460 Colorado College Publication 



mys fossor. Western Red Fox, Vulpes macrourus, Shrew?, 

 Sorex V. dobsoni, S. personatus, and 5". obscurus, and Water 

 Shrew, Neosorex navigator. 



The following birds have their center of abundance in 

 the breeding season in the Canadian Zone : 



Dusky Grouse, Alpine Three-toed Woodpecker, Red- 

 naped Sapsucker, Williamson's Sapsucker, Olive-sided Fly- 

 catcher, Cassin's Finch, Crossbill, Gray-headed Junco, Audu- 

 bon's Warbler, Red-breasted Nuthatch, Ruby-crowned Kinglet, 

 Townsend's Solitaire, and Audubon's Hermit Thrush. 



Though found also in the Hudsonian the heaviest portions 

 of the forests of Limber or Rocky Mountain White Pine, 

 Pinus flexilis, and Engelmann's Spruce, Picea engelmanni, 

 are in, the Canadian Zone. The Aspen, Populiis tremuloides, 

 lias its center of abundance in the Canadian and ranges but 

 little above it. The following willows are common to it and 

 the Hudsonian: Nuttall's or Black Willow, 5". nuttalli, Bog 

 Willow, S. glaucops, and Green-leaved Willow, 5'. chlorophylla. 



HUDSONIAN ZONE. 



This is the zone immediately below timberline, above the 

 Canadian ; it is intermediate in character between that and the 

 Arctic -Alpine Zone, not having any very strongly marked 

 characters of its own, but in its lower limits having much in 

 common with the Canadian, and in the upper portions sharing 

 some of the characteristics of the Arctic-Alpine. Its upper 

 limit varies in altitude from 11,500 to 12,500 feet. 



As stated above under the Canadian Zone, a number of 

 species of mammals are common to these two zones, or rather 

 characteristic of the two together. Of these the Woodchuck 

 is more abundant toward timberline, and rangps into the zone 

 above, and two additional species, the Cony, Ochotona saxa- 

 tilis, and Mountain Sheep, are more especially characteristic 

 of this and the zone above, the former being found, in the 

 Pike's Peak Region, mostly from a little below timberline up 

 to the summits of the mountains. 



