186 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



that they attack and drive vireos, tanagers, and warblers from their 

 nesting territories." 



Nesting. — E. trailli and miniTnus both build cup-shaped nests, 

 resting in crotches between upstanding shoots or twigs of such trees 

 of low growth as alder and sumac; mrescens swings her nest ham- 

 mock-wise between horizontally spreading twigs. It is a frail, 

 shallow basket of fine, dry plant stems or other fibrous strands, hung 

 by its rim between slender forked twigs. In the region of my own 

 observation (southwestern Pennsylvania), great beech trees stand 

 along the narrow bottomlands of the wooded ravines; the lower 

 branches droop and spread out horizontally toward their leaf- 

 bearing tips; and it is in these places that the flycatchers commonly 

 place their nests. They may hang them at a height of 8 or 10 feet, 

 and often directly over some pool in the course of the stream. 



At the time of nest building (the last week in May) the canker- 

 worms {Paleacrita vernata) are in their heyday. Their threads 

 hang everywhere through the woods, and as one presses through the 

 undergrowth they cling to one's perspiring forehead ; the caterpillars 

 themselves, "measuring worms," caught upon the clothing, climb 

 upward to one's neck. In the hanging threads of silk the falling 

 withered staminate flowers of forest trees and the scales of opening 

 buds are caught. These airy festoons the flycatchers catch up and 

 carry to their nests. In my region, at least, the wild silk so gathered 

 forms an ever-present, and, as I judge, an essential nest-building 

 material. The strands are collected in such quantity as to form a 

 web, and this web commonly swathes the supporting crotch. It 

 spreads upon the nest rim and in it the ends of the frail and loose 

 vegetable fibres are enmeshed. The effect is that the structure, of 

 flimsiest appearance, is in fact adequate to outlast its usefulness. I 

 quote from my own notebook of observations made in Allegheny 

 County, Pa.: "May 30. Acadian flycatchers nest-building at the tip 

 of a pendent lowest branch of a large beech, about 15 feet up, and 

 immediately above the stream. Nest seemingly all but finished. 

 The birds paid little attention to my presence. One, the female 

 presumably, seemed to do all the building. The male called at 

 intervals, and once or twice it flew up as the female came in to the 

 nest. The female kept calling too, more frequently than the male, 

 and continued even when she was in her nest. Her call note is softer 

 than the male's and less emphatic. Once when she was in the nest 

 I heard a reiterated chattering note, and occasionally (also from the 

 nest) a softer, whistled note with falling inflection. Wlien the male 

 approached, the notes of one or perhaps of both birds were softer 

 and more musical. 



