362 THE BIOLOGY OF BIRDS 



appetite and kin-sympathy, efficiency in using weapons 

 and effacement by camouflage. But, in more general terms, 

 considered in its time-relations, it depends on plasticity and 

 an ability to seize opportunities. There must be novelties — 

 the cards to play, and there must be ability to play them well. 

 Birds show that nothing succeeds like success. For their 

 independence of geographical restrictions and their individual 

 freedom of movement give them unusual opportunities for 

 discovering new homes, new corners, new kinds of food, new 

 devices — and they have risen to the occasion. 



