446 THE DESCENT OF MAN. 



The common drake {Anas hoschas) 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. The male pin-tail 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 cir- 

 cumstance that seems to bid defiance to all human reason- 

 ing." But the believer in the gradual modification of 

 species will be far from feeling surprise at finding grada- 

 tions of all kinds. If the male pin-tail 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 appar- 

 ently 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 com- 

 pletely lost.* 



Some male birds, as before stated, become more brightly 

 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. 

 In the Pelecanus onocrotalus a beautiful rosy tint with 

 lemon-colored 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 colored, while other 

 finches undergo no such change. Thus the Fringilla 

 tristis of the United States (as well as many other Ameri- 

 can species) exhibits its bright colors only when the winter 

 is past, while our goldfinch, which exactly represents this 

 bird in habits, and our siskin which represents it still more 

 closely in structure, undergo no such annual change. But 

 a difference of this kind in the plumage of allied species 



*See Macgillivray, "Hist. British Birds," (vol. v, pp. 34, 70, 223) 

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

 Montagu, Also Yarrellj " Hist, of British Birds," vol. iii, p. 243. 



