Corvids

Corvids
Green jay ( Cyanocorax yncas )
Systematics
Subclass : New-jawed birds (Neognathae) Order : Passerines (Passeriformes) without rank: Eupasseres Subordination : Songbirds (passeri) Superfamily : Corvoidea Family : Corvids
Scientific name
Corvidae
Vigors , 1825

The crows - in the bird customer (or Ornithology ) often (after zoological nomenclature , latin ) corvidae or (in the majority, merely with Germanised ending) Corvids called - are a bird family of the order of perching birds (Passeriformes). They include around 120 living species in 25 genera. Corvids are medium to very large songbirds with mostly strong beak and robust physique, which have colonized a large number of different habitats in the course of their development history and are distributed worldwide with the exception of southern South America and Antarctica.

Corvids are very diverse in their diet and eat - depending on availability - fruits, seeds, insects, mollusks, smaller vertebrates or carrion , most of which is taken up on the ground. Almost all species build supplies in which they hide excess food and keep it for later. Corvids show strong social behavior and in comparison with almost all other birds above average high cognitive abilities. Some species, especially the ravens and crows , are pronounced cultural followers and have successfully established themselves in human-made habitats. The intelligence and linguistic talent of the corvids, but also their quality as carrion and crop eater, led to an ambivalent role in many cultures around the world: on the one hand they were assumed to be wisdom, biblical age and shrewdness, on the other hand they were persecuted as doers and pests .

features

Physique and Physiology

The largest raven bird next to one of the smallest: common raven ( Corvus corax ) and black jay ( Perisoreus canadensis ) in size comparison (drawing by Louis Agassiz )

Corvids are usually very sturdy and are among the larger of the songbirds. However, within the family there is a wide variety of shapes and sizes. The smallest Rabenvogel is approximately 40 g in weight and 20-23 cm Zwerghäher ( Cyanolyca nanus ), the two main representatives of the thick-billed raven ( Corvus crassirostris ) and Raven ( Corvus Corax ), each having a length between 60 and 70 cm can and have been determined for a body weight of 1.5 kg. Both species are therefore not only the largest in their family, but also the largest passerine birds of all. A pronounced gender dimorphism in size does not exist in any member of the family. Females of a species are usually slightly smaller than males, but there is always an overlap between female and male body measurements. Corvids have strong legs with long bones . Species that move primarily on the ground tend to have longer legs than predominant tree dwellers. The front of their legs is - except for the mountain crows ( Pyrrhocorax ) - paneled, that is, covered with wide, rectangular horn scales; the back, on the other hand, has a smooth surface.

The legs of a hooded crow ( Corvus cornix ) with characteristic paneling

In many types of the family, the nodding membranes of the eyes or the iris are noticeably brightly colored and are used in social behavior for communication, for example to express aggression. The beaks of the individual raven bird species have a wide variety of shapes. Some representatives such as the Saxaul jay ( Podoces ) or the Alpine crow ( Pyrrhocorax pyrrhocorax ) have long, slender and curved beaks with which they poke the ground for insects. The frugivorous dangling star ( Dendrocitta ), on the other hand, have relatively short and very powerful beaks. Among the ravens and crows, on the other hand, many species have developed very long and highly arched beaks, of which the ore raven is by far the largest. The shape of the beak can also differ significantly within a species: European blue jays ( Nucifraga caryocatactes ) that eat hazelnuts have shorter and stronger beaks than Siberian populations, which live almost exclusively on spruce seeds and have long, thin beaks. Most species have beaks, however, between these two extremes. They are strong, elongated, relatively straight and rather unspecialized. Their color ranges between blackish-gray tones and strong yellow and red tones. The ridge of the beak is slightly curved and ends in a hook point, similar to that of the strangler , but usually less pronounced. There is usually no difference in the color of the beak between young and adult birds. In the species in which such a difference occurs, the young birds have lighter beaks than the sexually mature adults, which then show dark gray beaks.

Skull of a carrion crow ( Corvus corone ): In the side view, the curvature of the front skull, the broad postorbital process above the eye socket and the large cranial space can be seen.

Adapted to their diet, the upper digestive tracts - that is, the beak, throat and neck - of many corvids are shaped in such a way that they enable the temporary storage of food. Pine jays, for example, have a sublingual , the real magpies ( Pica ) an antelingual throat pouch in which they collect nuts and seeds. The esophagus of the genera Gymnorhinus and Cyanolyca are highly expandable, so that they offer space for a large amount of seeds.

