Statement - I : A bird perches on a bare high power line, and nothing happens to the bird. A man standing on the ground touches the same line and gets a fatal shock.
Statement - II : Current passes only when there is a difference in potential.

When a bird is perched on a bare high power line, the circuit does not get complete between the bird and the earth therefore, nothing happens to the bird. But When a man standing on the ground touches the same line, the circuit between the man and the earth gets completed. As a result, the high current passes through the man and the circuit gets completed and he gets a fatal shock.