Causes of the Migrations
“It is more than two thousand years since the wonders of bird travel have been noted; and while the distances and routes of travel are better known, we cannot yet give a positive answer to the question, ‘Why do birds migrate?’ ”
“Please, Gray Lady,” said Sarah Barnes, “I thought you said it was because in fall the insect food begins to freeze and give out, and they go south after it and in spring they want to go back home.”
“Yes, Sarah, that is one of the reasons, and yet birds start off oftentimes when food is still plenty, and every naturalist knows of the rush of the water-fowl northward so early every spring that they are often turned back by storms and have to retrace their flight, and they have all seen that Robins, Bluebirds, and Swallows, following too closely in the wake of the water-fowl, sometimes lose hundreds out of their flocks by cold and starvation.
“If the fall journey is caused by lack of food, why does it begin when food is most plenty? At some of the Florida lighthouses the Wise Men have seen that the southward trip with some birds begins between the first and middle of July, at the time when the crop of insects and ripe seeds and berries is at its height. So the best answer that can be made is that ages ago, when the migrations began, they were connected with a food supply that changed more suddenly than at the present time, and that, even when the direct motive is lost, the habit remains fixed.”
“That’s it; that’s a bully reason!” cried Tommy Todd, excitedly. “They’ve got the notion that they’re going travelling just so often and they can’t calculate the time right and so they get ready too soon; likely they haven’t got very good heads for planning. That’s the reason, Pop says, that every fall, when Ma and Aunt Hannah go up to Kent to visit Grandma Tuck, they are all ready on the stoop by half-past seven, when there’s never been a train from here to there before ’leven. If they were birds, they’d probably fly off as soon as it was light, and get to Grandma’s for breakfast, when they’d written on a picture postal, with tea-cups and a cat on it, that she might expect them for supper.”
When the laugh at Tommy’s comparison had subsided, Gray Lady said, “Your idea is by no means a foolish one, and it may be that a boy like you, who watches and thinks, will some day piece the facts together that will finally settle the question.”