212



Dr. Arthur G. Butler,



their species :* the colouring generally is more uniform and less

brilliant; thus if we take as an example the distinctions noted

in the British Museum Catalogue of the Parrots we find Chrysotis

augusta, young, “ Has the occiput and hind part of the head

green; also the posterior parts of the cheeks are tinged with green.”

C. mercenaria, “ No red wing-speculum.” C. cestiva, “ Has no yellow

on the head and no blue band on the forehead, the whole head

being green.” C. ochrocephala, “Yellow colour of the crown more

restricted or entirely wanting, and less red on the bend of the wing,

where sometimes it is entirely absent ” (probably immature and

nestling plumages). G. auropalliata , “ Wants the yellow collar on

the hind neck.” C. agilis, “ Has no red on the primary-coverts,

which are green, and no bluish tinge on the pileurn.” I have

omitted several descriptions of young said to have a red wing-

speculum, because I strongly doubt this being a nestling character;

I think the examples should have been described as “ immature,”

being in a transitional stage from the nestling to the adult plumage.


It is only what one would expect in birds like the Parrots,

the prevailing colour of which is green, that blue or yellow varying

through orange to scarlet should be developed in their plumage :

lutinos (answering to albinos in other groups) are not particularly

rare among them, and are probably the result of constitutional

delicacy. In the Budgerigar we also get a blue form, which 1 regard

as practically a melanistic type due to unusual constitutional vigour.

The late Mr. Joseph Abrahams assured me that the yellow form

resulted from close inbreeding, so that the blue form may, perhaps,

be produced by a directly opposite treatment.


By the way, if, as Pycraf't tells us in his ‘ Story of Bird-Life,’

p. 25, “ Blue colouring matter has never yet been found in birds.

The blue colour of certain feathers is due solely to structural

characters,” how is it that the elimination of yellow from green

feathers leaves them blue and the elimination of blue leaves them



* After writing the above, it occurred to me to wonder whether this idea had

also struck Darwin; so little escaped that marvellous man that it seemed

impossible that he could have overlooked it: sure enough (‘ Descent of

Man,’ second edition, p.742), I found — “We may admit as probable that

the young have retained an ancient state of plumage.”



