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The Descent of Man

The Descent of Man

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WHEN THE ADULT MALE RESEMBLES<br />

THE ADULT FEMALE, THE YOUNG OF<br />

BOTH SEXES HAVE A PECULIAR FIRST<br />

PLUMAGE OF THEIR OWN.<br />

In this class the sexes when adult resemble each<br />

other, and differ from the young. This occurs<br />

with many birds <strong>of</strong> many kinds. <strong>The</strong> male robin<br />

can hardly be distinguished from the female,<br />

but the young are widely different, with their<br />

mottled dusky-olive and brown plumage. <strong>The</strong><br />

male and female <strong>of</strong> the splendid scarlet ibis are<br />

alike, whilst the young are brown; and the scarlet<br />

colour, though common to both sexes, is<br />

apparently a sexual character, for it is not well<br />

developed in either sex under confinement; and<br />

a loss <strong>of</strong> colour <strong>of</strong>ten occurs with brilliant males<br />

when they are confined. With many species <strong>of</strong><br />

herons the young differ greatly from the adults;<br />

and the summer plumage <strong>of</strong> the latter, though<br />

common to both sexes, clearly has a nuptial<br />

character. Young swans are slate-coloured,<br />

whilst the mature birds are pure white; but it

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