92 THE MIGRATION OF BRITISH BIRDS 



— including the British Islands — by way of Iberia to 

 North-west Africa to winter ; but it seems very probable 

 that the ancient Emigration of the ancestors of these 

 individuals was originally from cast to west along the 

 Mediterranean basin, and thence north up West Europe, 

 inasmuch as the IMigration of their descendants at the 

 present time does not extend far down the African con- 

 tinent (probably not beyond the limits of Refuge Area 

 II., as these species are unknown in or only irregular 

 stragglers to the Canary Islands) in the west, but the 

 Migrations of the descendants of eastern individuals 

 extend down that continent on its eastern portions even 

 to the Cape. Moreover, the birds that winter in the west 

 are {q.v4, and often irregular in appearance ; the great 

 bulk of the species wintering in south-eastern areas. 

 It must always remain a moot point whether, in the 

 course of their Post-Glacial emigration or extension 

 northward of breeding area with the change of climate, 

 by this route, any or all of these five species bred in the 

 British Area when that region was of an Arctic or sub- 

 Arctic character : probably they did so very sparingly. 

 I may also remark ere leaving the subject that there are, 

 of course, vast numbers of individuals of other species 

 that breed or winter with us which pass our islands only 

 on passage to breed further north or winter further 

 south, but their movements do not materially affect the 

 question we have been discussing. The significance of 

 the above facts in relation to the past geographical 

 conditions of Refuge Area II and of continental Africa 

 in glacial ages cannot be too strongly impressed upon 

 the reader. 



We now come to deal with those species of which 



