. Essentials of biology presented in problems. Biology. 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 summe
. Essentials of biology presented in problems. Biology. 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 ; 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 1
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
