Page:The Zoologist, 4th series, vol 6 (1902).djvu/490

420 are absent, as compared with a dry climate, are those where the high notes are introduced. I do not mean that the song is not as beautiful; for I have listened to Wrens in Donegal singing quietly, whose notes, certainly not many, for fulness and richness of tone, were equal to the finest notes of the Blackcap. The same phenomenon applies to the song of the Whitethroat.

Different species appear to be subject to this climatic influence in different degrees of intensity. For instance, the variation to be found in the song of the Buntings is very small; I found great difficulty in detecting any variation at all in the song of the Yellow Bunting. The same thing applies to the song of the Tits, the Coal Tit having the least variation. On the other hand, the variation in the song of the Warblers—Wren and Blackbird—is most marked, that in the Whitethroat and Sedge-Warbler being very striking.

These facts seem to point to the variation being proportionate to the development that has taken place in the song of a given species, and I think it can be readily understood that the most highly developed, and, therefore, most sensitive, musical instrument would most probably be subject to this climatic influence in the greatest degree.

There is another phase of bird song which might be confused with this dialectical change, namely, the song of the immature males. The males of probably all species do not get their full song for some years, in the same way that they do not really get their full plumage—I think it very probable that the two correspond; but this song of the immature males differs rather in the direction of fulness and richness of tone than in any actual change of the song, and is very easily distinguished from this dialectical change.

My observations in a damp climate have always been made either in March or July. I think that a close study of the migratory species on their arrival in this country would, by settling certain difficulties, throw some light on the whole question. Is this change to be found immediately on their arrival, or does it increase as the season advances? Is it permanent, or only temporary? The difficulty, as I mentioned previously, is that it is impossible to compare notes with anyone making similar observations, and it is also obvious that it is