Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/769

Rh NEARCTIC REGION&quot;.] BIRDS 751 cilidce and Hirundinidce, 1 to Ampelidce and Laniidce respectively, 7 to Fringillidce, 2 to Emberizidce, 3 to Cor- vidce, 1 to each of Cypselidce and Alcedinidae, 3 to Picidce, 9 to Strigidce, 10 toFalconidce, 1 to Columbidce, 3toTetra- unidce and Charadrildce respectively, 2 to each of Hcema- topodidce, Recwrvirostridce, and Phcdaropodidce, 7 to Scolo- pacidce, 1 to Ibididce and Plataleidce respectively, 4 to Ardeidce, 1 to Gruidce, 5 to Rallidce, 1 to Ph&nicopteridce, 18 to Anatidce, 1 to each of Sididce, Pelecanidce, and Phalacrocoracidce, 6 to Lartdce, 3 to Procellariidce, 1 to each of Colymbidce and Podicipedidce, and 10 to Alcidce. 1 Thus it will be seen that no less than 57, or more than one- sicrt/i of the whole 330 genera, are purely Land-birds, a very large proportion. The genera which occur both in the Nearctic and Neotro pical Kegions, without appearing in the Palsearctic, must be divided into two categories in order to arrive at a just estimate of the relations of the avifaunas of the first two. These categories consist of those genera which, being only winter visitants to the southern Region, do not breed there, and those which may fairly be called common to both. The latter need perhaps no further attention, after what has been previously said of the Central-American Subregion (p. 748), but the former require some notice. Of those in this category 1 genus belongs to each of the families Sylviidcs and Troglodytidce, 8 to Mniotiltidce, 6 to Embe rizidce, 1 to Icteri/lce, Tmchilidat, Picidce, and Columbidce respectively, 6 to Scolopacidas, and 1 to Plialaropodidce 27 in all. These must, of course, be considered charac teristic of the Nearctic Region, and might, indeed, be not inappropriately added to the 24 genera which are, as already said, peculiar thereto ; but even if this be done, we find the number of peculiar and characteristic genera (taken together) of the Nearctic Region to be only 51 a smaller number than that of the genera of Land-birds alone (57) which are common to the Palaearctic, and considerably less than half the number of all genera which are found on both sides of the Atlantic (128), while the remaining genera which are strictly common to the Neotropical (151) is much larger again. Thus, regarded simply from an orni thologist s point of view, what we call the Nearctic &quot;Region&quot; seems to have no right to be considered one of the primary Regions of the earth s surface, and to be of less importance than some of the Subregions of the Neotropical Region, as may be shewn more plainly by the following table : Whole Xo. of Genera of Birds. Peculiar Genera of Birds. Patagonian Subregion 290 46 Brazilian, , 396 43 Amazonian ,, 373 27 Subandean ,, 469 72 Central- American ,, 464 46 Antillean ,, 140 30 Nearctic Region ... 330 24 It is not, however, intended here to question the validity of the Nearctic Region in a zoogeographical sense. If that position could be successfully disputed, it must be done on more than ornithological grounds, and a consideration of them would be out of place in this article. It is enough to mention that though the Mammals would possibly lead to much the same conclusion as the Birds do, yet the lower Classes of Vertebrates Reptiles, Amphibians, and Fishes would most likely have a contrary tendency, while the present writer is quite unable to guess at the result which would be afforded by the Invertebrates. Now, as in map- 1 Of many American Birds, especially Water-birds, which from time to time occur as stragglers in Europe, no account has here been taken, and, of course, they will not be reckoned in our computation of Pals- arctic genera. ping out the wtorld into zoological Regions all animals have to be regarded, he has no wish to disturb the scheme which has been so generally approved, but contents himself with pointing out that the case for its adoption is not in this particular instance strengthened by the evidence given by the Class Aves. A great majority of the Nearctic families and genera of Division Birds appear to be generally distributed throughout all the into sec- &quot; Subregions,&quot; or perhaps it would be better to call them tlons and &quot; provinces,&quot; into which ingenuity can separate the Region. ia And on this account, as well as from what has been urged in the preceding paragraph, it seems unnecessary to treat of each &quot; Subregion&quot; or &quot; province&quot; so fully as has hitherto been done in the present article. Indeed such districts are not easily defined, and their definition rests rather on differences of species than of higher groups, as we have found to be the case in discussing the several component parts of the other Regions we have considered. Professor Baird, in a masterly treatise on this and another subject, 2 would first divide that portion of North America which constitutes the Nearctic Region into two principal sections, the Eastern extending from the Atlantic sea-board west ward across the Alleghany Mountains and over the valley of the Mississippi and its fertile prairies to about long. 100 W., where the sterile plains begin. The western boundary of this division, however, is not sharply defined, nor does it coincide with any meridian line, but lies some what obliquely and interdigitates with the eastern confines of the next division by extending westward along the river- bottoms. Marching with this irregular frontier we have the second, or Western, great division reac-hing thence to the shores of the Pacific, and though the character of its avi fauna is much the same through and beyond the Rocky Mountains to the eastern slope of the Sierra Nevada and Cascade Mountains of California and Oregon, it changes somewhat on their western slope and thence to the sea, exhibiting modifications which may warrant further sepa ration into a truly Western and a Central subdivision thus making in all three provinces for the whole of the more southern part of the Nearctic Region, while each of them shews, as might be expected, indications of additional change, subject in great measure to the degree of latitude under which any particular locality in them may lie. Having thus pointed out the three provinces into which this portion of the Region can be separated, it may be well to cull from Professor Baird s investigations of the subject some further details. The boundary of the Eastern pro- Allegha- vince, which, taking up an old name, we may perhaps n f an P rf| - term the &quot; Alleghanian &quot; from the principal mountain % range within its limits, starts from the Gulf of Mexico, near the eastern border of Texas, perhaps between the rivers Brazos and Sabine, and folio wing the course of the&amp;gt; former to the great American Desert, in about long. 100 W., runs northward, forced sometimes more or less west ward, especially along the Platte, and sometimes eastward. It crosses the Platte between Forts Kearney and Laramie, and apparently intersects the Missouri about Fort Lookout. Reaching the southern frontier of the Dominion of Canada, it rapidly inclines to the westward, and including the valleys of the Saskatchewan and the Athabasca, it crosses the Rocky Mountains, and, cutting the river Yukon below the junction of the Pelly and the Porcupine, loses itself in the wilds which border the Arctic Ocean. Since the Middle province on which as yet no more precise name Middle- has been bestowed lies for the most part between the province. Alleghanian and the Western or &quot; Californian,&quot; as it has been entitled, the boundaries of this last had best, so far 2 The Distribution and Migrations of North American Birds,&quot; Ameri can Journal of Science and Arts, ser. 2, vol. xli. pp. 78-90, 184-192, 337-347 (January, March, and May, 1866).