Page:The British Warblers A History with Problems of Their Lives - 4 of 9.djvu/69

 on the shores of Loch Lomond, and both of these again differ in this respect from the same bird in the Island of Texel. The Wren in Worcestershire has a different song from that of the Wren in Donegal and Sark, and the Willow Warblers that grace the banks of the Danube can be readily distinguished by their notes from those in this country.

The subject is one of some difficulty, and is further complicated by our having to rely solely on so delicate an instrument as the human ear. But it should be our first aim, no matter what the problem with which we are confronted in Nature, to attempt to find some one characteristic which extends to every case, or at any rate obtains in a large number of them, and upon which we can base our further investigations. This. I believe, we can do in the present instance, always, however, bearing in mind the imperfections to which the human ear is liable.

If we take the Midland counties as our starting-point, and from thence journey in a westerly or south-westerly direction, we shall find that as we approach the coast of Wales, or of the south-western counties, the tendency is for the pitch of the song of many species to become gradually lower. But passing over these slight differences, we will still continue west, across the Irish Sea and across Ireland, until we finally reach the West of Donegal, where, having selected the song of one of the more common species, we will proceed to make comparisons with that of the same species in any one of the counties from which we started. Well, to my ear there is no doubt about the difference; the Blackbird pipes in a lower key, the cheery song of the Wren is more mellow, and even the familiar call note of the Chaffinch has gained some subtle difference. Leaving this, however, we will return to our starting-point, and journey in a southerly direction until we reach the Channel Islands. Here we shall find the same conditions prevailing as in Donegal—namely, a uniform lowering of the pitch; and yet again comparisons made on the west coast, or even on parts of the north-east coast of Scotland, will