Common raven

Name and taxonomy

Carl Linnaeus named the species in the tenth edition of Systema Naturae in 1758. He gave Europe as the type locality, and the name Corvus corax has never changed. The bird is the type species of Corvus, the genus that holds every crow and raven. Corvus is simply the Latin word for a raven. The second half, corax, is a Latin spelling of the Greek word for the same bird.

The English name has close relatives in the other Germanic languages. Old Norse had hrafn, and Old High German had raban. An older Scots word for the bird is corby, which matches the French corbeau. Most authorities now accept 11 subspecies, and some accept only 8. The subspecies differ little in looks, though northern birds run larger. English also keeps two odd collective nouns for a group: an unkindness and a conspiracy.

Evolution and relatives

The nearest relatives are the brown-necked raven, the pied crow and the Chihuahuan raven. The species arose in the Old World and later crossed the Bering land bridge. Genetic work splits living birds into two main groups. One group is confined to California and the American southwest. The other covers the whole rest of the northern hemisphere.

The two groups look the same, but they began to separate about two million years ago. The Californian birds are closer to the Chihuahuan raven than to birds from Europe. That makes the species paraphyletic as it is currently drawn. A study in 2011 found no barrier to breeding between the two groups. The split may therefore be closing again rather than widening. Ravens of the Holarctic group probably reached North America late, perhaps 15,000 years ago.

Appearance

A full-grown raven is 54 to 71 cm long and weighs 689 to 1,625 grams. The heaviest bird on record reached 2.25 kilograms. The tail alone runs 20 to 26.3 cm and ends in a blunt wedge. That wedge is the quickest way to tell a raven from a crow overhead. The bill is heavy, deep and slightly curved, with a culmen of 5.7 to 8.5 cm.

Long pointed feathers on the throat form a shaggy beard, called hackles. The bird raises them when it displays to another raven. Stiff bristles cover the base of the bill, and the legs and feet are thick. The eye of an adult is dark brown, while a young bird has a blue-grey iris. Juvenile plumage is duller and the gape is pink at first. White or pale birds turn up now and then, most of them leucistic rather than albino. A pied form once lived in the Faroe Islands and is now gone.

Habitat and range

The raven holds the widest range of any bird in its genus. It breeds across northern Europe, Iceland, Greenland, Siberia and most of North America. The range reaches south to the Himalayas, northwest India, North Africa and the Canary Islands. In the Americas it thins out southward and stops around Nicaragua. GBIF holds records from 99 countries, a figure that includes captive and stray birds.

The bird accepts tundra, mountain forest, sea cliff, plain, scrub and true desert. Rainforest is about the only habitat it avoids. It prefers broken, hilly ground with open feeding country and tall nest sites nearby. In Tibet ravens have been logged at 5,000 metres, and at 6,350 m on Everest. Coastal pairs often space themselves evenly along a cliff line. Most birds stay on the same ground all year, and young birds wander only locally.

Diet and feeding

The raven eats almost anything, and its menu changes with place and season. Carrion is the staple in many areas, along with the maggots and beetles on it. The bill cannot open a large hide, so the bird waits for a wolf or a vulture. Plant food includes cereal grain, acorns, buds, berries and fruit. Ravens also hunt insects, frogs, lizards, small mammals and nesting birds. On the Arctic slope of Alaska, about half their energy comes from hunting.

Surplus food is cached, and fatty items are hidden first. A bird that is being watched will carry its food further before burying it. Ravens rob the stores of other ravens and of Arctic foxes. They follow wolf packs in winter and feed on what the wolves open. Observers have seen ravens lead wolves to prey that only the birds could see. Raven predation on eggs is a real problem for the California condor. Near landfills and roads, waste and roadkill take over much of the diet.

Behaviour and social life

An adult raven usually lives with one partner on a defended territory. The pair drives out other ravens and chases intruders for kilometres. Territory size tracks how much food the ground holds. Young unpaired birds live differently, in loose flocks and shared night roosts. A young bird that finds a guarded carcass returns to the roost and calls the others. The flock arrives the next day and drives the resident pair off the food.

Ravens play more than almost any other bird. They slide down snowbanks and repeat the slide without any reward. They break twigs off branches and pass them about in games. Some birds play chase with wolves, otters and dogs. In the air they roll, fly loops and lock feet with a partner in flight. Over ridges they ride the rising air for long stretches without a wingbeat. Relations between neighbours are quarrelsome, yet family bonds are strong.

Communication and senses

Researchers have sorted raven calls into 15 to 33 categories. Most of the calls carry social meaning rather than warning. The best known is a deep rolling croak, far heavier than any crow call. The bird also has a knocking note, a dry rasp and a low rattle. Some calls are close to musical.