Due to the different eating habits within the family, the stomachs of the Corvidae species are very different from one another. Carnivores like the common raven and berry eaters like the mountain crows have typical soft-eater stomachs. Seed predation as the Siberian jay ( Perisoreus ) and omnivores such as the European crowing of the genus Corvus , however, feature Körnerfresser stomachs with strong muscles. Even within this last group, the shape of the stomach can vary widely. The jay ( Garrulus glandarius ), for example, has a large, rather weakly muscled stomach in adaptation to its low -protein diet. The closely related and sympathetic jay, on the other hand, has a very small, heavily muscled stomach that is used to digest hard, protein-rich pine seeds. The breeding spot is only developed in female corvids. The only exception are the nutcrackers, where both sexes take turns breeding.

The corvids also have a number of osteological features in common: The humerus has a single fossa . The front skull is clearly arched. Its lateral surfaces are delimited by simple zygomatic processes and broad postorbital processes ; the palate is wide split. Opposite the medium-sized ethmoid is a large tear bone . Both have grown along the length of the frontal bone and thus form a long, gap-like foramen . The forehead and the septum between the eye sockets are very ossified. The cranial space and thus the brain mass is larger in relation to the rest of the body dimensions than in most other birds. It also surpasses many other passerine birds , although the species of this order already have very large brains. The corvids' cerebellum halves are the largest of any living bird.

plumage

As with the wandering tree elster ( Dendrocitta vagabunda ), the nostrils of most corvids are covered by dense tufts of feathers

Corvids have a few things in common when it comes to their plumage. The entire body with the exception of the beak and legs from the running bone down is feathered. Only in some species of ravens and crows, the acacia jay ( Zavattariornis stresemanni ) and the yellow-billed elster ( Pica nuttali ) are also small parts of the face feathered. A typical feature of the family are the nasal feathers that cover the upper beak. They are differently pronounced among the species of Corvidae and often within a genus. 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. The partial or complete absence of nasal feathers in some species is usually due to an adaptation to food acquisition. If the beak has to be stuck deep into conifer cones, the feathers would otherwise be disheveled or damaged. Corvids also have moderately developed beak bristles .

A flying long-tailed jay ( Cyanocorax formosa ). It shows the typical large plumage structure of the family with a rounded hand wing made up of ten hand wings and a remicle as well as twelve control springs .

The family's tail and wing feathers are very stiff. As a rule, all species have moderately rounded, deeply fingered wings with ten hand wings . The outermost wing spring is slightly receded, some groups also have a remicle in addition to the actual hand wings . Twelve rudder feathers are common for the tail of corvids . Exceptions are the Piapia ( Ptilostomus afer ) and the Rakettschwanzelstern ( Crypsirina ) with only ten control springs. The tail is usually rather short and rounded in species that inhabit open habitats; in the case of tree and scrub dwellers, however, it can be very long and staggered. The middle pair of control feathers then usually clearly exceeds the remaining tail feathers.

Although the jay ( Garrulus glandarius ) is generally inconspicuous in color, it has a distinctive plumage characteristic with its blue arm and hand covers. Such patterns often serve as a social signal or camouflage in corvids of the temperate latitudes by dissolving the outlines of a bird in the thicket.

Corvids of dense tropical forests also differ in their plumage from the types of open and semi-open landscapes in temperate latitudes. The former are often very brightly colored in red, green and blue tones, while the plumage of the latter is rather inconspicuous gray, brown or black. Many species of the moderate latitudes nevertheless have smaller plumage areas with conspicuous patterns, which are ascribed a signal effect. They can often only be seen up close or in sunlight, or they look like rays of light falling through the branches because the rest of the bird's body merges with the environment. In addition to their social function, they often also have a camouflaging effect. Examples of such feathers drawings about the Jay ( Garrulus glandarius ) with bright blue wing badge or Unglückshäher ( Perisoreus infaustus ) with reddish feathers and wings bases. The New World jays represent a special case in terms of coloration . Almost all of them have larger or smaller, intensely colored blue components in their plumage. This is probably an original feature of their common ancestor, which the species in boreal and temperate zones have not lost since then.

Males and females show no, juvenile and adult birds mostly only slight differences in plumage, so the juvenile plumage in all corvids is softer, looser and greyish than the old plumage. In some species, however, young and adult birds are significantly different. In the case of the Yucatan blue ( Cyanocorax yucatanicus ), the white of the youth's dress changes to a deep black. The blue-tailed jay ( Perisoreus canadensis ) only receives its light-colored facial feathering when it reaches sexual maturity and before that it has a uniformly dark brown head plumage. The old crow ( Corvus tristis ), a crow that is conspicuously white and gray as a young bird, loses its bright feathers almost completely with age and then appears uniformly black. Unlike many other songbird families, the belly plumage of young birds is free of speckles; the only exception to this is the crested jay ( Platylophus galericulatus ), but its systematic position is controversial.

Locomotion

Their long legs enable the rook (Corvus frugilegus) to move forward. Corvids with shorter legs or less weight, on the other hand, move on the ground mainly by hopping.

