Abstract
The rapid global expansion of wind farms poses potential impacts to bird populations through collision mortality, movement barriers, and habitat displacement. Avoidance, the tendency of birds to maintain distance from wind turbines, plays a critical role in assessing the impacts of wind farms on avian species. In this study, we used marine surveillance radar to monitor avian responses to the Formosa 1 Offshore Wind Farm in the eastern Taiwan Strait. We assessed macro-avoidance by analyzing flight track directions and comparing bird density within and outside the wind farm area. Our findings suggested macro-avoidance rates ranging from 0.33 to 0.69 between March and May, and from 0.83 to 0.89 between July and January. The lower avoidance rates observed in spring could be partially attributed to the high proportion of egrets during this period, as these birds generally exhibited little macro-avoidance behavior in terrestrial observations. Discrepancies between the two methods used to assess avoidance were identified, with radar signal interference from wind turbines likely leading to an overestimation of avoidance rates in the track-density method. Low avoidance between March and May suggested a potentially higher collision risk during spring migration. Further investigation into finer-scale avoidance behaviors and collision rates is essential to understand the ecological impact of wind energy development.