256 BIRDS IN THEIR RELATIONS TO MAN. 



hope of survival lay in retreating to inaccessible localities. 

 The wholesale destruction of primeval nesting-sites has been 

 a potent factor in the change produced, but, fortunately, many 

 of the most useful birds found substitutes that answered the 

 purpose very well : kingbirds, chipping-sparrows, cedar-birds, 

 and robins have apparently been glad to adopt the imported 

 apple tree for a home tree ; swallows, swifts, and phoebes 

 have left the cliffs and hollow trees they formerly possessed 

 for rafters and chimneys and artificial houses put up for their 

 benefit. Meadow-larks, vesper, savanna, and other "ground" 

 sparrows inhabiting grass-lands have undoubtedly increased 

 -in numbers and widened their habitat since mowing fields 

 have so largely superseded timbered areas. 



Even under normal conditions birds have to encounter 

 grave perils that many of them, particularly of the smaller 

 varieties, are unable to withstand. Of these their annual 

 migration over hundreds and thousands of miles of land and 

 sea probably is most fatal. Their periods of travel are sea- 

 sons of strenuous weather. Gales carry them out to sea and 

 leave them exhausted to perish on the waves. Unwonted 

 cold in the South sometimes destroys them in great numbers. 

 A backward spring in the North, by retarding insect develop- 

 ment, adds hunger to cold. At the end of the long journey, 

 tired and lean, the birds suffer greatly when spring is late. 

 Warblers, orioles, tanagers, and other sylvan species may be 

 seen searching among the stubble for something to eat. Their 

 feebleness is apparent. Sometimes a cold storm follows, and 

 when such is the case many invariably die. It is interesting 

 to note that during such a stress of weather many birds that 

 ordinarily frequent the woods come to the vicinity of houses. 

 A parula warbler has been known to seek refuge in a store 

 doorway, a humming-bird to crawl into a crevice in a garden 

 gate, and redstarts and a Canadian warbler to find shelter in 

 a barnyard. Birds found dead after such a storm are greatly 

 emaciated, showing plainly the effects of starvation. Well fed, 



