532 



PASSERINES. 



This wonderful power, however, is only developed at the 

 sacrifice of another locomotive faculty, for they are bad walkers. 

 With their short limbs, activity on their feet is impossible ; and 

 if by chance they are placed on the ground, with difficulty they 



Fig. 240. Window Swallows (Hirundo rustica, Liun.). 



rise again on the wing. On the other hand, their sight is 

 excellent equal to even that of the Eagle or Falcon. According 

 to Spallanzani, who made numerous experiments on the Swallows, 



