ROOSTING OF BIRDS. 589 



case, the weight of the body, being divided 

 between them, does not stretch the tendons suf- 

 ficiently. In this position the bird not only 

 sleeps in perfect security, but resists the impulse 

 of the wind and the shaking of the bough. 



The great length of the toes of birds enables 

 them to stand steadily on one leg : and in this 



234 



attitude many employ the other foot as a hand ; 

 especially parrots, whose head is too heavy to be 

 readily brought to the ground. Some birds, 

 which frequent the banks of rivers, are in the 

 practice of holding a stone in one foot, while 

 they rest upon the other : this contributes to 

 increase their stability in two ways ; first, it 

 adds to the weight of the body, which is the 

 force that stretches the tendons, and causes 

 them to grasp the bough ; and, secondly, it also 

 lowers the centre of gravity. 



