Home / Solutions / Bird-Safe Film
This is the one film product on this site where the pattern generally belongs on the outside of the glass, not the inside — the opposite of how most window film gets installed. Put that same pattern on the inside of reflective glass and the reflection can hide it for part of the day, or all of it. We'd rather explain that upfront than have you find it out after the markers are already on the glass.
What Actually Happens
A window doesn't read as a barrier to a bird the way it does to us. Clear glass can look like open sky or the continuation of a hallway or courtyard beyond it; reflective glass can mirror back trees or sky convincingly enough that a bird flying toward it is flying toward what looks like open air. Either way, the bird doesn't slow before impact, because as far as it can tell, nothing is there.
The peer-reviewed estimate comes from Loss et al. (2014, The Condor 116:8–23): 599 million birds killed annually by building collisions in the United States, within a 95% confidence interval of 365 to 988 million. We are being precise about that figure on purpose, because this industry rounds it up. The number quoted across vendor pages — and, inconsistently, on some conservation organizations' own public-facing pages, even where their own technical documents cite the study correctly — is "more than 1 billion." That sits above the published upper bound of the study it gets attributed to. We will use the number the research actually supports.
That same study contains a finding that matters more to a commercial building owner than the headline does. The mental image is a mirrored high-rise downtown. The U.S. Fish and Wildlife Service, summarizing this research in its own best-practices document, corrects it: "While most people consider bird-glass collisions an urban phenomenon involving tall, mirrored-glass skyscrapers, the reality is that 56% of collision mortality occurs at low-rise buildings (i.e., four to eleven stories), 44% at urban and rural residences, and <1% at high-rises." The ordinary four-to-eleven-story building — an office, a school, a hospital wing, a retail box — is where most of this happens.
Where The Pattern Goes
This is the spine of the page, so we're leading with it instead of burying it in a spec sheet.
ABC's own consumer guidance is direct about this: "The best place to apply solutions is on the outside of the window, where they are easily visible." The reasoning is physical, not aesthetic. ABC's rating documentation explains why an interior-surface pattern can fail even when it's correctly spaced and sized: "Strong reflections can reduce pattern effectiveness by obscuring the visual markers during part or all of the day, if the pattern is on an inside surface of the glass." A bird looking at reflective glass from outside isn't looking through it to a marker on the far surface — it's looking at a mirror, and the mirror can hide the pattern, depending on the light.
ABC builds that physics into its rating rules rather than leaving it as advice. A pattern on the exterior surface of the glass has "no limit on VLR" — the glass can be as reflective as the project wants. A pattern on the interior surface only qualifies if reflectance is capped at 15% VLR, and even then ABC states it does "not test materials with greater than 15% reflection (VLR) at the exterior surface of the glass, unless the visual markers are on the outside surface, or our BirdVis app ... shows that there is sufficient contrast for markers to show through reflections." Reflective glass and an interior pattern don't reliably go together, and the body that tests these products says so in its own criteria.
Guidance is one thing; a controlled experiment is better. In 2023, Swaddle and colleagues published a study in PeerJ that tested two commercial bird-deterrent window films applied first to the outside and then to the inside of double-glazed windows. Applied externally, the two products increased window avoidance by 47% and 39%. Applied internally, neither produced a measurable benefit. The authors' conclusion is unusually direct for a journal: "it is imperative that installers apply these products to exterior surfaces of windows to render their protective benefits and reduce the risk of daytime window collision."
That cuts against the default. Most of the window film this company installs — solar control, security, decorative — goes on the inside of the glass, where it's protected from weather and easier to service. Bird-deterrent markers are the exception, and if the outside surface is available, that's where the pattern belongs. We'll say so before we quote the job, not after.
Pattern & Spacing
Early collision-deterrent guidance, based on research by Klem (1990) and Rössler et al. (2007), called for horizontal lines spaced 2 inches apart and vertical lines spaced 4 inches apart. ABC's rating documentation explains what changed: "subsequent monitoring showed that the 4" spacing does not stop collisions by the smallest birds, especially hummingbirds." So the wider dimension closed: "Two inch (5 cm) spacing for two-dimensional patterns on glass or window film is now typically recommended in Canada (Canadian Standard A460) and increasingly in the United States. Thus, what was once the '2x4 rule' is now the '2x2 rule'." ABC also notes 2x4 spacing "has been demonstrated to reduce collisions significantly and materials based on that guideline can still receive a 'bird-friendly' TF rating" — a step down from 2x2, not a disqualification.
ABC's consumer version: "make sure to eliminate all spaces larger than two inches." Spacing alone isn't the whole test — the pattern also has to be visible in time for a bird to react: "whichever material you use needs to be visible to birds from at least ten feet away so that they have time to see the material and change course." ABC's technical criteria set the equivalent standard more precisely, adopting "9'-9' ½" (3 meters) as the standard viewing distance from which birds must be able to detect the pattern, following Ros et al. (2017)."
