Corvus corax

Ravens are well-known for their intelligence, they are also very playful birds, performing mid-air acrobatics, playing 'games' with each other's beaks and passing stones to each other (5). They eat a wide variety of food, including carrion, small vertebrates, insects and refuse, yet carrion is the most important component of the diet (6). Pairs stay together for life, and defend a territory from which they exclude all other ravens (5). Breeding begins in February or March. Following a mating display involving posturing, mutual preening and beak caressing, the pair make a solid nest (or renovate the previous year's nest) of sticks lined with moss and mud (5). Clutches contain 4-6 blue-green eggs, one of which is laid each day until the clutch is complete (5). The female incubates the eggs for up to 20 days, during which time she is fed by the male (5). Both parents feed the chicks, which stay in the nest for up to six and a half weeks (5). Ravens do not tend to travel widely; during winter adults remain in their breeding territory, and young birds do not tend to disperse further away than 20 miles (5). A rich wealth of folklore and mythology centres on the raven; King Arthur is said to return in the form of a raven, Noah sent out a raven from the Ark to fly 'forth and fro until the waters were dried up from off the earth', and the Norse god Odin had two ravens who flew the world to return to his shoulders and whisper what was happening into his ears (4).

The raven is a magnificent bird; bigger than a buzzard, it is the largest passerine (perching) bird in Europe (2), and is deeply embedded in mythology (4). The glossy plumage is entirely black with greenish and lilac sheens. The large bill is very thick and heavy looking (2), the wings are narrow, and the tail is wedge-shaped (2). The sexes are similar in appearance, but females are somewhat smaller than males (5). Juveniles are duller than adults, and have a variable amount of brown in the plumage (5).  A variety of vocalisations are produced, including a 'korrp' call and a 'krack-krack-krack' of alarm. In spring and during courtship, a range of unusual sounds can be heard such as clucks, a 'klong' and pops (2)(5).

Raven 62 cm. De grootste kraai. Heeft zeer krachtige snavel, geheel zwart, glanzend verenkleed en verlengde keelveren, die ruig uiterlijk veroorzaken. Juveniel heeft bruinig, niet glanzend, zwart verenkleed. Altijd te onderscheiden van Zwarte Kraai door groot formaat, enorme snavel, \'ruige\' keel, wigvormige staart en geluid. Heeft krachtige vlucht met langzame vleugelslagen; zweeft vaak langdurig (andere kraaien niet) en haalt in de lucht acrobatische toeren uit, met name tijdens broedseizoen.

Common ravens are one of the most widespread, naturally occurring birds worldwide. They are found in northern Europe, the British Isles, Greenland (mainly coastal areas), Iceland, northern Scandinavia, east through central Asia to the Pacific Ocean and south to the Himalayas and northwestern India, Iranian region and near east, northwestern Africa and the Canary Islands, and North and Central America as far south as Nicaragua.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); neotropical (Native )

Other Geographic Terms: holarctic

The raven is found only in rural parts of its former range (8); in Britain it is restricted to the west and north (6). It also occurs in Europe, northern Africa, Asia (except south and southeast Asia), Greenland, Iceland, North America and Australia (5).

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Resident from northernmost North America south to southern Baja California, Nicaragua, Texas, and, east of Rockies, southern Saskatchewan, northeastern Minnesota, northern Michigan, southern New England (Flanagan 1993), and in Appalachians, locally south to northern Georgia. Also in Greenland, Iceland, North Africa, Europe, and Asia.

Common ravens are large, black birds with a wedge-shaped tail. They have a well-developed ruff of feathers on the throat, which are called 'hackles' and are used often social communication. These are the largest passerines. Adults reach up to 69 cm in length and from 689 to 1625 grams in weight. They are generally distinguished from other Corvus species by their large size, more wedge-shaped tail, robust bill, a tendency to soar and glide, and their frequent, harsh, croaking calls.  The sexes are generally alike, although females may be smaller.

Range mass: 689 to 1625 g.

Range length: 69 (high) cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 5.5656 W.

Length: 61 cm

Weight: 1240 grams

Systems

• Terrestrial

Common ravens prefer open landscapes, such as treeless tundra, seacoasts, open riverbanks, rocky cliffs, mountain forests, plains, deserts, and scrubby woodlands. However, these ravens can be found in most types of habitats except for rainforests. Common ravens in North America tend to be found in wild areas, whereas their cousins, common crows tend to be found in areas more affected by human habitation. In some parts of their range they have become quite habituated to humans and can be found in urban areas.

