16 MR. W. YARRELL ON THE LAWS WHICH APPEAR TO INFLUENCE 
The most conspicuous changes of plumage appear to be coincident with an altering 
or altered state of the sexual organs. 
The perfection and beauty of a recently acquired plumage compared with its appear- 
ance as the time of moulting approaches, when the sources by which it has been formed 
and nourished are about to be directed to the production of new feathers : 
The power possessed by many birds, particularly the Ducks, of resisting while alive 
the constant action of water, which power is lost after death : 
The fading of the more delicate tints of the plumage soon after life is extinct, as in 
the Goosander and others: and the varieties occasionally seen, generally young and 
weak birds, which, as they increase in health and strength, and obtain in consequence 
natural secretions, put forth by degrees the plumage common to the species,—are addi- 
tional proofs that feathers are influenced by constitutional power, and their colour af- 
fected as the secretions alter under constitutional changes. The remarkable alteration 
observed in some females, particularly among the Gallinaceous birds, when from dis- 
ease, age, or other cause, they are deprived of the influence of the perfect sexual organ, 
and assume in consequence the appearance of the male, is a striking example of an 
alteration in the colour of the feather produced by a constitutional change and its in- 
fluence. 
Montagu was unwilling to believe that the feathers themselves changed colour, as he 
states in the Introduction to his ‘ Ornithological Dictionary’ ; and it is certainly difficult 
to understand how this is so constantly effected in the web of the feather, where no 
vascularity can be shown to exist even when the part is growing: but the fact is cer- 
tain; it has been confirmed by the repeated observations of the Rev. Mr. Whitear and 
Mr. Youell (Linn. Trans., vol. xii. p. 524.) ; and of this fact further proof will be adduced 
in the course of this paper. 
Several birds examined in April were changing the colour of some parts of their 
plumage from that which is peculiar to winter, to that of the breeding season. Many 
of the old feathers obtained at the preceding autumn moult still retained the colours 
they had borne through the winter; others were changing ; and some had entirely as- 
sumed the colours peculiar to the breeding season, bearing precisely the same tints and 
markings as some new spring feathers, the webs of which were only in part exposed. 
This change of colour was particularly noticed among the scapulars, tertials and 
wing-coverts of the black and barred-tailed Godwits, the worn state of the edges of 
the webs and tips of these feathers leaving no doubt of their being old ones. On 
the breasts of several golden Plovers, some of the feathers were entirely white, the 
colour peculiar to all the feathers of that part of the bird in winter; some were 
entirely black, being the colour assumed at the breeding season ; while others bore 
almost every possible proportion of well-defined black and white on the same feathers ; 
from which it appears that the same cause of particular colour in new feathers can also 
partially or entirely change the colour of old ones. 
