1920.] Birds of the Canai-y Islands. 543 



rarer than volcanoes^ any more than we should look for Sand- 

 Grouse in Pabna. Even in such islands as Tenerife and 

 Gran C^anaria the distribution o£ the two Teydean Chaffinches 

 is bounded absolutely by the limits of the pine forests, 

 which once covered a much larger extent of land than they 

 do at the present day. Marsh breeding-birds — such as the 

 Marbled Duck, the Coot, and the Moorhen — must, since the 

 ancient lake at Laguna is no more, be restricted almost 

 entirely to the Charco's of Maspalomas and Arguineguin in 

 Gran Canaria. 



Special vegetation means special food upon wiiich many 

 seed- and fruit-eating species are entirely de[)endent. The 

 two fine Canarian Pigeons live almost entirely on the seeds 

 of certain trees ; Culuinba bollei and Culumba junoni<s sub- 

 sist to such an extent on the fruit of Laurus fa'tens that 

 when the laurel was exterminated in Gran ( -anaria C. bollei, 

 wliich formerly thrived in that island, completely disappeared. 

 There is no Laurel Pigeon in Hierro, for the Laurel and 

 Til-tree are almost absent. Instances could be multiplied, 

 but that mentioned will illustrate my point. 



Reference must be made here to the remarkable distri- 

 bution of two of the Tubinares which visit the Canaries 

 to breed. Puffinus assimilis baroli is the only form of 

 the assiiiiilis-gvovi\) of Shearwaters wdiich is found in the 

 Atlantic, where it is confined to the north Atlautides from 

 the Azores to the C'anaries. The other members of the 

 gioup inhabit widely separated localities in the Pacific and 

 Indian Oceans. 



I'crhaps the most remarkable case of all is that of 

 Bulwer's Petrel. In the Atlantic it inhabits the same 

 Archipelagos as the Madeiraii Allied Shearwater, but its 

 nearest allied race inhabits the Sandwich Islands in the 

 Pacific; no intermediate subspecific races are known. 



The explanation of this discontinuous distribution must 

 be looked for in the great autiquity of the order to which 

 the Petrels and Shearwaters belong, combined with the 

 changes which have taken place in the distribution of land 



