.\orlh .tmrrican numtaiw forrst bioriution 



This biociatioti, considering tlic forest-interior 

 and forest-edge together, occurs principally in the 

 coast forest (Storer, et al. 1944, Miller 1^51, Macnab 

 1958) and is less developed in the montane and siih- 

 alpine forests of the Rocky Mountains, Cascades, and 

 Sierra Nevada. There appear to be no important 

 subdivisions related to the several plant associations 

 that it covers ( Rasmussen 1941, Hayvvard 1945, 

 Munroe 1956, Snyder 1950). Because of the moun- 

 tainous terrain and the many possibilities for popu- 

 lations to become partially or wholly isolated from 

 each other, there are many local subspecies and spe- 

 cies of mammals and birds (Findley and Anderson 

 1956). The following lists include only common 

 species of wide distribution through the biociation. 



Shrews 



Mountain beaver 

 Yellow-bellied marmot 

 Golden-mantled ground 



squirrel 

 Western chipmunks 

 Douglas' squirrel 

 Bushy-tailed wood rat 

 Red-backed mice 

 Heather vole 



Mammals 



Long-tailed vole 

 Western jumping mice 

 Grizzly bear 

 Western marten 

 Mountain weasel 

 Wolverine 

 Mountain lion 

 Bobcat 

 Mule deer 

 Wapiti 



Birds 



Golden eagle 

 Blue grouse 

 Flammulated owl 

 Pygmy owl 

 Calliope hummingbird 

 W' illiamson's sapsucker 

 White-headed wood- 

 pecker 

 Hammond's flycatcher 

 Western flycatcher 

 Western wood pewee 

 Steller's jay 

 Clark's nutcracker 



Mountain chickadee 

 Pigmy nuthatch 

 \'aried thrush 

 Mountain bluebird 

 Townsend's solitaire 

 Audubon's warbler 

 Townsend's warbler 

 Hermit warbler 

 Western tanager 

 Evening grosbeak 

 Cassin's finch 

 Oregon junco 

 Gray-headed junco 



Additional species from the chaparral biociation 

 penetrate this community, particularly into shrubby 

 stages. The orange-crowned warbler is noteworthy 

 in this respect. 



In general, the population of breeding birds is 

 less than one-sixth what it is in the boreal forest 

 (Snyder 1950). In the northern Rockies there is con- 

 siderable mi.xture with species from the boreal forest 

 biociation, both in birds and mammals, but these 

 species drop out progressively southward and very 

 few of them cross the Cascades into the Coast forest. 

 The woodland caribou, for instance, ranges only to 



northeastern British Columbia and the moose to 

 central British Columbia, eastern Idaho, and western 

 Wyoming. The western facies of the deciduous for- 

 est-edge biociation penetrates widely as a serai stage 

 through the western forest biociation, and certain of 

 its S])ecies may persist into the climax. 



'.urasian 



boreal forrst biorialion 



The dominants of the Eurasian jjlant associa- 

 tions are different species but the same genera of 

 pines, firs, larches, spruces, poplars, and birches that 

 occur in North America. This biociation is best de- 

 veloped in Asia, from whence the biota is dispersed 

 across the northern part of the continent into Europe 

 (Berg 1950, Jahn 1942, Kalela 1938, Palmgren 

 1930, Pleske 1928, Stegmann 1932, 1938, Haviland 

 1926, Schafer 1938, Soveri 1940, Turcek 1956). 



The mammal fauna contains shrews, a varying 

 hare, flying and red squirrels, a chipmunk, red- 

 backed mice, the wolf and red fox, a brown bear, 

 martens, weasels, wolverine, lynx, a moose, and a 

 deer. Several of these species (wolf, red fox, wol- 

 verine, lynx) are considered by some taxonomists 

 to be conspecific with North American forms 

 (Rausch 1953). 



This biociation is equivalent to the Siberian bird 

 fauna of .Stegmann (1938) and includes several spe- 

 cies of grouse, owls, woodpeckers, crows and jays, and 

 tits, a creeper, several thrushes, several Old World 

 warblers, kinglets, a wagtail, waxwings, and several 

 finches or sparrows. The wood warblers, abundant 

 in the boreal forest of North America, are absent. 



PALEO-ECOLOGY 



In early Tertiary we may suppose that the 

 boreal unit of the Arcto-tertiary forest had a fairly 

 uniform animal composition from eastern Canada into 

 Asia and Europe. As the forest progressed southward 

 during the middle and later Tertiary, a large segment 

 became separated in consequence of the submergence 

 of the Bering land bridge, becoming the Eurasian 

 biociation. Forms now peculiar to the Eurasian and 

 to the North American biociations must have evolved 

 after this separation took place (Udvardy 1958). 



In North America, as the Arcto-tertiary biota 

 retreated southward with the progressive chilling of 

 the continent, it was separated into two portions by 

 the northward invasion of grassland over the Great 

 Plains, except as it had contact through the boreal 

 forest across Canada in the north. During the Pleis- 

 tocene even this northern contact was broken (Fig. 

 21-2) with each major advance of the glacier. Fur- 

 thermore, the western part of the continent was 



Coniferous forest, woodland, and chaparral biomes 307 



