Bird-Safe Buildings

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THe Problem

Have you ever heard that “thunk!” – a bird striking a glass window or door?

Bird-glass collisions are a major threat to birds. More than 1 billion birds die each year after colliding with glass in the U.S. alone.,  That’s the second highest direct-human cause of bird death, second only to outdoor cats. Many think high-rises are the biggest threat but only 1% of collisions occur at high-rise buildings. The vast majority (99% ) of bird-window collisions occur at private residences (1-3 stories) and low-rise buildings (4-11 stories). All sizes of glass are a threat, from small to large.

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Birds can’t “see” glass. Instead, they see reflections of vegetation or sky, think they’re real and fly towards them, often at full speed. Or, birds are misled by glass transparency. They see through the glass and try to reach shelter or vegetation on the other side but strike the glass instead. Light pollution (also called “Artificial Light At Night”, or “ALAN”, for short) exacerbates the problem, drawing birds into developed areas and increasing the reflection and transparency of glass. Even if the bird fly away after a collision, the majority sustain internal injuries and succumb days later.  Although bird-glass collisions occur year-round, they are especially common during spring and fall migration season. 

The Solution

Add patterns to the outside surface of the glass, to break up the reflection and create a visual barrier birds can see.

To be effective solutions must meet the following criteria:

OPTION #1 (for listing 3 criteria)

Markers must be applied to the outside-facing surface of the glass (or, “Surface 1”). Placing them on the outside, or exterior, side breaks up reflections. 

Markers applied on the glass must be spaced no further than 2-inches apart, called the “2 by 2 rule”. Hanging treatments hung in front of the glass (like Acopian blinds), can use a slightly wider spacing of 3- to 4- inches. The close spacing tells birds there isn’t enough space to fly through.

Dots or other shapes should be at least one-quarter inch in diameter. Stripes, or cording, should be at least one-eighth inch wide. 

OPTION #2 (for listing 3 criteria)

  1. Exterior Surface. Markers must be applied to the outside-facing surface of the glass (or, “Surface 1”). Placing them on the outside, or exterior, side breaks up reflections. 
  2. Close spacing: 2- or 4-inches. Markers applied on the glass must be spaced no further than 2-inches apart, called the “2 by 2 rule”. Hanging treatments hung in front of the glass (like Acopian blinds), can use a slightly wider spacing of 3- to 4- inches. The close spacing tells birds there isn’t enough space to fly through.
  3. Large enough for birds to see. Dots or other shapes should be at least one-quarter inch in diameter. Stripes, or cording, should be at least one-eighth inch wide. 

Additional guidelines:

  1. Full Coverage.  Markers and patterns should cover the entire glass surface.
  2. Contrasting Color. Markers should be in a contrasting color. For markers on the glass, white is often the best (though black is for “fly-through” situations). For cording in front of the glass, olive green or black is recommended (though other colors will probably be equally effective). Bigger is better.
  3. Start with the most hazardous windows. Prioritize glass where collisions have already happened. Also, look at your windows at different times of day, from different angles. Glass that reflects vegetation or has a clear view of habitat inside (like potted plants) tends to be the most dangerous. 

For more information about specific treatments, scroll down to the FAQs below

A note about ultraviolet (UV) treatments. While they are a good back-off solution, they generally aren’t recommended because not all birds can see them (raptors, owls, doves, pigeons) and the effectiveness changes depending on time of day and amount of sun. 

This is a sample image

Source: https://www.nps.gov/orgs/1252/upload/Bird-collisions-handbook.pdf

BIRD-FRIENDLY GLASS FAQs

Learn more about how to protect birds from glass collisions.

A wide range of products are available to make glass bird-friendly.

DIY SOLUTIONS

DRAWING ON GLASS

Photo by Erin Diehm

“ACOPIAN” BIRDSAVERS

Bird-Safe DIY Solutions: Paracording Acopianblinds
Photo by Erin Diehm
  • helpful DIY instructions
  • many options for mounting
  • great for upper stories, quick install
  • very affordable (one roll of cording only $20)

PRODUCTS FOR PURCHASE

FEATHER FRIENDLY MARKERS
(for Medium scale)

Feather Friendly, Melody pattern
Photo by Kathy Kramer
  • 95% effective
  • 1/4-inch white round markers meet “2×2” rule
  • On 6-inch wide rolls
  • Only dots remain
  • Guides make it easy to align rows
  • Attractive, clean appearance
  • 10+ years durability and longevity
  • ADD “RESEARCH” LINK?

