10 A NATURAL HISTORY OF THE DUCKS 



others, but I lay no claim to much original material. With certain species, however, 

 I am very familiar, both in the wild state and in confinement. 



It is almost impossible to realize the enormous amount of literature which has 

 accumulated around this group of birds. Practically there is no end to it, for it fills 

 the pages of hundreds of local sportsmen's journals all over the world, besides the 

 hundreds of scientific and popular periodicals devoted to natural history. The in- 

 formation of any one person can, therefore, never be complete. Very often, too, 

 extremely interesting accounts can barely be referred to for lack of space. A volume 

 might easily be written upon each of the common palaearctic or nearctic ducks, while 

 on the other hand there is almost no information about many sedentary and island 

 species. Among the little-known birds may be mentioned the Guam Island Duck, 

 Salvadori's Duck from New Guinea, and the Brazilian and Auckland Island Mer- 

 gansers. 



Since Volume 27 of the Catalogue of Birds in the British Museum was published 

 (Salvadori, 1895), the number of species of ducks belonging to the five great sub- 

 families Plectropterince, Anatince, Fuligulince, Erismaturince, and Merginae has scarcely 

 changed at all. Latin names have come and gone with such amazing frequency that 

 only the specialist can attempt to follow them. Genera almost too numerous to men- 

 tion have been suggested, but the tendency is now to make almost all the true sur- 

 face-feeding ducks congeneric. This appears to me the wisest course, for members 

 of the whole genus Anas, as here considered, are probably not only potentially fertile 

 inter se, but would produce fertile hybrids, could the proper conditions be brought 

 about. The Green-winged Teals, for instance, are just as typically surface-feeding 

 ducks as are the larger Mallard-like ducks, both in anatomy and in habits. The Widg- 

 eons form a very obvious and sharply defined little group, and yet it would be easy 

 enough to make a different genus out of each of the three species on anatomical 

 characters alone (trachea, for instance). Indeed, Mr. Alexander Wetmore, who has 

 paid particular attention to skull characters in ducks, has shown me rather well- 

 marked differences in the skulls of closely related species of ducks, so that when all 

 is said and done we get back very nearly where we started from and acknowledge 

 that present classification, no matter what it is based on, is largely a matter of con- 

 venience, and subject to varying opinion. 



A large number of races (subspecies) of ducks have been described in recent years, 

 mostly based upon size characters, and these will be considered at the end of the 

 account of the several species. The species will first be taken up as a unit; its descrip- 

 tion, its distribution, and its habits. 



GENERAL DISTRIBUTION 

 Ducks are found throughout the world, wherever fresh- or salt-water feeding 

 grounds are available, but certain regions are far richer than others, both in species 



