OCR Text |
Show 1876.] NEOTROPICAL ANATIDiE. 359 the districts in which they are found, whilst the latter, with few consist of winter emigrants from the northern continent. In the intermediate country, comprising by far the larger portion of South America, few members of this family are met with. In speaking of the Anatidae of the Neotropical Region, therefore, our subject very naturally divides itself into two portions, each of which requires somewhat different treatment, owing to the amount of attention they have received from naturalists. W e propose, then, to give a more complete account of those species which belong strictly to the southern continent, including the Antilles and Central America with Mexico. The species which belong to the northern continent and which only come during winter within the limits of the South- American avifauna, on the other hand, we shall handle more briefly, confining our notes and references to such as bear upon their occurrence in their winter quarters. The geographical distribution of the South-American Anatidae requires special consideration, inasmuch as the members of this family found in the Neotropical region, except in a few cases, do not conform in their range to the limits assigned to that region, but to a great extent rally round the more temperate portions of the continent. The characteristic species are in no case met with near the northern boundaries of the Neotropical region. The equatorial genera Dendrocygna and Cairina, however, reach Southern Mexico ; and the former is represented throughout the Antilles. They alone are distributed according to the prevailing law affecting Neotropical birds. Intertropical countries in general are not rich in Anatidae; and America is no exception to the rule. The Tree-ducks (Dendrocygna) form the chief exception. They alone abound in Tropical America, the high Andes (tropical only in position) being, of course, left out of consideration. The cause of this scarcity is not very apparent at first sight. The enormous rivers of tropical America and its numberless lagoons might be expected to be capable of supporting Ducks in any quantity. But such is not the case. The intertropical species are almost all of them arboreal in their habits ; and it may possibly be that this is so because they thus escape being preyed upon by the large Crocodilians which abound in these waters. The bulk of the peculiar South-American species are not found to the northward of the lower portion of the basin of the La Plata. Here, however, and onwards to Tierra del Fuego they abound, not only in species but in individuals, and their numbers would seem to rival those of the northern hemisphere. But the component species, and, in many instances, the genera, are quite different. Swans are there, but the species bear no resemblance to those of the north. The Geese are all different. Anas is there, but differing widely from the northern prototype. The same may be said of Dafila, where the sexes are similarly dressed, instead of being widely different. Mareca is also there; but here, again, the sexes are nearly alike, instead of the reverse. The Teals, too, of the south are very different from those of the north. The host of northern diving and oceanic species |