The American Crow is a distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They are 16-20 inches in length, of which the tail makes up about 40%. Each wing is around 7-8 inches long. The bill length is on average 2 inches, varying strongly according to location.
The most usual call is a loud, short, and rapid caah-caah-caah. Usually, the birds thrust their heads up and down as they utter this call. American Crows can also produce a wide variety of sounds and sometimes mimic noises made by other animals, including other birds.
American Crows are monogamous and cooperative. Mated pairs form large families of up to 15 individuals from several breeding seasons that remain together for many years. Offspring from a previous nesting season will usually remain with the family to assist in rearing new nestlings.
Outside of the few months of the breeding season, Crows are extremely gregarious. After the last young have fledged, the family group usually joins other groups of Crows, and these begin to form a large flock that divides up for feeding during the day, but gathers again each night to roost. The roost becomes an important focal point in the birds’ life outside the breeding season.
Each morning the roost breaks up into smaller flocks that disperse across the countryside to feed. Some flocks may fly up to fifty miles from the roost each day. In midafternoon these smaller flocks start back toward the communal roost. They fly along fixed flight lines used each day and are joined by other flocks as they go. Often there are preroosting sites, where flight lines coincide and Crows stop to feed before making the final trip to the roost.
At these spots there may be much chasing and often spectacular dives as the returning Crows join the others at the preroosting spot. Then just before dusk all the Crows in the area enter the roost site together. These last flights into the roost can be spectacular, for they may contain anywhere from a few hundred to a few hundred thousand birds. The largest roosts are where birds migrating from the north come together with local, year round residents.
Crows are smart and adaptable. For example, they drop nuts on streets so cars run over them, then wait for the traffic signal to change so they can pick up the food. Other crows who see this happen quickly learn how to do this for themselves.
Technology hacker Joshua Klein has been studying crows for over ten years and has learned that they are very intelligent. He has distributed a video of how a crow learned to use a tool to pull an object out of of a tube with a bendable wire.
Joshua built a vending machine that teaches crows to deposit coins they find into a special vending machine that dispenses peanuts. His machine uses Skinnerian training. He put coins and peanuts around the machine. The crows ate the peanuts on the feeder tray. Then Joshua took away the nuts and left coins in the feeder tray. The crows gathered the coins around with their beaks, looking for food. When a coin accidentally dropped into the slot, it dispensed a peanut. Next, Joshua took away the coins. The crows learned to find coins elsewhere and deposit them.
Anecdotes of crows birds snatching up shiny human valuables are plentiful, and many of them are undoubtedly true. Watches freshly removed in the outdoors are a favorite. They are certainly capable of detecting shiny and colorful items. But in all these cases, the items are probably perceived as potential food. It is likely that the shape of the object is more important than its color and brightness.
Detailed reports from people who have raised crows in captivity provide some telling clues. A classic 1927 report comes from Norman Criddle of Manitoba, Canada, who raised four young crows. He reported that they regularly collected a wide variety of objects together and then hid them. When they became older, they regularly hid food items for later eating, including shoving berries under a handkerchief in Criddle’s own front shirt pocket.
This tallies with modern observations that young birds aren’t sure of the food value of all the various items they see day to day, so they hide some to experiment with later. It is quite likely that many of shiny object theft reports are the work of young birds experimenting with possible food.
Bernd Heinrich, a University of Vermont biology professor, got even more detailed information in his work with young crows. He was intrigued when he gave them an egg and they immediately attempted to eat it, even though they had never seen one before. Presenting crows with objects, both edible and inedible, of various shapes, he found they would faithfully attempt to eat any smooth rounded object, including hickory nuts, a ping pong ball, film canisters and a red and white fishing float.
He also experimented by secretly burying a piece of roadkill they liked in different places under snow. He found they used visual cues in the disturbances of the snow rather than smell to find the roadkill again. This shows sight is critical to the birds’ food-finding. Our small valuables such as coins, rings, and watches tend to be smooth and rounded. It’s likely the birds simply consider them a meal, and dump them later when it’s clear they’re not.
American Crows are protected internationally by the Migratory Bird Treaty Act of 1918. Despite attempts by humans in some areas to drive away or eliminate these birds, they remain widespread and very common. The number of individual American Crows is estimated to be around 31,000,000. The large population, as well as its vast range, are the reasons why the American Crow is considered to be of least concern, meaning that the species is not threatened.