368 



ANIMAL DEFENCES 



is largely compensated by the specialization of the legs for the 

 purpose of rapid movement on the ground. For straightforward 

 retreat in open country nothing could be more effective; but 

 another kind of adaptation is required in birds like Rails, which, 

 though belonging to the Flying Birds, are deficient in powers. 





Fig. 508. The Common Squirrel (Sciurus vidgaris) 



of flight, and yet are able to run through thickly-growing vege- 

 tation with such rapidity as to commonly elude their enemies. 

 This is rendered possible by the shape of their bodies, which are 

 relatively narrow and flattened from side to side, so as to easily 

 slip between the stems of grasses, rushes, and similar plants. 

 Anyone who has pursued our native Land- Rail or Corn- Crake 

 (Crex pratensis] with intent to capture will have noted how 

 extremely difficult it is even to get within sight of a bird of this 

 sort. Certain birds, unfortunately for themselves, have lost the 



