465 
and Colour-change in Birds. 
Taking the first paper, that of Mr. Chadbourne, in the 
f Auk , for April 1897, I find that in discussing the moult 
and colour-change of the Bobolink (.Bolichonyx oryzivorus ) 
he lays down the following axioms, which, I may say, entirely 
agree with my observations as a whole:— 
I. “ Because one individual of a given species has moulted, 
it does not necessarily follow that all individuals of that 
species moult also.” 
II. “ In the absence of moulting, an alteration in colour 
must be due to a colour-change in the same feathers ; 
yet it does not follow, on the other hand, that because 
a bird is moulting, a colour-change in the individual 
feathers, be they old or new, is thereby excluded.” 
III. Feather-change and colour-change, in some cases at 
least, do take place separately and entirely independently 
of each other, though the two are also often in progress 
at the same time*. Hence it necessarily follows that 
neither can be the direct cause of the other; but that 
colour-change must be recognized as an independent 
process entirely distinct from so-called moulting.” 
Of course, in axiom ii., “ an alteration in colour ” must be 
restricted to individual feathers, as a general alteration of 
colour may be due to abrasion. Again, in axiom iii., 
colour-change can hardly be regarded as a process entirely 
distinct from moulting, since it sometimes certainly takes 
the place of moult. These, however, are minor points, not 
affecting the general principles. 
It will thus be seen that my remarks on the Corncrake f 
entirely bear out and confirm the last axiom, which certainly 
throws a new light on the question of colour-change, as it 
has always been supposed to be a method by which the 
* It is worthy of notice that this was first observed by Cartwright in 
1792, and has never, so far as I am aware, been again brought forward 
until the present time. See Edinburgh Philos. Journal, ii. (1820) 
pp. 271-276. 
f Zool. January 1900, p. 29; in which it was pointed out that the 
male Corncrake undergoes a complete moult in spring, the new dress re¬ 
sembling its winter plumage. The slate-colour of the breeding-dress is, 
however, assumed immediately after the moult by a change of colour. 
