Why Don't Birds get Electrocuted...?
To be 'electrocuted' you must be part of a complete circuit. You must touch both a positive wire, and a negative or neutral wire. If the bird was touching the ground, the ground would act as a neutral wire and the current would flow through the bird (i.e. electrocuting it). If the bird was sat on the wire and touched the metal of the pylon or another wire, it would also complete a circuit and get electrocuted. Because the bird is only sat on one wire, it is safe.