A singing bird was confined in a cage hanging outside a window. It had a habit of singing at night while all other birds slept. One night, a bat came and clung to the bars of the cage, asking the bird why it was silent by day and sang only at night.
"I have a very good reason," said the bird. "Once, when I was singing in the daytime, a fowler was attracted by my voice. He set his nets and caught me. Since then, I have never sung except at night."
But the bat replied, "It is no use doing that now that you are a prisoner. If only you had done so before you were caught, you might still be free."
Precautions are useless after the event.