MIGRATION. 161 



sive in some cases than in others, that is, there 

 is a greater distance between the summer and 

 winter abodes of certain species than of other 

 species, which at the same time migrate regu- 

 larly. For example, the gannet, which breeds 

 in flocks on the Bass Kock, on St. Kilda, on 

 the Isle of Ailsa, on the Skelig Isles, etc., 

 spends the winter in the Bay of Biscay and in 

 the Mediterranean, feeding upon the anchovy 

 and sardine. The shearwater, {Puffinus An- 

 glorum,) which breeds abundantly in the Ork- 

 neys, arriving in February or March, visits in 

 winter the coasts of Spain and the Mediterra- 

 nean. The guillemot and razor-bill, which breed 

 on the Needles (Isle of Wight) in great numbers, 

 also resort to the same winter-quarters. 



Our island, then, favourably situated, receives 

 an autumnal influx of birds from the north — 

 wild fowl, woodcocks, snow-buntings, redpoles, 

 etc., which pass the cold season with us, and 

 which in spring retire northwards, giving place 

 to our summer guests. The latter, inasmuch 

 as they breed with us and not in their winter 

 asylum, may be regarded as truly indigenous; 

 while the former, which make our island a con- 

 venient retreat, but breed in the Arctic Regions, 

 cannot be considered as truly indigenous, 

 though they occupy a place in the list of 

 British birds. Of these, however, some few do 

 breed in the northern districts of our island, and 

 are thus borderers : — the red pole, (Linaria 

 minor,) and the siskin, (Carduelis spinus,) are 

 examoles in point. 



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