. Bird-life; a guide to the study of our common birds . d northern Mon-tana. But—and here is the interesting point—these birdsof the far West do not follow their neighbors and migratesouthward through the Great Basin into Mexico, but,true to their inherited habit, retrace their steps, and leavethe United States by the roundabout way of Florida,crossing thence to Cuba, Jamaica, and Yucatan, and mn-tering south of the Amazon. The Bobolinks of Utahdid not learn this route in one generation ; they inheritedthe experience of countless generations, slowly acquiredas the species extended its range we
. Bird-life; a guide to the study of our common birds . d northern Mon-tana. But—and here is the interesting point—these birdsof the far West do not follow their neighbors and migratesouthward through the Great Basin into Mexico, but,true to their inherited habit, retrace their steps, and leavethe United States by the roundabout way of Florida,crossing thence to Cuba, Jamaica, and Yucatan, and mn-tering south of the Amazon. The Bobolinks of Utahdid not learn this route in one generation ; they inheritedthe experience of countless generations, slowly acquiredas the species extended its range westward, and in return-ing across the continent they give us an excellent illustra-tion of the stability of routes of migration. They furnish, too, an instance of one of the mostimportant factors in migration—that is, the certaintywith which a bird returns to the region of its is further evidenced by certain sea birds whichnest on isolated islets to which they regularly returneach year. Of this wonderful homing instinct, which plays so. Plate XIX. Page 109. SHORT-EARED , 1550 inches. Upper parts black, buti, and rusty; under parts whiteand brownish blacli ; eyes yellow. ORIGIN OF MIGRATION. 61 vital a part in the migration of birds, I have no exj^lana-tion to oifer. We know, however, that it exists not onlyin birds but in many other animals. It is this instinct,aided by the heredity of habit, which guides a birdto its nesting ground. The Carrier Pigeon is taught itslines of flight by gradually extending its journeys; aspecies establishes its routes of migration by graduallyextending its range. CHAPTEK V. THE VOICE OF BIRDS.* Aside from the pleasure to be derived from the callsand songs of birds, their notes are of interest to us astheir medium of expression. N^o one who has closelystudied birds will doubt that they have a language, limitedthough its vocabulary may be. Song.—Song is a secondary sexual character, generallyrestricted to the male. With i
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