12 PACIFIC COAST AVIFAUNA No. 14 



tlu l!()li('iiii;m Waxwiii.u' and lliidsoniaii Cliickadcc. The ]\[ontana Junro rcplai-cs 

 llu' I'ink-sitled as it doos in thy northwestcru region. 



The northwestern mountain region includes the rest of tlie state. It lies 

 entirely west of the continental divide, from the western hoimdarics of the north- 

 eastern mountain region and the nor1hei-n lioundaries of the soiiUkth niountaiu 

 reprion, weslAvard and northwai'd to the limits of the state. It iinglit readily iu- 

 ttriiied tile humid mountain region, for it is much more, humid in climate tiuui 

 any other part nf Ihe state. Tt is characterized by a good many species and siii)- 

 species, such as Townscud Wai'hler, Chestnut-backed Chickadee, Varied Thrush, 

 Merrill Song Sparrow and Dusky Horned Lark. It really forms part of a re- 

 gion which includes northern Idaho and northeastern Washington, a region 

 where the rainfall is considerably greater than in surrounding areas both east- 

 Avard and westward, and where many Pacific Coast species find their eastern 

 limits. A more detailed study of the region, with a greater amount of collecting, 

 ought to bring out many interesting points and probably show some new sub- 

 species. 



The life-zones found in .Montana are the I'pper Sonoran. Transition, Cana- 

 dia:n, Hudsonian and Alpine- Arctic. These zones cross the faunal areas, theii' 

 boundaries being mainly at right angles to the mountain slopes. The l^pper So- 

 noran occupies the areas of lowest elevation, and the Alpine- Arctic those of higli- 

 est. Since these zones are better characterized by their vegetation, particularly 

 their trees, than by their birds, I shall give the species of trees which character- 

 ize them in Montana, to serve as an aid to others in studying this phase of dis- 

 tribution. 



The Upper Sonoran zone occupies the lower valleys of the state, mainly the 

 areas below 4,000 feet in elevation east of the continental divide, and those below 

 3,000 feet west of it. It occupies nearly all of the southern prairie region, and 

 extends in long narrow strips along the rivers to the westward. While tlii' 

 map of life-zones accompanying the 1910 A. 0. U. Check-List shows this zone 

 only in the southern prairie region, I am inclined, after a study of Gary's (1917 i 

 recent paper on Wyoming life-zones, to think that this zone also occupies certain 

 of the valleys in the mountain region which are of low elevation. If such species 

 as the ]Mourning Dove, Bullock Oriole, Arkansas Kingbird, Lazuli Bunting and 

 Catbird are characteristic of the Upper Sonoran in Montana, as they are in 

 Wyoming, then there must be many areas of upper Sonoran wirhin the moun- 

 tains. I believe that the Missouri Valley in Broadwater County, and areas along 

 the IMissouri as far south as Three Forks and perhaps up the Jefferson and ^ladi- 

 son, should be considered Upper Sonoran. I believe this is also true of areas 

 west of the continental divide, up the Hell Gate River at least as far as Jlissoula, 

 and on the Pend-Oi-eille nearly to Poison, and perhaps above Flathead Lake 

 about Kalispell. However, it seems quite certain that the species last named 

 above breed locally in the Transition. As in Wyoming, it is t?-ue that the line 

 between these two zones is indefinite and difficult to draw. Tliert are no very 

 characteristic trees in this zone. Junipers and cedars, which are characteristic 

 in other regions, are scarce, and grow quite as abrmdantly in tiie Ti-ansition as 

 in this zone. Cottonwoods are the commonest trees, but are also common in the 



