Identifier: historyofbirds00pycr (find matches)
Title: A history of birds
Year: 1910 (1910s)
Authors: Pycraft, W. P. (William Plane), 1868-1942
Subjects: Birds
Publisher: London, Methuen and Co
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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ng a strangely unfinishedappearance to this ornament. What is still more strange is thefact that this opening leads directly into a mass of cancellatedtissue. The casque of the Helmet-Hornbill (Rhinoplax vigil)presents something of a mystery, inasmuch as it is com-posed of a mass of ivory-like density, and of great thickness.What can be the use of this structure ? It has been suggestedthat the bird uses it as a hammer for breaking open hard-shelled nuts, and certainly it is a fact that the face of this mass isbruised as if it were put to some such use. Further, the fossaeor cavities which lodge the cerebral hemispheres of the brain,and of the optic lobes, and the septum which dips down be-tween the two cerebral hemispheres in the middle line are un-usually thickened, as though to protect the brain from theeffects of violent shocks. To deaden the force of such shocksthe horny mass is backed by a bony network of props directedforwards and meeting its base at right angles. These mechani-
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ADAPTATIONS 423 cal contrivances to resist and deaden shock all point exclusivelyto the correctness of the surmise as to the use of this ham-mer . Both Hornbills and Toucans live chiefly on fruit, but theformer display a fondness for insect food. The great lengthof the beak of the Toucan has been explained by Bates in hisTravels 071 the Amazons. It is, he says, to enable (it) toreach and devour fruit whilst remaining seated, and thus tocounterbalance the disadvantage which the heavy body andgluttonous appetite would otherwise give it in the competitionof allied groups of birds. The relation between the extra-ordinarily lengthened bill of the Toucan and its mode otobtaining food is therefore precisely similar to that between thelong neck and lips of the giraffe and the mode of browsing ofthe animal. The bill of the Toucan can scarcely be considereda very perfectly formed instrument for the end to which it isapplied . . . but nature appears not to invent organs at oncefor the functions

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