1921 9 



DISTRIBUTIONAL AREAS IN MONTANA 



IN discussing the factors that influence the distribution of birds in ^lontana it 

 is first necessary to emphasize the incompleteness of our present knowledge 

 of this subject. I have been unable to visit all parts of the state myself, and 

 r find the writings of others frequently inadej.(uate in the details which would 

 help one to determine life-zones or to learn much of either faunal or associational 

 distril)ution. However, I feel that the knowledge that has been obtained on this 

 subject is sufficiently valuable to warrant a digest of it here. 



As in other regions the factors concerned can be most easily comprehended 

 by considering three kinds of distributional areas, faunal, zonal and associa- 

 tional. In ^lontana the larger faunal areas are primary ones, rather than the 

 zonal. Even to the superficial observer crossing the state on one of the trans- 

 continental railways the division of the state into two large areas is apparent. 

 These are the prairie region of the eastern half and the mountain region of the 

 western. The line between these two areas crosses the state diagonally from 

 northwest to southeast, and the prairie region is about twice the area of the 

 mountain region. 



The prairie region is characterized by such breeding birds as the IMcCown 

 Longspur, the Chestnut-collared Longspur, and the Clay-colored Sparrov/. 

 Other species found throughout the eastern United States find the western limits 

 of their normal breeding range in this region. Such species are the Red-headed 

 Woodpecker, Bronzed Grackle and Brown Thrasher. Other eastern species mi- 

 grate regularly through the prairie region, but are rare or unknown west of it. 

 Such are the ]Myrtle and Blackpoll warblers. 



The mountain region is characterized by a large number of Rocky Mountain 

 species such as the Richardson Grouse, Lewis Woodpecker, Rufous Hummingbird, 

 Black-headed Jay, Western Tanager, and JMountain Chickadee. There are a 

 certain numlier of w^estern species that range over both regions and are found 

 well distributed throughout the state, such as the Magpie, Black-headed Gros- 

 beak and Western ]\Ieadowlark. 



My personal acquaintance with the prairie region is less than with other 

 parts of the state. Certain large areas in it have never been studied ornitholog- 

 ically, at least, if so, the results have not been published. For these reasons the 

 statements made about this region will probably be subject to considerable future 

 modification. The region may be divided faunally into three parts. These are 

 the southern region, the northeastern and the northwestern. 



The southern prairie region extends over the southeastern part of the state, 

 west ta the foothills of the mountains in Carbon, Sweet Grass and Meagher coun- 

 ties, and north about to the divide between the Yellowstone and Missouri drain- 

 ages. The region is characterized by the regular occurrence of such species as 

 the Pinyon Jay, Western Lark Sparrow, Western Field Sparrow and White- 

 winged Junco, and by the western limits of such eastern species as tlie Black- 

 billed Cuckoo, Chimney Swift and Ovenbird. 



The northeastern prairie region lies north of the southern, extending west 

 to tlie middle of Choteau and Fergus counties. It is very little known except 



