Table 4. — Guild structure on logged and unlogged bird study plots, 1976—79 



Guild 



No. 

 species 



1976 



Unlogged 



1977 



1978 



Density 



1979 



1976 



Logged 1 



1977 



1978 



1979 



Foraging guild 



Pairs per 100 acres 



Foliage foragers 



17 



121.0 



109.8 



121.2 



103.5 



103.5 



80.9 



73.6 



78.4 



Flycatchers 



2 



20.0 



20.0 



17.5 



16.2 



13.8 



23.1 



23.8 



29.3 



Timber drillers 



4 



2.5 



5.0 



2.5 



5.0 



5.6 



8.7 



7.5 



5.6 



Timber gleaners 



3 



17.5 



21.2 



27.5 



37.4 



18.7 



9.4 



8.8 



6.8 



Ground foragers 



9 



53.7 



56.2 



33.7 



41.2 



50.6 



74.3 



73.0 



82.3 



esting guild 





















Conifer tree 



6 



49.9 



37.5 



27.5 



23.7 



37.4 



24.2 



23.7 



23.7 



Conifer-deciduous tree 



6 



39.9 



41.2 



48.7 



43.6 



33.6 



34.2 



35.6 



34.2 



Bush and small tree 



7 



68.7 



66.1 



62.5 



67.4 



61.2 



74.8 



73.0 



91.6 



Primary cavity 



6 



5.0 



7.5 



5.0 



7.5 



10.0 



11.2 



11.2 



8.7 



Secondary cavity 



6 



35.0 



39.9 



42.5 



47.5 



31.8 



26.2 



15.6 



23.0 



Ground 



5 



22.4 



25.0 



21.2 



21.2 



22.4 



35.6 



34.3 



29.3 



1 Average of bird study plots 1 and 2. Logging was done in late autumn 1976. 



bush and small tree, primary cavity, secondary cavity, 

 and ground (table 4). Bush and small-tree nesters (seven 

 species) had the highest total density of all nesting 

 guilds in the unlogged forest. This nesting guild reacted 

 positively to logging. The American robin, Empidonax 

 flycatcher, and the chipping sparrow increased most in 

 postlogging environments; the warbling vireo was found 

 only on logged plots. 



Species that nest on the ground increased after 

 logging. Each of the ground-nesting species represented 

 in the study made up a greater proportion of the 

 breeding bird population in logged areas than in the 

 unlogged forest. The dark-eyed junco accounted for over 

 70 percent of the total density of the ground-nesting 

 guild in both the logged and unlogged forest. The rock 

 wren and winter wren were territorial only on logged 

 plots. 



The nesting guild with the largest numerical decrease 

 in response to logging was the secondary cavity nesters, 

 which dropped from almost 19 percent of the total 

 breeding bird density in the unlogged forest to about 10 

 percent in the logged forest. Most of the decrease 

 resulted from reductions in the abundance of the red- 

 breasted nuthatch, mountain chickadee, and brown 

 creeper. Although occurring in low densities, three 

 secondary cavity nesters (house wren, western bluebird, 

 and mountain bluebird) were found only on logged plots. 

 Of the six secondary-cavity nesting species found during 

 the study, three species— those that were most 

 abundant— responded negatively to logging, and three 

 species— those not represented in the unlogged forest- 

 responded positively to logging. 



SUMMARY AND CONCLUSIONS 



These data suggest that separate components of the 

 breeding bird community, including species populations 



and both foraging and nesting guilds, responded 

 differently to structural changes in the forest vegetation 

 caused by diameter-cut logging. Although there were 

 slight changes in total density and standing crop 

 biomass during the 3-year postlogging period, greater 

 changes occurred in the species composition of the 

 breeding bird population. Logging resulted in a positive 

 response by six species: 



Empidonax flycatcher 

 Townsend's solitaire 

 American robin 

 chipping sparrow 

 dark-eyed junco 

 Cassin's finch 

 Species responding negatively were: 

 mountain chickadee 

 red-breasted nuthatch 

 brown creeper 

 golden-crowned kinglet 

 Swainson's thrush 

 Townsend's warbler 

 western tanager 



Densities of eight species remained relatively stable on 

 both logged and unlogged plots: 



calliope hummingbird 

 hairy woodpecker 

 northern flicker 

 ruby-crowned kinglet 

 hermit thrush 

 solitary vireo 

 Nashville warbler 

 pine siskin 



10 



