By Brendon Samuels
Whether you’re a human driving a car or a bird migrating across a continent, navigating safely at high speed requires awareness of visual signals in the environment. Fortunately for humans, signals along roads and highways are designed to be highly conspicuous so drivers can easily spot them. For example, road signs are large, brightly coloured and often made with fluorescent materials. Roads and vehicles are designed based on how humans see and use them.
Now imagine what driving would be like if roads suddenly didn’t have signs or if drivers couldn’t see them. In this scenario, suppose you make the same trip every day, from your home to the office. With enough practice you become familiar with this route and could possibly manage without signage. You learn where the local hazards are – the potholes, the crosswalks, the bends in the road – so you can navigate around them. But if you get in your car and take an unfamiliar route through a different neighbourhood or city, without visual signals to alert you to hazards ahead, that journey would be incredibly dangerous.
To a bird, migrating through a city must be like driving a car without a frame or airbags on an alien highway lacking signage and where most of the gas and rest stations are closed for business. Even so, bird migration is far more complicated and dangerous than driving. Humans have inserted invisible glass obstacles right in the middle of where birds fly and created a never-ending “car-chase” by free-roaming cats and other introduced predators. Like driving in a new neighbourhood, when migratory birds reach stopover sites, they have less experience in those specific environments than resident birds to know where the hazards are. This could be a reason why migratory birds are at greater risk of colliding with windows compared to resident birds. Well-designed “hazard signs” for birds, especially the ones passing through, could go a long way for preventing wrong turns and accidents.
I find the driving analogy is useful for thinking about how we can help birds to navigate safely through the built environment. I am working on my PhD in biology at Western University studying how bird vision contributes to the risk of bird collisions with windows. I am trying to develop new methods to measure how birds see windows and glass modifications. My research could help industry to produce materials that send strong visual signals to birds as they are approaching a solid barrier (to slam on the brakes or swerve, fast!). In other words, I want to figure out how to modify windows in a way that is optimal for birds’ visual sensitivities, kind of like how road signs were designed for human drivers.
Unlike on roads, we can’t just plaster bright colourful signals on building windows to save birds. That would be aesthetically unacceptable, but a bigger issue is that we don’t know enough about how birds in flight actually see those kinds of signals. What does the equivalent of a stop sign for birds look like? For the most part, existing “Bird-Friendly” or “Bird-Safe” products are based on a human perspective of window collisions, trial-and-error testing and educated best guesses about what birds can see. It seems like some existing solutions hold merit and actually do prevent collisions, but scientific understanding of why and how those products work is limited.
My research aims to learn about how birds see window glass by studying their behaviour and physiology. It is difficult to imagine a bird’s perspective of the world because bird vision is so fundamentally different from human vision. For example, birds see a much wider range of wavelengths of light than humans can (although not all bird species see ultraviolet). The retina of a bird eye is structured differently than the retina of a human eye with different types and configurations of photoreceptors – cells that absorb light and transmit signals to the brain. There is also wide variation at every level of the visual system across bird species. What does all this mean for understanding and preventing bird collisions with windows?
Understanding how birds see windows can help to answer lots of interesting questions about why bird collisions happen. For instance, FLAP data suggests that some species of birds are at greater or lesser risk of collisions. What explains these differences? A previous collaboration between FLAP and scientists at Western University explored how the frequency of collisions for particular bird species relates to bird abundance in the environment. My research explores collision risk at a finer scale – by examining how individual birds interact with glass. My hypothesis is that the risk of bird collisions with windows is related to sensitivities of the avian visual system. To test my hypothesis, I will combine computer models of the avian visual system with behavioural experiments with live birds. Although we aren’t quite there yet, I believe this method could provide the tools necessary to study how different bird species see glass and collision deterrents in the future.
I am often asked which solution I think is truly the best for preventing birds from crashing into windows. I believe the process of properly answering this question will require some outside-the-box empirical research rooted in neuroscience and biology, the kind I am excited to be working on for my PhD. Science has only just begun to scratch the surface of understanding how birds see glass windows and visual markers. In the meantime, I recommend sticking to solutions that are consistent with the Canadian Standards Association’s (CSA) 2019 Bird-Friendly Building Design Standard.
Brendon Samuels is a PhD student in the Department of Biology at Western University. Brendon works at the Advanced Facility for Avian Research and studies the relationship between bird vision and window collision risk. Brendon leads a Bird Safe Campus team for Western and is involved with municipal efforts in the City of London to adopt bird-friendly programs.