The Birds' Calendar 



of them is confined to their s])ring 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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