204 THE MIGRATION OF BRITISH BIRDS 



especially from the ]\Ialayand Pacific Islands. We need 

 not inquire how or whence the avifaunas of these various 

 islands have been derived ; all that concerns us is by 

 what means such a very large percentage of the species 

 has succeeded in becoming endemic. The indigenous 

 species of all these areas are sedentary. Vast numbers 

 of birds may visit these islands in winter, or pass over 

 them on migration, yet none of such birds are the direct 

 ancestors of these endemic species. The endemic avi- 

 fauna stands quite apart ; its affinities are exclusively 

 with the non-migratory species in the more or less 

 adjacent areas, or with forms that from a variety of 

 causes have ceased to visit the area occupied by the 

 peculiar form. It is said that many of these endemic 

 island species owe their origin to volcanic or seismic 

 agency, a species often being isolated into various 

 groups, as a previously compact area has been divided 

 into various portions by earthquakes or volcanic action. 

 This is true, but only under certain conditions. Japan 

 is a great centre of earth disturbance, so are various 

 parts of the Mediterranean ; but we do not find the 

 same results following upon such earth action as we 

 find in other areas, as, for instance, in the Pacific — 

 where almost every island possesses some endemic form 

 — or in the East Indian Archipelago, where the phe- 

 nomenon of peculiar species is very apparent and domi- 

 nant. If the geographical area be situated upon a 

 migration route, little specific change will result, no 

 matter how varied the physical disturbance ; if, on the 

 other hand, the disturbance takes place (even on a 

 comparatively small scale) in areas where no migration 

 occurs among the avifauna, or where species are chiefly 



