THE PHILOSOPHY OF MIGRATION. 67 



the area of their (hstribation northwards, so that 

 their moult which is performed (by the Swallows) 

 in February and March is really normal, that season 

 being the autumn of the Antipodes. The more 

 northerly dispersed Shrikes moult later, in our 

 spring in fact ; but this is only the retention of an 

 autumn moult performed during bygone ages in 

 their ancient southern home. The great majority 

 of migratory birds therefore moult before they 

 migrate, either in spring, or in spring and autumn ; 

 but some few, as, for instance, the Common Sand- 

 piper {Totanus hypoleucus), moult in autumn in 

 their winter quarters just after their migration is 

 over, although in spring the change occurs before 

 passage, as some sort of compensation for the 

 irregular circumstance. No bird of single moult 

 ever migrates in autumn before changing its flight- 

 feathers, and the change is effected just previous to 

 the journey. Normally, and almost without excep- 

 tion, the moult of the quills, whether single or 

 double, comes to an end just before the time of 

 actual migration arrives ; although some birds, as, 

 for instance, several species of Geese {Anser), begin 

 to walk from inland breeding-places en route to the 

 coast or great river valleys, changing their dress 

 as they go, whilst others frequently moult many 

 small body-feathers as they migrate. It must, 

 however, be borne in mind that the change of 

 quills is completed before the actual flight portion 

 of the bird's migration is commenced. During the 

 period of moulting, birds keep very close to their 



