question whether the exceptions are not so numerous as seriously to
invalidate them.
There is in the first place much truth in the Duke of Argyll s remark
(10. Journal of Travel, edited by A. Murray, vol. i. 1868, p. 281.)
that a large domed nest is more conspicuous to an enemy, especially to
all tree-haunting carnivorous animals, than a smaller open nest. Nor
must we forget that with many birds which build open nests, the male
sits on the eggs and aids the female in feeding the young: this is the
case, for instance, with Pyranga aestiva (11. Audubon, Ornithological
Biography, vol. i. p. 233.), one of the most splendid birds in the
United States, the male being vermilion, and the female light
brownish-green. Now if brilliant colours had been extremely dangerous
to birds whilst sitting on their open nests, the males in these cases
would have suffered greatly. It might, however, be of such paramount
importance to the male to be brilliantly coloured, in order to beat his
rivals, that this may have more than compensated some additional
danger.
Mr. Wallace admits that with the King-crows (Dicrurus), Orioles, and
Pittidae, the females are conspicuously coloured, yet build open nests;
but he urges that the birds of the first group are highly pugnacious
and could defend themselves; that those of the second group take
extreme care in concealing their open nests, but this does not
invariably hold good (12. Jerdon, Birds of India, vol. ii. p. 108.
Gould s Handbook of the Birds of Australia, vol. i. p. 463.); and
that with the birds of the third group the females are brightly
coloured chiefly on the under surface. Besides these cases, pigeons
which are sometimes brightly, and almost always conspicuously coloured,
and which are notoriously liable to the attacks of birds of prey, offer
a serious exception to the rule, for they almost always build open and
exposed nests. In another large family, that of the humming-birds, all
the species build open nests, yet with some of the most gorgeous
species the sexes are alike; and in the majority, the females, though
less brilliant than the males, are brightly coloured. Nor can it be
maintained that all female humming-birds, which are brightly coloured,
escape detection by their tints being green, for some display on their
upper surfaces red, blue, and other colours. (13. For instance, the
female Eupetomena macroura has the head and tail dark blue with reddish
loins; the female Lampornis porphyrurus is blackish-green on the upper
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