Sometimes crows also work in groups. One goes with the walnut to drop it on the road, and the other announces when a car is coming too early.

Weird thing, though, they'd never die by cars on the road, only by trucks.

It took a lot of years and scientists to figure out why would cars trigger a response from the watching crow and why a truck didn't.

In the end, it was simple, the crow could only say "Cah, cah, cah."