82 tHE BIOLOGY OF THE SEASONS 



and, speaking in the same rather vague manner, we may 

 say that the spring-tide is moved by " love " and the 

 autumnal - tide by "hunger." Although the subject 

 requires more exact study, we may admit that there 

 is some truth in what many observers have stated as to 

 a difference in the character of the movement at the two 

 seasons. 



The Autumnal movement is relatively less intense ; 

 there is more dallying at least, till they get fairly agoing. 

 In some cases, as Mr. Eagle Clarke points out, the reason 

 is obvious : " Food is still abundant in their favourite 

 resting haunts, and there is no particular hurry to move 

 southwards." 



Of the Spring movement, Gatke says " unrest and 

 impelling haste are everywhere the prominent characters " ; 

 there is no division of the journey into stages, nor any 

 tendency to long spells of rest. "Das ewig weibliche zieht 

 sie heran." 



As to the order of flight, likewise, one wishes that there 

 were more security. Gatke's conclusions in regard to the 

 396 birds studied in passage at Heligoland were, in the 

 main, three : that the Autumn migration is (with one ex- 

 ception) initiated by the young birds, which begin to move 

 about six or eight weeks after they leave the nest ; that 

 the parents of these young birds do not get restless till 

 a month or two months later ; and that among the adults 

 the handsomest old males are the last to set out on the 

 migratory journey. In Spring this order of succession is 

 reversed ; the gay old males are the first to arrive, and the 

 immature young birds come last. The exception referred 

 to above is, of course, the cuckoo, for the parents leave 

 long before the young ones, which they have foisted on to 

 the care of other birds. 



In his World of Life a remarkable achievement for a 



