Chap. XIII. DOUBLE ANNUAL MOULT. 85 



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

 " extraordinary circumstance, that seems to bid defiance 

 " to all human reasoniuir." But he who believes 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 wdthin 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 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 

 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 deciduary margins being- 

 shed. Changes of colour thus caused may last for a 

 lonsfer or shorter time. With the Pelecanus onocrotalus 

 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, dis- 

 *' appearing 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 be- 

 come brighter-coloured, while other finches undergo no 

 such change. Thus the Fringilla tristis of the United 

 States (as well as many other American species), ex- 

 hibits its bright colours only when the winter is past, 

 whilst our goldfinch, which exactly represents this bird 



/8 See Macgillivray, ' Hist. British Birds ' (vol. v. p. 34, 70, and 223), 

 on the niouhing of the AnatidiB, witli quotations from Waterton and 

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



