The Migration of Birds 185 



leave; by July twentieth the bobolinks are collecting 

 into small flocks, while a few days later the red- winged 

 blackbirds are gathering in considerable numbers 

 among the tall reeds along the larger water courses. 

 These are the first signs of the fall migration. Dur- 

 ing August, bird life, considered as a whole, is at 

 low ebb. Some species are slowly collecting, others 

 are roving about as families. There is very little 

 singing ; although the indigo bunting and the red-eyed 

 vireo are still tuneful, and occasionally a sparrow is 

 heard by the roadside. 



Early in September there is a marked change; the 

 warblers are passing in considerable numbers, and 

 about the twentieth we are overwhelmed by their 

 thousands. We must now begin to look for our 

 winter residents, such as the junco and the winter 

 wren. The summer residents are fast going, and 

 through October and November and into December 

 the various sparrows remain, but finally they, too, 

 retreat before the increasing cold and snow. 



The manner of migration is a study in itself. 

 Whether we decide that birds find their way by in- 

 stinct or by heredity of habit, we marvel at it none 

 the less. It is wonderful that birds can travel such 

 great distances over mountain, forest, and plain and 

 even for a considerable distance over the sea and 



