50 THE MIGRATION OF BRITISH BIRDS 



Range Base or Refuge Area III. : This area in- 

 cluded all the now submerged land in the Mediterranean 

 east of say E. long. 20", and Europe south of about lat. 

 47°, and east of the Adriatic. At this period probably 

 the whole of what is now the /Egean Sea was dry land, 

 the coast-line extending along the western shores of 

 Greece and continuing unbroken or nearly so along 

 Crete to Cyprus, and thence down the coast of Syria, 

 which possibly extended seawards much further than 

 is now the case. South of the Caucasus, Georgia, Ar- 

 menia, Asia Minor, Syria, Northern and Western Arabia, 

 Persia, and Afghanistan, must be included as part of this 

 refuge area ; as also must the entire continent of Africa 

 as it then existed, its northern coast-line reaching from 

 the Atlantic along the southern limits of the ancient 

 Saharan sea. The chief physical changes in this area have 

 been on the one hand the vast series of submergences 

 which have produced the Grecian Archipelago, and 

 isolated Crete and Cyprus ; and on the other hand, the 

 retreat of the ocean from the Sahara with the accom- 

 panying increase of the land surface of continental 

 Africa in the north. So far as concerns British species 

 this area is the least important of the three. We have 

 the most positive evidence to show that the range base 

 of purely West European birds did not extend to that 

 region during the Ice Age to any important extent. It 

 is, however, absolutely necessary for us to recognize such 

 an area, for it formed the range base of certain species 

 which, in ultimately extending their area to the British 

 Islands during Post-Glacial time, present some very 

 curious instances of dispersal, and forcibly illustrate the 

 eccentricities which sometimes characterize the migration 



