Aesop's ancient fable The Crow and the Pitcher tells the story of a thirsty bird who cleverly drops stones into a pitcher of water, raising the liquid's level to quench his thirst. Now, scientists have shown that rooks (Corvus frugilegus), birds from the crow family, can perform a very similar task. The finding suggests that facts may underlie the legend and indicates that corvids, like great apes, have a general understanding of physical rules.
“I had always wanted to see if there was a way to test what the crow did in Aesop's fable,” explains Nathan Emery, a comparative psychologist at Queen Mary, University of London. But he and his graduate student, Christopher Bird of the University of Cambridge, realized they couldn't “ethically deprive a bird of water.” So they devised an experiment that would approximate the challenge facing Aesop's crow. In previous experiments, the two had shown that the rooks, which are not known for using tools in the wild, would nevertheless pick up stones and drop them into a tube in order to make a treat roll out. In the new experiments, Emery and Bird gave each of four rooks (two mated pairs) a clear plastic tube; the tube contained the larvae of a wax moth–the birds' favorite food–floating near the bottom, just beyond the reach of the rooks' beaks.