Page:Popular Science Monthly Volume 20.djvu/544

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T would be a curious study to ascertain at what time certain wild animals came to be associated with man. We do not mean those which have become domesticated, though many of these run back far beyond the historical epoch. By wild animals we mean those which, still continuing in a wild state, build their nests or construct their burrows near, or within, the habitations of man.

The first advances in this direction must have been made by certain members that differed slightly, in their impulses, from others. It might have been the more courageous and intelligent ones, which, not fearing the presence of man, and recognizing the advantage to be gained in the greater abundance of food, selected human habitations as their abiding-places; or it might have been individuals so stupid as not to be aware of the possible danger of man's proximity, and thus unwittingly selected places in or about his dwellings.

The birds that nest in our trees we generally protect through humane or selfish motives, while with the rats, mice, and certain insects, we keep up a perpetual warfare. Yet, that these latter animals survive, indicates that, in spite of this opposition, the favorable conditions must outweigh the adverse ones, otherwise they would soon be exterminated.

A special investigation in regard to birds would be of great interest. The change that has taken place in the habits of birds in forsaking the forests and fields, and building their nests in the trees of towns and villages, must have occurred since the first settlement of this country by Europeans. After the incoming of each species from the wilderness their increase must have been rapid, as the favorable conditions far outbalanced the unfavorable ones. Not only does the bird secure a certain immunity from danger, in the shape of predatory birds like the hawk, but it finds itself in the midst of a plentiful supply of insect-life, which has in turn been lured from the wilderness, and which has developed with frightful rapidity, owing to the dense crops which man raises, and which were not always to be destroyed by every forest fire or persistent drought. Many species have been forced in by the destruction of large tracts of forest, which compelled them to seek other food, or become extinct. The destruction of forest-trees still goes on in this country with criminal celerity, and new insects injurious to vegetation will be added from year to year.

Audubon somewhere remarks that in passing through a dense forest it was the rarest thing to hear the notes of those song-birds most familiar to him, and he could always recognize his approach to a village by the notes of those birds which most commonly frequent our trees and fields. It is known historically when the cave-swallow first