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The Descent of Man

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certain herons. By such steps as these, the vernal<br />

moult might be rendered more and more<br />

complete, until a perfect double moult was acquired.<br />

Some <strong>of</strong> the birds <strong>of</strong> paradise retain<br />

their nuptial feathers throughout the year, and<br />

thus have only a single moult; others cast them<br />

directly after the breeding-season, and thus<br />

have a double moult; and others again cast<br />

them at this season during the first year, but<br />

not afterwards; so that these latter species are<br />

intermediate in their manner <strong>of</strong> moulting. <strong>The</strong>re<br />

is also a great difference with many birds in<br />

the length <strong>of</strong> time during which the two annual<br />

plumages are retained; so that the one might<br />

come to be retained for the whole year, and the<br />

other completely lost. Thus in the spring Machetes<br />

pugnax retains his ruff for barely two<br />

months. In Natal the male widow-bird (Chera<br />

progne) acquires his fine plumage and long<br />

tail-feathers in December or January, and loses<br />

them in March; so that they are retained only<br />

for about three months. Most species, which

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