Birds generally don't get electrocuted on power lines because they don't provide a pathway for electricity to flow through the bird's body. When a bird lands on a power line, it's only touching one wire, which means there's no complete circuit for electricity to pass through. Electricity needs a complete path to flow, and in this scenario, there's no path to the ground, so the bird remains safe.
However, there can still be risks if a bird touches two wires simultaneously or if it somehow creates a path to the ground by touching the power line and another conductive object (like a pole or a tree) simultaneously. In such cases, electricity can flow through the bird's body, resulting in injury or death.
Utility companies take precautions to minimize these risks by insulating power lines and using different designs to prevent animals from creating a path to ground. For example, some power lines are designed with specialized insulating materials or protective coverings to reduce the risk of electrocution for birds and other animals.