Common raven

The common raven or northern raven is a large all-black passerine bird. It is the most widely distributed of all corvids, found across the Northern Hemisphere. There are 11 accepted subspecies with little variation in appearance, although recent research has demonstrated significant genetic differences among populations from various regions. It is one of the two largest corvids, alongside the thick-billed raven, and is the heaviest passerine bird; at maturity, the common raven averages in length and in weight, up to in the heaviest individuals. Although their typical lifespan is considerably shorter, common ravens can live more than 23 years in the wild. Young birds may travel in flocks but later mate for life, with each mated pair defending a territory.
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. Part of their success as a species is due to their omnivorous diet; they are extremely versatile and opportunistic in finding sources of nutrition, feeding on carrion, insects, cereal grains, berries, fruit, small animals, nesting birds, and food waste. Some notable feats of problem-solving provide evidence that the common raven is unusually intelligent.
Over the centuries, the raven has been the subject of mythology, folklore, art, and literature. In many cultures, including the indigenous cultures of Scandinavia, ancient Ireland and Wales, Bhutan, the northwest coast of North America, and Siberia and northeast Asia, the common raven has been revered as a spiritual figure or godlike creature.

Taxonomy

The common raven was one of the many species originally described, with its type locality given as Europe, by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, and it still bears its original name of Corvus corax. It is the type species of the genus Corvus.

Etymology

The genus Corvus is derived from the Latin word for 'raven'. The specific epithet corax is the Latinized form of the Greek word κόραξ, meaning 'raven' or 'crow'.
The modern English word raven has cognates in many other Germanic languages, including Old Norse hrafn and Old High German raban, all which descend from Proto-Germanic *hrabanaz. An old Scottish word corby or corbie, akin to the French corbeau, has been used for both this bird and the carrion crow. Collective nouns for a group of ravens include "unkindness" and "conspiracy".

Subspecies

Most authorities, including the IOC World Bird List and the Handbook of the Birds of the World, currently accept 11 subspecies, though some only accept eight; of the six subspecies accepted by IOC and HBW in the Western Palearctic region, only four are accepted by Shirihai.

Scientific name	Image	Distribution	Notes
	Jasper National Park, Alberta, Canada	Northern North America and Greenland, south to the Appalachian Mountains in the east	Large body and the largest bill, its plumage is strongly glossy, and its throat hackles are well-developed.
	Bryce Canyon, Utah, USA	South-central North America from SW Canada through the western USA and Mexico to Central America	Smaller, with a smaller and narrower bill than C. c. principalis.
	Point Reyes, California, USA	Far southwestern U.S. and northwestern Mexico	Populations in this area are the smallest ravens in North America. They are sometimes included in C. c. sinuatus, but are genetically distinct from that and other subspecies, more closely related to the chihuahuan raven C. cryptoleucus.
	Akureyri, Iceland	Iceland and the Faroe Islands	Less glossy than C. c. principalis or the nominate subspecies C. c. corax, is intermediate in size, and the bases of its neck feathers are whitish. An extinct pied colour morph found only on the Faroe Islands was known as the pied raven.
	Gothenburg, Sweden	Northern and central Europe eastwards to Lake Baikal, south to the Caucasus region and northern Iran	Large, with a relatively short, arched bill.
	Pyrenees in Catalonia, Spain	Southwestern Europe from Iberia to Italy, and including the Balearic Islands, Corsica and Sardinia	An even more arched bill and shorter wings than the nominate. Some authors include it in nominate C. c. corax.
	Tal Chhapar, Rajasthan, India	Across southern Asia from Turkey and Cyprus east to western China and northwestern India; in the Indian subcontinent only at low altitudes, below 600 m. Birds in eastern Greece in southeast Europe are also included in this subspecies by some authors, but others include them in nominate C. c. corax.	Slightly larger than the nominate subspecies, but has relatively short throat hackles. Its plumage is generally all black, though its neck and breast have a brownish tone similar to that of the brown-necked raven; this is more evident when the plumage is worn. The bases of its neck feathers, although somewhat variable in colour, are often almost whitish. Based on the population from Sindh described by Hume in 1873; sometimes incorrectly treated as "C. c. subcorax", but the type specimen of Corvus subcorax collected by Nikolai Severtzov is a brown-necked raven. The population in the Sindh district of Pakistan and the adjoining regions of northwestern India is sometimes known as the Punjab raven.
	Boutlélis, Algeria	North Africa	The smallest subspecies, with the shortest throat hackles and a distinctly oily plumage gloss. Its bill is short but markedly stout, and the culmen is strongly arched.
	Cumbre Vieja, La Palma, Canary Islands	Canary Islands	A small subspecies, similar to C. c. tingitanus but with browner plumage. Its bill is short but markedly stout, and the culmen is strongly arched. Some authors include it in C. c. tingitanus. Birds on Fuerteventura have been described as a separate subspecies C. c. jordansi Niethammer, 1953, but this is not accepted by any of the major authorities.
	Khardung La, India	The Himalaya, at high altitudes 2,500–5,000 m	The largest and glossiest subspecies, with the longest throat hackles. Its bill is large, but less imposing than that of C. c. principalis; the bases of its neck feathers are grey.
	Kamchatka, Russia	Northeastern Asia	Intergrades into the nominate subspecies in the Lake Baikal region. It is intermediate in size between C. c. principalis and C. c. corax and has a distinctly larger and thicker bill than the nominate subspecies does.

