Comparative Analysis of Bird Collision Prevention Patterned Samples: Avoidance Performance Under Transparent and Reflective Glass Conditions in Flight Tunnel Tests

The transparency and reflectivity of glass are primary factors contributing to bird collisions, as they prevent birds from recognizing glass surfaces as obstacles. However, the effectiveness of bird collision prevention products is primarily evaluated through transparency-based tunnel tests, which do not adequately account for the reflective conditions commonly found on building glass. We developed an indoor flight tunnel system that simulated sky reflections on glass surfaces and compared avoidance responses to three bird collision prevention patterned samples under both transparent and reflective conditions. A total of 507 wild small passerines were tested, each undergoing a single flight trial. All three patterned samples showed lower avoidance rates under reflective than transparent conditions, but the overall effect of test condition on avoidance was not statistically significant. The frequency of invalid flights increased significantly under reflective conditions. These findings suggest that avoidance responses to bird collision prevention products may vary between transparent and reflective test configurations, although the magnitude of this difference remains uncertain. Incorporating reflective conditions alongside conventional transparency-based tests may therefore provide complementary information for evaluating product performance under different optical conditions.