College of Science and Mathematics

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Cal Poly Researchers Map Bird Deaths from Window Collisions

Common yellowthroat
Photo // Dan Pancamo (Flickr: Common Yellowthroat) [CC BY-SA 2.0], via Wikimedia Commons

Nearly 1 billion birds die annually in North America after colliding with windows in buildings. Cal Poly students joined an international team of researchers to determine how different buildings and landscaping contribute to those deaths. The researchers found that large buildings with a lot of windows caused the most bird deaths, especially when surrounded by more grass and landscaping.

Researchers monitored almost 300 buildings for bird-window collisions at 40 college and university campuses in North America, including Cal Poly. Students in biology Professor Clinton Francis’ Principles of Conservation Biology class contributed to the data collection by monitoring collisions on Cal Poly’s campus.

“This large collaborative project was a really fun way to get students involved in real research,” Francis said. “Students were so excited to know that their efforts were going towards a large project that could really help bird conservation and they all did a great job with the field work. Embedding this research project within a course was a fun experiment for me too and one that paid off for both the students and science.”

These patterns may be caused by bird migration patterns. Migrating birds select their habitat based on geography, weather and social cues such as hearing calls of the same species. Birds that are used to living in the forest might be more likely to settle near large buildings in rural rather than urban settings because of these factors.

In addition, because urban environments give off so much light, birds might avoid them all together and so decrease the number of window collisions with large buildings in these areas. Another possible explanation is that birds living in urban environments have learned about windows and change their behavior to avoid collisions.

Birds’ daily behavior may also play a role. In the mornings, birds fly above tree height looking for good habitat. This flight pattern could explain why more birds collide with windows in low-rise and tall buildings than in single-story buildings.

Researchers plan to explore these possibilities in the future.

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