Bird safe glazing treatment refers to various methods used to make glass surfaces more visible to birds, in order to prevent bird collisions. An estimated 365 million to 1 billion birds die from striking glass in the United States each year. Making glass bird friendly can significantly reduce this problem.
Why do birds collide with glass?
Birds don’t see glass the same way humans do. They either don’t see the glass at all, or they see habitat reflected in the glass, like trees or sky, and try to fly into it. Glass is invisible to birds for two main reasons:
- Birds can see ultraviolet light, which humans cannot. Most transparent and reflective glass absorbs UV light, so glass appears invisible or as an open path to birds.
- Glass reflects habitat like vegetation or sky. Birds try to fly into the reflections without realizing it is a solid barrier.
Certain conditions make glass even more dangerous for birds:
- Sheet glass – Large, reflective expanses of glass on buildings are a major hazard.
- Tinted glass – While it appears opaque to humans, tinted glass looks transparent to birds.
- Angled glass – Glass angled outward reflects more habitat and sky, attracting birds.
Birds are vulnerable to striking glass under certain circumstances as well:
- During migration – Birds are more likely to collide with buildings during migration periods.
- Fledglings – Young birds leaving the nest for the first time are more apt to strike glass as they learn to fly.
- Feeding – Birds chasing prey or approaching feeders near windows are at higher risk of collision.
Types of bird safe glazing treatments
There are a few main approaches to making glass safer for birds. The most effective treatments create visual noise and reduce reflectivity on the glass surface, alerting birds to the presence of a solid barrier.
Surface films and tape
Applying special patterns, dots, or lines to glass surfaces can deter bird collisions. Options include:
- Dot patterns – Small dots spaced 2 inches apart or less work best. Varying dot size, color, and density creates visual noise.
- Vertical or horizontal lines – Stripes spaced 2 inches apart or less effectively signal a barrier.
- Decals and tape – Easy to apply decorative films and tapes can be used, if spaced properly.
External screens
Installing items like netting, screens, shutters, and exterior shades over or in front of glass impedes reflections and visibility. These options are most suitable for large expanses of continuous glass. Screens can also help insulate buildings.
Ultraviolet patterns
Glass can be etched with patterns, frits, dots, or lines visible only in the UV spectrum that birds see. This alerts birds while remaining translucent and unobtrusive to humans.
Angled glass treatments
Making angled or sloped glass more visible is especially important, as it reflects more habitat and sky. Options like films, screens, shades, and UV markers effectively deter bird collisions on angled glass.
How effective are bird safe treatments?
Research shows bird friendly treatments can reduce collisions by up to 90% when applied properly. Here are some key factors determining effectiveness:
- Spacing – Markings must be no more than 2 inches apart horizontally and 4 inches vertically.
- Coverage – Treatments applied to 10% of the glass surface area can deter 90% of strikes. Full coverage is best.
- Pattern variations – Irregular patterns work better than grids to break up reflections.
- Project location – Treatments are most effective in high risk areas near landscaping and in migration pathways.
Treatment Type | Effectiveness |
---|---|
Surface dots | Up to 80% effective |
Surface stripes | 70-90% effective |
Decals and tape | 60-80% effective |
Netting/screens | 90-100% effective |
UV patterns | 60-90% effective |
Permanent vs. temporary treatments
Both permanent and temporary options are available for bird friendly building treatments:
- Permanent – Etched or fritted glass, window films, screens, exterior shades. Lasts lifetime of glass surface.
- Temporary – Decals, tape, removable shades. Shorter lifespan from months to a few years.
Permanent treatments provide lasting protection at a higher up front cost. Temporary options work well for short term use or to test effectiveness before permanent application.
Building code requirements
Some cities and counties have enacted bird-safe building legislation requiring glazing treatments on new construction. San Francisco, Oakland, Sunnyvale, and New York City are examples of cities with bird safe building codes and guidelines.
Typical requirements include:
- Applying treatments to a certain percentage of glass, like 60%.
- Meeting 2″ x 4″ spacing rules for patterns and markers.
- Treating glazing within a set distance of landscaping or water features.
- Using treatments on angled glass and glass railings.
Codes apply mainly to large commercial buildings. Voluntary programs and incentives are also available to encourage bird friendly home construction.
Cost of bird safe glazing
Bird safe treatments typically add less than 2% to overall building construction costs. Retrofitting existing buildings has a wider range of costs depending on the treatment method used.
Here are approximate costs for some common options:
- Dot window films – $0.50-$2 per sq. ft. installed
- Exterior screens – $25-$35 per sq. ft. installed
- Decals and tape – $0.20-$0.40 per sq. ft.
- Fritted or etched glass – 1-10% of glass unit cost
UV patterned glass is generally 15-25% more expensive than standard glass. Consulting with contractors and glazing specialists is recommended to estimate project-specific costs.
Conclusion
Making glass bird friendly through the use of visual markers, patterns, and screens has proven highly effective at reducing bird collisions. A range of solutions are available to fit different budgets and project scopes. With some forethought, new construction and existing buildings can incorporate bird safe design features that prevent unnecessary bird deaths.