BIRDS 



245 



school collection. In some cases the general structure of 

 feet and bills may be seen in the live birds by the use of 

 an opera-glass. The characters of bills and feet are much 

 used in the classification of birds, so that any knowledge 

 of them gained primarily in the study of adaptations 

 will have a secondary use in classification work. 



Fig. 199. 



-Ostriches on ostrich-farm at Pasadena, California, 

 from life.) 



(Photograph 



Note the foot of the robin, bluebird, catbird, wren, 

 warbler, and other passerine or perching birds. It has 

 three unwebbed toes in front and a long hind toe per- 

 fectly opposable to the middle front one. This is the 

 perching foot. Note the so-called zj'godactyl foot of the 



