voccinium 



ribes 



swainson ^ 

 .thru 

 douglos fir 

 amelanchier 



SPRUCE-FIR FOREST 



alpine fir 

 lonicera rubus 



FIG. 23-3 Foraging niches of birds in the western forest bl< 

 tion of the central Rocky Mountains (Salt 1957). 



hardwoods, several warblers and other species nor- 

 mally characteristic of coniferous forest have learned 

 to occupy niches in the deciduous forests as well, and 

 attain high populations therein (Saunders 1936, 

 Brooks 1940, Kendeigh 1945). The species composi- 

 tion of foliage insects in the coniferous forests of the 

 Smoky Mountains is essentially similar to that of 

 the deciduous forest (Whittaker 1952). Such gen- 

 eral intermingling of species in an ecotone is to be 

 expected, and may be considered characteristic of the 

 Appalachian faciation. 



Perhaps some species listed above reach larger 

 populations in a serai shrub or forest-edge biocies 

 (Adams 1909). The Philadelphia vireo. palm war- 

 bler, Wilson's warbler, rusty blackbird, and Lin- 

 coln's sparrow are largely limited to shrubs or 

 second growth ; the northern waterthrush occurs in 

 bogs; the savannah sparrow, in marshes and grassy 

 areas; and the white-winged crossbill, irregularly 

 through the climax. These species extend to the 

 northern tree-line. Serai aquatic stages in the boreal 

 forest contain beaver, muskrat, and nesting horned 

 grebe, black duck, common goldeneye, Canada 

 goose, and the common and hooded mergansers 

 (Hanson et al. 1949). Actually, the coniferous forest 

 does not develop a recognizable forest-edge along 

 its southern border because these borders grade 

 by steps into deciduous forest, aspen parkland, wood- 

 land, and chaparral. The closest resemblance to an 

 edge are shrubby openings within the forest or the 

 subseres that develop in bogs, burns, and logged 

 areas. The aspen parkland contains a fauna in which 



boreal, grassland, deciduous forest, and deciduous 

 forest-edge biociation species are represented (Bird 

 1930) and is essentially an ecotone. Invertebrate 

 composition of the serai stages bears a strong resem- 

 blance to that occurring in serai stages of the decidu- 

 ous forest. 



Along its northern border, the coniferous forest 

 comes in direct contact with open tundra to form a 

 broad ecotone. Boreal forest biociation species 

 reach their northern limits of distribution and tundra 

 species begin to appear. There are no distinctive 

 mammals, but several birds are characteristic of this 

 subarctic, lichen woodland and muskeg, Hudsonian, 

 or (most apt) forest-tundra faciation (Manning 

 1952, Harper 1953, 1956, Preble 1908) : 



Solitary sandpiper 

 Lesser yellowlegs 

 Rough-legged hawk 

 Boreal owl 

 Hawk-owl 

 Great gray owl 

 Northern shrike 

 Gray-cheeked thrush 

 Bohemian waxwing 

 (west) 



Blackpoll warbler 

 Pine grosbeak 

 Hoary redpoll 

 Common redpoll 

 Tree sparrow 

 Harris' sparrow 

 White-crowned sparrow 

 Fox sparrow 



The pine grosbeak, white-crowned and fox sparrows 

 extend to the southward at tree-line on the western 

 mountains and the gray-cheeked thrush and black- 

 poll warbler extend southward at high elevations in 

 the northern Appalachians. 



306 Geographic distribution of communities 



