598 MOULT 
only moult after thé 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.? 
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 BLAckcapP, S. atricapilla, does so but once. The same may 
be said of the HLmberizidex (BUNTING), in which Family both prac- 
tices seem to obtain, but on the other hand, the distinction in this 
respect between the Alaudidx (LARK) and the Anthine (PIPIT), 
belonging to the Family Motacillidx (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 Alaudidx moult- 
ing but once and the Anthinx, conforming to the practice of the 
normal Motacillide (Motacillinx), 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.’ 
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 Abbé Caire (Rev. Zool. 1854, p. 494) independ- 
ently made the discovery of the Triple Moult, and almost simultancously 
announced it (cf. Gloger, Journ. fiir Orn. 1856, p. 461). 
* The fullest list as yet published is that of Meves (Journ. 7. Orr., loc. cit.), 
but it is not entirely free from error. 
