262 ISLAND LIFE part ii 



than between the cont inent of Europe or North Africa, 

 and a group of rocky islands in mid-Atlantic, situated in 

 the full course of the Gulf Stream and with an excessively 

 mild though stormy climate. We have every reason to 

 believe that special modifications would soon become 

 established in any animals completely isolated under such 

 conditions. But they are not, as a rule, thus completely 

 isolated, because, as we have seen, stragglers arrive at short 

 intervals ; and these, mixing with the residents, keep up 

 the purity of the breed. It follows, that only those species 

 which reach the Azores at very remote intervals will be 

 likely to acquire well-marked distinctive characters ; and 

 this appears to have happened with the bullfinch alone, a 

 bird which does not migrate, and is therefore less likely 

 to be blown out to sea, more especially as it inhabits woody 

 districts. A few other Azorean birds, however, exhibit 

 slight differences from their European allies. 



There is another reason for the very slight amount of 

 peculiarity presented by the fauna of the Azores as com- 

 pared with many other oceanic islands, dependent on its 

 comparatively recent origin. The islands themselves may 

 be of considerable antiquity, since a few small deposits, 

 believed to be of Miocene age, have been found on them, 

 but there can be little doubt that their present fauna, at 

 all events as concerns the birds, had its origin since the 

 date of the last glacial epoch. Even now icebergs reach 

 the latitude of the Azores but a little to the west of them ; 

 and when we consider the proofs of extensive ice-action in 

 North America and Europe, we can hardly doubt that 

 these islands were at that time surrounded with pack-ice, 

 while their own mountains, reaching 7,600 feet high in 

 Pico, would almost certainly have been covered with per- 

 petual snow and have sent down glaciers to the sea. They 

 might then have had a climate almost as bad as that now 

 endured by the Prince Edward Islands in the southern 

 hemisphere, nearly ten degrees farther from the equator, 

 where there are no land-birds whatever, although the 

 distance from Africa is not much greater than that of the 

 Azores from Europe, while the vegetation is limited to a 

 few alpine plants and mosses. This recent origin of the 