Corvids move frequently in the air as well as in the branches and on the ground. However, there is a wide range of locomotion areas and species among the genera and species. The very terrestrial Saxaul jays ( Podoces ) are skilful and fast runners who move skillfully on the ground and cover long distances mostly on foot. Many species of the Southeast Asian tropics, on the other hand, move mainly in the undergrowth and branches and appear rather clumsy due to their shorter legs on the ground, but still often come down from tree tops and bushes to look for food. Smaller species often or always hop, larger corvids stride more frequently; their gait usually appears military. Typical for Corvids is the asynchronous triple step, slightly rotated from the body axis, which they adopt when they want to move faster across the ground. The use of this so-called “ polka step” is in contrast to the locomotion of many other bipedal animals, which hop when they want to move slowly and run when they want to move quickly.

The species of the family fly purposefully in the air with deliberate, powerful flaps of their wings. In the case of long-tailed corvids with relatively short wings, the flight is comparatively strenuous or undulating as with the dangling star . Especially larger species with long wings also sail on warm air currents or circling at great heights. In the case of flying corvids, the legs are usually drawn in, less often laid out. Despite their usually very economical flight style, not a few species are agile flyers and perform fictional figures in flight.

voice

Although they belong to the songbirds , the corvids do not have a particularly melodic song, such as the smaller songbirds use to defend their nesting site or for courtship . In return, they have a very broad repertoire of calls that become even more complex through nuance, contextualization or combination. In all kinds of families, they often sound croaky, hoarse and rough, but they can also take on an unexpectedly soft or chatty character. The repertoire of individual species is in the double-digit range and ranges from 14 known calls for the azure raven ( Cyanocorax caeruleus ) to 80 for the common raven . The range of calls of individual individuals is, however, smaller with the latter and is around 20 different vocalizations. For most tropical species, however, the breadth and complexity of the call spectrum is unknown. Calls are mostly used in very specific contexts, even if they differ from others only in nuances. Swedish populations of the bad luck bug , for example, have 14 different calls for security alone. They not only differentiate between owls and birds of prey , but also between individual danger situations and the respective defense strategy.

The cawing call of the pine jay ( Nucifraga columbiana ) is an example of the rather unmusical vocalizations often attributed to the corvids

Calls meant to signal fear, aggression, or despair are usually very harsh, high-pitched, or loud. Since these calls are most likely to be heard by the outside world, they are often considered typical in the literature. Alarm, dominance or intense begging calls are also rather croaking and simple in their basic structure. Conversely, vocalizations that accompany soothing or advertising gestures such as feeding the partner or moderate begging are softer and more delicate; they seem less harsh. In addition, corvids also have vocalizations that come close to a song. However, they do not seem to have any significant function in territorial or social behavior and are accordingly less pronounced than in the small, sparrow-like songbirds. These series of sounds, often referred to as subsong or whisper song in English, are comparatively quiet and unstructured, but still have a high musical quality. They mostly combine different vocal expressions from the repertoire of the respective type, which are used outside of their actual context. Corvids usually sing this way when they are outside of large groups, such as in flight or in a seat guard.

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Corvids are gifted voice imitators. Not only can you learn many different sounds and even human words, but you can also use them in a targeted manner. Here a common raven imitates the bark of dogs.

Corvids also weave in imitated sounds of other animals or other noises from their environment, especially in subsongs. Many types of the family are able to imitate such sounds in a deceptively real way and also use them in a targeted manner. For example, the jewelry kitta ( Urocissa ornata ) calls out like the Besrasperber ( Accipiter virgatus ) to warn of this bird of prey and to hate it . The ability to contextualize such sounds also have raven bird species that hardly show any acoustic mimicry in the wild : ravens and crows, raised by humans, learned to use phrases and words in their social context, for example as greetings. Imitation is made possible for the corvids by their highly developed speaking apparatus, especially their vocal cords; however, the original function of this mimicry is unclear. The overall very varied acoustic vocabulary of the corvids is probably a consequence of their complex social organization, which entails a high degree of communication.

Spreading and migrations

Distribution of the corvids. Green: natural distribution; yellow: (re) introduced; red: extinct before 1500; blue: extinct after 1500.

Corvids can be found almost everywhere in the world. Above all, southeast of the Himalayas to Southeast Asia, many genera are native to the more original representatives of the family, such as the Baumelstern ( Dendrocitta ) or the Kittas ( Urocissa ). Several genera such as the Garrulus jens, the blue star ( Cyanopica ) or the mountain crows ( Pyrrhocorax ) managed to colonize Eurasia and North Africa independently of one another. The bad luck jays ( Perisoreus ), the real magpies ( Pica ) and the nutcrackers ( Nucifraga ) also reached North America. The group of New World jars , whose representatives can be found from central Canada to northern Argentina, also live on both American continents . Saharan could with the Stresemann's Bushcrow ( Zavattariornis stresemanni ) and the piapia ( Ptilostomus afer ) two monotypic established genres.

