174 THE MIGRATION OF BRITISH BIRDS 



by way of the Orkneys and Shetlands. The Hedge 

 Accentor {Accentor modular is) is unquestionably increas- 

 ing its range northwards in Sutherlandshire and Caith- 

 ness ; and it may be remarked is another precisely 

 similar instance to the preceding one of the Goldcrest — 

 a species that has emigrated east from England across 

 the North Sea Area before it extended its northern 

 range at all dominantly into Scotland. The Nuthatch 

 {Siita ccssid) is one of our most local birds, yet there is 

 evidence to suggest that it is steadily advancing north- 

 west into Wales, where comparatively recently it was 

 very rare. The Tree Pipit (Antfnis trivialis) has, it is 

 said, only been detected breeding in Sutherlandshire 

 within the past twenty years. 



The Greenfinch {Fringilla cJiloris) must also be re- 

 garded as another species that has extended its northern 

 emigration in our islands within recent years. It has 

 become much more dominant in the northern and wilder 

 portions of our islands, as the cultivation of trees has 

 increased, even reaching the Orkneys, where it now 

 breeds sparingly. It is interesting to remark that this 

 bird, like the Goldcrest, is only known as a Coasting 

 Migrant over, or winter visitor to, the Shetlands ; and 

 this fact seems to me to suggest that the favourable 

 conditions which assisted the emigration of this species 

 across our area via the Orkneys and the Shetlands to 

 Scandinavia (where it ranges up to lat. 65""), have lapsed 

 ■ — a variation in the climate of these islands involving 

 the destruction of forest growth seems to have occurred 

 (and there is some evidence that such actually took 

 place), and by extermination driven the breeding range 

 in our islands southwards for a time (although the 



