Ill 



MIGRATION 



The migration of birds is their movement away from their 

 breeding grounds at the close of one breeding season, and 

 their return to it at the approach of the next. Almost all 

 birds move about to a certain extent after they are no longer 

 bound to the neighborhood of the nest, but when an Owl 

 haunts the same swampy forest throughout the year and a 

 Downy Woodpecker wanders no farther from its woodland 

 home than the nearest village, we call such birds non-migra- 

 tory. The great majority of our birds, however, are forced by 

 lack of food to move southward at the end of summer ; some 

 go only a short way, many pass beyond the limits of the 

 United States, a few pass the Equator. It often happens that 

 there are individuals of a species present both in summer 

 and in winter ; there are Chickadees, for instance, in New 

 England at all seasons, though it is quite possible that they 

 are not the same individuals — that the more southern have 

 been replaced by some that bred farther north. For our 

 purpose, however, such birds must be considered permanent 

 residents. Some species, Crows for instance, are permanent 

 residents, but are much dommoner in summer than in winter. 

 The wandering away from the breeding ground begins 

 almost as soon as the young are able to fly ; Snowbirds often 

 appear in the valleys, a mile or so from spruce growth, as 

 early as the middle of July. During August, many of our 

 resident birds undoubtedly move southward ; many have 

 been silent for some time, so that we do not notice their 

 departure. A few species, too, reach us from the north 



