1916] Dice: Land Vertebrates of Southeastern Washington 297 



study the extent to which the different species are restricted to par- 

 ticular habitats. The habitats have been described in some detail in 

 order to facilitate comparison with the habitats of other regions. 



The attempt has been made to study and describe the habitats and 

 associations in as nearly their native and normal conditions as pos- 

 sible, but for many habitats it has been difficult to find a sufficient area 

 retaining anything like the original conditions. 



While many of the associations here considered could be^easily sub- 

 divided or several could perhaps be combined, yet it is believed that 

 the present arrangement is the most useful one for the study of verte- 

 brate distribution in the region. A region is divided into associations 

 as a matter of convenience in studying and describing the environ- 

 ments and the habitat preferences of the animals. To increase the 

 number of associations unduly would destroy the convenience of use 

 for which the classification is made, while to lump the associations 

 might obscure important facts. It cannot be hoped that the relative 

 abundance of the species in the different associations as here given is 

 fully accurate, for the observations on which the results are founded 

 are known in many cases to be too few in number. 



In order to show the relative abundance of each species in the dif- 

 ferent habitats it has been desirable to use a system of nomenclature 

 modified from that used by Grinnell (1914, p. 67) . As here considered, 

 the relative abundance of each species in the different habitats of the 

 same area is compared. No attempt is made to compare the relative 

 abundance of a species in the different faunal areas. When a species 

 occurs in only one habitat in an area, this is designated the exclusive 

 habitat. If the species occurs in more than one habitat in the area, the 

 habitat in which it occurs most abundantly is said to be its major 

 habitat and all others are said to be minor habitats. If the data are 

 insufficient to determine the major habitat, the term reported is used 

 to refer to each habitat in which the species is known to occur. The 

 relative abundance in the different habitats has been determined on 

 the basis of the comparative number of individuals actually observed 

 or trapped in each. 



Active observation of the birds in the region near Prescott was 

 begun by the author in December, 1904, and attention was later 

 directed to the other vertebrates. The observations have been much 

 interrupted by the conflicting claims of other duties and by prolonged 

 absences from the region. In the summer of 1914 ten days were spent 

 in the region near Wallula, a shorter excursion was made to Lyon's 



