The bird in Japan known for dropping walnuts on crosswalks for cars to crack them is the carrion crow.
Carrion crows are highly intelligent members of the crow family and are widespread across Europe and Asia, including Japan. In some Japanese cities, observers have reported crows placing hard-shelled walnuts in vehicle lanes or at crosswalks, then waiting for passing cars to crush the shells. The birds can retrieve the edible nut after traffic stops or the crossing signal changes.
This behavior is a striking example of tool use and problem-solving. Rather than breaking every walnut with their own bills, the crows exploit the predictable force of vehicles. Crosswalks can be especially useful because traffic pauses at regular intervals, giving the birds an opportunity to collect the cracked food more safely.
The bird is sometimes confused with the American crow or common raven. Those are different species, although all belong to the crow family, Corvidae. The carrion crow is generally smaller than a raven and lacks the raven's heavy bill and shaggy throat feathers. Walnut-dropping stories are also often generalized to “crows,” but the well-known Japanese example specifically concerns carrion crows.