As the crow flies: changing land use patterns are fueling the flight to inner-city roosts

You have to get up pretty early in the morning to fool a crow. John Withey, a Ph.D. candidate monitoring a roost in Seattle, gets up before dawn. As part of a larger study of the increase in the city's crow population, he sets his traps in the dark and places camouflaging around the wire that trips them. When he succeeds in trapping one of the crafty birds, he bands it and clips a piece of feather for a DNA sample before releasing it. But if he arrives too late, the crows will see what he is doing and will not take the bait.

In California crows have been observed dropping nuts onto roadways and waiting for traffic to run over and crack them open. Gavin Hunt, studying crows on New Caledonia, a French island 700 miles east of Australia, has seen them fashion two distinct tools to impale and extract invertebrates from tree crevices. And the birds have an impressive memory, too, which helps them find food caches months after they've hidden them.

Intelligent, inquisitive, highly social, and chatty, the bird has grabbed a growing foothold on America's urban scene, to the delight of some and the annoyance of others.

Urban crow populations across the country have climbed steadily for the past 30 years. Albuquerque has seen a population increase of 425 percent; Hartford, Connecticut, 187 percent; and Seattle, where an inner-city roost has boomed to more than 9,000 birds, 57 percent. About 160,000 crows live in Chatham, Ontario, outnumbering humans four to one, and a single roost of 50,000 crows is located in Auburn, New York. The Boston area's largest roost, a moveable party generally found and in the neighborhoods of Brookline, Newton, and Brighton, peaks in winter at about 5,000 birds.

Biologists say the rise stems directly from human activities. As with Canada geese, we have created safe, food-rich havens for crows. Grassy lawns provide nutrient-rich worms and insects. The birds easily glean delicacies such as French fries, Cheetos, bread, and hamburgers from open garbage cans, dumpsters, and the leftovers of sloppy picnickers. In addition, crows find good nesting spots in the open, tree-filled landscapes that dominate metropolitan areas.

According to Kevin McGowan, a crow researcher at the Cornell Laboratory of Ornithology, the boom in crow numbers has occurred mostly in western and mid-western settings. In the East, it's more a matter of shifting population densities. Crows are moving away from agricultural landscapes to select suburban and urban areas, where they find fewer predators, such as great horned owls, red-tailed hawks, and goshawks; plentiful food; and good nest sites. These advantages combine to produce higher nest success and better one-year survival prospects for chicks.

In the western United States, sprawl is the main factor driving crow populations up, with development carving out new, crow-friendly habitat. Researchers have found that these new suburbs feed the population rise in western cities. Because adult crows are territorial, juveniles born in the suburbs initially cannot find a home near their parents. So they head to the city. They hang out with other young birds, often forming large winter roosts, but eventually, when habitat modification makes new territories available to raise a family, these young crows move to start the cycle again. "I call it the young urban crow, or YUCKIE, phenomenon," says Withey.

McGowan, who has studied crows in upstate New York since the 1980s, has also observed behavioral changes in both humans and crows. The crow's taste for farmers' crops, which had spurred an adversarial relationship with people, has eased in the past few decades. "We used to not get close to crows because we shot them. Did restrictions on killing crows [mandated by the 1972 inclusion of crows in the federal Migratory Bird Treaty Act] change this interaction? It is hard to say, but [the change] is compelling," he says. Living in closer proximity offers opportunities for wildlife viewing and has given both species a chance to know each other better.

Until recently, however, few researchers and fewer lay people appreciated the brainy birds. Instead people attacked crows, often killing thousands at a single roost. The preferred method was to decorate a known roost tree during the day with hundreds of foot-long steel tubes, each containing a stick of dynamite and several pounds of iron pellets. These would be detonated electrically at night after the birds had returned. State game officials killed 26,000 birds in Oklahoma in one roost in 1937 and another 18,000 the following year. In 1940, Life magazine reported the killing of as many as 328,000 crows in roosts near Rockford, Illinois. The story included pictures of a man and a boy clubbing wounded crows to death and of kids sitting on a sled loaded with dead crows. Making no apology for the killings, the article was headlined "Least Popular U.S. Bird Is the Crow."

But with more research providing convincing evidence of their intelligence, crows are winning newly found respect. The birds not only use tools; they have been known to fashion them. A recent report describes the inventiveness of Betty, a captive crow who took a straight piece of wire and bent it to form a hook, which she then used to pull a bucket of food out of a tube. Walnut-eating crows are as discriminating as any inspector on the line at a Planter Nuts factory. The birds tailor their walnut cracking with amazing accuracy--choosing to drop harder nuts at greater heights and adjusting the release altitude on successive fly-bys to account for varying substrates.