Chap. XIII.J DOUBLE ANNUAL MOULT. 81 



The common drake (Anas hoschas) is well known after 

 the breeding-season to lose his male plumage for a period 

 of thi'ee months, during which time he assumes that of 

 the female. The 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 extraordinary circum- 

 stance, that seems to bid defiance to all human reasoning. 

 But he who believes in the gradual modification of spe- 

 cies will be far from feeling surprised at finding grada- 

 tions of all kinds. If the male pintail were to acquire his 

 new plumage within a still shorter period, the nfiw male 

 feathers would almost necessarily be mingled with the old, 

 and both with some proper to the female ; and this ap- 

 parently is the case with the male of a not distantly-allied 

 bird, namely the Merganser serrator, 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 bright- 

 ly colored in the spring, not by a vernal moult, but either 

 by an actual change of color in the feathers, or by their 

 obscurely-colored deciduary margins being shed. Changes 

 of color thus caused may last for a longer or shorter time. 

 With the Pelecanus onocrotalus a beautiful rosy tint, with 



plovers, in 'Birds of India,' vol. iii. pp. 617, 637, 709, 711. Also Blyth 

 in 'Land and Water,' 1867, p. 84. On the Vidua, 'Ibis,' vol. iii. 1861, 

 p. 133. On the Drongo Shrikes, Jerdon, ibid. vol. i. p. 435. On the 

 vernal moult of the Herodias bwbulcus, Mr. S. S. Allen, in ' Ibis,' 1863, p. 

 33. On Gallus bankiva, Blyth, in 'Annals and Mag. of Nat. Hist.' vol. 

 i. 1848, p. 455 ; see, also, on this subject, my ' Variation of Animals 

 under Domestication,' vol. i. p. 236. 



■'8 See Macgillivray, 'Hist. British Birds' (vol. v. pp. 34,70,223), 

 on the moulting of the Anatidae, with quotations from Waterton and 

 Montagu. Also Yarrell, ' Hist, of British Birds,' voL iii. p. 243. 



