Birds and small wind turbines: Basic information for collision risk management

<p> Abstract: Assessing the risk of collisions between wind turbines and passing birds is an important issue in bird conservation. Unlike their larger counterparts, small wind turbines do not need to undergo environmental impact assessments (EIAs) in Japan. Being subject to fewer restrictions, they can be constructed where large turbines may be forbidden. Small wind turbines are increasingly being installed in Japan, and the endangered white-tailed eagle (Haliaeetus albicilla) is known to collide with them. As EIA methodologies are geared toward large turbines, they may be unsuitable for small turbines. However, there has been no formal assessment of the risks of bird collisions with small wind turbines in Japan. In the absence of systematic collision data, we used bird flight frequency near small turbines as a proxy for collision frequency. We recorded birds flying within 10 or 20 m of small wind turbines during point-count surveys and then ran generalized linear models with the number of flights as the objective variable and weather and surrounding land cover as explanatory variables. Slaty-backed gulls approached turbines most often (537 observations), followed by black-tailed gulls (536), large-billed crows (459), and Oriental greenfinch (292). Two rare species, the white-tailed eagle and Steller's sea eagle, were recorded 29 and 2 times, respectively. The slaty-backed gull is also the species most often observed colliding with large wind turbines; small turbines seem to also be approached by smaller grassland species. The effects of wind speed varied, with three species flying less during high winds and white-tailed eagles flying more. All species regularly approached within 10 m during their breeding seasons, indicating that these are periods of especially high collision risk. Given the small number of survey sites in our study, our results provide only preliminary insight into turbine placement and bird collision risk management; more research is needed.</p>