THE VERTEBRATE ANIMALS 



309 



as the ostrich and cassowary, 

 are said to belong to the 

 Ratitce. These birds malve 

 up for their lacli: of wing de- 

 velopment by having the legs 

 strong and long. 



The flying birds are 

 further subdivided into a 

 number of orders, the clas- 

 sification based upon the 

 adaptations of different parts 

 of the bird, especially the legs 

 and feet, the wings and the 

 bill, to different functions. We shall not trouble ourselves to learn all 

 the diiierent groups, but shall content ourselves with picking out some of 

 the more evident and important ones, especially those which we might 

 _ meet in field trips. 



I. Perching Birds. — To 

 this order belong most of our 

 common birds, — sparrows, 

 swallows, larks, blackbirds, 

 orioles, kingbirds, and many 

 others well known to e\ery 

 bird lover. In this group the 



Wliite-throatcd sparrow {Zoiiotrtcltlu albicollis). 



toes are so placed, three toes 

 being turned forward and one 

 backward, as to be perfectly 

 adapted to perching. A large 

 number of our sweetest song- 

 sters belong among the perch- 

 ers, the warblers, wrens, 

 thrushes, bluebirds, and, last 

 but not least, our robin. 



II. The Fowls or Gallina- 

 ceous Birds. — This order is 

 of great economic impor- 

 tance. From the jungle fowl, 

 found wild in the jungles of 

 India, most of our domesti- 

 cated fowls have descended. 



A, ptarmigan in winter; B, ptarmigan in 

 summer. How do you account for 

 the change in plumage ? May this 

 change be of use to the bird ? 



