THE UNCHARTED SKY 141 



middle of the summer or in the very early autumn 

 when weather is at its finest and food is most 

 plentiful. There is no escaping the fact that 

 among several species of birds, the young, born 

 that season, who have never left the vicinity of the 

 nest, not only leave for the distant south on almost 

 the same day as the young of the preceding season, 

 but also that they fly to the same distant point over 

 the same route, without a single adult bird in the 

 company. This cannot be teaching, it must be in- 

 stinct." 



''But how do yo' suppose the bird finds its 

 way?" 



The Biological Survey expert smiled and shook 

 his head. 



''This time," he said, "you've asked a question 

 that nobody can answer. Ornithologists have 

 solved a lot of puzzles, but they have not yet 

 learned how a bird finds its way in the uncharted 

 air. Neither have they found out how a species 

 of birds, in migrating, invariablj^ takes a certain 

 route and never any other. Their paths in the sky 

 are as clean-cut and as arbitrary as though the 

 birds themselves were machines moving over steel 

 rails. The commonest route is from north-west 

 Florida and Alabama straight across the Gulf of 



