SWANS, GEESE AND DUCKS 



movement in the pursuit of prey; the head is 

 more or less crested; feed almost exclusively 

 on fish. 



(b) The bill is especially constructed for 

 seizing and holding live, active, and slippery 

 prey; the bill is narrow, cylindrical, and slen- 

 der, compared to that of other Ducks; the 

 lamellae, or tooth-like serrations at the edges 

 of the mandibles, are highly developed, rigid, 

 sharp-pointed, and generally inclined back- 

 wards; the "nail" at tip is hooked. 



(c) The tarsi, as in all the true ducks, are 

 scutellate, that is, with overlapping scales on 



FIG. u. -Typical bill and t he front edge; the hind toe has a lobe or flap 

 foot of Merganser, showing as j n t h e Diving Ducks; the feet are large and 

 scutellate tarsus and hind broadly we bbed; the legs are placed well to 



the rear, as in the Diving Ducks (but not so 



far back as in Loons or Grebes); the gait on land is awkward and la- 



boured. 



(d) Lower end of windpipe of males (true of males of all other 



ducks) is modified to form a voice-box (fig. 32); all species show some 



white on the wings in flight, and the flight is seldom high above the 



water. 



RUDDY DUCK GROUP 



Subfamily Erismaturinae (Oxyurinae of Peters) 



There are, in this Subfamily, seven forms 

 of ducks distributed mainly throughout the 

 southern portions of both hemispheres. One 

 of these is regularly found in North America 

 and another, the Masked Duck, visits this 

 continent occasionally. 



This Subfamily is characterized by the 

 following features: 



( a ) These are freshwater ducks of small 

 size a ^f ^edentary habits. 



(b) Tail consists of stiff, spike-like feath- 

 ers, with coverts extremely short, barely cov- 



ering the bases of the tail-feathers. 



(c) Nail of bill, strongly hooked down- 

 ward at the tip and very sharp-pointed. 



(d) Legs, placed even further to rear of 

 body than in the Mergansers and Diving 

 Ducks; these birds are practically unable to 

 walk on land; tarsi very short and scutellate; 



hind toe with lobe, as in Diving Ducks and FIG. 13. Typical foot and 

 Mergansers. bill of Ruddy Duck 



FIG. 12.-Ty P ical Ruddy Duck 



