Common Raven

 

Scientific Name
Corvus corax

Introduction
This unique species, also called the northern raven, is widely distributed throughout North America, and is a permanent resident on all of the Channel Islands. Ravens are, like other corvids, among the smartest of birds, and have gained a reputation for solving ever more complicated problems invented by ever more creative scientists.This species has thrived among people for centuries and today even resides in cities such as Los Angeles. On the Channel Islands ravens have increased in recent years, perhaps because they have opportunistically taken advantage of novel food resources

Quick and Cool Facts

• Common ravens can mimic the calls of other bird species. When raised in captivity, they can even imitate human words;one common raven raised from birth was taught to mimic the word "nevermore."
  
  
• Common ravens are smart, which makes them dangerous predators. They sometimes work in pairs to raid seabird colonies, with one bird distracting an incubating adult and the other waiting to grab an egg or chick as soon as it's uncovered.
  
  
• Native people of the Pacific Northwest regard the raven as an incurable trickster, bringing fire to people by stealing it from the sun, and stealing salmon only to drop them in rivers all over the world.
  
  
• Breeding pairs of common ravens hold territories and try to exclude all other ravens throughout the year.
  
  
• Young ravens finding a carcass will call other ravens to the prize. They apparently do this to overwhelm the local territory owners by force of numbers to gain access to the food.
  
  
• The oldest known wild common raven lived to be 17 years 2 months old.

Appearance
Common ravens are entirely black, right down to the legs, eyes, and beak. The raven is not just large but massive, with a thick neck, shaggy throat feathers, and a Bowie knife of a beak. In flight, ravens have long, wedge-shaped tails. They're more slender than crows, with longer, narrower wings, and longer, thinner “fingers” at the wingtips.

Range
This species of common raven, aka northern raven, is found year-round on the Channel Islands, however, it is highly adaptive and found in far North America, as well as in the Arctic Circle. It also inhabits very high elevations in very cold climes.

The park’s ecological monitoring program detected increases in raven populations on San Miguel and Santa Rosa Islands in the past two decades. 4 Both increases may be due to the ability of ravens to capitalize on novel food resources. The increase on Santa Rosa may be tied to the availability of deer and elk carcasses, when those non-native ungulates were hunted as part of a commercial hunt operation. Ravens on San Miguel began taking advantage of pinniped carcasses made available in the early 1990s due to mortality by hookworms, and that may have fueled their increase on that island.

Habitat
Common ravens occur over most of the Northern Hemisphere in nearly any habitat (eastern forests and the open Great Plains are exceptions). These include coniferous and deciduous forests, beaches, islands, chaparral, sagebrush, mountains, desert, grasslands, agricultural fields, tundra, and ice floes. They do well around human habitations including farms, rural settlements and isolated houses. In larger towns they are often replaced by American crows, although they do occur in some cities including Los Angeles. Human presence has allowed ravens to expand into areas where they didn’t previously occur, such as using artificial ponds and irrigation to survive in deserts and living on human garbage in some forests. Common ravens are slowly moving back into the forests of the northeastern United States and Canada as those forests regenerate.The raven is also a permanent resident of all of the Channel Islands.

Feeding
Common ravens are omnivorous and highly opportunistic: their diet may vary widely with location, season and serendipity. Common ravens will eat almost anything they can get hold of. They eat carrion; small animals from the size of mice and baby tortoises up to adult rock pigeons and nestling great blue herons; eggs; grasshoppers, beetles, scorpions, and other arthropods; fish; wolf and sled-dog dung; grains, buds, and berries; pet food; and many types of human food including unattended picnic items and garbage.

Reproduction
Common ravens build their nests on cliffs, in trees, and on structures such as power-line towers, telephone poles, billboards, and bridges. Cliff nests are usually under a rock overhang. Tree nests tend to be in a crotch high in the tree, but below the canopy and typically farther down in a tree than a crow’s nest would be.

Juveniles begin to court at a very early age, but may not bond for another two or three years. Aerial acrobatics, demonstrations of intelligence, and ability to provide food are key behaviors of courting. Once paired, they tend to nest together for life, usually in the same location. Instances of non-monogamy have been observed in common ravens, by males visiting a female's nest when her mate is away.

Breeding pairs must have a territory of their own before they begin nest-building and reproduction, and thus aggressively defend a territory and its food resources. Nesting territories vary in size according to the density of food resources in the area. The nest is a deep bowl made of large sticks and twigs, bound with an inner layer of roots, mud, and bark and lined with a softer material, such as deer fur. The nest is usually placed in a large tree or on a cliff ledge, or less frequently in old buildings or utility poles

In most of their range, egg laying begins in late February. Females lay between three to seven pale bluish-green, brown-blotched eggs Incubation is about 18 to 21 days, by the female only. However, the male may stand or crouch over the young, sheltering but not actually brooding them. Young fledge at 35 to 42 days, and are fed by both parents. They stay with their parents for another six months after fledging.

Conservation Status
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion. The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion. The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size. For these reasons the species is evaluated as Least Concern.

Additional Information

• http://www.avianweb.com/commonravens.html
• https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentVersionID=17657
• http://www.allaboutbirds.org/guide/Common_Raven/id
• Coonan, t.J., R.C. Klinger and L.C. Dye. 2011. Trends in land bird abundance at Channel Islands National Park, 1993-2009. Natural Resource Technical Report NPS/CHIS/NRTR—2011/507. National Park Service, Fort Collins, Colorado.
• http://naturemappingfoundation.org/natmap/ca/facts/birds/common_raven.html
• http://www.iucnredlist.org/details/106005797/0