. On the natural history and classification of birds . it is designated as long (c). Itscircumference assumes threeprincipal forms ; for it is eithercompressed, depressed, or length of a bill is usuallyestimated from that part whichprotrudes beyond the front ofthe head; and not, unless soexpressed, from the angle ofthe mouth to the tip of theupper mandible. We shall 64 ON THE CLASSIFICATION OF BIRDS. mouths, both which characters belong to the goatsuckersand the swallows : in both these the mandibles are soweak as to be only capable of clasping small insects;and it is very questionab
. On the natural history and classification of birds . it is designated as long (c). Itscircumference assumes threeprincipal forms ; for it is eithercompressed, depressed, or length of a bill is usuallyestimated from that part whichprotrudes beyond the front ofthe head; and not, unless soexpressed, from the angle ofthe mouth to the tip of theupper mandible. We shall 64 ON THE CLASSIFICATION OF BIRDS. mouths, both which characters belong to the goatsuckersand the swallows : in both these the mandibles are soweak as to be only capable of clasping small insects;and it is very questionable whether those of the ordinaryCaprimulgidce are ever employed for this purpose, theremarkable smallness of both mandibles rendering themlittle more than rudimentary. The great majority ofbirds which catch their food in the air have short bills,. but of great breadth, as we see in the flycatchers : whilethose 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 billagainst any substance. The longest bills are found amongthe waders (Grallatores, fig. 31. a 6), and such birds asplunge this member into substances which contain theirfood. The snipes, woodcocks, and many of the godwits,are familiar examples of this structure; and they arewell known to insert their bills to a considerable depthin soft mud, for the purpose of finding worms andaquatic insects. This great elongation of the bill, ormouth, as we have had frequent occasion to remarkbefore, is one of the leading characters of the grallatorialtype in its different modifications throughout the animalkingdom. We consequently find that the tenuirostraltribes, represented by the humming birds, have the long-est bills
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