238 The Bird 
of such a beak, the oysters and other large bivalves 
close with a snap, defying these birds to penetrate their 
living armour. Indeed, more than once a gull or wader 
has rashly pecked at the sweet flesh, when the two tight- 
fitting doors have suddenly closed, pinning the bird help- 
Fic. 180.—Boat-billed Heron. 
Figs. 179 and 180 represent birds with slightly different feeding habits, 
less and holding it captive despite its struggles, until 
the rising tide has ended its life. 
But along comes a bird, well named Oyster-catcher, 
and woe to the mollusks now. It allows them to close 
tightly upon its bill, the mandibles of which are thin 
like blades, many years antedating man’s oyster-knives. 
The mollusk is wrenched free by the sturdy bird, car- 
ried from the water still gripping the bird’s bill, and is 
