370 ANIMAL DEFENCES 



remains, and the proverb " as extinct as a dodo ". As Belloc 

 (in The Bad Child's Book of Beasts) pathetically sings : — 



"The Dodo used to walk around, 



And take the sun and air, 

 The Sun yet warms his native ground — 



The Dodo is not there! 

 That voice that used to squawk and squeak 



Is now for ever dumb — 

 Yet may you see his bones and beak 



All in the Mu-se-um." 



A similar fate must overtake any organism suddenly exposed 

 to new and unfavourable conditions, if devoid of sufficient plas- 

 ticity to rapidly accommodate itself to the altered environment. 



Ordinary flying birds naturally betake themselves to flight 

 when attacked, but this is often insufficient to save them from 

 predatory species of their own class. Under such circumstances 

 the flight may be conducted in such a way as to increase their 

 chance of escape. Houssay (in The Industries of Animals) 

 gives a good instance of this, drawing the facts from Naumann 

 i^Naturgeschichte der Vogel Deutschlands): — "Larks, a feeble 

 race of birds, rise higher in the air than any rapacious bird, and 

 this is often a cause of safety. Their greatest enemy is the 

 Hobby [Hypotrioi'-chis sublutes). They fear him greatly, so that 

 as soon as one appears singing ceases, and each suddenly closes 

 his wings, falls to the earth, and hides against the soil. But some 

 have mounted so high to pour out their clear song that they 

 cannot hope to reach the earth before being seized. Then, 

 knowing that the bird of prey is to be feared when he occupies 

 a more elevated position from which he can throw himself on 

 them, they endeavour to remain always above him. They mount 

 higher and higher. The enemy seeks to pass them, but they 

 mount still, until at last the Hobby, heavier, and little accustomed 

 to this rarefied air, grows tired and gives up the pursuit." 



Climbing Birds, such as Woodpeckers, pursue the same kind 

 of tactics as squirrels (see p. 367), working round a trunk or 

 branch so as to keep it between them and the enemy. The 

 powers of diving possessed by many aquatic birds naturally stand 

 them in orood stead when retreating from foes. 



Reptiles in Retreat. — The great majority of reptiles are timid 

 and seek refuge in flight on the first alarm. Some Lizards, when 



