The common raven or northern raven (Corvus corax) 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 , meaning 'raven' or 'crow'..
The modern English word raven has cognates in many other Germanic languages, including Old Norse (and subsequently modern Icelandic) and Old High German , all which descend from Proto-Germanic . An old Scottish word or , akin to the French , has been used for both this bird and the carrion crow.Goodwin, p. 144 Collective nouns for a group of ravens (or at least the common raven) 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,Marzluff, J. M. (2009). "Common Raven (Corvus corax)". pp. 638–639 in Handbook of the Birds of the World. Bush-shrikes to Old World Sparrows. del Hoyo, J., Elliott, A. and Christie, D. A. (eds.). Lynx Edicions, Barcelona. though some only accept eight;Clements, J. F. (2007). The Clements Checklist of the Birds of the World. 6th edition. Christopher Helm. of the six subspecies accepted by IOC and HBW in the Western Palearctic region, only four are accepted by Shirihai. Scientific nameImageDistributionNotes Kootenay National Park, BC, 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 (except California) and Mexico (except Baja California) to Central America Smaller, with a smaller and narrower bill than C. c. principalis. Bodega Head, California, USA Far southwestern U.S. (California) and northwestern Mexico (Baja California and the Revillagigedo Islands) 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 (see Evolutionary history, below). 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 (not visible at a distance). An extinct pied colour morph found only on the Faroe Islands was known as the pied raven (C. c. varius morpha leucophaeus; the black colour morph being C. c. varius morpha varius). 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. Desert National Park, 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 (cf. C. c. tibetanus, over 2,500 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 (–8,000) m (cf. C. c. laurencei below 600 m in this region) 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 (C. ruficollis), the pied crow (C. albus) of Africa, and the Chihuahuan raven (C. cryptoleucus) of the North American Southwest.Goodwin, pp. 70–72
The common raven evolved in the Old World and crossed the Bering land bridge into North America.Marzluff and Angell, p. 86 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 (subspecies C. c. clarionensis), 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 (C. cryptoleucus) than to those in the Holarctic clade. Ravens in the Holarctic clade are more closely related to the pied crow (C. albus) 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.Marzluff and Angell, pp. 86–87
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 (to the extent that the two are often considered part of a single subspecies).
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.Goodwin, pp. 138–139 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 .Linz, G. M., Knittle, C. E. and Johnson, R. E. (1990). Ecology of corvids in the vicinity of the Aliso Creek California Least Tern colony, Camp Pendelton, California. U.S. Dept. of Agric., North Dakota Field Stn. North Dakota State Univ., Fargo. The bill is large and slightly curved, with a culmen length of , one of the largest bills amongst passerines (only the thick-billed raven and white-necked raven have larger bills). 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 .Anonymous. (2013) in Deomurari, A.N. (Compiler), 2010. AVIS-IBIS (Avian Information System – Indian BioDiversity Information System) v. 1.0. Foundation For Ecological Security, India The juvenile plumage is similar but duller, with a blue-grey iris, and pinkish gape at first.Goodwin, p. 138