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Bird-Building Collision Reduction:

Strategies for Architects, Developers, Building Owners and Managers

Daytime Window Reflection Hazard
(Photo: FLAP)

As our urban environment continues to grow, so do the negative impacts it has on the natural environment. We all have a responsibility to try and lessen these harmful affects by adopting an ecological approach to planning, designing, building, and retrofitting our cities and towns.

The bird/building collision issue is now incorporated into sectors of the green building movement, i.e. the City of Toronto’s Toronto Green Standard and the U.S. Green Building Council’s LEED Bird Collision Deterrence Pilot Credit.

Building aesthetics is important to everyone. Visual cues that birds need to avoid impact with glass are perceived to interfere with this demand, when in fact they can beautify a building’s facade. The moment one looks at glass as a canvas, the options for individuality and beauty become limitless.

This page highlights collision reduction strategies, supported by research, that offer cost-effective, durable, and aesthetically-pleasing solutions, while helping to provide a safer passage for migratory birds through urban areas.

Migratory birds are protected species under federal legislation (Species at Risk Act) and provincial legislation (Ontario Environmental Protection Act).

Nighttime Lighting Hazard
(Photo: FLAP)

Why Do birds Collide with Windows and Buildings?

Bird-building collisions occur most frequently in dense urban areas. During the day, birds see their habitat (trees, bushes, sky, water) reflected in the windows and reflective exteriors on buildings and fly towards them. Or they perceive clear passage through the transparent glass on linkways between buildings or through glass-walled solariums and lobbies. birds might also strike a window when they see interior, ornamental plants and trees through clear glass and try to take refuge there.

During the night, birds are drawn to the artificial sky glow produced by excessive, overnight lighting. They flutter around the lights until they drop from exhaustion or collide with the buildings themselves. If they survive until daybreak, birds find themselves trapped in a maze of reflective buildings and collide with the windows and reflective walls in an attempt to escape.

You Can Make Your Buildings Safe for Migrating birds

As architects, developers, building owners and managers, you have a corporate responsibility and a prime opportunity to influence the designs of new buildings, and to upgrade existing buildings to be bird-safe.

Window Film Application
(Photo: FLAP)

The Key to Bird-Safe Buildings

The key to bird-safe buildings is to provide birds with the visual cues they need to alert them to the presence of glass and reflective building exteriors.

During the night, birds are drawn to excessive overnight lighting. Your careful consideration when planning both interior and exterior lighting systems, and reducing unnecessary overnight lights will lessen the fatal attraction of your building to birds.

Common Myths about Bird Deterrents

  • Hawk Silhouettes: Single window decals in the shape of a hawk silhouette do not frighten birds. The shape of a window decal is unimportant in bird-window collision prevention. It’s the use of multiple window decals, of any shape, that helps make windows visible to birds.
  • Single Window Decals: The use of single decals (including WindowAlert), affixed to a window will not deter birds. One decal covers only one small portion of a window. Unless the bird is headed for that spot it will not be alerted to danger. The use of multiple decals lessens the areas of exposed glass and helps make windows visible to birds.
  • Noise Deterrents: Common noise deterrents include high-frequency ultrasound, noise cannons and the recorded distress calls of various species of birds. In urban settings, these devices attempt to deter birds where colonies of resident species, like pigeons, are situated in public areas. Noise deterrents are ineffective at preventing birds from colliding with windows.
  • Plastic Owls: birds quickly learn that a motionless plastic owl is not a threat. This type of deterrent is ineffective at preventing bird-window collisions.
  • Magnetic Fields: Some bird deterrents emit a magnetic field which theoretically disrupts a bird’s geomagnetic orientation and encourages them to avoid the area. Magnetic fields are not effective at protecting birds from window collisions.

A Rule-of-Thumb to Follow for Visual Markers on Windows

Ornithological research strongly supports that by correctly following the instructions below, bird-window collisions can be greatly reduced, and in some cases eliminated.

  • Uniformly cover windows with a pattern of any shape so that the pattern elements are separated by 10cm (4 in) if applied in vertical columns or by 5 cm (2 in) if applied in horizontal rows.
  • Pattern elements can vary in width from 0.32 cm (1/8 of an inch) or greater.
  • Pattern elements should contrast as much as possible with the clear or reflective window pane to be effectively visible to birds.
  • At see-through sites where clear panes are located one behind the other (e.g., greenhouses, solariums, glass walkways, corner windows) or where clear panes allow views of interior plants, uniform patterns can be applied to either the inner or outer window surface. Please note, applications to the outer window surface provide the best results.
  • Uniform patterns on reflective windows must be applied to the outside surface in order to best disrupt the illusion of facing habitat and sky.

