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The Descent of Man

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dimorphic, for white and coloured individuals<br />

<strong>of</strong> the same age may be observed. <strong>The</strong> Harlequin<br />

duck (Anas histrionica, Linn.) takes three<br />

years to acquire its full plumage, though many<br />

birds breed in the second year (vol. iii. p. 614).<br />

<strong>The</strong> White-headed Eagle (Falco leucocephalus,<br />

vol. iii. p. 210) is likewise known to breed in its<br />

immature state. Some species <strong>of</strong> Oriolus (according<br />

to Mr. Blyth and Mr. Swinhoe, in 'Ibis,'<br />

July 1863, p. 68) likewise breed before they attain<br />

their full plumage.)<br />

<strong>The</strong> fact <strong>of</strong> birds breeding in their immature<br />

plumage seems opposed to the belief that<br />

sexual selection has played as important a part,<br />

as I believe it has, in giving ornamental colours,<br />

plumes, etc., to the males, and, by means <strong>of</strong><br />

equal transmission, to the females <strong>of</strong> many species.<br />

<strong>The</strong> objection would be a valid one, if the<br />

younger and less ornamented males were as<br />

successful in winning females and propagating<br />

their kind, as the older and more beautiful ma-

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