Aesop's Crows Understand Physics, Literature

Aesop told the fable of a thirsty crow that came upon a nearly empty pitcher of water and discovered that by dropping pebbles in, he could raise the water to a drinkable level. The moral is "Little by little does the trick"--or was that "Necessity is the mother of invention"? Either way, scientists have enjoyed testing non-fictional members of the clever corvid family with this puzzle. Most recently, wild crows showed scientists they're smart enough for a whole barrage of Aesop-inspired challenges.