The Birds' Calendar 



of them is confined to their spring passage. It 

 is a peculiar fact, for which I can find no ex- 

 planation, that some species seem to choose a 

 different route for the fall migration from that 

 in the spring passing to the north through the 

 Atlantic States, and even near the coast in 

 spring, but taking a more inland course on their 

 return. The added fact that the fall migration 

 is made in smaller flocks, and apparently with 

 fewer delays on the route, accounts for their es- 

 caping observation even when their course is the 

 same. Strictly speaking, all birds not permanent 

 in one place throughout the year are migrants ; 

 but, for convenience in distinguishing this group 

 from the other two, the term is commonly ap- 

 plied only to those that neither summer nor 

 winter with us, and can be seen only in transit. 

 The approach of warm weather the new 

 impulse of life starts them in successive flocks 

 northward. Moving by easy stages, so that 

 their advance accords with the later opening 

 of spring in more northerly latitudes, they 

 stop for a brief season here and there, and 

 it is often several weeks before they reach 

 their final destination. Evidently no one 

 species moves in a body, as they seem to come 

 in successive "waves." In making a tour of 



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