Bird–building collisions increase with weather conditions that favor nocturnal migration and with inclement and changing weather

Abstract

ABSTRACT Collisions with building windows are a top bird mortality source, but few studies have evaluated how bird–window collisions are influenced by weather. By monitoring collisions daily at 21 buildings in Minneapolis, Minnesota, over 4 migration seasons, we show that weather influences numbers of window collisions of nocturnal migrants in spring and fall, indicating that collisions may be forecastable based on weather conditions. Collisions increased with weather favoring migration, such as consecutive nights of south wind in spring and even short periods of north wind in fall. We also found evidence that spring and fall collisions increase with weather changes that impede migration, such as changes from fair conditions and tailwinds early in the night to headwinds near sunrise. Our study suggests complex weather effects never before considered in the context of bird collisions, including possible time lag effects of conditions 2–3 nights before collisions occur, effects of multi-day sequences of conditions, and interactions between conditions at different times of night. More research is needed to determine if the accuracy of weather-based collision prediction systems improves by integrating such nuances and to clarify mechanisms through which these complex effects operate, such as influences of weather on migration intensity and collision avoidance behavior. Weather-based forecasts may allow refinement of collision mitigation approaches (e.g., reducing building lighting on certain nights or using temporary glass coverings or treatments). However, because challenges remain to communicating such temporally targeted actions and implementing them in a timely manner, other bird-friendly practices (e.g., season-long lighting reduction and permanent glass treatments) should continue to be prioritized. How to Cite Lao, S., A. W. Anderson, R. B. Blair, J. W. Eckles, R. J. Turner, and S. R. Loss (2022). Bird–building collisions increase with weather conditions that favor nocturnal migration and with inclement and changing weather. Ornithological Applications 125:duac045. LAY SUMMARY Collisions with windows are a top bird mortality source. Information about weather effects on bird–window collisions could help predict collisions. In Minneapolis, Minnesota, we studied 21 buildings over 4 migrations to evaluate how weather affects collisions for birds that migrate at night. Spring and fall collisions increased with weather favoring migration, like tailwinds. We also found evidence that collisions increase with weather changes that cause migrating birds to be grounded, like changes from tailwinds to headwinds during the night. We also found more-nuanced weather effects, including possible effects of weather 2–3 nights before collisions occur, and of multi-day sequences of conditions. Weather forecasts may help target temporary measures to reduce bird–window collisions, but relationships are complex, and recommendations to building managers could be difficult to implement on short notice. More-permanent practices, like turning off nighttime lights throughout migration and using bird-friendly building design and glass treatments, should therefore be prioritized. RESUMEN Las colisiones con las ventanas de los edificios son una de las principales fuentes de mortalidad de las aves, pero pocos estudios han evaluado cómo las colisiones entre las ventanas y las aves están influenciadas por las condiciones del tiempo. Al monitorear las colisiones diariamente en 21 edificios en Minneapolis, Minnesota, durante 4 temporadas de migración, mostramos que el tiempo influye en el número de colisiones con ventanas de los migrantes nocturnos en primavera y otoño, lo que indica que las colisiones pueden ser predecibles en función de las condiciones del tiempo. Las colisiones aumentaron con el tiempo que favorecía la migración, como noches consecutivas de viento del sur en primavera e incluso períodos cortos de viento del norte en otoño. También encontramos evidencia de que las colisiones de primavera y otoño aumentan con los cambios del tiempo que impiden la migración, como cambios de las condiciones favorables y vientos de cola temprano en la noche a vientos en contra cerca del amanecer. Nuestro estudio sugiere la ocurrencia de efectos complejos del tiempo, nunca antes considerados en el contexto de las colisiones de aves, incluidos los posibles efectos diferidos de las condiciones de 2 a 3 noches antes de que ocurran las colisiones, los efectos de las secuencias de condiciones de varios días y las interacciones entre las condiciones en diferentes momentos de la noche. Se necesita más investigación para determinar si la precisión de los sistemas de predicción de colisiones basados en el tiempo mejora al integrar dichos matices y para aclarar los mecanismos a través de los cuales operan estos efectos complejos, como las influencias del tiempo en la intensidad de la migración y en el comportamiento para evitar las colisiones. Los pronósticos meteorológicos pueden permitir refinar los enfoques de mitigación de colisiones (e.g., reducir la iluminación de los edificios en ciertas noches o usar cubiertas o tratamientos temporales de los vidrios). Sin embargo, debido a que persisten los desafíos para comunicar dichas acciones temporales dirigidas y para implementarlas de manera oportuna, se debe continuar priorizando otras prácticas amigables con las aves (e.g., reducción de la iluminación durante toda la temporada y tratamientos permanentes de los vidrios).