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Show 2-1:2 ISLAND LTFK [rA.tt'I' 1!. Africa except three-the Atlantic chaffinch and the canary which inhabit .Madeira and the Canary Islands, and t~e ~zorean bullfinch which is peculiar to the islands we are considenng. 0Tigin' of the Azorean Birdjauna.-The questions ~ve have now before us are-how did these eighteen species of birds first reach the Azores, and how are we to explain the pres~nce 0~ a single peculiar species while all the rest are identical with European birds 1 In order to answer them, let us first see what strarro'lers now actually vi· s·i t t h e A zores f ro m the nearest con-tinebnbts . The four speC.i es gi• ven m• Mr . Go d m an's list are the kestrel the oriole the snow-bunting, and the hoopoe; but he also tells us that there are certainly others, and adds: "Scarcely a storm occurs in spring or autumn without bringing one or more species foreign to the islands; and I have frequently been told that swallows, larks, grebes, and other species not referr~~ to here, are not uncommonly seen at those seasons of the yea.r. We have, therefore, every reason to believe that ~be birds which are now residents oricrinated as stragglers, whiCh occasionally found a haven in the~e remote islands when driven out to sea by storms. Some of them, no doubt, sti~l _ofte~ arrive from the continent, but these cannot easily be distmgmshed rt.s new arrivals among those which are residents. Many facts mentioned by Mr. Godman show that this is the ~ase. A barn-o.wl, much exhausted, flew on boa,rd a whaling-ship when 500 m1les S. W. of the Azores; and even if it had come from Madeira it must have travelled quite as far as from Portugal to the islands. Mr. Godman also shot a single specimen of the w heatear 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 birdpopulation having arrived as stragglers is, that they are most abundant in the islands nearest to Europe and Africa. The A.r.ores consist of three divisions-an eastern, consisting of two islands, St. Michael's and St. Mary's; a central of fiye, Terceira, f:l!Al'. Xll.] TilE AZORES. 243 Graciosa, St. George's, Pico, and Fayal; and a western of two, Flores and Corvo. Now had the whole group once been united to tho 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 wnnderers, and including all birds which have probably arrived involuntarily, tho 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 tho 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 individunJ 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 than between the continent of Europe or North Africa, ancl a group of rocky islands in mid-Atlantic, situated in the full course of the Gulf Stream and with an excessiYely 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, Fitragglers 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 Europerm 81lics. R 2 |