The Scottish Naturalist. 205 



But on this point see the Report on Migration of Birds in 

 1880. 



Again, near Alloa, at a locality not far removed from Kin- 

 cardine on-Forth, where I shot the Black Redstart, Mr J. J. 

 Dalgleish has recorded 1 the occurrence of another south- 

 eastern species — viz., the Desert Wheat-ear — which will also be 

 found alluded to in the same report. At that time also the 

 prevailing winds were E. and S.E. 



Now again occurs another Central and South European species 

 (C. Wolfi) at the Isle of May, in the Firth of Forth, during pre- 

 vailing and strong S.E. winds, which species has not before been 

 recorded from Scotland. 



"What I want specially to point out here is, that the localities 

 of Alloa and the narrow part of the Firth of Forth, and the Isle 

 of May and the shores of the Firth, aH Me in a li?ie, or nearly 

 so, running from E. to W. ; and I only desire further to remark 

 that Alloa and that part of the country appears to be visited by 

 many other rarities, such as the Waxwing and Great Grey Shrike, 

 and a line of distribution of the occurrences of the Great Grey 

 Shrike runs also broadly across Stirlingshire, the narrowest part 

 of Scotland. I indicate these facts for further study and com- 

 parison, only adding that, as far as I can at present judge from 

 numerous statistics at command, I believe the waves of migra- 

 tion of certain species take certain and fixed lines, according to 

 influence of weather and winds ; or, in other words, that certain 

 Continental species are known to turn up at certain localities in 

 Britain with greater regularity and precision than at others — and 

 that, in extraordinary seasons, and with prevalence of wind from 

 unusual quarters, a corresponding change will take place in the 

 distribution of so-called " accidental occurrences " of Continental 

 species in Britain \ and further, that this will be aided to a con- 

 siderable extent by the northern range of such species on the 

 Continent during the breeding season in exceptionally fine 

 summers, or by the natural extension of the breeding haunts of 

 many species. 



One more point I would like to bring forward in support of 

 what I still consider theory, but which to me seems strongly 

 supported already by known facts. In ' The Field' of May 7th 

 1 88 1, were recorded occurrences of the Pied Fly-catcher in 

 Sutherland and Rosshire ; and about the same date other occur- 

 rences were recorded from various parts of the east coast of 



1 Proc. Royal Phys. Soc. Edin., 1SS0-S1, vol. vi. p. 64. 



