GEOGRAPHICAL DISTRIBUTION ^^2, 



Perhaps thei'e is nothing very surprising in this, when we con- 

 sider the narrowness of the channel which here divides America 

 from Asia, and furthermore the fact that the water of Bering's 

 Strait is shallow suggests a still closer connexion in bygone times 

 of the two continents. The Aleutian Islands, though they look 

 like a series of stepping-stones from one to the other, do not seem 

 to furnish a route of communication, for Mr. Dall {Froc. Californ. 

 Acad. Sc. 14 March 1874) calls special attention to the fact that 

 no intrusion of Asiatic forms occurs towards the western end of the 

 chain, while observing that its Avifa^^na is reinforced beyond 

 Ounalaska by several Arctic species not possessed by the more 

 eastern islands. The other islands belonging to the Nearctic Sub- 

 region, the Prybilof in the Northern Pacific, and the Bermudas 

 nearly in the middle of the Northern Atlantic Ocean, do not need 

 any particular remark here. Greenland may be regarded as coming 

 almost into the same category, and though there, as might be 

 expected, the influence of the Old World is strong, that of the New 

 World just prevails, since of the 45 genera to which belong the 

 feathered denizens of the fringe of habitable soil on its western 

 coast (which is all that is oft'ered by that land of desolation) 

 none is especially characteristic of the former, while one, ZonotricJiia, 

 is peculiar to the latter, and a similar result follows from an investi- 

 gation of the species — a bare majority being Nearctic.^ 



It has been already stated that more than one -third of the 

 genera of Nearctic birds are common also to the Paloearctic Sub- 

 region. If we take the number of Nearctic species at 700, which 

 is perhaps an exaggeration, and that of Palsearctic at 850, we find 

 that, exclusive of stragglers, there are about 120 common to the 

 two areas. Nearly 20 more are properly Palsearctic, but occa- 

 sionally occur in Amei'ica, and about 50 are Nearctic, which from 

 time to time stray to Europe or Asia.^ This, however, is by no 

 means the only point of resemblance. Of many genera, the so- 

 called species found in the New World are represented in the Old 

 by forms so like them that often none but an expert can distinguish 

 them, and of such representative " species " about 80 might be 

 enumerated. 



this the writer fully believes them to be, more than one-half the Avifauna of 

 these portions of the two continents would be the same. 



^ Any one at all curious in these questions should consult Prof. Palmen's 

 tables at the end of his contribution to the ornithology of the Siberian coast, 

 printed in the fifth volume of the Scientific Results of the Voyage of the ' Vega.' 



- Baird, in the essay before cited, has reasonably accounted for this dispro- 

 portionate reciprocity between Europe and America ; but perhaps more than ho 

 has allowed for must be set down to the comparative want until lately of records 

 in the newer country. This want is being speedily supplied by the increased 

 study of Ornithology of recent years in Canada and the United States. 



