Crows: The Bad Boys of Birding
By Kathy Bernhardt
Crows are the victims of a lot of bad press. Deemed nuisance birds, destructive to crops and exceptionally messy in large groups, they have been persecuted and hunted for hundreds of years. Even our language treats them with disdain. The expression "to eat crow" means to do something disagreeable. To "crow" is to brag obnoxiously. Wrinkles around the eyes are called "crows-feet." A flock is known as a "murder" of crows. Their cousin, the raven, spawned the word "ravenous", meaning extremely hungry or greedy, and "ravage", meaning to destroy or plunder.
It is true - crows are known as scavengers and opportunists. They will eat just about anything that doesn't eat them first. Crows are also exceptionally curious, observant, sociable, cooperative, resourceful, intelligent, and successful. And their undiscriminating taste often makes them a farmers best friend.
For instance, a New Jersey farmer hired marksmen to stand in his field and shoot the crows that landed on his asparagus field each morning. They shot the crows, but the asparagus didn't grow. After careful investigation, the farmer discovered a cutworm infestation. When the crows were allowed to return to the field, they resumed their cutworm feast and the farmer harvested his asparagus.
Crows do go after crops such as corn when the plants first sprout, and then again as the ears ripen. (Unfortunately, scarecrows don't live up to their name after the first few days of service.) But, as described by researcher Arthur Cleveland Bent, crows actually benefited the crops of corn farmers in early spring by eating thousands of white grubs and cutworms. Gathering the bodies of crows shot by farmers, it was shown their stomach contents consisted of 1% corn and other crops and 99% insects and carrion, but convincing farmers of this has been difficult. Some states continue to practice extensive control efforts, sometimes dynamiting winter roosts and killing tens of thousands of birds. And most states issue licenses to hunt crows.
Members of the family Corvidae, which includes jays, magpies and ravens, crows are one of the most widespread and adaptable of birds. They are in practically every part of the world except New Zealand. Found from Canada to Baja, New York to California, the American Crow -- or Common Crow -- is one of the widest spread and most easily recognized birds in the United States. A large, 17 to 21 inch, chunky bird with glossy solid black plumage and beak, they are comfortable in woodland, farmland, orchards, tidal flats and, because of their ability to tolerate human disturbance, in most city neighborhoods. About the only place they do not occur is in the hot, dry desert. Crows roost in large winter flocks and can be seen in the early evenings congregating in loud, small groups to join the ever-increasing flocks flying to the nighttime roost. Some winter roosts number in the tens of thousands.
Crows mate for life, although adultery is not unknown. Paired male and female crows share in the incubation of four to six eggs which hatch in eighteen days. Both parents feed and care for the young, with help from previous year's youngsters. These "helpers" assist in the raising of new nestlings by bringing them food and guarding the nest. Youngsters first fly when they are about one month old, but often stay with their parents for up to three years. Nestlings may also benefit from the care of other nonbreeding crows around the nest. This cooperative breeding approach distinguishes the crow from most birds, and is believed to be a sort of apprenticing of youngsters learning how to be parents. Or, perhaps, they are freeloading, bumming food off productive parents and doing just enough chores to keep from getting kicked out. Or it may be that in really lean years, the helpers make a crucial difference in survival. The truth is probably all three.
Crows' nests are rather sloppily built, and don't hold up well in high wind and rain. Sometimes crows return and reuse nests, and very often they will continue to nest in the same tree or adjacent trees for many years, usually making a new nest. Sometimes old crow nests are used by owls for the basis of their nests. Hawks also have been known to inhabit a crow nest. Squirrels use them for summer napping platforms.
Crows have a big fan club as well as well as a large number of critics. Admired for their intelligence and tenacity, they also have a reputation for destroying gardens, farm crops and the nests of other birds. Corvids can and do eat almost anything. Their diet consists of insects, carrion, small rodents, bird eggs, nestlings, seeds, fruit, and nuts. Crows eat young nestlings and eggs for the same reason that robins snap up worms; all birds have increased energy requirements during the breeding season, and crows are no exception. Crows often cache food in trees and in the ground and are known to retrieve caches up to several months later. They've been seen dropping walnuts and mollusks from heights onto rocks to break them open; and have been observed stealing food from hawks and owls they have mobbed from their territory.
Crows chase hawks and owls for the same reason that mockingbirds chase crows: to purge their territory of a potential predator. Crows especially hate Great Horned Owls, their main predator, and take particular delight in harassing these hapless raptors as they nap during the day, often calling in friends to participate in the chase. The few predators that crows, especially fledglings, might face (besides unfriendly humans) are raptors. Adult crows often participate in a behavior known as mobbing, in which they drive the threatening bird out by chasing it en masse. This may also be a means of demonstrating to young crows "this is what trouble looks like."
