Birds are known to perch on 2300V bare transmission line without apparent harm. why?

Question

please explain the reason behind this.

Answer 1

For the same reason that a bulb will not light if only one side of a battery is connected to it.  

Both sides of the battery must be connected, one to each side of the bulb, for anything interesting to happen.

A bird sitting on an electrical cable is sitting on one side of the supply.  

n.b. the word "ground" helps no one.  It is usually used without understanding what it really means anyway.

Answer 2

no path to ground.