Marine birds: vision-based wind turbine collision mitigation.
In this paper, marine birds (38 species from Anseriformes (ducks and geese); Podicipediformes (grebes); Charadriiformes (gulls and auks); Suliformes (gannets and cormorants); Gaviiformes (divers/loons); Procellariiformes (shearwaters, petrels and storm petrels) and Accipitriformes (eagles)) were ranked according to two possible outcomes of their interactions with wind turbines: (1) a direct effect on individual birds through collisions and (2) the indirect effects of disturbance and/or displacement from key habitats caused by the presence of wind turbines. Key aspects of the vision, behaviour and ecology of marine birds which contributed to their collision risk under a range of natural viewing conditions were studied. The information was then used to give insights into the requirements and key elements for the design of vision based mitigation measures aimed at reducing the collision of marine birds with offshore wind farms. It was shown that there was a 70% reduction in annual turbine-blade collision mortality rate in 19 bird species at a terrestrial location in Scotland, UK, indicating a justifiable ecological basis for increasing the internal visual contrast of turbines through blade marking to benefit seabirds. A mitigation measure is proposed which is neither site or species specific and can be employed generally in marine situations. The principle aim of the mitigation measure is to increase the conspicuousness of wind turbines across a wide range of natural viewing conditions, such that a turbine can be detected by an approaching bird sufficiently early to allow change in their flight path and avoid collision.