Crow bar

Natural History, April, 2005 by Stephan Reebs

New Caledonian crows (Corvus moneduloides) are famous for poking twigs under bark or into crevices to dislodge grubs. Only one other species of bird, the wood-pecker finch, uses an object for probing--a cactus spine. But are these cases of nature or of nurture? Does such resourcefulness come naturally to the "average joe" crow (or woodpecker finch)? Or did some unsung Einstein among the birds invent a practice subsequently picked up by every other bird that cared to watch and learn? Ben Kenward and his colleagues at the University of Oxford have a persuasive answer.

In separate aviaries littered with twigs and pocked with holes and crevices, the ornithologists hand-raised two New Caledonian crow chicks, each in isolation. The young birds spontaneously began to use the twigs to reach into the holes and crevices, and, at the tender ages of sixty-three and seventy-nine days, respectively, they got hold of their first tasty morsels. (Two other chicks, raised together and tutored in the art of twig probing by the investigators, first retrieved food from crevices on days sixty-eight and seventy-two.) On day ninety-nine, one of the isolated birds even shaped its own tool by tearing up a proffered leaf and probing for food with the remaining rib.

If two random New Caledonian crows can, by themselves, acquire expertise in twig usage--and if having companions and regular tutelage doesn't speed up the learning process--it seems safe to assume that most members of the species are naturals with an organic version of the bar that bears their name. The scientists conclude that the crow's brain is well wired for both tool use and toolmaking. (Nature 433:121, 2005)