THE VERTEBRATES: BIRDS 



215 



almost wingless, and the penguins have the wings so reduced 

 as to be incapable of flight, but serving as flippers to aid in 

 swimming underneath the water. The ostriches and cas- 



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FIG. 111. Cardinal grosbeak, or red bird, Cardinalis cardinalis. (One- 

 half natural size; from life.) 



sowaries also have only rudimentary wings and are not able 

 to fly. Legs are present and functional in all birds, vary- 

 ing in relative length, shape of feet, etc., to suit the special 

 perching, running, wading, or swimming habits of the 

 various kinds. Living birds are toothless, although certain 



