FEATHERED ATHLETES 73 



inexplicable habit of plucking the feathers from its 

 own body and eating them. Naumann says: 

 "These feathers seem to act with the grebe like 

 sand or small stones do with many other birds, as a 

 necessary aid to digestion." 



No movement of a bird seems more wonderful, 

 as far as position is concerned, than flying under 

 water. Of course, water is more difficult for a 

 bird to fly through than air, because of the greater 

 pressure; yet not a few divers and swimmers are 

 masters of this strange art of aquatic-aviation. 

 They might be termed living submarines. These 

 birds have much smaller wings than those of the 

 professional aviators, as large wings would be use- 

 less under water. There are many birds, however, 

 who have to fly both under water and in the air. 

 These are handicapped when under water because 

 they have to fly in the denser medium with aerial- 

 propellers. 



The most skilled submarine birds, the penguins, 

 are no good at aviation. Their wings are nothing 

 but flat paddles, and suitable only for the water. 

 At first sight, one might think the penguin had no 

 feathers at all on its wings, but such is not the 

 case ; while it has no quills, it is covered with scaly- 

 like feathers which are totally unlike all other 

 feathers, 



