Chap. XTU. Double Annual Moult. 393 



that we hero see, as to part of the plumage, a double moult 

 changed under domestication into a single moult.*'' 



The common drake (Anas hoschus) after the breeding- season 

 is well known to lose his male plumage for a period of three 

 months, during which time he assumes that of the female. Tlie 

 male pintail-duck {Anas acuta) loses his plumage for the shorter 

 period of six weeks or two months ; and Montagu remarks that 

 " this double moult within so short a time is a most extra- 

 " ordinary circumstance, that seems to bid defiance to all human 

 " reasoning." But the behever in the gradual modification of 

 species will be far from feeling surprise at finding gradations of 

 all kinds. If the male pintail were to acquire his new plumage 

 within a still shorter period, the new male feathers would 

 almost necessarily be mingled with the old, and both with some 

 proper to the female ; and this apparently is the case with the 

 male of a not distantly-allied bird, namely the Merganser sei-rator, 

 for the males are said to " undergo a change of plumage, which 

 " assimilates them in some measure to the female." By a little 

 further acceleration in the process, the double moult would be 

 completely lost.'^ 



Some male birds, as before stated, become more brightly 

 coloured in the spring, not by a vernal moult, but either by an 

 actual change of colour in the feathers, or by their obscurely - 

 coloured decidiiary margins being shed. Changes of colour thus 

 caused may last for a longer or shorter time. In the Pc/ecanns 

 (inocrotalus a beautiful rosy tint, with lemon-coloured marks on 

 the breast, overspreads the whole plumage in the spring ; but 

 these tints, as Mr. Sclater states, " do not last long, disappearing 

 " generally in about six weeks or two months after they have 

 " been attained." Certain finches shed the margins of their 

 feathers in the spring, and then become brighter coloured, while 

 other finches undergo no such change. Thus the Fringilla tristis 

 of the United States (as well as many other American species) 



^^ For the foregoing statements of the Herodias hub'icus, Mr, S. S. 



in regard to partial moults, and Alien, in 'Ibis,' 1863, p. 33. On 



ou old males retaining their nuptial Gailus bankiva, Blyth, in ' Annals 



plumage, see Jerdon, on bustards and Mag. of Nat. Hist.' vol. i. 1848, 



iind plovers, in ' Birds of India,' vol. p. 455 ; see, also, on this subject, 



iii. pp. 617, 637, 709, 711. Also my Variation of Animals under 



blyth in * Land and Water,* 1867, Domestication,' vol. i. p. 236. 



p. 84. On the moulting of Para- '^ See Macgiilivray, ' Hist. British 



jisea, see an interesting article by Birds ' (vol. v. pp. 34, 70, and 223), 



Dr. W. Marshall, ' Archives Neerlan- on the moulting of the Anatidae, 



iaises,' torn. vi. 1871. On the Vidua, with quotations from Waterton aad 



'Ibis,' vol. iii. 1861, p. 133. On Mcntiigi. Also Yarrell, 'Hist. o< 



'.he Drongo-shrikes, Jerdon, ibid. British Bii'ds,' vol. iii. p. 2*3. 

 rol, i. p. 435. On the vernal movU 