In turn, the sight of a crow near a songbird's nesting territory makes the occupants pretty nervous and quite defensive. Songbirds mob crows as a preventative measure, but also in retaliation, if they spot the crow fleeing the raided nest.
Crows have the largest brain capacity to body size of any North American bird. Their intelligence and curiosity often result in play-like activity. Their ability to solve problems and remember those solutions are well documented. In one Moscow study, a crow was presented with a row of caps with food hidden under the first cap. Once it found the food, by trial and error, it was again presented with the caps, with food under the second. Again, the crow found the food, and again, presented with the caps, with the food under the third. By the fourth time, the crow went directly to the next cap in the row, irrefutable evidence of a highly evolved learning ability.
Compared to other birds, the math skills of crows are considerable - they can count at least to three or four, possibly as high as seven. They are known to craft and use their own tools, and have extensive proficiency in locating the four-taloned discount. In fact, they specialize in pilfering. Anyone who has left a shiny key or bracelet outside in crow territory can attest to that.
"You get the feeling that they notice little details," said Cornell University crow expert Kevin McGowan. Since he started handing out peanuts to appease the birds he studies, he's been followed all over by crows that spot his Toyota with the ladder on the roof. "They seem to think and learn and change their behavior accordingly. They are the most human-like of the birds around us."
Crow behavior sometimes borders on the unbelievable. For instance, an ice fisherman reported that a group of crows, after watching human fishermen pull fish through holes in the ice, started doing the same when the fishermen retreated to their shack for coffee. The crows took the line in their beaks and backed up, then walked on the line up to the hole and repeated the behavior until the end was on the ice. They then devoured the fish or bait they found on the hooks. In Virginia, a murder of crows was implicated in a milk scandal. Upon retrieving their milk from the porch, people found the bottles opened and the cream gone. After careful watching, a neighbor reported seeing crows follow the milkmen on their deliveries, pry the paper lids off the bottles and help themselves to breakfast.
One observer told of watching a crow solve a tricky problem. The bird had found a pile of berries of varying sizes. Probably with hungry nestlings to feed, it attempted to carry the berries away. Repeatedly it picked up the berries in various size combinations. Finally satisfied, the bird took off with all the berries. It had stacked the treats in its beak in descending order of size, smallest in back, largest at the tip.
Crows also have a wicked sense of humor. There are many stories of crows snipping clothespins off lines just to watch the clean sheets fall to the ground. Others like to undo shoelaces. One group of ravens in Alaska was observed repeatedly climbing to the top of a sloped, snow covered roof and sliding down, with apparent delight, on their rears.
And yet the cerebral tendencies of crows have not impaired their sociability one bit. While melody may not be the crow's strong point, the crow vocabulary numbers more than 20 different vocalizations. They have their own, highly evolved language and society. They live in close-knit families of at least nine birds. The leader acts as a lookout, stationing himself at the top of the tallest tree while others forage or attend to other crow business. The leader uses a wide repertoire of calls to alert his family to different situations.
A scolding call warns of an approaching predator, such as a fox or an owl; a rallying call means that the predator is closing in; an assembly call is sounded when it's time to mob the enemy. There is also a dispersal call, the crow equivalent of "Scatter!"
Crows are classified as migratory birds, although few migrate more than from one neighborhood to another, and therefore are protected by federal law. Unless one has a federal permit (these are difficult to obtain), it is illegal, a criminal offense, to keep a crow or raven. These laws have a rational basis -- to keep people from buying or selling native birds in pet shops, as was once a common practice. Also this protects birds from idle, would-be pet keepers whose intentions are good, but are so lacking in expertise that they end up abusing the animals. An adult crow, or even young ones past the imprinting age, are among the most difficult of creatures to "tame." They remain hostile and frightened no matter how much care is lavished. People who come upon an infant or injured adult crow, in fact, upon any wild animal or bird, should take them to a licensed rehabilitator. Rehabilitators, by law, cannot charge for their services.
Henry Ward Beecher, an eminent 19th-century American preacher and naturalist, once said that if human beings wore wings and feathers, very few would be clever enough to be crows.
And any crow could tell you that is true.
Sources: Angell, Tony. Ravens, Crows, Magpies and Jays. Seattle: University of Washington Press, 1978.
Bent, Arthur Cleveland. Life Histories of North American Jays, Crows and Titmice. New York: Dover P