Page:The New International Encyclopædia 1st ed. v. 13.djvu/529

* MIGRATION OF ANIMALS. 477 MIGUEL. Iiunt us. European ornithologists assert that there the yoimg uf many species precede the adults on their journey southward in the autunni. Cooke and Widman, in tlieir ehiborale Uiporl on Bird Miyralion in the Mississiptii ullcy, say the same for the interior of North America. On the other liand, William Brewster, who has ob- served this matter with the highest zeal and intelligence, maintains the opposite view as the result of long experience in Xew England and Eastern Canada, and declares that the young never precede older birds in the fall, explaining that the first southward flights of adult birds have been overlooked because they were unex- pectedlv early. He has elucidated this with much detail in the Memoirs (No. 1) of the Nut- tall Ornithological Club. That this is the true history of migration in respect to many and various kinds of birds can- not be gainsaid: that it is an allsullicient ex- planation is not universally admitted. The powers of recognition and recollection involved are doubted by some ; yet all animals are strong in this direction — perhaps no mental faculties are so distinctly manifested by brutes as ob- servation and memory. Examples might be drawn from eveiy class, but homing pigeons are most closely to the point. There can be no reason to suppose other birds are less able in this re- spect until we have taken pains to exploit their abilities. No mj'sterious 'homing faculty' need be summoned. The great height at which pigeons usually fly enables them to survey a wide extent of coimtry. and find some points with which they have been previously familiarized ; from this a second is visible and so on, leading the pigeon straight home as the pioneer follows a blazed trail through a forest. Wild birds may be sup- posed to do the same, and their wish to get a very wide view of the landscape explains the height to which they rise in these journeys and their descent and confusion in murky weather. From a height of 10.000 feet both shores of the Mediterranean, for example, would probably be visible to a bird's eye, at any- rate in the nar- rower places where they mostly cross. It must be confessed, however, that this explanation does not cover the ca,se of those birds which migrate aero.ss ocean spaces of one or two thousand miles. Here it seems necessary to believe that they are guided by an intuitive sense of direction — a frelinft for the points of the compass, so to speak. Something so closely akin to this instinctive power of orientation is observable among other animals, including the human savage, that it may be very well conceded to the birds. Bibliography. For references to early essays, and to many essavs and books in European lan- guages, consult Newton, article "Migration," in Dictionary of Birds (London and New York, (18!)3-96), and Giebel, Thesaurus Ornilhologiw (Leipzig, 1872-77); Baiid. "Distribution and Migrations of North American Birds" (three articles), in American Journal of Science and Arts. ser. 2. vol. xli. (New Haven, 1800) ; Allen. "Birds and Weather." in Scribner's Magazine, vol. xxii. (New York, October. 1881) ; Brewster. "Bird Migration." in Memoirs (No. I) of the yuttall Ornithological Club (Cambridge, 1886) : Cooke, Report on Bird Migratioti in the Missis- sipin Valley (United States Department of Agri- culture, Washington, 1888) ; Palmen, translation by .Shoemaker of a report to the International Ornithological Congress at Budai)est, 1891, in Ke/iort of the timithsonian Institution for JS92 (Washington, ISiKi) : (iatke. Die Vogelivarte Helgoland (Brunswick, 1801), translated by Rosenstock as Heligoland us an Ornithological Observatory (Edinburgh, 189.5); Whitlock, The Migration of Birds: A Consideration of Herr Giitke's Views (London, 1897). This combats many of Giitke's statements and theories. Dixon, The Migration of Birds: An Attemj)t to Reduce Arian Season Flight to Law (amended edition, London, 1897), an ambitious book of theory, not well sustained; Beddard, Book of Whales; Scud- der. The Butterflies of New England (Boston, 1886). MIGRATION OF PLANTS. The natural movement of plants from one area to another. This term is thus somewhat in contrast to natu- ralization (q.v.). Migration of species is possi- ble by reason of variations in the structural adaptations which are found in most plants. Among these perhaps the most important are the structures which are concerned in the dis- persal of seeds and spores, which may be scat- tered by means of birds, wind, or water to very great distances. Besides this type of dispersal, certain plants may be scattered in a vegetative wav for great distances and become established far from the original home. Thus the common water weed Elodea is believed to have spread all over Europe vegetatively from a single plant introduced in the early part of the nineteenth century. It seems likely that after a time a certain equilibrium between the various species of the world will have been reached, and that each particular species will be found in the con- ditions best suited to it. When this time comes, further migration would seem to be without re- sult, whether the scattering of seeds takes place or not. It must be remembered, however, that various factors enter in to disturb any equilib- rium which may be formed. In the first place, there are changes in the organic world itself; that is, new species of both plants and animals are developed from time to time through evolu- tion and new disturbances in the so-called equilib- rium must arise. In the second place, the ex- ternal world sutlers tremendous changes. It is probably this last cause which has been most responsible for the migration of plants. Through the geological ages continents have arisen and passed away, and all these changes must have been accompanied b.y changes in the mutual rela- tions of the species then living. C^langes in climate have taken place many times in the world's histon*. and all of these changes must have been attended with great plant, niigrations. To illustrate: the oncoming of the ice epoch caused a southern movement of the climatic zones, and the species which had become adapted to a particular climate moved south to a greater or less degree pari passu with the climatic move- ment. Post-glacial times have witnessed north- ern migrations which are necessarily much slower than the northern migrations of the southern zones. Plants must not be regarded as less active migrants than animals, though they make no seasonal migrations. MIGUEL, mg-gal'. Dnm Maria Evaristo (1802-66). An aspirant for the Portuguese throne, the third son of John VI. of Portugal.