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The Raven

Corvus corax

 Green_Ball.gif (968 bytes)  Der Kolkrabe (Text in deutsch)

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Ecology, Extinction, Recolonization and Habitat Use in Hesse.

...edited by Thomas Müller and Sascha Rösner

The Raven
... in Hesse (Germany)

Green_Ball.gif (968 bytes) General Information

Green_Ball.gif (968 bytes) Field characters

Green_Ball.gif (968 bytes) Distribution

Green_Ball.gif (968 bytes) Ecology

Green_Ball.gif (968 bytes) Related Species

Green_Ball.gif (968 bytes) Endangering

Green_Ball.gif (968 bytes) References

Green_Ball.gif (968 bytes) Further Links
Green_Ball.gif (968 bytes) Survey 1999

Green_Ball.gif (968 bytes) Extinction

Green_Ball.gif (968 bytes) Recolonization

Green_Ball.gif (968 bytes) Current Distribution

Green_Ball.gif (968 bytes) Habitat Characters

Green_Ball.gif (968 bytes) Thanks


General Information

The raven – Corvus corax (L. 1758) - largest of the songbirds (Passeriformes) is possibly well known. Not only from the scientific point of view but even more through stories, such as Wilhelm Buschs "Huckebein" or "The raven" by Edgar Ellan Poe and many more featuring the intelligent black fellows. Also in many religions and myths the bird plays an important role, e.g. Haida-culture and in former times in some nothern european peoples myths (Kunin and Munin - the holy birds of Odin).

 

Field Characters

Sized like a common buzzard Buteo buteo (about 65cm length) the raven is the largest of the Corvidae familiy. Its black plumage and heavy black bill gives it a rather massive impression. Furthermore its relatively narrow, pointed wings,
the wedged tail and its easy soaring flight with regular powerful upbeats identify the raven, which for all its bulk (weighing appr.1250g) is a great aerial acrobat. Depending on the light the dark plumage shows a metallic gloss.The scientific name is onomatopoetical and derives from greek meaning "the croaker". The typical and sonorous calls deep repeated pruk-pruk and  "grock grock grock" often signal the raven´s presence from the distance. Apart from this the raven possesses a large variety of different calls. For example wooden, xylophone-like or even barking sounds (Bezzel 1993).

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picture 1: Raven, Lake Baikal (Central Sibiria).



Distribution

The raven occurs nearly in the entire northern hemisphere. It breeds in North-America (distribution map USA), Greenland and large parts of Eurasia.

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map 1: distribution of Corvus corax. source: Glutz v. Blotzheim & Bauer  (1993).

In the western palaearctis it breeds in the whole of the scandinavian area, in eastern Europe to the Ural, in the south in Turkey, Greece, southern Italy, the mediterranean isles, in Spain and Portugal. Furthermore it also breeds in Morocco, Algeria and Tunesia. Bauer & Berthold (1997) mention 12.000 to 18.000 breeding pairs.

 

Ecology

The raven is a resident bird, i.e. it is not migratory but stays in the breeding area for the whole year.This applies at least to adult animals which often stay as a pair for many years. Young animals leave their parents breeding territory and travel some hundred kilometres. Doing so they get together in large flocks (up to few hundred individuals, Heinrich 1998). A flock of 40 was seen in middle Hesse in the Winter of 99/00. After three years they become sexually mature and establish breeding territories of their own. They build nests on trees and on rocks but can also use abondened  nests of birds of prey. Nests can be used for a number of years. The ravens start to breed relatively early in the year (February / March) and lay 2-6 eggs. The young hatch in April and fletch in May.

Ravens are omnivorus. They prey on small mammals but also on insects, young birds, amphibians and others. If there is carrion availible (such as in natural landscapes or extenisve pastures) it has an important role: Especially at the beginning of the breeding season when other resources are scarce the availibility of food becomes an important factor for the reproductive success (Lo Liu-chih 1997).

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Ravens are highly specialized on finding carcasses. They are often the first to discover a carcass (Selva 1999). Often already a few hours after a kill of wolves, they arrive at the dead animal. It has been reported that they follow wolf packs (Heinrich 1998, Mech 1995, Promberger 1992, Chadwick 1999). Wether there really is a causal relationship is currently being investigated in Yellwostone (research in Yellowstone).
picture 2: Raven at a wolves kill collecting meat, Poland.

