FLYCATCHEBS 373 



and the Cassin Vireo, which live in the same sort of territory, bear a super- 

 ficial resemblance in size and coloration to the Western Flycatcher; but 

 their voices and manner of foraging are totally unlike the flycatcher's, 

 so that there is no need to confuse these birds with this or with any other 

 of the flycatchers. 



On the morning of June 3, 1915, a Western Flycatcher was watched 

 as it sang and foraged among the big-trunked incense cedars and huge 

 mossy boulders on the north side of the Yosemite Valley, at the foot of 

 Rocky Point. The greenish yellow of the bird's upper plumage and its 

 yellowish under surface were the only sight characters available, but the 

 call note and song were both distinctive. The former was a single high- 

 pitched, even piercing, swee'ip or twee'it; less often a fainter peet was 

 uttered. The song proper goes see'rip, sip, see'rip, or sometimes see'rip, 

 serf, sip, see'rip, and is repeated over and over again, often so continuously 

 that the pauses between songs seem no greater than the intervals between 

 the constituent notes. The syllables were given in varying order, and 

 often the single combination, see^rip, was uttered over and over again. 

 While singing, this bird was perched on various twigs and branches 10 

 to 20 feet above the ground. The song is to be heard most often in May 

 and early June, but as late as July 30 a bird was heard in full summer 

 song. 



Gray Flycatcher. Empidonax griseus Brewster 



Field characters. — As for Wright Flycatcher (which see). Judging from specimens 

 in hand the following features might prove usable in life if the bird be seen at close 

 range and be in fresh, unworn plumage: Coloration as in Wright Flycatcher but paler, 

 more ashy gray; general size slightly greater; bill longer and proportionately narrower, 

 with base of lower mandible pale-colored, rather than dark throughout. Voice: As far 

 as learned, like that of Wright Flycatcher. 



Occurrence. — Summer visitant to lower levels east of the Sierras. Specimens taken 

 in 1916 in Mono Lake district as follows: near William^ Butte, May 6; at Mono Mills, 

 June 8; and on Dry Creek (at 6600 feet altitude) north of Mono Mills, June 11. Also 

 rare transient on west slope of Sierras, at Dudley, 6 miles east of Coulterville (specimen 

 in D. D. McLean collection taken May 20, 1916). Inhabits tracts of large-sized sage and 

 Kunsia bushes. 



When a group of birds is so difficult of field identification as are the 

 small flycatchers, only through long-continued practice can one expect 

 satisfactorily to approach facility in recognizing the species. The Gray 

 Flycatcher is sharply set off from both the Traill and the Western on the 

 ground of voice ; but this test fails absolutely in differentiating the Wright ; 

 and, in our experience, the Hammond has not sufficient individuality 

 always to be identified with certainty. Behavior seems to be identical 

 in the Gray, the Wright, and the Hammond, so that there remain, as 



