[ArtDodger]

When I lived in Tokyo, rocks were being found on the train tracks. Potentially, very damaging. Never caught anyone doing it. Cameras were set up. Crows were doing it so the trains would bust up the rocks into smaller pieces for their craws...

[MrChips]

Quick! Someone call Alfred Hitchcock!

[Bullish]

I watched a crow one time from where I was working. He was carrying a walnut in his mouth and flying up about 60 ft in the air and then dropping it on the road. He repeated this several times until the shell broke open so he could get to the nut inside. Pretty smart for a bird and it showed he had learned something rather ingenuous to open the nut.

[Boogieman]

Also in Japan, they discovered that crows were dropping nuts into traffic, so the cars would break them open for them:

http://www.youtube.com/watch?v=NenEdSuL7QU