Page:The British Warblers A History with Problems of Their Lives - 7 of 9.djvu/15

 districts than is sometimes imagined to be the case, but, according to my experience, is gradually extending its range in a northerly direction. It is now eleven years since the bird first came under my notice on the northern boundary of the county of Worcester. A solitary individual then appeared in June, but after remaining a few days vanished. For some years following there was no further sign of the species, but it has now reappeared and. I hope, finally established itself in the district. There are places in both Worcestershire and Gloucestershire where it can by no means be described as uncommon, since it is an annual visitor in numbers which seem to be increasing. The Severn Valley appears to be especially favoured, but in saying this we must bear in mind how limited our knowledge of its distribution may really be, and how rare the bird was supposed to be until efforts were made to discover it. Many districts in which it has already been found nestingare eminently suited to its habits, and it is difficult to believe that in such places it is a casual visitor only. But just because it is an easy matter to assume that it has been overlooked, we must in the future scrutinise all the facts relating to its distribution the more closely, for otherwise we should be neglecting the bird with the most striking and highly developed vocal powers of all our birds. The gradual extension of its breeding range has a meaning in relation to the struggle for existence which we can scarcely afford to ignore. On migration it has been recorded from St. Kilda and Fair Isle. Concerning its distribution in the Iberian Peninsula little appears to be known beyond the fact that it is said to have bred towards the south, though the evidence is far from satisfactory. In France it is generally distributed, except in the western provinces. In all suitable localities in Belgium, the Netherlands and Germany it is common, but in Denmark scarce: it has occurred near Gothenburg. To the northern provinces of Italy, especially Piedmont, it is a common summer visitor, and though less common than the Reed Warbler in Switzerland, it is nevertheless generally distributed in all suitable localities, such as the