DISTRIBUTIONAL AREAS IX MONTANA 



IN discussing the factors that influence the distribution of birds in Atontinin it 

 is first necessary to emphasize the incompleteness oi our prcsiiit L-no\\ 1im1i;<- 

 of 1liis subject. I iia.ve l)een finable to visit all jiarts of the st:Ui- iiiyscir, and 

 I find till' writinus of others frequently inadequate in the details wiiieli would 

 help one to detei-inine life-zones or to learn much of either fauna! or assoeialinnal 

 distribution. Iliiwever, 1 feel that the knowledge that, has been obtained on this 

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



As in othei- i-eijions the factors concerned can lie most easily comprehended 

 by cousiderini;- three kinds of distributional areas, faunal, zoniil and associa- 

 tional. in .Montana the laruer faunal areas are primary ones, rather than the 

 zonal. Kven to the superficial oliserver crossing the state on one of the ti'ans- 

 continental i-ailways the division of the state into two large areas is apparent. 

 These are the praii'ic I'egion of the eastern half and the mountain region of the 

 M'estern. The line between these two areas crosses the state diagonally from 

 lUH'thwest to southeast, and the prairie regii n is iibont twice the area of the 

 mountain region. 



The praii'ie region is cliaraetei'ized liy such breeding birds as the .'\Ic('o\vn 

 Longs]iiir, the Chestnut-collai'cd I.ongspui'. and the Clay-colored Sjiarrow. 

 Other species found thi'ouglioiit the e:istern I'nited States find the western limits 

 of their normal lireeding range in this I'egion. Sucli species arc the Reddicaded 

 Woodpeckei-. Iironzed Gracklc and Bi'own Thrashiu'. (~)thei' eastern s|)eeies mi- 

 grate regularly through the priiirie i-egion, but are I'aiv or uid^nowu west of it. 

 Such are the .Myrtle nnd i;iack].oll warblers. 



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

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

 Black-headed Jay, Westiu-n Tanager, and ^lountain Chickadee. There are a 

 ""•ertain number of westei'u species that range over both regions ;iiiil are found 

 Well distribulcd thi'oughout the state, such as the Magpie, Black-headed (Jros- 

 beak and Westeiai .^leadowlai'k. 



^ly jiersonal aci|uaintance with the prairie region is less than with other 

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

 ically. at least, if so, the residts have not been ])idilished. For these reasons the 

 statements mach' about this region will proliably be sidjject 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 to the foothills of the mountains in Carbon, Sweet Grass and Jleagher coun- 

 ties, and north al)out to the divide between the Yellowstone and Jlissouri drain- 

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

 the Pinyon Jay, Western Lark Sjjarrow, Western Field Sparrow and Wlnte- 

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

 billed Cuckoo, Chimney Swift and Ovenbird. 



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

 to the middle of Choteau and Fergus comities. It is very little known except 



