Northern raven, Western raven
The Common raven (Corvus corax) is a large all-black passerine bird. Found across the Northern Hemisphere, it is the most widely distributed of all corvids. It is one of the two largest corvids, alongside the Thick-billed raven, and is possibly the heaviest passerine bird. Common ravens have coexisted with humans for thousands of years and in some areas have been so numerous that people have regarded them as pests. In many cultures Common ravens have been revered as spiritual figures or godlike creatures.
The Common raven has a longish, strongly graduated tail, mostly black iridescent plumage, and a dark brown iris. The throat feathers are elongated and pointed and the bases of the neck feathers are pale brownish-grey. Juvenile plumage is similar but duller with a blue-grey iris. Apart from its greater size, the Common raven differs from its cousins, the crows, by having a larger and heavier black beak, shaggy feathers around the throat and above the beak, and a wedge-shaped tail. Flying ravens are distinguished from crows by their tail shape, larger wing area, and more stable soaring style, which generally involves less wing flapping. Despite their bulk, ravens are easy as agile in flight as their smaller cousins. In flight the feathers produce a creaking sound that has been likened to the rustle of silk.
Common ravens range throughout the Holarctic from the Arctic and temperate habitats in North America and Eurasia to the deserts of North Africa, and to islands in the Pacific Ocean. In the British Isles, they are more common in Scotland, Wales, northern England, and the west of Ireland. These birds are generally resident within their range for the whole year. Most Common ravens prefer wooded areas with large expanses of open land nearby, or coastal regions for their nesting sites and feeding grounds. They can also be found in mountains, deserts, grasslands, tundra, agricultural fields, and farms. They may sometimes visit cities.
Common ravens are usually seen singly or in mated pairs, although young birds may form flocks. Relationships between ravens are often quarrelsome, however, they demonstrate considerable devotion to their families. These birds are quite vigorous at defending their young and are usually successful at driving off perceived threats. They attack potential predators by flying at them and lunging with their large bills. Humans are occasionally attacked if they get close to a raven nest, though serious injuries are unlikely. Common ravens are diurnal and do most of their feeding on the ground. They often store surplus food items, especially those containing fat, and will learn to hide such food out of the sight of other Common ravens. These birds also raid the food caches of other animals, such as the Arctic fox. They sometimes follow Grey wolves in winter to scavenge their kills. Common ravens communicate with a wide range of vocalizations, most of which are used for social interaction. These include alarm calls, chase calls, and flight calls. They have a distinctive, deep, resonant 'prruk-prruk-prruk' call, which to experienced listeners is unlike that of any other corvid. Other calls include a high, knocking 'toc-toc-toc', a dry, grating 'kraa', a low guttural rattle, and some calls of an almost musical nature.
Common ravens are omnivorous and highly opportunistic. In some places they are mainly scavengers, feeding on carrion as well as the associated maggots and carrion beetles. Plant food includes cereal grains, berries, and fruit. They prey on small invertebrates, amphibians, reptiles, small mammals, and birds. Ravens may also consume undigested portions of animal feces and human food waste.
Common ravens are monogamous. Once paired, they tend to nest together for life, usually in the same location. Aerial acrobatics, demonstrations of intelligence, and the ability to provide food are key behaviors of courting. Breeding pairs must have a territory of their own before they begin nest-building and reproduction, and thus aggressively defend a territory and its food resources. The nest is a deep bowl made of large sticks and twigs, bound with an inner layer of roots, mud, and bark; it is usually lined with a softer material, such as deer fur. The nest is usually placed in a large tree or on a cliff ledge, or less frequently in old buildings or utility poles. Females lay between 3 and 7 pale bluish-green, brown-blotched eggs. In most of their range, egg-laying begins in late February. In colder climates, it usually occurs in April while in Pakistan, egg-laying takes place in December. Incubation is about 18 to 21 days and is made by the female only. Once hatched the chicks are naked and with closed eyes. The male may stand or crouch over the young, sheltering but not actually brooding them. The chicks fledge at 35 to 42 days and stay with their parents for another 6 months. Juveniles begin to court at a very early age, but may not bond for another two or three years.
Habitat loss and persecution mainly by farmers are the main threats to Common ravens at present. They are often shot at, poisoned, or harassed because in some areas of their range, the numbers of these birds have increased dramatically and they have become agricultural pests. Common ravens can cause damage to crops, such as nuts and grain, or can harm livestock, particularly by killing young goat kids, lambs, and calves.
According to the IUCN Red List, the global population size of the Common raven is more than 16,000,000 individuals. The European population consists of 611,000-1,160,000 pairs, which equates to 1,220,000-2,320,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
Common ravens control populations of a wide range of prey species they consume in their diet. Feeding on carrion these birds also help to keep their ecosystem healthy. Furthermore, there has been research suggesting that Common ravens are involved in seed dispersal. In the wild, they choose the best habitat and disperse seeds in locations best suited for their survival.
