150 Univeisity of CaUfornia Publications in Zoology [Vol.12 



Nuttallornis borealis (Swainson) 



Olive-sided Flycatcher 



One seen May 6 perched at the top of a willow stub in bottom 

 land on the California side near Pilot Knob. Two seen near the same 

 place, May 10. Undoubtedly migrants. 



Myiochanes richardsoni richardsoni (Swainson) 

 Western Wood Pewee 



First observed April 20, when a male was secured on the California 

 side, eight miles east of Picacho. Next noted at Potholes, April 29 ; 

 thenceforth in small numbers nearly every day, at the stations four 

 miles south of Potholes, five miles northeast of Yuma, and at Pilot 

 Knob. Most numerous at the latter point. May 6 to 12, where as 

 elsewhere they were closely confined to the willow bottoms. Evidently 

 only a migrant through the region. Eight specimens taken, nos. 

 12918-12925. 



There are also in the ^luseum three skins (nos. 4305—4307) taken 

 by J. G. Cooper at Fort INIohave, May 21 and 22, 1861. 



Empidonax diflBcilis difficilis Baird 

 Western Flycatcher 



First noted April 3, on the California side opposite Cibola, observed 

 almost daily thereafter throughout the trip, the last being seen the day 

 we left, May 15. Still, there is no evidence to indicate that the species 

 remains to breed anywhere in the region. The migration appeared not 

 to have reached its height until the second week of May when, in the 

 willows of the bottom lands on both sides near Pilot Knob, western 

 flycatchers were continually in evidence, through their unmistakable 

 notes. 



The fourteen skins preserved (nos. 12896-12909) are representa- 

 tive of the following localities : Arizona side : ten miles below Cibola, 

 five miles north of Laguua; California side: opposite Cibola, eight 

 miles east of Picacho, four miles south of Potholes, Pilot Knob. One 

 specimen (no. 12909) is aberrant in that the lower surface has a 

 peculiar blanched appearance, the sides of the belly and cri.ssum being 



