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The Descent of Man

The Descent of Man

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females in the groups, in which as a general<br />

rule the sexes resemble each other, all relate to<br />

species which build domed or concealed nests.<br />

But similar gradations may likewise be observed<br />

in groups in which the sexes as a general<br />

rule resemble each other, but which build open<br />

nests.<br />

As I have before instanced the Australian parrots,<br />

so I may here instance, without giving<br />

any details, the Australian pigeons. (27. Gould's<br />

'Handbook to the Birds <strong>of</strong> Australia,' vol. ii. pp.<br />

109-149.) It deserves especial notice that in all<br />

these cases the slight differences in plumage<br />

between the sexes are <strong>of</strong> the same general nature<br />

as the occasionally greater differences. A<br />

good illustration <strong>of</strong> this fact has already been<br />

afforded by those kingfishers in which either<br />

the tail alone or the whole upper surface <strong>of</strong> the<br />

plumage differs in the same manner in the two<br />

sexes. Similar cases may be observed with parrots<br />

and pigeons. <strong>The</strong> differences in colour

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