INTRODUCTION. 
XXXI 
most conducive to the wants and necessities of the possessors ; from 
the huge, unshapely beak of the Rhinoceros Bird, and the unwieldy, 
indented one of the Toucan, to the slender bill of the Redbreast, the 
short, and weak one of the Goatsucker, the incurvated one of the Avoset, 
the long one of the Curlew and the Woodcock, the flat one of the Spoon- 
bill, and the strong, firm, angular, and compressed bill of the Turnstone. 
Generally the two mandibles are of equal length ; in some instances the 
upper is longer than the under, as in the Hawk tribe, and rarely the under 
exceeds the superior. The races, formed to seek their food in wet and 
marshy places, are in general provided with bills of extraordinary length, 
or breadth, and with nerves reaching to their extremitAq to enable them to 
find it, even when out of sight. For this purpose, some of these nerves 
line a part of the roof of the mouth. All birds possess them, but they 
that grope for their food have either a greater number, or they extend 
nearer to the extremity of the bill. Those individuals of the feathered 
race, whose principal food is insects, and which hunt for them chiefly on 
the ground, have short, slender bills ; but to the Creeper, which also feeds 
on insects, and is compelled to find them in their retreats, imbedded in 
moss, nature has given a slender, long, and incurvated one. The Wood- 
peckers, the nests of which are formed in the hollows of decayed trees, 
have a firm, strong, sharp bill, well fitted to perforate wood ; and the Gros- 
beak, the principal food of which is kernels and pippins of fruits, or hard 
berries, is possessed of a short, strong bill, admirably contrived for the 
opening of such substances. In the Hawk tribes, which live on animal 
food, and require strong bills for tearing it, nature has extended the upper 
mandible over the inferior, and terminated it in a sharp, exserted angle, 
well adapted for their use. Of these two mandibles, the upper one of 
which the bill is composed, in most birds, is immovable ; but the Parrot 
tribes have the power of moving both mandibles. On the upper mandible 
are situated the nostrils, which, in some birds, as the Kingfisher and the 
Waterouzel, are covered with a membrane; in others, open and broad, as 
in the Goatsucker ; in some, linear and pervious, as in the Rail and the 