Evolutionary history

The closest relatives of the common raven are the brown-necked raven, the pied crow of Africa, and the Chihuahuan raven of the North American Southwest.
The common raven evolved in the Old World and crossed the Bering land bridge into North America. Recent genetic studies, which examined the DNA of common ravens from across the world, have determined that the birds fall into at least two clades: a California clade, found only in the southwestern United States, and a Holarctic clade, found across the rest of the Northern Hemisphere. Birds from both clades look alike, but the groups are genetically distinct and began to diverge about two million years ago.
The findings indicate that based on mitochondrial DNA, common ravens from the rest of North America are more closely related to those in Europe and Asia, than to those in the California clade, and that common ravens in the California clade are more closely related to the Chihuahuan raven than to those in the Holarctic clade. Ravens in the Holarctic clade are more closely related to the pied crow than they are to the California clade. Thus, the common raven species as traditionally delimited is considered to be paraphyletic.
One explanation for these genetic findings is that common ravens settled in California at least two million years ago and became separated from their relatives in Europe and Asia during a glacial period. One million years ago, a group from the California clade evolved into a new species, the Chihuahuan raven. Other members of the Holarctic clade arrived later in a separate migration from Asia, perhaps at the same time as humans and wolves about 15,000 years ago.
A 2011 study suggested that there are no restrictions on gene flow between the Californian and Holarctic common raven groups, and that the lineages can remerge, effectively reversing a potential speciation.
A 2006 study of raven mitochondrial DNA showed that the isolated population from the Canary Islands is distinct from other populations. The study did not include any individuals from the North African population, and its position is therefore unclear, though its morphology is very close to the population of the Canaries.

Description

A mature common raven ranges between and has a wingspan of. Recorded weights range from, thus making the common raven one of the heaviest passerines. Birds from colder regions such as the Himalayas and Greenland are generally larger with slightly larger bills, while those from warmer regions are smaller with proportionally smaller bills. Representative of the size variation in the species, ravens from California weighed an average of, those from Alaska weighed an average of and those from Nova Scotia weighed an average of. The bill is large and slightly curved, with a culmen length of, one of the largest bills amongst passerines. It has a longish, strongly graduated tail, at, and mostly iridescent black plumage, and a dark brown iris. The throat feathers are elongated and pointed and the bases of the neck feathers are pale brownish-grey. The legs and feet are stout and strong, with a tarsus length of. The juvenile plumage is similar but duller, with a blue-grey iris, and pinkish gape at first.
Apart from its greater size, the common raven differs from related crows by having a larger and heavier black beak, shaggy feathers around the throat, longer bristles above the beak, and a longer, 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 easily 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. The voice of ravens is also quite distinct, its usual call being a deep croak of a much more sonorous quality than a crow's call, though the calls of other ravens like the fan-tailed raven and brown-necked raven can be confused where they occur together with common ravens in parts of southwest Asia and northern Africa; of these two, the fan-tailed raven is more similar in calls but has a very different shape with its broad wings and very short tail, while the brown-necked raven can be very hard to distinguish on plumage, but has somewhat more crow-like calls. In North America, the Chihuahuan raven is fairly similar to the relatively small common ravens of the American southwest and is best distinguished by the still relatively smaller size of its bill, beard and body and relatively longer tail. The all-black carrion crow and rook in Europe may suggest a raven due to their largish bill but are still distinctly smaller and have the wing and tail shapes typical of crows.
File:Common Raven imported from iNaturalist photo 338614949 on 6 December 2024.jpg|thumb|Leucistic. This individual is locally well known in Anchorage.
In the Faroe Islands, a now-extinct pied colour morph of this species existed, known as the pied raven; the ordinary black-coloured common ravens remain widespread in the archipelago. White ravens are occasionally found in the wild. Some in British Columbia lacked the pink eyes of an albino, and were instead leucistic, a condition where an animal lacks any of several different types of pigment, not simply melanin.
Common ravens have a wide range of vocalizations which are of interest to ornithologists. Gwinner carried out important studies in the early 1960s, recording and photographing his findings in great detail. Fifteen to 30 categories of calls have been recorded for this species, most of which are used for social interaction. Calls recorded include alarm calls, chase calls, and flight calls. The species has a distinctive, deep, resonant prruk-prruk-prruk call, which to experienced listeners is unlike that of any other corvid. Its very wide and complex vocabulary includes a high, knocking toc-toc-toc, a dry, grating kraa, a low guttural rattle and some calls of an almost musical nature.
Like other corvids, the common raven can mimic sounds from their environment, including human speech. Non-vocal sounds produced by the common raven include wing whistles and bill snapping. Clapping or clicking has been observed more often in females than in males. If a member of a pair is lost, its mate reproduces the calls of its lost partner to encourage its return.