In middle Europe we know about ravens visiting open rubbish dumps, animals killed by cars or deadborn livestock. In wilderness ravens can live up to an age of 20 years and 4 months (ringed bird). In captivity a raven lived for 69 years (Bezzel 1993).

 

Related Species
The nominate form Corvus corax includes 5-8 subspecies. The genus Corvus contains three further species. In Europe there are in total 11 species of the corvidae.

 
Species genus Corvus species of the family Corvidae
Corvus corone - Crow Garrulus glandarius - Jay
ssp. Corvus corone corone - Carrion Crow Perisoreus infaustus - Siberian Jay
ssp. Corvus corone cornix - Hooded Crow Nucifraga caryocatactes - Nutcracker
Corvus frugileus - Rook Pyrrhocorax graculus Alpine - Chough
Corvus monedula - Jackdaw Pyrrhocorax pyrrhocorax - Chough
Pica pica - Magpie
Cyanopica cyana - Azure-winged Magpie

 

Endangering

Respected and known as an intelligent fellow by some, it is also hated by others as "pestbird". The raven was poisoned, shot or clobbered to death and alike it many other corvidae have such a horrific history. Since the beginning of the 19th century many methods were intensively applied: poisonous chemicals such as strychnine and glucochloral are just an example. Because of such actions there was a decline in range and numbers. Finally in 1927 it could not be found anymore in middle Europe. Last nesting activities were in Luxembourg as early as the end of the 18th century and in 1919 in Belgium.

In Germany the raven originally was a breeding bird in all larger forest areas (Niethammer 1963). Since the middle of the 18th century a continuous decline in numbers was documented and around the turn of the century the raven was missing in Baden Württemberg, Hamburg, Palatinate, Saxony, Silesia, Westphalia and Thuringia (Niethammer 1988:50).

At the middle of the 19th century the raven was extinct in western middle Europe! Last refuges were in northern Germany, Poland and in the Alps. After the end of the aggressive persecution and beginning conservation activities the expansion to its former ranges began. The source for the recolonization came from the last refuges.

 

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map 2: The raven in middle europe.   cross: former nest, date: extinction of breeding occurence, hatching: refuges, arrows: direction of expansion. source: Niethammer (1963).

In some parts (North Rhine-Westphalia, Thuringia) also reintroductions took place. But although the raven has been continually spreading for a few decades it has not yet completely reached its former range-expansion. Only in a few states (Schleswig-Holstein, Mecklenburg -West Pomerania) it has regained its original ranges.

Not only in Europe but also in the USA raven numbers are increasing (diagram , map).

Nowadays closure of open rubbish dumps, the large number of perilous high-voltage-cables and disturbances (forestry works, climbing etc) of nesting places have a negative impact on breeding performance (Bauer&Berthold1997). In case carrion crows are hunted there is also the danger of mistaking a crow with the raven. In Germany ravens are hunted in 7 states.

 

The Raven in Hesse (Germany)

Hesse is a state located in the middle of Germany and covers about 21.000 square kilometers.

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Survey in Hesse 1999

The documentation of the ravens distribution by the authors began in October `99 in cooperation with the  and the Hessian Society for Ornithology and Nature Conservation (HGON). Questionnaires were sent to all the honorary ornithologists on the level of districts. Furthermore available literature was evaluated. Data till 1994 are from the survey of indicator species in Hesse (1990-1993) by M. Hormann (State Ornithological Station in Frankfurt/Main), the publication of W. Brauneis (1991) and the following local avifaunistic reports: Vogelkundlicher Jahresbericht in Marburg-Biedenkopf (HGON), Vogelkundliche Mitteilungen aus dem Kasseler Raum (Nabu, HGON, Naturschutzring Nordhessen), Vogelkundlicher Jahrebericht für das Mittlere Fuldatal (Naturkundliche Gesellschaft Mittleres Fuldatal e.V., HGON), Naturkundlicher Jahresbericht für das Mittlere Fuldatal (Naturkundliche Gesellschaft Mittleres Fuldatal e.V.), Avifaunistischer Sammelbericht für den Schwalm-Eder Kreis (Schaub, H. & S. Stübing), Vogelkundliche Berichte Lahn-Dill (Arbeitskreis Lahn-Dill, HGON, Nabu). The data collected with these methods are presented in the following maps.

