192 THE MIGRATION OF BRITISH BIRDS 



peculiar species where the avifaunas, both on the islands 

 and in the surrounding areas, are sedentary. Let us 

 deal with each of these island groups in turn, and sec 

 how the facts they present may be explained by geo- 

 graphical position, and the absence or presence of any 

 dominant line of Migration. 



First we will consider the British Isles. We have 

 already dwelt at some length on the emigration of 

 species to this area, and on the comparison of its avi- 

 fauna with that of adjacent areas. For the purposes of 

 the present inquiry it will only be necessary to confine 

 our attention to the few endemic species or races that 

 dwell in these islands, to explain their presence in that 

 area, and to show wh}- the British avifauna is so poor in 

 peculiar forms. At the close of Chapter IV. (p. 158J 

 we gave a list of these British endemics. But one of the 

 five species is absolutely distinct, the remaining four 

 being races or insular forms, only subspecifically distinct 

 from continental species. The one exception is so 

 utterly unique in character that I cannot resist the 

 opportunity of inquiring somewhat full}- into its origin. 

 The Red Grouse is absolutely peculiar to the British 

 Archipelago, the one solitary endemic bird entitled to 

 specific rank. How did it come there .' The nearest 

 ally of the Red Grouse, in fact its continental represen- 

 tative, is the Willow Grouse {Lagopiis a/bus). There 

 can be no reasonable doubt that before the Glacial 

 Epoch the Willow Grouse was the only and dominant 

 species in West Europe, including what is now the 

 British Area. Exterminated in the north by the chang- 

 ing climate, by the snow-fields and the glaciers, the 

 remainder of the species continued to dwell in South 



