﻿EXTERNAL ANATOMY. BILL. 6*5 



That the humming birds, and all those which suck the 

 contents of flowers, should have a bill so much length- 

 ened, is owing to the nature of their food, which re- 

 quires the faculty of probing the bottom of those long 

 tubular flowers of the natural order of Bignoniacce, with 

 which the forests of tropical regions abound ; this struc- 

 ture, in fact, is as necessary to them as an elongated mouth 

 is to bees, which feed upon, and have to reach, the very 

 same substance. It may here be observed, and laid 

 down as a general rule, that as a depressed bill always 

 indicates weakness, so one that is compressed on its sides, 

 (that is, whose length is always greater than its breadth), 

 indicates strength. No better proof of this position can be 

 adduced than the genera Platyrhynchus and Megalophus, 

 as examples of the first of these forms; and that of the 

 crows or the parrots, as examples of the second. When, 

 however, the bill is not only short, but so thick as to 

 become almost round or cylindrical, we have exam- 

 ples of the greatest strength with which Nature has 

 endowed the mouth of birds. No group in the orni- 

 thological circle exhibits this powerful structure so much 

 as that of the Fringillidce, where the bill is short, and 

 nearly conic ; both mandibles are equally thick, and 

 when closed, their height and breadth are nearly the 

 same. In many of the finches (as in the sub-genera 

 Amadina, Coccothraustes, &c), the thickness of the bill 

 at its base, in comparison to the size of the head, is 

 enormous : but in the Loocia 

 Ostrina of Vieillot (fig. 32.), 

 a rare and most extraordinary 

 bird from Western Africa, the 

 bill is not much inferior to 

 the size of the head. It is 

 well known that all these 

 " hard-billed" birds, as the 

 old writers aptly called them, feed entirely upon seeds 

 and nuts ; and the harder these are, the stronger are the 

 bills of such species as are appointed to derive nourish- 

 ment from the different sorts. Whenever an insectivorous 



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