2 28 THE MIGRATION OF BIRDS. 



by having to complete their moult, but then they 

 too, in a great many cases, pack together and migrate 

 in company. Unfortunately we have not much 

 reliable data respecting the autumn movements of 

 birds in the Arctic regions just previous to migra- 

 tion, but in more temperate latitudes the information 

 is ample. In the Arctic regions the great wave of 

 Autumn Migration is not so apparent in its de- 

 parture as in its arrival, but further south towards 

 the grand winter quarters, when the flood-tide of 

 this mighty host is gradually accumulating, it is 

 even more apparent than in spring, the points of 

 greatest influx being of course exactly reversed. 

 The first signs of autumn appear in the Arctic 

 regions during August, when the sun drops behind 

 the horizon for a little time every twenty-four hours, 

 his stay gradually getting longer and longer as 

 September arrives. Then the frosts begin, and by 

 the end of that month summer is banished for the 

 year, and the great army of migrants that had 

 collected here from almost every corner of the 

 world, has fled south again, and the land is given 

 up to silence and desolation once more. Species 

 after species for two months has been speeding 

 south ; all the old winter quarters in temperate and 

 tropic latitudes have been slowly filling with 

 banished birds, fleeing from the terrors and the 

 hardships of a northern winter ; and with the 

 gradual spending of this mighty wave of Avian 

 Refugees the grand phenomenon of Bird Migration 

 completes once more its annual cycle. 



