Robin Powell, age 11, of Anderson, South Carolina, for her question:
Why don't migrating birds stay south all year?
If you are seriously interested in bird study, you may choose a career in ornithology. You might solve one of the mysteries of migration. This would be interesting and also useful. Migrating birds have a superior gift for plotting their flights and we could learn a lot from their secret.
The bird population of South Carolina is large and varied but many types arrive and depart with the seasons. The red cardinal and the blue bird, the goldfinch and the throaty mockingbird are permanent residents. So are the raucus grackles and blue jays. An assortment of owls and hawks all stay throughout the year. In spring, the scarlet tanager and the Baltimore oriole arrive to spend the summer. With them come the blue bunting and the purple martin, an assortment of thrushes and warblers and the red throated hummingbird.
As the summer visitors arrive, a number of other birds depart. Some kinds of song sparrows and the waxwings have been around all winter. So have the dainty kinglets, the phoebes and the Brewer blackbirds. A few migrating geese, mallards and other wild ducks wintered where there was water. It would be nice to have these birds around all year. But they have other plans. In spring, they migrate north as the summer visitors fly in from farther south.
Summer, of course, is the nesting time. This is the busy season, for birds are splendid parents. Nothing is too much trouble and nothing is too good for their chicks. And the squalling young birds are hungry, always hungry. From dawn until dunk, the parents dash back and forth to the nest with snacks and more snack's. So much food is needed that they have no time to fly far for it. The nest must be near plenty of the right kind of groceries. This grocery problem is the main reason why birds migrate north to bring up their families.
In winter, the bird population increases in the south. All the spring chicks are grown adults. They are crowded and there is barely enough food. Certainly there is not enough to feed throngs of youngsters. So the adults wait out the winter. In spring, many of them fly north and spread out far and wide. Each pair of parents stakes out a territory where gobs of the might food can be grabbed and whisked up to the nest in a hurry. Owls and other residents stay in the south because their kind of food is plentiful throughout
It seems strange that birds sing their best in spring when they are so busy nesting. They are not, it seems, singing lullabies or whistling to welcome the warm weather. Ornithologists say that their caroling concerns groceries. The song of A father bird warns other birds from his territory so that his family has plenty of food. If another bird of his species trespasses, the two of them fight. However, a seed eating bird is quite willing to share his territory with other birds that do not gather the special food he needs for his growing family.