Page:The British Warblers A History with Problems of Their Lives - 5 of 9.djvu/79

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Redshank (Totanus calidris). The alarm-note of the Blackbird is often well imitated, and the call-note of a Pied Wagtail (Motacilla lugubris) fluttering out of the reeds, or of a Kingfisher (Alcedo ispida) flying above, is sometimes well reproduced. The cries of the different Terns, where a colony happens to be breeding in proximity to a reed bed, will often be incorporated with the song, and I have also heard perfect imitations of a call-note of the Blue Tit, Chaffinch, Icterine Warbler (Hypolais icterina), Sedge Warbler and Willow Warbler. But in judging of the power of imitation it is necessary to bear in mind the possibility of some of the notes, which are apparently perfect copies of those of another species, being in reality a natural part of the vocal powers of the imitator. For instance. I remember hearing a Blackbird introduce into its song throughout the breeding season the cry of the Curlew (Numenius arquata) in a very perfect manner. Possibly it may have heard a Curlew, but in the district in which it was singing it is scarcely probable that it had done so, for that species, with the exception of an individual occasionally passing over at a considerable height, is unknown there. At the time I did not believe that the imitation, perfect as it was, was genuine, but rather part of the true song slightly altered, and later I was confirmed in this opinion upon finding that only a slight alteration is required to produce such a result. There are some imitations which we need not hesitate to declare to be imitations pure and simple. When a bird interrupts its true song, and for a few moments introduces that of another, differing in combination and possibly in tone, we can point to it with some certainty as an imitation. On the other hand there may be a perfect resemblance in the song of two species which we can be equally certain has no foundation in the imitative faculty. It is only with difficulty that the true song of the Icterine Warbler can be distinguished from that of the Marsh Warbler, yet no one could say that one is an imitation, although it may be a perfect representation, of the other. Both songs