Page:Popular Science Monthly Volume 60.djvu/331

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THE sudden appearance of certain familiar birds in spring and their disappearance at the close of summer has excited the attention and interest of all classes of observers from the earliest times. "The stork in the heaven" says the prophet Jeremiah, "knoweth her appointed time; and the turtle and the crane, and the swallow observe the time of their coming." Much curious speculation has been indulged in to account for this periodic appearance and disappearance, one ingenious writer of the early part of the eighteenth century arguing that when the birds leave in the fall they retire to the moon. He presumed that they required about two months in passing thither, and that, after arriving above the lower regions of the air they will have no occasion for food. Concerning the great distance, he adds, 'between the moon and the earth, if any shall still remain unsatisfied, I leave only this to his consideration, whether there may not be some concrete bodies at much less distance than the moon, which may be the recesses of these creatures, and serve for little else but their entertainment,' just as the rocky islands of the sea which he says are 'of no other manifest use than for sea fowl to rest and breed upon!'

Hardly less absurd but wonderfully more persistent has been the notion that birds hibernate during the winter in hollow trees, caves and holes, and, at least in the case of swallows, in the mud at the bottoms of lakes and ponds. Linnæus and Cuvier, as well as a great number of lesser lights, believed that swallows spent the winter in a torpid state in mud, and even as late as 1878, a writer in a prominent natural history journal in this country described the finding, in midwinter, of two swallows in the mud at the bottom of a spring in a logging camp in Maine. When taken out they are said to have revived and to have flown about in a warm room.

These absurd ideas have gradually given way to more rational views, and at the present time the whereabouts of a great majority of our birds is known accurately for the entire year. Their coming and going on these long journeys has been under intelligent, though often desultory, observation for more than a century and, although we have learned much, it seems likely that we are hardly advanced beyond the borderland of this intricate and fascinating subject. The object of the present paper is to bring together some of the more important