Corvus corax

Corvus corax

The Common raven (Corvus corax Linnaeus, 1758) is a passerine bird belonging to the Corvidae family.

Systematics –
From the systematic point of view it belongs to the Eukaryota Domain, Animalia Kingdom, Subarign Eumetazoa, Superphylum Deuterostomia, Phylum Chordata, Subphylum Vertebrata, Infraphylum Gnathostomata, Superclass Tetrapoda, Classe Aves, Subclass Neornithes, Superorder Neognamigliaesiform, Suborder Corfineform, Suborder Corfine Corvoidea, Corvidae Family and therefore to the Corvus Genus and to the C. corax Species.
Of this species, most authors recognize eleven subspecies, with different ranges and characteristics:
– Corvus corax principalis Ridgway, 1887 – characterized by a massive build and large beak, very bright plumage and well developed throat beards, spread from Alaska to Greenland and south to Oregon and northwestern Georgia (through the Appalachians;
– Corvus corax sinuatus Wagler, 1829 – small in size and with a small and relatively thin beak, spread from British Columbia to Nicaragua through the Great Plains, the Rocky Mountains, the Great Basin and Mexico;
– Corvus corax clarionensis Rothschild & Hartert, 1902 – widespread in California and Baja California (as well as on the island of Clarión), as far east as the Mojave desert;
– Corvus corax varius Brünnich, 1764 – intermediate size between the nominal and principalis subspecies, characterized by less shiny plumage and a characteristic ring of whitish feathers around the base of the beak, widespread in Iceland and the Faeroe Islands (where it was also widespread a geographic variant, the piebald crow, currently extinct [52]);
– Corvus corax corax Linnaeus, 1758 – the nominal subspecies, characterized by a short and stocky beak, rather arched, spread from the British Isles to the Enisej through Fennoscandia, western, central and eastern Europe, European Russia and Siberia;
– Corvus corax hispanus Hartert & Kleinschmidt, 1901 – widespread in the Iberian Peninsula, in Italy (including Sicily and Sardinia), in Corsica and in the Balearics;
– Corvus corax laurencei Hume, 1873 – spread from eastern Greece to western Turkestan and north-western India, through Cyprus, the Middle East and Central Asia;
– Corvus corax tingitanus Irby, 1874 – characterized by small dimensions, slightly hinted throat beards and greasy-looking plumage, with brown shades on the head and body more evident in old age, short but robust beak with an arched upper margin, spread along the band coast of North Africa from north-central Morocco to Egypt;
– Corvus corax canariensis Hartert & Kleinschmidt, 1901 – endemic to the Canary Islands;
– Corvus corax tibetanus Hodgson, 1849 – characterized by large dimensions (although the beak is not as large in proportion to the body as in the subspecies principalis), by the very bright plumage with greyish shades at the base of the neck and by the very pronounced gular beards, widespread from the Pamir and from Tian Shan to the Tibetan plateau and the northern foothills of the Himalayas;
– Corvus corax kamtschaticus Dybowski, 1883 – characterized by large size and large and strong beak, spread from central Siberia to Kamchatka, as far south as Manchuria and Mongolia, as well as Hokkaidō, the Kuril Islands, Sakhalin and the Commodore Islands.

Geographic Distribution and Habitat –
The Corvus corax, together with the Corvus crassirostris represents the largest representative of its family.
It is a bird native to Eurasia that exploited the land bridge of the Bering Strait formed during the Pleistocene ice ages to colonize North America: it is therefore one of the few animals (among others there are for example the elk, wolf and brown bear) to be present on both continents without having been imported there by man.
Due to this ancient origin, the raven, with all its subspecies, occupies the largest natural range among birds (over 10,000,000 km²).
It is a species widespread throughout Europe (Canary Islands, Iceland, Great Britain and Ireland included, while it is almost completely absent from central Europe), in central and northern Asia (as far south as Iran and northern India) , in North Africa, in North and Central America (with the exception of the southeastern United States) as far south as Nicaragua, as well as in many Pacific islands.
In Italy, the Common raven is quite rare, so much so that it appears among the species included in the Red Book of Animals of Italy: in fact, a total population of less than 15,000 units is recorded throughout the national territory, concentrated along the Alpine arc. in Sardinia, in the Gargano and along the Southern Apennines, but present roughly in all the rocky areas of the country.
Its habitat is that of tree-lined areas, with the presence in the surroundings of large open spaces where to look for food; it is also found along the coastal areas with the presence of rocky cliffs, where the animal feeds and nests. It is a very adaptable bird: it is also found in the icy areas of the Arctic Circle, in the arid and semi-desert areas of North Africa, up to the peaks of the Himalayas, where specimens of this species have been observed at 6,350 m of altitude on Mount Everest. It can be said that the only habitat that the raven avoids is the rainforest.

