No bird-brain … clever rook has much to crow about

Published on Monday 25 May 2009 22:11

ROOKS have astonished scientists by proving they can use stones and sticks as tools and can even fashion hooks out of wire to retrieve food.

Researchers studying the large black birds believe they rival even chimpanzees in their ability to use tools.

The rooks, members of the crow family, amazed the researchers by using their beaks to use stones, sticks and wire to get to food.

The scientists even caught them on video bending a piece of wire into a hook to grab a morsel of food that was out of reach inside a tube.

In another experiment, a rook picked up a stone with its beak and put it in a hole to release a trapdoor to get to food. When the diameter of the tube was reduced, the bird chose a smaller stone.

The birds, which were studied in captivity, were able to modify sticks to fetch food and also demonstrated ability to use tools sequentially, by using one tool to retrieve another that was out of reach.

Rooks have never been known to use tools in the wild, but the scientists believe this is because food is so readily available they do not need to put their brains to use in this way.

In contrast, New Caledonian crows, which live on an island in the Pacific, regularly use tools in the wild to retrieve grubs from holes in trees.

Chris Bird, the lead author of the research at the University of Cambridge, said: "This finding is remarkable because rooks do not appear to use tools in the wild, yet they rival habitual tools users, such as chimpanzees and New Caledonian crows, when tested in captivity."

Despite not using tools in the wild, rooks have been known to show other signs of intelligence, such as working in pairs to free food from a dustbin.

Mr Bird added: "Tool use in the wild is generally a consequence of motivation. Rooks don't need to use tools in the wild because they have access to fast food, such as carrion and roadkill and human litter.

"New Caledonian crows don't have the same access to these kind of foods and have to rely on grubs from the trees, so they have the motivation to use tools."

Mr Bird added that crows have particularly large brains, compared with other birds. Only parrots have a similar brain to body size ratio.

As the four birds involved in the study were bred in captivity, the scientists are convinced they used their brains to fathom how to use tools, instead of learning the skills through trial and error.

Dr Nathan Emery, of Queen Mary University of London, who was also involved in the research, said: "We suggest that this is the first unambiguous evidence of animal insight, because the rooks made a hook tool on their first trial and we know that they had no previous experience of making hook tools from wire because the birds were all hand-raised."

Crows feature heavily in folklore. Traditionally, they are said to be able to forecast weather, sense the approach of death and even escort the souls of the dead to heaven.

The results of the study are published in the journal Proceedings of the National Academy of Sciences.