The Invisible Threat: Creating bird-friendly buildings

In 2013, amid growing awareness of the bird/glass problem, a ground-breaking Canadian lawsuit created an important precedent for building owners. The environmental group Ecojustice brought suit against Cadillac Fairview, a firm whose reflective-glass buildings near downtown Toronto had killed hundreds of birds. The suit alleged the killing of birds was caused by a failure of the company to take measures that would reduce bird deaths—an alleged violation of the Environmental Protection Act (EPA) and the Species at Risk Act (SARA).

Cadillac Fairview was held not liable because it had recently taken steps to retrofit the building with an exterior film visible to birds. However, the court did conclude light discharged from windows is a prohibited ‘contaminant’ in circumstances where birds are deluded by the reflection of safe places, such as the sky or trees.

Also, as a result of the court’s interpretation of the law, Ontario can now require building owners to obtain an environmental compliance approval if they are discharging light that is killing or injuring birds. Under SARA, the court found the inadvertent killing of threatened species in window strikes was covered by the provision prohibiting harm to listed species.

State and local jurisdictions have also taken action by passing legislation mandating bird-friendly buildings in certain cases, and more is pending. Toronto requires most development four storeys or greater to adhere to the Toronto Green Standard (TGS), which includes a number of bird-friendly measures.3 These include either treating glass with a density pattern or muting reflections for the first 10 to 12 m (33 to 39 ft) above-grade, and installing shielded light fixtures.

San Francisco’s 2011 Bird Safe Building Act requires bird-friendly treatment of façades for new buildings within a clear flight path of less than 91 m (300 ft) from any natural bird habitat of 0.8 ha (2 acres) or more. The treatment must extend for the first 18.2 m (60 ft) in height of the building and is also required for hazardous features in all new buildings—such as skywalks, glass rails, and transparent corners. Other similar laws are passing in jurisdictions throughout North America.

As concern for bird deaths intensifies, the building community is increasingly demanding new products, information, and design solutions to reduce fatal collisions.

Several published guidelines are now available, including Bird-friendly Development Guidelines, published by the City of Toronto and referenced in the TGS, and Bird-friendly Building Design published by the American Bird Conservancy. Although the science is constantly evolving, certain principles of bird-friendly construction are now generally accepted.

Visual noise
‘Visual noise’ refers to any glass treatment that alerts birds to its presence (Figure 5). Since birds cannot see glass, any texture, pattern, or architectural element making the surface more visible to birds will reduce collisions.

Common treatments include:

  • non-reflective or patterned films on glass;
  • screens or netting positioned in front of glass;
  • retractable shutters;
  • exterior roller shades;
  • changes of glass plane to distort reflections;
  • projecting sun-control elements (i.e. brises soleil);
  • integrally patterned or fritted glass; and
  • tape stripes or patterns on glass.
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