is. This may be illustrated by the practice followed by some
bird-fanciers, who pull out a few feathers from the breast of nestling
bullfinches, and from the head or neck of young gold-pheasants, in
order to ascertain their sex; for in the males, these feathers are
immediately replaced by coloured ones. (36. Mr. Blyth, in
Charlesworth s Magazine of Natural History, vol. i. 1837, p. 300. Mr.
Bartlett has informed me in regard to gold pheasants.) The actual
duration of life is known in but few birds, so that we can hardly judge
by this standard. And, with reference to the period at which the power
of reproduction is gained, it is a remarkable fact that various birds
occasionally breed whilst retaining their immature plumage. (37. I have
noticed the following cases in Audubon s Ornith. Biography. The
redstart of America (Muscapica ruticilla, vol. i. p. 203). The Ibis
tantalus takes four years to come to full maturity, but sometimes
breeds in the second year (vol. iii. p. 133). The Grus americanus takes
the same time, but breeds before acquiring its full plumage (vol. iii.
p. 211). The adults of Ardea caerulea are blue, and the young white;
and white, mottled, and mature blue birds may all be seen breeding
together (vol. iv. p. 58): but Mr. Blyth informs me that certain herons
apparently are dimorphic, for white and coloured individuals of the
same age may be observed. The Harlequin duck (Anas histrionica, Linn.)
takes three years to acquire its full plumage, though many birds breed
in the second year (vol. iii. p. 614). The White-headed Eagle (Falco
leucocephalus, vol. iii. p. 210) is likewise known to breed in its
immature state. Some species of Oriolus (according to Mr. Blyth and Mr.
Swinhoe, in Ibis, July 1863, p. 68) likewise breed before they attain
their full plumage.)
The fact of birds breeding in their immature plumage seems opposed to
the belief that sexual selection has played as important a part, as I
believe it has, in giving ornamental colours, plumes, etc., to the
males, and, by means of equal transmission, to the females of many
species. The objection would be a valid one, if the younger and less
ornamented males were as successful in winning females and propagating
their kind, as the older and more beautiful males. But we have no
reason to suppose that this is the case. Audubon speaks of the breeding
of the immature males of Ibis tantalus as a rare event, as does Mr.
Swinhoe, in regard to the immature males of Oriolus. (38. See footnote
37 above.) If the young of any species in their immature plumage were
more successful in winning partners than the adults, the adult plumage
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