When working on high voltage power-lines via helicopter the technician will "bond-on" with a steel wand called a hot-stick. During this process an arc is conducted from the line to the wand. Now, since the helicopter is floating both literally and electrically, why is there any potential between the line and the wand?
My guess is that because of the alternating electric current in the power-line there is therefore an alternating expanding and collapsing magnetic field present in close proximity to the helicopter. This sets up a charge polarization in the frame of the helicopter 180 degrees out of phase with the current and therefore an electrical attraction occurs which produces an electric potential.
If this is true, even though the electrons are not free to move in a bird (as they are in the metal helicopter frame) they are able to rotate and still set up a charge polarization (much like a charged balloon sticks to a wall) and therefore when a bird "bonds-on" to a wire don't you think they feel a little tingle at first?
One other thing. Is it true that by virtue of the fact the the helicopter circuitry is an isolated one, they can bond-on to either line and that line will be the ground reference for the ground of the helicopter circuitry?