Sheila Malysa, age 13, of St. Catherines, Ontario, Canada, for her question:

How do migrating birds navigate?

This wondrous mystery has tantalized everybody for ages. In recent years, researchers began trying to solve it by using scientific methods. They have gathered masses of data, found a few clues    and grasped the tail end of the mystery. But the complete explanation must wait until large numbers of persons prepare themselves for careers in ornithology. Goodness knows how many persons will take up the study of birds before this problem is solved.

One clue suggests that the birds sense that the days grow longer and shorter through the year. Certainly they time their migrations to the lengthening days of spring and the shortening days of autumn. Some researchers suspect they may navigate to some extent by the sun and the stars. But nobody really can explain how they find their way over trackless oceans, or retrace the same long journeys year after year.