PREFATORY NOTE VU 



taken, it will be necessary to reset this portion if a larger edi- 

 tion is required; and in order to secure uniformity, the composi- 

 tion should be, if possible, in/ac simile. 



The illustrations of the present volume are chiefly those which 

 formerly appeared in the same author's "Key to North Ameri- 

 can Birds ". 



According to the report rendered by the author, the present 

 part of the work carries the subject through Passercs to Laniidce. 

 The whole consists in a systematic treatise on the families, gen- 

 era and species represented in the Colorado Valley — that is to 

 say, in the whole region drained by the Colorado Eiver of the 

 West and its tributaries, as far south as the present Mexican 

 boundary of the United States. The watershed of this great river 

 includes Arizona, much of New Mexico, Utah, and Nevada, a 

 part of the State of Colorado, and some of Southern California. 

 The faunal area thus circumscribed is nearly that of the " Great 

 Basin", and corresponds with the "Middle Faunal Province" of 

 some zoo-geographers, as distinguished from the "Western" and 

 ' ' Eastern " Provinces respectively. The main chain of the Eocky 

 Mountains, or great continental divide, bounds it on the east, as 

 the Sierras Nevadas do on the west. To the north hes the Salt 

 Lake Valley ; southward the boundary is an arbitrary political 

 one. In the last-named direction, the fauna changes insensibly 

 by the gradual gain of a "neotropical" complexion, though 

 many "nearctic" features are imj^ressed uijon the table-lands of 

 Mexico. The proper fauna of that country is prefigured in the 

 area under consideration by the various subtropical forms of bird- 

 life which have successively been found within the border of the 

 United States in the Valley of the Gila, as in that of the Lower 

 Eio Grande of Texas. Both to the east and to the west the 

 geographical boundaries already mentioned correspond quite 

 closely with the limits of the natural faunal areas ; for we miss 

 in the Colorado Valley some characteristic forms both of the 

 Pacific slope proper and of the Eastern United States at large. 

 Northward the Great Basin narrows like a wedge thrust in 

 between the converging Eastern and Western Provinces. 



No other portion of the United States of equal area offers 

 such varied surface conditions and such climatic extremes. The 

 region is hedged about by mountain ranges of immense extent 

 and elevation, and contains many other lofty chains and peaks, 

 while the greater part of the country is low, hot and arid. The 



