New Caledonian crows are renowned for their toolmaking skills. In the complexity, fluidity and sophistication of their tool use, their ability to manipulate and bird-handle sticks, leaves, wires, strings and any other natural or artificial object they can find into the perfect device for fishing out food, or fishing out second, third or higher-order tools, the crows have no peers in the non-human vivarium, and that includes such textbook dexterous smarties as elephants, macaques and chimpanzees.
Videos of laboratory studies with the crows have gone viral, showing the birds doing things that look practically faked. In one famous example from Oxford University, a female named Betty methodically bends a straight piece of wire against the outside of a plastic cylinder to form the shape of a hook, which she then inserts into the plastic cylinder to extract a handled plug from the bottom as deftly as one might pull a stopper from a drain. Talking-cat videos just dont stand a chance.
So how do the birds get so crafty at crafting? New reports in the journals Animal Behaviour and Learning and Behavior by researchers at the University of Auckland suggest that the formula for crow success may not be terribly different from the nostrums commonly served up to people: let your offspring have an extended childhood in a stable and loving home; lead by example; offer positive reinforcement; be patient and persistent; indulge even a near-adult offspring by occasionally popping a fresh cockroach into its mouth; and realise that at any moment a goshawk might swoop down and put an end to the entire pedagogical programme.
Jennifer C. Holzhaider, the lead author on the two new reports, said that in one year of their three-year field study, the crows they were following gave birth to a total of eight chicks.
We thought, yay, well have eight juveniles we can watch, she said. But the goshawks, the rats, the owls and the torrential rains took their toll, and only one of those eight chicks survived. Its a hard life in the jungle; thats all there is to it, said Holzhaider.
By studying the social structure and behaviour of the crows and the details of their difficult daily lives, the researchers hope to gain new insights into the evolution of intelligence, the interplay between physical and social skillfulness, and the relative importance of each selective force in promoting the need for a big animal brain.
The researchers want to know why it is that, of the 700 or so species of crows, ravens, rooks, jays and magpies that make up the worlds generally clever panoply of corvids, the New Caledonian crow became such an outlier, an avian savant, a YouTube top of the line.
The birds are indefatigable toolmakers out in the field. They find just the right twigs, crack them free of the branch, and then twist the twig ends into needle-sharp hooks. They tear strips from the saw-toothed borders of Pandanus leaves, and then shape the strips into elegant barbed spears.
With their hooks and their spears they extract slugs, insects and other invertebrates from deep crevices in the ground or in trees. The birds are followers of local custom.
Through an arduous transisland survey of patterns left behind in Pandanus leaves by the edge-stripping crows, Gavin Hunt of the University of Auckland determined that toolmaking styles varied from spot to spot, and those styles remained stable over time. In sum, New Caledonian crows have their version of culture.
Being cultured is hard work. In studying the birds social life, Holzhaider and her colleagues confirmed previous observations that New Caledonian crows are not group-living social butterflies, as many crows and ravens are, but instead adhere to a nuclear family arrangement. Males and females pair up and stay together year-round, reaffirming their bond with charming gestures like feeding and grooming each other, sitting close enough to touch, and not even minding when their partner plays with their tools.
Young birds stay with their parents for two years or more — a very extended dependency, by bird standards — and they forage together as a family, chattering all the while. They have this way of talking in a quiet voice, Waak, waak, waak, that sounds really lovely, said Holzhaider.
The juveniles need their extended apprenticeship. Theyre incredibly persistent, wildly ripping and hacking at Pandanus leaves, trying to make it work, said Holzhaider, but for six months or so, juveniles are no way able to make a tool.
The parents step into the breach, offering the trainee food they have secured with their own finely honed tools. By seeing their parents get a slug out of a tree, they learn that theres something down there worth searching for, she said. That keeps them going.
The carrot-on-stick approach: it works every time.