134 



NAIURALIST'S GUIDE TO THE AMERICAS 



give birth also to branches of the Nass, 

 the Skeena, and the Finlay. 



A typical valley, that of the Upper 

 Ispatseeza, may be described in some 

 detail. It varies from a mile or less to 

 several miles in width. Long stretches, 

 perfectly level, having a gravelly soil 

 covered with a good growth of grass, 

 are frequent, and these often succeed 

 each other as terraces, with altitudinal 

 differences of only a few feet, or may 

 alternate with gently undulating mea- 

 dows clothed with patches of willows 

 and dwarf birches, or with stunted white 

 spruces, which merge gradually into the 

 fairly well grown forest which covers 

 the sides of the bordering mountains. 



These valleys though largely treeless 

 correspond to the stunted forest belt 

 of the Mackenzie and most of their 

 woody plants are the same. With them 

 are found also certain Rocky Mountain 

 plants, including the large blue larkspur 

 {Del-phinium menziesii), western ane- 

 mone (Pulsatilla occidentalis) , and the 

 yellow paint brush (Castilleja pallida). 

 Mammals more or less characteristic 

 of these broad valleys are the Osborn 

 caribou (Rangifer osborni), the hoary 

 marmot {Marmota caligata oxytona), 

 the Yukon ground squirrel [Citellus 

 plesius), and the British Columbia 

 lemming {Lemmus helvolus). The most 

 characteristic birds are the willow 

 ptarmigan {Lagopus lagopus) which 

 breeds almost entirely on these brushy 

 meadows, the golden-crowned sparrow 

 (Zonoirichia coronata), and the western 

 tree sparrow {Spizella monticola 

 ochracea) . 



In these valleys, usually at the sources 

 of streams, sometimes in the forest, and 

 sometimes above the timberline, lakes 

 of clear water occur. About these nest 

 Barrow's goldeneye. 



Bordering the valleys a zone of spruce 

 usually covers the lower slopes of the 

 mountains, which are treeless above an 

 altitude of about 5000 ft. The summits 

 of the mountains are usually rocky, 

 sometimes craggy and precipitous, but 

 hold many gently sloping meadows and 

 hanging valleys, well-watered and sup- 



porting an alpine flora of great beauty. 

 The fauna of the peaks include the 

 mountain sheep {Ovis d. stonei) and 

 the mountain goat {Oreamnos m. colum- 

 bianus) which usually, but not in- 

 variably, choose different mountains, 

 the hoary marmot, the white-tailed and 

 rock ptarmigan, the pipit, the Alaska 

 horned lark, and the Hepburn rosy 

 finch. 



Below the level of these broad valley 

 meadows, where the streams cut their 

 way down to the deeper canyons of the 

 main valleys, the trees are those of the 

 main transcontinental forest, with an 

 infusion of west coast types. Populus 

 trichocarpa replaces Populus balsami- 

 fera, and the red-berried elder is occa- 

 sional in the damper situations. The 

 plants, however, are virtually the same 

 as those of the great interior forest as 

 far down the Stikine as the Little Can- 

 yon, below which the flora and fauna 

 changes abruptlj^ to that characteristic 

 of the coast region, elsewhere con- 

 sidered. In these lower valleys and the 

 adjacent slopes up to about 2000 ft. 

 (Canadian Zone), certain birds of the 

 Athabaska-Mackenzie region are com- 

 mon, including gray ruffed grouse, yel- 

 low-bellied sapsucker, eastern night- 

 hawk. Say's phoebe, alder flycatcher, 

 rusty grackle, Gambel's sparrow, west- 

 ern chipping sparrow, junco, cliff swal- 

 low, barn swallow, western warbling 

 vireo, Tennessee warbler, redstart, olive- 

 backed thrush, hermit thrush, with 

 many others. With these are found the 

 following which are mainly confined to 

 the Rocky Mountain region: Hammond 

 flycatcher, Wright flycatcher, violet- 

 green swallow, Macgillivray warbler, 

 Myadestes townsendi, and Ixoreus naevius 

 meruloides. 



Yukon: Yukon, stretching through 

 nearly ten degrees of latitude, and 

 extending from the Arctic Ocean nearly 

 the Pacific, lies between Mackenzie, 

 British Columbia, and Alaska, and sends 

 rivers of considerable size to all of these 

 adjacent regions. Its affinities are close 

 to Alaska, owing to its contributions 

 to the Yukon, Alaska's main waterway. 



