STRUCTURE OF BIRDS 



The bill in itself is simply a horny sheath 

 enveloping the jaws. Its primary use would 

 appear to be that of a pair of forceps in order 

 to recompense the bird for the absence of hands. 

 It is an indispensable adjimct in all the affairs 

 of life, though its chief use is to pick up food. 



Birds obtain their food in many diverse ways. 

 The eagle carries its prey to its eyrie, and then 

 tears it limb from Hmb. For this purpose a 

 strong, hooked, sharply-pointed beak is necessary. 

 The shrike, too, is a bird of prey on a smaller scale, 

 and its beak may be Hkened to that of a miniature 

 eagle. The feathers do not reach to the base of 

 the vulture's beak — the neck indeed, is partly 

 bare — otherwise the plumage would become soiled 

 with blood when the fierce bird thrusts its man- 

 dibles deep into the carrion. FHes caught on 

 the wing form the staple diet of the nightjar, 

 hence in this bird length of bill is sacrificed for 

 great width; and flies find it difiicult to escape 

 the gaping jaws, guarded by their array of bristles. 

 We see the same principle at work in the bills of the 

 swifts and swallows. Insect-eating birds, such as 

 the robin and hedge-sparrow, may be distinguished 

 from grain-eaters by their soft, slender beaks, 

 which though excellent for intercepting the darting 

 insect, would be useless for breaking and tearing 

 apart hard shells or husks. For this purpose, 

 sharp, powerful beaks, like those of the finches, 

 are requisite. For the bird nourished on the 

 seeds to be found in pine cones a peculiar and 

 special instrument has been provided. The 

 bent and seemingly misfitting mandibles of the 

 crossbill will be seen to be admirably adapted for 

 the work they have to do. In the woods we may 

 sometimes hear the tap -tap-tap of the wood- 

 pecker, as it sounds the trees, in search of grubs : 



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