Behaviour 2019
Bird-Window Collisions and Reflection as a Risk Factor
Lauren C. Emerson1, Robin G. Thady1, John P. Swaddle1, 2. 1Biology Department, William & Mary, Williamsburg, VA, United States; 2Institute for Integrative Conservation, William & Mary, Williamsburg, VA, United States

Bird-window collisions account for millions of bird deaths annually in the United States. Despite many correlative studies citing the potential influence of reflective glass on daytime collision risk, few studies have explicitly tested this hypothesis. We aimed to determine whether reflection from a window influences daytime collision risk by manipulating the lighting conditions on exterior and interior window surfaces. We conducted this research within a flight tunnel in which domesticated zebra finches (Taeniopygia guttata) flew towards a window structure situated behind a mist-net. We assessed collision risk and flight velocity through 3D videography. We predicted that risk of collision and flight velocity would be greater when windows were manipulated to reflect more light. We found no support for our predictions. In contrast, we found that collision risk decreased in the presence of a reflection during bright, midday exterior lighting conditions. We suggest that the influence of window reflection on daytime window collisions is more complex than assumed and might involve previously unaccounted properties of light such as wavelength.