PDF - Wallace Online

v COLOURS OF ANIMALS 879is, by the supposition that colour and ornament are strictlycorrelated with health, vigour, and general fitness to survive.We have shown that there is reason to believe that this isthe case, and if so, conscious sexual selection becomes asunnecessary as it would certainly be ineffective.Greater Brilliancy of some Female BirdsThere is one other very curious case of sexual colouringamong birds that, namely, in which the female is decidedlybrighter or more strongly marked than the male, as in thefighting quails (Turnix), painted snipe (Ehynchsea), twospecies of phalarope (Phalaropus), and the common cassowary(Casuarius galeatus). In all these cases it is known that themales take charge of and incubate the eggs, while the femalesare almost always larger and more pugnacious.In my "Theory of Birds' Nests" (see p. 132) I imputedthis difference of colour to the greater need for protection bythe male bird while incubating, to which Mr. Darwin hasobjected that the difference is not sufficient, and is not alwaysso distributed as to be most effective for this purpose and he;believes that it is due to reversed sexual selection that is, tothe female taking the usual rdle of the male, and being chosenfor her brighter tints. We have already seen reason forrejecting this latter theory in every case ;and I also admitthat Mr. Darwin's criticism is sound, and 'that my theory ofprotection is, in this case, only partially, if at all, applicable.But the theory now advanced, of intensity of colour beingdue to general vital energy, is quite applicable ;and the factthat the superiority of the female in this respect is quiteexceptional, and is therefore probably not in any case of veryancient date, will account for the difference of colour thusproduced being always very slight.Colour-development as illustrated by Humming-birdsOf the mode of action of the general principles of colourdevelopmentamong animals, we have an excellent example inthe humming-birds. Of all birds these are at once thesmallest, the most active, and the fullest of vital energy.When poised in the air their wings are invisible owing tothe rapidity of their motion, and when startled they dart