BLACK-POLLED WARBLER 401 



out from tlie concealment of the foliage to capture some passing flying 

 insect with a sharp snap of the bill, after the manner of the flycatcher. 

 At Kent Island, New Brunswick, I have frequently seen them on the 

 terminal branches of the spruce trees feeding upon the spruce gall 

 lice and other insects which infest these trees. All the food that I 

 have seen eaten by the adults or delivered to their young during the 

 nesting season consisted wholly of insects and spiders. 



The blackpoll, like many other species of insect-eating birds, may 

 at times neglect its usual food to take extraordinary numbers of those 

 species which, for any reason become superabundant for a time, thus 

 this bird serves well in doing its part to extirpate serious local infes- 

 tations of insects. E. H. Forbush (1907) cites a case in which war- 

 blers completely eliminated an infestation of plant lice as follows: 



I have had sevei'al opportunities, within the last fifteen years, to watch the 

 checking of insect uprisings by birds. One morning in the fall of 1904 I 

 noticed in some poplar trees near the shore of the Musketaquid a small flock 

 of myrtle and black-poll warblers, busily feeding on a swarm of plant lice. 

 There were not more than fifteen birds. The insects were mainly imagoes, and 

 some of them were flying. The birds were pursuing these through the air, 

 but were also seeking those that remained on the trunks and branches. I 

 watched these birds for some time, noted their activity, and then passed on, 

 but returned and observed their movements quite closely all day. Toward 

 night some of the insects had scattered to neighboring trees, and a few of the 

 birds were pursuing them there ; but most of the latter remained at or about 

 the place where the aphids swarm was first seen, they were still there at sun- 

 down. The swarm decreased rapidly all day, until just before sunset it was 

 difficult to find even a few specimens of the insect. The birds remained until 

 it was nearly dark, for they were still finding a few insects on the higher 

 branches. The next morning at sunrise I went to the trees to look for more 

 specimens. The birds, however, were before me, I was unable to find a single 

 aphis on the trees. 



S. A. Forbes (1883) made an investigation of the food eaten by 

 birds found in a 45-acre apple orchard, in Illinois, heavily infested 

 witli cankerworms. Of the birds collected and their stomach con- 

 tents examined, four blackpolls had eaten cankerworms to the extent 

 of 67 percent of their stomach contents. In addition there were bor- 

 ing bettles (Psenocerus) , 15 percent; other Coleoptera (beetles), 4 

 percent; ants, 4 percent; gnats 4 percent; traces of Hemiptera and 

 mites ; and some undetermined seeds. Samuel Aughey (1878) studied 

 the food of Nebraska birds during the great invasion of Eocky 

 Mountain migratory locusts on the western prairies and plains during 

 the period 1873-1876. The blackpoll was prominent among the birds 

 which preyed upon the locusts. Of four blackpoll stomachs examined, 

 each contained an average of 30 locusts and 12 other insects ; no seeds, 

 grains, or other food was found. Sylvester D. Judd (1902) made a 

 special study of the birds on a Maryland farm. On May 13-15, 1900, 