COLLIDESCAPE FILM
(with Custom photo)

Photo by Erin Diehm
  • 95+% effective
  • Perforated film, like on a bus
  • Use your own photo or free ones online
  • Daytime privacy (people can’t see in, you can still see out)
  • Reduce heat gain 50-60% – great for summer heat
  • 10+ years durability and longevity

“ACOPIAN” BIRDSAVERS
(Paracord blinds)

© Jeff Acopian / Acopian Birdsavers
  • 95% effective
  • 4-inch spacing effective for even small birds (hummingbirds)
  • 3D protection = movement + shadow of cord on glass
  • “Zen Wind Curtains”, fluid, aesthetically pleasing
  • Many options for mounting
  • Great for upper stories, quick install
  • Research

FEATHER FRIENDLY MARKERS
(for Small scale)

Photo by Erin Diehm
  • 95% effective <<- VERIFY
  • 1/4-inch white square markers
  • Apply to meet “2×2” rule
  • Roll of single dots
  • Only dots remain
  • Rulers provided to align rows
  • Attractive, clean appearance
  • 10+ years durability and longevity
  • ADD “RESEARCH” LINK?

COLLIDESCAPE FILM
(in Solid colors)

© CollidEscape
  • 95+% effective
  • Perforated film, like on a bus
  • Choose from white or custom-color (including favorite paint or pantone)
  • Daytime privacy (people can’t see in, you can still see out)
  • Reduce heat gain 50-60% – great for summer heat
  • 10+ years durability and longevity

INSECT SCREENS

  • 99+% effective
  • Eliminates reflections
  • Mount at least 1-inch away from glass
  • If bird does strike, screen acts like a trampoline, reducing impact
  • Not applicable to casement windows (which open outwards)
  • Important that screen covers all glass
  • Research

Most collisions occur on homes and the first four stories of buildings. In addition to turning off lights, you can ensure your windows are bird safe and prevent collisions with window treatments, tested by the American Bird Conservancy.

HANDY TABLE OF BIRD-SAFE TREATMENTS

See the table below, or click here to access the spreadsheet directly.

New glass and construction can take advantage of a wide variety of methods to prevent collisions. And – big bonus – the protections are long-lasting and permanent, protecting birds for the life of the glass. A few examples include:

  • Acid-etch and frit patterns. Glass is clear with permanent markings
  • Opaque and frosted glass. Glass is opaque but translucent textures, channeling or glass block
  • Structures added to the exterior of the building and glass, to provide a visible barrier. Shades, louvers, sheeting materials, and more

A Note About Sourcing

While solutions are expanding, it’s currently easier to source bird-friendly glass for commercial properties than residential homes. Commercial spaces can take advantage of the benefit of scale, ordering a large number of windows and doors with custom sizing for a “special order”. Being of smaller size, residential spaces often don’t have those advantages so sourcing may be more challenging. But we hope to change this situation, by working with bird enthusiasts to help create greater demand at the local level!

Reflection and Transparency are the two primary reasons.

Reflection

© NEED TO REPLACE IMAGE. https://www.birdnote.org/podcasts/birdnote-daily/birds-and-glass-making-homes-safer

Birds don’t perceive glass as a solid object. They see the reflection of the sky, trees, or vegetation, think they’re real (a literal object), and fly towards the glass. But instead of reaching their destination, the bird strikes the glass. 

Transparency

NEED PHOTO

Birds see through the glass – to habitat, open space, or even into a room. They perceive the flight path as unobstructed [a safe corridor/an open flight path/a flyable pathway], and fly towards their destination. But instead of reaching it, the bird strikes the glass.

No. Low-rise and mid-story buildings are the biggest threats, with almost 99% of all collisions happening at lower elevations. In fact Residences (1 to 3 stories, like many homes) account for 44% of collisions. That’s almost half. High-rises are associated with just 1% of all collisions.

