146 



ANATOMY OF VERTEBRATES. 



The different degrees of hardness and varieties of form of the 

 beak exercise as much influence upon the nature of Birds as the 

 number and figure of the teeth do upon that of Mammals. 



The beak is hardest in those Birds which tear their prey, as 

 Eagles and Falcons ; in those which bruise hard seeds and fruits, 

 as Parrots and Grosbeaks ; and in those which pierce the barks 

 of trees, as Woodpeckers, in the larger species of which the 

 beak absolutely acquires the density of ivory. The hardness 

 of the covering of the beak gradually diminishes in those Birds 

 which take less solid nourishment, or which swallow their food 

 entire ; and it changes at last to a soft skin in those which feed 

 on tender substances, or which have occasion to probe for their 

 food in muddy or sandy soils, or at the bottom of the water, as 

 Ducks, Snipes, Woodcocks, &c. 



Cceteris paribus, a short beak must be stronger than a long one, 

 a thick one than a thin one, a solid one than one which is flexible ; 

 but the general form produces much variety in the application of 

 the force. A compressed beak T\dth trenchant edges, and a 

 hooked, sharp-pointed end, is the fit instrument for seizing and 

 slaying prey, whether birds, beasts, or fishes ; and such ^ aduncate' 

 beak is seen in the Frigate-bird, Tropic- 

 bird, Albatross, Petrel, fig. 52, but com- 

 bined with length in these piscivorous birds. 

 In the Raptores the beak is shorter and 

 stronger, and in some genera a tooth-like 

 process on either side of the upper man- 

 dible, fig. 60, adds to its destructive 

 power: hence the Falcons, having this armature, are reckoned 

 the more ' noble ' or courageous birds of prey. 



The Shrike {Lanius) and Yanga, which have their bill similarly 

 armed, fig. 61, have the cruel disposition of the 

 Hawk, but take prey proportioned to their small 

 l^ ^^ size : and the ^ tooth' is confined to the horny sheath, 

 fig. 61, not developed on the bone. As the beak 

 becomes straio;hter and conical with the maro^in 



60 



Beak of Falcon. 



Beak of a Shrike. 



entire, the bird is less daring in attacks on other 

 kinds, though occasionally predaceous when large and strong (as the 



Baven and Crow, fig. 62) : but most 

 ' conirostrals ' are omnivorous, and 

 the rest granivorous, as the ' Hard- 

 billed Passeres ' of Ray. When the 

 _____ cone is attenuated and leno-thened 



Beak Of a Crow. out, iig. 63, it IS adapted to extract 



