Recent estimates suggest about 25 million birds die each year from window collisions in Canada. The issue is gaining widespread attention. As a result, building owners and designers are learning that bird strike mitigation is a matter to be taken seriously.
It might come as a surprise to learn bird mitigation is accompanied by a legal context.
Although ultimately acquitted when due diligence efforts were proven in court, the Ontario Court of Justice in 2013 found that under Ontario’s Environmental Protection Act and the federal Species at Risk Act, a developer was responsible for the death of hundreds of birds at one its buildings. However, it emphasizes the point that building owners are obliged to take actionable steps to prevent or at least reduce bird strikes.
Toronto is a leader is bird strike mitigation and a model for other major municipalities across North America.
Toronto sits adjacent to Lake Ontario and at the confluence of the Atlantic and Mississippi migratory flyways. Containing one-third of all tall buildings in Canada, the city carries a disproportionately high number of bird fatalities.
Toronto’s 2007 Bird-Friendly Development Guidelines was the first council-adopted document of its kind in North America. Under the city’s 2010 Toronto Green Standards (TGS), further refined in 2014, performance measures for reducing bird collisions were incorporated, thereby defining a green building in Toronto as one that must also be bird-friendly.
The TGS is wide in scope. Bird strike mitigation mandates include exterior glazing up to the 12-metre level, including balconies, of residential developments four storeys and higher, all non-residential developments, and low-rise residential developments abutting a ravine or natural area and containing more than five units. Green roofs and their balcony railing must be mitigated up to the four-metre level, and address along with other architectural features such as potential fly-throughs.
The conflict between buildings and birds can occur during the day or night.
Normally birds use natural cues like the moon and stars to navigate. However, light emanating from urban areas obscures natural cues such as the moon and stars which birds use to navigate. When attracted into an unfamiliar urban environment, they can get trapped. The term is called “fatal light attraction.”
The reflective qualities of glass are another problem that birds encounter in urban areas and even beyond. Trees, vegetation and the sky itself, when reflected on a glass surface, can mislead birds, resulting in them crashing into the glass. Mirrored glass surfaces obviously have a worse result. However, even transparent panels can cause birds to believe they can fly through to an area beyond.
As glass facades become more popular, bird deaths have similarly increased. A New York City study conducted in 2023 suggests each 10 per cent increase in glass exterior can result in between 19 and 32 per cent more bird deaths, depending on the season. It is suggested that keeping window-to-wall ratios less than 40 per cent can dramatically reduce the instances of collisions.
Most bird strikes occur at lower elevations. That’s because reflections of trees, shrubs and natural vegetation are close to the ground. Collisions at higher levels generally occur at night or during periods of poor weather.
The solution to bird strike reduction must go beyond design efforts to angle glass in order to change the reflected image or switching to low-reflective glass.
Interior blinds, tinted glass and bird decals are little help either. Even fly-through passages featuring glass balconies or walkways are known to be a flight trap for birds, no matter how they are positioned. Added exterior features such as awnings, screens, shutters and sunshades can be somewhat helpful though.
The ideal solution is treatment of the glazing itself. Various images can be etched, screened or printed onto exterior glass surfaces to reduce reflection and create awareness of a physical barrier to flight. Dense, high contrast patterns in combination with non-reflective glass are best. An option to patterns is frosted glass, even applied as a retrofit.
John Bleasby is a Coldwater, Ont.-based freelance writer. Send comments and Inside Innovation column ideas to editor@dailycommercialnews.com.
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