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The American Crow

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).

Typical spectrogram representing 4 short calls. (Recorded at the Morgan Arboretum, Qc, Canada on October 17, 2012).

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).

Figure 2: Spectrogram representing calls from two American Crows responding to each other. Note that the vertical peak represent one individual and the leaned-back peak is another individual. (Recorded at the Morgan Arboretum, Qc, Canada on October 17, 2012)

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:

http://www.allaboutbirds.org/guide/American_Crow/sounds

Here are additional typical calls:

___________________________

References

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,
503-512

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

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About Crystal Ernst

Hakai Institute postdoctoral scholar at Simon Fraser University (B.C.)

27 comments on “The American Crow

  1. hi

    i’m very curious to know how can one differentiate a young crow from an adult crow?

    thank you in advance

    Sam

    • Young crows have bright pink mouths that darken with age, and blue eyes (which also darken rapidly). Additionally, younger birds have pointed tail feathers whereas, older birds have tail feathers which are more squared off..

  2. Very interesting! Discovered new aspects on the American Crow, that I had not think about before; like their strong social relationships and how they have such a variety in their way of communicating! Crows are very present in North American and can sometimes be perceived as mysterious and un-attractive birds, but oh so intelligent 🙂

  3. First, thank you for your comment!
    Beside being of smaller size, young crows have blue eyes until they reach sexual maturity and then their eyes turn black/brown! First year crows also have less abundant feathering with less shine than adults.
    If you have any other questions, let us know!

  4. I really like the fact that I could listen to the crow typical calls. I will try to be careful now when I listen to birds calls and try to identify the crow’s. Distinguishing birds from their calls is quite difficult, but having to samples here really helps getting the particularities of this bird. Plus, I found this article was really easy to read and full of pertinent information!

  5. Excellent work. Wondering if anyone has looked at fluctuations in American Crow populations since introduction of West Nile Virus over 10 yars ago, particularly in St. Lawrence Lowlands.

    • Thank you for the encouragement!

      A paper published in Nature by LaDeau et al. (2007) showed the fluctuation of different bird species population across the United States. Their findings show that the American Crow population did deacrease since the introduction of the WNV.

      Here is the full reference: LaDeau, S. L., Kilpatrick, A. M. & Marra, P. P. (2007). West Nile virus emergence and large-scale declines of North American bird populations. Nature, 447(7145), 710-713. Doi 10.1038/Nature05829

      We did not find (yet) any papers evaluating the Quebec population of the American Crow. However, Ludwig et al. (2010) eveluated the risks factorsassociated with WNV mortality in the American Corw population in Southern Quebec (St Lawence lowlands). They suggest that second year crows are the main propagator of the WNV.

      Here is the full reference: Ludwig, A., Bigras-Poulin, M., Michel, P. & Bélanger, D. (2010). Risk factors associated with West Nile Virus mortality in American Crow population in southern Quebec. Journal of Wildlife Diseases, 46(1), 195-208.

      Moreover, the Public Health Agency of Canada and the Canadian Cooperative Wildife Health Centre make report every year on the WNV. In 2012, 43 American Crow where tested in Canada and 10 positive for WNV where from Quebec. In 2011, out of the 38 American Crow tested, 14 WNV-positive were from Quebec. The surveilance map also indicate that most of WNV positive cases occur in southern Quebec and eastern Ontario. Have a look at their data, they are very interesting and useful.

      CCWHC: http://www.ccwhc.ca/wnv_report_2012.php

      Public Health Agency of Canada: http://www.phac-aspc.gc.ca/wnv-vwn/index-eng.php

    • We found an interesting paper by Ludwig et al. (2009) showing that the normal dynamic in the crow population in Quebec changed in 2003. In 2003, the normal crow population fluctuation changed due to the West NIle Virus.

      Here is the full reference: Ludwig, A., Bigras-Poulin, M. & Michel, P. (2009). The Analysis of Crow Population Dynamics as a Surveillance Tool. Transboundary and Emerging Diseases, 56(9-10), 337-345. doi: 10.1111/j.1865-1682.2009.01090.x

  6. Nice – I like how you guys are incorporating different media into these posts (call recordings in this one, video in the last one about beeches).

