1921 BIRDS OF MONTAiNA 21 



ill tliis association, and in tiir mountain footliills 1 iiave found n.'sls of tlir West- 

 ern Cliiiiping Sparrow and Pink-sidetl Junco in sage-covered areas. 



The wild-rose association consists of thickets of shrubs that occur on tlie 

 sides of moist eouh'es on the pirairies and about the foothills of the mountains. 

 While the wild-rose is oiie of the most abundant shrubs, many others are found, 

 such as currant and goo.seberrv { Rihrs), buffalo-berry (>SIn jilnrdin) . silver berry 

 (Elcagnus), snowberry {SiiinjiliDrirarpus), and thorn [Cyattu (jus) . 'I'lie most 

 characteristic species of this association are tlie Wright Flyeat^-lier, Magpie, 

 Brewer Blackbird, Clay-colored Sparrow, Arctic and Green-tailed towhees. Lazuli 

 Bunting, MacGillivray Warbler, Western Yellowthroat and Catbird. 



The cin(iuefoil association is found maiul.y in the northwcst( fn ])rairie re- 

 gion, where sage-brush areas do not occur. It consists of low scatlci'ed bushes ol' 

 the shrubb,y cinqnefoil (Dasiophora fruticosa) . forming a growth that very mucli 

 resembles sage. A few other shrubs, such as the buffalo-berry and silver berry, 

 are found in small quantity with it. Its bii'ds are the Marsh Ilauk, Shoil-eared 

 Owl, Sharp-tailed Grouse, Brewer Blackbird, Vesper Sparrow. Clay-colored Spar- 

 row, and certain others. There being often bodies of water closi: by. ducks ocea- 

 sionall.y nest in this association. Many species which live upon tiie open grass 

 areas of the prairie are liable to place their nests in this association because of 

 the protection the shrubs afford. 



Tree associations cover a larger |)art of the area of the state than any other 

 group except the grass associations. They support a, larger amoiinl of bird life 

 per unit of area than the grass associations and are therefore of greater iiiiixirt- 

 ance in their influence on bird distribution. We may make two general ilivisious 

 of the tree associations, broad-leaf trees and coniferous trees, though there is at 

 lea.st one well-marked association, west of the continental divide, tlu'* is a mixture 

 of both. The broad-leaf tree associations are but two in number, cottonwood 

 groves and aspen groves. 



Cottonw-oods are found along streams in the I'pper Sonoran and Transition 

 zones, mainly in the prairies and mountain valleys. (See fig. 3.) Four species of 

 Populiis are represented, P. ddtoidcs in the eastern part of the state. /'. Inilsain- 

 ifcra and P. angustifolia throughout most of the state, and /'. trichocarpa west of 

 the divide. While these species are the only trees, there is a considerable under- 

 growth of .young cottonwood, willows, dogwood (Cornus stoJonifrra) and other 

 shrubs. There are many species of birds breeding in this association, and bird life 

 is usuall.y abundant in it, particularl.v in small groves that occur at long intervals 

 in prairie regions. Some of the most characteristic species are the Swainson 

 Hawk, Horned Owl, Red-shafted Flicker, Kingbird, Western Kingbird, Western 

 Wood Pewee, Least Flycatcher. Magpie, Crow, Bullock Oriole, Goldfmc-h, Cedar 

 Waxwing, Red-eyed Vireo, Yellow AVarbler, Redstart, House Wren, Long-tailed 

 Chickadee and Robin. 



The aspen grove is found chiefly in the lower mountains in the western half 

 of the state, occupying the Transition and lower Canadian zones. It consists 

 almost entirel.v of the aspen (Popiilns frcnnilnidi s) . which forms small grove.-? 

 in somewhat moist .soil in the lower mountains. The area of this association is 

 not great, but tiiere are a few sjiecies of i)ir(ls that are characteristic of it antl in 



