300 SIBERIA IN EUROPE. CHAP. xxm. 



to extend beyond the valley of the Petchora, as far as the 

 White Sea, viz. : 



Siberian Lesser-spotted Wood- 

 pecker. 



Little Bunting. 

 Arctic Willow- Warbler. 



Marsh-Tit (eastern form). 

 Terek Sandpiper. 

 Siberian Herring-Gull* 



One bird only appears to be so restricted in its geographical 

 range as to be found only in the valleys of the Petchora, the 

 Obb, and the Yenesay, viz. : 



Siberian Chiff-chaff. 



Of the fourteen birds included in the last four lists, only four 

 or five of them have their principal breeding-grounds within 

 the Arctic Circle, and these all belong to genera which are 

 represented in the Nearctic region, with the exception of the 

 Arctic willow-warbler, which has been obtained in Alaska. 



The final conclusion to which we must therefore arrive, 

 from a study of the geographical distribution of the birds 

 found in the valley of the Petchora, is that a circumpolar 

 region ought to be recognised : that so far as the Polar 

 regions are concerned the division into Nearctic and PalaB- 

 arctic is a purely arbitrary one. 



The migration of birds is a subject which interests all 

 naturalists, and is a very attractive one to a great number of 

 persons who do not pretend to any scientific knowledge of 

 ornithology. The dates and order of arrival of migratory 

 birds present so many points of interest that, for the sake 

 of comparison, the following list has been made of all those 

 birds which we had reason to believe to be migratory in the 



