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University of California Publications in Zoology [Vol. 12 



Empidonax griseus: min.; winter 

 Pyrocephalus rubinus mexicanus: 



max.; resident 

 Molothrus ater obscurus: iiiin.; sum- 

 mer 

 Astragalinus psaltria hesperophilus: 



min.; resident 

 Astragalinus lawrencei: excl.; winter 

 Zonotrichia leucophrys leucophrys: 



min.; transient 

 Zonotrichia leucophrys gambeli: min.; 



winter 

 Spizella passerina arizonae: min.; 



winter 

 Pipilo aberti: max.; resident 

 Piranga ludovlciana: min.; transient 

 Phainopepla nitens: max.; resident 

 Vireosylva gilva swainsoni: min.; 



transient 

 Vireo belli arizonae: min.; summer 

 Vermivora lueiae: excl.; summer 



Dendroica auduboni auduboni: min.; 



winter 

 Dendroica nigrescens: min.; transient 

 Wilsonia pusilla pileolata: min.; 



transient 

 Wilsonia pusilla chryseola: min.; 



transient 

 Oreoscoptes montanus: max.; winter 

 Mimus polyglottos leucopterus: max.; 



winter 

 Toxostoma crissale: max.; resident 

 Heleodytes brunneicapillus eouesi: 



min.; resident 

 Auriparus flaviceps flaviceps: min.; 



resident 

 Polioptila caerulea obseura: min.; 



winter 

 Polioptila plumbea: min.; resident 

 Planesticus migratorius propinquus: 



min.; winter 

 Sialia mexicana occidentalis: excl.; 



winter 



Odocoileus hemionus eremicus: min. 

 Peromyscus maniculatus sonoriensis: 



min. 

 Neotoma albigula venusta: max. 

 Perognathus penicillatus penicillatus: 



min. 



Sylvilagus auduboni arizonae: min. 

 Felis oregonensis browni: min. (f) 

 Lynx eremicus eremicus: max. (?) 

 Mephitis estor: max. 

 Myotis calif ornicus pallidus: min. 



Bemarks upon tlic Mesquite Association. — This association is given 

 the vernacular name of what is perhaps the most widely known plant 

 of the region, the mesquite (Prosopis juliflora). Along the Colorado 

 River the mesqnite is closely restricted to a rather narrow belt along 

 the outer edge of the riparian area, mostly above the reach of the 

 highest flood water. This belt is of course lacking where hills closely 

 abut upon the river, save at the mouths of ravines. Along the great 

 valleys it forms a nearly continuous tract consisting of straggling 

 clumps or of well-formed, though small, trees, in the latter case some- 

 times orchard-like in regularity of spacing. At no point did we see 

 mesquites with trunks over eight inches in diameter. 



While evidently requiring abundant water at root, submergence 

 of the ground for any length of time kills mesquites. a.s proven by 