Description –
The Common raven is a bird with a total length of 52 – 64 cm, a wingspan of 117 – 135 cm, for an average weight that varies between 600 and 1,600 grams.
It has a robust conformation, completely shiny black with violet iridescences. The plumage is thick and tight. Depending on the subspecies, there may or may not be brown shades on the chest and neck, or whitish feathers arranged in a ring around the base of the beak. On the throat, in correspondence with the goiter, there are particular lanceolate and erectile feathers, called barbs, which the animal uses to communicate its state of mind.
The head is elongated, with dark brown eyes and a strong beak. The latter is rather long and slightly curved on the upper margin, with a sketch of a hook at the tip: the beak appears, however, shorter due to the bristly feathers that cover the proximal part, going beyond the edge of the beak and going to form a ring at its base, extending almost to the chin on the mandible.
The legs are bare from the tarsus down, where they are rough to the touch and covered on their front by a single row of rectangular scales: as well as all the other naked parts of the body they are blackish, sometimes with shades of flesh color in the vicinity. of the nail line. The latter are strong and hook-shaped, also shiny black. There are four toes, three facing forward and one facing back, ensuring the animal a firm grip on the grips and a good balance on the ground. The inside of the mouth is pink or bright red, with a pointed and rough reddish tongue.
The two sexes are similar, with the females being slightly smaller, while the young crow can be distinguished by the lack of purple iridescence and by its duller and brownish color. It can be distinguished from other corvids by its protruding neck due to its long wedge-shaped tail.
The young Common raven, very similar to the adults, even if smaller and with bluish-gray eyes instead of brown, gather in small groups composed on average of about fifteen individuals: they are extremely curious and show interest in any novelty that comes. their proposal (in particular for round and shiny objects), curiosities that will gradually lose with adulthood, to the point of becoming distinctly neophobic during old age.
The flight of the Corvus corax is characteristic: powerful, straight, with wide and slow beats, it also has the habit of gliding along like birds of prey.
In general, the southern subspecies, widespread in warmer areas, are generally smaller and slender than those found in colder environments.

Biology –
The Common raven reaches sexual maturity for both sexes around three years of age, even if behaviors that can be compared to courtship acts can be observed already starting from the second year of life, especially in the autumn and winter months: however, the females rarely lay the eggs before they are 4 years old.
The beginning of the reproductive phase is preceded by the characteristic nuptial flights during which the two spouses reach great heights and then quickly throw themselves downwards, overturning during the dive, and finally ascend in a spiral flight: during the whole operation, both the sexes emit a line that sounds like k-long k-long. At the end of these flights, secluded near the nest, the male imposes himself on the female in a position of dominance, upright on the legs and with ruffled plumage, while the latter is placed in a subordinate position, keeping the body horizontal and the head lowered: at this point the male bows spasmodically in front of his wife, holding the pendulous wings and ruffling the feathers of the head, while the white nictitating membrane of the eye is raised and lowered. If the female is receptive, then she mimics the posture of the male, keeping her tail folded sideways: this is where mating takes place.
Corvus corax has a reproductive period ranging from February to May, with one brood a year, during which it lays 4 – 6 (3 – 7) eggs. The eggs are blue-green in color with brown specks, and are laid in cavities or rocky shelves, more rarely on trees.
The duration of the hatching is 20 – 21 days and the stay in the nest of the chicks is 35 – 42 days.
The chicks are fed with large quantities of food regurgitated by the male, and as early as the first month of life they venture to the edges of the nest, although usually they do not fly before the completion of the second month of life: even once they are able to flying, they continue to be fed by both parents with pieces of meat, and they separate from it only after the sixth month of life. Many young crows stay with the adults until the next mating season.
The maximum age of this species is 15 – 16 years in the wild, while they can also go beyond this limit, exceeding 40 years of age and in some cases reaching 80 years in captivity.
Ravens are strictly monogamous animals: couples form at a young age and only dissolve with the death of one of the two spouses, although occasionally episodes of infidelity can be observed, with females receiving other males in the nest while males they are not present. The choice of the partner is made on the basis of the qualities of intelligence and ability to obtain food shown by the animal, rather than on the basis of tests of strength.
Once the couple is formed, the two components settle in a territory and start the construction of the nest: the latter, usually located in inaccessible places (rocky escarpments, very tall treetops, long-abandoned buildings), consists in a large cup up to one meter wide and about thirty centimeters deep, formed by a coarse scaffolding of branches lined inside with thinner twigs, mud and soft material such as fur, feathers and lichens. The couple always tends to use the same nest to raise the offspring, unless some event occurs that pushes the members to abandon it in search of other less accessible sites: every year it is remodeled with the addition of new twigs, so that the old nests reach quite impressive dimensions.
During the hatching of the eggs, the Common raven become even more circumspect than usual: before approaching the nest, the male stands at a certain distance to make sure that there are no strangers around, and only after having scrutinized the territory thoroughly dares to join his wife. However, if some predator (such as large birds of prey, both diurnal and nocturnal, or some canid or mustelid) still discovers the location of the nest and tries to steal its eggs or nestlings, it is often put to flight by the joint action of the two angry parents. , which can directly attack the intruder with blows of beak, or target him with stones that they drop from above. Predatory animals can also be attacked if they approach the nest even if only casually.

