18/0.] NEOTROPICAL ANATID.E. 359 



the districts in which they are found, whilst the latter, with few ex- 

 ceptions, 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 Anatidee 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. We 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- 

 Americau avifauna, on the other hand, we shall handle more briefly, 

 confining our notes and references to such as bear upon their occur- 

 rence in their winter quarters. 



The geographical distribution of the South- American Anatidse 

 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 Anatidse ; 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 



