THE BIRDS' TIME-TABLE 



in one flight, but because of these rests between 

 flights the species to which it belongs does not 

 make anything like this rate of speed. 



Professor Cooke's studies for the Biological 

 Survey at Washington have told us more about 

 the speed at which the bird army advances than 

 we knew before. Thus he has found that for 

 the first month of their northward journey, 

 Robins make an average advance of only thir- 

 teen miles a day. The next ten days they go 

 forward at double this pace. Then, as the sea- 

 son becomes rapidly warmer, the rate rises to 

 fifty, and soon to seventy miles a day. This 

 increase in speed does not mean that the Robin 

 flies faster but that its rests are shorter. 



The same authority tells us that when travel- 

 ing from the Gulf of Mexico to Minnesota, 

 Blackpoll Warblers average only thirty to thirty- 

 five miles a day, but before they reach Alaska 

 they have raised this rate to two hundred miles 

 a day. So while the journey of one thousand 

 miles from the Gulf of Mexico to Minnesota 

 takes thirty days, the two thousand five hundred 

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