Would you ever touch a live electric wire? Certainly not, because it is likely to kill you. So how come birds can sit unruffled on high-voltage power lines? What magical skill do they have to withstand such contact? To understand that, we have to first understand electrical current.
Electrical Current
The electrical current is the motion of electrons. These electrons travelling from the power station to your house through the mains. They then move throughout the power lines through your electronic devices and eventually return to the principals. This process takes place in a closed loop. This closed-loop is necessary for electricity to flow, to move. Electrons also require a difference in electric potential.
Simply put, electrons move from a higher electric potential to a lower one. Imagine a lot of balls on top of the hill. If they're not blocked, they will roll down any path that becomes available. That imagine similar to how electrons move from one electrical potential to another.
What happens when birds sit on power lines?
When a bird sits on a wire, both of its feet are at the same electrical potential, so the electrons, therefore, have no reason to flow through the bird's body. No moving electrons means no electric current. The bird is safe unless it suddenly touches another electrical wire, especially one with a different electrical potential. If it does this, it opens a path for the electrons to flow away for electrons to move through the bird's body.
It is also dangerous for birds to sit on the wooden poles supporting the wires. This pole is buried in the ground. Therefore it has a low electric potential. When a bird was to sit on that pole and simultaneously touch a cable, the current would once more flow from the high potential wire through the bird's body and into the low potential ground.
Above is the same reason why it is dangerous for humans to touch live wires. Since we're almost always in contact with the ground, our bodies serve as a conductor for current to move from an area of high potential like a wire to an area of lower potential, the floor. Our bodies make excellent electrical conductors, and the result is that we get zapped.
Repairing live wires in the power lines
Why workers repairing live electrical wires use insulating materials, such as rubber in their clothing and equipment. Even their bucket trucks are properly Insulated. These insulating materials do not conduct electricity, so the electrons are blocked from flowing.
Workers who repair power lines also sometimes work while hanging from a helicopter, ensuring they are not touching the ground. They still need to make sure they only contact one wire at a time, though. That is why the job of electrical repair remains one of the most dangerous around, which leads to our conclusion. It may be safe for birds to sit on electrical wires, but humans should stay far away.
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