DESTROYERS OF WEED SEEDS 87 



The percentage of weed seeds eaten by some of 

 the more effective weed-seed destroyers are shown in 

 the following table, based on the reports of the 

 Bureau of Biological Survey : — 



Name of bird Per cent of whole food 



that weed seeds form 



Mourning dove 64 



Horned lark 64 



Cowbird 60 



Red-winged blackbird 55 



Chipping sparrow 53 



Bob-white 50 



Song sparrow 50 



Vesper sparrow 42 



Field sparrow 40 



The following table, also based on the reports of 

 the Bureau of Biological Survey, shows the number 

 of different kinds of weed seeds known to be eaten 

 by certain species of birds: — 



Name of bird Number of kinds of 



weed seeds eaten 



Crow blackbird 6 



Rose-breasted grosbeak 14 



Red-winged blackbird 14 



Cowbird 17 



Horned lark 38 



Cardinal 39 



Bob-white 129 



Amounts eaten. As birds are capable of eating 

 enormous quantities of insects, so, too, some eat 

 enormous quantities of weed seeds. It is common for 

 a crow blackbird to eat from thirty to fifty seeds of 

 smartweed, and a field sparrow one hundred seeds 

 of crabgrass, at one meal. Dr. Judd estimated that 



