Well, that old child's tale may turn out to have been more fact than fiction.
The following was reported in the Independent on Sunday, about an experiment carried out by faculty from Cambridge and the University of London:
Scientists have found that rooks – a member of the crow family – were able to figure out how to raise the water level in a laboratory container by dropping stones inside to retrieve a tasty worm floating on the surface.Four different rooks, called Cook, Fry, Connelly and Monroe, quickly discovered that they could raise the water level in a transparent container by adding stones, just like the mythical crow in the fable, which illustrates the virtue of ingenuity and how necessity is the mother of invention.
P.S. I thought this was a humorous side note - one of the experimenter's names is Jonathan Bird.