Table 3 — Mean number of birds, by guilds, counted per census point within the four stand conditions at the Terrace 

 Hill study area and adjacent Coram Research Natural Area, Coram Experimental Forest, in 1989 and 1990 



Stand condition 



Number of Clear- Partial- Unlogged Natural Proba- 



Gulld^ species cut^ cut^ forest area bility^ 



Foraging 



Foliage forager 



23 



2.4* 



5.0^ 



4.5^ 



4.7B 



0.001 



Flycatcher 



5 



1.0* 



.3^ 



.1^ 



0^ 



.001 



Tree driller 



4 



.7 



.5 



.5 



.9 



.544 



Tree gleaner 



5 



.7* 



gAB 



I.3BC 



1.5c 



.003 



Ground forager 



14 



3.4* 



2.7*^ 



1.8^ 



I.4C 



.001 



Total 



51 













esting 















Conifer tree 



8 



1.0* 



2.6^ 



2.5B 



. 2.7B 



.001 



Conifer or broadleaf tree 



10 



1.4 



2.0 



1.6 



1.8 



1.000 



Bush or small tree 



10 



1.5 



1.6 



1.2 



1.0 



1.000 



Primary cavity 



5 



.9 



.6 



.6 



1.1 



.416 



Secondary cavity 



9 



1.6 



1.0 



1.3 



1.6 



1.000 



Ground 



9 



1.7* 



1.5*B 



QBC 



.3c 



.001 



Total 



51 













'Guilds adapted from Diem and Zeveloff (1980). 



^ree snags of all species and living paper birch left standing where possible. 



^Low probability values indicate significantly different means among stand conditions, Bonferroni adjusted to control for 

 experimentwise error; superscript letters group similar means for each guild (SPSS Inc. 1983). 



The same statistical analysis was used on guild 

 populations (table 3) and vegetation structure 

 (table 1). 



RESULTS 



The differences among the stand conditions in the 

 study area are described for bird populations and 

 vegetation components. 



Birds 



Tobalske observed 51 bird species during 

 censusing of the study area (appendix), but only 

 32 species were sufficiently abundant to include in 

 the statistical analysis (table 2). Pine siskins and 

 varied thrushes exhibited a significant interaction 

 effect between stand condition and year. Significant 

 differences in abundance occurred among stand 

 conditions for 10 species of birds. Tree swallows 

 were frequently detected in clearcuts, but virtually 

 absent elsewhere. Species that were less abundant 

 in clearcut or partial-cut areas were golden-crowned 

 kinglet, Swainson's thrush, varied thrush, and 

 Townsend's warbler. Conversely, dark-eyed juncos 

 and pine siskins were more abundant in harvested 

 habitat than elsewhere. Ruby-crowned kinglets and 

 fox sparrows were least abundant in clearcuts and 



in the CRNA, while chipping sparrows were com- 

 mon in all areas except the CRNA. 



Several other species did not exhibit significant 

 differences in abundance, but were less abundant 

 in clearcuts than elsewhere. These include brown 

 creeper, winter wren, and MacGillivray's warbler 

 (table 2). Likewise, species that were more abun- 

 dant in harvested stands but did not exhibit signifi- 

 cant differences include oHve-sided flycatcher, 

 Townsend's solitaire, and American robin. Interest- 

 ingly, robins were least abundant in the CRNA and 

 relatively common in the unlogged forest between 

 harvest units on the THSA. 



When species were grouped into foraging guilds, 

 following Diem and Zeveloff (1980), foliage foragers 

 were least abundant in clearcuts. Similarly, tree 

 gleaners were less abundant in clearcuts and partial 

 cuts than in unharvested areas. In contrast, fly- 

 catchers and ground foragers were more abundant 

 in harvested habitat, particularly clearcuts. Among 

 the nesting guilds, conifer tree nesters were least 

 abundant in clearcuts and ground nesters were 

 most abundant in cutover sites. Ground nesters 

 and ground foragers had a significant interaction 

 effect between stand conditions and years because 

 of a marked increase in abundance in harvested 

 areas in 1990. 



6 



