A synthetic analysis of post-construction displacement and attraction of marine birds at offshore wind energy installations

Changes in the distribution of marine birds in their at-sea foraging, resting, and migratory habitats are frequently observed following construction of offshore wind energy installations. However, the presence and strength of both displacement and attraction effects have been shown to vary widely among species and locations. An understanding of the underlying factors driving both occurrence and detection of distributional changes is required to inform wind farm design and develop best practices for environmental impact assessment, monitoring, and mitigation. Drawing from 39 publications and reports, we conducted a meta-analysis to assess the likelihood of detecting attraction or displacement of marine birds by wind energy infrastructure as well as the proportional change in use of the wind energy areas. We evaluated these outcomes as functions of wind farm characteristics, biological characteristics of birds, and the observation process. We found that the presence and strength of distributional change varied most strongly among taxa and seasons, followed by study design criteria and wind farm characteristics. Displacement and attraction effects were more frequently detected during the breeding season and in studies with a larger overall study area footprint relative to the size of the wind farm. Effects were also greater at wind farms further offshore and with lower turbine densities. Effects were significant and negative for loons, grebes, sea ducks, alcids, and gannets, and were mainly neutral or slightly positive for gulls, waterfowl, and cormorants. Less frequently-observed taxa such as fulmars and skuas had low frequency of significant displacement effects but large negative effect sizes, suggesting that displacement may be underestimated in these groups. Overall, we recommend that future monitoring studies clearly report underlying metrics (i.e., abundance and/or density) within defined study areas to allow for robust comparison among sites, species, and survey methodologies.