A bird is in a cage outside a window. It often sings at night when other birds are sleeping.
One night, a bat flew to the cage. He asked the bird: "Why do you remain silent during the day and sing at night?"
The bird replied: "One day last year, a hunter heard me while I was singing and put me in his cage. Since then, I have never sang during the day."
The bat replied: "But you don't have to do that now, because you have lost your freedom." Then the bat flew away.