Ecological Role –
According to the traditional symbology, that of the Raven is the most nefarious among the species. The black plumage and the hoarse cry are the traits that have contributed to spreading the myth of this bird as a messenger of misfortunes in the service of evil forces. According to Greek mythology, the Raven, originally white, was a servant of the god Apollo. Punished for reporting bad news to the deity, he was condemned along with all his offspring to have feathers as dark as darkness. In reality, the mystery surrounding this species is probably due to its reserved and prudent nature: it prefers solitary life and harsh and inhospitable environments. Noted for its cunning, it is also capable of imitating a wide variety of sounds, even the human voice.
This bird normally leads a solitary or couple existence, but can unite in large groups if food availability is favorable.
The Common raven is a basically sedentary animal: young individuals can make displacements of a certain extent (200 km and more) in search of new environments in which to establish their own territory, while the populations residing in the less hospitable areas of the range of this species they can make small seasonal migrations in case of particularly inclement seasons from the climatic point of view, such as particularly hot summers or particularly harsh winters.
The ravens communicate with each other through a vast and complex range of sounds: so far the vocalizations of these animals have been classified into a series of categories that varies according to opinions from 15 to 34, most of which have the function of communicating with conspecifics. In addition to the sounds actually produced by the emission of air, Common ravens also communicate by noisily flapping their wings or beak, the latter action more observed in females than males. The posture of the body is instead indicative of submission (when horizontal) or dominance (when vertical) towards other specimens, or requests for grooming towards the spouse.
Among birds, ravens are those endowed with brains which are larger in proportion to the body: it is therefore not surprising that they show great intelligence. They are in fact able to learn what they are taught and even to develop in a completely autonomous way effective answers to the problems presented to them.
As far as nutrition is concerned, ravens are omnivorous and very opportunistic birds: their diet includes everything that the animal can find edible, therefore it can also vary quite markedly depending on latitude, season and availability. local food. For example, the resident crows in the Alaskan tundra are mainly carnivores that actively prey on local voles or feed on caribou and ptarmigan carcasses, while in other areas they may behave mainly as scavengers, feeding on carcasses and larvae of d ‘ insects associated with them. Whenever possible, the raven’s diet is also composed of a certain amount of material of plant origin, such as fruits, berries and grains. To locate food, the raven mainly uses sight and only secondarily the other senses.
Furthermore, the Corvus corax is one of the few species of corvids that actively preys on other animals, thus not behaving only as a simple scavenger: in addition to insects and other invertebrates, it also feeds on amphibians, reptiles, small mammals, birds (even of comparable to his own) and their eggs. In case of need, it does not disdain to rummage in the feces in search of coprophagous insects and undigested portions of food while in poorly populated areas or in those where it is not persecuted it frequents landfills, where it finds food at will and often settles in definitive way, even nesting there.
The raven usually stores excess food (in particular foods rich in fat, but also grains and bones) in hiding places, which the animal takes care to displace in various places, so that, if one of these pantries is discovered and plundered (which happens very regularly among crows), the animal does not remain dry-mouthed.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– C. Battisti, D. Taffon, F. Giucca, 2008. Atlas of nesting birds, Gangemi Editore, Rome.
– L. Svensson, K. Mullarney, D. Zetterstrom, 1999. Guide to the birds of Europe, North Africa and the Near East, Harper Collins Publisher, UK.