1914] GrinneU: Ma))imah and Birds of the Colorado Valley 73 



thronirhoiit the year, chiefly by seepage. These were always located 

 back from the river near the outer edges of the broader valleys, where 

 they were least affected during flood time. They were marked by 

 growths of tules, sedge, and salt-grass, sometimes the latter alone, and 

 were usually surrounded by the arrowweed or willow association (see 

 fig. B). The little open water sometimes attracted a few transient 

 ducks and mudhens, but so far as known no water birds outside of 

 the Ardeidae remain to breed anywhere along the Colorado River. 



As may be noted from the list, but few animals were found to 

 frequent the tule association regularly enough to be considered dis- 

 tinctive features of that association. Of these, Reithrodontomys was 

 the onlv mammal finding its center of abundance there. 



Arrowweed Association 

 BIRDS 



Lophortyx gambeli: miii.; resident Melospiza melodia saltonis: max.; 



(only as a forager) resident 



Geococe^'x californianus: miu.; resi- Melospiza lineolni lincolni: max.; 



dent (only as a forager) winter 



Astragalinus psaltria hesperophilus: Pipilo maculatus curtatus: max.; 



min.; resident winter 



Zonotriehia leucophrys leiicophrys: Oreospiza chlorura: min.; transient 



min.; winter Vireo belli arizonae: min.; summer 



Zonotriehia leucophrys gambeli: Vermivora celata celata: min.; win- 



min.; winter ter 



Melospiza melodia fallax: max.; win- Dendroica townsendi: min.; transient 



ter Oporornis tolmiei: min.; transient 



Peromyseus maniculatus sonoriensis: Sylvilagus auduboni arizonae: min. 



min. Mephitis estor: min. 



Neotoma albigiila venu.sta: min. Spilogale arizonae arizonae: miu. (? 



Perognathus penicillatus penicillatus: 



min. 



Eemarls upon the Arrowweed Association. — In its purity this asso- 

 ciation possesses only one conspicuous plant, the arrowweed (Pluchca 

 se.ricea), which, over extensive areas, grows so densely as to occupy 

 the ground to the exclusion of everything else (pi. 5, fig. 5). This 

 belt of arrowweed u.snally occupies slightly liighcr ground than does 



