The reason that birds don’t get electrocuted whilst they sit on power cables is that both the birds feet are at the same potential, so the electricity doesn’t flow through them. Secondly, the bird offers greater resistance to the electricity passing through it than the power cable, so the electricity will travel through the power cable. As long as the birds don’t touch anything else, such as the ground or another power cable, they will continue to sit up there and can take their food.