East of the Wallace Line , with the exception of ravens and crows ( Corvus ), there are no corvids. This relatively young genus not only spread throughout the Palearctic , but also advanced as far as southern Africa and Australia, where corvids had not previously existed. They also settled the sub-Antarctic and even reached remote islands such as the Hawaiian archipelago and New Zealand . The genus Corvus is distributed almost worldwide today and is only absent in South America, where the blue ravens ( Cyanocorax ) occupy their ecological niche .

Seasonal migratory behavior is only shown by some corvid species in the northern hemisphere , while the species in the tropics and subtropics are mostly stationary or line birds . There are differences between sympatric species or within a species. For example, adult Northern European blue jays ( Nucifraga caryocatactes ) remain in their breeding grounds all year round. Their annual storage facilities not only enable them to hibernate safely, they also bind them to their breeding ground at the same time. However, there are often eruptive migratory movements of unpaired young birds, several thousand of which fly into the southwest of the continent due to a lack of food or nesting sites. The rook populations of northern latitudes, on the other hand, regularly move 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 . In addition to geographical hikes, some species also perform high-altitude hikes. Such migratory movements occur, for example, in the Alpine choughs ( Pyrrhocorax graculus ) in the European Alps , which descend into the warmer and human-inhabited valleys in winter.

habitat

Is considered Habitat specialist among crows: The Saxaulhäher ( Podoces panderi ) from the deserts of Central Asia

Few families of songbirds inhabit such diverse habitats as the corvids. In addition to their probably most pristine habitat, the dense tropical forests of Southeast Asia, corvids have also conquered open and semi-open landscapes in all climatic zones. The mountain crows ( Pyrrhocorax ), which today can only be found in mountains and on cliffs, were able to colonize the then vast steppe landscapes of Eurasia in the Pleistocene . This niche is now largely occupied by the ravens and crows ( Corvus ), whose jay-like ancestors probably still lived in the forests of Northern Europe. The acacia jays ( Zavattariornis stresemanni ) in the Ethiopian highlands and the Saxaul jays ( Podoces ) from the scree and sandy deserts of Central Asia have emancipated themselves even further from the family's originally arboreal way of life . They use trees or bushes almost exclusively for breeding and have become very undemanding in this regard. The same applies to species that, like the vulture raven ( Corvus albicollis ) or the jackdaw ( Coloeus monedula ), became cliff or cave breeders. A series of physiological and morphological adaptations went hand in hand with the conquest of habitats . The Gray Jay ( Perisoreus infaustus ) for example, is one of the smallest birds throughout the year in boreal endure coniferous forests. In order to maintain its body temperature, a bird of its size would actually have to consume 50% of its body weight per day in fat, for which it only has four to six hours available during the polar day . The titjay overcomes this challenge through hypothermia . As a result, the species can tolerate temperatures of up to 4.5 ° C.

Open and semi-open habitats play an important role for most corvids, also for cultural followers such as the American crow ( Corvus brachyrhynchos )

The greatest diversity of habitats within a genus is found among the ravens and crows. While the habitats of other genera are usually very homogeneous, the ravens and crows gather jungle and mountain dwellers as well as rock, cave and tree breeders. The fact that the genus was able to colonize such diverse habitats as the arctic tundra or the Indonesian rainforests in a short time is attributed less to a specific adaptation than to the lack of specialization of this group. 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. To a lesser extent, this also applies to other corvids such as the real magpies ( Pica ) or some New World jays . 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.

Way of life

nutrition

The New Caledonian straight-billed crow ( Corvus moneduloides ) uses bent petioles under the tree bark to fish for longhorn beetle larvae and has thus developed one of the most sophisticated techniques for obtaining food

Almost all corvids have a very diverse range of food, which includes both animal and vegetable food. Almost all species of the family have insects, fruits, seeds, eggs, carrion and small vertebrates in the diet. Not all species are equally omnivorous, however . The naked jay ( Gymnorhinus cyanocephalus ) feeds mainly on the seeds of a few species of pine from western North America and has a close ecological relationship with them. The common raven , on the other hand, is a pronounced carnivore and scavenger, while the Saxaul jay and mountain crows feed largely on insects. The proportions of certain feed sources in the diet can also fluctuate regionally and seasonally. Corvids are very opportunistic and usually stick to the available or most abundant food when foraging. In addition, they are very curious and test every unknown object for its usability. It so happens, for example, that in the stomach of rooks ( Corvus frugilegus ) often find rubber rings that were held by the birds because of their consistency for meat. At the same time, this behavior led to the fact that corvids were long regarded as indiscriminate omnivores in western folk beliefs and in science, and they can survive even with very nutrient-poor food. In fact, even such versatile food processors as the carrion crow ( Corvus corone ) are dependent on a balanced diet with appropriate nutrient content.

