Birds aren’t generally a consideration when designing a building, but the wild bird populations are dwindling and glass collision is the biggest culprit in bird deaths, so it’s perhaps time to add birds to design considerations. It’s much easier and cheaper to make small changes to accommodate our feathered friends in the design phase than it is to retrofit, so let’s take a look at some ways in which we can keep unwanted birds out and help preserve our wild bird populations.
Increase in glass use is bad news for birds
As improvements in window technologies allow homes and larger buildings to use more glass while preserving the efficiency of their building envelopes, more glass means an increase in the incidents of bird fatalities. Combined with a loss of habitat, the wild bird populations of North America are being decimated with 25% of domestic bird species on the watch list while numbers dwindle across the board.
The American Bird Conservancy has set broad outlines to help designers construct buildings that mitigate bird deaths. Here is their list of bird-friendly design specifications:
- At least 90% of exposed façade material from ground level to 40 feet (the primary bird collision zone) has been demonstrated in controlled experiments to deter 70% or more of bird collisions
- At least 60% of exposed façade material above the collisions zone meets the above standard
- There are no transparent passageways or corners, or atria or courtyards that can trap birds
- Outside lighting is appropriately shielded and directed to minimize attraction to night migrating songbirds
- Interior lighting is turned off at night or designed to minimize light escaping through windows
- Landscaping is designed to keep birds away from the building’s façade
- Actual bird mortality is monitored and compensated for (e.g., in the form of habitat preserved or created elsewhere, mortality from other sources reduced, etc.)
In Canada, the Fatal Light Awareness Program (FLAP) aims to reduce collision deaths through education.
As of October 14th, 2011, the Green Building Council (GBC) has added Credit 55 (Bird Collision Deterrence) to the LEED certification protocol. This provision enables designers to calculate their building’s threat to birds rating and, if that rating is below the standard, they will receive credits which count towards their LEED certification.
Taking measures to mitigate bird collisions will also help you to earn your Green Globes certification. Here design professionals must focus on: “: i) minimizing night time lighting; AND ii) applying bird-safe treatment to indicate the presence of glass; AND/OR iii) avoiding reflections in the glass that birds will confuse with habitat; AND iv) monitoring the effectiveness of the collision mitigation measures.”
Glass treatments or designs which partially block windows prevent birds from mistaking large glass surfaces as navigable. Designs such as open-topped atria and windowed courtyards allow birds to get in easily, but it is difficult for them to find a way out. Research by Martin Rössler, Dan Klem, and Christine Sheppard focused on spacing, width and orientation of lines marked on glass and found that certain patterns which covered as little as 5% of the glass surface could prevent 90% of fatal collisions. For example, birds won’t fly through horizontal spaces of less than 2” or vertical spaces narrower than 4”. When lines are traced onto the glass, the birds know to avoid this surface.
These patterns can be combined into decorative façades that wrap glassed buildings. Alternatively, designers can include grilles, netting, screens, and exterior shades to make buildings bird-friendly.
Reducing nighttime lighting is also essential in preventing deaths and is especially important during spring and fall migratory times.
Green roofs which are well designed can provide a vital oasis for birds in an urban landscape provided that they are situated well away from glassed areas.
Angle glass panels 20°-40° so that vegetation is reflected downwards.
Sunshades, awnings and grills help to keep out the sun and can help deter birds.
Move vegetation from glassed areas as reflected vegetation increases the incidence of collision deaths.
The efficacy of preventative measures can be monitored by regularly surveying the affected area prior to improvements and after and counting dead or injured birds.