As soon as the young leave the nest the greedy Cowbird follows the little mother about the thickets, shouting loudly for food. Its fierce clamour drowns the weaker cries of the legitimate young, which I have reason to believe even then often die for lack {58} of nourishment. So insistent is the young Cowbird and so persistently does it pursue the foster parent that it is well cared for and invariably thrives. It is no uncommon sight, during the days of June and July, to see a worn, bedraggled Song Sparrow {59} working desperately in a frantic effort to feed one or more great hulking Cowbirds twice its size. It is little wonder that discerning people are not fond of the Cowbird. Even the birds seem to regard it as an outcast from avian society, and rarely associate with it on friendly terms. This is the only species of North American birds that exhibits such depravity. [Illustration: The Greedy Young Cowbird] All other birds display great willingness to attend to their home duties, and often give evidence of keen delight while so engaged. One of the most exquisite and dainty forms of bird life found in the United States is the little Blue-gray Gnatcatcher. When occupied in building the nest, which is usually saddled on the limb of some forest tree, the birds call to each other constantly; and even after the eggs are laid there is no attempt to restrain their expressions of happiness. Unlike the Crow and Jay, that sometimes appropriate the nests of other birds, these little creatures have no sins to answer for to their neighbours. One of the most pleasing sights I {60} have witnessed was a male Gnatcatcher that had relieved his mate at the nest. He was sitting on the eggs and, with head thrown back, sang with all his might, apparently unconscious of the evil which such gaiety might bring upon his household. {61} CHAPTER IV THE MIGRATION OF BIRDS There is something fascinating about the word migration. It sends our minds back to the dim stories of tribal movements carved on the rocks by men who wrought in the dawn of history. We wonder at the compelling force that drove our ancestors through the forests of northern Germany, or caused the Aztecs to cross the Mexican deserts. It calls to something in our blood, for even the most stolid must at times hearken to the Pied Piper and with Kipling feel that "On the other side the world we're overdue."