II 



BIRD MIGRATION 



In any given locality, so regular is the date of the 

 return of the migratory birds in their flight from nesting 

 site or winter resort that the exact time may be predicted 

 as accurately as an eclipse of the moon or sun. 



Migration is a kind of marathon in which all the 

 birds of a species are entered. This race is run twice 

 each year and is attended by many difficulties, almost 

 insurmountable, that only the healthy and strong can 

 conquer. By day and by night the procession wings its 

 semi-annual flight along unmarked aerial trails, just a 

 few miles, or hours, in the advance southward before 

 the chilly blast of approaching winter, pausing here and 

 there just long enough to rest a tired wing, or gather 

 a few seeds or other provender. Storms and man with 

 his automatic shotgun make great inroads on these 

 travelers. 



During the glacial period, when the central part of 

 the United States was under an ice-cap, the birds exist- 

 ing at that time had, in all probability, as their northern 

 limit of migration, the southern extremity of the glacial 

 area, in about the same latitude as Kansas City, Mis- 

 souri, and Cincinnati, Ohio. This gap between the south- 

 ern and northern migratory points has, by the retreat 

 of the ice sheet, been extended to the Arctic Ocean and 

 to the islands farther north. 



I have often wished I could join the bird frontiers- 

 men as they go to their unsettled territory in the Far 

 North. What could be more enjoyable than to follow a 

 trail not even blazed by human hand! Yet for ages 

 these winged travelers have followed an imaginary thor- 

 oughfare without leaving a footprint or a sign-board, 

 guided only by that something in their make-up which 

 is more accurate than the stars or the mariners' com- 

 pass. Day and night the right of way is cleared from 

 Brazil to Point Barrow. 



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