Final answer:
A bird sitting on a high-voltage power line is not electrocuted because it does not provide a path to the ground. However, if a bird hits two wires with its wings, it can create a circuit and be electrocuted.
Step-by-step explanation:
A bird sitting on a high-voltage power line is not electrocuted because electricity always takes the path of least resistance, and the bird does not provide a path to the ground. The bird's body is not grounded, so there is no potential difference between the bird and the power line to cause a flow of current.
However, if a large bird hits two wires simultaneously with its wings, it creates a complete circuit, allowing the current to flow through its body. This can result in electrocution because the bird completes the circuit and becomes a pathway for electricity to flow to the ground.