BIRD TRAVELERS 5 



their way to and from their breeding-grounds. Many 

 warblers belong to this group. The birds which be- 

 long in each of these four groups vary according to 

 the locality. 



The general changes in bird life due to migration 

 which occur annually in any locality may be briefly 

 summarized as follows: During the winter months 

 the birds found in a locality belong to the perma- 

 nent residents and winter residents. For several 

 months there is little change in the kinds of birds 

 seen. But beginning with the early spring the migra- 

 tion commences, the exact date varying with the lat- 

 itude and the weather. New birds continue to come 

 in large numbers up to the middle or last of May, 

 some remaining for the summer and others passing 

 farther north. Meanwhile the winter residents have 

 been leaving. Then follows the breeding-season, 

 and for several months there is little change in the 

 kinds of birds seen. About the first of September 

 the fall migration begins, extending into Novem- 

 ber, the birds gradually leaving for the South, 

 slipping away so quietly that they may be gone for 

 some time before their absence is noted. In the 

 late fall the winter residents arrive, and bird life 

 settles down again to the winter quiet. Thus this 

 annual change occurs year after year with great 

 regularity. 



Regularity of migration. The time at which each 

 species of bird arrives at a certain place varies little 



