As a kid I loved watching hooded crows breaking snails' shells by picking up a snail, flying a 10 or so feet up into the air and then throwing the snail against a narrow stone path in the park. I've never seen even one crow making a mistake to throw a snail on the soft grass on either side of the path, they would aways carefully aim for the snail to hit the hard surface - which means it wasn't just an act of imitation, each of them perfectly understood the idea behind what they were doing.