8 A NATURAL HISTORY OF THE DUCKS 



form a very compact and sharply differentiated group which has been included in 

 this work. 



We now come to the ducks themselves, the Anatinae, about which there can be 

 little confusion. They are headed by the Sheldrakes of the Old World, birds which 

 show very distinct gooselike characteristics, especially in their habits; and it is pos- 

 sible that at some future time they may be relegated to a subfamily by themselves. 

 The true surface-feeding, or river ducks, of the genus Anas, are the more typical 

 members of the Anatinoe. 



The diving, bay, or sea ducks, subfamily Fuligulince, typified by the Pochards and 

 Scaups, form a more or less natural group, whose members are distinguished not 

 only by different habits and a less elegant form, but by having the hind toe broadly 

 lobed or webbed. The legs are placed somewhat farther back, and the gait is wad- 

 dling. The curious Black-headed Duck (Heteronetta) of South America forms a con- 

 necting link between the surface-feeding and the diving ducks. 



The spiny-tailed ducks, subfamily Erismaturince, include the Ruddy Duck group, 

 and the Musk Duck of Australia. These stiff-tailed diving ducks are characterized 

 not only by their cormorant-like tails, but by their thick-appearing necks, which in 

 the male sex contain curious tracheal air-sacs. 



The Torrent, or Mountain Ducks, Merganettince, are very peculiar, grebelike 

 divers, mostly confined to high Andean streams, having long stiff tails, and a bill like 

 that of a Merganser, but lacking the serrations. 



The Mergince, the last subfamily of the swan, goose, and duck tribe, contains the 

 familiar fish-eating ducks (Mergansers) with their characteristic toothed bills, slen- 

 der bodies, and fish-eating habits. 



The classification of the great suborder Anseres or lamellirostral swimmers may be 

 summed up in the following scheme, which conforms very closely to the one sug- 

 gested by Shufeldt in 1914. 



Suborder Families Subfamilies 



1. Cygnince — Swans 



2. Anseranatince — Semipalmated goose 



3. Plectropterince — Spur-wing family 



4. Cereopsinw — Cape Barren Goose 



5. Anserinae — True geese 



6. Chenonettince — Australian Maned Goose 



7. Dendrocygninoe — Tree Ducks 



8. Anatinoe — Fresh-water, or river, ducks 



9. Fuligulince — Diving ducks 



10. Erismaturince — Spiny-tailed ducks 



11. Merganettince — Torrent, or Mountain, Ducks 

 . 12. Mergince — Mergansers, or sawbills 



Gastornithidoe 

 (extinct) 



Anseres Anatidw. 



(Lamellirostres) 



