The Birds and Poets 167 



for the purpose. When the roosting time comes 

 they rapidly approach the top of the chimney, and 

 the whole company darts back and forth over it, 

 time and again, showing every indication of drop- 

 ping into it but still continuing their flight. After 

 a number of preliminary approaches of this char- 

 acter, a small number drop into the chimney top 

 and disappear, while the rest continue their rapid, 

 reeling flight, and circling and sailing about over 

 the chimney again, another select few drop into 

 it, and thus they continue until at last all have dis- 

 appeared in the sooty depths of the chimney. 



The swifts also leave about the middle of Sep- 

 tember, and the remarkable thing about it is that 

 no one knows where they go. Their winter base is 

 one of the unsolved mysteries of bird migration. 



The late Mr. Wells W. Cooke, of the United 

 States Biological Survey, perhaps the foremost 

 American student of migration, could tell us no 

 more about this riddle than the merest novice. 



He says : 



"Much has been learned about bird migration in 

 these latter days, but much yet remains to be learned, 

 and the following is one of the most curious and inter- 

 esting of the unsolved problems. The chimney swift 

 is one of the most abundant and best-known birds of 

 eastern United States. With troops of fledglings catch- 

 ing their winged prey as they go and lodging by night 

 in tall chimneys, the flocks drift slowly south, joining 

 with other bands, until on the northern coast of the 

 Gulf of Mexico they become an innumerable host. 



