€hap. XIII. 
DOUBLE ANNUAL MOULT. 
85 
this double moult withiu so short a time is a most 
extraordinary circumstance, that seems to bid defiance 
to all human reasoning.” 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 within a still 
shorter period, the new male feathers would almost 
necessarily be mingled with the old, and both vdth 
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 
longer 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 
See Macgillivray, ‘ Hist. British Birds ’ (vol. v. p. 34, 70, and 223), 
on the moulting of the Anatidse, with quotations from Waterton and 
'Montagu. Also Yarrell, * Hist, of British Birds,’ vol. iii. p. 243. 
