32 



THE BEAK. 



of a lake, pushing their bills into the thin mud, by 

 repeated thrusts, quite up to the eyes, then drawing 

 them back again with great quickness, and every now 

 and then shifting their ground a little. 



The bills of Ducks and similar birds, which live 

 partly by suction, and partly on small fish or aquatic 

 animals, merit particular notice from their peculiar 

 adaptation to that office. The inside of them, 

 towards the edge, being thickly set wdth rows or 

 lines of short, strong, sharp-pointed prickles. These 

 might be mistaken for teeth; this, however, is not 

 their purpose, which is merely to act as a sort of 

 filter. Observe a duck in a brook, crushing, with 

 that quick motion of his head, soft weeds and other 

 substances mixed wdth the mud. The operation is 

 thus carried on: by plunging its flat bill into the 

 oozy pulp, the finer portion is sucked up through 

 these tooth-like lines; what it chooses is retained, 

 the rest being thrown out and washed away by the 



Beak of the Shoveler Duck. 



rapid clattering motion of the flat-bill. As a fur- 

 ther help, enabling them to judge what is an agreeable 

 and proper food, these birds are furnished with an 

 additional supply of delicate nerves, extending to 



