that seemed to move on its own and a person who left a hiding place near the stick shortly afterwards. Previously, it had been suggested that only humans are able to draw such a conclusion.

In 2014, researchers at the Max Planck Institute for Ornithology in Seewiesen presented the first results that indicate that the ravens have a certain ability to communicate through gestures.

evolution

There also seem to be interesting aspects to the evolution of corvids. Washington University determined based on the mtDNA of ravens that the Eurasian-North American so-called Holarctic ravens separated more than 2 million years ago from the so-called Chihuahua ravens, which spread in Central and South America. A subspecies of the Chihuahua raven, namely the so-called California raven, mixed with the Eurasian raven about 10,000 years ago, which is said to have resulted in today's common raven, which practically replaced the Holarctic raven and is now spread over the entire northern hemisphere . With this, the researchers provided evidence of a backward evolution for the first time. that is, a much older form led to the development of a new species through hybridization . Something similar is assumed for the bison , which is said to have emerged from a hybrid of the Eurasian bison and the aurochs during the last ice age high and replaced the Eurasian bison, which is why rock carvings with two forms of bison each with short or long horns are found. The researchers at Washington University draw a comparison here with the Neanderthals whose genes entered the gene pool of modern humans through hybrids. They consider this inversion of speciation to be an underestimated process in the formation of new species.

Life expectancy

Ravens and crows can reach a great age. The following maximum ages have been proven for the individual species:

  • Rook: 20 years
  • Carrion crow: 19 years
  • Common raven: 28 years
  • New Holland Crow: 27 years
  • Salvadoran crow: 20 years

Mythology and cultural reception

Crow's nest made from hangers in Tokyo

The striking crows and ravens play a role in legends and fairy tales around the world. Accordingly, ancient gods and kings used their wisdom, intelligence and ability to fly. In parallel, these birds also play a role in popular belief and superstition . In many fairy tales, for example, there is often talk of the wise hiker "röiven" (old German), who shows stray hikers the right way (and often gives a few tips on the trip). Well-known are the Grimm fairy tales The Seven Ravens and The Raven .

In Norse mythology , the raven symbolizes wisdom , the god Odin always had the two common ravens Hugin and Munin with him, who sat on his shoulders and told him what was going on in the world. King Arthur is said to have been turned into a raven. The ravens were sacred to the Greek god Apollon (see Koronis ). In the story of the flood , Noah lets a raven fly ( Gen 8,6-7  ELB ). According to the Bible, the prophet Elijah is cared for by ravens during a time of famine ( 1 Kings 17 : 6  ELB ). In the Babylonian version of the Flood myth, the Atraḫasis epic , Atraḫasis sent three birds after the rain had ended: a dove, a swallow and a raven. The raven did not return, so Atraḫasis knew the land was accessible again. In both the Judeo-Christian and the older Babylonian version, the earth "fell" after the flood, which contributed to the bad image of the raven as a bird of bad luck. With Christianization, the raven was increasingly seen in Europe as a demonic being or an evil animal, due to its mythological significance in the previous cults (e.g. as a Wotans bird, battle leader and hunting companion), which accompanied the devil as a scavenger and heralded damage as an unlucky raven. The assumption of a connection between the raven and the devil goes back mainly to the church fathers. The corpses of the hanged were often not buried in the Middle Ages, when the raven, like the rook or carrion rook, was given an ambivalent interpretation, and even later; so the raven even became a gallows bird . On the other hand, the tame, affectionate and speaking raven also plays a role as a pet.

A big part of Rabe plays in North American Indians - and Inuit - fairy tale , in which he, in contrast to West Africa plays a positive role fairy tale. In India , crows accompany the goddess Kali . In Christian legends, the crow is the messenger of Saint Oswald , and two ravens pursued the murderers of Meinrad von Einsiedeln and brought them to justice.

Up to the present day ravens and crows are frequently found symbols in literature, film and the way of life. Examples are poems and films with ravens or crows as protagonists or at least an essential design element. One of the most famous poems in the English-speaking world is The Raven by the American writer Edgar Allan Poe . The German writer Wilhelm Raabe was inspired by Poe's poem in his novel Das Odfeld for the battle of ravens that took place in him . Even Wilhelm Busch immortalized in literature in his picture story Hans Hucke leg of Jonah the form of a raven. Witches and wizards can u. a. to be transformed into crows, a motif that the children's book author Otfried Preußler took up in detail in his book Krabat , as well as the makers of the television fairy tale The Magic Raven Rumburak . The children's book The Little Raven Socke is also about a raven or comics like The Crow . In pop music , bands give themselves names such as B. Corvus Corax . The term unlucky fellow stands for a person who is constantly unlucky.