“The majority of bird-window collisions happen at apartment buildings,
office buildings, and residential houses.”

Image source: https://swibirds.org/prevent-collisions

One final note – while skyscrapers aren’t the biggest source of collisions, they are typically more illuminated at night and play an outsized role in contributing to the problem of artificial light at night (ALAN) and related bird mortality.

No. Sticking one or two decals on a window – even if they’re larger “hawks” – is usually ineffective because too much glass remains untreated. The bird simply flies between the decals, striking the glass instead. To be effective, markers must be spaced no more than 2-inches apart (hung paracording can be spaced 4-inches apart). In addition, decals are often applied to the interior side of the glass. This may be easier, but putting them on the inside makes them ineffective as they won’t break up dangerous mirror-like reflections on the outside side of the glass.

© Feather Friendly

Bird-friendly treatments are very effective and can prevent more than 95% of collisions. The American Bird Conservancy has tested hundreds of bird-friendly treatments, creating an online database of products. For each treatment tested a “Threat Factor” (TF) is included. The TF is like golf – the lower the score, the better. Only those with a TF of 30 or lower are recommended (as a TF of 30 prevents half of collisions). To learn more about how products are tested for efficacy, watch this short video.  For a summary of some of our favorite products, including the Threat Factor for each, see the Handy Table above.

Ideally, all glass up to the height of mature trees is made bird-friendly. That’s where dangerous reflections of vegetation and sky can lure birds in. If that is not possible, work your way down the following bullet list, from highest to lowest risk (source: the Stop Bird Collisions webpage.):

  • Glass that has caused known collisions
  • Glass near areas that attract birds (e.g. bird feeders, water features, gardens, trees and shrubs)
  • Glass that creates a “passage effect” to trees or other habitat (transparent or reflective)
  • Glass at the end of rock walls, outcrops, or other “funnel” shaped landscape features
  • Glass in a courtyard

Remember, all bird-friendly treatments should be applied to the exterior side of the glass, meeting the 2-inch spacing rule (or, 4-inch for cording).

Renters may want to use bird-friendly treatments that are easiest to remove. Two good options might be DRAWINGS or ACOPIAN BIRDSAVERS (attached with removable 3M CommandTM hooks):

Drawings

Use paint pens, tempera paint or even soap to create an “artistic” drawing or draw “dots” or other repeating patterns.

Artistic drawings. There are many examples of drawings on glass to protect birds, including this one which is easy and affordable, featuring vines and Chickadees. Of course, any pattern is possible – geometric, spider webs, space ships, floral, dinosaurs, to name a few. One option – find a simple pattern you like online, print several copies, cut each one out, tape to inside of glass, then go outside and trace the pattern. Remember to ensure that the completed drawing adheres to the “2 by 2-inch” spacing rule (no area bigger than 2”x2” left unmarked). Filling in with small embellishments can be very helpful.

Oil-based Sharpie on glass
Photo by Erin Diehm
Oil-based pen on glass (From Bird Friendly Design Guidelines for Buildings, University of British Columbia)
Soap on glass
(From Facebook post by Randy Tashjian)

Dots or Other Patterns. Can be drawn free-hand or using a template (homemade or purchased, pictured below). Of course, any other geometric patterns could be drawn, like lines drawn on at 2” spacing. When it’s time to move, if needed, simply use nail polish remover to remove the drawing, being careful to keep it on the glass and not touch surrounding paint or surfaces.

Example of a homemade Stencil
From “DIY Collisions Deterrents“,
Cornell Lab of Ornithology
Example of a stencil for purchase
From Flock Blocker.

Acopian BirdSaver blinds

Paracording spaced at 4” apart. To facilitate removal when it’s time to move out, use removable adhesive mounts like 3M CommandTM Outdoor Hook and Clips. There are many ways to mount the cording. See below for three examples.

Header from Garden Stake. Some bird advocates create a header out of a garden stake, tie paracording to the stake at 4-inch intervals and then hang the stake on two Command hooks mounted to the outside of the glass on the left and right sides. Mounting the Command hooks directly to the glass ensures window frames aren’t damaged when they’re removed sometime in the future.

