THE BLUE-THROATED WARBLER IN SCOTLAND. 4538 
Society’s meeting in Edinburgh, on the 21st February, 1877. At 
that time I said, “‘ What we have for a long time considered as 
accidental—purely accidental—occurrences of continental species 
ought, in many instances, I think, rather to be held as indications 
of extension towards the north of their breeding limits on the 
Continent.” Since then, as I will show, I have somewhat modified 
this opinion, as I think, besides such occurrences being partly 
due to northern extension of the breeding range, they are also 
due to prevalence of easterly and south-easterly winds and gales 
blowing the migrants more to the northward than in other 
circumstances they would be borne. 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* the occurrence of another south-eastern 
species,—viz., the Desert Wheatear,—which will also be found 
alluded to in the same Report. At that time also the prevailing 
winds were EK. 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 
prevailing 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, all lie in a line, 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 comparison, 
only adding that, as far as I can at present judge from numerous 
statistics at command, I believe the waves of migration of certain 
species take certain and fixed linés, 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 
extraordimary seasons and with prevalence of wind from unusual 
* Proc. Royal Phys. Soc. Edinb. 1880-81, vol. vi. p. 64. 
