" Carrion crows use passing cars to crush especially tough nuts, such as walnuts, that won’t break by simply falling on pavement. The now-famous video of these crows in a city in Japan shows one stationed above a pedestrian crossing. When the light turns red, it positions its nut on the crossing, then flies back to the perch and waits while the light changes and traffic passes; when the light turns red again, it flutters down to safely collect the cracked nut. If no car smashed the nut, the bird repositions it. "

― Jennifer Ackerman , The Genius of Birds