As diverse as the range of food available within the family are the techniques that are used to acquire food. Nuts, insects or other pieces of food are picked up from the ground or leaves or plucked from branches. Depending on the shape of the beak, larvae are poked or dug out of the ground. Vertebrates are caught using their feet and killed with targeted beak blows. The acquisition of food can take place both alone and in groups, whereby an eating corvid quickly attracts conspecifics. So-called circles are a specialty of the Corvids and, independently of that, of the starlings. The closed beak is inserted into an opening and then an attempt is made to open it with force in order to widen the opening and to get to any food stored in it. Corvids are also very resourceful when it comes to finding unusual or supposedly inaccessible food. Hooded crows ( Corvus cornix ) in Finland 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. Green jay ( Cyanocorax luxuosa ) were observed to successfully poke for insects with the help of a branch under the bark of a dead tree and then to eat them. The New Caledonian straight-billed crow ( Corvus moneduloides ) is known for a similar behavior . Kleptoparasitism is a common behavior observed in corvids. American crows ( Corvus brachyrhynchos ) wait for gray squirrels to fetch food from a garbage can inaccessible to the crows and then chase it away from them. Not only smaller animals are affected by loot by corvids. Corvids are extremely vigorous and, in flocks, often drive larger birds of prey from carcasses or distract them collectively in order to steal lumps of prey from them. The common raven is also likely to be responsible for the fact that the wolves that live with them hunt in packs: the food yield in relation to the hunting effort is best for a single wolf. However, a flock of common ravens can steal more than half of its prey from a wolf without the wolf being able to defend itself effectively. The success of the ravens only decreases with increasing pack size.

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New world jays like the blue jay ( Cyanocitta cristata ) can chop up nuts and seeds particularly easily with their special jaw joint

Pieces of food are mainly transported and processed with the beak. Often, however, the feet are used to hold a piece of food in place when the bird hits it with its beak. The jaw joint of the new world jay makes it easier for them to break open nuts and similar objects by supporting the chiselling function of the beak even more. Other species of corvid, such as the pine jay ( Nucifraga columbiana ), have a straight, pointed beak, which is particularly suitable for hammering conifer seeds. Sticky or greasy pieces of food are usually dipped into the water before consumption, probably to prevent soiling of the plumage or beak. All corvids have an instinct to hide, which prompts them to hide excess food in order to store it for later, even if they are not dependent on such hiding places. The food is usually buried, but perishable food is hidden on the surface of the earth. The Siberian jay ( Perisoreus ) sticking her found food with saliva in bark furrows. Even very hungry corvids clear excess food aside before they begin to eat last. The food is not hidden in a central location, but distributed over several stores, which often only contain a single piece of food. The birds can still find hiding spots months later and even under thick blankets of snow. In contrast to hoarding mammals, the sense of smell does not seem to play a role, the birds rely on their spatial memory. When corvids observe each other while hiding, the observer usually clears out the hiding places of the observed. The robbed person then learns from this experience, even if he has not noticed the clearing himself, and from then on no longer hides his food when someone of the same species is nearby. Even if most of the hiding spots are then cleared out, a certain amount of the food always remains in the ground. Some corvids thus contribute significantly to the spread of many tree species.

Social and territorial behavior

A pair of glossy crows ( Corvus splendens ) taking care of each other's plumage

The corvids' social behavior is very pronounced. All species form smaller or larger swarms that sleep, eat or migrate together . The degree of socialization is very different within the family. While rooks form large sleeping and breeding colonies and naked jays live in flocks of an average of 250 birds, adult common ravens generally move in pairs. However, unmated young birds also form loose associations looking for food with one another. Life in flocks offers corvids advantages when looking for food, defending themselves against predators and occasionally also in brood care.

Hierarchies exist within the communities, but they are not necessarily transitive : bird A can dominate over bird B and bird B over bird C without bird A dominating over bird C. The dominance of a bird can also be limited to a small area (such as a breeding or roosting place), while another bird sets the tone beyond the boundaries of the area. The position within these hierarchies determines the assertiveness of the birds against conspecifics when it comes to the fight for food or nesting places. The recognition of such hierarchies also serves to resolve conflicts in the swarm relatively non-violently. In addition, there are also friendly relationships between individuals and caring behavior towards sick or injured conspecifics.

Brood partners develop a special relationship to one another, which is reflected in reduced individual distance and mutual grooming. Together they not only occupy nesting sites, but also defend them against conspecifics and other birds. The defended territories can be very large, like some ravens, or very small, like the rook.

Reproduction and breeding

Two titjays feed their brood

Corvids tend to be monogamous and form lifelong breeding pairs. Additional copulations can occasionally occur, but only the partner is always looked after and, if the relationship has lasted for more than a year, not abandoned. Only the disappearance of a partner, illness-related loss or death usually lead to the remaining partner being mated again. The effect of this lifelong fidelity is an increasing breeding success: the longer couples stay together, the higher the excursion rates of their clutches.

