BLACKCAP
parison with those produced by any other known species; it is, in fact, difficult to conceive of more beautiful notes being uttered. This development, which, is very remarkable, must, in the light of this theory, have arisen from the greater sensitiveness shown on the part of the females for the vocal powers than for the colours of the males, and I do not think that anyone will question this. We ought, therefore, to find that during the courtship the males would utilise their power of song to the best of their ability, but such is not the case. As considerable significance is attached to this point, let me repeat the facts which I have mentioned earlier when describing the courtship. Until the females arrive the males usually sing their true song, but occasionally, especially when excited, imitate other species. Upon the arrival of the females a change takes place, and excitement is at its highest point, with the result that the true song is so far forgotten that, especially during that part of the courtship when the male is close to the female, high-pitched squealing notes, together with imitations, are almost solely produced, and often for a considerable time without a pause. Now let us see how the males behave under the influence of a different kind of excitement. Remove a young one from the nest, when old enough to recognise and reply to its parents, and notice the effect produced. The male approaches within a few yards of you, twists and turns on the branches, or flutters and flaps along the ground, uttering short snatches of its song identically the same as when courting, but more often squealing and imitating other species. Here, then, we have a species which performs, not only during the period of courtship, but also at other periods of excitement in its life, a remarkable series of both bodily and, if I may use the term, vocal antics. We cannot disregard these facts. If the song has really been developed owing to the females showing a greater preference for the males with the more highly developed vocal powers, is it not a little curious that, during the courtship, the true song should be so far forgotten
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