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The Descent of Man

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('Ornithological Biography,' vol. iii. p. 416; vol.<br />

iv. p. 58) seems rather pleased at the thought<br />

that this remarkable change <strong>of</strong> plumage will<br />

greatly "disconcert the systematists."), should<br />

for any special purpose have been rendered<br />

pure white and thus made conspicuous to their<br />

enemies; or that the adults <strong>of</strong> one <strong>of</strong> these two<br />

species should have been specially rendered<br />

white during the winter in a country which is<br />

never covered with snow. On the other hand<br />

we have good reason to believe that whiteness<br />

has been gained by many birds as a sexual ornament.<br />

We may therefore conclude that some<br />

early progenitor <strong>of</strong> the Ardea asha and the<br />

Buphus acquired a white plumage for nuptial<br />

purposes, and transmitted this colour to their<br />

young; so that the young and the old became<br />

white like certain existing egrets; and that the<br />

whiteness was afterwards retained by the<br />

young, whilst it was exchanged by the adults<br />

for more strongly-pronounced tints. But if we<br />

could look still further back to the still earlier

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