598 MOULT 



only moult after the breeding-season is over into a grey suit, and 

 then again as autumn passes away into their snowy winter-clothing, 

 but, divesting themselves of this last in spring, at that time put on 

 each a third and most distinctive dress these changes, however, 

 do not extend to the quills either of the wings or tail. 1 



The number of Birds which undergo a more or- less entire 

 Double Moult is very considerable, and the peculiarity is not always 

 characteristic of Families or even, unless in a very restricted sense, of 

 genera. Thus while the Garden- WARBLER, Sylvia salicaria, and the 

 WHITETHROATS, S. rufa and S. curruca, are said to moult twice in the 

 year the BLACKCAP, S. atricapilla, does so but once. The same may 

 be said of the Emberizidx (BUNTING), in which Family both prac- 

 tices seem to obtain, but on the other hand, the distinction in this 

 respect between the Alaudidse (LARK) and the Anthinx (PIPIT), 

 belonging to the Family Motacillidte (WAGTAIL), appears, so far as 

 our knowledge goes, to be invariable, though the habits and general 

 appearance of both groups are so much alike the Alaudidss moult- 

 ing but once and the Anthinse, conforming to the practice of the 

 normal Motacillidte (Motacillinte), twice a year the quills, be it 

 understood, excepted. But it would be impossible here to give 

 more than these few examples, and indeed we scarcely know any- 

 thing of the subject outside of some groups belonging to the 

 Northern hemisphere. 2 



In a large number of species the Additional Moult is very 

 partial, being often limited to certain portions of the plumage, and 

 it is yet an unsolved problem how far some of the changes to be 

 observed are due to actual Moult and how far to the alteration of 

 colour in the feathers themselves, as also the way by which this 

 alteration of colour is produced, whether, as certainly happens in 

 many instances, by the dropping off of the " barbicels " the fine 

 filaments that fringe the "barbules," which are arranged on the 

 upper surface of each " barb " composing the web of the feather 

 or in some other manner. With either of these last considerations 

 we need not now concern ourselves. It is unquestionable that there 

 are innumerable species of birds, the males at least of which put 

 forth in spring decorative plumes unknown at any other season, 

 and it would appear that in some of them the feathers which 

 before clothed the parts whence the newly-donned ornaments grow 

 are doffed to make room for these paraphernalia of marriage. 



1 Macgillivray (Brit. Birds, i. p. 196 ; and Nat. Hist, of Deeside, p. 405) 

 thought there were four moults in this species, but that seems to be one too 

 many. Meves (loc. cit.) and the Abbe Caire (Rev. Zool. 1854, p. 494) independ- 

 ently made the discovery of the Triple Moult, and almost simultaneously 

 announced it (cf. Gloger, Journ. fur Orn. 1856, p. 461). 



2 The fullest list as yet published is that of Meves (Journ. f. Orn., loc. cit.}, 

 but it is not entirely free from error. 