The breeding systems differ significantly within the family, the individual genera and even between populations of the same species. A rough distinction is made between three different breeding systems: brood rearing only by the pair of parents, the provision of non-breeding conspecifics as well as the independence of last year's offspring, which is delayed by a few months or years, which is viewed as a transitional form. The sole rearing by the parents is usually associated with strong territoriality, but brood helpers are more likely to be found among colony breeders. Breeding helper birds benefit from their activity through greater experience, which leads to greater success with their own broods later on. Their work can go beyond just feeding or affect other areas, such as defending the territory or building nests. The number of available breeding territories and the productivity of surrounding food sources may be decisive for a breeding system. Hatchers can do their job for several years before they breed themselves. Often they then occupy territories in the vicinity. This is especially true when it comes to offspring of the original breeding pair.

Predators and parasites

Larger corvids, in particular, have hardly any definite predators. The common raven, the largest songbird, is only captured by a few animals, such as peregrine falcons, but conversely, it is also able to kill them. Where corvids appear in flocks, they often drive away much larger raptors , but also other corvid species. Smaller corvids, on the other hand, often fall victim to hawks and sparrows ( Accipiter ) and other specialized bird hunters. 

Taxonomy and history of development

→ Main article : Systematics of corvids

External system

The corvids are a rather original family of songbirds. Her sister family are in all likelihood the Strangler (Lanidae). The birds of paradise are also more closely related to the corvids. The corvids probably developed in Southeast Asia, where a wide variety of genera can still be found today. The oldest known representative of the family is Miocorvus larteti from the middle Miocene of France, followed by Miopica paradoxa from the late Miocene of Ukraine and Miocitta galbreathi from the upper Miocene of Colorado .

Internal system

Internal systematics of the living corvids according to Ericson et al . 2005 Corvidae   ( Corvidae )   Mountain Crows ( Pyrrhocorax )      Dangling star ( Dendrocitta )      Rocket Tail Star ( Crypsirina )      Mourning Star ( Platysmurus )      Ladder tail star ( Temnurus )      Green star ( Cissa )      Kittas ( Urocissa )      Blue star ( Cyanopica )      Unglückshäher ( Perisoreus )   " New World "   Jackdaw ( Cyanolyca )      Blue raven ( Cyanocorax )      Naked jay ( Gymnorhinus )      Bush jay ( Aphelocoma )      Blue jay ( cyanocitta )      Real Magpies ( Pica )      Acacia jay ( Zavattariornis )      Piapias ( Ptilostomus )      Saxaul jay ( Podoces )      Garrulus      Nutcracker ( Nucifraga )      Ravens and Crows ( Corvus )      Jackdaws ( Coloeus )

The DNA of almost all corvidae genera was examined in a study published in 2005 under the leadership of Per Ericson. The monophyly of the examined group and its rough lines of development emerged:

• Mountain crows and Southeast Asian magpies: This monophyletic group separated from the ancestors of the other corvids early and originated in Southeast Asia. The Southeast Asian dangling star ( Dendrocitta ), mourning star ( Platysmurus ), ladder tail star ( Temnurus ) and rocket tail star ( Crypsirina ) inhabit the Indian subcontinent, Southeast Asia and Indonesia. The mountain crows were previously considered to be close relatives of the ravens and crows, but are much more original and form the sister group of the Southeast Asian magpies or even all of the rest of the corvids. From there they spread throughout Eurasia in the Pleistocene .
• Green star and kittas: The green star ( Cissa ) and the kittas ( Urocissa ) also have their origin and distribution in the Southeast Asian region and inhabit a similar habitat as the Southeast Asian magpies. They split off from the rest of the corvids a little later than the first group.
• Blue magpies and Unglückshäher: The external and ecologically very different blue magpies ( Cyanopica ) and Unglückshäher ( Perisoreus ) originate from a common ancestor. While the blue jays inhabit boreal and montane coniferous forests, blue stars can be found in Mediterranean, semi-open park landscapes. The distribution area of ​​the blue jay stretches across northern Eurasia and North America, while that of the blue star falls into two relic areas on the Iberian Peninsula and East Asia . Fossil finds indicate that this genus was more widespread in earlier times.
• New world jay: The new world jay includes all those species of corvids that occur exclusively on the American double continent. They came into being after their common ancestor reached North America over a land bridge 8-10 million years ago. Their jaw joint allows them to hammer with their beak open and anatomically distinguishes them from all other corvids.
• Real magpies and dryland jays: The real magpies ( pica ) are birds of the temperate parkland and distributed in the Holarctic. They are close to the Akazienhähern ( Zavattariornis ) Piapias ( Ptilostomus ) and Saxaulhähern ( Podoces ) is used, all dry inhabit in the northern half of Africa and Central Asia to desert-like habitats.
• Ravens, crows, jays and nutcrackers: the jays of the genus Garrulus , the nutcrackers ( Nucifraga ) and the ravens and crows ( Corvus ) represent a comparatively young group . Garrulus and the nutcrackers each specialize in certain seeds and nuts as food. The closely related ravens and crows, on the other hand, are an unspecialized and ecologically very successful group of birds that colonized a variety of habitats and were the first among the corvids to reach southern Africa, Australia and remote oceanic islands.

