MEALY REDPOLL. 139 



arctic winter by an exti-aordinary growth of plumage, their 

 new feathers, assumed at the autumnal moult, hearing very 

 long white fringes, which not only greatly change the appear- 

 ance of the birds, by almost entirely masking their darker 

 colours, but form a warm clothing that affords the wearers 

 an efficient protection against the rigours of the climate. 

 This growth indeed takes place in all, but among those 

 which flee from the severity of the northern regions at this 

 season it bears no comparison as to extent with that which 

 obtains among those that abide under high latitudes and 

 thus muffled in their thick vestments await the return of 

 spring. 



But another and yet more remarkable seasonal change 

 occurs in these birds, of which Wolley during his long resi- 

 dence in Lapland seems to have been the first observer, 

 though his full explanation of it has not been made public* 

 It had long been known that examples differed greatly in the 

 size and especially in the length of the bill, and many 

 naturalists were inclined to believe that this difference indi- 

 cated two races, if not species, of Kedpoll.f A certain amount 

 of it indeed was obviously rather apparent than real, being 

 due to the length of the feathers on the bird's face, and thus 

 the bill of a specimen obtained in winter always seemed much 

 shorter than that of one procured in summer ; but from re- 

 peated examination of birds killed out of the same flock he 

 satisfied himself that during the latter season the horny 

 covering of the mandibles was constantly growing longer, 

 and attributed the fact to the softer nature of the food 

 then eaten, observing that when winter really set in, and the 

 birds were living solely on hard seeds, the edges and tip of 

 the mandibles were rapidly worn down, so that the bill at the 

 beginning of spring became considerably shorter than it 

 was at the end of the preceding summer. If this mode 



* Wolley's residence extended over five summers and three winters : his views 

 on this subject were first made known to the Editor in 1855. They are con- 

 firmed by Gloger's happy conjectures published some eighteen months afterwards 

 (Journ. fiir Orn. Nov. 1856, pp. 433-440). 



t The large-billed birds were described by Brehm (Handb. p. 280) in 1831 

 as forming a distinct species which he called Linaria holboelli. 



