THE GLACIAL RANGE CONTRACTION, ETC. 127 



range higher in continental Europe than they do in the 

 British Islands. In many cases the difference of northern 

 limit in the two areas is enormous ; and curiously enough 

 some of the most striking examples are to be found 

 amongst such delicate species as the Thrushes and 

 Warblers ! Our Missel Thrush and Song Thrush are 

 by no means dominant birds in Scotland, yet in Scan- 

 dinavia they range up to the Arctic Circle ; the Redstart 

 is only locally distributed in Scotland, but in summer it 

 ranges in Norway to the North Cape, the Arctic land of 

 the midnight sun ! The two species of Whitethroat are 

 decidedly rare and local north of the Border, yet in 

 Scandinavia they are regular summer visitors up to 

 lat. 64° ; whilst the Garden Warbler, local even in the 

 south of Scotland, prolongs its migrations to the North 

 Cape in Norway. The Sedge Warbler,^ too, goes as far 

 north in summer, yet does not range as high in our area 

 to breed as the Orkneys. The Tree Pipit is rare north 

 of the Clyde, yet is a regular summer visitor to the 

 extreme north of Norway, fifteen degrees of latitude 

 higher. Even the delicate fastidious Wood Lark — a typical 

 English species — ranges up to lat. 60° in Scandinavia. 

 The Swift does not breed in the Orkneys, yet does so in 

 Scandinavia in lat. 70° ; the Wryneck, unknown in Scot- 



^ The Sedge Warbler is said to be absent from the south of 

 Norway, which is strong evidence that the species entered that 

 portion of Europe from the south-east, and not by a northern 

 emigration or range expansion either up what is now west conti- 

 nental Europe, or across the British Area. From such a South- 

 eastern base an extension of range southwards or across a wide 

 water area would be necessary for the species to enter south 

 Norway — a line of emigration contrary to the law of its dispersal. 

 Very similar remarks apply to the Wood Wren, which is absent 

 from Norway altogether, yet breeds in Sweden as far north as 

 Upsala. 