For an opaque, 2-inch-spaced pattern, ABC's prescriptive marker minimums specify: "Continuous solid lines at least 1/8" wide (~3mm), nowhere more than 2" apart, measured edge to edge." For dot or shape patterns: "Circular, square, or irregular solid shapes that are nowhere more than 2" from another shape, measured horizontally or vertically, (edge to edge) and 2.83" diagonally ... Each shape must have a minimum area of ≥ 0.20 in2, which corresponds approximately with circles of diameter ¼" (~6mm)."
Whether a pattern looks visible to a person standing at the glass is not the test. ABC's documentation is explicit that "birds, particularly small birds like songbirds, have very poor visual acuity in comparison to humans. Therefore, a pattern that appears quite visible to us may not be apparent at all to birds." The spacing and sizing spec exists because "I can see it" isn't a reliable stand-in for what a bird can see in flight.
How Products Get Rated
ABC rates materials using what it calls a tunnel test — "a non-injurious, standardized binomial choice technique that uses wild songbirds." A bird is released down a dark tunnel toward two panels at the far end: one a clear control, one carrying the test pattern. A net stops the bird before it reaches either panel. Across a minimum of 80 birds flown, ABC records the percentage that fly toward the test pane rather than the clear control — the Specimen Performance Index. With no other data adjusting it, the Threat Factor equals the SPI.
ABC's own definition of the pass line: "ABC defines 'bird-friendly' materials as having a threat factor ≤ 30, corresponding to a conservative estimated reduction of collisions of at least 50% under real world conditions." The scale runs the opposite direction from what you might expect at first: "The lower the Threat Factor, the more effective the tested material will be at reducing collisions." It also isn't a straight-line scale — ABC is explicit that "one cannot say that a pattern with TF=15 is twice as effective as a pattern with TF=30."
Not every pattern needs a dedicated tunnel test. ABC assigns prescriptive Threat Factors to opaque patterns that meet its spacing criteria on their own:
| Opaque Pattern On Glass | Threat Factor Assigned |
|---|---|
| 2" x 2" spacing | 20 |
| 2" x 4" spacing | 25 |
| Under 2" spacing | 25 |
| Unpatterned façade / spandrel meeting ABC's surface criteria | 25 |
Lower is better, and ABC's bird-friendly threshold is ≤ 30 — all four of the prescriptive ratings above qualify. That's a useful shortcut for a spaced marker pattern that matches one of these rows: it doesn't need a lab test of its own to carry a bird-friendly rating.
What A Rating Doesn't Promise
Marketing in this category often leads with a headline collision-reduction percentage. Here's the honest version, in ABC's own words.
ABC — the organization that runs the tunnel test these ratings come from — says plainly in its own documentation that a Threat Factor doesn't travel with a promise: "SPIs and TFs do not warranty the actual percent reduction in collisions to be expected when a product is installed on a building. In fact, the same product may perform better or worse due to facade orientation in the same building, façade detail creating traps or channels, habitat reflected, whether the glass is free-standing and other variables."
A Threat Factor is a relative tunnel-test index — a way to compare one pattern against another under controlled conditions — not a guaranteed reduction on your building. Facade orientation, what the glass reflects, and how the openings are configured all move the real-world result, in either direction, from what the lab number suggests. A vendor page that states a single collision-reduction percentage as a fixed property of the product is stating more certainty than the body behind the test claims for it.
Field data gives you the honest order of magnitude. The largest real-world test of an exterior dot marker published to date — Lawson et al. (2026, Ornithological Applications), covering six treated façades on two university buildings — measured collision rates falling 67.2% to 71.6% at the treated façades, while collisions at untreated façades on the same buildings rose 15.7% over the same period. An earlier study using the same markers reported 71%. Set that against the 94%-and-up figures that appear on product pages. The researchers themselves explain the gap: Swaddle and colleagues caution that "our computed metrics from binary choice trials overestimate collision reduction," having measured 75–90% in forced-choice trials but only 30–50% under more ecologically realistic conditions. A two-thirds to three-quarters reduction is a real, defensible, worthwhile result. It is also not the number on the brochure.
One more thing to check, because it comes up in specifications. There is no published ASTM consensus standard for bird-friendly glazing. A tunnel-test method has been under development as an unpublished ASTM work item, but it carries no standard designation. If a product sheet or a spec cites an ASTM number for bird-safe glass, ask which standard it is — ASTM E3199, the number that circulates in this context, is a life-cycle-assessment guide on recycling allocation and has nothing to do with birds or glazing. The consensus standard that does exist for bird-friendly building design is Canadian: CSA A460.