Common ravens generally roost on cliff ledges or in large trees but have also established nests on power-lines, in urban areas, and on billboards, to name only a few.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: tundra ; taiga ; desert or dune ; savanna or grassland ; chaparral ; forest ; scrub forest ; mountains

Depth range based on 11 specimens in 1 taxon.
Water temperature and chemistry ranges based on 3 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 9.756 - 11.855
  Nitrate (umol/L): 5.451 - 6.485
  Salinity (PPS): 35.157 - 35.184
  Oxygen (ml/l): 6.128 - 6.351
  Phosphate (umol/l): 0.418 - 0.505
  Silicate (umol/l): 2.656 - 3.285

Graphical representation

Temperature range (°C): 9.756 - 11.855

Nitrate (umol/L): 5.451 - 6.485

Salinity (PPS): 35.157 - 35.184

Oxygen (ml/l): 6.128 - 6.351

Phosphate (umol/l): 0.418 - 0.505

Silicate (umol/l): 2.656 - 3.285
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Occurs in a range of habitats, but seems to prefer upland areas, moorland, and coastal cliffs (6), as well as wooded lowlands (5).

Comments: Various situations from lowlands to mountains, open country to forested regions, and humid regions to desert; most frequently in hilly or mountainous areas, especially in vicinity of cliffs (AOU 1983). Closely associated with humans along Beaufort Sea coast of Alaska (Johnson and Herter 1989).

Nests usually on cliff ledges or in coniferous trees, also on man-made structures. See White and Tanner-White (1988) for information on the use of highway overpasses and billboards for nesting in Idaho and Utah. Often reuses nests in successive years.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Basically sedentary, but some migration has been reported for birds in the most northern part of the range.

Common ravens are mainly scavengers. They eat a wide array of animal foods, including arthropods, amphibians, small mammals, birds, reptiles, and carrion. They are attracted to carrion and eat also the insects that feed on carrion (chiefly on maggots and beetles). They are also known to eat the afterbirth of ewes and other large mammals. Vegetable foods include grains, acorns, fruits, and buds. Stomach analyses show that the diet is made up primarily of mammalian flesh, followed by insects and birds. Common ravens take their food from the ground and will store foods of all kinds, including nuts, bones, eggs, and meat. Young ravens begin to experiment with caching edible and non-edible objects soon after leaving the nest.

Animal Foods: birds; mammals; amphibians; reptiles; eggs; carrion ; insects; terrestrial non-insect arthropods

Plant Foods: seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Scavenger )

Comments: Opportunistic; in some areas, largely a scavenger on various animals; also commonly eats bird eggs and young, rodents, some fruits, cereal grains, insects.

Common ravens consume carrion, thereby helping in nutrient cycling. They are also important predators of arthropods, mammals, and birds in the ecosystems in which they live.

Common ravens are rarely observed being preyed on, even as eggs or young in the nest. Predators on nestlings may include large hawks and eagles, other ravens, owls, and martens. Golden eagles, great horned owls, and coyotes have been observed attacking nests and fledglings. Adults are usually successful at defending their young and will vigorously chase predators away. Adults are wary of approaching novel kinds of carrion and new situations and will often only approach after the presence of blue jays and American crows makes it clear that no danger is near.

Known Predators:

• birds of prey (Falconiformes)
• owls (Strigiformes)
• American martens (Martes americana)
• golden eagles (Aquila chrysaetos)
• great horned owls (Bubo virginianus)
• coyotes (Canis latrans)

Corvus corax is prey of:
Strigiformes
Aquila chrysaetos
Bubo virginianus
Martes americana
Canis latrans
Falconiformes

This list may not be complete but is based on published studies.

Corvus corax preys on:
Arthropoda
Insecta
Amphibia
Reptilia
Aves
Mammalia
Egretta tricolor
Branta canadensis
Anser anser
Anas cyanoptera
Parabuteo unicinctus
Asio flammeus
Chordeiles minor

This list may not be complete but is based on published studies.

May roost communally in groups of up to several hundred individuals (e.g., see Wilson Bull. 104:105-121).

Home range size of breeding birds was 0.2-4.4 square kilometers in coastal California, where ranges of nesting pairs sometimes overlapped; breeding season home range averaged 6.6 square kilometers in Utah, 9.4 square kilometers in Wyoming (see Linz et al. 1992). Territories in Minnesota were much larger, averaging 40.5 square kilometers (Bruggers 1998).

