Breeding bird response to varying amounts of basal area retention in riparian buffers

We examined response of breeding bird communities to forest harvest that removed varying amounts of tree basal area from riparian buffers on a 2- to 4-m-wide stream in northern Minnesota, USA. We compared bird species and communities in 30-m-wide riparian buffers along the stream. Buffers were established within plots in which upland forests were clear-cut (basal area 2 m²/ha) according to standard local forest management practice. Buffers had 4 treatments (3 plots/treatment): (1) no harvest (riparian control); (2) reduction of basal area to an average of 7-10 m²/ha; (3) reduction of basal area to an average of 2 m²/ha (defined as a clear-cut); and (4) control (no harvest in either riparian buffer or adjacent upland). Bird surveys were conducted 1 year prior to harvest and for 4 years after harvest.Results revealed a significant response of the bird community to varying amounts of tree basal area retention in the riparian area. Univariate (analysis of variance) and multivariate (principal response curves [PRC]) analyses showed that in the first year after harvest, bird community composition in the riparian buffers changed in all 3 treatments relative to the control plots, and continued to diverge over time. More species and individuals, primarily those species associated with edge or early-successional habitats, colonized the harvested riparian buffers after treatment. In contrast, the number of birds and species that inhabit interior forests declined in the riparian buffers. Results suggest that any amount of harvest in riparian buffers next to clear-cut upland forest will affect breeding bird communities along small headwater streams. Because individual bird species are differentially affected by riparian forest harvest, management should consider the desired future condition of the forest and choose a harvest prescription to benefit the desired avifauna community.