BIRDS OF THE GALAPAGOS. 49 



■which afford numerous resting-places, it would not seem difBcult 

 to account for the occurrence of land-birds at the remotest dis- 

 tances from the mainland, even without having recourse to the 

 accessory transporting agency of prevalent winds and storms. But 

 even with this favourable condition added, it would appear that 

 most land-birds are not disposed to undertake of their own free 

 will extended oceanic journeys, as is proved by the avi-fauna of 

 many of the oceanic islands. Thus, while, as we have already 

 seen, nearly all the representatives of the bird-fauna of the Azores, 

 situated more than one thousand miles from the mainland, are 

 identical with forms inhabiting either Europe or Northern Africa, 

 indicating that the islands were peopled in comparatively recent 

 times from those continents, in the Galapagos, situated only six 

 hundred miles off the west coast of the continent of South Amer- 

 ica, we meet with an entirely dififerent state of things as regards 

 the bird-fauna. Of about thirty species of indigenous land-birds, 

 apparently only one, the common rice-bird (Dolichonyx oryzivorus), 

 which ranges from Canada to Paraguay, is absolutely identical with 

 a form found outside the limits of the island group. In addition 

 to this a species of owl (Asio Galapagoensis) is considered by some 

 authors to be but a mere variety of the cosmopolitan Asio brachy- 

 otuSj, or short-eared owl, which is distributed from China to Ire- 

 land, and from Greenland to Patagonia."' We have here, there- 

 fore, positive evidence that migrant stragglers from the South 

 American continent are at the best of but very rare occurrence, 

 and, on the other hand, visitors from the islands to the mainland 

 appear to be equally rare. But since, from the resemblance which 

 the fauna as a whole presents to that of the mainland, it is practi- 

 cally proved that the same was at one time derived by migration 

 from the continental areas — the islands being of volcanic origin — 

 it is manifest that this migration must have taken place at a period 

 sufficiently remote to have permitted the differences separating the 

 two faunas to have been brought about. On the other hand, the 

 absolute identity of the rice-bird with the similar form from the 

 continent, proves, as has been pointed out by Wallace, that the 

 island breed has been kept unaltered only through repeated or fre- 



Isles. The easterly dispersion Is attributed to causes identical with those 

 which have been assigned in explanation of the phenomenon by Professor 

 Boird. 



