The Birds of El Paso County, Colorado 457 



yellow pines and cedars growing on them, and considerable 

 scrub oak and other shrubbery, and are good resorts for birds. 



The westerly part of the County forms part of the Pike 

 National Forest. 



LIFE ZONES. 



Owing to its varied topography we have within the bound- 

 aries of El Paso County no less than five life zones, as follows ; 



Upper Sonoran, Transition, Canadian, Hudsonian, and 

 Arctic-Alpine ; the first named comprising the plains region 

 and the very lowest foothills; the Transition the foothills and 

 the lower portions of the mountains, and the other three are 

 wholly mountain zones. Each of these zones is more or less 

 well characterized by the presence of certain plants and ani- 

 mals which are either peculiar to or largely confined to it. 



UPPER SONORAN ZONE. 



This zone, which is agriculturally the most important in 

 the County, as noted above covers the plains region. The 

 elevation of its upper boundary varies from a little over 6,000 

 to nearly 7,000 feet, depending on the steepness and exposures 

 of the slopes in the foohills, the limit naturally being higher 

 on slopes having a southern exposure than on those with a 

 northern. The pifions and cedars, which are usually consid- 

 ered as belonging to this zone, range even higher at times, 

 but such occasions are really overlappings into the Transition. 

 There are comparatively few of these trees in the County. 



In El Paso County the following mammals are confined 

 to this zone : 



Bailey's Wood Rat, Neotoma f. baileyi, Pale Grasshopper 

 Mouse, Onychomys I. pallescens, Yellow Pocket Gopher, 

 Geomys lutescens, Kangaroo Rat, Perodipus m. richardsoni, 

 Baird's and Plains Pocket Mice, Perognathus flavus and P 

 flavescens, Black-tailed Jack Rabbit, Lepns c. nielanotis , 

 Bailey's Cottontail, Sylvilagus a. baileyi, and possibly a few 

 others. 