  7. Really interesting! Now, i’ll see the American Crow differently!

  8. Good and well prepared article! I enjoyed hearing the diffrent crow sounds, this was new to me. I also have a question: their used to be one big roost in which they aggregate in order to wait for the next mating season near my home, and I have not heard it for a while now. The roost location is not the same year after year?
    Thanks!

    • Usually the American Crow do roost around the same area every year. Maybe construction or predators forced the crows to move to more a undisturbed area. Another plausible explanation is that the roost might have been divided by the west nile virus (WNV). Clark et al. (2006) showed that the death of family members from WNV forced other members to move away into other family groups and new territories. Like in your case, some territories remained empty for a while because neighbouring crows “know” that these territories belong to other families and the neighbour do not realize that these families left.

      Here is a summary: http://www.birds.cornell.edu/Publications/Birdscope/Autumn2007/virus_disrupts.html

      Here is the complete reference: Clark, A. B., Robinson, D. A., & McGowan, K. J. (2006). Effects of West Nile Virus Mortality on Social Structure of an American Crow (Corvus brachyrhynchos) Population in Upstate New York (Vol. No. 60): American Ornithologists’ Union.

  9. The crow looks very similar to the raven…how do you tell them apart?

    • If you can see them up close you can notice that the raven is relatively larger than the crow, 63cm vs 48cm long. Raven also tend to have a shaggy collar whereas American crows have a sleek one and the raven have a larger and thicker bill than the crow. If you want to identify them at flight you need to look at the tail shape, the ravens tail feathers are spear shaped while the crows are fan shaped.
      Hope this answers your question!

  10. Are there cases where crows aren’t monogamous? What if a partner dies?

    • I general the American Crow is monogamous. However, in rare cases when a major disturbance occurs in their habitat, some pairs break up and each individual integrates another family territory. Otherwise, the male or female will usually find another mate if their partner dies and this occurs rather frequently in areas of high West Nile Virus infection where many pairs are broken by death due to the West Nile Virus infection.

  11. Our west coast home is under flyover for crows and we love them. They are so bold and raucous and social! I heard that insects and animals have to “speak” louder due to noise pollution? Are crows in urban cantres noisier than ever?

    • Unfortunately, we were not able to find any articles yet on the specific “loudness” of the American Crow in urban versus rural areas. However, calls varies depending on the sex and size of the crow and it was proved that the crows in urban areas are larger in size than those in rural areas due primarily to all the human waists available (garbage!). Thus, it is very possible that the crows in cities might be louder than in the forest but we cannot confirm or tell you to which extent. We will keep you posted if we find anything new that relates to that!

      Here is the reference on the article on the differences in vocalisation between different American Crow individuals:
      Yorzinski JL, Vehrencamp SL, Clark AB, McGowan KJ. 2006. The inflected alarm caw of the American Crow: Differences in acoustic structure among individuals and sexes. Condor. 108(3):518-529. Doi 10.1650/0010-5422(2006)108[518:Tiacot]2.0.Co;2

      Here is the article on the size of the American Crows raised in urban versus rural areas:

      Heiss RS, Clark AB, McGowan KJ. 2009. Growth and nutritional state of American Crow nestlings vary between urban and rural habitats. Ecol Appl. 19(4):829-839. Doi 10.1890/08-0140.1

  12. Is a flock of crows really referred to as a “murder” of crows?

  13. I live on the west coast in Victoria and walking to work yesterday I realized that I have not heard crows for quite some time. In September they were in big noisy groups but now seem to have disappeared. Do you think they have moved or are they just leading quieter more singular lives now that it is winter?

    • It is true that bird in general and other animals are “quieter” in winter because they try to minimise their energy expense when the temperature cools down. It is also possible that they moved into another area more suitable for wintering. American Crows aggregate into large roost in the fall and winter and tend to go back to the same roosting area every winter. Perhaps, the food became less available in you area and they decided to all move to an area with more food or sometime when the temperature is very cold they will move a little south into the United States.
      Does this answer you question?

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