1914] Grinnell: Mammals and Birds of the Colorado Valley 189 



Vireosylva gilva swainsoni (Bairdj 



Western Warbling Vireo 



First noted April 1, opposite Cibola. Thenceforth of almost daily 

 obser\ation at all our stations from there to Pilot Blnob, where still 

 common May 1-t. At times numerous in the willows ; a few noted in 

 the mesquite belt. Evidently a plentiful migrant through the region. 

 Fourteen specimens taken, nos. 13-537-13.5.50. 



Lanivireo solitarius cassini ("Xantus) 

 Ca.ssin Vireo 



Occurred only in April and as a transient. First seen on the 7th 

 of that month on the Arizona side ten miles below Cibola. One was 

 found on the 9th singing volubly from an iron wood in a desert wa.sh ; all 

 the rest seen were in the willow belt. On the California side, twenty 

 miles above Picaeho, several were noted April 10 and 11. Thereafter 

 none were seen anywhere. Four specimens, nos. 13533-13536. 



There is also in the Museum a skin fno. 4247) taken by J. G. 

 Cooper at Fort Mohave, ilay 14. 1861. 



Vireo belli arizonae Ridgway 

 Arizona Lea.st Vireo 



First detected early in the morning of ilarch 8, on the California 

 shore opposite The Needles. Heard repeatedly the same day from 

 both banks as we floated down to lower Chemehuevis Valley. Xests, 

 a year or more old, were seen both in the \ieinity of The Needles and 

 above, and the inference was that the species arrived throughout the 

 region in full force on the above date. Thenceforth the species was 

 met with at all stations all the way down the river, being one of the 

 most characteristic a^vifaunal elements in the riparian .strip. The bird 

 foraged in aU of the comjjonent associations, but was perhaps best 

 represented in the willow a.ssociation. especially where there was an 

 undergrowth of guatemote ( Baccharis glutinosa). 



On the Arizona side above Bill Williams River. March 14. I was 

 able to make some observations on local di.stribution. Here the wiUow 

 a.ssociation was narrow but well defined, and the vrreos were closely 

 confined to it. A singing male occupied each segment of about 200 

 yards in this belt, just about the same spacing as the Lucy warbler 



