3 March 2015
Capable of using tools to obtain their food, remembering the faces of humans and predators, and communicating to others around them, crows are widely believed to be the most intelligent birds on the planet. Besides this intelligence, crows have gained an important reputation for being able to survive in many ecologically diverse habitats such as fields, woodlands, forests, farming sites, towns, neighborhoods and cities around the world. This and the crow’s ability to travel far distances, as well as their omnivorously diverse diet, has helped crows to maintain stable and growing populations, even as human interference and adversity continues to affect them time and time again.
Current ecological research has shown that crow populations have slightly increased from 1966 to 2010 and that the global breeding population is at 27 million. A fairly recent, and very deadly virus called the West Nile Virus, has been responsible for many recent crow deaths and has accounted for killing 45% of American Crows since 1999. Virtually all crows who come in contact with this virus die within the first week, with very few survivors. Even with these dangerously high numbers of crow fatalities, the International Union for Conservation of Nature still lists them as a species of least concern. With this growing virus epidemic however, it should be of major importance to focus on protecting these crows before their populations begin to decline and the virus is too rapidly spreading to stop.
Although large crow roosts and close contact with one another can be dangerous with the spread of the West Nile Virus, it is also fundamental in crow’s success and natural social behavior in order to benefit and enhance their daily lives. These crows usually spend this time together while roosting in very large “murders” (crow flocks), which can range from hundreds to thousands and even sometimes to the hundreds of thousands during the Winter months. Crows take this time to socialize, to forage for new types of food, and to drive off predators (known as mobbing). When they're not roosting, crows often stay together in year-round family groups, which consists of the breeding pair and their offspring from the past two years. Everyone in these families participate and cooperate in raising the younger crows.
Probably the most important phase in the crow’s lifetime is reproduction. In order for these crows to reproduce, they must build nests in order to accommodate the needs of their young. Both members of the breeding pair build the nest, which is made largely by medium-sized twigs with an inner cup lined with pine-needles, weeds, soft bark, or animal hair. Nest sizes are typically 6 - 19 inches across, with an inner cup about 6 -14 inches wide and 4 -15 inches deep. Crows will usually build their nests in trees, however there are many occasions where crows build their nests in neighborhoods, towns and cities on human made structures such as buildings, power lines and lamp posts. To build such nests on these structures, crows use man-made objects to construct these complex designs.
Something which has fascinated and proven to humans how intelligent crows truly are is how they are able to recognize human faces from a bird’s eye view and from very far distances away, and more importantly, communicate these human faces to other crows. Even more intriguing, these adult crows will later pass this human facial recognition on to their offspring, so that they also know to avoid these threats. In addition to knowing these threats, crows also use different forms of vocalization for different threats.
Over time, crows have become very ecologically diverse throughout North America and the rest of the world. This diversity has allowed them to continue traveling all around North America, even as human civilization and industry expands rapidly. Some major advances to crow livelihood came from American agriculture during the 1800’s and 1900’s. Corn and other grains became a common food choice amongst most crows and this large abundance of food helped to grow crow populations significantly.
With such a diverse diet, methods to eating hard to crack foods must be found. Nuts and small turtles for example, cannot be eaten in their shells, so many crows have adapted to dropping these foods from high altitudes and then fetching them as they hit the ground and break. Other, much more modern methods discovered by crows, involve placing these shelled foods in front of cars on streets and waiting for the cars to smash them, to which the crow takes great delight in eating afterwards. These new methods of eating uncommon foods are essentially important in understanding crow intelligence and how they will continue to find new solutions to every problem they encounter.
Throughout this ecological research of crows, I have learned and come to understand many important and fascinating things about crows who live in many different ecological habitats and deal with many different ecological factors all the time. It is important that I can inform others about these crows and also point out their true importance in the natural world.
I am from Redmond, Washington and am currently attending the University of Washington in Bothell. As a first year student, I am currently working towards getting my credits and the necessary prerequisite courses in order to attend the School of Business here are UWB and to eventually get a degree in Business. I am enjoying my first year here so far and look forward to continuing my education at UWB.
Photo credits: all by S. Offeman
The Cornell Lab of Ornithology, All About Birds, American Crow [Internet]. [Cited March 5, 2015]. Available from:
KCTS 9, Nature, A Murder of Crows, Crow Facts [Internet]. c February 21, 2013. [Cited March 5, 2015]. Available from:
Scientific American, Crows Show Off Their Social Skills [Internet]. c August 8, 2013. [Cited March 5, 2015]. Available from:
Marzluff M John. 2007. In the Company of Crows and Ravens. [Cited March 5, 2015]. Yale University Press.