240 THE MIGRATION OF BRITISH BIRDS 



early, and they frequently begin to move south before 

 their moult is completed. These may be regarded as 

 the pioneers, and with their departure the flight south 

 of the young commences. These young often set off as 

 soon as they can fly, and individuals of certain high 

 Arctic species have been observed on the British coasts 

 even with the down of their nestling plumage still 

 adhering to them. Soon after the departure of the bulk 

 of the young the adult males begin to leave their 

 summer quarters, the females following a little later, 

 their moult being delayed somewhat by maternal duties. 

 In the rear of the migration come the laggards — indi- 

 viduals delayed by accidents to their flight feathers, or 

 other casualties. The order of return in spring is to 

 some extent reversed. As usual, the adult males initiate 

 the migration ; then follow the females ; the young of 

 the preceding season follow, and lastly the maimed and 

 weakly individuals. These and the young (or birds of 

 the last season) frequently pass the summer some 

 distance south of the actual breeding grounds, or actually 

 remain in some cases in the winter quarters. 



The daily time of migration also varies considerably. 

 Some species migrate exclusively by day ; others just 

 as regularh- by night ; some by night as well as by day. 

 The punctuality of their arrival and departure is also 

 profoundly interesting ; and it will almost invariably be 

 found to be the rule that the birds that arrive earliest in 

 spring are the latest to depart in autumn ; the latest to 

 arrive in spring being the first to take their departure. 

 I should be disposed to class the former of this class of 

 migrants as much earlier emigrants to the British Area 

 tlian the latter. 



