NATURAL HISTORY. 311 



" The starling, distinguishable from the rest of the sparrow 

 tribe, by the glossy green of its feathers, in some lights, and 

 purple in others, breeds in caves of houses, ruins, hollow trees, 

 cliffs, and high rocks." GOLDSMITH. 



992. Why are birds enabled to sleep securely when perched 

 on the branches of trees ? 



Because the claws of birds are so organized, that the flexor 

 muscles pass over the joints of the knee and heel in such a manner, 

 that, when the latter bend, they necessarily press on the tendons 

 of the muscles, and make them bend the toe< ; the weight of the 

 body pressing down the thighs and legs, necessarily produces 

 this action ; and, as a consequence, the bird grasps, without 

 effort, the branch on which it is perched, and maintains itself in 

 a fixed position without watchfulness. 



993. Why do starlings frequently accompany roolcs in 

 their flight? 



Because rooks have a more discerning scent than starlings, 

 and lead them to spots productive of food. 



The superior power of finding food is owing to rooks having 

 two large nerves which rim down between the eyes into the upper 

 mandible, which invests their beaks with a more delicate sensitive- 

 ness than other round-billed birds, and enables them to grope for 

 their food when out of sight. 



994. Why are the necks of birds long, and easily moveable? 



Because the beak is generally the only organ of prehension by 

 which they pick their food from the ground ; and the extent of 

 the neck is augmented, in order to admit of the head being 

 brought freely to the ground without incommoding the body. 



995. Sow is the wisdom of the Creator shown in tfo 

 structure of the head and neck of birds ? 



In the heads of birds teeth are dispensed with, and, as a conse 

 quence, along with them, the thick and massive jawbones ittt< 

 which they must have been implanted, and which are replaced 

 by a light strong bill. 



Hence mastication is very limited, and the muscles subservient 