 

Extinction

Before its extinction the raven probably inhabited nearly all places which offered it such possibilities as nesting places in old quarries or hollow trees and next to this open landscapes (foraging). At first the raven could stand the persecution but then it was chased away even from the larger woods in the hills. The last known brood in Hesse was as long ago as 1912. In 1926 Sunkel wrote:"The chapter on the raven can sadly only be an obituary" (Berck 1997). As the endangering of this species had become apparent first actions were taken in jurisdiction and the recolonization from the last refuges in Poland and the foothills of the Alps began.

After 75 ravenless years the first two broods were recorded in1985 in northern Hesse. The recolonization in Hesse has started and is still an ongoing process: in recent regional avifaunae (HGON, NABU) sightings of broods are often mentioned. Brauneis ´91 reports on the recolonization of the northern Hesse region.

 

Recolonization

In the early 80´s the raven started its comeback in Hesse. Coming from northeast it populated  the districts in Hesse step by step. The recolonization is shown on maps. The following maps (3 and 4) show the expansion of common ravens (Corvus corax) on the level of districts in Hesse during 10 years (1985 to 1995). Maps from 1912 to1998 illustrate the whole recolonization from extinction in 1913 up to today.
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map1985

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map 3: Distribution in Hesse in 1985.

map 4: Distribution in Hesse in 1995.

 

Following graph shows the recolonization of Hesse by the raven quantitatively. Data up to 1993 are taken from literature, data  from 1994 to 1999 are of  the own survey.  The data from literature were in some parts rather undetermined and the own survey lack data in the district Vogelsberg and in the district Schwalm-Eder in the years 1994 -1995. Thats why in 1994 it seems to be less ravens than in 1993. The increasing numbers in the last years are of special interest as numbers are still increasing in those northeastern districts of Hesse where the raven is already established since the mid 80´s. For example the number of breeding pairs in the district Werra-Meißner was in 1996 16 and raised up to 31 in 1999. As districts in central and southern Hesse have still low numbers of ravens or are not recolonized yet, its rather probable that numbers of ravens in Hesse will continue to increase in the next years.

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graph 1: Numbers of ravens in Hesse 1979-1999. BP=breeding, BV=assumption of breeding,
BZ=observation during breeding period

 

Current Distribution in Hesse

After the first two breedings in 1985 the raven meanwhile is established as breeding bird in many districts of Hesse. According to results of the current survey the raven occurs in 14 districts. After Berck (1997) in Hesse 70 breeding pairs occured, today there are already about 110 pairs in Hesse (Rösner & Müller i.p.) The following maps still lack some data (especially Vogelsberg district).

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map 5: Known distribution of ravens in Hesse in 1979 and 1999.
 

 

Habitat Characters

According to its ecology ravens need specific breeding habitats. In Hesse it uses high beeches or firs as nesting-trees. Furthermore good food supply close to the nest is of crucial importance for the breeding success (Lo Liu-chih 1997). As open landscapes are the mean hunting habitat, breeding sites are mostly located at borders of forests and soils with low biomass production (e.g. red sandstone) are obviously avoided.

 

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map 7: Breeding sites are mainly located outside red sandstone areas. (orange: red sandstone, olive-grey: basalt,  brown and gray-blue: slate and graywacke, purple: shell-
lime, black line: border of Hesse).		 map 8: Breeding sites in relation to distribution of forests /open landscapes:  Forest borders as breeding sites are preferred (green: forest, orange: open landscape, blue: breeding site).

 

Thanks

Without being supported by many persons this investigation about the recolonization and distribution of ravens in Hesse would not have been possible. Special thanks to M. Hormann and Dr. K. Richarz of the ornithological station of Hesse, Rhineland Palatinate and Saarland in Frankfurt/Main and the Hessian Society for Ornithology and Nature Conservation (HGON) as well as to Dr. K.-H. Müller (department of Geography of the Philipps-University Marburg) and Anita Hopes (Marburg).

