Why birds will not get shock when they are on high tension wire?

They're a lot of reasons that I don't know of but here are some, Birds do get electrically shocked sometimes, but most of that time they're not touching the ground or another object that electricity can pass on to. If the bird is touching a branch of a tree then that's a complete circuit, the electricity can go through the bird to get to the tree. That causes electrical shock, want more information about it?