402 BULLETIN 2 3, UNITED STATES NATIONAL MUSEUM 



he observed blackpolls feeding on mayflies at the top of a cedar tree 

 so heavily infested that it was gray with these insects. On May 17 

 he also found these warblers doing their part in suppressing an infes- 

 tation on pine trees by sawflies {Pteronus). The stomachs of 11 

 specimens collected on the farm revealed that they had also eaten 

 freely of ants, weevils, wasps, and bees. The blackpoll warbler has 

 been known to feed ravenously on winged termites at times when 

 these insects appear in immense swarms. There are numerous reports 

 that in the far north these birds devour hundreds of troublesome 

 mosquitoes. 



In fall the blackpoll eats a few seeds and berries, such as the poke- 

 berry {Phytolacca americana) ^ but they are mainly insectivorous at 

 all seasons. "VVlien passing through Florida in autumn they devour 

 large numbers of spiders and their eggs, plant lice, and scale insects 

 found on the citrous and native plants. It is obvious that the black- 

 poll is useful as an insect-eating bird and that they often play an 

 important role in suppressing insect infestations. 



Voice. — Late in May in New England after the host of warblers 

 have arrived and many of them have passed on their way, we may 

 expect to hear the unpretentious, high-pitched, insectlike but charac- 

 teristic song of the black-polled warbler. It is in full song when 

 it arrives and continues to sing throughout its stay, one of the most 

 frequently heard warbler songs at that season. Its song is not musical, 

 but the ebb and flow of its rapidly uttered series of high-pitched, 

 accented syllables is most agreeable. It sings on the average only 

 two or three times a minute, and seldom more than four times a min- 

 ute, but in any favorable woodland there are sure to be several indi- 

 viduals singing, so that the song is always in evidence. Although 

 these birds may be well hidden by the foliage, the song always assures 

 one of their presence, but it is not always easy to trace to its source, 

 as it has certain deceiving ventriloquial qualities. 



Aretas A. Saunders (1941) gives his analysis of the black-polled 

 warbler's song as follows : "The song of this bird is weak, high-pitched, 

 and much like those of the Bay-breast and Black and White in qual- 

 ity. The commoner form of song is a series of notes all on the same 

 pitch and in even time, but growing louder in the middle and softer 

 again to the end. The number of notes varies from six to eighteen, 

 and the notes are sometimes slow and measured and at other times 

 quite rapid. In a less common form the notes are so rapid as to be 

 uncountable, and the song becomes a trill, swelling in loudness in the 

 middle." 



Ralph Hoffmann (1904) in describing the song writes: "It is a 

 high thin tsit tsit tsit tsit tsit, of a penetrating quality, delivered with 

 a crescendo and diminuendo; the last notes are by some birds run 

 rapidly together with almost a sputtering effect." 



