444 



COLLEGE ZOOLOGY 



•••••., 



Fish 



oubmarine 



...•••••••••••; 



Ou I 



Airplane 



Figure 313. Diagrams of living and nonliving things that have a fusiform shape. This shape 

 is characteristic of birds capable of rapid flight and fast-moving objects in air and water. The 

 flightless fossil birds differed about as much in form from the fast-flying birds of today as the 

 first airplanes differed in shape from a modern jet. 



white and song sparrow, possess short 

 rounded wings which enable them to fly 

 rapidly for short distances. Many aquatic 

 birds such as the penguins (Fig. 314), auks, 

 and murres use their wings effectively for 

 swimming and diving. Flightless birds such 

 as the ostrich (Fig. 305), rhea (Fig. 322), 

 emu (Fig. 321), and kiwi (Fig. 305) possess 

 only the remnants of wings, but have very 

 well-developed legs. 



The primitive use of wings was probably 

 for climbing in addition to gliding and fly- 

 ing. Archaeornis (Fig. 331) was provided 

 with three strong claws on its forelimbs. Of 

 living birds, the young of the hoatzin (Fig. 

 315), a peculiar bird inhabiting South Amer- 



ica, is able to climb about before it can fly 

 by the aid of two claws on each forelimb; 

 small claws are found in numerous other 

 species. 



Wings may also serve as organs of offense 

 and defense as in the large waterfowl, or as 

 musical instruments for the "drumming" 

 of the ruffed grouse. 



Tails 



During flight the tail acts as an aerial 

 rudder; a long-tailed bird is able to fly in 

 short curves or follow an erratic course with- 

 out diflSculty. The tail is also used as a brake. 

 It is light and therefore easy to manage, and 

 the tail feathers are firmly supported bv the 



