ROUTES OF MIGRATION 221 



land extension southwards was much greater than it now 

 is. They are hardy northern species, be it remarked, the 

 Wheatear, " Swallows," and Whimbrel for instance, all 

 birds that have extended their breeding range to the 

 Arctic regions. The greater difficulties of such a route at 

 the present time may possibly have reduced the number 

 of individuals very considerably, and we can almost pre- 

 dict a future time when all migration b\' that route ma\' 

 cease. If this should Jiappcn, the Wheatear tvill cease 

 to breed in the extreme south-iuest of Ireland. Second, 

 that the St. Georges Channel land connection with Ire- 

 land continued to endure for some time after the land 

 at the extreme south of Ireland had disappeared. At 

 this time too we may be tolerably certain that much of 

 the Bristol Channel was then dry land. These facts are 

 still reflected in the great and almost only Migration 

 Route to Ireland at the present day across St. Georges 

 Channel. It marks the point of entrance into Ireland of 

 most of its avian summer visitors. Wide water areas 

 were already formed in the north of the Irish Sea, and 

 submergence was rapidl}' spreading south down that 

 sea — checking all emigration from Central and North 

 Wales to Ireland, even of sedentary species, as the few 

 last Summer Migrants succeeded in extending their 

 breeding range to the Irish Area. Complete severance 

 of Ireland from England must have taken place before 

 the island received its due share of these summer 

 visitors, the last land connections in the south across 

 St. Georges Channel disappearing and checking all 

 emigration in that direction. Migration, as we know, 

 would still continue across the slowly widening sea, 

 for once the habit of visiting Ireland was acquired, 



