Vegetation 



Some components of the vegetation varied by 

 stand condition while others did not (table 1). 

 Obviously the cutover areas had significantly less 

 tree basal area and d.b.h. than the uncut controls. 

 The clearcuts had some tree basal area and d.b.h. 

 because, where possible, snags of all species and live 

 paper birch were left for use by birds and animals. 

 Percentage of total tree cover (made up of seedlings, 

 saplings, and pole-size and larger trees) signifi- 

 cantly increased fi'om clearcut through partial cut 

 to uncut units. Although the pole-size and larger 

 trees followed this pattern, sapling-size trees were 

 not significantly different between the cutover 

 areas. Seedling cover was not significantly 

 different among stand conditions. 



Following timber harvest, total shrub cover 

 (percent) on partial-cut and uncut stands was 

 significantly greater than on clearcuts (table 1). 

 The tall-shrub and mid-shrub components were 

 decreased substantially on clearcuts compared to 

 partial cuts or the uncut controls. Low shrub cover 

 on clearcuts was significantly less than on the uncut 

 stands, and was intermediate (but not significantly 

 different) on partial cuttings. 



Neither the graminoid nor the forb cover was 

 significantly different among the stand conditions 

 after the cutting treatments (table 1), but twice as 

 much average graminoid cover occurred on cutover 

 than on uncut areas. Conversely, forb cover within 

 the cutover stands was about half that of the uncut 

 areas. 



DISCUSSION 



For the bird species and guilds that exhibited 

 significantly different means among stand condi- 

 tions, abundance patterns seem biologically reason- 

 able in light of their habitat requirements. For 

 example, tree swallows were most abundant in 

 clearcuts with some snags and birch trees reserved 

 (fig. 4). For these members of the flycatching and 

 secondary-cavity nesting guilds, open, meadowlike 

 habitat with nest-tree resources is probably ideal 

 habitat. Likewise, dark-eyed juncos, as ground 

 foragers and ground nesters, were most abundant 

 in clearcuts and partial-cut units. In contrast, the 

 members of the conifer tree nesting guild, with 

 species like golden-crowned kinglet and Townsend's 

 warbler, were less abundant in clearcuts than 

 elsewhere (tables 2 and 3). 



Ruby-crowned kinglets and fox sparrows were 

 most abundant in partial-cut stands and unlogged 

 forests interspersed between the cutting units. 

 Perhaps an increase in edge habitat is beneficial to 

 these species; males of both species were frequently 



heard singing from conifers adjacent to clearings. 

 Chipping sparrow and American robin were least 

 abundant in the CRNA and relatively abundant in 

 the unlogged forest on the THSA, pointing out that 

 they may favor edge habitat in conjunction with 

 open stands. 



The pine siskin, a foliage-foraging and conifer- or 

 broadleaf-tree nesting species showed a significant 

 interaction between habitat and year for abundance, 

 but this was due to a dramatic increase in abun- 

 dance during 1990 in all habitat categories of the 

 study. This species is known for sporadic, large 

 changes in abundance and irruptive foraging be- 

 havior. Abundance of pine siskins within harvested 

 habitat is the result of retaining living birch trees 

 and the small size of the cutting units. These two 

 factors may also have increased the abundance of 

 other members of the conifer/broadleaf tree nesting 

 guild (table 3). 



Varied thrushes showed a significant habitat and 

 year interaction for abundance. No varied thrushes 

 were detected while censusing during 1990 even 

 though these birds were relatively common in 1989. 

 Censusing during 1991 may help to clarify which 

 year was unusual for this species on the study area. 

 Varied thrush is the only species among those that 

 were most abundant in unharvested areas to have 

 a significant difference in numbers between the 

 unlogged forest and the natural area (table 2). 

 This may illustrate a qualitative difference for this 

 species between contiguous and fragmented old- 

 growth forest. 



A habitat and year interaction for abundance 

 was also significant for ground-foraging and ground- 

 nesting guilds. The number of ground foragers 

 increased from 1989 to 1990 in clearcut, partial cut, 

 and unlogged forest, but decreased in the CRNA. 

 Numbers of ground nesters also increased more in 

 partially cut areas than elsewhere. These patterns 

 are shifts away from contiguous forest toward 

 harvested and fragmented forest. A time-lag effect 

 following logging, as described for these guilds, 

 seems reasonable in light of the possibility of site 

 tenacity by breeding birds (Atwood and Massey 

 1988). Adults may be predisposed to return to the 

 same site to breed following migration, and they 

 may not have time immediately upon arrival to 

 search for other potential territories. If this is true, 

 they may correct the situation in late summer when 

 they have time to search for a new site. 



Because more than half of the species included 

 in the statistical analysis did not show significant 

 differences in abundance among stand conditions, 

 it is possible that factors related to logging may not 

 affect the majority of species if reserving snags and 

 live trees, and if small harvest units surrounded by 



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