DESTROYERS OF INSECT PESTS 77 



hour. At this rate, for seven hours a day, a brood would 

 consume 210 locusts per day, and the passerine birds of 

 the eastern half of Nebraska, allowing only 20 broods to 

 the square mile, would destroy daily 162,771,000 of the 

 pests. The average locust weighs about 15 grams, and is 

 capable each day of consuming its own weight of standing 

 forage crops, corn and wheat. The locusts eaten by the 

 nestlings would therefore be able to destroy in one day 

 174.397 tons of crops, which at $10 per ton would be 

 worth $1743.97. This case may serve as an illustration 

 of the vast good that is done every year by the destruction 

 of insect pests fed to nestling birds. 



Number of insects destroyed by birds in the 

 eastern United States. Birds feed their young, on 

 an average, about two hundred insects a day. If we 

 take fifteen days as the average time that young 

 birds remain in the nest, the young during this time 

 would devour about three thousand insects. A 

 recent bird-census of the United States, made by the 

 Bureau of Biological Survey, showed that there was 

 an average of one pair of birds per acre on the farms 

 of the eastern United States. East of the Mississippi 

 River there are about 375,000,000 acres of farmland 

 supporting an equal number of pairs of birds. These 

 birds in rearing one brood of young would destroy 

 about 1,100,000,000,000 insects. This is the amount 

 for only two weeks eaten by the young birds alone 

 while in the nest. To get some conception of the 

 total amount of food eaten by all birds, to this must 

 be added the insects eaten by the second and third 

 broods which some species raise, those eaten by the 