Visit Dr. Daniel Klem, Jr.’s website to learn more.

The Critical Area for Application of Visual Markers

The critical area for application of any bird-collision reduction strategy that meets the above criteria is no less than the first 16 metres (52 feet) above grade.

This dimension relates to the height of a typical city tree reflected in a window or building exterior. Dense visual markers in this critical area provide protection for birds.

The following collision reduction strategies are condensed from the City of Toronto's Bird-Friendly Development Guidelines. The guidelines were published in 2007, in close partnership with the Fatal Light Awareness Program. FLAP's expertise and research findings helped set the parameters for these bird-friendly strategies.

The guidelines emphasize visual markers on windows as the most effective collision reduction strategy. While all of the other techniques suggested in the guidelines are also effective (i.e., angled glass, awnings, overhangs, louvers etc.), properly applied visual markers on windows potentially remove the need for employing other techniques.

Important Note: For the most effective results at achieving bird-safe buildings, it is crucial to use the dimensions cited above in the rule-of-thumb on any exposed areas of glass.

There are a number of guidelines from urban centres across North America:

  • Click here to view the City of Toronto's Bird-Friendly Development Guidelines
  • Click here to view the City of Toronto’s Toronto Green Standard
  • Click here to view the City of Calgary’s Bird-Friendly Urban Design Guidelines
  • Click here to view the New York City Audubon’s Bird-Safe Building Guidelines
  • Click here to view the San Francisco’s Standards for Bird-Safe Buildings
  • Click here to view the American Bird Conservancy’s Bird-Friendly Building Design
  • Click here to view the US Green Building Council’s LEED Pilot Credit 55: Bird Collision Deterrence
  • Click here to view Audubon Minnesota’s Bird-Safe Building Guidelines
  • Click here to view the City of Chicago’s Bird-Safe Building: Design Guide for New Construction and Renovation
  • Click here to view New York State’s Bird-Friendly Buildings Act
  • Click here to view the United States Government’s Federal Bird-Safe Buildings Act

Strategies for Glass:

Create Visual Markers on Windows and Reflective Exteriors

Window Film Application
(Photo: FLAP)


  • Design buildings with densely patterned decorative exteriors to help birds perceive the building as a solid object.
  • Incorporate patterned, etched, or glass block into building designs that include linkways and other large expanses of transparent or reflective glass.
New generation of window film
(Photo: FLAP)


Feather Friendly® Technologies in association with the Convenience Group provide window film technologies designed to reduce bird collisions. The solution consists of the application of various patterns of visual markers of a specific size, colour, and spacing to the exterior glass surface to provide the necessary visual signals for birds to avoid impact. The solution provides in excess of 98% clear viewing by building occupants and is ideal for new construction and retrofits on existing buildings. A do it yourself residential kit is available.

In 2009, FLAP partnered with the City of Markham to test a Feather Friendly Technologies patterned film on the windows of a City of Markham building, 8100 Warden Avenue (see image on the left). The analysis of FLAP's collision records at this site demonstrated an annual attrition rate of over 100 birds. Following the application of this test film, site visits concluded over a 97% reduction in bird collisions.

FLAP participated in additional field research in 2012 at both Consilium Place and Yonge Corporate Centre in Toronto that involved a new generation of Feather Friendly Technologies window film (see image on the left). As a result, both locations also experienced dramatic reductions in bird collisions.

For more information, visit: Feather Friendly®



Protect birds with CollidEscape, a densely-perforated window film with the best results for reducing collisions. CollidEscape is used on many existing buildings for the purposes of advertising or security.

From the outside, CollidEscape looks opaque and eliminates window reflection and transparency. This protects birds from collisions. From the inside, CollidEscape looks like a window screen. This preserves your view and the flow of natural light into your home.

This image captures the mid-way installation of CollidEscape at the Toronto Zoo.
(Photo: FLAP)

In 2001, the Toronto Zoo applied a similar product on an expanse of glass known to kill birds at their facility. They reported complete success in eliminating bird-window collisions at this location.

CollidEscape and FLAP have a long-standing partnership in their commitment to prevent birds from colliding with windows. Visit CollidEscape for FAQ's, photos of CollidEscape installations, and purchase information.

Important Note: CollidEscape is better suited as a daytime collision prevention technique. At night, CollidEscape becomes see-through from the exterior.


birds can see ultraviolet (UV) light: a part of the spectrum in natural sunlight that humans can not see. birds rely on their perception of UV light for success and survival when courting, reproducing or finding food. They are able to detect the reflected UV light from the feathers and bills of other birds, from a variety of berries and seeds, from the wings of insects, and (for raptors) in the feces and urine of some small rodents. This alerts the bird to the presence of a potential mate, or a possible food source, and aids them in their survival in the natural world.

