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Show 280 DARWINISM CHAP. exposed to the attack of the whole colony; whereas a hawk or falcon could carry off a sittinrr-bird or tho young at a swoop, and entirely avoid attack. Moreover, each kind of covered nest is doubtless directed acrainst the attacks of the most danO"crous enemies of the spe~ies, the purse-like nests, often a yard loner suspended from the extremity of thin twigs, being useful ag~inst the attacks of snakes, which, if the;r attempted to enter them would he easily made to lose thmr hold and fall to the ~round. Such birds as jays, crows, magpies, hawks, and other birds of prey, have also been urged as an exception; but these arc all agrrrcssivc bird~, able to protect themselves, and thus do not need any spccml protectiOn for their females during 11idification. Some birds which buj}d in covered nests are comparatively dull coloured, like many of the weaver birds, but in others the colours arc more showy, and in all the sexes arc alike; so that none of these arc in any way opposed to the rule. The golden orioles have, however, been adduced as a decided exception, since the females arc showy and build in an open nest. But even here the females are less brilliant than the males, and arc sometimes grccni. h 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 off most intruders. On the other hand, how remarkable it is that the only srnn 11 and brightly coloured birds of our own country in which tho male and female are alike-the tits and starlings-either build in holes or construct covered nests; while the beautiful hangncsts (Icterid::.e) of South America, which always bnild covered or purse-shaped nests, are cquaUy 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 arc about 1200 species of birds in the class of showy males and females, with concealed nidification; while there are probably, from an equally rough estimate, about the same number in the contrasted 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 orsanisation and habits, do x COLOURS AND ORNAMENTS CIT ARACTERl~TIC OF SEX 281 not require special protective coloration, such as many of the birds of prey, the larger waders, and the oceanic birds. There are a few very curious cases in which the female bird is actually more brilliant than the male, and which yet have open nests. Such arc the dottcrcl (Eudromias morincllus), several species of phalarope, an Australian creeper (Climactcris crythropus), and a. few others; but in every one of these cases the relation of the sexes in regard to nidifica.tion is reversed, the male performing the duties of incubation, while the female is the stronger and more pugnacious. This curious case, therefore, quite accords with the general law of coloration.1 Sexual Coloun of other Vertebmtes. We may consider a few of the ca. cs of sexual colouring of other classes of vertebrates, as given hy Mr. Darwin. ln fishes, though the sexes arc usually alike, there are several species in which the males arc more brightly coloured, and ha.ve more elongated fins, spines, or other a-ppendages, and in some few cases the colours arc decidedly different. The males often fight together, and arc altogether more vivacious and excitable than the females during the breeding season; and with this we may connect a greater intcn. ity of coloration. In frogs and toads the colours arc usually a.like, or a little more intense in the males, and the same may be said of most snakes. It is in lizards that we first meet with considerable sexual differences, many of the species having gular pouches, frills, dorsal crests, or horns, either confined to the males, or more developed in them tha.n in the females, and these ornaments are often brightly coloured. In most cases, however, the tints of lizards are protective, the male being usually a little more intense in coloration; and. the difference in extreme cases may be partly due to the need of protection for the female, which, when laden with eggs, must be less active and less able to escape from enemies than the male, and may, therefore, have retained more protective colours, as so many insects and birds have certainly donc. 2 In mammalia there is often a somewhat greater intensity ~ Seebobm's History of B1itish Bi1·ds, vol. ii., introducLiou, p. xiii, ~ for details see Darwin's Descent of Afan, chap. xii, |