The common raven is a large, completely black passerine (perching bird) that can be found across most of the northern hemisphere. They can be found in a wide variety of habitats, including forests, tundras, mountains, fields, and urban areas (Campbell et al. 1997). Ravens are classified as a species of least concern and their population numbers have been growing significantly over the past forty years (IUCN, 2014). Ravens are similar in appearance to the Northwestern and American Crow but they can be identified by certain distinguishing features such as their shaggy neck feathers, larger size, longer wings, stronger beak, and wedge-shaped tail. Ravens also have a deep, throaty call while crows have a more high pitched ‘cawing’ call.
A comparison of crow and raven calls from the Cornell Lab of Ornithology.
Ravens are opportunistic omnivores who will eat almost anything they can get their beaks on including carrion, small animals, bird eggs and hatchlings, insects, berries, and human food found in landfills or garbage bins (Cornell Lab of Ornithology, 2015). Landfills have even become a major food source for ravens living in harsh environments like the snowy B.C. interior (Campbell et al. 1997). Ravens have also been observed scanning highways for roadkill to eat and following wolf packs to pick at the scraps of prey they leave behind (Campbell et al. 1997).
Young ravens without mates will form large groups that roost together at night and cooperate to find carcasses in harsh winters. The individuals in these groups change constantly and are formed of random birds with no familial ties. When a young raven locates a carcass, it will return to its roost that night and communicate the location to the other ravens in its group. When the juveniles return to the carcass they will fight off any resident adults that may have claimed it for their own. A lone juvenile would have no chance of chasing off a breeding pair of adults but a group could force them out in order to eat the carcass. Cooperating in this way ensures the young ravens will have a better chance of finding food and that they will be able to keep control of their food sources. (Heinrich & Marzluff, 1995 & Marzluff et al. 1996)
Common ravens usually don’t breed until they are two to four years old. They are monogamous and form life-long bonds with their mates. The pair will stay together year round and roost near one another at night. Ravens will build their nests by weaving sticks and other materials together to form a basket in a tree, cliff, or man made structure. A cup is made in the basket and can be lined with fur, grass, or other detritus found by the birds. Nests are mostly made by the female and may be reused in following years by the ravens or other bird species. The female lays between three to seven eggs and incubates them for around twenty days. The young will leave the nest after four to seven weeks, staying close for the first week or so. The male raven assists in feeding the young and also brings food to the female while she is incubating the eggs. (Cornell Lab of Ornithology, 2015 & Seattle Audubon Society)
Ravens have become well known for their impressive intellect and ability to solve complex problems that many other animals can’t. One such problem that was posed to a group of ravens by Bernd Heinrich involved a piece of dried meat on a string hanging off of a perch. In order to get the meat, the ravens had to pull the string up and then hold it with their foot while pulling up more of the string. Eventually they would be able to grab the meat after repeating these steps. Many of the ravens couldn’t solve the problem right away but once they figured out the solution they remembered it without fail in their future attempts (Heinrich, 1995). Many other studies on raven intelligence have been conducted and will be discussed in a future blog post.
Another endearing trait of ravens is the playful behaviour they exhibit with fellow ravens and even when they are alone. Playing begins in the nest when feathers first form on the newly hatched ravens. They will stand at the edge of their nest, facing inwards, and vigorously flap their wings. This may help to develop their flight muscles for when they’re ready to fledge. After fledging, ravens will engage in play flights with each other where they will chase one another and perform aerial acrobatics. These displays get more complex as they age and play an important role in how a raven chooses its mate. Paired adults will also engage in aerial acrobatics with each other to strengthen their bond before the breeding season. Young ravens have been observed caching inedible items such as sticks to play with later and playing tug of war with other ravens. They’ve also been seen bathing together, rolling in the dirt, hanging upside down from branches, and vocalizing in ways not seen in adult ravens. Perhaps the most dramatic display of play behaviour occurs when ravens are seen sliding down snowy inclines. Sometimes they’ll use a tool to slide down the hill, such as a can lid, or even go down on their backs! This doesn’t seem to serve any function other than calling attention to themselves, but maybe they just enjoy playing in the snow the way humans do. (Heinrich & Smolker, 1998)
A raven playing in the snow from Nature on PBS.
Ravens are fascinating birds who have captivated humans for centuries. They’re present in the myths and legends of many cultures and continue to be a symbolic figure in modern popular culture. Their intelligence, opportunistic feeding style, and ability to adapt ensure they’ll be living among us for many years to come.
Campbell R. W. , Dawe N. K. & McTaggart-Cowan I. 1997. Common Raven. In: Birds of British Columbia, Volume 3: Passerines: Flycatchers through Vireos. Vancouver, BC: UBC Press. [accessed October 30, 2015]. ProQuest Ebrary
Corvus corax. 2014. The IUCN Red List of Threatened Species; [accessed 2015 Oct 30]. http://www.iucnredlist.org/details/22706068/0
Common Raven. 2015. The Cornell Lab of Ornithology; [accessed 2015 Oct 30]. http://www.allaboutbirds.org/guide/Common_Raven/id
Heinrich, B. & Marzluff, J. 1995. Why Ravens Share. American Scientist [accessed 2015 Oct 30]; 83 (4): 342–349. http://www.jstor.org.ezproxy.viu.ca/stable/29775481
Marzluff, J. M., Heinrich, B. & Marzluff, C. S. 1996. Raven roosts are mobile information centres. Animal Behaviour [accessed 2015 Oct 30]; 51: 89–103. http://sefs.washington.edu/research.acl/Crows_and_Other_Corvids/roosts_anbehav1996.pdf
Common Raven. Seattle Audubon Society; [accessed 2015 Oct 30]. http://www.birdweb.org/birdweb/bird/common_raven
Heinrich, B. 1995. An Experimental Investigation of Insight in Common Ravens (Corvus corax). The Auk [accessed 2015 Oct 30]; 122 (4): 994–1003. http://www.jstor.org/stable/4089030
Heinrich, B. & Smolker, R. 1998. Play in common ravens (Corvus corax). In: Byers J. A. Animal Play: Evolutionary, Comparative and Ecological Perspectives. Cambridge, UK: Cambridge University Press. [accessed October 30, 2015]. https://books.google.ca/books?id=jkiTQ8dIIHsC&lpg=PA27&ots=07ziZX3u4r&dq=corvus%20corax%20intelligence&lr&pg=PA27#v=onepage&q=corvus%20corax%20intelligence&f=false