Beaks and Bills. 



233 



the surface of the water, so close in fact that the lower 

 mandible dips below the surface, thus ploughing a zig- 

 zag furrow and catching up any organisms, shrimps or 

 fish, which chance to be floating on the water. 



Fig. 173. — Bill ot Merganser, a tish-eating duck. 



Fig. 174. — Bill of Shoveller Duck, a bird which strains its food from the mud. 



Among ducks, we find those which feed on fish, and 

 those which sift their food from the mud at the bottom 

 of ponds, and these differ radically in respect to their 

 beaks. The fish-eating merganser has perhaps, of all 

 living birds, the nearest resemblance to a toothed beak. 



