i6o THE MIGRATION OF BRITISH BIRDS 



condition of the British Area during this cold era, and 

 attempted an outline of the probable resident avifauna 

 of that and adjoining areas during this period. We 

 traced out the two other Range Bases or Refuge Areas 

 during the close of the Glacial Epoch of most of the 

 species that now compose the avifauna of West 

 Europe, by the aid of their allied southern and parent 

 races or representative species left stranded in Iberia, 

 North-west Africa, the Canary Islands, Malta, etc. 

 We have also sought to demonstrate not only that 

 the range of a very large percentage of our resident 

 species is continuous from our area down to Iberia, 

 North-west Africa, and the Canary Islands ; but also 

 that a by no means inconsiderable number of species 

 resident in our islands or met with in them through- 

 out the year resort to that region (Refuge Area II.) 

 in winter, as very conclusive evidence of the source 

 from which our avifauna was derived. Similar con- 

 firmation of this fact has also been shown to exist 

 among the species that are only known as winter 

 visitors to our area, many of them extending their 

 range at that season to varying limits as far south as 

 the Canaries. We have also shown that almost all our 

 Summer Visitors seek winter quarters in this Refuge 

 Area (II.). Some of these species go much further south 

 in the east than in the west ; some of them breed as well 

 as winter in North-west Africa (a most convincing proof 

 that that was an area of dispersal or base from which 

 their emigrations northwards commenced), yet only pass 

 North-east Africa on migration — two apparent anom- 

 alies for which I think a satisfactory reason has been 

 given, Wc have also dealt with the two small groups of 



