Bird window collisions happen throughout the year, taking place in rural and urban habitats with deaths documented for many groups of birds. Birds are unable to perceive glass itself as a barrier, and instead are attracted to the reflections on the surface or suitable habitat on the other side. Window treatments have been developed to reduce collisions and while some individual studies test a subset of solutions, there has not been a thorough comparison of solutions to inform managers and citizens. The goal of this study is to estimate the effect of treatments and systematically compare and rank different window treatments based on effectiveness. To address this goal we conducted searches for terms related to bird-window collisions in Google Scholar and Web of Science following PRISMA guidelines. From all papers found, we selected only the ones that included treatments applied directly to windows and control data. From these eight studies we collected collisions rates then conducted a meta-analysis in the metafor package in R. We used a random effects model to estimate the overall average effect size and rank individual solutions. We used a mixed effects model moderated by treatment groups to compare solidly colored, ultraviolet absorbing and/or reflecting.
Results/Conclusions
The random effects model identified a commercially available one-way glass called CollidEscape and alternating vertical strips of ultraviolet absorbing and reflecting as the best treatments for reduction of collisions. The mixed effects model supported the same treatments as most effective. In addition, the mixed effects model identified the combination of ultraviolet absorbing and reflecting as the best group, with ultraviolet reflecting as the second best collision reduction choice. The overall effect was that the treatments reduced collision rates by 80% compared to clear glass. The solutions found to be effective are feasible for application anywhere from homes to businesses. Future action needs to focus on scientist and community involvement to collect information on buildings with greater risk. Once identified, effective solutions can be implemented. This research helps inform residents, builders, and managers about effective solutions to consider while making decisions to suit their specific needs.