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Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biology

Supervisor

MacDougall-Shackleton, Scott A.

Abstract

Collisions with architectural glazing on buildings are a major anthropogenic source of bird mortality. Bird collisions can be prevented by applying bird safe design principles in building construction and renovations. Modifications to the appearance of glazing, such as using applications of visual markers on glass, can provide signals to alert birds to presence of an obstacle. To optimize visual markers for mitigating collisions with buildings, bird safe design must consider visual perception and behaviour of birds in the moments leading up to detection and avoidance. However, avian visual perception of glass, a unique and highly dynamic category of materials, remains poorly described in the literature. Defining relationships between avian and human visual perception, glazing and environmental variables such as lighting can support more effective real-world architectural applications of emerging technologies tested under controlled experimental conditions. This thesis examined environmental variables associated with the risk of bird collisions with glass on institutional campus buildings in London, Ontario, Canada as well as the efficacy of mitigation techniques using visual markers. To develop the methods, I reviewed assumptions and constraints associated with existing glass testing, such as experiments in the field and using flight arenas. I discussed approaches to improving the interpretation and generalisability of behavioural data. I then applied a combination of novel experimental and passive observational methods using building surveys, video recording and flight arenas to examine understudied aspects of collisions, yielding insights into effects of lighting conditions, flight kinematics, and glazing characteristics on outcomes of collisions. I found that collision risk increases with reflectivity of glass and decreases when surfaces use high contrast markings. When accounting for other factors, building façades with the most reflective glazing were associated with the greatest number of collisions. I found birds tested in flight experiments avoided markers applied on glass and transparent film. I gathered evidence that avoidance was affected by environmental factors such as lighting and the background. Translating knowledge from other academic disciplines and sectors, I provided recommendations for prioritizing further research, policy and program development to address social dimensions of this rapidly evolving challenge for the conservation of migratory birds.

Summary for Lay Audience

Millions of birds are killed by colliding with glazed surfaces, such as glass windows, on buildings in Canada each year. Bird collisions can be prevented by applying markers on glazed surfaces to signal the presence of an obstacle for birds to avoid. It is important that markers on glass are designed to be visible to birds. It is also important to understand the properties of glass that influence the risk of bird collisions, so that treatments of buildings can be prioritized where they will have the greatest conservation impact. In this thesis I reviewed how bird safe glass is tested as well as aspects of bird vision that may be relevant to understanding how birds detect and avoid collisions with glass. I examined architectural and landscape factors that predict the risk of collisions using surveys. Using remote video monitoring, I explored how birds behave in the moments leading up to and immediately following colliding with windows. I also tested how the visibility of markers to birds is affected by environmental conditions such as ambient light and the background behind the glass. This research provides evidence suggesting environmental variables can affect how effective markers on glass are at triggering avoidance by birds, which has implications for product testing and applications of products on buildings. I found that bird collisions occur more often at reflective windows, and that many birds that collide fly away immediately without leaving a trace. This suggests existing models of the total number of bird deaths caused by collisions may be an underestimate. I provided recommendations for future research to fill gaps in knowledge and to support development of programs and policies to mobilize solutions aimed at mitigating bird collisions with buildings.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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