Summary 1.There is an urgent need for climate change mitigation, of which the promotion of renewable energy, such as from wind farms, is an important component. Birds are expected to be sensitive to wind farms, although effects vary between sites and species. Using data from 12 upland wind farms in the UK, we examine whether there is reduced occurrence of breeding birds close to wind farm infrastructure (turbines, access tracks and overhead transmission lines). To our knowledge, this is the first such multi-site comparison examining wind farm effects on the distribution of breeding birds. 2. Bird distribution was assessed using regular surveys during the breeding season. We took a conservative analytical approach, with bird occurrence modelled as a function of habitat, before examining the additional effects of wind farm proximity. 3. Seven of the 12 species studied exhibited significantly lower frequencies of occurrence close to the turbines, after accounting for habitat variation, with equivocal evidence of turbine avoidance in a further two. No species were more likely to occur close to the turbines. There was no evidence that raptors altered flight height close to turbines. Turbines were avoided more strongly than tracks, whilst there was no evidence for consistent avoidance of overhead transmission lines connecting sites to the national grid. 4. Levels of turbine avoidance suggest breeding bird densities may be reduced within a 500-m buffer of the turbines by 15-53%, with buzzard Buteo buteo, hen harrier Circus cyaneus, golden plover Pluvialis apricaria, snipe Gallinago gallinago, curlew Numenius arquata and wheatear Oenanthe oenanthe most affected. 5. Despite being a correlative study, with potential for Type I error, we failed to detect any systematic bias in our likelihood of detecting significant effects. 6. Synthesis and applications. This provides the first evidence for consistent and significant effects of wind farms on a range of upland bird species, emphasizing the need for a strategic approach to ensure such development avoids areas with high densities of potentially vulnerable species. Our results reduce the uncertainty over the magnitude of such effects, and will improve future environmental impacts assessments.

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Masden, E. A., Haydon, D. T., Fox, A. D., Furness, R. W., Bullman, R., and Desholm, M. 2009. Barriers to movement: impacts of wind farms on migrating birds. – ICES Journal of Marine Science, 66: 746–753. Advances in technology and engineering are enhancing the contribution that wind power makes to renewable energy generation. Wind farms, both operational and in planning, can be expected to impact negatively on wildlife populations, particularly birds. We propose a novel approach to assess the impacts through the energetic costs of avoidance behaviour for a long-distance, migratory seaduck. Flight trajectories were recorded using surveillance radar at a Danish offshore wind farm with emphasis placed on the 200 000+ migrating common eiders that pass through the area annually. Minimum distance to wind farm and curvature of trajectories were compared pre- and post-construction. Additional costs of the avoidance response were estimated using an avian energetic model. The curvature of eider trajectories was greatest post-construction and within 500 m of the wind farm, with a median curvature significantly greater than pre-construction, suggesting that the birds adjusted their flight paths in the presence of the wind farm. Additional distance travelled as a consequence of the wind farm's presence was ca. 500 m and trivial compared with the total costs of a migration episode of 1400 km. However, construction of further wind farms along the migration route could have cumulative effects on the population, especially when considered in combination with other human actions.