318 OKNITIIOLOGV. 



else, but simply tliat siuli a ])lace is where it is most abundant, or most 

 likely to be found ; and also, that the arrangement presented is based upon 

 the distribution of the species dunng the breeding-season. 



There are, however, certain species whose distribution seems to be in 

 nowise connected with vegetation, the considerations which influence their 

 range being the presence of water, of rocks, or of earth-banks ; but these 

 form a small proportion of the summer residents, most of them being the 

 jvater-fowl, and of these many might be assigned to the meadow series, 

 since they nearly all resort to the meadows to breed. 



The main natural subdivisions of the avifauna of the Interior, as above 

 determined, are the following : — 



/. Arboreal Avifnuua, 



1. Birds of the piue-region, or higher coniferous forests. (18 species.) 



2. Birds of the cedar or nut-pine groves. (9 species.) 



3. Birds of the aspen groves or copses. (7 species.) 



4. Birds of the caQou shrubberj'. (7 species.) 



5. Birds of the wooded river-valleys. (25 species.) 



//. Terrestriul Avifauna. 



0, Birds of the sage-bnisli. (10 species.) 



7. Birds of the mountain meadows, or parks. (9 species.) 



8. Birds of the lowland meadows. (8 species.) 



III. Mural Avifauna. 



9. Species strictly saxicoline. (2 species.) 



10. Species saxicoline only in nesting habits. (5 species.) 



11. Species nesting in earth-banks. (3 species.) 



IV. Aquatic Avifauna, 



12. Water birds. (41 species.) 



1. Birds of the pine -region, or higlier coniferous woods. — Compared with 

 the general extent of the Interior, the wooded portions ai'e exceedingly 

 limited, the only approach to a continuous forest encountered being that 

 clothing the eastern slope of the Sierra Nevada, and the more scant and 

 interrupted forests of the Wahsatch and Uintahs, on the opposite side of the 

 Basin. Between these two distant forest-clad mountain systems no true 

 forests exist, oidy a few of the loftier ranges supporting an extensive tree- 

 growth on their higher summits, forming islands, as it were, in a sea of desei-t 



