128 



COACTION: THE INTERRELATIONS OF ORGANISMS 



TABLE 1 



Relative Composition of the Food of Common Birds 



Species 



Species 



Seed 

 Fruit 



In- 

 sects 



White-winged crossbUl . 



Purple finch 



CaUfornia towhee 



House finch 



Phainopepla 



Horned lark 



Blue jay 



Mocking bird 



Song sparrow 



White-crowned sparrow 



Varied thrush 



Redwing blackbird .... 



Bobolink 



Cardinal 



Indigo bunting 



White-throated sparrow 

 American goldfinch .... 



Arkansas goldfinch 



Brewer's blackbird 



Lazuli bunting 



Slate-colored junco 



Yellow-headed blackbird. . 



Towhee 



Chipping sparrow 



Catbird 



Bushtit 



Crow blackbird 



White-breasted nuthatch . 



Brown thrasher 



Robin 



Black-headed grosbeak . . . 



Lark sparrow 



Rose-breasted grosbeak. . . 



% 

 67 

 67 

 67 

 67 

 60 

 60 

 58 

 52 

 50 

 50 

 50 

 43 

 42 

 40 

 40 

 40 



% 

 33 

 33 

 33 

 33 

 40 

 40 

 42 

 48 

 50 

 50 

 50 

 57 

 58 

 60 

 60 

 60 



TABLE 2 



Seasonal Differences in the Food of Granivores 

 (Gabrielson, 1924) 



Species 



Evening grosbeak 

 Pine grosbeak . . . . 



Red crossbill 



Common redpoll . 



Pine siskin 



Snow bunting. . . . 

 Lapland longspur 

 Vesper sparrow. . 



Winter 



Seeds 



Insects 



.4 



Summer 



Seeds 



Insects 



