go NATURE'S CALENDAR 



j>- from every grove ; the thrush, oriole, 



^— finch, and cuckoo mingle their strains in 



the richest chorus of the year, and the 

 tree-tops sparkle with the flitting forms 

 and tinkle with the bright singing of 

 countless gayly dressed warblers. We 

 may see anywhere more birds in May 

 than at any other time of the year, be- 

 cause now we make a passing acquaint- 

 ance with many that do not remain with 

 us, but only flit through on their way 

 from tropical winter-quarters to summer 

 residences far to the north. 



The migration of birds has been noticed 

 ever since men began to make note of 

 anything in the world about them, yet 

 many mysterious questions in regard to 

 the influences that produce it remain un- 

 answered. But, though we cannot ex- 

 plain the why, we have learned much a^ 

 to the how of this movement, which is so 

 peculiar to and characteristic of birds as 

 a class. We know that as winter ap- 

 proaches from the poles it drives south- 

 ward before it— or northward, in the 

 southern hemisphere— the birds which 

 inhabit the polar regions in summer. 

 Some who are hardy and able to pick up 

 a living in a cold and snowy region from 

 seeds and dormant insects go only a little 

 way southward, and become the winter 

 visitors to the temperate zones, where 

 others reside comfortably the'whole year 

 round. Many birds, however, are not 

 content even with the open fields and 



