• Bird collisions with offshore wind structures are difficult to detect. Assessing collision rates at other human structures, like tall buildings and land-based wind facilities, is typically done by repeatedly counting carcasses underneath the structures. This is not possible in the ocean as bird carcasses sink, float away, or are scavenged. Thus, direct observations or remote monitoring technologies such as cameras and thermal sensors must be used. • Monitoring bird collisions in the offshore environment (whether via direct visual observation or remote monitoring) presents significant logistical and technical difficulties, particularly for smaller-bodied birds and species that migrate at night. Thus, while there are several key studies that have used a combination of human observers, camera systems, and radar to count collisions at offshore wind facilities, this type of data collection at scale is expensive and technically demanding. • Prior to construction, collision risk models (CRMs) are used during the permitting process to estimate the likelihood of bird collisions at a given wind facility site. Such models use wind facility characteristics (e.g., turbine height) and species-specific parameters (e.g., distribution, avoidance behavior, morphology) to predict potential collision rates. However, there are limited data available to validate predictions from these models, and more field research is needed to improve confidence in model outputs. In the face of limited data, however, CRMs can help inform risk assessments and possible mitigation strategies. For more detailed information and scientific citations, please see the full FAQ document linked below.

• Based on the accumulated available data, bird collisions with offshore wind turbines are thought to be rare events that are also infrequent in comparison to other sources of human-caused bird mortality. • Collection of carcasses from the ground is commonly used to assess bird collisions with land-based infrastructure and vehicles. This is largely not possible at offshore wind turbines. Visual observations by human observers in real time must be supplemented or replaced with remote monitoring technologies to collect data on collisions offshore and inform mortality estimates and risk. • Facility siting and design, environmental conditions (e.g., nighttime, inclement weather), the species present, and the mitigation measures in use will all impact the frequency of bird collisions at a given facility, so continued advancements in research and monitoring technologies will help refine bird collision estimates, reduce uncertainties, and inform management decisions. For more detailed information and scientific citations, please see the full FAQ document linked below.