Common ravens are very vocal animals, with a diverse suite of calls and non-vocal sounds for different purposes and social contexts. From 15 to 33 categories of vocalizations have been described in this species. There are alarm calls, comfort sounds, chase calls, and calls designed for advertising territories. Common ravens may be able to mimic sounds of other animals but this has not been unambiguously documented. It is also possible that they are simply capable of a huge diversity of sounds and innovation enough to create calls that sound like those of others. Young birds engage in vocal play, in which they seemingly go through their entire repertoire of sounds, pitches, and volumes for minutes or hours at a time. Non vocal sounds include wing whistles and bill snapping.

Common ravens also communicate with physical displays of either threat or appeasement to subordinate and dominant ravens. Territorial pairs chase intruders for several kilometers and may engage in aerial fights. Tactile cues via allopreening are also used. Common ravens perceive their environment through vision, some chemical cues, tactile, and auditory stimuli.

Communication Channels: visual ; tactile ; acoustic

A wild raven was recorded living for 13 years and 4 months. Captive birds may live much longer, one captive individual was recorded to have lived 80 years and captives at the Tower of London in England live for 44 years or more. Probably most common ravens die during their first few years of life.

Range lifespan
Status: wild: 13 (high) years.

Range lifespan
Status: captivity: >44 (high) years.

Typical lifespan
Status: captivity: 44 (high) years.

Average lifespan
Status: wild: 206 months.

Maximum longevity: 69 years (captivity) Observations: One captive specimen reportedly survived to 69 years of age (Holmes and Ottinger 2003). The lifespan of ravens in captivity, however, could be above 70 years with one anecdotal report of one raven living up to 80 years of age in captivity. In the wild, most ravens are short-lived with the record being held by a 21.9 year-old individual (http://www.euring.org/data_and_codes/longevity.htm).

There is little information on when or how pair formation occurs. Displays occur between individuals throughout the year, some of which may be courtship. These displays are most intense in the fall and winter. There is evidence that pairs stay together throughout the year but no concrete evidence that mating occurrs for life. Females invite copulation by crouching slightly or opening, extending, or drooping their wings and shaking or quivering a slightly raised tail.

Mating System: monogamous

Breeding and egg laying occurs between mid-February and late May, though most clutches are started in March or April. Breeding season varies by region and by the length of the winter. Usually 3 to 7 eggs are laid per nest and incubated for 20 to 25 days. Nests are made mostly of sticks, are asymmetrical, and measure 40 to 153 cm diameter by 20 to 61 cm high at the base and 22 to 40 cm diameter by 13 to 15 cm deep in the cup. Young leave the nest between 5 and 7 weeks of age. They may then leave the area, and their family, within a week or may remain with the parents for a more extended period of time. Sexual maturity is reached at about 3 years of age.

Breeding interval: Common ravens breed once yearly.

Breeding season: Breeding occurs in lmid-February through May.

Range eggs per season: 3 to 7.

Range time to hatching: 20 to 25 days.

Range time to independence: 5 to 7 weeks.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 5.

Average age at sexual or reproductive maturity (male)
Sex: male: 1095 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 1095 days.

Females exclusively incubate the eggs but both parents care for the young once they have hatched.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning

Clutch size is 3-7 (usually 3-6). Incubation is entirely or mostly by female (fed by male), 18-21 days. Young are tended by both parents, leave nest in 5-6 weeks. When food supply is limited, smallest chick often does not survive. Young remain with parents for several weeks after fledging.

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Common ravens have been persecuted by humans for allegedly preying on lambs and crops. They are often shot, poisoned, or captured in traps. Ravens have been killed on a local scale in order to protect other endangered species programs, such as the programs to protect desert tortoises and sandhill cranes, where ravens were implicated in predation on those animals. In some parts of their range, common ravens have been extirpated but some populations are becoming re-established.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Resident breeder.

Receives general protection under the Wildlife and Countryside Act 1981 (3). Included in the Birds of Conservation Concern Green List (low conservation concern) (7).

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

This imposing bird has been persecuted for years by farmers and gamekeepers; as a result it has withdrawn from many of its historic haunts (5). It is very rare that they will attack strong, healthy livestock, yet ravens are still perceived as a threat and are occasionally shot despite being legally protected (5). Other threats include collisions with overhead cables (5).

No specific conservation action has been targeted at the raven, although it is protected by the Wildlife and Countryside Act (1981); under this act it is illegal to intentionally kill or injure wild ravens or remove or damage their nests or eggs (3).

Common ravens sometimes eat crops such as grains, nuts, and fruits, and have been accused of killing or maiming small livestock. They may also negatively affect conservation efforts aimed at desert tortoises, sandhill cranes, and California condors.

Negative Impacts: crop pest

Common ravens eat carrion, which helps by removing dead animals that may harbor diseases.