236 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI. 



ern range being in accordance with the survival or i^resence of that zone, 

 at least as far south as Belmont. 



Contopus richardsoni (Swains.) Baird. — Western Wood Pewee. 



Common throughout the northern and more timbered regions, but 

 rather rare in the southern interior. It was again met with at Spring 

 Mountain, where it appeared abundant about the beginning of Septem- 

 ber. 



Empidonax difficilis Baird. — ^Western Yellow-bellied Flycatcher. 



This rare species may properly be included in the present list, as its 

 occurrence on the eastern slope of the Sierra N^evada is recorded by Mr. 

 Eidgway. The same writer says also : " It is with little hesitation that 

 we consider this bird as distinct specifically from U. flaviventris. Not 

 only are there very conspicuous and constant differences in proportions 

 and colors (especially the former), but numerous observers have noticed 

 remarkable and important peculiarities in the nesting habits, the pres- 

 ent species almost invariably building its nest in cavities, either of 

 stumps, trees, or rocks, or on beams inside of buiklings, a habit not yet 

 noticed in U. flaviventris, nor indeed in any other species of the genus." 

 Dr. Cooper says, " the differences in the two races seem to be wholly in 

 shades of color and size, and not in proportions, as formerly supposed," 

 which is a mistaken view according to the observations of Mr. Eidgway. 



Empidonax pusillus (Swains.) Baird. — Little Flycatcher. 



Common throughout the watered valleys. Was especially abundant 

 along the Humboldt Eiver and the tributaries from the north, frequent- 

 ing the willow groves. Dr. Cooper noted its occurrence in the Colorado 

 Valley, at Fort Mojave, as early as the 1st of May, where he found sev- 

 eral inhabiting a dark dense thicket. Yarrow and Henshaw found it 

 sparingly in Eastern Nevada. 



Empidonax hammondi (Xantus) Baird. — Hammond's Flycatcher. 



In noting this bird Mr. Eidgway says " it was not met with anywhere 

 as a summer resident, but during its autumnal migration was found to 

 be very common on the East Humboldt Mountains." Its occurrence in 

 the Colorado Valley is noted by Dr. Cooper, who states that he obtained 

 but one specimen at Fort Mojave on May 20. 



Empidonax obscurus (Swains.) Baird. — Wright's Flycatcher. 



This species was found rather common at Bull Eun Mountain as early 

 as May 25, and again at Prospect Hill in June. Dr. Cooper found it at 

 Fort Mojave about Ax)ril 1, and a few afterwards until ]\Iay 25. Mr. 

 Eidgway mentions it as more abundant in the aspen copses of the high 

 canons of the lofty Toyabe range near Austin than anywhere else, while 

 Yarrow and Henshaw found it rather scarce in Eastern Nevada. 



