V ,°g 93 X ] Allen, Origin and Distribution of N. A. Birds. I -JQ 



maritime or pelagic. Of the 10 peculiar land birds, all but one 

 are congeneric with and for the most part closely allied to North 

 American species. Of the 24 subspecies, 23 are merely local 

 races of North American species. A number of these peculiar 

 species and subspecies are confined to the subtropical portions of 

 the region below La Paz, which belongs to the American 

 Tropical Realm rather than to the Temperate Realm, thus leav- 

 ing very little of distinctive importance for the non-tropical 

 portion of the Peninsula. 



It is at present impracticable to attempt to define in detail the 

 numerous faunae of the Arid Province. While certain portions 

 might be thus treated, our knowledge of the region as a whole is 

 too defective to warrant even a provisional subdivision into fauna? . 

 The same is true also of the southern prolongations of the Cold 

 Temperate along the mountain ranges of the western half of the 

 continent. It is evident, without going into a detailed analysis, 

 that many of the wide-ranging species that prevail over and give 

 character to the Arctic, Hudsonian, and Canadian Faunae, re- 

 spectively, are absent from the Rocky, the Cascade, and the 

 Sierra Nevada ranges and their outlying spurs ; also that manv 

 eastern forms are here replaced by more or less closely related 

 western forms, and that quite a number of peculiar mountain 

 types are superimposed upon this new combination. The case is 

 obviously quite different from the conditions met with in the 

 Alleghanies, where merely a small percentage of Canadian forms 

 occur far to the southward of where they are found in the con- 

 tiguous lowlands. To give due expression to the faunal condi- 

 tions met with, for example, in the Rocky Mountains south of 

 the Canadian Pacific Railroad, it evidently will be necessary to 

 recognize a succession of mountain faunae as we go southward, 

 as well as in descending from timber-line at any given point to 

 the foot-hills. Dr. Merriam, in defining the life zones at high 

 elevations in Arizona, Idaho, and California, has made an excel- 

 lent beginning in this comparatively new line of work, and we 

 may confidently look forward to still more important results from 

 the great mass of unpublished data he has so industriously 

 brought together. The proper collation of our mountain areas, 

 from the British boundary across the United States into Mexico, 

 will be a work of exceptional interest and importance, and will 

 require much additional fieldjresearch. 



