168 THE WONDER OF LIFE 



The migration of birds is a seasonal phenomenon, and 

 it seems legitimate to rank among the fundamental facts 

 the contrast that obtains between the autumnal and the 

 vernal movements. There is some uncertainty in regard 

 to various features of the contrast, but that it is marked 

 must be admitted. The autumnal migration, on the 

 whole southwards, is less intense than the return migration 

 in spring. One often observes a good deal of preliminary 

 fuss and not a little dallying before the autumnal migrants 

 get fairly under way. They make trial journeys and may 

 begin their pilgrimage with short stages. The young 

 birds are said to get restless first ; the old males are said to 

 linger longest. It may be that the adults are kept back 

 by the need of recuperation after their family cares, and 

 also by a moult after which the feathers damaged by the 

 summer's wear and tear are replaced. Every one knows 

 the exceptional case of the cuckoo, whose offspring, carefully 

 fostered by other birds, do not leave Britain for six weeks 

 or so after all their real parents have gone. 



In spring, on the other hand, the movement is much 

 more intense, impetuous, and urgent. The adult males 

 seem usually to take the lead, * love-prompted ' ; then 

 follow the adult females ; the immature birds, who will 

 not breed for a season or two, bring up the rear. Thus 

 the vernal order is the reverse of the autumnal order. 

 There is some evidence, also, that the spring journey is 

 more direct than the autumn journey. Shortcuts are found 

 and impelling haste is the characteristic feature. Where 

 the sexes fly separately, it may be that this is because they 

 naturally fly at different rates. 



As a striking illustration of the contrast between the 

 vernal and the autumnal migration movement, we may 



