In the spring and summer, you go to field and garden, and you hear and see many birds. As you walk about the woods, you may see a dozen kinds of birds in a few minutes. There will go a yellow-bird, looking like a canary. There, all splendid in black and gold, an oriole is busy building his curious nest. There flies from the swamp a red-wing blackbird. A big woodpecker drums on the nearest tree. A bluebird with a russet breast sits singing on the top rail of a fence. Sparrows, swallows, crows, are everywhere. Out of the grass whirrs up a lark with his brown and yellow coat, and black velvet collar. The thrush sings in a bush. The catbird, in the shade, cheers his mate with a rich, mellow note, and then darts out into the sunshine in his glossy drab dress. But in late autumn, or in winter, you walk abroad, and where are all the birds? A crow may sit, scolding, on a dead limb. A social robin may flit down to your door. The velvet sparrows may be balls of noise and feathers. But where are the other birds? Are they all dead? Oh, no! They have flown off to sunny lands, where they will have mild weather, and food in plenty, and green trees. The birds _migrate_. What is it to migrate? It is to go from one place to another a long way off. They migrate as the season changes. Let us take that pretty bird, the bobolink, as an example of a bird on his travels. In the winter months he is feasting and singing in the warm West India Islands. There he finds grubs, insects, and seeds in plenty. He grows so fat, that they call him the butter-bird. About the first of April, he finds Jamaica too hot for him, and flies over to Georgia, or South Carolina. He settles in the rice-fields, and eats so much rice that he is a great trouble to the planters. They call him the rice-bird. But they are soon rid of him. About the middle of May, the rice-bird, with hundreds of his relations, goes up to Virginia and Pennsylvania. At this time, he eats May-flies, caterpillars, and various insects. But his taste for seeds continues, and he devours the young wheat and barley at a great rate. The farmers name him the reed-bird. Many reed-birds are shot, and sent to market. In spite of the guns, the bobolink seems now in the gayest hour of his life. He sings with all his might, and his black and white coat, with its touches of yellow, is at its best. But again he starts northward. He goes up to New York, and New England, and appears in the orchards and wheat-fields, at the end of May, or the first of June. There he is called, from his song, the bobolink. But Mr. and Mrs. Bobolink must now set themselves to the serious business of making a nest, and rearing a family. They choose a good nest place, and begin to build in a great hurry. Mrs. Bobolink is not so gayly dressed as her mate. She is brown, with a little dull yellow in her plumage.