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. 
al 
Fie. 173.—Bill of Merganser, a fish-eating duck. 
Fic. 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. 
