14 



the blue-headed vireo, for example, may summer in a lowland 

 grove of tall dense white pines, in the moist interior of which 

 the summer temperature is comparatively low, while in ad- 

 jacent, open, warm, dry, upland pitch pine woods, with an 

 undergrowth of shrub oaks, the prairie warbler may breed. 

 Some species seem to overflow from their normal breeding 

 grounds. The olive-sided flycatcher and the hermit thrush 

 summer on Cape Cod, and the slate-colored junco has been 

 known to breed in eastern Massachusetts. I have recently 

 seen an occupied nest of the myrtle warbler in the lower lands 

 of southern Worcester County near the Connecticut line. 



Changes caused by woodcutting and farming bring about 

 changes in the bird life of a region. The draining of a great 

 swamp may drive out species that previously bred there, and 

 their places may then be taken by others. The draining of a 

 marsh or the cutting of a large tract of timber may have a 

 similar effect. The cutting away of the spruce forest may 

 drive out some Canadian warblers, and at the same time may 

 bring in white-throated sparrows and towhees, which breed in 

 the ''slash" and sprout growth. The foregoing considerations 

 may indicate that while a study of the faunal areas and breed- 

 ing zones is useful to determine where certain species may be 

 nesting, nevertheless breeding birds may be sought and some- 

 times found quite outside of the areas where one would expect 

 to find them. Therefore every locality should be searched 

 during the nesting season. 



July is one of the most interesting months in the bird calen- 

 dar, for then there are many young birds about, and some of 

 the birds which have reared their young begin to slip away 

 toward the south, and shore birds begin to come from the north. 



The Autumnal Migration. 



In August many land birds are inactive, shy, and retiring 

 because of their moult. Many others are then leaving for the 

 south, and many which breed to the northward have not yet 

 reached us, but shore birds and a few ducks are then migrat- 

 ing southward, and some shore birds are visiting the shoal 

 spots of lakes and rivers, where the water is low. These birds 

 may be studied to advantage in August and early September. 



