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Gould, J., on migration of swifts; on the arrival of male snipes before the females; on the numerical proportion of the sexes in birds; on Neomorpha Grypus; on the species of Eustephanus; on the Australian musk-duck; on the relative size of the sexes in Briziura lobata and Cincloramphus cruralis; on Lobivanellus lobatus; on habits of Menura Alberti; on the rarity of song in brilliant birds; on Selasphorus platycerus; on the Bower-birds; on the ornamental plumage of the Humming-birds; on the moulting of the ptarmigan; on the display of plumage by the male Humming-birds; on the shyness of adorned male birds; on the decoration of the bowers of Bower-birds; on the decoration of their nest by Humming-birds; on variation in the genus Cynanthus; on the colour of the thighs in a male parrakeet; on Urosticte Benjamini; on the nidification of the Orioles; on obscurely-coloured birds building concealed nests; on trogons and king-fishers; on Australian parrots; on Australian pigeons; on the moulting of the ptarmigan; on the immature plumage of birds; on the Australian species of Turnix; on the young of Aithurus polytmus; on the colours of the bills of toucans; on the relative size of the sexes in the marsupials of Australia; on the colours of the Marsupials.

No doubt the males of some obscurely-coloured birds fight desperately together, but it appears that when sexual selection has been highly influential, and has given bright colours to the males of any species, it has also very often given a strong tendency to pugnacity. We shall meet with nearly analogous cases when we treat of mammals.

The reverse appears to occur seldom; for, as he believes, the more vigorous males pass over the weakly females, and are attracted by those endowed with most vitality. Nevertheless, the Bombycidae, though obscurely-coloured, are often beautiful to our eyes from their elegant and mottled shades.

By a little further acceleration in the process, the double moult would be completely lost. See Macgillivray, 'Hist. Some male birds, as before stated, become more brightly coloured in the spring, not by a vernal moult, but either by an actual change of colour in the feathers, or by their obscurely-coloured deciduary margins being shed.

The bright colours of the male must make it very conspicuous to birds of prey, and, probably in consequence, it is not nearly so bold as the obscurely-coloured females.