There are several, new and promising window techniques available that use ultraviolet technology to help reduce bird-window collisions. Research indicates that birds are alerted to the presence of glass when they detect a UV pattern applied to a window.

Photo: Ornilux

Bird-Window Collision Reduction Technology

ArnoldGlas, a German company that manufactures glass, has developed a bird protection glass called, “Ornilux” that they claim prevents 71% of bird-window collisions. Ornilux earned ArnoldGlas the Innovation Award for Architecture and Building in 2006 and was recently selected as one of the top 10 most exciting Green Building Products during the 2010 Greenbuild conference in Chicago.

Ornilux glass is embedded with ultraviolet (UV) patterns which are highly visible to birds and almost imperceptible to humans. Ornilux protects the lives of birds and maintains window aesthetics.

While Ornilux is still being refined, the current version is already in use by commercial and residential owners in Germany, the United States, and Canada.

Photo: WindowAlert

WindowAlert window decals have also adopted this UV concept. WindowAlert states that these decals help reflect ultraviolet light. The reflected UV light is thought to be seen as a bright, iridescent glow to a bird’s eye, but invisible to humans. The decal, defined by its glow, is designed to help alert birds to the presence of glass.

Important Note: As with all the other suggested techniques, it is important that WindowAlert decals are applied according to the rule-of-thumb: 5 cm (2 in) apart horizontally or 10 cm (4 in) apart vertically.

Visit WindowAlert to read more about bird vision and ultraviolet light and to see pictures of WindowAlert decals in various applications.

Strategies for Muting Reflective Exteriors

Please Note: The following exterior strategies would not be required if all windows were treated with visual markers that meet the criteria of the rule-of-thumb up to 16 meters (52 feet) above grade. (Though the City of Toronto guidelines requires treating windows up to 12 meters above grade, FLAP’s witnessed accounts reveal the majority of bird strikes occur up to 16 meters above grade.)

The City of Toronto’s Bird-Friendly Development Guidelines (page 37)


  • If your building design includes glass panels, angle the panels 20°- 40° to project reflected images downward and lessen the fatal attraction to birds (see F on diagram).


  • Install decorative grilles, louvers or film over windows so that the space between slats or markers meets the requirements of the rule-of-thumb (see A on diagram).
  • Install awnings and overhangs over windows within the critical area of 16 meters (52 feet) above grade (see E on diagram).
  • Install energy-saving external sunshades to reduce direct sunlight and mute reflections in windows.

Strategies for Reducing Light Pollution


  • Design any external lighting systems intended for security purposes so that they eliminate direct upward light, reduce spill light and optimize useful light (see H on diagram).
  • Eliminate exterior decorative lighting from designs wherever possible, or use sparingly and project the light downwards.


  • Install motion-sensitive interior lighting in lobbies, walkways and corridors.
  • Use timers to turn unnecessary lights off automatically during after-work hours.
  • Design interior office space that allows for task lights at every workstation and reduces the need for excessive overhead lighting (see B on diagram).
  • Draw blinds and curtains after dark. (see C on diagram)

Strategies for Building Owners and Managers

The following strategies continue to be condensed from the City of Toronto's Bird-Friendly Development Guidelines.


  • Visit Lights Out Toronto!, an initiative by the City of Toronto in close collaboration with FLAP and other non-profit environmental organizations and concerned community partners.
  • Appoint someone in your building to ensure that lights are turned out each night. Rotate the responsibility.


  • Ask tenants and employees to close drapes and blinds at night to reduce the light pollution that attracts birds.


  • Consider daytime office cleaning to reduce light pollution during night-time cleaning that attracts birds.


  • Move interior plants, trees and shrubs away from clear glass to lessen the illusion of a safe refuge. If you can see interior plants and trees through the windows from the outside of your building then so can the birds.


  • Publicize your intent to reduce both daytime and night-time bird collisions with your building tenants and employees.
  • Post news bulletins and/or signage in elevators, lobbies, washrooms and other public areas in your building during each migration season.
  • Email migration alerts to tenants and employees.
  • Use educational displays or hold lunch-and-learn sessions for your tenants and employees.
  • Insert migration information into seasonal company newsletters.

For more detailed information on these collision reduction strategies, please email us at for information, advice, or to have your building(s) assessed for migratory bird sustainability. You can also reach us by phone at (416) 366-3527.