ABC puts it more bluntly still on its own product database: no product can be guaranteed to stop all collisions in real world conditions. If a product page offers you a guarantee that collisions will be eliminated, it is promising something the testing body behind the rating explicitly says cannot be promised.
Warranties deserve the same scrutiny, because in this category they do not line up with the marketing. It is common to find a manufacturer's own written data sheet warranting a term several times shorter than the lifespan claimed on its product page for the same product. That gap matters here more than with interior film, because an exterior-applied marker system lives in UV, rain, wind-driven grit and whatever gets used to clean the glass. Ask for the written warranty term specifically for exterior application, and ask what the cleaning restrictions are, because those two answers set your real reapplication cycle.
So ask a supplier for specifics, not a headline: the tested pattern and spacing, the assigned Threat Factor, and whether the tested configuration matches the surface — interior or exterior — and the glass reflectance you actually have. Those answers tell you whether the rating applies to your building. A percentage on a brochure doesn't.
California Requirements
There are a lot of "cities that require bird-safe glass" lists circulating in this industry. Most of them mix adopted ordinances, proposals, staff reports and voluntary guidance together. What follows is drawn from adopted code text.
Start with the statewide answer: California has no enacted state law requiring bird-safe glazing on private buildings. What exists statewide is CALGreen Appendix A5.107, "Bird-Friendly Building Design" — and Appendix A5 is the voluntary nonresidential section of the code. It binds a project only where a local jurisdiction has adopted it as mandatory. Where it does apply, it reaches "a newly constructed building, or an alteration of an existing building that includes the addition or replacement of 50 percent or more of the exterior glazing," and it asks for bird-friendly treatment on no less than 90% of an elevation from grade to 40 feet, and 60% above that.
A5.107 uses the 2x2 rule — quarter-inch dots or eighth-inch stripes at 2-inch maximum spacing horizontally and vertically. Worth knowing if someone tells you otherwise: the state's voluntary standard expressly permits interior glazing film with 2x2 markers, and allows patterns on glass surface 2 with the note that "they can be effective if visible behind an exterior surface with reflectivity of 15 percent or less." The code permits interior application. The research in the section above is why we still recommend the exterior surface where it is available. Those are two different questions, and we would rather you hear both answers than only the convenient one.
Below the state level, the requirements are local, and they are concentrated in the Bay Area. These are the jurisdictions where we confirmed an adopted ordinance, with the trigger that matters most for retrofit work — whether the rule reaches a building that already exists:
| Jurisdiction | Adopted | Does it reach existing buildings? |
|---|---|---|
| Emeryville | 2020, amended 2024 | Yes — any replacement window 12 sq ft or larger, citywide |
| Palo Alto | Ord. 5695, effective 2026 | Yes — substantial remodel, or any new fenestration |
| Cupertino | 2021, amended since | Yes — remodels, and any new or replacement glass |
| Berkeley | 2023 | Yes — replacement material on existing buildings, grade to 100 ft |
| San Mateo County (unincorporated) | 2026 | Yes — additions, and replacing 50%+ of exterior glass |
| Mountain View | Ord. 9.2025, effective 2026 | Yes — 50%+ of exterior glazing, buildings 10,000 sq ft and up |
| Alameda | 2018 | Limited — replacement windows 12 sq ft+, only buildings over 35 ft with a glass-dominant façade |
| San Francisco | Planning Code §139, 2011 | Limited — 50%+ glazing replacement on a designated hazard; the code states the controls "do not apply retroactively" |
| Santa Cruz | 2022 | Limited — façade alterations requiring a planning permit |
| Oakland | Condition of approval, revised 2025 | No retrofit trigger |
| Richmond | 2016 | No retrofit trigger |
| Menlo Park | 2016, amended 2018 | No retrofit trigger |
Now the part most vendor pages leave out. We could not find a bird-safe glazing requirement anywhere in Los Angeles or Orange County. We ran full-text code searches for Los Angeles County, Orange County, Irvine, Pasadena and Long Beach citywide and found nothing in any of them. We will be straight about the limit of that: a few smaller Southern California cities keep their municipal codes behind hosts we could not search, so we are not going to claim the answer is no for every city in the region. We looked, we found nothing, and you should confirm with your own planning department before anyone bills you for compliance work. The City of Los Angeles had a draft in progress under its Wildlife Work Program; City Planning's own page now states that the adopted 2025–2026 budget eliminated the funding for that program and it "will be discontinued." Long Beach has a bird-safe provision, but it sits inside one specific plan covering the southeast area of the city, not the city as a whole. If you own a building in our home market and someone tells you this is code-required, ask them to name the section. In LA and Orange County this is a voluntary choice today, and we are not going to sell it as anything else.
