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Show 100 JIADITATIONS OF BIRDS. [Ch. VI. one sea m· to th e ot her• But as the occurren.c.e of wolves and ot h er noxt·o us ant'mals ' on both sides the Br1t1sh channel, was adduced by Desmarest, as one of many arguments to prove that England and France were once united, so the. cor~espondence of the aquatic species of the inland seas of Asta w1th those of the Black Sea, tends to confirm the hypothesis for which there ~re abundance of independent geological data, that those seas were connected together by straits at no remote period of the earth's history. Geographical Distribution and Migrations of Birds. We shall now offer a few observations on some of the other divisions of the animal kingdom. Birds, notwithstanding their great locomotive powers, form no exception to the general ru:es already laid down, but, in this class as in plants a~d terres~r1al quadrupeds, different groups of species are c1rcumscr1bed within definite limits. We find, for example, one assemblage in the Brazils, another in the same latitudes in central Africa, another in India, and a fourth in New Holland. But some species again are so local, that in the same archipelago, a single island frequently contains a species found in no other spot on the whole earth; as is exemplified in some of the parrot tribes. In this extensive family, which are, with few exceptions, inhabitants of tropical regions, the American group has not one in common with the African, nor either of these with the parrots of India*. Another illustration is afforded by that minute and beautiful tribe, the humming-birds. The whole of them are, in the first place, peculiar to the new world ; but there, although some-have a considerable range, as the T'rochilus jlammifrons which is common to Lima, the island of Juan Fernandez and the Straits of Magellan t, other species are peculiar to some of * Prichard, vol. i. p. 47. f Captain King, during his late survey, found this bird at the Straits of Magel· Ian, in the month of May, the depth of winter, sucking the flowers of the large species of fuchsia, then in bloom in the midst of a shower of snow. Ch. VI.] THEIR POWF.RS OF DIFFUSION. 101 the West-India islands, and have not been found elsewhere in the western hemisphere. The ornithology of our own country affords a no less striking exemplification of the same law, for the common grouse (Tetrao scoticus) occurs nowhere in the known world except in the British isles. Some species of the vulture tribe are said to be true cosmopolites, and the common wild goose, Anas anser, Linn., if we may believe some ornithologists, is a general inhabitant of the globe, being met with from Lapland to the Cape of Good Hope, frequent in Arabia, Persia, China, and Japan, and in the American continent, from Hudson's Bay to South Carolina*. An extraordinary range has also been attributed to the nightingale, which extends from western Europe to Persia, and still farther. In a work entitled Specchio Comparativo t, by Charles Bonaparte, many species of birds are enumerated as common to Rome and Philadelphia; the greater part of these are migratory, but some of them, such as the long-eared owl, Strix otus, are permanent in both countries. In parallel zones of the northern and southern hemispheres, a great general correspondence of form is observable, both in the aquatic and terrestrial birds, but there is rarely any specific identity; and this phenomenon is truly remarkable, when we reco11ect the readiness with which some birds, not gifted with great powers of flight, shift their quarters to different regions, and the facility with which others, possessing great strength of wing, perform their aerial voyages. Some migrate periodically from high latitudes, to avoid the cold of winter, and the accompaniments of cold,-scarcity of insects and vegetable food ; others, it is said, for some particular kinds of nutriment required for rearing their young: for this purpose, they often traverse the ocean for thousands of miles, and re-cross it at other periods, with equal security. Periodical migrations, no less regular, are mentioned by * Bewiak's Birds, vol. ii. p. 294, who cites Latham. ·1· Pisa, 1827 (not sold). |