In a busy city there lived a crow that loved walnuts, but the shells were far too hard for its beak. For a long time it was hungry and frustrated. Then, one afternoon, it saw a car drive over a walnut that had fallen on the road. Crack! The shell broke open, and the crow understood.
After that, the crow had a plan. It carried a walnut to the zebra crossing, dropped it on the road and flew up to the traffic light to wait. The cars rolled over the nut and cracked it. Then the light turned red, the cars stopped, and the pedestrians began to cross. That was the moment when the crow hopped down and collected its lunch.
An old man called Mr. Sato, who fed sparrows on a bench nearby, watched the crow every day. After a few weeks he began to bring walnuts for it. Years later the crow came back to the crossing with its young and taught them exactly the same trick.