MIGRATION 



lumined by the sun for all the duration of their 

 stay. 



Four months pass. The ice is just as cold, the 

 air as bitter, there is no change in the character or 

 abundance of food, yet again comes the restlessness, 

 and northward goes every bird, reflying the eleven 

 thousand miles of whirling globe, and redistribut- 

 ing themselves. If the gods of little birds have been 

 kind to any single pair, the chances are they will 

 meet and mate again, and deposit their eggs in the 

 selfsame hollow. 



These are the facts. But what about Why? One 

 recent answer is that " annual migration cannot be 

 looked upon as an act of volition, but as the auto- 

 matic response to a certain physiological state prob- 

 ably induced by a gonadial hormone." And this, in 

 spite of itself, is very probably true, and contains 

 a core of dramatic interest equal only to the more 

 perspicuous phase of the subject with which we are 

 at present concerned. It is clear that our Arctic 

 terns must move south from their breeding grounds 

 or be starved and frozen to death. But now that we 

 know that they crave ice and stress of storm and 

 small fish in frigid seas, why should they go farther 

 south than Labrador? It would seem that this ob- 

 session of migration sometimes acquires such an 

 impetus that only the whole long length of the 

 planet itself can dissipate it. 



If we find mystery in the migration of the Arctic 

 tern we are still less able to explain the annual 

 movements of many other birds. Of those which are 



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