ORNITHOLOGICAL EXPLORATIONS. 357 



pothesis that this isolation has existed since it first began to be inhab- 

 ited by its present laud-oruisy and also that this immigration commenced 

 at no very distant period. The probable cause of this comparatively 

 late colonization, whether due to the country having undergone a glacial 

 period, or whether volcanic phenomena have anythiug to do with it, is 

 not in our line to discuss, these being questions for the geologists to 

 solve. 



That so many of the resident birds have developed into distinct forms 

 is no argument against the theory of a comparatively recent coloniza- 

 tion, since all are nearly related to forms inhabiting neighboring coun- 

 tries, and since this specialization is chiefly only an intensification of 

 the general tendency of the birds inhabiting the whole region of which 

 Kamtschatka only forms a province. If considering these facts in con- 

 nection with the nearly absolute isolation of the forms in question, no 

 assumption of a very long period seems to be needed in explanation. 



The question how these residents originally happened to populate the 

 country should, perhaps, be discussed briefly before closing these re- 

 marks. 



Looking at the absence of many generally distributed northern Cir- 

 cumpolar and Palaearctic forms of the resident ornis, for instance, Fe- 

 risoreus, Garrulus, Certhia, Begulus, Ginclus, Bonasa, «&c., one can hardly 

 escape the imjjression that those species which now reside perma- 

 nently in Kamtschatka originally came there accidentally. Like so many 

 other islands Kamtschatka probably owes its resident ornis to storms 

 having blown the first pairs over from countries across the sea. This 

 population has been- going on since it first became inhabitable, and con- 

 tinues so even to-day. That explains in a measure the different degree 

 of abundance and specialization, those forms which have only recently 

 made their appearance being less numerous and less modified. 



Saving now discussed the Kamtschatkan avifauna in its relation to 

 the surrounding countries, the conclusion seems quite justified that the 

 peninsula forms a very well circumscribed ornitho-geographical jjrov- 

 ince, remarkable not only for a number of jieculiarly modified forms, but 

 also for a surprising absence of many of the most characteristic forms 

 of the Northern Palajarctic and Oircumi^olar ornis. 



It may finally be interesting to give a condensed comparison with a 

 province of similar size and position at the opposite side of the Palaearctic - 

 continent. Great Britain is situated between nearly the same latitudes 

 as Kamtschatka, taking a somewhat similar position on the Atlantic side 



