hatched, are helpless in the nests and are unable to feed themselves. Most of the food of young birds consists of the larvæ of insects and some of the families, e.g. the fly-catchers (Fig. 69), feed upon insect food throughout their life. The sparrow family (Fig. 70), on the other hand, choose largely a diet of seeds. Almost every kind of food, however, is eaten by some of the perching birds.

64. Migration of birds. Some of the birds like the

chickadee and downy woodpecker, remain in the middle and northern United States throughout the year, and hence are known as permanent residents of these regions. Many birds, however, spend the winter

in the warmer regions of the South and in the spring months move northward; some of them, like the robin (Fig. 71) and the bluebird, build their nests, rear their young, and stay all summer in northern and middle United States. Such birds are called summer residents. Still other birds rear

their young in Canada

and even farther north,

and come to us only as FIG. 69.-Kingbird. (Courtesy of National

winter visitants. This

Audubon Society.)

seasonal movement of birds is known as migration. Migration is

especially characteristic of the perching birds. For this reason, birds in this, the highest order, are known as "birds of passage."

the

65. Field work on birds. Pupils should become familiar with the size, form, colors, and song of as many birds as possible, and should note carefully where each kind of bird is most commonly found (e.g. in marshes, trees, bushes, or on the ground). In this study bird glasses or opera glasses are very useful. Books like

1 Length of robin from tip of bill to tip of tail feathers, about 10 inches; length of sparrow from tip of bill to tip of tail feathers, about 6 inches.

Chapman's" Bird Life," Wright's "Citizen Bird " and " Birdcraft," Hornaday's "American Natural History," should be frequently consulted. In order to record striking characteristics as a help toward identifying birds, it is suggested that each pupil fill out a table as shown on page 82.

Few animals are more

66. Importance of birds to man. beautiful in form and color than are many of our most common birds, and one of the greatest delights of springtime is to greet the return of the bluebirds, tanagers, thrushes, and others of our feathered friends. "To appreciate the beauty of form and plumage of birds, their grace of motion and musical powers, we must know them. . . . Once aware of their existence, and we shall see a bird in every bush and find the heavens their pathway. One moment we may admire the beauty of their plumage, the next marvel at the ease and grace with which they dash by us or circle high overhead.... The comings and goings of our migratory birds in springtime and fall, their nest-building and rearing of young, their many regular and beautiful ways as exhibited in their daily lives, stir within us impulses for kindness toward the various creatures which share the world with us.. But birds will appeal to us most strongly through their song. When your ears are attuned to the music of birds, your world will be transformed. Birds' songs are the most eloquent of Nature's voices: the gay carol of the grosbeak in the morning, the dreamy, midday call of the pewee, the vesper hymn of the thrush, the clanging of geese in springtime, the farewell of the bluebird in the fall, how clearly each one expresses the sentiment of the hour or season!" Quoted from Bulletin No. 3 of University of Nebraska, and from Chapman's "Bird Life."

The value of birds to man as objects of beauty cannot be measured, it is true, in dollars and cents; but were we to

lose the birds, we should realize all too well how much they contribute to the happiness of every lover of nature. When, however, we come to discuss the economic value of birds, the good that they do cannot be overestimated. Biologists have carried on long series of studies to determine accurately the food of different kinds of birds. This has been done

by watching them while they are eating

or while feeding their young, and by examining the contents of birds' stomachs. The following paragraphs contain descriptions of some of the ways in which birds are of inestimable use to man.

67. Birds as destroyers of harmful insects. Undoubtedly the greatest value of birds to man is the good that they do in destroying injurious insects. In 13-18, 23, and 46, we have described some of the ravages made by our insect foes.

"But if insects are the natural enemies of vegetation, birds are the natural enemies of insects. In the air swallows and swifts are coursing rapidly to and fro, ever in pursuit of the insects which constitute their sole food. When they retire, the nighthawks and whip-poor-wills will take up the chase, catching moths and other nocturnal insects which would escape day-flying birds. Fly-catchers (Fig. 69) lie in wait, darting from ambush at passing prey, and with a suggestive click of the bill returning to their post. The warblers (Fig. 72), light, active creatures, flutter about the