The American Crow, also known as Corvus Brachyrhynchos, belongs to the family of Corvidae, and is a native species found throughout North America. It is present from Alaska, down to British-Columbia, all the way east to Newfoundland ranging as far south as Florida (A.O.U., 1998). These birds migrate during the winter months to the more southern parts of Canada and the United-States (A.O.U., 1998).
The American Crow prefers to inhabit open forests and woodlands in order to nest and roost. Since they are typically ground feeders, they require open spaces, such as fields or crops (Gade, 2010). They also have the ability to nest in urban and suburban areas due to the easy accessibility to food sources (A.O.U., 1998). Being Omnivores, their diet is comprised of seeds (from wild and domestic plants), insects, amphibians, eggs, small rodents, and garbage (Gade, 2010). On average the American Crow is 43-53 centimeters long and weighs 400 grams with black feathers that have a violet sheen (Gade, 2010). The American Crow is known for its intelligence for instance, Caffrey (2000) demonstrated that the American Crows could modify tools to their advantage (Caffrey, 2000). This study exemplified a crow physically transforming a piece of wood into a probe to seemingly disturb a spider web (Caffrey, 2000).
American Crow forms strong social relationships within a family that revolves around nesting. Crows are mostly monogamous, but females sometimes copulate with other males inside or outside the family (Townsend, 2009). The social behaviour of the American Crow is called cooperative due to the fact that older siblings help raise and feed the young (Gade, 2010; Tarter, 2008; Townsend, 2009). These older siblings are known as auxiliary birds. A typical family consist of 2 breeders, 0 to 5 auxiliary birds and 2 to 5 juveniles/young (Tarter, 2008). This means that a family can potentially have more than twelve related birds from previous broods (Townsend, 2009; Yorzinski et al., 2006). During nesting, family members are faced by many challenges such as feeding and predator attack (Chamberlain & Cornewell, 1971; Yorzinski et al., 2006). At the end of the nesting season, crows aggregate into a large roost until the next breeding season (Townsend, 2009; Yorzinski et al., 2006).
The American Crow is recognised for its vast vocal repertoire with more than 20 different calls and sounds (Chamberlain & Cornwell, 1971). The common calls or caws are divided into short and long calls (Tarter, 2008). The short call is a high pitch with a short duration of 200 milliseconds. Short calls are usually executed in a fast interval of 2 to 10 successive repetitions (Tarter, 2008). The long call is of 300 milliseconds and is different from the short call by its audible roughness (Tarter, 2008). Both short and long calls are commonly used for attention and communication between American Crows during the day (Chamberlain & Cornwell, 1971).
Hear the difference between the short and long call in this recording of both calls from the Morgan Arboretum, Qc, Canada:
The warning calls are also of short duration but are more rapid than short calls. Warning calls can be executed in several saccades of 3 to 6 repetitions (Chamberlain & Cornwell, 1971). Moreover, the warning call is generally sharper than the short call and can occur at anytime of day or night (Chamberlain & Cornwell, 1971). The American Crow will vocalise the warning call usually in the presence of a predators, hunters or startling sounds (Chamberlain & Cornwell, 1971).
In addition to the warning call, the American Crow can mob predators in order to make them leave using the mob call (Chamberlain & Cornwell, 1971). Crows mob in group during the daytime by vocalising a cacophony of warning calls of different length and roughness (Chamberlain & Cornwell, 1971; Tarter, 2008). The group members are always ready to attack an approaching crow that they cannot identify. In that situation the calls resulting from the altercation are named fighting calls (Chamberlain & Cornwell, 1971).
A recent study by Yorzinsk et al. (2006), suggests that crows are able to differentiate individuals and sex in function of warning call. Call frequency is one of the critical components for discriminating individuals (Yorzinsk et al. 2006). For instance, females American Crows have shorter and more frequent warning calls than males (Yorzinsk et al. 2006).
Among specific calls, the feeding or hunting calls are emitted before a meal or as a begging call by a hungry nestling (Chamberlain & Cornwell, 1971; Tarter, 2008). Feeding calls resemble long calls in that they are of long duration but the “aw” part of the “caw-aw” sounds like a cry or complain (Chamberlain & Cornwell, 1971).
Crows.net has excellent examples of feeding calls: http://www.crows.net/analysis.html
Rattles are in a different group of vocalisation emitted by the American Crow that does not comprise the “caw” note (Tarter, 2008). Rattles are produced in several situations such as feeding, mobbing and when a predator is seen (Chamberlain & Cornwell, 1971; Tarter, 2008). The American Crow is also able of vocalising many other notes (Chamberlain & Cornwell, 1971). The American Crow has the ability to mimic sounds in its environment like a crying children, other birds call and even human voice to some extend (Chamberlain & Cornwell, 1971).
Here is a link to good examples of rattle and typical caws:
Here are additional typical calls:
A.O.U. (1998) Passeriformes: incertae sedis mimidae. The AOU check-list of North-American birds, 7th edition, pp. 449-450. The American Ornithologists’ Union.
Caffrey, C. (2000). Tool modification and use by an American Crow. Wilson Bulletin, 112, 283-284. doi: 10.1676/0043-5643(2000)112[0283:Tmauba]2.0.Co;2
Chamberlain, D.R. & Cornwell, G.W. (1971). Selected Vocalisations of the Common Crow. The Auk, 88, 613-634. doi: 10.1111/j.1095-8312.2010.01527
Gade, D.W. (2010). Shifting Synathropy of the Crow in Eastern North Amercia. Geographical Review, 100, 152-175. doi: 10.1111/j.1931-0846.2010.00019.x
Tarter, R.R. (2008). The Vocal Behaviour of the American Crow, Corvus Brachyrhynchos. Master of Science, Ohio Sate University, Ohio, (US). Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1204876597 (osu1204876597)
Townsend,Andrea K.; Clark,Anne B.; McGowan,Kevin J.; Lovette,Irby J.(2009) Reproductive partitioning and the assumptions of reproductive skew models in the cooperatively breeding American crow, Animal Behavior, 77, 2,
Yorzinski, J.L., Vehrencamp, S.L., Clark, A.B. & McGowan, K.J. (2006). The Inflected Alarm Caw of the American Crow: Differences in Acoustic Structure among Individuals and Sexes / El Llamado Declinado de Alarma de Corvus brachyrhynchos: Diferencias en la Estructura Acústica entre Individuos y Sexos. The Condor, 108, 518-529. doi: 10.1650/0010-5422(2006)108[518:TIACOT]2.0.CO;2