Breeding bird response to riparian forest harvest and harvest equipment

We examined response of breeding bird communities to timber harvest in riparian areas using two harvest techniques (full tree harvest and cut-to-length (CTL)) along first to third order streams in northern Minnesota, USA. Although many studies have quantified bird response to riparian buffer harvest, we are unaware of any study that examined the response of breeding birds to riparian forest harvest using different cutting practices. We compared community composition, total abundance and species richness, as well as abundance of six individual species on plots within four treatments (three plots/treatment) completed within 30 m on both sides of the stream. Treatments in the riparian area (30 m on both sides of the stream) were: (1) riparian control (no harvest); (2) reduction of basal area to an average of 7-10 m²/ha with full tree harvest system; (3) reduction of basal area to an average of 7-10 m²/ha with CTL harvest system; and (4) control (no harvest in riparian area or upland). For treatments 1, 2, and 3, adjacent upland forests on the plots were clearcut. Bird surveys were completed 1 year prior to, and 3 years after harvest and revealed a significant response of the bird community to timber harvest in the riparian area. Bird communities were most affected by tree removal with both harvest methods, but harvest type also affected bird communities. Early-successional species, e.g. song sparrow (Melospiza melodia), white-throated sparrow (Zonotrichia albicollis), mourning warbler (Oporornis philadelphia), and chestnut-sided warbler (Dendroica pensylvanica) were associated with harvested plots, whereas forest species, e.g. scarlet tanager (Piranga olivacea) and black-throated green warbler (Dendroica virens) were associated with riparian control and control plots. Of six individual species tested for response to riparian harvest treatment over time, only the ovenbird (Seiurus aurocapillus) showed a significant time by treatment interaction. Ovenbird numbers decreased in both the CTL and full tree harvest plots through 2000, when no individuals were observed. Two other forest-dependent species, black-throated green warbler and hermit thrush (Catharus guttatus), showed similar responses to treatment as the ovenbird. The winter wren (Troglodytes troglodytes) responded positively to the greater amount of slash that was left on-plot with the CTL harvest system. However, with the exception of the winter wren, we found that bird species and communities did not differ in their response to harvest system.