A bird is in a cage outside a window. She often sings at night when all other birds are asleep. One night a bat comes. He asks the bird, "Why do you only sing at night?" The bird says, "Last year when I was singing in the daytime, a bird catcher heard my voice and caught me with his net. Since then I never sing in the daytime." The bat says: "But it is no use doing so. You are in the cage now."