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As many as one billion birds die each year in the United States from collisions with glass on residential and commercial buildings. Combined with other lethal threats (cats/dogs, habitat loss, climate change, etc.), window strikes are creating an existential threat for many avian species.

Birds strike windows because they either perceive a flight path through a building or mistake a reflection (usually in a window or door) for a safe flight path.


  • Affixing a bird silhouette decal or two to a window is not enough to prevent window strikes!
  • A home may kill a dozen or more birds a year without the resident even being aware.
  • Homes with bird feeders result in more window strikes than those without. (See Feeder Placement.)
  • Even if a bird flies away after striking a window, she may die elsewhere as a result of injuries suffered in the collision. If you see an adult bird on the ground who appears to need help, try to capture her and get her to a wildlife rehabilitator.

Effective Strategies – External Modifications

Vertical or Horizontal "Stripes"

Apply visible markings to the outside of windows in patterns the birds can see. Most birds will avoid windows with vertical stripes spaced 10 centimeters (4 inches) apart (or less), or horizontal stripes spaced 5 centimeters (2 inches) apart. The stripes themselves should be at least 0.6 centimeters (0.25 inches) wide.

External modifications can be achieved in several ways, most notably:

  • Vertical or horizontal lines made with weather-resistant pens or bird tape.
  • Vertical parachute cords, strings of beads, or bamboo.
  • Acopian BirdSavers are a commercially available option.
  • One-way window films such as those offered by CollidEscape and Feather Friendly.

Night Lighting

Eliminate or minimize external lighting at night, year-round, and close curtains in rooms that are occupied at night. Artificial light at night causes birds to become disoriented. Turning off outside lights (or setting them on motion sensors) protects birds and saves energy and money.

Encourage building managers to do the same!


Cover window exteriors with conventional screens. This reduces reflections and can help mitigate injury by providing a bit of a cushion to birds who hit the windows.

Feeder Placement

If you feed birds, make sure your windows are bird friendly. Place feeders within one meter (three feet, three inches) of windows. From this distance, birds leaving feeders generally aren't able to build up enough momentum to hurt themselves if they do fly into the glass.

Window Replacement

See Bird-Safe Glass.

Effective Strategies – Internal Modifications

Blinds and Curtains

Blinds and curtains can be used to eliminate the perception of flight paths. The best solution to "flight path windows" is to modify them with visual deterrents. Until you do so, you should close blinds and curtains on these windows as a rule.


Move houseplants away from windows. Birds may perceive them as safe landing spots.

Night Lighting

Eliminate or minimize internal lighting at night, year-round, and close curtains in rooms that are occupied at night. Artificial light at night causes birds to become disoriented.

Bird-Safe Glass

Consider using bird-safe glass when replacing windows or in new construction. Patterned glass features visual marks that birds will see as barriers (and therefore avoid). Likewise, acid-etched glass features visual marks or a solid translucent satin appearance that birds will see and avoid. Both types of glass provide a high level of light transmittance. Both can be creative and beautiful while preventing bird strikes. Try Walker Glass Company for acid-etched windows. Other glass products, including those with ultraviolet patterns, should be assessed through,, or consultants, as the technology is rapidly changing.

Building Design

Design buildings to be bird friendly.

  • Use bird-safe glass in new construction.
  • Advocate for the design of building surfaces that make glass more visible to birds.

The American Bird Conservancy offers several examples to encourage bird-friendly building designs and window modifications.

The Canadian Standards Association offers up-to-date bird-friendly building design standards (CSA A460:19). These standards apply to both construction and remodeling of buildings.

Excess Noise and Light

Excess human lighting and noise can lead to fatigue, stress, or impaired decision-making, any of which can have fatal or injurious consequences, especially for birds already facing the inherent challenges of migration.

Eliminate excess noise and light, and design structures, communities, transportation systems, etc. to minimize their emissions of light and noise. See Canada Fatal Light Awareness Program for more information.

A Veritable Lethal Obstacle Course

In addition to threats posed by residential and office buildings and excess noise and light, human structures such as suspension bridges and wind turbines also result in bird injury and mortality.

And on top of all this, window reflections can also result in territorial aggression. In such instances, birds attack their reflections, which they perceive as other birds invading their territory. This can result in beak injuries and even death.


... or for that matter any injured or sick bird?

Any bird who has struck a window and can be captured should be taken immediately to a wildlife rehabilitator. Even if the bird appears to be only stunned, it is still best for a professional to give anti-inflammatories, pain medication, supplemental oxygen, etc. as soon as possible. Expert examination, treatment, and observation are strongly advised.

Always err on the side of caution!

Carefully place the bird in an unwaxed paper bag or a box lined at the bottom with tight-knit cloth or paper towels and containing small air holes. Make sure the bird is upright. If the bird is on his side, make a small "donut" out of paper towels to keep him upright. Do not offer food or water. Move the box indoors, away from predators, to a dark, warm, and quiet location until he can be transferred to rehab. Supplemental heat can help prevent shock (though some rehabilitators recommend avoiding heat because it may exacerbate inflammation). We recommend placing a heating pad set on LOW below the box/carrier – not below the entire bottom of the box; it's important to let the bird escape from the heat if he chooses to do so.

Go to the Animal Help Now homepage or use Animal Help Now's free smartphone app (Android, iOS) to find a nearby wildlife rehabilitator. For guidance, see this short video tutorial.

If you are not in the United States, do a web search for "wildlife rehabilitator" or "injured bird" to find whatever nearby assistance may be available.

For more information on helping animals, see the Animal Help Now Resources page.


Do-It-Yourself Tri-fold Flier (PDF format) for educating people, including decision- and policy-makers, about how to prevent window strikes and find help for window-injured birds.

Avian window strike flier



Bird Smart Glass

Canadian Standards Association Bird-Friendly Building Design

Three Billion Birds

Acopian Center for Ornithology

American Bird Conservancy

Canada Fatal Light Awareness Program

Cornell Lab of Ornithology

Just Save Birds

Ornithological Societies of North America


A special thank you to Prof. Daniel Klem, Jr. (Muhlenberg College [PA]) and Heidi Trudell (Just Save Birds) for the many improvements they provided to the content of this publication. Any mistakes are of course the responsibility of Animal Help Now.