220 THE MIGRATION OF BIRDS. 



be said slowly to follow the retreat of wdnter ; in 

 southern latitudes it is much more gradual and 

 broken, just as the grand seasonal change is slower 

 and the summer is long; in higher regions it is 

 rapid and continuous, because seasonal change is 

 quick and the summer is short. In southern 

 regions most migrants are in no great hurry to 

 breed after their arrival — in the extreme south 

 they are remarkably late (later in the basin of 

 the Mediterranean, for instance, than in England) ; 

 but in the Arctic zone the pent-up sexual passions 

 reach their highest pitch before the summer haunts 

 are open. The young of the Common Sandpiper, 

 for instance, are hatched in England before other 

 individuals of this species reach their Arctic breed- 

 ing-grounds ; so that the moment migrants arrive 

 in the high north they generally begin to breed. 

 If they did not do so, the object of their visit 

 would result in failure. Mention has also been 

 made of the route of Migration varying in spring 

 and autumn ; of the change from diurnal to 

 nocturnal flight according to season ; but the 

 data on which these statements rest is remarkably 

 meagre, and suggest a wide and useful field for 

 future investigation. In fact the work before the 

 student of Migration is endless, and as enthralling 

 as it is eternal. Our space utterly forbids us to 

 do more than allude to the southern flight of 

 birds during the Antipodean spring, a subject 

 nevertheless of intense interest and importance. 



