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To see if New Caledonian crows could handle some of the basic principles of volume displacement, Sarah Jelbert at the University of Auckland in New Zealand and her colleagues placed scraps of meat just out of a crow's reach, floating in a series of tubes that were part-filled with water.  Objects potentially useful for bringing up the water level, like stones or heavy rubber erasers, were left nearby. 
The crows successfully figured out that heavy and solid objects would help them get a treat faster. They also preferred to drop objects in tubes where they could access a reward more easily, picking out tubes with higher water levels and choosing tubes of water over sand-filled ones. 

Ref: "Eureka" (exclaimed by Archimedes upon discovery that the volume of displaced fluid is equal to the volume of the submerged object)

Ref: "The Crow and the Pitcher" (A fable by Aesop, where a thirsty crow comes upon a pitcher with water at the bottom, beyond the reach of its beak. The bird drops in pebbles one by one until the water rises to the top of the pitcher, allowing it to drink.)

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