Stephanie Koehler, age 12, of Milwaukee, for her question:

Why do birds fly south?

A bird does not sit down to/hearty meal. But this does not mean he has a small appetite, He is always eating snacks and during a day he may very well consume his own weight in food. Imagine the mountains of food needed by all the summer time birds. This would include truck loads of worms,, countless tons of insects, endless baskets of berries and seeds. In the summer, all this food is plentiful, There is enough for the parent birds and plenty left over to feed several broods of youngsters.

Come fall, the insects disappear. The worms burrow deep below frost level. There are not enough seeds and berries to go around. Besides which, many trees lose their foliage and the cold winds whistle through their bare branches. These winter trees can provide no shelter for the birds. But the main reason why the birds fly south is to find food.