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Rooks show there may be some truth to Aesop's fable 'The Crow and the Pitcher'

August 7, 2009 |  8:22 pm

New research shows not only that rooks, crow-like members of the corvid family of birds, not only have impressive reasoning skills, it also shows that one of Aesop's fables may not be just a story after all.  

In the well-known fable in question, "The Crow and the Pitcher," a thirsty crow is confronted with a problem: A pitcher that contains water, but at too low a level for the bird to reach. The clever crow hatches (no pun intended) a plan and puts it into action, dropping pebbles into the pitcher until the water is raised to a level at which it can drink.

Researcher Christopher Bird of the University of Cambridge (who has previously made headlines with his bird-intelligence experiments -- and yes, that's his real name) and his colleague, Nathan Emery of Queen Mary University of London, found in their recent study that the fable isn't far from reality. 

For the study, they offered wax worms to four rooks, each of whom was raised by hand and five years old. But even if you're a rook, there's no such thing as a free lunch; the birds had to work for their food.  Bird and Emery placed the wax worms in narrow beakers partly filled with water, but at a level too low for the rooks to reach the worms.  Next to the beakers, they placed piles of stones. 

Our colleague Thomas H. Maugh II explains what the rooks did next:

Two immediately figured out how to get the worm, and two got it on the second try. The birds appeared to calculate how high the water had to rise, and put in only enough stones to raise the water to that level, not stopping to try to reach the worm after each stone. They also figured out quickly that larger stones would raise the water more quickly.

The only other animals known to have accomplished a similar feat are orangutans, which have been shown to carry water in their mouths to fill a pitcher so they can reach a floating peanut. But the rooks' feat is more impressive, Bird argued, because their brains are much smaller than those of orangutans.

This study isn't the first to show a high level of intelligence and problem-solving ability in members of the corvid family. Last year, a German research team subjected a group of magpies to the mirror test, which measures self-awareness by determining whether a subject recognizes its own reflected image as itself.  The researchers placed brightly colored stickers under the magpies' beaks, an area of their bodies that they were unable to see without a mirror. Lo and behold, when they saw themselves reflected in a mirror, the magpies tried to remove the stickers.

Another example of corvids' intelligence was demonstrated by a New Caledonian crow named Betty, who learned to fashion her own curved tool from a straight piece of wire in order to obtain food at the bottom of a beaker.

The results of Bird and Emery's study were published Thursday in the journal Current Biology

-- Lindsay Barnett

Video: A rook named Monroe gets her worm after selecting large stones to drop into the beaker.  Credit: cellpress via YouTube

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