Breeding Bird Responses to Silvicultural Treatments in the Klamath Province of Oregon

Abstract

Silvicultural practices such as thinning are performed both for commodity production and to help achieve fuel reduction and biodiversity goals. Although there are several studies that have examined effects of clearcut harvest techniques on forest songbirds, few have examined the effects of thinning. We studied the response of songbirds to different silvicultural approaches to forest management. We experimentally manipulated three 80 to 110 y-old Douglas-fir stands to evaluate influences of commercial thinning and clearcut harvest silvicultural systems on populations of diurnal breeding birds in southwestern Oregon. We conducted 10 to 12 bird point count surveys in each stand between 1992 and 1994 (prior to treatment), and point count surveys of birds 6 times each year from 1998 through 1999 (subsequent to treatment). We found that relative abundance and species richness were highest in the uncut control plots, slightly lower in the thinned plots, and lowest in the clearcut plots. A species-by-species analysis of those species with sufficient data showed marked negative short-term impacts of clearcutting on 12 of 16 species, potentially moderate negative impacts of thinning on 9 of 16 species, as well as positive impacts of thinning on at least 3 species.