On which surface the code demands: be careful here too, in both directions. Only Cupertino requires the treatment be "applied to the outermost surface" without qualification. Mountain View requires it for film specifically. Palo Alto asks that film "be applied to the outer surface to the extent possible," and permits film only on residential buildings or on nonresidential elevations below 35 feet. Oakland expressly allows "the interior or exterior" of the glass. Every other jurisdiction we checked is silent on the point for film. So an installer claiming a Bay Area ordinance forces exterior film is usually overstating it — and an installer using that silence to argue interior film performs as well is ignoring the research. The code sets the floor. The physics sets the outcome.
On Threat Factors in law: Berkeley is the only California jurisdiction we found that writes a number into adopted code, requiring a product with an American Bird Conservancy Threat Factor rating of 30 or less. Palo Alto and Santa Cruz name ABC as an approving body or product source without attaching a number. CALGreen does not reference Threat Factors at all. Nobody should represent a Threat Factor number as a statewide code requirement, because it isn't one.
Bird collision deterrence is also recognized within the LEED rating system — ABC's documentation states that Threat Factors "made it possible to create a credit for reducing bird collisions in the LEED rating system," and ABC describes the original pilot credit as having since moved into the permanent innovation credit library. We are not going to print a credit number, a point value or a current status here, because we could not verify the live credit language against USGBC directly. Confirm the current credit and its requirements with USGBC for your rating-system version.
Codes change, and several of the ordinances above were amended recently. Treat this as a starting map, not a compliance opinion — confirm the current requirement with the planning department that has jurisdiction over your building before you specify anything.
Where We Fit
We install bird collision-deterrent marker systems as a film and glazing retrofit, on glass already in the building. We do not replace glass, windows, doors, or storefront systems — that's outside our scope. Since most of the California ordinances above trigger on new construction or glass replacement rather than an existing building left alone, new-construction glazing compliance is a different scope from what we do, and if that's what your project actually needs, we'll say so rather than stretch our own scope to fit.
What we can do is walk your building's glass, tell you honestly which openings are candidates for an exterior-surface marker pattern, and get you a written specification — the pattern, the spacing, the surface it goes on — before anything is installed. We're brand-agnostic on the marker product; we're not an authorized dealer for any specific bird-deterrent brand, and we won't imply otherwise. What we'll give you is the criteria to judge any product against, and an honest read on your building.
Questions
Not reliably on reflective glass. ABC's own guidance is that the best place for the pattern is the outside of the window, and that strong reflections can hide an inside-surface pattern for part or all of the day. ABC's rating criteria reflect the same physics numerically: an interior pattern is only accepted with glass reflectance capped at 15% VLR, while an exterior pattern has no VLR limit. If the outside surface is available, that's where it belongs.
No — ABC's own consumer guidance says a single decal may be enough to warn an alert human to expect a glass door, but for a bird it's simply an obstacle to fly around. The reason follows the spacing rule: one sticker or silhouette leaves gaps far larger than two inches across the rest of the glass, and a bird in flight reacts to open space, not to a single marker.
ABC's marker minimums describe a spaced pattern, not a solid coating: continuous lines at least 1/8" wide, no more than two inches apart, or small solid shapes with a minimum area of about 0.20 sq. in. — roughly a quarter-inch circle — spaced the same way. That's a grid of thin lines or small dots, not a full frosted surface.
No. Every California jurisdiction we could confirm against adopted code text — San Francisco, Oakland, Richmond, Menlo Park, Alameda, Emeryville, Cupertino, Santa Cruz, Berkeley, Mountain View, Palo Alto and unincorporated San Mateo County — is in the Bay Area or on the Central Coast. We ran full-text code searches for Los Angeles County, Orange County, Irvine, Pasadena and Long Beach citywide and found no bird-friendly glazing requirement in any of them. A few smaller Southern California cities keep their codes behind hosts we could not search, so confirm your own city with its planning department rather than taking a blanket “not required” from anyone, us included. California's statewide CALGreen provision for bird-friendly design sits in the voluntary appendix of the code and binds a project only where a local jurisdiction adopts it. In Los Angeles and Orange County this is a voluntary choice today, not a code requirement.
That depends which surface the solar film is on and which surface the bird pattern needs. ABC's guidance points the marker pattern to the outside of the glass — a different surface than where solar film is typically installed — so the two usually aren't competing for the same surface. Where a pattern does need an interior surface, ABC's criteria cap that surface's reflectance at 15% VLR — check whether solar film has pushed reflectivity above that before assuming a pattern will work there.
Keep Reading
Applied patterns, frosted effects and printed film — the product family a bird-deterrent marker pattern belongs to.
See the options →Reflectivity is what makes glass invisible to a bird. Here is what solar film does to a window and how reflectance is measured.
See the spec →The questions that separate two quotes that look identical on paper — product, spec, attachment and who actually does the work.
Read the checklist →Free site assessment across LA & Orange County. We'll tell you which openings are film candidates, which need anchored attachment, and which need a different answer entirely.