Feathers 



47 



above, shed every primary in their wings at once, so that 

 their angular stump-feathered wings are perfectly useless 

 for flight. In this class are many water birds — ducks, 

 geese, flamingoes, snake-birds and others. Just before this 

 wholesale moulting occurs, a flock of wild ducks will 



Fig. 29. — Wing of adult Mallard Duck, with the new set of flight-feathers 



just appearing. 



make their way, by an unfailing instinct, to some large 

 body of water where they can swim and dive in safety 

 and, if need be, never come within reach of enemies on the 

 shore until the new feathers are strong enough to bear 

 them up. 



Associated with this temporary- disablement is another 

 provision for the safety of certain birds of this class. Our 

 common Mallard Duck, for example, is sometimes com- 



