26 FOOD OF WARBLERS 



have caused losses of hundreds of millions of dollars to the wheat 

 growers of the United States. 



My former assistant, Mr. F. H. Mosher, one day observed a 

 pair of Northern Yellow-throats feeding upon the aphis that infests 

 the gray birch. One of these birds ate eighty-nine of these tiny 

 insects in a minute. Mr. Mosher watched the pair eating at this 

 rate for forty minutes, and states that they must have eaten over 

 seven thousand plant-lice in that time. 2 His field-notes also give 

 instances where numbers of caterpillars of considerable size were 

 eaten within very brief periods, by Warblers. 



A Chestnut-sided Warbler was seen to capture and eat, in 

 fourteen minutes, twenty-two gipsy caterpillars, that were posi- 

 tively identified, and other insects that could not be seen plainly 

 were taken during that time. A Nashville Warbler ate forty-two 

 of these caterpillars in thirty minutes, with many other insects as 

 well, that either could not be plainly seen or fully identified. A 

 Northern Yellow-throat was seen to eat fifty-two caterpillars 

 within a short time. 



A Chestnut-sided Warbler took twenty-eight browntail cater- 

 pillars in about twelve minutes. When we consider that the short 

 hairs on the posterior parts of this caterpillar are barbed like the 

 quills of a porcupine and Will penetrate the human skin, causing 

 excessive irritation and painful eruptions, we may well wonder if 

 the little bird lived to repeat this performance. But many small 

 birds eat these caterpillars at a time when probably the noxious 

 hairs have not fully developed, and others seem to have learned to 

 divest the larger caterpillars of their hairs by beating and shaking 

 their prey and thus loosening the hairs, which are shed as the por- 

 cupine sheds its quills. The insect is then eaten with impunity 

 and even fed to young birds. 



Still other birds reject the external parts of the larvae and, 

 tearing them open, eat only small portions of their viscera. A 

 Black and White Warbler was seen to take twenty-eight of these 

 caterpillars in ten minutes and probably took many more. A Yel- 

 low Warbler ate thirty-three canker worms in a little over six 

 minutes. 



Practically all the Warblers feed very largely at times on 

 measuring worms and other hairless caterpillars. I once noticed 



2 Birds as Protectors of Woodlands, by E. H. Forbush, Forty-eighth Annual 

 Report of the Massachusetts State Board of Agriculture, 1900, p. 303. 



