378 



GENERAL ZOOLOGY 



FIG. 195. Foot of Pelican 



ducks, geese, and swans are included here. The bill is usually 

 flattened and is furnished with transverse tooth-like ridges 



on both upper and lower mandibles. 

 In the species which frequent rivers 

 and ponds, feeding largely on vege- 

 table food or on small mollusks, 

 crustaceans, and larvse of insects, 

 these ridges act as a strainer 

 through which the water runs off 

 when the bill is closed, leaving the 



rL Vm ^ 00( * Behind; in the harbor and 



1 i TO sea-haunting, fish-eating species the 



ridges are useful in holding the 

 slippery food. The nest is usually 

 placed on the ground near the water. 

 Several of the swans have the 

 trachea greatly lengthened and 

 looped through the hollow sternum (Fig. 196). By this means 

 they produce their loud whistling or trumpeting note. Wild 

 geese have long excited interest on account of their peculiar 

 manner of migrat- 

 ing in a flock ar- 

 ranged in a long, 

 V-shaped group, 

 keeping up the 

 continual, sono- 

 rous "honk, honk." 

 Among the geese 



and swans the 



FIG. 196. Trachea of Trumpeter Swan 

 sexes are usually 



alike, but in many of the ducks the male is specially orna- 

 mented with brilliantly colored plumage. Well-known species 

 of ducks are the canvasback duck, dear to the epicure ; and 

 the mallard, the ancestor of the common domesticated duck. 



