Response of Non-grassland Avian Guilds to Adjacent Herbaceous Field Buffers: Testing Hypotheses about Configuration of Targeted Conservation Practices in Agricultural Landscapes

Riffell, S. K., Monroe, A. P., Martin, J., Evans, K. O., Burger, L. W., & Smith, M. (2015). Response of Non-grassland Avian Guilds to Adjacent Herbaceous Field Buffers: Testing Hypotheses about Configuration of Targeted Conservation Practices in Agricultural Landscapes. Journal of Applied Ecology. British Ecological Society. 52(2), 300-309. DOI:10.1111/1365-2664.12389.

Abstract

1. In agricultural landscapes, forest habitat often consists of discrete patches of forest and linear woody corridors. These natural components provide habitat for some forest birds, and habitat quality may be influenced by in-field practices applied outside the forest patch. For example, specific juxtapositions of herbaceous field buffers adjacent to forest habitat could increase avian diversity contributions of existing forest without creation of additional forest habitat. Our prediction was that herbaceous field buffers would increase bird richness in adjacent forest, and we evaluated four potential mechanisms. 2. We used bird count data from a conservation buffer monitoring program and hierarchical community models to estimate species richness of forest generalist, forest interior and shrubland (edge) species near forest edges with and without adjacent herbaceous field buffers. We accounted for heterogeneity in detection probabilities and forest cover in the surrounding landscape when estimating species- and community-level responses. 3. Consistent with the drift fence hypothesis, adjacent herbaceous buffers were associated with a modest increase in richness of forest interior birds in woody corridors, but not in forest blocks. Consistent with resource complementation, adjacent herbaceous buffers were associated with modest increases in richness of shrubland (edge) birds in both woody corridors and forest blocks. 4. Overall species and guilds, adjacent buffers consistently associated with greater abundance (e.g., 30 of 39 species), but these increases were also relatively small and highly variable (i.e., overlapping 95% credible intervals). Consistent with existing research, effects of adjacent herbaceous buffers are likely real, but neither pervasive nor strong. 5. Synthesis and applications. Conservation practices targeted to grassland species (like those in Europe and North America) often produce measurable conservation benefits for target species. However, biodiversity return for investment would be further increased if targeted practices could be deployed in ways that also produce benefits for non-target species in adjacent habitats. Our results suggest that additional benefits for non-target species using adjacent forest habitat are likely modest, so conservation planning should focus on target species and avoidance of potential negative impacts on target species.