114 USEFUL BIRDS. 



tions may be questioned by those who rely solely upon the 

 examination of stomach contents to determine the food of 

 birds ; but for the purpose for which these investigations are 

 made they are, if skilfully conducted, quite as serviceable 

 as stomach examinations. In fact, one must supplement the 

 other. Were one to follow the birds about through the 

 fields and woods, no doubt some interesting facts might be 

 learned in regard to their food ; but it is not in this way 

 that a series of accurate observations can be made. For 

 our purpose, the method pursued was to find an outbreak 

 of hairy caterpillars situated in a locality where many spe- 

 cies of birds would be likely to find it. The watcher first 

 made sure as to the kind of insects to be found upon the 

 trees or plants to be watched ; he then concealed himself 

 near the insects whose destruction he wished to observe, and 

 watched the birds which came there to feed. When this 

 method is followed methodically by trustworthy, painstaking- 

 naturalists, and when results obtained by different observers ^ 

 working independently, agree in the main, there can be no 

 reasonable doubt as to the value of such observations. When 

 the caterpillars are small, certain marked branches are selected 

 to be watched, or certain nests, webs, or tents are studied at 

 close range. By this method, as well as by stomach exam- 

 inations, fifty-one species or subspecies of birds were found 

 to be feeding to a greater or less extent upon hairy cater- 

 pillars. A list of these is given below. It Avill be seen 

 that it comprises most of the common summer birds found 

 in Massachusetts woodlands, and some not commonly found 



there. 



Birds observed feeding on Hairy Cnterjnllars. 



Yellow-billed Cuckoo. 



Black-billed Cuckoo. 



Hairy Woodpecker. 



Downy Woodpecker. 



Yellow-bellied Sapsucker. 



Northern Flicker. 



Kingbird. 



Crested Flycatcher. 



Phcebe. 



Wood Pewee. 



Least Flycatcher. 



Blue Jay. 



Crow. 



Red-winged Blackbird. 



Baltimore Oriole. 



Purple Crackle or Crow Blackbird. 



Bronzed Crackle. 



White-throated Sparrow. 



Chijjping Sparrow. 



Field Sparrow. 



Song Sparrow. 



Towhee. 



