Clever rooks repeat ancient fable

One of Aesop's fables may have been based on fact, scientists report.

In the moral tale, written more than 2,000 years ago, a crow uses stones to raise the water level in a pitcher so it can reach the liquid and quench its thirst - demonstrating that necessity is the mother of invention.

Now a study published in Current Biology reveals that rooks, a relative of the crow, do just the same when presented with a similar situation.

In this footage, the rook first assesses the water level, peering at the tube from above and from the side, then drops stones into the water, raising the water level so it can reach a floating worm.

Video courtesy of Current Biology/University of Cambridge/QMUL