The membership of the crested jay ( Platylophus galericulatus ) among the corvids has long been disputed. According to many recent studies, osteological characteristics and behavioral findings suggest that the species is not a corvid. However, detailed investigations of their DNA are still pending.

Word origin

Almost all species of the Corvidae family have the additions “crow”, “jay”, “raven” or “magpie” in their common names . These names originally referred to bird species from the German-speaking area and were later transferred to other species in the family. "Crow" comes from the Old High German krāha , which is an onomatopoeic name for the smaller species of the genus Corvus . The same is true for "Raven", which from the Old High German Hraban comes (croaker). The Old High German "hehara" is also an onomatopoeic name that originally referred to the jay and its reputation. "Elster" is derived from the Old High German "agalstra", the meaning of which is unclear.

Mythology and Reputation

Probably the earliest depiction of a raven in the Lascaux cave

Among the corvids, the ravens and crows ( Corvus ), but also the bad jays ( Perisoreus ) and the magpie ( Pica pica ) experienced a cultural reception . The human view of corvids has always been ambivalent. On the one hand, many species were always present in the human environment, but their role in human life was never as central as that of farm animals or predators. Corvids were never domesticated because they did not produce any particular yield compared to chickens or geese and also had a reputation for not tasting good. References to corvids in systematized mythologies are correspondingly rare; they often appear only marginally and anecdotally, even if they sometimes play a key role, for example as the creator of the world among Siberian and Indian peoples, who soon loses his power. In many cultures ravens were considered omens animals regarded the Ravens as was in the mythology of ancient Rome as the most important bird for the auspices of the augurs . Corvids were seen as harbingers of doom primarily because of their affinity for carrion and their often massive appearance after battles, where they ate from the corpses of the fallen. The esoteric often alleged closeness to death is also due to the increased occurrence of ravens at places of execution , since the corpses of those who were executed usually got stuck until they a. were eaten by animals. Only the bones were then buried. But also smaller species like the bad luck tots ( Perisoreus ) were said to bring bad luck to find their nests.

While corvids were seen as welcome cleaners in the cities and villages during the European Middle Ages, they lost this reputation with the modern age, when the cities became increasingly cleaner and the birds lost their old function. Instead, they came to the fore as agricultural and game pests, which were subsequently massively persecuted. Magpies, ravens and crows were hunted down and shot down in many parts of the world, which is why the common raven became extinct in Central Europe and eastern North America. It was not until the end of the 20th century that the pressure of persecution eased in many regions, so that corvids could make their home there again.

swell

literature

• Anke Adrian: Are there any signs of friendship-like relationships in jackdaws? Bielefeld University, Bielefeld 2006.
• Dean Amadon: The Genera of Corvidae and their Relationships. In: American Museum Novitates 1251, January 1944, pp. 1–21.
• Tony Angell: Ravens, Crows, Magpies and Jays . University of Washington Press , Seattle and London 1978, ISBN 0-295-95589-9 .
• M. Antiqur Rahman Ansari: A Revision of the Brüelia (Mallophaga) Species Infesting the Corvidae. Part II. In: Bulletin of the British Museum (Natural History) 5 (4), June 1957, pp. 6-182.
• Leslie Brown, Emil K. Urban , Kenneth B. Newman (Eds.): The Birds of Africa. Volume 6: Picathartes to Oxpeckers. Academic Press, 2000, ISBN 0-12-137301-0 .
• Stanley Cramp , CM Perrins: Handbook of the Birds of Europe, the Middle East, and North Africa: The Birds of the Western Palearctic. Volume VIII: Crows to Finches. Oxford University Press, Hong Kong 1994, ISBN 0-19-854679-3 .
• 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 0-565-00979-6 .
• Michael Griesser: Mobbing Calls Signal Predator Category in a Kin Group-living Bird Species . In: Proceedings of the Royal Society B 276 (1669), August 2009. doi: 10.1098 / rspb.2009.0551 , pp. 2887-2892.
• G. Hayes, RM Alexander: The Hopping Gaits of Crows (Corvidae) and Other Bipeds . In: Journal of Zoology 200 (2), 1983. doi: 10.1111 / j.1469-7998.1983.tb05784.x , pp. 205-213.
• Wilhelm Heizmann , Hans Reichstein: Corvids. In: Reallexikon der Germanischen Altertumskunde. 2nd Edition. Volume 24 (2003), pp. 42-45.
• 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 0-19-553996-6 .
• Joseph 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 978-84-96553-50-7 .
• 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 .
• Albrecht Manegold : Morphological characters of the tongue skeleton reveal phylogenetic relationships within the Corvidae (Oscines, Passeriformes). In: Emu. 108, 2008. doi: 10.1071 / mu08022 , 321-330.
• 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. (on-line)
• Roger D. Price, Ronald A. Hellenthal: Taxonomy of Philopterus (Phthiraptera: Philopteridae) from the Corvidae (Passeriformes), with Descriptions of Nine New Species. In: Annals of the Entomological Society of America 91 (6), November 1998, pp. 782-799.
• Chaminda P. Ratnayake, Eben Goodale, Sarath W. Kotagama: Two sympatric species of passerine birds imitate the same raptor calls in alarm contexts . In: Natural Sciences. 97 (1), 2010. doi: 10.1007 / s00114-009-0617-7 , pp. 102-108.
• Boria Sax: Crow . Reaction Books, 2003; ISBN 1-86189-194-6 .