ASK COLLETTE IF CAN USE PHOTOS

Header from Cording. Instead of a garden stake, some make the header from cording, and then attach the top cord to the window with adhesive clips. While the photos below show the clips attached to the window frame, it’s suggested to attach them directly to the glass, to ensure frames and paint aren’t affected when the clips are removed.

© Jeff Acopian / Acopian Birdsavers
(Step 5 in “How to make “All Paracord” Acopian BirdSavers; using paracord for the top horizontal piece, as well as for the vertical pieces.“)
© Jeff Acopian / Acopian Birdsavers
© Jeff Acopian / Acopian Birdsavers

No Header, just Clips. Others avoid a header altogether by attaching 3M CommandTM Outdoor Light Clips (Model #17017CLR-AWES) hooks across the top of the window frame, spaced 4-inches apart, and then tying a separate cord to each hook. The photos below show the clips affixed to the window frame; but to avoid the possibility of damaging the frame when removing the hooks, each clip can be applied directly to the glass.

© Janet Allen / Our Habitat Garden
© Janet Allen / Our Habitat Garden
(from “Other BirdSavers Examples” on “Our Habitat Garden“)

Yes. Bird feeders and other attractants like birdbaths can greatly increase the likelihood of bird strikes. In fact, where glass hasn’t been treated to deter collisions, “Homes with bird feeders have almost twice the number of window collisions as homes without bird feeders.” (“January 29, 2025: Backyard Birds Bird-Window Collisions“, U.S. Fish & Wildlife Service)

What to do? The first recommendation is to treat windows to be visible to birds, especially those facing a bird feeder, birdbath or vegetation.  In addition, move the bird feeders, birdbaths or other attractant to within 3-feet of the building (so birds won’t have time to build up to lethal speeds).

For additional tips on maintaining bird feeders, click here (from the American Bird Conservancy).

Yes. Guidelines are usually found on a product’s FAQs webpage. As quick reference, here are brief guidelines for three treatments:

  • DIY Drawings. It depends. Markings made with soap or tempera paints are temporary and will probably wash off with the first cleaning (or even rain). Drawings made with acrylic- or oil-based pens will last longer and withstand cleaning, but we haven’t yet found any clear guidelines on this topic. In general, to protect the drawing it’s best to avoid abrasives (like scouring pads). Instead, use soft tools (like a microfiber cloth, sponge), mild solutions (like mild dish soap or a non-ammonia glass cleaner), and apply light pressure when cleaning.
  • Cording. (e.g. BirdSavers or Acopian Blinds) – Acopian blinds are perhaps the most straightforward to clean. If the cording is attached ONLY at the top, simply hold the paracording away from or to the side of the glass. If the cording is attached at top AND the bottom of the window, avoid a side-to-side motion and, instead, move cleaning tools top-to-bottom.
  • Adhesive treatments, like Feather Friendly or CollidEscape – can withstand washing for many years. See the manufacturers webpage for the latest guidelines, e.g.
  • From Feather Friendly, “After the installation, allow the adhesive to set for 30 days before cleaning. You can then clean with a soft cloth, paper towels, or rubber squeegee, along with typical cleaning products for glass, including soap and water and glass cleaners like Windex. However, we recommend against using pressure washers or abrasive cleaners.” (April 2026)
  • From CollidEscape, “Most CollidEscape Applications require nothing more than the occasional hose rinse… [however] There are no performance issues with regularly scheduled window washing services…. [if using a pressure washer, low-pressure hosing]… use of 40 to 60 degree pressure washer nozzle to minimize likelihood of lifting CollidEscape off the glass.” (April 2026)

It depends. Some are short-lived, lasting a few weeks (or until it rains) while others, like commercially available adhesive markers, are guaranteed for a decade or longer.

  • Drawings (soap & tempera paints) – The shortest-lived. Depending on rain and weather exposure, they could last from just a few days to several weeks.
  • CollidEscape – guaranteed for 10 years but can last much longer. In fact, some installations dating back to the 1990s are still in place.
  • Feather Friendly – from 8 to 20+ years, varies by type:
  • 8+ years for Small-scale DIY
  • 12+ years for Medium-scale Pro DIY
  • 15+ years for Large-scale Pro
  • 20+ years for Large-format Evolution
  • Acopian BirdSavers – Varies by installation, especially how the cording is mounted. If screws or other permanent hardware is used, the installation will likely last decades. If adhesive mounts are used (velcro, Command strips), the duration is hard to predict but likely shorter (but also easy to refresh)

Want to see bird-safe glass in-person?! The Golden Gate Bird Alliance has created a map of bird-friendly installations located in public and residential spaces. They include retrofitted and new glass. Go check them out!

