(table 2). Although there were few snag trees remaining 

 immediately after logging, the slash-burning treatment 

 conducted weeks later killed or damaged many of the 

 residual unmerchantable trees. The highest woodpecker 

 densities recorded during the study were on logged plots 

 the year following logging and slash burning. Some, but 

 not all, of the territorial woodpeckers nested directly on 

 the logged plots. Hagar (1960) also noted increased 

 woodpecker densities on recently logged areas in north- 

 western California. 



The presence of relatively high numbers of wood- 

 peckers on logged plots resulted in a number of holes 

 being excavated in dead or weakened residual trees 

 which, in turn, provided nest sites for the western blue- 

 bird, mountain bluebird, and house wren. Frequent and 

 prolonged combative encounters between wrens and 

 bluebirds near excavated or natural tree cavities sug- 

 gested competition for nest sites on logged plots. 

 Recently dead and trunk-blackened trees, particularly 

 Douglas-fir, were used heavily by the black-backed wood- 

 pecker for feeding and, in two cases, for nest sites. The 

 pileated woodpecker, an uncommon bird in the area, was 

 rarely observed on logged plots. 



Table 3 summarizes responses of common bird species 

 to tree removal treatments in coniferous forests of the 

 western United States. The notations in table 3 repre- 

 sent a liberal interpretation of published information 

 that was often originally presented in tabular form. 

 Source material is arrayed left to right roughly on the 

 basis of the degree of tree removal with the most severe 

 treatment on the extreme right. Twelve species tended 

 to react positively to most tree removal treatments. 

 These were: 



olive-sided flycatcher 

 rock wren 

 house wren 

 winter wren 

 western bluebird 

 mountain bluebird 

 American robin 

 rufous-sided towhee 

 chipping sparrow 

 fox sparrow 

 dark-eyed junco 

 Cassin's finch 



The wrens, bluebirds, and sparrows were consistent in 

 showing an upward numerical response. Nine species 

 responded negatively to most treatments. These were: 



western flycatcher 

 mountain chickadee 

 red-breasted nuthatch 

 pygmy nuthatch 

 brown creeper 

 golden-crowned kinglet 

 hermit thrush 

 Townsend's warbler 

 red-faced warbler 



Responses of other species listed in table 3 are less 

 clear. The hairy woodpecker, northern flicker, Town- 

 send's solitaire, yellow-rumped warbler, and pine siskin 

 either responded minimally or were inconsistent in their 

 response to treatment except for the highest levels of 

 tree removal. In general, the numerical response of many 

 species depends on the degree of tree removal; compare, 

 for example, species responses listed from Kilgore (1971) 

 with those from the clearcut treatment of Szaro and 

 Balda (1979). 



Guild Responses 



Birds may be placed in categories, or guilds, based on 

 foraging behavior or the type of substrate in which 

 foraging occurs (Diem and Zeveloff 1980; Root 1967). 

 The 35 breeding bird species listed in table 2 were 

 divided into five foraging guilds: foliage foragers, 

 flycatchers, timber drillers, timber gleaners, and ground 

 foragers (table 4). 



Birds that forage by searching foliage (foliage foragers) 

 formed the largest single category, and these, along with 

 the ground foragers, made up the largest proportion of 

 all foraging categories. Among the foliage foragers, 

 insectivorous species predominated. The ground-foraging 

 forms, which included chipping sparrows, dark-eyed 

 juncos, and Cassin's finches, were largely granivorous. 

 The flycatchers were the olive-sided flycatcher and the 

 Empidonax flycatcher. Four species— the yellow-bellied 

 sapsucker, hairy woodpecker, white-headed woodpecker, 

 and black-backed woodpecker— were classified as timber 

 drillers, and three species— the red-breasted nuthatch, 

 white-breasted nuthatch, and brown creeper— were 

 grouped as timber gleaners. 



Foliage foragers (17 species) had the highest total 

 density of all foraging guilds in the unlogged forest 

 (table 4). The three species with the highest densities 

 were the Swainson's thrush, western tanager, and 

 mountain chickadee. The foliage foraging guild declined 

 after logging. One species, the golden-crowned kinglet, 

 was territorial only on unlogged plots. Three foliage 

 foragers (house wren, warbling vireo, and black-headed 

 grosbeak) were territorial only on logged plots. 



Birds that forage by gleaning the surface of bark 

 (timber gleaners) declined the most after logging; guild 

 density in the third year following logging was only 

 about one-third that of prelogging density. The 

 numerical decrease was most severe for the brown 

 creeper and red-breasted nuthatch. Other foraging 

 guilds— the ground foragers and flycatchers— were more 

 numerous on logged plots. Birds that feed on the ground 

 were, by a slight margin, the most abundant foraging 

 guild on logged plots 3 years after logging. Each of the 

 nine species in the ground-foraging guild was 

 proportionately more abundant in logged environments 

 than in the unlogged forest. The timber-drilling guild 

 maintained relatively stable total densities on both 

 logged and unlogged plots. 



Categorizing birds on the basis of the substrate in 

 which nesting occurs provides additional information 

 about the breeding bird community. Six nesting guilds 

 were recognized: conifer tree, conifer-deciduous tree, 



8 