Web links

Commons : Corvids  - Album with pictures, videos and audio files

• Duden online. Bibliographisches Institut GmbH, www.duden.de, 2011.

Individual evidence

1. ↑ del Hoyo et al. 2009 , pp. 510-512.
2. ↑ Marzluff & Angell 2005 , p. 50.
3. ↑ Madge & Burn 1994 , pp. 2-60.
4. ↑ Goodwin 1986 , pp. 17-18.
5. ↑ ^{a b} del Hoyo et al. 2009 , p. 514.
6. ↑ Glutz von Blotzheim & Bauer 1993 , p. 1376.
7. ↑ Higgins et al. 2006 , p. 672.
8. ↑ Angell 1978 , p. 82.
9. ↑ Marzluff & Angell 2005 , p. 43.
10. ↑ ^{a b c} Cramp & Simmons 1994 , p. 5.
11. ↑ Brown et al. 2000 , p. 531.
12. ↑ Glutz von Blotzheim & Bauer 1993 , p. 1375.
13. ↑ Goodwin 1986 , p. 17.
14. ↑ Goodwin 1986 , pp. 18-20.
15. ↑ Goodwin 1986 , p. 221.
16. ↑ Madge & Burn 1994 , pp. 48-49.
17. ↑ Goodwin 1986 , p. 50.
18. ↑ Hayes & Alexander 1983 , p. 205.
19. ↑ del Hoyo et al. 2009 , pp. 526-529.
20. ↑ Griesser 2009 , pp. 2889–2892.
21. ↑ Goodwin 1986 , pp. 51-52.
22. ↑ Ratnayake et al. 2010 , p. 105.
23. ↑ Marzluff & Angell 2005 , p. 208.
24. ↑ del Hoyo et al. 2009 , pp. 528-533.
25. ↑ ^{a b} del Hoyo et al. 2009 , pp. 494-510.
26. ↑ del Hoyo et al. 2009 , pp. 552-554.
27. ↑ del Hoyo et al. 2009 , pp. 514-515.
28. ↑ del Hoyo et al. 2009 , pp. 514-516.
29. ↑ Glutz von Blotzheim & Bauer 1993 , p. 1817.
30. ↑ ^{a b c} Goodwin 1986 , pp. 23-27.
31. ↑ del Hoyo et al. 2009 , p. 531.
32. ↑ ^{a b} del Hoyo et al. 2009 , p. 541.
33. ↑ Goodwin 1986 , pp. 32-33.
34. ^ Adrian 2006 , pp. 81-82.
35. ↑ ^{a b} Goodwin 1986 , pp. 36-37.
36. ↑ del Hoyo et al. 2009 , p. 545.
37. ↑ del Hoyo et al. 2009 , pp. 545-548.
38. ↑ Goodwin 1986 , p. 55.
39. ^ Jønsson & Fjeldså 2006 , p. 152.
40. ↑ del Hoyo et al. 2009 , p. 494.
41. ↑ ^{a b} Ericson et al. 2005 , p. 232.
42. ↑ del Hoyo et al. 2009 , p. 495.
43. ↑ ^{a b} del Hoyo et al. 2009 , p. 505.
44. ↑ del Hoyo et al. 2009 , p. 504.
45. ↑ del Hoyo et al. 2009 , pp. 515-516.
46. ↑ del Hoyo et al. , P. 566.
47. ↑ Manegold 2008 , p. 321.
48. ↑ ^{a b} Duden 2011 . Retrieved September 30, 2011.
49. ↑ ^{a b} del Hoyo et al. 2009 , pp. 554-559.