might have been made a little clearer. Incidentally, you have done me a
good service by reminding me of the rudimentary spurs on the legs of the
partridge, for I am now writing on what I have called sexual selection. I
believe that I am not mistaken in thinking that you have attended much to
birds in confinement, as well as to insects. If you could call to mind any
facts bearing on this subject, with birds, insects, or any animals--such as
the selection by a female of any particular male--or conversely of a
particular female by a male, or on the rivalry between males, or on the
allurement of the females by the males, or any such facts, I should be most
grateful for the information, if you would have the kindness to communicate
it.

P.S.--I may give as instance of [this] class of facts, that Barrow asserts
that a male Emberiza (?) at the Cape has immensely long tail-feathers
during the breeding season (433/3. Barrow describes the long tail feathers
of Emberiza longicauda as enduring "but the season of love." "An Account
of Travels into the Interior of Southern Africa": London, 1801, Volume I.,
page 244.); and that if these are cut off, he has no chance of getting a
wife. I have always felt an intense wish to make analogous trials, but
have never had an opportunity, and it is not likely that you or any one
would be willing to try so troublesome an experiment. Colouring or
staining the fine red breast of a bullfinch with some innocuous matter into
a dingy tint would be an analogous case, and then putting him and ordinary
males with a female. A friend promised, but failed, to try a converse
experiment with white pigeons--viz., to stain their tails and wings with
magenta or other colours, and then observe what effect such a prodigious
alteration would have on their courtship. (433/4. See Letter 428.) It
would be a fairer trial to cut off the eyes of the tail-feathers of male
peacocks; but who would sacrifice the beauty of their bird for a whole
season to please a mere naturalist?