this was written in the study material:-

"Potential difference is a must for current to flow. Birds do not get electrocuted while sitting on live transmission wires because their body does not provide a bridge or link for the electrons to flow. The potential of a birds body is zero, before coming in touch with the wire. When a bird sits on the wire, the body potential rises and becomes equal to the potential of the wire. If a person standing on ground touches the bird, then both will receive a shock. This is because a persons body provides a link for the electrons to pass to the Earth."

CAN ANYONE TELL ME HOW THE BIRD'S POTENTIAL BECOME ZERO?