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ON THE CLASSIFICATION OF BIRDS. 



mouths, both which characters belong to the goatsuckers 

 and the swallows : in both these the mandibles are so 

 weak as to be only capable of clasping small insects ; 

 and it is very questionable whether those of the ordinary 

 Caprimulgidce are ever employed for this purpose, the 

 remarkable smallness of both mandibles rendering them 

 little more than rudimentary. The great majority of 

 birds which catch their food in the air have short bills, 



but of great breadth, as we see in the flycatchers : while 

 those birds which peck their food, like crows and thrushes, 

 have them generally of a moderate length ; or, at least, 

 they are never depressed, as this latter form always im- 

 plies weakness, and an incapacity for striking the bill 

 against any substance. The longest bills are found among 

 the waders (Grallatores, fig. 31. a 6), and such birds as 

 plunge this member into substances which contain their 

 food. The snipes, woodcocks, and many of the godwits, 

 are familiar examples of this structure; and they are 

 well known to insert their bills to a considerable depth 

 in soft mud, for the purpose of finding worms and 

 aquatic insects. This great elongation of the bill, or 

 mouth, as we have had frequent occasion to remark 

 before, is one of the leading characters of the grallatorial 

 type in its different modifications throughout the animal 

 kingdom. We consequently find that the tenuirostral 

 tribes, represented by the humming birds, have the long- 

 est bills (fig. S 1 .c) among the perchers ; and the pigeons 

 are so characterised by this very circumstance in the order 

 of Rasores, although their bills, in comparison with 

 those of the generality of birds, are only moderately long. 



