At dusk, thousands of crows lift off from their roosts just outside Burnaby and head into the city, joining dense flocks from other staging areas. At an intersection in central Burnaby, vortexes of black birds whirl down out of the overcast sky, settling on rooftops, lampposts, boulevards and stop signs. To an onlooker, it seems as if the sky has cracked open and every crow on the planet is pouring onto this utterly unremarkable expanse of suburbia. Like a scene from Hitchcock’s The Birds, thousands of crows gather in fidgety masses on bare trees and crowd shoulder-to-shoulder on hydro lines. It’s not raining, but women heading home after work nevertheless grimace and hold umbrellas over their heads as they pass under the jostling crows.
There may be no obvious reason why the crows come here, but Clulow says they’re clever birds, and they do everything for a reason. “They exploit every chance of survival, and they’re quick to adapt. Their choice of this spot may have something to do with the growth of Burnaby. It’s a bit warmer than the surrounding countryside, so this roost may allow them to conserve energy on a cold winter night. There’s safety in numbers, too, and any hawk, owl or raccoon that showed up here would be quickly mobbed and driven off.”
Other birds (such as robins and sparrows) do well in suburbia, but they don’t form enormous and complicated societies that share information and defend against threats. Why are crows so well organized? Crow behaviour might have something to do with their intelligence. Without implying disrespect toward the typical male robin, which might spend hours hurling itself against its own reflection in a kitchen window, scientists are learning that crows are smarter than the average bird.
It’s difficult to measure intelligence, even in humans, but crows get high marks among scientists for their impressive problem-solving. In one test, a crow jammed a wire rod into a crevice, then gripped the other end for maximum mechanical advantage and walked in a semicircle, bending the tip of the rod into a small hook, which it then used to extract a treat from the bottom of a tube. British researchers tested a crow that could solve a sequence of complex problems — in the right order — to get a reward.
Crows can also understand symbols and analogies, and unlike a robin, they can look in a mirror and seem to understand that it’s a reflection. They also seem to know they are distinct from others. Scientists call this “theory of mind.” When crows are stashing treats, they make sure other crows aren’t watching. They comprehend that other crows may have separate and sometimes conflicting needs. (In human children, this is a major step in psychological development.) When appraising human onlookers, crows use a beady, calculating stare that some people find creepy.
Marzluff has conducted experiments on corvids that determined crows have large brains compared to their body size. Brain-to-body mass ratio is a good indicator of intelligence, and corvids (crows, as well as ravens and jays) have larger brains than any other bird relative to their body size except parrots. And the crow forebrain is organized in clusters rather than layers. This is important because birds belong to a distinct evolutionary line that branched off 300 million years ago. Bird brains and mammalian brains have very different wiring plans and hardware, but their CPUs perform similar tasks. This calls into question the old model of the “tree of evolution,” with human beings at the crown. The “tree” may be more of a shrub, with smart animals developing along any number of off-shooting branches.
For a crow or a human, a large brain has proven to be an asset. Of course, some humans are more intelligent than others. Ditto with crows — in a laboratory, some crows ace tests while others fumble. It’s reasonable to assume that clever crows will do better in a demanding and rapidly changing urban environment. Is it therefore possible that crows are getting smarter?
It sounds like the premise for a spooky movie. But walking through the Burnaby roost, looking up at all those glinting black eyes, it’s impossible not to be captivated by the idea. Crows talk to each other. They build tools and solve problems. They even take transit — in Vancouver, one crow has been filmed riding the SkyTrain. The solitary crow gets on the train downtown, minds its own business and gets off in East Vancouver. (It beats flying.)
Marzluff says the idea of rapidly evolving super-crows may not be far-fetched. “They are definitely changing their behaviour,” he says. “For example, in Japan, when cars stop at a red light, crows will swoop down and place a hard walnut in the path of the tires. Natural selection favours individuals that make good choices, and crows have done so by learning to take advantage of our expanding cities. Crows are evolving culturally — and that is the very definition of evolution.”