192 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



and accordingly it is a fair inference that if only we had eyes to 

 see we should discover some peculiarity — in food supply, in all 

 likelihood — that would afford us the reason why this little bird is 

 not widely and generally distributed but found only in restricted 

 areas of specialized sort. 



Prof. Beal's report, informing though it is, does not afford certain 

 guidance in following that inquiry. The food found in a bird's 

 stomach is broken and macerated. Here and there a particular 

 insect may be recognized, but for the greater part it is hardly 

 possible to go beyond family or genus; and, since the genera of 

 insects are widely distributed, one could hardly hope to discover a 

 predominance of forms characteristic of forested ravines. One clue, 

 however, lying in Prof. Beal's data, is this: The score that virescens 

 makes in the consumption of Lepidoptera is exceptionally high. 

 With di-fflcilis, Lepidoptera make up 5.68 percent of the total con- 

 sumption; with traill% 7.73 percent; with minimus^ 7.27 percent; 

 but with virescens Lepidoptera make up 18.87 percent of the whole, 

 and the creatures are largely consumed when in larval state. 

 Among the Lepidoptera, Paleacrita vernata^ the common canker 

 moth, is worthy of note, because it abounds in the haunts of 

 virescens and because, in the northern latitudes at least, the silk that 

 its caterpillar produces is, as has been noted, an invariable and 

 seemingly an indispensable item of this bird's nest-building material. 

 These caterpillars are abundant late in May and early in June; 

 in July they are gone; but after a month or more those of another 

 species succeed them. The indications are quite definite that, in the 

 North at least, the cankerworm fills an important place in the economy 

 of the Acadian flycatcher. 



Behavior. — Generally speaking, virescens is a very inconspicuous 

 bird. It must be sought for to be seen. Throughout the summer 

 it does not leave its woodland habitat, and while nesting its territory 

 may be no more than one or two hundred yards across. It may 

 ordinarily be found perched in deep shade, less than 20 feet from 

 the ground, and well beneath the canopy of foliage. It flits its tail 

 as it calls, and it hawks its prey in the manner common to all fly- 

 catchers. Todd (1940) says that it is shy and suspicious and con- 

 trives to keep well out of sight ; and adds that "like other flycatchers, 

 it is a solitary bird; each pair, after having settled for the season, 

 has its own definite territorial limits beyond which it does not pass 

 unchallenged." Langille (1884), writing from western New York, 

 says: 



In a shadowy part of the woods, where young hemlocks are thickly inter- 

 spersed, I hear sharp, quick notes, pee-wliee, qttee-ree-ee, which I at once recog- 

 nize as those of the Small Oreen-crested Flycatcher {Empidonax acadicus), a 

 very common summer resident of our upland woods. I look sharply into the 