If you’d like to visit residential installations Erin Diehm, the GGBA the Bird-Safe Project Lead, can help. Just email Erin at ediehm@goldengatebirds.org.

Together we can make a difference! Here are a few ways to help:

  • Treat your own windows.  If treating all of them at once isn’t realistic, start with the most dangerous ones and then apply treatments to additional windows incrementally.
  • Talk with friends, neighbors, anyone who’ll listen.  Spread the word about bird-glass collisions and especially how easy it is to prevent them.
  • Help friends and neighbors treat their windows.  Organize work parties to help each other apply treatments – learn together!
  • Advocate at work and apartment buildings.  If your workplace has an Office of Sustainability, try starting with them. (See the NYC Bird Alliance or Canadian’s FLAP webpages for helpful suggestions.)
  • Advocate with your city to pass an Ordinance. If your city doesn’t have bird-friendly legislation, attend a meeting and ask elected officials to protect birds. Contact your elected representative(s) to share your interest in protecting birds. (Electeds usually pay attention to their constituents.) Contact your local birding groups and ask for support.

The first place to check is the American Bird Conservancy (ABC), which maintains a database of current legislation, ordinances and codes in the U.S. to prevent window collisions. If your city has adopted bird-safe protections, and they’re mandatory or incentivized, it will probably be listed there. (Because voluntary guidelines tend not to be followed, only mandatory and incentivized guidelines are included.)

Note that the ABC database is broken down into three groups: “Recommended”, “Recommended with Reservations”, and “Not Recommended”. When glancing through the list, it might be useful to review legislation under “Recommended” and “Recommended with Reservations”, to see what specific guidelines are the most effective and which could be improved upon.

If you learn that your city doesn’t have any guidelines, now is the perfect time to advocate for one! Contact local elected officials, city departments and local environmental and bird groups to express your support for bird-friendly legislation. To help you get started, the ABC has a webpage on Bird-friendly Legislation & Code. It’s written to help communities successfully advocate for and pass bird-friendly building codes and laws. It even includes a Model Ordinance, which can be downloaded and edited.

Any bird that has collided with glass should be taken to a professional wildlife rehabilitation center. Even if the bird appears fine it still needs professional care.

Why a rehabber? Birds strike glass at speeds of 25 to 30 miles an hour, often leaving them with concussions. Others have pelvic injuries, from sticking their legs out towards the windows in a last-minute attempt to avoid collision. Anti-inflammatories and professional care are usually needed, including time to recover. A lay person isn’t equipped to diagnose and treat collision injuries. Without receiving professional care, most birds that collide with glass will not survive.

What to do

  • If there’s time, put on gloves or wash your hands
  • Approach the bird slowly and quietly – ideally from behind, to avoid startling it. “Do not talk to the bird as you approach it. Wild birds are frightened of humans and could fly back into the glass or into traffic.” TAKEN FROM NYC ALLIANCE NEED TO CREDIT NYCBA?
  • “Gently but firmly grab the bird by putting one or two hands over its wings. You can also carefully throw a lightweight towel, cloth, or jacket over the bird and scoop it up with the towel.”  TAKEN FROM NYC ALLIANCE NEED TO CREDIT NYCBA?
  • Put the bird in a small paper bag, small cloth sack, or small shoebox. Containers should be ventilated. Close the bag or container (with a binder clip) to prevent the bird from escaping later. A small space protects the bird from excessive activity which could cause further injury. Lining the container isn’t necessary. However, if lining is added, avoid strings and cloth with loops (like a terry cloth towel), which could entangle the bird’s legs and feet. Instead, any lining should be smooth, like newspaper, a paper towel, a cotton pillowcase or T-shirt.
  • Finally, wash your hands and call a professional wildlife rehabilitation center. In the San Francisco Bay Area, local rehabbers include the Lindsay Wildlife Experience (Walnut Creek), Wild Care (Santa Rafael) and Yggdrasil Urban Wildlife Rescue (San Francisco), Peninsula Humane Society & SPCA (South Bay/Peninsula), For additional resources, see the Human Society’s helpful list of rehabbers.
  • If you’re not able to transport the bird immediately, put the bag or box in a quiet dark place (like a closet) until you can. Do not try to feed or give it any water or food.

