BRITISH WARBLERS
trembling, and further in the reflexes that are commonly awakened in the face of an enemy, such as inflation, erection of hair or feathers, lifting the voice, &c. These are obviously the material from which Nature has derived the peculiar arts of courtship in all their variety, and these arts as we have seen are then extended to occasions which have no sexual meaning." But surely the restless fluttering, running about, skipping, trembling and so forth are the peculiar arts of courtship; at least, I am aware of scarcely any sexual behaviour that could not justly be included under one of these headings.
The detailed life-history of the Marsh Warbler, which now follows, entails a repetition of certain features of behaviour to which allusion has already been made, and if the foregoing discussion fails in its first purpose to make clear the necessity for such comparisons as we shall presently institute, it will, I hope, serve to show the complexity and difficulty of the subject, and how much remains to be explained. Owing to its peculiarly close relationship to the Reed Warbler, few birds have been of greater interest to me than the Marsh Warbler, and I find it difficult to analyse its habits and instincts, or institute comparisons between its behaviour and that of the Reed Warbler without being constantly awakened to the fact that some lesson is to be learnt from its life. In the following account the different phases of its life-history will therefore be compared, wherever possible, with those which correspond to them in the life of the Reed Warbler.
The latest of all our summer migrants to arrive at its breeding haunts, it is said to reach Oxfordshire during the last few days of May or, more usually, the first few days of June, and this agrees with my own experience of the bird in Worcestershire, where I have observed it in the Severn Valley. In that district May 30th is the usual date of arrival, but in other parts of the country it has been known to arrive some few days earlier. In Gloucestershire the average date for fresh
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