Evaluating bird-window collision patterns, species vulnerability, and a mitigation approach

Bird populations are declining at an unprecedented rate worldwide. In North America, 57% of all bird species have experienced population declines in the last 50 years. Collisions with building windows are one of the top avian mortality sources contributing to these declines, and in North America alone, potentially over one billion birds die annually from window collisions. Despite the importance of window collisions to global bird conservation, many substantial gaps remain in the window collision literature. These gaps include a lack of rigorous field testing of products designed to mitigate collisions, and a scarcity of studies evaluating collision patterns at broad spatiotemporal scales. To address these knowledge gaps, we conducted two separate studies. Firstly, we conducted a before-after control-impact (BACI) study of the effectiveness of a mitigation product at the Oklahoma State University campus—specifically, monitoring of window collisions both before and after a treatment of Feather Friendly® 5x5 cm white dot markers. Secondly, we analyzed continental-scale taxonomic and spatiotemporal patterns of window collisions using bird band recovery data from the North American Bird Banding Program (NABBP) dataset and estimated vulnerability of individual species to window collisions. In relation to the first study, we found a 67.2-71.6% reduction in collisions at glass façades treated with the window markers, in contrast to a 15.7% increase in collisions at untreated façades during the same period. This result emphasizes the promise of window markers as a collision mitigation technique and offers a framework for a rigorous study design that can be used for future studies on similar products. For the second study, we found that the NABBP dataset included collision records for 298 species and 51 families, encompassing the entire continental United States and southern Canada. Many of the most vulnerable species in the dataset were from families currently underrepresented in the window collision literature, including hawks, falcons, owls, and finches. This underscores the need for demographic modeling studies to determine if species in these families are experiencing population-level effects from window collisions. Collectively, we offer valuable insights into the effectiveness of collision mitigation products and broad-scale species vulnerability to window collisions.