What NOT to do

  • Do not feed or give the bird water. Giving it food or water could cause the bird to aspirate, a potentially deadly condition.
  • Do not excessively handle or engage with the bird. Avoid petting or touching it. Minimize voices. While these behaviors may calm our pets, they are stressful to birds and most other wild animals.

Report It

If the bird is deceased, due to collision or any cause, contribute to citizen science and report it at dbird.org:

Apply Bird-Safe Treatments

To prevent future collisions, make a plan to apply treatments to glass as soon as possible following the guidelines above: 2-inch spacing (or 4-inches for cording) and on exterior surface of glass. If you know which window the bird struck, prioritize treating that glass first.

If you found a deceased bird, due to collision or any cause, contribute to citizen science and report it at dbird.org:

When was the last time you were able to look up at the night sky and see the Milky Way? Remember the sense of wonder and awe you felt at seeing the brilliancy of the natural lights surrounding our earth. Physically seeing our place in the galaxy has inspired scientific discoveries and artistic creations for millenia. Connecting with our ancestors and the globe in modern times, through stargazing is part of a universal dark sky heritage that we risk losing as our world is increasingly lit up.

Additionally, it is important to remember that humans evolved, alongside our bird and wildlife brethren, in a darker world. Artificial light has negative impacts on our human health, and darkening our urban world will have benefits for humans as well.

When was the last time you were able to look up at the night sky and see the Milky Way? Remember the sense of wonder and awe you felt at seeing the brilliancy of the natural lights surrounding our earth. Physically seeing our place in the galaxy has inspired scientific discoveries and artistic creations for millenia. Connecting with our ancestors and the globe in modern times, through stargazing is part of a universal dark sky heritage that we risk losing as our world is increasingly lit up.

Additionally, it is important to remember that humans evolved, alongside our bird and wildlife brethren, in a darker world. Artificial light has negative impacts on our human health, and darkening our urban world will have benefits for humans as well.

When was the last time you were able to look up at the night sky and see the Milky Way? Remember the sense of wonder and awe you felt at seeing the brilliancy of the natural lights surrounding our earth. Physically seeing our place in the galaxy has inspired scientific discoveries and artistic creations for millenia. Connecting with our ancestors and the globe in modern times, through stargazing is part of a universal dark sky heritage that we risk losing as our world is increasingly lit up.

Additionally, it is important to remember that humans evolved, alongside our bird and wildlife brethren, in a darker world. Artificial light has negative impacts on our human health, and darkening our urban world will have benefits for humans as well.

When was the last time you were able to look up at the night sky and see the Milky Way? Remember the sense of wonder and awe you felt at seeing the brilliancy of the natural lights surrounding our earth. Physically seeing our place in the galaxy has inspired scientific discoveries and artistic creations for millenia. Connecting with our ancestors and the globe in modern times, through stargazing is part of a universal dark sky heritage that we risk losing as our world is increasingly lit up.

Additionally, it is important to remember that humans evolved, alongside our bird and wildlife brethren, in a darker world. Artificial light has negative impacts on our human health, and darkening our urban world will have benefits for humans as well.

Thank you to these businesses and buildings for committing to Lights Out!

  • 101 California Street, San Francisco
  • Allsteel Inc., San Francisco
  • Barker Pacific Group, Inc. San Francisco
  • San Francisco Municipal Buildings and Agencies including:
    • City Hall
    • Dept.of the Environment, 1455 Market Street
    • Dept.of Public Works 25 and 30 Van Ness and 1680 Mission Street
    • Municipal Transportation Agency, One South Van Ness
    • San Francisco Planning Dept., 1650 and 1680 Mission Street
    • Public Defender, 555 7th Street
  • Tishman Speyer, San Francisco
  • Post Montgomery Associates, 1 Montgomery St. Ste. 2350