Karen Siegel, age 10, of Carmel, Ind., for her question:

WHY DO BIRDS SING?

You might think that birds sing sweetly as a way of attracting a mate or perhaps just for the joy of making happy music. While this might be the case part of the time, scientists tell us that more probably the bird sings because he is warning strange birds to stay away.

Each kind of singing bird has its own special voice. Most melodious of all songbirds, the experts say, is the wood thrush.  Sparrows may sing as many as 20 variations of the same song. Birds often make sounds other than singing. Sometimes they make noise to warn other birds that an enemy is near.