CHAPTER XXXV 



THE ALLIES OF THE PIGEON: AVES 



Robins and mocking-birds that all day long 



Athwart straight sunshine weave cross-threads of song. 



Sidney Lanier 



Definition of Aves (Lat. avis f "bird"). The pigeon is a rep- 

 resentative of the class A'ves. Birds are warm-blooded ver- 

 tebrates adapted as a class to an aerial existence. They are 

 covered with feathers, which are, in their origin, modified 

 scales. Birds breathe by lungs. The young are always 

 hatched from eggs in a form closely resembling the parent. 

 There is remarkable uniformity of structure in the class, 

 making classification extremely difficult. 



The following groups, which are some of the most impor- 

 tant of the many divisions into which birds have been di- 

 vided, are not all entitled to rank as separate orders, though 

 often treated as orders. 



The Ostrich and Allies. The group Struthio'nes (Gr. stru- 

 thion, "ostrich") contains the ostrich of Africa, the rheas, or 

 South American ostriches, and the emus and cassowaries 

 of Australia, New Guinea, and adjacent islands. They are 

 all large birds with rudimentary wings, and with only two 

 or three toes on each foot. They have no ridge, or keel, on 

 the sternum, a structure which in most birds serves as an 

 attachment for the muscles of flight ; hence the struthious 

 birds cannot fly, though there is evidence that they have 

 descended from ancestors that had functional wings. The 

 legs are large, and the birds run with great speed. Most of 

 them live in open desert places, though cassowaries inhabit 



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