Question

Why Don't Birds get Electrocuted when they land on wires?

Answer 1

because their legs are very close so high amount of potential difference is not generated

Answer 2

Not only birds, even humans won't be electrocuted if they land on wires. See to be electrocuted the path trough which the current flows should be complete without any breaks. Now when a bird lands on a wire, a circuit is not established so current does not flow through its body. However if the bird is stationed on the ground, and the wire falls on it, then a complete circuit is established as the bird is earthed. Hope i solved your query.