Footnote 30: 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 flight 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 $10 per ton would be worth $1743.26. 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. And it should be remembered that the nesting season is also that when the destruction of injurious insects is most needed; that is, at the period of greatest agricultural activity and before the parasitic insects can be depended on to reduce the pests. The encouragement of birds to nest on the farm and the discouragement of nest robbing are therefore more than mere matters of sentiment; they return an actual cash equivalent, and have a definite bearing on the success or failure of the crops.--_Year Book of the Department of Agriculture._ [Illustration: Food of some common birds. Which of the above birds should be protected by man and why?] Birds eat Weed Seeds.--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 mourning dove, bobwhite, and other birds feed largely upon the seeds of many of our common weeds. This fact alone is sufficient to make birds of vast economic importance. Not all birds are seed or insect feeders. Some, as the cormorants, ospreys, gulls, and terns, are active fishers. Near large cities gulls especially act as scavengers, destroying much floating garbage that otherwise might be washed ashore to become a menace to health. The vultures of India and semitropical countries are of immense value as scavengers. Birds of prey (owls) eat living mammals, including many rodents; for example, field mice, rats, and other pests.