We are still inclined to believe, however, that there is a larger proportion of musical birds in the temperate than in the torrid zone, because in the former region there are more of those species that build low and live among the grass and shrubbery, and it is well known that the singing-birds are mostly of the latter description. In warm climates the vegetation consists chiefly of trees and tall vines, forming together an umbrageous canopy overhead, with but a scanty undergrowth. In temperate latitudes the shrubbery predominates, especially in the most northerly parts. Moreover, the grasses that furnish by their seeds a great proportion of the food of the smaller birds are almost entirely wanting in the torrid zone. The birds that live in trees are remarkable for their brilliant plumage; those that live upon the ground and in the shrubbery are plainly dressed. This is a provision of Nature for their protection, as the ground-birds must have a predominance of tints that resemble the general hues of the surface of the earth. I do not know a single brightly-plumed bird that nestles upon the ground, unless the bobolink may be considered an exception. They are almost invariably colored like sparrows. The birds that inhabit the trees, on the other hand, need less of this protection, though the females are commonly of an olive or greenish yellow, which harmonizes with the general hue of the foliage, and screens them from observation, while sitting upon the nest. The male, on the contrary, who seldom sits upon the nest, requires a plumage that will render him conspicuous to the female and to the young, after they have left their nest. It is remarkable, that Nature, in all cases in which she has created a difference in the plumage of the male and female, has used the hues of their plumage only for the protection of the mother and the young, for whose advantage she has dressed the male parent in colors that must somewhat endanger his own safety.