Birds, on the other hand, show extreme joy, both in motion and appearance; and it is the sight of this evident disposition for enjoyment on their part that gladdens us as we watch them. And this appearance must not be regarded as unreal and deceptive. They sing to express the happiness they feel, and the happier they are, the more vigorously do they sing. And if, as it is said, they sing louder and more sweetly when in love than at other times, it is equally certain that other pleasures besides love incite them to sing. For we may notice they warble more on a quiet and peaceful day, than when the day is dark and uncertain. And in stormy weather, or when frightened, they are silent; but the storm passed, they reappear, singing and frolicking with one another. Again, they sing in the morning when they awake; being partly incited to this by a feeling of joy for the new day, and partly by the pleasure generally felt by every animal when refreshed and restored by sleep. They also delight in gay foliage, rich valleys, pure and sparkling water, and beautiful country.... It is said that birds' voices are softer and sweeter, and their songs more refined, with us than among wild and uncivilised people. This being so, it would seem that birds are subject to the influence of the civilisation with which they associate. Whether or not this be true, it is a remarkable instance of the providence of nature that they should have capacity for flight, as well as the gift of song, so that their voices might from a lofty situation reach a greater number of auditors. It is also providential that the air, which is the natural element of sound, should be inhabited by vocal and musical creatures.