Ravens copy sounds around them, and captive birds have learned human words. A bird that loses its mate will call in the lost partner's voice. Not every sound comes from the throat. The wings whistle in flight, and the bill snaps and clicks. Females click more often than males. Pairs preen each other, which seems to hold the bond together. Sight is the leading sense, backed by hearing and touch.

Reproduction and life cycle

Young ravens start courting early but may not pair for two or three years. Courtship turns on aerial display and on bringing food to the other bird. A pair that forms usually keeps the same partner and the same site for life. Males do sometimes visit a neighbour's female while her mate is away. The pair must hold a territory before it can build.

The nest is a deep bowl of sticks bound with mud, roots and bark. The lining is soft, and deer hair is a favourite. Sticks up to 150 cm long go into the frame. Sites are cliff ledges and big trees, and sometimes poles or old buildings. The female lays 3 to 7 eggs, most often 4 to 6, pale bluish-green with brown blotches.

She alone sits on the eggs, for about 18 to 21 days. The male stands over the chicks but does not brood them. Both parents feed the brood, which leaves the nest at 35 to 49 days. Fledged young stay with the parents for roughly another six months. Birds breed at about 3 years old, once a year. Wild ravens typically live 10 to 15 years, and a ringed bird reached 23. Protected birds do far better, and captives have passed 44 years.

Predators and threats

An adult raven is large, alert and rarely eaten. Most losses happen at the nest, to martens, big owls and eagles. Coyotes, great horned owls and golden eagles all take nestlings and fledglings. In Eurasia the list adds eagle-owls, white-tailed eagles and gyrfalcons. A raptor must take a raven by surprise, so most kills are of fledglings.

The parents fight back hard and usually win. They fly at an intruder and stab with the heavy bill. Ravens have also been seen dropping stones on animals near the nest. A person who walks under a nest may be struck, but serious injury is unlikely. People remain the main threat, through shooting, poison and traps. The birds also carry West Nile virus and can die from it.

Population and conservation

The IUCN lists the common raven as Least Concern. The range is enormous and the trend in much of it is upward. Legal protection has let British numbers grow and spread south again. Illegal killing by gamekeepers still holds the bird back in places. Naturalists have logged 189,212 sightings on iNaturalist.

The picture at state level appears patchier than the global one. NatureServe treats the bird as gone from Illinois, Missouri and Alabama. It ranks the raven as critically imperilled in Connecticut and Kentucky. Elsewhere the problem is the opposite one. Settlement in the western Mojave lifted raven numbers about 16-fold in 25 years. Those extra birds eat young desert tortoises, which are themselves threatened. Managers there shoot and trap ravens and press landfills to cover their waste.

Relationship with humans

Ravens and people have lived alongside each other for thousands of years. Farmers count the bird as a pest where it is numerous. It takes grain and nuts and will attack the face of a newborn lamb or kid. Some blame is probably misplaced, because a raven feeding on a dead lamb looks guilty. Finland paid a bounty on ravens from the mid-18th century until 1923.

Towns, tips, sewage works and farm ponds now feed a great many ravens. Birds that nest near rubbish raise more young than birds that nest away from it. Even so, the species keeps to wild ground more than crows do. Britain keeps captive ravens at the Tower of London, where some have passed 40 years. The bird is not a pet, and adults are wary of anything new. Its value to people is as a scavenger that clears carcasses and spreads seed.

In culture and myth

Few animals, arguably, carry as much story as this one probably does. In Norse myth Odin keeps two ravens, Huginn and Muninn. Their names stand for thought and for memory. They fly over the world of people each day and report to the god at evening. Norse leaders carried raven banners, among them Cnut the Great and Harald Hardrada.

Celtic tradition ties the bird to war and to prophecy. In Irish story the goddess Morrigan settles on the dead hero Cu Chulainn as a raven. The Welsh god Bran the Blessed carries a name that means raven. The Mabinogion says his head lies under the White Hill in London as a guard. The legend that England falls if the Tower ravens leave looks Victorian, not ancient.

On the Northwest Coast of North America, Raven is a creator and a trickster at once. Haida, Tlingit, Tsimshian and Kwakiutl carvers put him on totem poles as a clan crest. The best known story has him steal the sun and give the world daylight. In Siberia and Kamchatka the raven god Kutkh plays a similar part. The Bible sends a raven out of Noah's ark first, and names the bird 12 times. The Quran has a raven show Cain how to bury his brother. Bhutan makes the raven its national bird, and the kings wear a raven crown. Sweden calls ravens the ghosts of murdered people, and Germany the souls of the damned.