CHAP, xri THE AZORES 251 



Madeira it must have travelled quite as far as from 

 Portugal to the islands. Mr. Godman also shot a single 

 specimen of the wheatear in Flores after a strong gale of 

 wind, and as no one on the island knew the bird, it was 

 almost certainly a recent arrival. Subsequently a few 

 were found breeding in the old crater of Corvo, a small 

 adjacent island ; and as the species is not found in any 

 other island of the group, we may infer that this bird is a 

 recent immigrant in process of establishing itself. 



Another fact which is almost conclusive in favour of the 

 bird-population having arrived as stragglers is, that they 

 are most abundant in the islands nearest to Europe and 

 Africa. The Azores consist of three divisions — an eastern, 

 consisting of two islands, St. Michael's and St. Mary's ; a 

 central of five, Terceira, Graciosa, St. George's, Pico, and 

 Fayal ; and a western of two, Flores and Corvo. Now had 

 the whole group once been united to the continent, or even 

 formed parts of one extensive Atlantic island, we should 

 certainly expect the central group, which is more compact 

 and has a much larger area than all the rest, to have the 

 greatest number and variety of birds. But the fact that 

 birds are most numerous in the eastern group, and diminish 

 as we go westward, is entirely opposed to this theory, while 

 it is strictly in accordance with the view that they are all 

 stragglers from Europe, Africa, or the other Atlantic 

 islands. Omitting oceanic wanderers, and including all 

 birds which have probably arrived involuntarily, the 

 numbers are found to be forty species in the eastern 

 group, thirty-six in the central, and twenty-nine in the 

 western. 



To account for the presence of one peculiar species — 

 the bullfinch (which, however, does not differ from the 

 common European bullfinch more than do some of the 

 varieties of North American birds from their type-species) 

 is not difficult ; the wonder rather being that there are 

 not more peculiar forms. In our third chapter we have 

 seen how great is the amount of individual variation in 

 birds, and how readily local varieties become established 

 wherever the physical conditions are sufficiently distinct. 

 Now we can hardly have a greater difference of conditions 



