BIRDS. 



265 



in the glens of the central hills and " dryfields " lands of Stirlingshire, 

 and in the Vale of Menteith, and beyond as far as the roots of the 

 G-rampians about Callander, though I am not aware that many have 

 as yet succeeded in penetrating beyond the Pass of Leny in that 

 direction. I do know, however, that they have penetrated well up 

 the Forth Valley as far as Aberfoyle, and have appeared in cliffs 

 between Aberfoyle and Loch Katrine in the vicinity of the new road 

 which leads across from Aberfoyle to the Trossachs. I will not venture 

 to attempt to decide whether these last have found their way by that 

 route, or by any other, more directly through Tay from the east. 



Perhaps I may be permitted here to refer once more to my 

 previous communication, already quoted, and ask those of my readers 

 who are sufficiently interested in "distribution and dispersal of 

 species " to read hack. Everything points to an ever-increasing 

 pressure from the south towards the north, at least so far at present 

 as the Great Divide (or approaching to it). When inland localities 

 become flushed, then there is abundant evidence that the Stock-Dove 

 can — and does — accommodate itself to the friendly companionship 

 of the rabbit of the sandhills ; and so the ground in time is all taken 

 up. As for any migrational instinct — the word will slip in urongly 

 sometimes — or migratory necessity, that will come to be developed 

 later when the necessity arises, and all grounds become congested. 

 Birds do not become migratory until they are forced to become so ! 



Before quitting the article upon this species, perhaps I may be 

 allowed also to ask my readers to refer back to what has been 

 already written of it in our Moray volumes, and in all places north 

 of the Grampians. The dispersal there I believe to have been 

 induced from a different centre, and to be due to congestion at 

 some Continental centre or centres. The same impetus to increase 

 which had congested the breeding quarters of England had, in all 

 probability, also acted in certain zones of the greater nesting haunts 

 on the Continent ; and the same impulses had acted and made those 

 of European, i.e. Continental origin seek wider fields, and find an 

 escape from a condition of things which was fast becoming intoler- 

 able. I have wondered, at times, if all the Lemmings which swarm 

 periodically in Scandinavia were able to reach our shores, what vole- 

 plague would compare with their invasions 1 How else can we 

 explain that phenomenal invasion of the Tartar host of Syrrhaptes 1 



If we do not grant that there was a different centre for the in- 

 vaders found north of the Grampians, then how can that strange 

 hiatus, or blank, or slow filling-in of the coast counties of Forfar and 



