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We used to be pretty smug about our species’ ability to use tools—the dividing line, some thought, that separated humanity from the rest of the animal kingdom. But naturalists’ observations have laid that notion to rest. 

We now know about tool use by chimpanzees and orangutans, and the sea otters that crack abalone shells with rocks, and, unlikely as it might seem, a variety of birds. 

Egyptian vultures and Australian black-breasted kites use stones to crack the eggs of, respectively, ostriches and emus. The woodpecker finch of the Galapagos Islands employs a small pointed stick to extract insects from crevices. In the southeastern United States, brown-headed nuthatches use fragments of pine bark as wedges to remove more bark, under which insects are hiding. 

So, forget tool use. But surely tool making—intentionally shaping an object for some purpose—is exclusive to us and our great-ape kin? 

Sorry. 

On the South Pacific island of New Caledonia, a species of crow—a perfectly ordinary-looking black bird—has developed the ability to craft insect-probes from the leaves of pandanus trees. 

Gavin Hunt, who has spent years studying these remarkable crows, says the tools are made to a pre-set pattern, and that different populations seem to have distinctive tool traditions. Hunt isn’t prepared to say whether the crows’ tool-making behavior is learned or innate. Either way, it’s hard not to be impressed. 

It figures that if any bird had the cognitive wherewithal to make its own tools, it would be some kind of crow. Crows, ravens, and their relatives are famous for their adaptability, resourcefulness, sociality, and curiosity. As a group, they have the highest encephalization quotient—ratio of brain size to body size—among birds. (The relationship of this measurement to intelligence of some kind is indicated by the its range in mammals, from Homo sapiens and a couple of dolphin species at the high end to the opossum at the very bottom.) 

But is the New Caledonian crow uniquely gifted? According to Carolee Caffrey, a zoologist at Oklahoma State University, maybe not. Caffrey, whose primary concern now is the impact of West Nile disease on crow populations, is a keen observer of the American crow’s behavior. A few years ago she watched a crow investigating a hole in a fencepost. Unable to get its bill very far into the hole, the crow pried off a triangular piece of wood from the post. It held the wood fragment down with its feet and hammered at the tapered end with its beak, then picked the object up by the wide end and poked around in the hole with the pointed end. Caffrey says the crow was distracted by a flockmate and flew away before retrieving anything, leaving the tool behind. Comparing the fragment with the wood from which it had been removed, she saw that the tapered end had been narrowed. Later she found a sizable spider in the hole. 

Okay, it’s not a graduated socket-wrench set. But the crow’s improvised spider-pick is a remarkable enough achievement. (I keep wanting to use the word “manufacture,” which is not really appropriate for a creature that works with its beak). 

Caffrey also says she has seen American crows engaging in another behavior that could be called tool use by proxy. And it’s one that I suspect I’ve also seen among the crows that begin to gather in Hitchcockian numbers in my neighborhood around this time of year. I once saw one swoop down from its utility wire perch after a car had passed, pick up what appeared to be a cracked walnut from the street, and fly off with it. Caffrey has watched crows in Encino “land on wires above a road, drop pecans onto the pavement, and not fly down to inspect or retrieve them until a car had passed.” The inference is that the crows know what will happen to a nut when a car runs over it, and take advantage of traffic to get at the tasty contents.  

This is a topic of some controversy among students of corvids. It appears to have been first reported in 1974, by Terry Maple of the UC Davis psychology department (with walnuts as the food item), and in 1978 by two biologists apparently visiting Long Beach (palm fruit). Some years later, a team of researchers at Davis, headed by Daniel Cristol and Paul Switzer, set out to systematically study whether the local crows were using cars as nutcrackers. They logged over 25 hours of observer time in a neighborhood with walnut trees and a crow roost that housed up to 10,000 birds. Cristol and Switzer concluded that the crows were no more likely to bring walnuts to the study site or to drop nuts on the road when a car was approaching than when the road was empty. (They also noted that none of the walnuts dropped by crows were hit by any of some 200 passing cars). 

What was really going on, Cristol and Switzer decided, was that the crows were trying to crack the nuts by dropping them on the roadbed, and that the presence of the cars was just coincidental. That doesn’t require all that much cognitive flexibility. Even a seagull knows what will happen if you drop a clam onto pavement. (The Greek tragedian Aeschylus is said to have been killed when a passing vulture, mistaking his bald head for a rock, dropped a tortoise on it.) 

But I suspect Caffrey may be right. These birds are not just smart. Read, say, Bernd Heinrich on ravens, and you begin to believe they may have a twisted sense of humor. It would be just like a crow to decide to thwart the researchers: “Okay, now, just lay off the walnuts until those guys with the binoculars are gone.”