BIRDS 87 



to Agriculture," the writer estimated that in the state of 

 Iowa during the six months of fall and winter, tree sparrows 

 devoured 875 tons of weed seed. An actual count of the 

 stomach contents of a bobwhite showed the presence of 

 400 pigweed seeds. In the stomach of another were 500 

 seeds of ragweed. 



69. Birds as destroyers of rats and mice. We learned 

 in 61 that hawks and owls by their hooked bills and claws 

 are admirably fitted to clutch and tear living prey. It 

 has been demonstrated that the food of many of these birds 

 consists almost wholly of small gnawing mammals (e.g. 

 field mice) (Fig. 64) which are exceedingly injurious in fields 

 of grain. An examination of the stomachs of fifty short- 

 eared owls (Fig. 65) showed that 90 per cent of them contained 

 nothing but mice. Forty of the forty-nine stomachs of the 

 rough-legged hawks were found to contain mice, while most 

 of the rest contained injurious animals. 



70. Birds as scavengers. Some birds of prey, like the 

 turkey buzzards of the Southern states, eat animals that are 

 dead. " These animals may be seen at all hours of the day 

 sailing through the air in majestic circles or lazily resting 

 on stumps or trees after a feast of their filthy food. They 

 perform an important service as scavengers, disposing of all 

 sorts of animal matter that would pollute the air. On this 

 account they are seldom molested by man and in some 

 States are protected by law. They devour both fresh and 

 putrid meat. . . . They are known sometimes to capture 

 live snakes and to attack helpless animals of many kinds. 

 Along the seashore they feed upon dead fish cast up by the 

 waves." WEED and DEARBORN, " Birds in their Relations 

 to Man." Gulls (Fig. 59) also serve a useful purpose by 



