^ INTRODUCTORY. 



arboreal vegetation than by any meridian of longitude. It includes 

 Nebraska, the greater portion of Dakota, Montana, Wyoming, Colorado, 

 Kansas and Missouri, portions of Iowa and Minnesota, together with a 

 small area in the British Provinces near the head-waters of the Sas- 

 katchewan, where the Goteau de Missouri, running obliquely northwest- 

 ward, crosses the parallel of 49° N. Much of the western portions is 

 mountainous, as in Montana, Wyoming and Colorado, the easternmost ele- 

 vations of any note being the Black Hills, lying across the boundary of 

 Wyoming and Dakota. Extensive areas are cut up into Maiivnises Terres, 

 or "Bad Lands." Most of the region, however, is the great elevated 

 central plateau of the continent, of low mean annual rain-fall, and con- 

 sequently treeless, or nearly so, and more or less sterile, supporting for 

 the most part a comparatively meagre or stunted vegetation. Trees are 

 in effect restricted to the mountainous tracts and to a slender precarious 

 fringe along most of the larger streams. 



It results from these physical conditions that the Avi-fauna proper of 

 the region is not rich. Notwithstanding the great extent of country, 

 there is no single species absolutely confined to it. There are, however, 

 several abundant and generally diffused species which may be held by 

 this circumstance to be characteristic. Such are Eremophila leucolcema 

 (in the breeding season), Weocorys spraguei, Genironyx bainlii, Goturni- 

 cvlus lecontii, Zonotriehia harrisi, Galamospiza bicolor, Plectrophanes 

 ornatus and F. maccownii, Falco richardsoni, Pedioecetes eolumbianus, and 

 some others less distinctively of the same category. The great number 

 of species treated in the present volume is due to accessions from both 

 of the contiguous Paunal Provinces above mentioned, as well as of those 

 species of general diffusion over the continent, as most Baptores, Limi- 

 colcB, and Lamellirostres. It results from the extensive overlapping of 

 the Missouri Eegion upon the Eastern Province, that in effect nearly all 

 the birds of Eastern North America are represented fairly within this 

 area, the exceptions being chiefly the marine Atlantic species, and a 

 few others peculiar to the South Atlantic and Gulf States. The low 

 position of Saint Louis in the Mississippi Valley, which affords a ready 

 approach from the south, renders it probable that souie of these last 

 named, not yet known to proceed so far north, may finally be found 

 within Missouri limits. 



In discussing the western limits of eastern species, it is not easy to 

 overestimate the effect of the larger streams, and especially of the 

 great artery itself — the Missouri — in prolonging an eastern bird-fauna 

 in streaks to or toward the Eocky Mountains. These streams, with a 

 general east-and-west course, and with their usual fringe of trees, often 

 the only timber of various large areas, form attractive highways of mi- 

 gration, as it were, along which avenues birds push on beyond their 

 general limit. From this it results that the boundary line of the Middle 

 and Eastern Provinces in these latitudes is a zigzag of interdigitations. 



The general fades of the birds of this region may be summed in a 

 Digitized by Microson® 



