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

Authors: Sirena Lao, Abigail W. Anderson, Robert B. Blair, Joanna W. Eckles, Reed J. Turner, and Scott R. Loss

Year: 2023

Publication: Ornithological Applications

Publication Link:

Keywords: anthropogenic mortality, bird–building collisions, bird–window collisions, human-caused mortality, migration, nocturnal migrants, urban, weather

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.

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