species

Bristle Raven, Kenya
Big-billed crow
rook
Tortoise in Namibia
Tasman crow

literature

Web links

Commons : Ravens and Crows ( Corvus )  - Collection of images, videos and audio files
Wiktionary: Krähe  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Rabe  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Colin Ryall: The House Crow population in the Netherlands and its implications for the species' spread across the Europe. In: A. Woolnough, C. Feare, G. Meier (Eds) 2008: Proceedings of the International Invasive Bird Conference, Fremantle, Western Australia. : P. 27. Abstract as PDF ( Memento from March 26, 2012 in the Internet Archive )
  2. ↑ Duden: Etymology. Dictionary of origin of the German language. Bibliographisches Institut Mannheim, Dudenverlag 1963, ISBN 3-411-00907-1
  3. ↑ Madge & Burn 1994 , pp. 48-49.
  4. ^ Higgins, Peter & Cowling: Handbook of Australian, New Zealand & Antarctic Birds: Volume 7 Boatbill to Starlings, Part A: Boatbill to Larks . P. 757.
  5. ↑ del Hoyo et al. 2009 , pp. 494-510.
  6. ↑ del Hoyo et al. 2009 , pp. 552-554.
  7. ↑ del Hoyo et al. 2009 , pp. 514-516.
  8. ↑ Glutz von Blotzheim & Bauer 1993 , p. 1817.
  9. ↑ del Hoyo et al. 2009 , p. 531.
  10. ↑ Goodwin 1986 , pp. 23-27.
  11. ↑ https://m.geo.de/natur/tierwelt/19945-rtkl-tausende-tote-laemmer-raben-fuer-mehr-tote-schafe-verendunglich-als
  12. ^ Paul Rincon: Crows and jays top bird IQ scale BBC News, February 22, 2005
  13. ↑ Bayerischer Rundfunk: Intelligence of the Animals: Refined Ravenvögel . October 30, 2018 ( br.de [accessed May 9, 2020]).
  14. ^ Romana Gruber, Martina Schiestl, Markus Boeckle, Anna Frohnwieser, Rachael Miller: New Caledonian Crows Use Mental Representations to Solve Metatool Problems . In: Current Biology . February 2019, doi : 10.1016 / j.cub.2019.01.008 ( sciencedirect.com [accessed February 12, 2019]).
  15. ↑ Cameron Buckner, Stephan A. Reber, Thomas Bugnyar: Ravens attribute visual access to our competitors . In: Nature Communications . tape 7 , February 2, 2016, doi : 10.1038 / ncomms10506 .
  16. ↑ Video presentation by Joshua Klein: The amazing intelligence of crows TED.com
  17. ^ Social learning spreads knowledge about dangerous humans among American crows , accessed June 15, 2020
  18. ↑ Crows recognize hidden causes . In: Spiegel.de, September 18, 2012, accessed on August 19, 2012
  19. ↑ RABEN communication with a black pen deutschlandfunk.de, current research on June 16, 2014
  20. ↑ Kearns et al. a .: Nature Communications, Genomic evidence of speciation reversal in ravens . 2018, doi: 10.1038 / s41467-018-03294-w
  21. ↑ Pauline Palacio, Véronique Berthonaud, Claude Guérin, Josie Lambourdière, Frédéric Maksud, Michel Philippe, Delphine Plaire, Thomas Stafford, Marie-Claude Marsolier-Kergoat, Jean-Marc Elalouf: Genome data on the extinct Bison schoetensacki establish it as a sister species of the extant European bison (Bison bonasus) . In: BMC Evolutionary Biology 17 , 2017, p. 48, doi: 10.1186 / s12862-017-0894-2 .
  22. ↑ Wolfgang Grummt , H. Strehlow (Ed.): Zoo animal keeping birds . Verlag Harri Deutsch, Frankfurt am Main 2009, ISBN 978-3-8171-1636-2 .
  23. ^ Will-Erich Peuckert: Raven (Corvus corax). In: Concise dictionary of German superstition. Volume 7 (1935/1936), Col. 427-457.
  24. ↑ Gundolf Keil : "blutken - bloedekijn". Notes on the etiology of the hyposphagma genesis in the 'Pommersfeld Silesian Eye Booklet' (1st third of the 15th century). With an overview of the ophthalmological texts of the German Middle Ages. In: Specialized prose research - Crossing borders. Volume 8/9, 2012/2013, pp. 7–175, here: pp. 105 f.
  25. ^ Christian Hünemörder , Marianne Rumpf: Lexicon of the Middle Ages . Volume 7 (1995), Col. 381 f.
  26. ^ Wilhelm Heizmann , Hans Reichstein: Rabenvögel. In: Reallexikon der Germanischen Altertumskunde. 2nd Edition. Volume 24 (2003), pp. 42-45.
  27. ↑ The story of the creation of the raven Tu-lu-tau-guk, in Das Märchenbuch. Edited by Claudia Schmölders . Insel TB, 998, Frankfurt 1987. Transferred from Paul Sock, pp. 179-196. Excerpt , in the transfer from Patrick Rotter.
  28. ↑ DWDS - Unlucky Raven. Retrieved March 13, 2018 .