ii8 THE MIGRATION OF BIRDS. 



Instances of Chronic Emigration are not only as- 

 interesting, but even more numerous, and appeal 

 all the more forcibly to us, because they are either 

 actually in progress around us, or have only ceased 

 during historic time. The evidence that many 

 species of birds have quite recently extended their 

 range, or are even in the act of doing so, is above 

 the faintest suspicion of doubt, and in no smalL 

 number of cases amounts to absolute proof. The 

 Arctic Willow Wren {P Injlloscopus horealis) at one 

 time bred in North-east Siberia, and wintered in 

 Burma and the Malay Archipelago, as might 

 naturally be inferred from the locality of its- 

 summer quarters. But a slow and gradual emigra- 

 tion set in westwards across Siberia and Europe,, 

 and now this species actually visits Finmark in 

 summer, but returns along the old routes of gradual 

 dispersal to the ancient trunk iiy-lines of the far 

 East, which it follows to the accustomed winter 

 home! The Siberian Pipit [Aiithus gustavi) has- 

 emigrated gradually from the East in a precisely 

 similar manner, and now its summer range is known 

 to extend at least as far west as the Petchora Valley,, 

 in Russia, although its winter quarters are still con- 

 fined to South-eastern Asia. The Rustic Bunting 

 (Emberiza rustica) has extended its range even as 

 far west as Scandinavia in summer, but returns to 

 India and China to winter. Precisely the same 

 kind of emigration has been taking place among 

 West Palaearctic birds. The individual Willow 

 Wrens {Phylloscopus trochilus) and Sedge Warblers 



