National Geographic : 2008 Mar
course they're smart. Now we're finding these kinds of exceptional behaviors in some species of birds. But we don't have a recently shared an cestry with birds. Their evolutionary history is very different; our last common ancestor with all birds was a reptile that lived over 300 million years ago. "This is not trivial," Kacelnik continued. "It means that evolution can invent similar forms of advanced intelligence more than once-that it's not something reserved only for primates or mammals." Kacelnik and his colleagues are studying one of these smart species, the New Caledonian crow, which lives in the forests of that Pacific island. New Caledonian crows are among the most skilled of tool-making and tool-using birds, forming probes and hooks from sticks and leaf stems to poke into the crowns of the palm trees, where fat grubs hide. Since these birds, like chimpanzees, make and use tools, research ers can look for similarities in the evolutionary processes that shaped their brains. Something about the environments of both species favored the evolution of tool-making neural powers. But is their use of tools rigid and limited, or can they be inventive? Do they have what re searchers call mental flexibility? Chimpanzees certainly do. In the wild, a chimpanzee may use four sticks of different sizes to extract the honey from a bee's nest. And in captivity, they can fig ure out how to position several boxes so they can retrieve a banana hanging from a rope. Answering that question for New Caledo nian crows-extremely shy birds-wasn't easy. Even after years of observing them in the wild, researchers couldn't determine if the birds' abil ity was innate, or if they learned to make and use their tools by watching one another. If it was a genetically inherited skill, could they, like the chimps, use their talent in different, creative ways? To find out, Kacelnik and his students brought 23 crows of varying ages (all but one 52 NATIONAL GEOGRAPHIC * MARCH 2008 caught in the wild) to the aviary in his Oxford lab and let them mate. Four hatchlings were raised in captivity, and all were carefully kept away from the adults, so they had no opportu nity to be taught about tools. Yet soon after they fledged, all picked up sticks to probe busily into cracks and shaped different materials into tools. "So we know that at least the bases of tool use are inherited," Kacelnik said. "And now the question is, what else can they do with tools?" Plenty. In his office, Kacelnik played a video of a test he'd done with one of the wild-caught crows, Betty, who had died recently from an infection. In the film, Betty flies into a room. She's a glossy-black bird with a crow's bright, in quisitive eyes, and she immediately spies the test before her: a glass tube with a tiny basket lodged in its center. The basket holds a bit of meat. The scientists had placed two pieces of wire in the room. One was bent into a hook, the other was straight. They figured Betty would choose the hook to lift the basket by its handle. But experiments don't always go according to plan. Another crow had stolen the hook before Betty could find it. Betty is undeterred. She looks at the meat in the basket, then spots the straight piece of wire. She picks it up with her beak, pushes one end into a crack in the floor, and uses her beak to bend the other end into a hook. Thus armed, she lifts the basket out of the tube. "This was the first time Betty had ever seen a piece of wire like this;, Kacelnik said. "But she knew she could use it to make a hook and ex actly where she needed to bend it to make the size she needed." They gave Betty other tests, each requiring a slightly different solution, such as making a hook out of a flat piece of aluminum rather than a wire. Each time, Betty invented a new tool and solved the problem. "It means she had a men tal representation of what it was she wanted to make. Now that," Kacelnik said, "is a major kind of cognitive sophistication."