4 FAMILY ANATIDAE 



Ducks); the hind toe, as in the Pond Ducks, has no flap or lobe; the legs 

 are placed nearer the middle of the body than in the Swans or the Ducks, 

 and the birds are better able to walk on land. 



(d) Windpipe, unlike that of some Swans but like that of the Ducks, 

 is simple, that is, not convoluted in the breast bone. 



(e) Being better walkers than Swans and Ducks, they feed more on 

 land, and are largely vegetable feeders; when feeding in the water, they 

 do so, like Swans and Pond Ducks, by tipping in shallow places. 



(f) The annual moult, like that of the Swans, consists of a single 

 postnuptial moult (Ducks have a double moult), during which the flight- 

 feathers are shed simultaneously and the birds are flightless for a while. 



DUCKS 



Ducks differ from Swans and Geese in the following respects: 



(a) They are generally smaller; the necks are shorter, the body 

 usually longer than the neck; sexes usually are not alike in colour. 



(b) Bill is broad and flat but extremely variable. 



(c) Tarsi are scutellate, that is, fitted with overlapping scales along 

 the front edge, whereas in the Swans and 



Geese the tarsi are reticulate, that is uniform- 

 ly covered with small hexagonal scales; the 

 legs are proportionately shorter (except in the 

 Tree Ducks) and are placed further back than 

 in the Geese; the walk is a characteristic 

 waddle. 



(d) The eggs are usually more numer- 

 ous; the progressive increase of down in the 

 nest as the eggs are laid is characteristic of 

 Ducks. 



(e) Ducks feed less by grazing on land 

 than do Geese. 



(f) The lower end of the windpipe is ^ 5 -~T yp h ica ! foot and 

 variously modified in the males of all Ducks bM f t *'/^ g """ 

 to form a voice-box (fig. 32). 



(g) The annual moult is not a single moult like that of the Swans 

 and Geese, but consists of what might be termed a double postnuptial 

 moult, during which the male, for a short while, assumes a dress similar 

 to that of the female ("eclipse" plumage, described elsewhere), but the 

 flight-feathers, like those of the Swans and Geese, are shed simultaneous- 

 ly, with the result that the birds are flightless for a while. 



The ducks of North America other than the Mergansers, the Ruddy 

 Duck group and the Tree Ducks, fall naturally into two subfamilies as 

 follows: 



