278 KEY AND DESCB.IPTION 



When disturbed, they leave the water at a bound, and in a 

 few seconds are beyond the gunner's range. 



(5) The Fish Ducks are narrow-billed ducks, with the heads 

 generally crested. They have the lobed hind toe,* and like the 

 sea ducks, dive for their food. Their prey consists of fish, 

 which they pursue under water. There are but three species 

 in North America, of which two are "fishy" food. Only the 

 hooded merganser is good for table use. The saw-like teeth 

 along the nearly cylindrical bilP enable these ducks to capture 

 their prey and give the name sawbills. 



Key to the Subfamilies 



* Neck as long as the body ; tarsus, 4 or more long ; wing, 20 or more ; 



adult entirely white Swans, below. 



* Neck shorter than the body ; tarsus under i long. (A.) 



A. Tarsus, 2-4 long and longer than the middle toe without claw (ex- 

 cept in No. 10, a southern species with a hind toe about 1 long); 



front of tarsus with rounded scales ^ instead of square scutellse 



Geese, p. 280. 



A. Tarsus not over 2 long and shorter than the middle toe without 

 claw; front of tarsus with distinct scutellse.^ (B.) 

 B. Bill nearly cylindrical, only about as wide as high throughout ; ^ head 



in most cases distinctly crested Fish Ducks, p. 304. 



B. Bill always wider than high near tip ; head rarely crested. (C.) 



C. Hind toe with a rounded membranous lobe * Sea Ducks, p. 284. 



C. Hind toe without a lobe-like border ^ River Ducks, p. 297. 



SWANS (SUBFAMILY CYGNIN^) ' 

 Characteristics given on p. 276 



Key to the Species 



* Bare skin in front of eye with yellow ; back end of nostril much nearer 



to the tip of bill than it is to the front corner of the eye 



1. Whistling Swan. 



* Bare skin in front of eye without yellow ; back end of nostril about 



midway between the tip of bill and the front corner of the eye 



2. Trumpeter Swan. 



