XXYITI 



BEAKS 



The beaks of birds are formed on the same Hues 

 as tlie horns of antelopes (see p. 26G). There is a. 

 core, formed by prolongations of those Ijones known 

 as the upper and the lower jaw, covered with a 

 modification of skin known as horn ; tliis (.)uter 

 covering, or sheath, is as insensitive as the horn- 

 sheath of a buftalo, goat, sliee]D, or antelope. Tlie 

 l)ase of the sheath (known as- the cere) softens where 

 it becomes continuous with the featlier-cnvered skin 

 on the bird's head. 



The beaks of birds are used for otfensive and defensiNc 

 purposes : also for constructing nests, but abo\'e all 

 things for obtaining food, and for this purpose it is 

 often strangely modified. Long thin Ijcaks are useful 

 for obtainino- worms from soft mud ; and long, .strong 

 and sharp beaks are used by herons and darters to 

 secure sli[ipery creatures like fish. Beaks which are 

 short, but strong and sharp, enal)]e many birds to 

 extract the kernels of nuts, or grubs from the trunks 

 and branches of trees. By means of powerful, sharp, 

 and hooked beaks, birds of prey are able to rend the 

 carcases of animals ; ducks, by means of flat, spatulate 

 lulls, sift mud and ooze to ol)tain tlie organisms 

 necessary for their sustenance ; with their stout lieaks 

 open-bills can break the shells of molluscs and extract 

 the soft animal within. 



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