ISLAND AVIFAUNAS 197 



complete distinction to be attained. I cannot admit 

 what Dr. Wallace asserts to be the case, viz. that in 

 the British Isles " the process of formation of peculiar 

 species has only just commenced" (^Island Life, new ed., 

 p. 408), for there is no evidence whatever to show that 

 these British endemic forms are not of very ancient 

 origin — dating, it may be, from the close of the Pleis- 

 tocene Period — to indicate that they are not struggling 

 with adverse conditions in segregating themselves ; con- 

 ditions, be it remarked, that will prevent complete 

 specific distinction so long as they continue. 



Now a few words with regard to the poorness of the 

 British avifauna in endemic species. The geographical 

 position of our islands is directly opposed to the 

 establishment of local or peculiar species. They are 

 situated too far north for many species ever to become 

 absolutely sedentary within their limits (so long as 

 climatal conditions continue the same), and they are 

 adjacent to areas where the conditions for sedentary 

 residence are even less suitable. The inevitable con- 

 sequence is that the several avifaunas are constantly 

 being mixed by the migration taking place over these 

 various districts ; and to such an extent does this pre- 

 vail, that probably not more than two or perhaps three 

 of our indigenous birds are sufficiently isolated from the 

 remainder of the species to ensure the preservation of 

 any variation that they might develop. The species 

 that are the most sedentary show the greatest amount 

 of local variation. This is specially observable in the 

 case of the Dipper, the Red Grouse, and the Partridge ; 

 and could we only isolate sufficiently the various local 

 types of these species that occur in certain areas, there 



