The Birds . of El Paso County, Colorado 461 



Of birds, the Rocky Mountain Jay, Rocky Mountain Pine 

 Grosbeak, and Rocky Mountain Creeper probably breed prin- 

 cipally within the limits of the Hudsonian, though there are a 

 number of other breeders in common with other zones. 



The only tree which seems to be confined to the Hudsonian 

 is tlie Foxtail Pine, Pinus aristata, which grows from 10,250 

 f ( et up to timberline. This zone also includes the upper por- 

 tion- r f the Engelminn's Spriice and White Pine forests, and 

 in it arc also found the willows mejilioned under the Canadian 

 as common to both. 



ARCTIC-ALPINE ZONE. 



The Arctic-Alpine Zone is the region above timberline, 

 characterized by slopes devoid of trees and with but four 

 species of woody plants growing thereon, though a number 

 of flowering plants are characteristic of it, or nearly so. 



No species of mammals is restricted to this zone, but it 

 shares a number of species with the zone below, some of which 

 live here the year round, and others, like the Mountain Sheep, 

 Fox, Coyote, and Black Bear, range into it from below. Some 

 of the species living in this zone the year round are the Wood- 

 chuck, Cony, Rocky Mountain Field Mouse, and Colorado 

 Pocket Gopher. 



One species of bird is restricted to this zone in the breed- 

 ing season, the Brown-capped Rosy Finch, atid the Pipit is 

 practically so, and the Desert Horned Lark also breeds in the 

 bare spaces, while the White-crowned Sparrow and Pileolated 

 Warbler breed in the willow thickets for five hundred feet 

 above timberline. The Sparrow has been known elsewhere 

 in the State to raise a brood at a lower elevation early in the 

 season, and then to move above timberline and raise a second 

 family, but we have no information as to whether it does 

 this here. A few other birds range intermittently above tim- 

 berline. 



But four species of woody plants grow above timberline, 

 the Dwarf Willow, Salix saximontana, and another willow, S. 



