When birds perch, they’re not linked to another line or the ground. No circuit, no current through them. Same for us: grab a single live wire, don’t touch the ground or other conductors, and the current might not flow through you — at least in theory.
The completed circuit idea is key. Electricity takes the path of least resistance. Don’t give it a ground path, and it won’t “want” to go through you.
In theory, you could hold a live wire and not get shocked if you’re not in contact with the ground or other conductive surfaces. But touch something else — ground, a tree, another wire — and it’s deadly. That second contact closes the circuit, letting electricity flow, leading to a bad shock or worse.
That’s why linemen use special gear, insulating gloves, and sometimes helicopters. They block any ground contact, working safely around high-voltage wires.