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.”
Man is not alone the possessor of the migrating passion. Menhaden, in vast schools, sweep along our Atlantic Coast in their season. From unknown regions of the ocean herring and salmon return to the streams of their nativity when the spirit of migration sweeps over the shoals into the abysmal depths. There are butterflies that in companies rise from mud puddles beside the road and go dancing away to the South in autumn. The caribou, in long streams, come southward over the barrens of Labrador when the word is passed, and even squirrels, over extended regions, have been known to migrate en masse for hundreds of miles. There is, however, no phase of the life of birds which is quite so distinctive. The extent and duration of their migrations are among the most wonderful phenomena of the natural world.
Ornithologists have gathered much information regarding their coming and going, but knowledge on many of the points involved is incomplete. It is only of recent years that the nest of the Solitary Sandpiper has been found, and yet this is a very common bird in the eastern United States in certain seasons. Where is the scientist who can yet tell us in what country the common Chimney Swift passes the winter, or over what stretches of sea and land the Arctic Tern passes when journeying between its summer home in the Arctic seas and its winter abode in the Antarctic wastes? The main fact, however, that the great majority of birds of the Northern Hemisphere go south in autumn and re-turn in spring, is well known.
Moulting.By the time the young are able to care for themselves the plumage of the hard-working parents is worn and frayed and a new suit of feathers becomes necessary. They do not acquire this all at once. The feathers drop out gradually from the various feather tracts over the body, and their places are at once taken by a new growth. While this is going on the birds are less in evidence than at other times. They keep out of sight and few song notes are heard. Perhaps there is some irritation and unpleasantness connected with moulting which causes a dejection of spirit.
With swimming water birds the wing quills disappear nearly all at once and the birds are unable for a short time to fly; but being at home in the water, where they secure their food, they are not left in the helpless, even desperate, condition in which a land bird would find itself if unable to fly. In a few cases birds begin to migrate before this moulting takes place, but with the great majority the moult is complete before they leave their summer homes.