64 THE MIGRATION OF BRITISH BIRDS 



less northerly ; the Arctic area of distribution more 

 and more contracted, until the glaciers and the snow- 

 fields had killed or reduced the range of all living 

 things as low in West Europe as say the 53rd parallel 

 of latitude. England, say from Yorkshire southwards. 

 Northern France, Belgium, Holland, and parts of North- 

 western Germany, eventually became to all intents and 

 purposes the Arctic regions of Western Europe, with 

 a scanty resident avifauna, and a flora in which Arctic 

 willows and mosses, dwarf birches, lichens, and saxifrages 

 were perhaps the most characteristic features. 



So far as birds are concerned, and to them, of course, 

 our inquiry is exclusively limited, I am compelled to 

 reject the hypothesis that any temperate species sur- 

 vived the Ice Age as residents in the south of England. 

 I do so because I cannot trace a single species fairly 

 classed as temperate whose winter range to-day in 

 Western Europe reaches no further south than the 

 British Area, or say the northern portion of Range Base 

 or Refuge Area I. It will be interesting to sketch, if 

 possible, the resident avifauna of this district during 

 those far-off ages, when the greater part of England 

 was reduced to an Arctic waste. Then, as now, the few 

 resident birds of the Arctic regions were all Nomadic 

 Migrants — those restless wanderers of the avian world, 

 with no regular seasons of passage, that linger in their 

 accustomed haunts so long as they can obtain food, 

 and that travel no further than to districts where their 

 wants can be supplied. What we now class as Nomadic 

 Migrants were species whose southern range base just 

 escaped the glacial invasion ; they are species that 

 survived on the very margin of the ice-sheets and 



