92 THE INFANCY OF ANIMALS 



breeds in huge colonies. Long-continued heavy rains are 

 as bad as floods, washing away the nests and destroying the 

 eggs of the whole community at once ; droughts are no 

 less disastrous, for then the swamp is converted into a sun- 

 baked plain : the mud necessary for nest-buUding is 

 unobtainable, and again the whole community suffers. 

 There is no breeding that year, unless there be some 

 favoured distant spot yet within range. If the drought 

 comes later, after the young are hatched, matters are still 

 worse, for every one must perish. 



Than the flamingo no bird better illustrates the meaning 

 of the word " speciahsation," or demonstrates the perils 

 arising therefrom. The curious fashion of its beak renders 

 it incapable of any changes in the matter of food : during 

 seasons of plenty it has no competitors but its own kind, 

 but seasons of adversity convert this advantage into a 

 penalty. Too much or too little, as we have just remarked, 

 in the matter of rainfall are matters of life and death; 

 for without a plentiful supply of mud no nests can be 

 built, while an excess of rain may sweep away every nest 

 in the colony and thus the continuation of the race for 

 that season, and perhaps during a succession of seasons 

 is rendered impossible, and thereby the very existence 

 of the species is menaced. If by any other cause their 

 numbers have been reduced, such adverse conditions may 

 end in extinction. 



Few realise how much birds suffer from an excess over 

 what we may call the optimum temperature for the species. 

 That they do so may be one of the underlying factors which 

 have so far escaped students of the mysteries of migration. 

 Those who have pondered this question must often have 

 been struck by the fact that such of our native birds as 

 winter in the tropics are driven by some mysterious factor 



