Care of the Young.-After the eggs have been hatched, the young in most cases are quite dependent upon the parents for food. Most young birds are prodigious eaters; as a result they grow very rapidly. It has been estimated that a young robin eats two or Common tern (Sterna hirundo) and young, showing nesting and feeding habits. From group at American Museum of Natural History. three times its own weight in worms every day. Many other young birds, especially kingbirds, are rapacious insect eaters. In the case of the pigeons and some other birds, food is swallowed by the mother, partially digested in the crop, and then regurgitated into the mouths of the young nestlings. Problem XL. How birds are of economic importance. (Laboratory Manual, Prob. XL.) Food of Birds. The food of birds makes them of the greatest economic importance to our country. This is because of the relation of insects to agriculture. A large part of the diet of most of our native birds includes insects harmful to vegetation. Investi Spiders May Beetles Etc. CUCKOO Ants Cut Worms Stink Bugs HOUSE WREN BANK SWALLOW Beetles Spiders Etc. Insects Spiders, Etc. FRUIT gations undertaken by the United States Department of Agriculture (Division of Biological Survey) show that a surprisingly large number of birds once believed to harm crops really perform a service by killing injurious insects. Even the much maligned 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 during 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 insects. Birds use the food substances which are most abundant around them at the time.1 BARN SWALLOW Beetles Etc. GRAIN RED WINGED Beatles Etc. CORN AMERICAN CROW Food of some common birds. 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. ... 1 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. .. I 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 HUNT. ES. BIO - 20 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. Sea birds also live upon shellfish and crustaceans (as small crabs, shrimps, etc.); some even eat lower organisms. The kea parrot, once a fruit eater, now takes its meal from the muscles forming the backs of living sheep. Birds of prey (owls) eat living mammals, including many rodents, for example, field mice, rats, and other pests. Extermination of our Native Birds. - Within our own times we have witnessed the almost total extermination of some species of our native birds. The American passenger pigeon, once very abundant in the Middle West, is now practically extinct. Audubon, the greatest of all American bird lovers, gives a graphic account of the migration of a flock of these birds. So numerous were they that when the flock rose in the air the sun was darkened, and at night the weight of the roosting birds broke down large branches of the trees in which they rested. To-day hardly a single specimen of this pigeon can be found, because they were slaughtered by the hundreds of thousands during the breeding season. At the present time nearly $3000 is offered to the person finding a pair of nesting passenger pigeons. The wholesale killing of the snowy egret to furnish ornaments for ladies' headwear is another example of the improvidence of our fellow-countrymen. Charles Dudley Warner said, "Feathers do not improve the appearance of an ugly woman, and a pretty woman needs no such aid." Wholesale killing for plumage, eggs, and food, and, alas, often for mere sport, has caused the decrease of our birds to 46 per cent in thirty states and territories within the past fifteen years. Every crusade against indiscriminate killing of our native birds 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. should be welcomed by all thinking Americans. Without the birds the farmer would have a hopeless fight against insect pests. The effect of killing native birds is now well seen in Italy and Japan, where insects are increasing and do greater damage each year to crops and trees. Of the eight hundred or more species of birds in the United States, only two species of hawks (Cooper's and the sharp-shinned hawk), the great horned owl, the cowbird, and the English sparrow may be considered as enemies of man. Weed The English Sparrow. The English sparrow is an example of a bird introduced for the purpose of insect destruction, that has done great harm because of its relation to our native birds. Introduced at Brooklyn in 1850 for the purpose of exterminating the cankerworm, it soon abandoned an insect diet and has driven out most of our native insect feeders. Investigations by the United States Department of Agriculture have shown that in the country these birds and their young feed to a large extent upon grain, thus showing them to be injurious The proportions of food of the English sparrow. to agriculture. Dirty and very prolific, Insects Grain 74% it already has worked its way from the East as far as the Pacific coast. In this area the bluebird, song sparrow, and yellowbird have all been forced to give way, as well as many larger birds of great economic value and beauty. The English sparrow has become a national pest, and should be exterminated in order to save our native birds. It is feared in some quarters that the English starling which has recently been introduced into this country may in time prove a pest as formidable as the English sparrow. Geographical Distribution and Migrations. Most of us are aware that some birds remain with us in a given region during the whole year, while other birds appear with the approach of spring, departing southwards with the warm weather in the fall of the year. Such birds we call migrants, while those that remain the year round are called residents. In Europe, where the problem of bird migration has been studied carefully, migrations appear to take place along welldefined paths. These paths usually follow the coast very exactly, although in places they may take the line of coast that existed in former geological times. In this country the Mississippi valley, a former arm of the sea, forms one line of migration, while the north Atlantic seacoast forms another route.1 It has been shown that the southern movement of migratory birds in the fall of the year is not due entirely to the advent of cold weather, but is largely a matter of adjustment to food supply. A migrant almost always depends upon fruits, seeds, and grains as African ostrich (Struthio camelus). part of its food. Most winter residents, as the crow, are omnivorous in diet. Others, as the sparrows, may be seed eaters, but under stress may change their diet to almost anything in the line of food; still others, as the woodpeckers, although insect-eating birds, manage to find the desired food tucked away under the bark of trees. Many insect-eating birds, however, because their food is found on green plants, appear to be forced southward by the cold weather. Classification of Birds. Birds are divided into two great groups, depending on the de velopment of the keel; that is, the part of the breastbone to which the muscles used in flight are attached. a group called the Carinatæ. Hence all flying birds are placed in Birds in which the keel of the breastbone is not well developed, such 1 There is opportunity for a careful observer to learn much of the spring or fall migrations in the particular part of the country in which he resides. All information thus obtained should be sent to the secretary of the American Ornithologists' Union or to W. W. Cooke of the Biological Survey, who has done much to establish what we already know about bird migration in this country. |