Occasional Papers of the Museum of Zoology 19 



The black spruce forest is not as a rule very dense, and a person 

 can usually pass easily between the trees. The ground is heavily 

 covered, to a depth of from several inches to several feet, with 

 sphagnum moss, which retains a large amount of moisture. Vari- 

 ous shrubs grow in the available space between the trees, the 

 principal species being the dwarf birch, Betiila glandulosa, blue- 

 berries, Vaccinnum, dwarf willows, Salix, dwarf alders, Alnus, 

 and Labrador tea. Ledum. A few tough grasses of the type found 

 in the niggerheads also occur, nearly covered by the sphagnum. 



Lakes which occur in an area of black spruces are commonly 

 invaded at their edges by the sphagnum. About such lakes the 

 vegetation is usually not different from that of the black spruce 

 forest, and no fringe of shrubs or other plants is developed. Neither 

 is there any evidence for the presence of a water-margin vertebrate 

 society about such lakes. 



Timber-line willow-alder habitat and association: 



Lagopus lagopus albus. Willow ptarmigan. Resident. 



Lagopiis rupestris rupestris. Rock ptarmigan. Resident. 



Asia flammeus. Short-eared owl. Summer (Osgood). 



Zonolrichia gambeli. Gambel sparrow. Summer. 



Junco hyemalis hyemalis. Slate-colored junco. Summer. 



Wilsonia pusilla pusilla. Wilson warbler. Summer. 



Penlhestes hudsonicus hudsonicus. Hudsonian chickadee. Summer. 



Acanthopneuste borealis kennicotli. Kennicott willow warbler. Summer. 



Rcgulus calendula calendula. Ruby-crowned kinglet. Summer. 



Planesticus migratorius migratorms. Eastern robin. Summer. 



Ixoreus ncevius meruloides. Northern varied thrush. Summer. 



Sorex personalus arclicus. Arctic shrew. 



Evotomys dawsoni dawsoni. Dawson red-backed vole. 



Lepiis americanus macfarlani. Macfarlane snowshoe hare. 



Thickets of scrub willow or alder frequently occupy the moist 

 ground at the head of a ravine or cove at timber-line or above, 

 and any small stream flowing above timber-line is likely to be 

 fringed by a thicket of these shrubs. Tongues of stunted willows 

 and alders also extend up protected slopes and gullies for a long 

 distance above timber-line. A fringe of alders was found on 



