292 Univi rsity of California Publications in Zoology I VoL - lu 



tain, June L3, this being the aorthernmosl station of observation. 

 Along t lie trail from Vandeventer Flai to Pinon Flat many were 

 noted as far easl as Omstott Creek, 4500 feet to 3000 feet, this 

 being also about the limit in that direction of cither species of 

 Adenostoma. One bird was heard June 23 among the pinons 

 on Pinon Flat, half a mile east of Omstotl ('reck. Several 

 individuals were ooted on a brushy ridge near Garnel Queen 

 .Mine at aboul 6000 feel altitude, this being the most southeastern 

 point of observal inn. 



As already intimated, this vireo is pre-eminently an inhab- 

 itanl of dry chaparral, thus conflicting in range with no other 

 species of the genus. Along the road below Strawberry Valley, 

 towards Keen's ('amp. both this and the western warbling and 

 ('assiu vireos were heard simultaneously. The notes of the latter 

 two, however, resounded respectively from the alder-lined ravine 

 bottoms, and from the golden or black oaks of the cool slopes. 

 while the gray vireo sang from the chamissal mi the hot. steep 

 slopes near Chalk Hill. At Garnel Queen Mine, both the Hutton 

 and gray vireos were heard from the same stand, the former. 

 however, from the golden oaks, the latter, as usual, from the 

 brush hell adjacent. In upper Palm Canon, both the gray and 

 the least vireos were noted in one short stretch, the former in 

 some chamissal straggling down the west wall to the lowest limit 

 of its range, the latter species in some guatemote and chilopsis 

 along tin- stream bed. The presence of no less than five closelj 

 related species of one family in so limited a region is obviously 

 closely dependent upon the separate, sharp, associational and 

 zonal preferments of each. The warbling, Cassin and Hutton 

 vireos are arboreal foragers; the hast and gray vireos brush 

 foragers; hut the least is riparian, while the gray is distinctly 

 a. dry-slope forager. We may surmise that the latter species has 

 only been able to find its way into the avifauna of southern 

 California from a Sonoran center of dispersal, through the exist- 

 ence of an associational niche not occupied by another vireo. 



It was in the vicinity of Kenworthy that most of our study 

 of the gray vireo was carried on. Here the bird was a con- 

 stant accompaniment of the belts of the two species of chaparral 

 bushes, Adenostoma sparsifolium and .1. fasciculatum. While 



