Bird BrainsCracking WalnutsThe scene: a traffic light crossing on a university campus in J

Bird Brains

Cracking Walnuts

The scene: a traffic light crossing on a university campus in Japan. Carrion crows and humans line up patiently, waiting for the traffic to halt. When the lights change, the birds hop in front of the cars and place walnuts, which they picked from the adjoining trees, on the road. After the lights turn green again, the birds fly away and vehicles drive over the nuts, cracking them open. Finally, when it's time to cross again, the crows join the pedestrians and pick up their meal.

Biologists already knew the corvine family--it includes crows, ravens, rooks, magpies and jackdaws--to be among the smartest of all birds. But this remarkable piece of behavior. would seem to be a particularly acute demonstration of bird intelligence. Researchers believe they probably noticed cars driving over nuts fallen from a walnut tree overhanging a road. The crows already knew about dropping clams from a height on the seashore to break them open, but found this did not work for walnuts because of their soft green outer shell.

Other birds do this, although not with quite the same precision. In the Dardia Mountains of Greece, eagles can be seen carrying tortoises up to a great height and dropping them on to rocks below.

Do Birds Have Intelligence？

Scientists have argued for decades over whether wild creatures, including birds, show genuine intelligence. Some still consider the human mind to be unique, with animals capable of only the simplest mental processes. But a new generation of scientists believes that creatures, including birds, can solve problems by insight and even learn by example, as human children do. Birds can even talk in a meaningful way.

Good Memory

Some birds show quite astonishing powers of recall. A type of North American crow may have the animal world's keenest memory. It collects up to 30,000 pine seeds over three weeks in November, and then carefully buries them for safe keeping across over an area of 200 square miles. Over the next eight months, it succeeds in retrieving over 90 percent of them, even when they are covered in feet of snow.

Making and Using Tools

On the Pacific island of New Caledonia, the crows demonstrate a tool-making, and tool using capability comparable to Paleolithic man's. Dr Gavin Hunt, a New Zealand biologist, spent three years observing the birds. He found that they used two different forms of hooked "tool" to pull grubs from deep within tree trunks. Other birds and some primates have been seen to use objects to forage. But what is unusual here is that the crows also make their own tools. Using their beaks as scissors and snippers, they fashion hooks from twigs, and make barbed, serrated rakes or combs from stiff leathery leaves. And they don't throw the tools away after one use--they carry them from one foraging place to another.

Scientists are still debating what this behavior. means. Man's use of tools is considered a prime indication of his intelligence, is this a skill acquired by chance？ Did the crows acquire tool making skills by trial and error rather than planning？ Or, in its ability to adapt and exploit an enormous range of resources and habitats, is the crow closer to humans than any other creature？

Dr Hunt said this of his research: "There are many intriguing questions that remain to be answered about crows' tool behavior. Most important would be whether or not they mostly learn or genetically inherit the know-how to make and use tools. Without knowing that it is difficult to say anything about their intelligence, although one could guess that these crows have the capability to be as clever as crows in general."

The woodpecker finch is another consummate toolmaker; It will snap off a twig, trim it to size and use it to pry insects out of bark. In captivity, a cactus finch learnt how to do this by watc

A．kindness of people

B．harmonious living conditions

C．ecological stability

D．bird intelligence