Newton (Encyclopæedia Britannica, article Birds) says: "We have here more than enough to excite our wonder, and instead are brought face to face with perhaps the greatest mystery which the whole animal kingdom presents—a mystery which attracted the attention of the earliest writers, and can in its chief point be no more explained by the modern man of science than by the simple-minded savage or the poet or prophet of antiquity. Some facts are almost universally known, and have been the theme of comment in all ages and in all lands. The hawk that stretches her wings toward the south is as familiar to the latest Nile-boat traveler or dweller on the Bosporus as of old to the author of the book of Job.
"The autumnal thronging by myriads of waterfowl of the rivers of Asia is witnessed by the modern sportsman as it was of old by Homer. . . . But there is no need to multiply instances. The flow and ebb of the mighty feathered wave has been sung by poets and reasoned by philosophers, has given rise to proverbs and entered into popular superstitions, and yet we must say of it still that our ignorance is immense."
While this author does not exaggerate either the interest or our ignorance of the life of birds, which goes on in regions that are almost inaccessible and unknown, there is no reason to suppose their migrations are any more mysterious than most biological problems; for the modern man of science is little more able than the simple-minded savage or the poet or prophet to tell how all the co-ordinated faculties of a predaceous animal are so thrown into action by the stimulus of hunger as to lead to the pursuit and capture of prey; yet there is no mystery in the physiology of hunger, for, while there is much we do not understand, we do know that hunger incites actions which are responsive, or adapted for satisfying hunger.
So also it may be possible to make progress in the study of the meaning of migration in spite of our ignorance of the nature of the impulse which excites and determines it; and while I gratefully acknowledge my debt to Newton for the facts, I am not able to agree with him that there is anything distinctively or peculiarly mysterious in the subject.
While there is reason to believe almost every bird of temperate and arctic climates is migratory to some degree, those which simply range over a wider area at one season than at another present nothing notable, and it is only in regions which are almost or quite deserted by birds for part of the year that their migrations attract the attention of students. As many birds which are most valued for food are found in temperate regions for only a short time in the spring and fall, sportsmen and hunters and all who pursue them for food