Page:The British Warblers A History with Problems of Their Lives - 7 of 9.djvu/83

 (Sylvia cinerea) call note, Pied Wagtail (Motacilla lugubris), Blue-headed Wagtail (Motacilla flava), Yellow Bunting (Emberiza citrinella), Green Woodpecker (Gecinus viridis), Oyster-catcher (Hæmatopus osiralegus), Black-tailed Godwit (Limosa belgica), Common Tern (Sterna fluviatilis), Common Redshank (Totanus calldris), Lapwing (Vanellus vulgaris), Meadow-Pipit (Antlius pratensis), Skylark (Alauda arvensis), Redstart (Ruticilla phœnicurus), Starling (Sturnus vulgaris), and Magpie (Pica rustica). The imitations are to a large extent copies of sounds produced by the inhabitants of the surrounding district. For instance, the cries of the Black-tailed Godwit, Redshank and Oyster-Catcher are reproduced in Holland where those birds are everywhere abundant. Any cry, call note, or song is liable to be reproduced immediately, if only it is uttered sufficiently close to a male that is singing, or if it happens to be particularly loud or distinct, and as a rule no hesitation is shown by the imitator in incorporating the alien sound with its true song. So easily does the imitation flow from the throat of the bird, and so natural a sequence does it seem to be of the vocal effort, that an observer who had not just heard the sound which was copied might readily regard it as a revival of phrases previously associated. Nevertheless the majority of the imitations are due to revival. This can be proved in two ways. Firstly by the fact that a species is sometimes imitated which does not inhabit the surrounding neighbourhood, as for instance when a male in a midland county reproduces the song of Savi's Warbler, and secondly by noting the sequence of imitative strains. This latter feature requires some further consideration. The question is sometimes asked whether the sequence is always similar in the same individual. I have satisfied myself that it is not. The cries of different species are not reproduced in rotation but are interspersed throughout the song in no definite order. From time to time, whilst listening to different males. I have rapidly written down the species