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Yet this bird may have been but another male, to whom the next unseen notes that I heard were, perhaps, due. Always I bless those birds whose sexes are plainly distinguishable from each other.

What was very noticeable in these nightingales—and the remark applies to others that I have closely listened to—was that, even when not singing against each other, they made little noises in their throats, and these, when distinctly heard, resolved themselves into a deep, guttural sound, which, though far from unpleasing, could hardly be called anything but a croak. This sound, as I have noticed, is very frequently uttered. It often commences the song, or is even intermingled with, though it can scarcely be said to belong to, it. It does not, in this case, diminish the beauty of the melody; yet, did it stand alone, the nightingale would be merely a somewhat musical croaker. Probably this is what it once has been, the low, croaking note representing the original utterance of the bird, on which the song, by successive variations, and choice of them on the part of the female, has been founded. Just as in the dull plumage of female pheasants and other birds, the males of which are splendidly adorned, or in both the sexes of some species belonging to the same families, we see the early state of their common, plain progenitors, so, in song-birds, the uninspired, workaday voice of call-note or twitter—the spoken language, as one may call it—probably represents the humble roots from which the various trees of song, with all their diversified branchings, and fluttering,