Bird Safe Glass Protects Biodiversity

In a Nutshell

Researchers estimate that more than 1 billion birds die each year due to window collisions.

This occurs especially in built environments close to rural areas, and can cause reductions in bird populations, creating a significant conservation risk to biodiversity.

This article examines the issue and the remedies that are available, including smart technologies such as bird safe glass.

Why do birds collide with windows?

Windows reflect the local environment, including trees and foliage, which confuses the birds into thinking they are flying into safe territory.

You might think that the simple answer is to simply to reduce window reflectance.

However, reduced reflectance at night time can have a negative effect, since it increases visibility onto interior plants or vegetation, which can result in the same risk of injury or death.

Also, artificial lighting attracts birds at night and causes them to deviate from their normal (often migratory) flight paths. In fact, bird fatality rates increase proportionately with light emitted from buildings.

Birds sometimes even attack their own reflections in an attempt to protect their territory.

Fewer collisions occur in highly-developed areas and yet, high-rise buildings have the highest median annual mortality rates.

Some species are listed as ‘Birds of Conservation Concern’ due to their risk of declining populations.

These include: 

• Golden-winged Warbler (Vermivora chrysoptera)
• Painted Bunting (Passerina ciris)
• Canada Warbler (Cardellina canadensis)
• Wood Thrush (Hylocichla mustelina)
• Kentucky Warbler (Geothlypis formosa), and 
• Worm-eating Warbler (Helmitheros vermivorum).

What are the effects of bird-window collisions?

Sadly, birds can be killed immediately upon impact, or sometimes stunned, while suffering internal injuries, only to perish thereafter.

The financial costs to building owners is also real and cannot be understated, as window breakages can result in lengthy and costly glazing replacements.

Finally, the psychological impact on occupants, especially children or older citizens, can result in feelings of despair for the harm being done to our natural environment.

What remedies avoid bird-window collisions?

Reducing the reflectivity of glass facades is a start, since this can minimize confusion to birds.

Other measures include:

• Frequently-spaced patterns on the glass to ensure even the smallest birds are protected from collision. This can take the form of ceramic frits or etchings on the glass.
• Installing screens or taut netting over the window exterior (so birds just bounce off).
• Installing one-way transparent film such as this one from Collidescape which makes the window appear opaque on the outside.
• Installing external shutters, awnings or sun shades, which block reflected light.
• Adding interior vertical blinds (and keeping the slats partially open).
• Avoiding nocturnal lighting which draws migrating birds off course and towards buildings.

How can smart glass help?

We define smart glass as “any glazing material having surface coatings, internal structures or embedded circuits that influence the optical, electrical, thermal or mechanical properties of glass’.

There do exist bird-friendly (bird-safe) glass products which change their optical properties specifically to enhance visibility to birds and reduce collisions. More on that below.

Bird Safe Glass

One particular product takes the form of a bird-safe window film that absorbs ultraviolet (UV) and re-emits it as blue light at 450 nm (nanometres). This corresponds to the peak sensitivity of bird vision.

The film also scatters and fluoresces light, creating a visual disturbance to birds. When textured with a fluorescent dye, the film increases the intensity and range of the visual effect. 

These films are highly visible to birds (appearing as a blue glow), but less noticeable to human vision which has a sensitivity of only 7% at 450 nm.

Thanks to bird safe glass, birds can distinguish between the reflections in windows and the scenery itself, whilst allowing the building facade to maintain its aesthetic appeal. 

The films can be affixed easily to window interiors, avoiding damage due to extreme weather conditions. In fact, if we apply multiple films to multi-pane glass, especially in vertical and horizontal strips, this reduces the chances of bird strikes by up to 86%.

However, we should also take note of a research study which concluded that window films on interior window panes may not be as effective as those compared to exterior surfaces.

Threat Factors and LEED

The American Bird Conservancy, working with architects, developed a concept in 2010 called the ‘Material Threat Factor’, or simply Threat Factor.

This gives architects a mechanism to design built structures that do not endanger wildlife, especially near to rural areas where the chances of bird strikes are higher.

The key is to standardize a number of techniques, including glass with ceramic frits, acid-etched glass or glass with engineered optical properties, as described above.

This benchmark evaluation allows an objective assessment of various products to facilitate decisions in sourcing supplier products.

Ideally, no more than 5% of the facade areas which are within the first 40 feet above grade can have a Threat Factor higher than 30.

Finally, check out our analysis of how bird-safe glass can help property developers and architects achieve LEED v5 compliance by allowing the building to meet ecological conservation goals.

Bird Safe Glass Suppliers

Below are listed some manufacturers of anti-collision window films in alphabetical order:-

• Artscape
• Birdshades
• Glas-Pro
• Haverkamp

Outlook

We are now seeing increased awareness of the dangers to wildlife from human built environments. 

This has resulted in government regulations and public initiatives such as LEED v4.1, as well as technological advances in smart glass to reduce the risk.

Organizations such as the American Bird Conservancy (ABC) and the Bird Friendly Building Certification program are driving ahead positive change and causing architects to rethink the impact of built structures on the environment.

Smart glass is well placed to offer a unique solution that reduces bird fatalities, reduces solar heat gain and reduces glare on building occupants, all with one set of products.

This bodes well for the future of our building stock and the environment which we cohabit with nature.