him. But can this be so confidently said of sexual selection? Seeing in
how many ways the tail-feathers of humming-birds differ, why should not
the four central feathers have varied in this one species alone, so as
to have acquired white tips? The variations may have been gradual, or
somewhat abrupt as in the case recently given of the humming-birds near
Bogota, in which certain individuals alone have the central
tail-feathers tipped with beautiful green. In the female of the
Urosticte I noticed extremely minute or rudimental white tips to the
two outer of the four central black tail-feathers; so that here we have
an indication of change of some kind in the plumage of this species. If
we grant the possibility of the central tail-feathers of the male
varying in whiteness, there is nothing strange in such variations
having been sexually selected. The white tips, together with the small
white ear-tufts, certainly add, as the Duke of Argyll admits, to the
beauty of the male; and whiteness is apparently appreciated by other
birds, as may be inferred from such cases as the snow-white male of the
Bell-bird. The statement made by Sir R. Heron should not be forgotten,
namely, that his peahens, when debarred from access to the pied
peacock, would not unite with any other male, and during that season
produced no offspring. Nor is it strange that variations in the
tail-feathers of the Urosticte should have been specially selected for
the sake of ornament, for the next succeeding genus in the family takes
its name of Metallura from the splendour of these feathers. We have,
moreover, good evidence that humming-birds take especial pains in
displaying their tail-feathers; Mr. Belt (54. The Naturalist in
Nicaragua, 1874, p. 112.), after describing the beauty of the
Florisuga mellivora, says, I have seen the female sitting on a branch,
and two males displaying their charms in front of her. One would shoot
up like a rocket, then suddenly expanding the snow-white tail, like an
inverted parachute, slowly descend in front of her, turning round
gradually to shew off back and front...The expanded white tail covered
more space than all the rest of the bird, and was evidently the grand
feature in the performance. Whilst one male was descending, the other
would shoot up and come slowly down expanded. The entertainment would
end in a fight between the two performers; but whether the most
beautiful or the most pugnacious was the accepted suitor, I know not.
Mr. Gould, after describing the peculiar plumage of the Urosticte,
adds, that ornament and variety is the sole object, I have myself but
little doubt. (55. Introduction to the Trochilidae, 1861, p. 110.)
If this be admitted, we can perceive that the males which during former
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