138



C or re spondenee.



successful, the hybrid would be most interesting; as it is, I strongly advise you not

to risk it. Sell the young if you can get a good offer for them.


Arthur G. Butler.



MORE ABOUT FEATHER-PATTERNS.


Dear Dr. Renshaw, —The photograph of an Eagle which you propose to use

as an illustration to my paper has suggested another point to me. As you observe

in your letter, the feathers on the breast have lost the central shaft stripe, while

those lower down still retain it; which seems to indicate distinctly that the breast-

markings were developed first.


Now, in the Turdidce , the young in their nestling plumage all have throat

and breast more or less spotted ; that is to say, the shaft-streaks persist ; but later

in life many of the smaller forms, as, for instance, our Robin, Nightingale, and

many of the Warblers, have lost this character ; whereas others have retained it only

on the flanks, and in the case of the Barred Warbler the later development of a

crescentic border to the feathers has been reached ; whilst on the coverts, wings,

and rump shaft-streaks have been modified, either so as to darken a great portion

of the feather or to form additional crescentic bars.


It seems probable that the habits of the different species will explain why

certain of these Thrush-like birds have developed markings of this character in

their adult plumage, when others have lost them ; thus the Barred Warbler, being

a skulking bird, frequenting tangled undergrowth in thickets and plantations, would

be less conspicuous in its barred markings than if more uniformly coloured.


Then, again, if the modification of shaft-streaks commenced with the throat

and breast-feathers one can understand why that portion of a bird’s plumage is

so frequently occupied by a dark or uniform belt of colour.


I hope other bird-students with younger and better brains will follow up this

subject : it seems to me to be worth coirsidering.


Yours very sincerely,


January 17 th, 1918. A. G. Butler.



THE EVOLUTION OF FEATHER-PATTERNS: CHANGE OF COLOUR

WITHOUT A MOULT.


Dear Sir,—I was much interested in reading the letter by Dr. Butler, in

which he refers to the change of colour which may occur in the feathers of certain

birds without a moult.


I have frequently noticed a remarkable deepening in the pink shade of

Roseate Cockatoos’ breasts when the birds came into breeding condition in the

early summer, at a time when no feathers were dropped.


I have also noticed that the crimson head and bib of a cock Yellow-mantled

Parrakeet (and presumably therefore of an ordinary Rosella) lose their brilliance and

turn to a duller bricltish shade quite suddenly when the moult begins in July,

although there has been no perceptible fading of the plumage during the preceding

nine months. Some naturalists have asserted most positively that the repigmenta¬

tion of feathers is quite impossible, and they have denied its occurrence even in the

Touracos, where the phenomenon was at one time considered an established fact.


My own experience with Parrots has, however, converted me to Dr. Butler’s



