THE BIRDS OF SABK. 419 



I may here say that by the word " call notes," I refer to everys 

 note belonging to a species thai is not actually the song, although 

 they are not by any means in a number of cases call notes in a 

 literal sense. The climate in Sark and in the west of Donegal 

 are much the same. The rainfall of both is above the average ; 

 both are subject to bad sea fogs from the Atlantic, and are there- 

 fore very damp. On the other hand, the climate of Worcester- 

 shire is peculiarly dry, the rainfall being much below the average. 

 Looking, then, at this fact, that a lower pitch corresponds with 

 a damp climate, and a higher pitch with a dry climate, I think I 

 am justified in coming to the conclusion that clmate exercises a 

 certain influence on the pitch of the notes and songs of certain 

 species. 



The dialectical variation is more difficult to explain, and my 

 observations up to the present time are, comparatively speaking, 

 so small, that perhaps I am hardly justified in forming any 

 definite conclusion. The great difficulty in any researches on 

 this point appears to be this — that all observations must be 

 carried out by the same person ; and to compare, except on 

 general lines, with anyone making similar investigations is almost 

 a practical impossibility. At first I was inclined to think 

 that the song was more highly developed, or the reverse, in 

 certain districts than in others, and that as a result of there 

 being a scarcity of one sex or the other, sexual selection might 

 exercise considerable influence in this direction ; but on finding, 

 after making further investigation, that migratory species were 

 subject to this change, any theory with regard to sexual selection 

 acting in this manner becomes impossible, and we must, there- 

 fore, look to some other cause for an explanation. I found that 

 the song of the Whitethroat on the shores of Loch Lomond 

 differed very much from anything I had previously or since 

 heard. Again I noticed the same change in the call note of the 

 Chaffinch in Inverness ; and I now feel convinced that there are 

 as many dialects amongst certain species as there are amongst 

 human beings. I am inclined to think that the explanation will 

 again be found in climatic influence, and that these dialects are 

 in a great measure due to the lowering of the pitch. Take, for 

 instance, the song of the Wren in a damp climate. When 

 listened to very carefully, it will be be found that the parts that 



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