When birds land with both their feet on the electric wires, their body has enough electric ‘resistance’ to protect them. This means that for the electricity it doesn’t make sense to make an effort and go through the birds’ body, so it continues travelling along the wire. However if the bird touches the pole at the same time as the wire, the electricity sees a shortcut to get back to the ground (electricity likes to go back into the ground) and so it goes trough the bird’s body, electrocuting it.
Comments