RESULTS: BREEDENTG BIRDS 



Little change occurred in total breeding bird popula- 

 tions as a result of the selection-cut logging (table 1). 

 Prelogging and postlogging estimates of total density, 

 standing crop biomass, and species diversity were similar. 

 All but one of the 28 breeding bird species listed in table 1 

 were found in both logged and unlogged environments. 

 The olive-sided flycatcher, warbling vireo, and varied 

 thrush were territorial birds only on the logged plot. 

 Numbers of individual species fluctuated widely from year 

 to year on both logged and unlogged plots. Annual fluc- 

 tuations in total bird populations were less extreme. 



The most abundant species in the unlogged forest — 

 each making up more than 5 percent of the breeding bird 

 community and collectively accounting for 77 percent — 

 were: 



Empidonax flycatcher 

 mountain chickadee 

 red-breasted nuthatch 

 Sweiinson's thrush 

 yellow-rumped warbler 

 MacGillivray's warbler 

 western tanager 

 chipping sparrow 

 dark-eyed junco 



In the logged forest, species each making up more than 

 5 percent of the breeding bird community and collectively 

 accounting for 65 percent were: 



Empidonax flycatcher 

 Swainson's thrush 

 yellow-rumped warbler 

 Townsend's warbler 

 MacGillivray's warbler 

 western tanager 

 chipping sparrow 

 dark-eyed junco 



Among these eight most abundant species, seven were 

 common to both logged and unlogged plots. 



Several species responded either positively or nega- 

 tively to the selection-cut logging (table 1). Species with 

 significant upward patterns of numerical response in- 

 cluded the olive-sided flycatcher, Swainson's thrush, 

 yellow-rumped warbler, and chipping sparrow. Of these, 

 only the olive-sided flycatcher nested in the overstory; the 

 others nested either in the midstory or understory layers 

 of vegetation. Olive-sided flycatchers, chipping sparrows, 

 and yellow-rumped warblers have shown positive numeri- 

 cal responses to tree removal treatments elsewhere in 

 western coniferous forests (Medin 1985). 



Each of the four species showing a positive response to 

 the logging treatment is classified as having a medium 

 versatility rating with respect to reproduction and feeding 

 orientation, and each is characteristic of shrub-forest 

 ecotonal habitats (Thomas 1979). All but the yellow- 

 rumped warbler are oriented to a variety of successional 

 habitats (Thomas 1979). Each is a common summer resi- 

 dent throughout the coniferous forests of central Idaho 

 (Burieigh 1972). 



The warbling vireo, a bird of deciduous shrub and tree 

 habitats (Burleigh 1972), was found as a breeder only on 

 the logged plot. More tall shrubs, particularly willows 

 and alders, were present on the moist sites of the logged 

 watershed. Hermit thrushes, common on the unlogged 

 plot, were not ofl;en seen on the logged plot. 



The red-breasted nuthatch and the brown creeper re- 

 sponded negatively to the timber harvest (table 1). Both 

 are bark gleaners typically found in late-successional 

 forest habitats (Thomas 1979), and both are secondary 

 cavity nesters. The brown creeper nests under loose bark 

 and is often associated with mature stands of ponderosa 

 pine. The red-breasted nuthatch is a bird of coniferous or 

 mixed coniferous-deciduous forests and may excavate its 

 own nesting cavity if a natural cavity is not available 

 (Burleigh 1972). Both species have low versatility ratings 

 (Thomas 1979). Others (summarized in Medin 1985) 

 have reported similar negative numerical responses by 

 the brown creeper £ind red-breasted nuthatch to tree 

 removal treatments. The western tanager and 

 Townsend's solitaire showed weaker patterns of decline 

 after timber harvest. 



The hairy woodpecker and northern flicker maintained 

 relatively stable densities on both the logged and 

 unlogged plots. 



Birds may be placed in categories, or guilds, to organize 

 and compare functional relationships within the commu- 

 nity. Guilds were defined by Root (1967) as groups of 

 species that use similar environmental resources in simi- 

 lar ways. The 28 breeding bird species listed in table 1 

 were organized into feeding and nesting guilds based on 

 their foraging behavior and the substrates used for nest- 

 ing (table 3). 



Birds that feed by searching foliage (foliage feeders and 

 gleaners) formed the largest single feeding guild. These, 

 along with the ground gleaners, made up the largest pro- 

 portion of all feeding categories. Among the foliage feed- 

 ers, insectivorous species predominated. The ground 

 gleaners, including chipping sparrows, dark-eyed juncos, 

 and Cassin's finches, were largely granivorous. Two spe- 

 cies — the olive-sided flycatcher and the Empidonax fly- 

 catcher — were classified as aerial-sally feeders. And two 

 species — the red-breasted nuthatch and the brown 

 creeper — were grouped as timber gleaners. The hairy 

 woodpecker was the only timber driller represented. 



Foliage feeders, the guild containing the most species, 

 had the highest total density among all feeding or nesting 

 guilds in both the logged and unlogged forest. The 

 Swainson's thrush, western tanager, MacGillivray's war- 

 bler, mountain chickadee, and yellow-rumped warbler 

 were the most abundant members of the guild. Of these, 

 only the western tanager declined after logging. Among 

 all feeding guilds, only the timber gleaners were adversely 

 affected by the logging treatment. The negative response 

 of this guild reflects the significant reductions in density 

 of the brown creeper and red-breasted nuthatch, both 

 timber gleaners. Foliage feeders, aerial-sally feeders, and 

 timber drillers were about equally abundant before and 

 after logging. Ground gleaners were slightly more abun- 

 dant in the logged forest. 



6 



