Migratory Bird-Window Collisions: Understanding Physiology, Risk Factors, and Evaluating Mitigation Measures
DOI:
https://doi.org/10.58445/rars.2770Keywords:
Migratory birds, Bird-window collisions, Bird collisions, Urban ecology, UV-reflective markings, Conservation, EcologyAbstract
Migratory birds, totaling ~25% of all bird species, fill many ecological roles and are vital for global ecosystems. Urban areas interrupt migrant flyways, forcing birds to fly through unfamiliar environments. This paper reviews the reasons and risk factors behind bird-window collisions and evaluates mitigation strategies. Birds focus their visual attention on searching for foraging opportunities and predators instead of obstacle detection. This leads to an overload of their visual processing systems in the unfamiliar urban environment, causing 365 to 988 million annual window collisions in the US alone. Larger windows with higher reflectivity are dangerous as they are harder to detect and reflect more of the surrounding environment. Various window markings have been developed to allow birds to detect obstacles; the most effective are vertical stripes (94% risk reduction) and large, round dots (100% risk reduction). Most diurnal migrants can see UV light, which allows effective markings to reflect and absorb UV light, which is invisible to humans. The most effective markings are the 100% absorbent film (100% risk reduction) and any measures to increase the contrast between UV reflectance and absorbance across the same pane (71-91% risk reduction).
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