and Culoiir-chanye in Birds. 405 



Taking the first paper, that of Mr. Chadbourne, in the 

 ' Auk ' for April 1897, I find that in discussing the moult 

 and colour-change of the Bobolink {Dolichonyx oryzivorus) 

 he lays down the following axioms, which, I may say, entirely 

 agree with my observations as a w^hole : — 



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. 



t 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. 



