280 
DARWINISM 
CHAP. 
exposed to the attack of the whole colony ; whereas a hawk or 
falcon could carry off a sitting-bird or the young at a swoop, 
and entirely avoid attack. Moreover, each kind of covered 
nest is doubtless directed against the attacks of the most 
dangerous enemies of the species, the purse-like nests, often a 
yard long, suspended from the extremity of thin twigs, being 
useful against the attacks of snakes, which, if they attempted 
to enter them, would be easily made to lose their hold and 
fall to the ground. Such birds as jays, crows, magpies, 
hawks, and other birds of prey, have also been urged as an 
exception; but these are all aggressive birds, able to protect 
themselves, and thus do not need any special protection for 
their females during nidification. Some birds which build in 
covered nests are comparatively dull coloured, like many of 
the weaver birds, but in others the colours are more showy, 
and in all the sexes are alike ; so that none of these are in any 
way opposed to the rule. The golden orioles have, however, 
been adduced as a decided exception, since the females are 
showy and build in an open nest. But even here the females, 
are less brilliant than the males, and are sometimes greenish 
or olivaceous on the upper surface; while they very carefully 
conceal their nests among dense foliage, and the male is 
sufficiently watchful and pugnacious to drive oft' most in¬ 
truders. 
On the other hand, how remarkable it is that the only small 
and brightly coloured birds of our own country in which the 
male and female are alike—the tits and starlings—either 
build in holes or construct covered nests ; while the beautiful 
hangnests (Icteridae) of South America, which always build 
covered or purse-shaped nests, are equally showy in both 
sexes, in striking contrast with the chatterers and tanagers of 
the same country, whose females arc invariably less conspicuous 
than the males. On a rough estimate, there are about 1200 
species of birds in the class of showy males and females, with 
concealed nidification; Avhile there are probably, from an 
equally rough estimate, about the same number in the con¬ 
trasted class of showy males and dull females, with open 
nests. This will leave the great bulk of known birds in the 
classes of those which are more or less protectively coloured 
in both sexes ; or which, from their organisation and habits, do 
