388 THE DESCENT OF MAN. 



"circumstance, 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 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 neces- 

 sarily 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 serrator, for the 

 males are said to "undergo a change of plumage, which assimi- 

 "lates 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 col- 

 ored 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 American species) exhibits its bright 

 colors only when the winter is past, whilst our goldfinch, which 

 exactly represents this bird in habits, and our siskin, which rep- 

 resents it still more closely in structure, undergo no such annual 

 change. But a difference of this kind in the plumage of allied 

 species is not surprising, for with the common linnet, which 

 belongs to the same family, the crimson forehead and breast are 

 displayed only during the summer in England, whilst in Madeira 

 these colors are retained throughout the year." 



Display hy Male Birds of their Plumage. — Ornaments of all 

 kinds, whether permanently or temporari-ly gained, are sedulously 

 displayed by the males, and apparently serve to excite, attract, 

 or fascinate the females. But the males will sometimes display 

 their ornaments, when not in the presence of the females, as 



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

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

 Montagu. Also Yarrell, 'Hist, of British Birds,' vol. ili. p. 243. 



« On the pelican, see Sclater, in 'Proc. Zool. Soc' 1868, p. 265. On 

 the American finches, s«e Audubon, 'Ornitli. Biography,' vol. i. pp. 

 174, 221, and Jerdon, 'Birds of India,' vol. ii. p. 383. On the Fringilla 

 cannabina of Madeira, Mr. B. "Vernon Harcourt, 'Ibis,' vol v 1863 

 p. 230. 