Following persons supported us by giving "raven data": Dr. Anhut, K.-H.; Arno, W.; Bender, H.; Brauneis, W.; Diehl, O.; Dietz, H.; Dietz, M.; Dressler, B.; Eckstein, R.; Flehmig, B.; Prof.-Dr.-Ing. Friemann, H.; Henning, J.; Herbig, G.; Hettche, E.; Hogefeld, C.; Hormann, M.; Jobst, F.-J.; Jöstingmeier, H.; Jöstingmeier, H.; Korn, M.; Dr. Kreuziger, J.; Lucan, V.; Menning, K.; Norgall, A.; Reifenberg, A.; Reubert, H.; Schäfer, F.; Schindler, W.; Schmidt, D; Schneider, G.; Seum, Siebold, D.; U.; Stübing, S.; Trieschmann, M.; Veit, W.; Weisenborn; Wissner, H.-E.  Thank you very much to them and everybody who is missing in this list.

 

References

Bauer, H.-G. & P. Berthold (1997): Die Brutvögel Mitteleuropas, Bestand und Gefährdung. 2. durchges. Aufl., Aula-Verlag, Wiesbaden.

Berck, K.-H. (1997): Kolkrabe Corvus corax - Artkapitel in: Avifauna von Hessen, Frankfurt.

Bezzel, E. (1993): Kompendium der Vögel Mitteleuropas- Passeres, Singvögel. 766 Seiten, Aula Verlag, Wiesbaden.

Brauneis,W. (1991): Die Wiederbesiedlung des nordhessischen Raumes durch den Kolkraben (Corvus corax), Metelener Schriftenreihe für Naturschutz, Band 2, S.37-40,

Chadwick, D.H. (1999): Ravens - Legendary Bird Brains. - National Geographic, January 1999, S.100-115.

Dachverband Deutscher Avifaunisten /Hrsg.), Schriftenreihe des DDA 12, Bonn.

Deutscher Avifaunisten (DDA), 6, Bonn.

Havelka & Ruge (1988): Die Verfolgung der Rabenvögel (Corvidae) in Baden-Württemberg - Beih. Veröff. Naturschutz Landschaftspflege Bad.-Württ. 53, S.135-160, Karlsruhe.

Heinrich, B. (1989): Ravens in Winter. - Summit Books, 379 S., New York.

Jedrzejewska, B. & Jedrzejewski, W. (1998): Predation in Vertebrate Communities - The Bialowieza Primeveal Forest as a Case Study. - 449 S., Springer-Verlag, Berlin Heidelberg.

Glutz von Blotzheim, U.N. & K.M. Bauer (1993): Handbuch der Vögel Mitteleuropas - Passeriformes, Teil 4, S. 1947 - 2022, Wiesbaden

Lo Liu-chih (1997) Bruterfolg als Funktion von Ökosystemtyp, Flächennutzung und Konkurrenz bei Corvus corax - Dissertation an der Universität des Saarlandes, Saarbrücken.

Mech, L.D. (1995): The Wolf. - 8. Aufl., 384 S., University of Minnesota Press, Minneapolis.

Niethammer, G. (1963): Der Kolkrabe in Mitteleuropa einst und jetzt - Vogelring 31, S.49-54.

Promberger, C. (1992): Wölfe und Scavenger. - Diplomarbeit am Fachbereich Wildbiologie, 54 S., Forstwissenschaftliche Fakultät der Ludwig-Maximilians-Universität München.

Rheinwald, G. (1982): Brutvogelatlas der Bundesrepublik Deutschland - Kartierung 1980. Schriftenreihe des Dachverband

Rheinwald. G. (1993): Atlas der Verbreitung und Häufigkeit der Brutvögel Deutschlands - Kartierung um 1985. Schriftenreihe des Dachverband

Selva, N. (1999): Scavenging on Ungulate Carcasses, Dissertation in Vorbereitung, Mammal Research Institute, Polish Academy of Science, Bialowieza.

 

Further links to ravens:

Further general links: 1, 2,  pictures  Tales and myths: tales in North America, ravens in myths