“Another stranger idea was that small birds crossed large bodies of water as passengers on the backs of large birds, such as Cranes, Ducks, and Geese, for people did not know enough of the structure of birds to realize that the machinery of the tiny Humming-bird is as fit for flying long distances as that of the biggest birds that grow. Ideas like this have been believed until a comparatively short time ago, and it is only within the last fifty years that there has been much real progress toward the truth of it all. And this is the way it has been brought about. In our country the band of Wise Men at Washington, forming the United States Biological Survey, have for twenty years been gathering facts about the migration of birds. This body has sent out naturalists to travel through the North American continent from Guatemala to the Arctic Circle, to meet with other scientific men on their way, and keep careful notes of what they see, so that reports are had in the spring and fall each year from hundreds of observers.
“These reports give the date upon which each particular kind (or species, as they call it) of bird is seen, when it becomes plenty, and when it moves on again. The lighthouse keepers also give much information by noting the times at which they find the birds that are dashed to death against the lanterns in the tower. In short, the Wise Men have more material at hand than ever before from which to shape the story that day by day increases in wonder.
“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.