“If a person knows only four birds,” wrote Edward, Forbush, “one of them will be the crow.” Forbush set down that opinion 60 years ago, but it is still true. Big, ubiquitous, and noisy, crows make their presence felt from the remotest wilderness to the busiest city.
In Chicago they nest in the larger parks, in cemeteries, along the river, and in forest preserves. Their numbers seem to rise in the winter as the local birds are joined by others fleeing the icy climes of Wisconsin and points north. Christmas bird counts in the city run up totals in excess of 1,000 birds, and the Waukegan Christmas count holds the record for the region with a count in excess of 10,000. It is likely that there are more crows in North America now than there were 400 years ago
Their success comes in the face of the urbanization of the continent and despite massive persecution by humanity. Crows have thrived amid these radical changes for much the same reasons as people. They are smart. They are adaptable. They are able to eat almost anything.
Crows belong to the family Corvidae, a group that also includes ravens, jays, magpies, and the Old World jackdaws and rooks. The family is part of the giant order of passerine birds, otherwise known as songbirds, a group that includes about half of the world’s birds. Weighing about a pound and having a wingspan of up to 40 inches, crows are among the largest birds in this huge group.
Our local crow, Corvus brachyrhynchos, ranges over the United States and the southern two-thirds of Canada. It has some close relatives. The fish crow lives along the Atlantic and Gulf coasts. The northwestern crow lives along the Pacific coast from southern Alaska to Washington. The Mexican crow was unknown in the U.S. until the 1960s when it moved into the lower Rio Grande Valley. This bird has made the city dump in Brownsville, Texas, into a place of pilgrimage for serious birders because it is one of the few places the species can reliably be found on this side of the border. Serious birders want the species on their U.S. lists, so crossing into Mexico to see it just wouldn’t count. These various crows are all big black birds distinguishable only by call and range.
Here in Chicago, you can always find crows at the Lincoln Park Bird Sanctuary at Addison and the lake. They nest there regularly, and sometimes the nests are visible from outside the fence that surrounds the sanctuary.
Crows are very wary of close approach, a fact that has contributed to their reputation for intelligence. As Forbush put it, “His judgment of the range of a gun is too nearly correct. If crows could be shot oftener they would be more popular.”
Out in the country, they make part of their living scavenging on the various animals that have been flattened on the highways. But despite their need to spend long stretches of time on the pavement, I have never seen a crow dead on the road. They always get out of the way of approaching traffic, even when it is moving 70 miles an hour.
Farmers have traditionally hated crows because the birds eat sprouting grain, and in the days when chickens were allowed outdoors, they would raid poultry yards in search of eggs and young chicks.
Beginning around the turn of the century, the Department of Agriculture began a careful study of the eating habits of Corvus brachyrhynchos, shooting large numbers of crows in all parts of the country and at all times of year and cutting open their stomachs and crops for minute examinations of the contents.
The number of different kinds of food items discovered by this process totalled 608. Crows eat insects of all the larger sorts, as well as spiders and millipedes. They will pluck crustaceans, frogs, and salamanders from the water’s edge and raid the nests of all birds save the biggest and fiercest to take eggs or young. They will pull clams or mussels from shallow water and carry them aloft and drop them on rocks to shatter the shells and release the meat. They scavenge on anything dead, whether a field mouse or a cow, and they will rummage through a Dumpster in an alley to grab whatever humans have discarded.
On the average, plants make up about three-fourths of their diet. They eat all sorts of wild and domestic fruits and seeds from almonds to poison ivy.
The official conclusion of the USDA was that while local control measures were sometimes justified, crows were, on balance, at least as beneficial as they were harmful. A flock of crows foraging through a field of young corn are as likely to be eating the grubs of harmful beetles as sprouting plants, so you need to consider killing them with some discretion.
This advice was usually ignored. For decades, every man’s hand was turned against the crow. Hunters killed them whenever they could get close enough because they didn’t like the crow’s habit of eating ducks’ eggs and young. Farmers, with help from the U.S. Fish and Wildlife Service and various state agencies, even used dynamite to attack crows.
During the breeding season, crows usually live in small family groups, but in winter they may gather by the thousands in huge roosts. Bombing these roosts became a standard method of crow control. For example, in Collingsworth County, Texas, in April of 1937, 180 sticks of dynamite were placed in a crow roost during the day when the birds were out feeding. The sticks were scattered around the roost, but connecting wires allowed them to be set off in large batches.
When the birds returned and settled down for the night, the first blast, 60 sticks in all, killed an estimated 40,000 birds. A second blast of the remaining 120 sticks did in a similar number.
The Illinois Department of Conservation even made the pages of Life magazine in 1940 when it used clusters of dynamite bombs to slaughter 328,000 crows in roosts near Rockford.
Crow killing is one of those perfect patronage jobs. No matter how many you kill, there are always more, so you don’t have to worry about putting yourself out of work. And if you prefer sleeping late or working your precinct to murdering crows, your absence won’t make any difference either.
The crow’s reputation for sagacity is mainly based on anecdotes, but there are so many anecdotes that it is hard to ignore them. We do have evidence that they can count to four. This was discovered in a series of experiments performed on a pair of crows that were nesting on top of an unused building. If a human entered the building, the crows would fly off to a nearby tree and wait for him to leave before returning to the nest.
If two humans entered and then left one at a time, the crows would wait until the second person left before returning. They had a similar reaction with three or four people, but if five entered, they would return after four left. These experiments taught us that crows can count to four and also answered the age-old question, how many ornithologists does it take to fool a crow?
Back in 1913, a Harvard psychologist named Charles Coburn, a true ancestor of B.F. Skinner, set up a series of experiments that proved that crows could distinguish between various shapes–circles, squares, triangles, hexagons–as well as between similar shapes of different sizes. In one test, a pair of crows learned after only one trial to distinguish a five-centimeter circle from a four-and-a-half centimeter circle. I’m not sure I could do that well.
Coburn’s biggest problem was getting the birds to cooperate, especially since, as a founding behaviorist, he had his crows working their way through a maze set up in a series of small dark boxes. Crows have more sense than to willingly enter small dark boxes, so Coburn spent the first two months of his project overcoming this reluctance by forcing them to enter the boxes to get something to eat.
Since Coburn didn’t test any other birds, we cannot say how pigeons or robins or mallards would do in similar experiments.
In the end, the best evidence of the crow’s intelligence lies in its ability to thrive despite the changes that have overtaken its life in the past couple of centuries, and that ability accounts for much of the delight we take in seeing them soaring above city streets.
Thoreau said it very nicely: “This bird sees the white man come and the Indian withdraw, but it withdraws not. Its untamed voice is still heard above the tinkling of the forge. It sees a race pass away but it passes not away. It remains to remind us of aboriginal nature.”