THE VERTEBRATE ANIMALS 



305 



gations undertaken by the United States Department of Agricul- 

 ture (Division of Biological Survey) show that a surprisingly large 

 number of birds once believed to 

 harm crops really perform a serv- 

 ice by killing injurious insects. 

 Even the much mahgned crow 

 lives to some extent upon insects. 

 During the entire year, the crow 

 has been shown to eat about 25 

 per cent insect food and 29 per 

 cent grain. In May, when the 

 grain is sprouting, the crow is a 

 pest, but he makes up for it dur- 

 ing the remainder of the summer 

 by eating harmful insects. The 

 robin, whose presence in the 

 cherry tree we resent, during the 

 rest of the summer does untold 

 good by feeding upon noxious in- 

 sects. Birds use the food sub- 

 stances which are most abundant 

 around them at the time.' 



Not only do birds aid man in his battles with destructive insects, 

 but seed-eating birds eat the seeds of weeds. Our native sparrows 

 (not the English sparrow), the doves, partridges, and other forms 

 feed largely upon the seeds of many of our common weeds. This 

 fact alone is sufficient to make birds of vast economic importance. 



' The following quotation from I. P. Trimble, A Treatise on the Insect Enemies 

 of Fruit and Shade Trees, bears out this statement : " On the fifth of May, 1864, . 

 seven different birds . . . had been feeding freely upon small beetles. . . . There 

 was a great fUght of beetles that day ; the atmosphere was teeming with them. 

 A few days after, the air was filled with Ephemera flies, and the same species of birds 

 were then feeding upon them." 



During the outbreak of Rocky Mountain locusts in Nebraska in 1874-1877, 

 Professor Samuel Aughey saw a long-billed marsh wren carry thirty locusts to her 

 young in an 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 twenty broods to the square mile, would destroy daily 162,771,000 of the 

 pests. The average locust weighs about fifteen grains, and is capable each day of 

 consuming its own weight of standing forage crops, which at .510 per ton would be 

 worth $1743.26. This case may serve as an illustration of the vast good that is 



HUNT. ES. BIO. 20 



Food of some common birds. 



