286



Colour change without a moult.



assumption of summer plumage in Pyromelana oryx, in confirmation

of the late Dr. Arthur C. Stark’s and my own published declaration

that in the genus Pyromelana all plumage which does not require

alteration in form and size for purposes of ornamentation gradually

assumes the nuptial colouring without a moult, and I pointed out

that in the example which I was describing, and which died during

the change, a considerable part of the plumage was in a transitional

condition between winter and summer colouring, in many of the

feathers the brown winter colouring, with heavy blackish shaft-

streaks being washed over with the more or less reddish orange of

the summer hue. If feathers are moulted out and replaced by new

ones of a different colour, the change must necessarily be abrupt;

and, as I have argued years ago, when describing the development

of the adult colouring in the Yellow-hilled Cardinal (‘Proc. Zook Soc.,’

1903, vol. ii. pp. 350, 351), it would require not one but a constant

succession of moults to represent all the changes through which these

tropic feathers pass.


At the end of my paper the Editor inserts the following note :

“ The example of Pyromelana oryx, referred to by Dr. Butler, is now

in the British Museum, and does not, in our opinion, or that of

others who have examined it, warrant the conclusion that the colour-

change is brought about by the absorption of fresh colour by the old

feathers. Both it and other examples, especially one collected

by Mr. Swynnerton, in Pthodesia, in November (reg. no. 1911, 5. 30.

394), show undoubted signs of moult.”


Now, nobody has yet called in question the fact stated by

Stark that “ the feathers of the lower back, rump, and flanks are

entirely changed by a moult ” ; what they, many of them, refuse to

believe is his further statement, “ the remaining plumage and bill

becoming darker, owing to a gradual absorption of colouring matter.”

(‘ The Fauna of South Africa,’ Birds, vol. i, p. 131) ; yet Stark is by

no means the only careful observer of birds in their native haunts

who has expressed his faith in colour-change without a moult.


{To he continued.)



