154 



THE MIGRATION OF BRITISH BIRDS 



line of Migration in autumn is more southerly than 

 westerly, and whose breeding grounds in some cases are 

 for the most part below the parallels of Irish latitude, 

 and in others whose centre of dispersal was from the 

 south-east. 



These facts prove undoubtedly that the common and 

 dominant species that exclusively winter in Ireland and 

 in other portions of the British Islands, or that pass 

 such areas on migration, are strictly boreal forms, most 

 of them from the high north or north-east ; the few that 

 reach us from the east are mostly rare and irregular, 

 and confine their visits principally to the eastern side of 

 our islands. Of course I need scarcely state that I do 

 not include our normal east to west migrants {conf. table, 

 p. 132) in these remarks. The proportions of the Irish 

 avifauna to that of England, Wales, and Scotland may 

 be thus briefly summarized. 



CLASSIFICATION. 



Summer migrants, 63. 

 Resident species, 115. 

 \Vinter visitors or coast- 

 ing migrants : 

 64, less 6 better classed 



as abnormal migrants ; 



total 58. 



BREEDING IN ENGLAND 

 AND SCOTLAND. 



115. 



Wintering in or passing 

 over England and Scot- 

 land : 

 58. 



BREEDING IN IRELAND. 



Wintering in or passing 



over Ireland : 

 57, less 2 abnormals ; 

 total 55. 



The significance of this proportion is apparent when 

 we study it in relation to the following facts. It may 

 be stated as an axiom, that as species begin to e.xtend 

 their breeding or summer range northwards they still 

 continue to return to winter in the area which they 

 formerly occupied as residents, until such time as that 

 extended summer area may be dwelt in permanently 



