212 ACTION OF THE PARROT'S BILL. 



which is expended by a parrot. The tongue is of 

 considerable use in guiding the substance to the most 

 effective part of the mandibles ; and even the motions 

 of the neck are of service in breaking detached sub- 

 stances, as well as in detaching fast ones. 



Very hard substances are broken between the 

 point of the under mandible and the hook of the upper 

 one, the lower side of which is slightly hollowed and 

 roughened like a mill-stone by means of angular fur- 

 rows, with their apices directed towards the tip. 



The bills of the falcon, the crossbill, and the parrot 

 may be reckoned the three most powerful bills in the 

 action of the mandibles that occur in the whole class, 

 and as their action is wholly structural, not deriving 

 any assistance from momentum, they may be reckoned 

 the three most perfect species of mechanism the first, 

 for tearing ; the second, for wrenching open ; and the 

 third, for breaking and bruising ; and all of them are 

 so formed as to have compound motions. 



There are several tolerably distinct forms of bill 

 in this very numerous and abundant family. The 

 parroquets, which fly much from branch to branch in 

 search of their food, have the bill smaller than the 

 others, not exceeding one-third the length of the head, 

 and not very broad ; but it is very firm in its texture, 

 and perhaps proportionably the most powerful of 

 any. The parrots, properly so called, which are the 

 most scandent, have it half the length of the head, 

 and very thick and strong. The cockatoos, which 

 inhabit more marshy places, and live upon softer food 

 than the others, have the bill feebler. The maccaws, 

 which use the wing more than any of the others, and 

 find much of their food on the tops of forest trees, 

 have the bill large, as long as the head, and very 

 sharp. When birds feed wholly or partially on the 



