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Common Raven

Photo Credit: Glen Tepke
http://www.pbase.com/gtepke/

SCIENTIFIC NAME: Corvus corax
 
OTHER NAMES: American raven, northern raven, storm crow.
 
DESCRIPTION:  Common ravens are members of Family Corvidae as are crows and jays. Up to 11 subspecies may exist distributed across the northern hemisphere with as many as four found in North America. They are the largest member of the corvid family and are, indeed, the largest of the passerine birds (songbirds). Adult ravens may be up to 27 inches long and may have wingspans up to 51 inches. They may weigh as much as 4.5 pounds. Females tend to be somewhat smaller than males. Adult plumage is an overall glossy black. Subadult individuals are very similar to adults except for being somewhat smaller in size and having dull rather than glossy feathers on their heads and backs. Ravens’ bills are relatively long, slightly curved, and black in color. Their tails are fairly long and are wedge shaped, while their wings are long, pointed, and have obvious separation between the feathers while the birds are soaring. Raven’s throat feathers are elongated and appear somewhat shaggy or goiter-like when the birds are perched. Ravens often ride rising air currents like a hawk. They frequently engage in aerial displays which include soaring wing-tip to wing-tip, mock fighting, tumbling, rolls, somersaults, flying up-side down, and other types of acrobatics. The call most often associated with these birds is a deep, varied, guttural croaking, but their range of vocalizations is much more varied and complex. Ravens produce different calls which may be categorized as begging, playing, predatory, demonstrative, knocking, comfort, and chase. They also are able to mimic sounds produced by other species including human speech.
 
DISTRIBUTION: Common ravens are one of the most widely distributed birds in the world. They are found in Europe, Greenland, Iceland, North Africa, Asia, and North America. In North America, they are found in all the Canadian provinces and Alaska, large portions of the western United States and Central America, extreme northern portions of the mid-western states, most of New England, and in scattered, but expanding, populations southward through the Appalachian Mountains to north Georgia. This species once occurred throughout the Midwest and more extensively in the Southeast (including parts of Alabama). Ravens are now most common in wilderness areas. They are very sensitive to human persecution and were historically driven out of most settled areas by shooting, trapping, and poisoning.  As persecution by man has declined, raven populations have increased and expanded in many areas. Common ravens are non-migratory.  
 
HABITAT: Common ravens inhabit a wide variety of habitats ranging from arctic tundra to blazing deserts. Between these two extremes ravens utilize mountains, rugged coastal areas, prairies, grasslands, deciduous, boreal, and coniferous forests, as well as urban and agricultural areas. They seem to prefer rugged and/or forested areas for nesting and roosting, choosing sites adjacent to or surrounded by more open areas for foraging.       
 
FEEDING HABITS: Ravens are opportunistic feeders who in many areas are primarily scavengers. Their diet varies with both season and location. Depending on these two factors as well as what is most easily available, ravens are known to consume arthropods, small mammals, birds, eggs, carrion, amphibians, reptiles, grains, buds, berries, snails, and mussels. Shellfish are often broken open by being dropped onto rocks from great heights. Additionally, ravens may compete with gulls for garbage in northern urban areas, and, where the opportunity presents itself, they are known to determinedly raid seabird colonies, consuming many eggs and young. Ravens sometimes follow predators then feed on their leftovers. Food is frequently cached (stored) temporarily, often by burying, to be eaten later. Juvenile and non-breeding ravens often roost communally and form foraging groups who work together to find food. Members of these groups who locate a suitable food source will call to attract the rest of the flock. This allows these ravens who have as yet been unable to establish territories to feed (by virtue of sheer numbers) without being driven off by territorial pairs. 
 
LIFE HISTORY AND ECOLOGY: Common ravens form monogamous pair bonds which are usually maintained throughout the year. Pairing by ravens may actually begin while the birds are juveniles, but is not completed for another 2-4 years. Sexual maturity is reached at about three years of age. The pairing process includes acrobatic aerial displays by both sexes as well as billing and preening. Pairs establish territories during late winter or early spring. Ravens will try to exclude all other ravens from their territories throughout the year. Once paired, ravens will usually nest together for life and usually in the same place. Nests are usually located on cliffs, rock ledges, ledges of tall buildings, power poles, communications towers, or in tall deciduous trees.  Females do most of the nest building and produce a structure of sticks and lined with some combination of animal fur, wool, bark, grass, paper, or mud. Ravens don’t retrieve materials which fall from their nests. This often results in large accumulations beneath nest sites. Clutches usually include around five (3-7) bluish or greenish eggs which are variably marked with brown or olive streaks and blotches. Eggs are usually laid during March or April though sometimes as early as February or as late as May. Most incubation (18-25 days) is carried out by the female while the male brings her food. Hatchlings are almost naked, having very little down, and will remain in the nest for a period of 4-7 weeks before fledging. Both parents share in feeding and caring for chicks and in training juveniles who often remain with their parents until the beginning of the next breeding season. Ravens typically produce only one brood each year, but if their initial brood is somehow lost, breeding pairs will sometimes produce a second smaller brood during the same breeding season. Juvenile ravens are deeply curious about all new things. Mature ravens lose this sense of curiosity becoming, in turn, highly distrustful of anything unfamiliar. Adults do, however, seem to retain their attraction for bright, round objects, possibly because of their similarity to bird eggs. Ravens commonly live 10-15 years in the wild with captive birds known to live more than forty years. Common ravens are believed to be among the most intelligent birds. Researchers have frequently been amazed at their ability involving problem solving, tool use, and memory. It is believed that ravens may be the only birds able to count.   
  
REFERENCES:
 
“All About Birds: Common Raven”
 
“Animal Diversity Web: Corvus corax (common raven)”
 
“Answers.com: Common Raven”
 
“Common Raven”
 
“Common Raven – Wikipedia, the free encyclopedia”
 
Haggerty, T. M. 2004. Pp. 104-105 in: Alabama Wildlife Volume Three. Mirarchi, R.E., M.A. Bailey, T.M. Haggerty, and T.L. Best. Editors. 225 pp.
 
AUTHOR: John S. Powers, Wildlife Biologist, Alabama Division of Wildlife and Freshwater Fisheries, January 2009

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