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University of California Publications in Zoology [Vol.12 



In the case of desert quail there is a double need: of daily access 

 to water, plus that for refuges constantly within easy reach in event 

 of the birds being suddenly threatened by an enemy. The quail-brush 

 association affords the ideal shelter. The futile efforts of a coyote 

 or fox to dash in pursuit into such an interlacing thorny branch-work 

 as is afforded by Atriplex lentiformis can be imagined! 



Fig. E. Diagram showing frequency of capture of Perognathus intermedins 

 in the several associations. Eighty-three individuals were trapped, of which 

 associational occurrence was definitely recorded. 



In these cases and all others it is self-evident that presence of 

 food-supply is the primal associational requisite, whatever other fac- 

 tors may be also essential. And kinds of food produced, with regard 

 to the structural characters of each animal, determine what kinds of 

 associational elements can exist in a locality. An animal having a 

 specialized means of procuring food, like that of a sandpiper, or a 

 woodpecker, or a rock wren, is hemmed in by the bounds outlining the 



