ORNITHOLOGICAL EXPLORATIONS. 339 



cidental visitors enter the fauna! lists, which, strictly, should be kept 

 aside as foreign elements. The list of Kamtschatkan birds, however, 

 appears to embrace but very few forms which do not occur regularly in 

 one or the other part of the peninsula. There are apparently four 

 causes of this peculiarity of the list, the first being that comparatively 

 few irregular visitors find their way to it on account of its isolated po- 

 sition ; second, that no general migration route between countries to 

 the north and south seems to pass through the region ; third, that the 

 extreme districts which adjoin neighboring regions are entirely unex- 

 plored ; and fourth, that, since Steller's time, no ornithologist who was 

 a hunter himself has resided in the country for more than a few months. 

 In thickly settled countries, where all the common birds are known, 

 every unusual and rare visitor is soon found out and reported (cf. 165 

 occasional visitors, against 211 regular inhabitants of the British ornis); 

 but not so in Kamtschatka, where the 175 names may practically be re- 

 garded as representing the number of species actually belonging to the 

 fauna. 



But not all of these throw particular light upon the relationship of 

 the ornis, except in a general way. Many forms are so generally dis- 

 tributed over large areas and show so little variation that they are less 

 fit to illustrate those features of the geographical distribution, which 

 are of special interest. Others again are so closely limited in their dis- 

 tribution by the character of the localities they inhabit as to give 

 very unreliable material for comparison. This is eminently true of 

 many water birds, a great many of which in their distribution char- 

 acterize the faunal areas of the ocean and not those of the land. They 

 will therefore have to be considered separately. It will be seen that 

 m this case, at least, the habits have a considerable influence upon 

 .the geographical distribution j the old-fashioned system, chiefly based 

 upon teleological characters, may therefore, in this connection, offer 

 some advantages over those aiming at morphological characters for 

 their basis. For this purpose we shall partly apply a division of the 

 birds into " swimmers," " waders," « game birds," " birds of prey " " pi- 

 carians," and "perchers," in the old sense of these appellations, a 

 course which, in some measure, will facilitate a comparison of some of 

 the results here arrived at with those of earlier writers. 



The old observation that the proportional number of species of water 

 birds (swimmers and waders) increases toward the Arctic region is 

 confirmed by the following table, which shows that of all the birds oc 



