THE GLACIAL RANGE CONTRACTIOX, ETC. 133 



Of the species whose lines of Emigration from the 

 British Islands extend East alone, not one, it may be 

 remarked, has succeeded in extending its breeding range 

 across our area to Scandinavia. They are all species 

 whose northern breeding range in the British Isles does 

 not reach the Shetlands, or in the few instances in which 

 it does reach that locality, the evidence distinctly shows 

 that they have only done so within recent time. It is 

 therefore more than doubtful whether any individuals of 

 these typical Eastern migrants come from continental 

 areas north or east of the Baltic, or south of Holland. 

 From how far north in Russia these eastern migrants 

 may come it is at present impossible even to conjecture. 

 That the line of Emigration, however, extended into 

 Western Asia, say as far south as Orenburg, is to some 

 extent proved by the odd individuals of thoroughly 

 eastern or Asiatic species that from time to time get 

 into this western stream of migration and abnormally 

 turn up on Heligoland, in the British Islands, and else- 

 where. It may also be remarked that iox^^ if any, of 

 these typical Eastern migrants are dominant during 

 winter in the extreme south of Europe, still less so 

 across the Mediterranean, where some of them are 

 replaced by nearly allied species or races. 



Of the species whose lines of Emigration from the 

 British Islands extend both East and North-east, it is 

 significant that in every case they are birds that have 

 reached Scandinavia by both routes, as is proved by 

 their breeding dominantly in the Shetlands, and by 

 their passing our entire eastern area on migration. It 

 is, however, worthy of remark that in many, if not in all, 

 cases the North-east migrants are the first to visit us, 



