PDF - Wallace Online

NATURAL SELECTIONIn the extensive families of the warblers (Sylviadae),thrushes (Turdidae), flycatchers (Muscicapidse), and shrikes(Laniadee), a considerable proportion of the species are beautifullymarked with gay and conspicuous tints, but in everycase the females are less gay, and are most frequently of thevery plainest and least conspicuous hues. Now, throughoutthe whole of these families the nest is open, and I am not aware ofa single instance in which any one of these birds builds adomed nest, or places it in a hole of a tree, or under ground, or inany place where it is effectually concealed.In considering the question we are now investigating, it isnot necessary to take into account the larger and more powerfulbirds, because they seldom depend much on concealmentto secure their safety. In the raptorial birds bright coloursare as a rule absent ;and their structure and habits are suchas not to require any special protection for the female. Thelarger waders are sometimes very brightly coloured in bothsexes ;but they are probably little subject to the attacks ofenemies, since the scarlet ibis, the most conspicuous of birds,exist in immense quantities in South America. In game birdsand water-fowl, however, the females are often very plainlycoloured, when the males are adorned with brilliant hues ;and the abnormal family of the Megapodidee offers us the interestingfact of an identity in the colours of the sexes (whichin Megacephalon and Talegalla are somewhat conspicuous), inconjunction with the habit of not sitting on the eggsWhat the Fads Teach usat all.Taking the whole body of evidence here brought forward,embracing as it does almost every group of bright-colouredbirds, it will, I think, be admitted that the relation betweenthe two series of facts in the colouring and nidification ofbirds has been sufficiently established. There are, it is true,a few apparent and some real exceptions, which I shall considerpresently ;but they are too few and unimportant toweigh much against the mass of evidence on the other side,and may for the present be neglected. Let us then considerwhat we are to do with this unexpected set of correspondencesbetween groups of phenomena which, at first sight, appear sodisconnected. Do they fall in with any other groups of