86 THE MIGRATION OF BRITISH BIRDS 



confined to the southern and central counties of Eng- 

 land, the Marsh Warbler to one or two of the southern 

 counties only, the Red-necked Phalarope chiefly to the 

 Shetlands, Orkneys, and Outer Hebrides. We shall also 

 fmd that even with resident birds that have ennigrated 

 from the south-east, extremely few are widely distributed 

 or dominant species in our area {couf. pp. 88 — 91). 



It will thus be seen that of the G'^^ species that 

 may be fairly classed as regular summer visitors to 

 the British Islands (or some part of them), no less 

 than 60 species may be said, almost with absolute 

 certainty, to have reached them by way of the Iberian 

 Peninsula and France, and but three species can be 

 reasonably presumed, judging from their present geo- 

 graphical limits, to have reached them by no other 

 way than from the south-east, most probably via the 

 valleys of the Danube and the Rhine. Could an)-- 

 thing testify more eloquently or more significantl)- 

 to the source whence the British avifauna has been 

 derived ? 



Whilst dealing with species obviously of south-eastern 

 origin, it may be advisable here to treat with another 

 group of birds resident in or wanderers on nomadic or 

 abnormal flight to the British Islands — birds whose 

 range base during the Glacial hLpoch extended to 

 Refuge Area III., or which have gradually extended 

 their range to Western Europe from Asia after the 

 Ice Age had passed away. 



