The birds and the…buildings?
Global biodiversity is in steep decline, with the World Wildlife Fund reporting a 68% loss of wildlife populations since 1970. While many factors contribute to biodiversity loss, a major driver is the conversion of natural areas into urban developments. Urban areas have doubled in the last 30 years and continue to grow, with much of this growth occurring in biodiversity hotspots.
Modern urban building design is contributing to bird population declines, as an estimated 16-42 million birds in Canada and up to 1 billion in the USA die annually as a result of building collisions caused by the disorienting effects of glass and artificial light. Research in this area is important as we know birds are key components of the global ecosystems that our own health and livelihood depend upon. Protecting birds locally contributes to the protection of biodiversity globally.
This blog post explores tangible solutions to the issue, examines the notion of sustainable buildings, and emphasizes the benefits of bird-safe buildings, for them and for us.
Window strikes are the second largest cause of urban avian mortality, after cat predation. These collisions occur because birds have difficulty interpreting glass as a physical obstacle, and those flying at night are further disoriented by building light. Peak numbers of window strikes occur during spring and fall migration, and the majority of victims are songbirds. More than 70% of victims in the Northern Hemisphere are migratory species, many of which are of conservation concern.
Structures that contribute to window strikes range from tall glass skyscrapers to small houses. A review of 92,00 fatality records from North American monitoring programs found a key factor that predicts a building’s collision risk is high glass surface area. Other factors that increase collision risk include the presence of nearby vegetation, light emitted from building windows, and large building size.
Solutions!
Glass windows can easily be modified to become bird-safe. Unsuccessful methods include tinted or angled glass, interior screens, bird of prey images, and 2D predator models. Successful methods work by creating clear and repetitive visual markers to inform birds that they are approaching a solid object. For example, external shutters reduce the amount of visible glass, and netting or one-way films make glass appear more opaque. Another option is to reduce reflectivity, which can be done by staining or frosting. UV glass is an elegant option since birds can see ultraviolet but people can’t.
The simplest and most popular option is fritting. This includes decals, tape, ceramic frit, or acid etching that create opaque patterns. However, patterns must uniformly cover the glass surface and be spaced at a maximum of 2” high and 4” wide to successfully prevent window strikes, as birds generally won’t attempt to fly through spaces smaller than that.
Lastly, a unique option from the field of biomimicry is a type of glass inspired by spiderwebs. Since some spiders use UV reflective strands - potentially to deter birds from flying through their webs - this glass utilizes an intricate UV pattern in much the same way. The product demonstrates the potential to glean inspiration from nature’s solutions to fix human problems.
Light is the other cause of window strikes, and a straightforward solution is to simply reduce urban light pollution. When outdoor lightning is necessary to highlight a building, downward lighting is recommended over upward, as well as reducing light “trespass” outside of necessary areas. “Lights Out’ programs have emerged across North America to encourage the public to turn off overnight lights during migration season, to reduce fatalities at this sensitive time.
In addition to the above methods that can be retrofitted to existing buildings, there are also architectural elements that can be considered early in the design process to reduce collisions. For example, since collision risk increases with glass surface area, buildings designed with a total glass surface area of less than 25-40% relative to the total façade can successfully reduce collisions. Eliminating hazardous glass elements such as transparent walkways, railings, or corners can go a long way too.
What makes a building sustainable?
“Green” buildings, defined as those designed to reduce the harmful impacts that they have on the environment and occupants, are currently on the rise. However, even LEED certified buildings can still cause significant window strikes, begging the question: can a building be considered “green” if it’s deadly to birds? The American Bird Conservancy helped develop a special LEED credit that encourages building developers to reduce mortality to birds; however, this credit is not mandatory to earn certification. This suggests that sustainable design and bird-safe design are not synonymous, and while green buildings may be icons of sustainability with their focus on energy, water, and materials, perhaps not enough attention has been given to biodiversity.
One area for improvement is policy. Vague recommendations make it difficult to objectively quantify whether designs comply with requirements, and voluntary guidelines can be ignored. This highlights the need for clear and mandatory government policies. Thankfully, policies promoting bird-safe building design are increasing across North America, led by Toronto and San Francisco.
Building codes and municipal bylaws can help advance sustainable building design, but sustainability need to be a central part of the planning and design process, not an afterthought; therefore, integrated planning is key. Municipal, provincial, and federal scales must be engaged, due to the fact that sustainability reflects global needs but depends upon local action.
The beauty of bird-safe design is in its interdisciplinary benefits. In terms of the environment, the benefits of bird-safe design are obvious. Protecting bird populations means securing the priceless ecosystem services that they provide, from population control, seed dispersal, and supporting the food chain. Conserving birds is an essential step in protecting biodiversity, and with urbanization threatening their wild habitats, it’s critical that we support them within urban spaces.
Birds in urban spaces bring immense social and economic benefits too. Human vitality depends on their ecosystem services, such as pest control, which reduces damage to crops as well as disease transmission. Birds are also an educational and economic resource, given that bird-watching is a multi-billion dollar industry, and they have aesthetic and cultural value that benefits our wellbeing.
Economically, the cost of making a building bird-safe is relatively low. One study spent only $26 USD on window decals that reduced collisions by 84 %, demonstrating that bird-safe measures are extremely affordable. The American Bird Conservancy insists that designing a bird-safe building doesn’t add to the cost of construction, and costs can be minimized by targeting problem areas instead of entire façades. Additionally, many bird-safe materials and designs that modify glass windows also help improve security measures, reduce building energy costs, add aesthetic value, and control heat and light; for example, solar screens outside of a window can be adjusted to protect occupants from the sun and control indoor heat. In terms of reducing light-related collisions, switching to daytime cleaning of office buildings or using automatic timers has the added benefit of energy and cost savings for building owners. Thus, it’s entirely possible to adjust and improve our structures to be more in tune with nature.
Research on this topic is significant as it highlights opportunities to transform our cities to support not only local birds, but global biodiversity by extension. Understanding the impacts our cities have on wildlife can inform conservation efforts, to reduce this threat before irreversible damage is done.
Sustainable communities cannot be achieved without consideration for the species we share our urban spaces with. Given that biodiversity is fundamental to human wellbeing and a crucial component of Earth’s life-support system, the preservation of biodiversity must become a priority of governments and urban planners. We need to redesign our cities in ways that support biodiversity, including implementing bird-safe measures to enable our coexistence with birds and ensure they remain active players in global urban ecosystems.
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