How do birds sit on high-voltage power lines without getting electrocuted?

When a bird is perched on a single wire, its two feet are at the same electrical potential, so the electrons in the wires have no motivation to travel through the bird’s body. No moving electrons means no electric current. Our bird is safe, for the moment anyway… If that bird stretches out a wing or a leg and touches a second wire, especially one with a different electrical potential, it will open a path for the electrons — right through the bird’s body.