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Evolving Technology

UV daylight is visible to birds but invisible to humans.
(Source: NY City Audubon)

Ultraviolet (UV) Technology

Birds can see ultraviolet (UV) light, a part of the spectrum of natural sunlight that humans cannot see. They are able to detect the reflected UV light from the feathers and bills of other birds, from berries, seeds and the wings of insects, and (for raptors) in the feces and urine of small rodents. This heightened perception alerts birds to the presence of a potential mate or a possible food source, and helps them survive in their natural environment.

Emerging bird-deterrent technologies using UV light may ultimately provide the perfect answer to the bird-collision conundrum. UV windows would be transparent to humans but alert birds to the potential danger.

We have known for some time (Klem 1990) that to significantly reduce bird-window collisions, a pattern made up of visible elements to birds must uniformly cover the outside surface of a window, have strong contrast and be separated by no more than 10 cm (4 in) if oriented in vertical columns and/or by 5 cm (2 in) if oriented in horizontal rows. Besides this, a pattern offering a UV signal must reflect the UV strongly in the right wavelength range for a bird to see it. Birds’ ability to perceive contrast and depth of field are weak. Since their eyes are positioned on the sides of their head, they are keenly aware of what’s going on to their left and right (as they fly through a tree or dodge a raptor) but not necessarily what’s directly in front of them unless the visual signal they are getting is strong.

According to a study (Klem 2009), “a pattern offering a UV signal must have elements that reflect 20-40% UV over the 300-400 nm wavelength range, and be placed adjacent to complete (100%) UV-absorbing elements.” Reflecting the UV strength and breath of wavelength specified is essential for this technique to work, as anything outside of these criteria may be more hazardous to birds than conventional glass panes (Klem and Saenger 2013).

Three examples of window products that use ultraviolet technology are ORNILUX Mikado glass and GlasPro-Bird Safe Glass (mainly used for new construction) and WindowAlert (mainly used for existing construction.)

Photo: Ornilux


ArnoldGlas, a German company, has developed a bird protection glass called ORINLUX Mikado, which, according to their literature, prevents up to 71% of bird/window collisions. In ORNILUX panes, UV patterns are applied onto the second surface of glass (interior surface of the first layer of glass). However, a study concludes that the UV signal from ORNILUX Mikado is ineffective in alerting birds to the window hazard; the UV signal is simply too weak since it is not on the first surface of glass (Klem and Saenger 2013).

Photo: GlasPro - Bird Safe

GlasPro - Bird Safe Glass

GlasPro - Bird Safe also offers a UV treated glass applied in horizontal or vertical bands. These markers are sandwiched between two sheets of glass making them suitable for a variety of installations including transparent railing systems, noise and wind barriers, and public viewing settings.

Like most UV bird deterrent treatments, this product provides maximum transparency to achieve an unobstructed view. According to studies by the American Bird Conservancy, GlasPro - Bird Safe Glass exceeds their minimum standard for effective bird collision deterrent materials.


Klem, Jr. Collisions between birds and windows: mortality and prevention.
Klem, Jr. Preventing bird-window collisions.
Klem, Jr. and P. G. Saenger. 2013. Evaluating the effectiveness of select visual signals to prevent bird-window collisions.

Photo: WindowAlert


WindowAlert™, in decals and liquid form, has also adopted the UV concept. WindowAlert states that their decals help reflect ultraviolet light, while their UV liquid absorbs ultraviolet light. The reflected UV light is thought to be seen as a bright, iridescent glow to a bird’s eye, but is only barely visible to humans. Dr. Daniel Klem, Jr.’s research shows that it is the physical film that makes up the decal that the bird sees, not the UV signal, if that signal is not strong enough.

It’s more the smudge on the glass created by the drying of the liquid that birds see, not the UV itself in this instance. There are a few concerns regarding the stability of the liquid.

  • WindowAlert™ UV Liquid may be used only on an exterior glass surface – free of any overlay, tinting or coating.
  • While drying, UV Liquid can be contaminated by windborne dust or pollen. For best results, apply during calm weather with low pollen count.
  • UV Liquid will fade based on exposure and local elevation. Re-apply every 3 months.
  • According to WindowAlert™, UV Liquid contains Isopropyl Alcohol and Butyl Carbitol. These chemicals are known to cause cancer and birth defects or other reproductive harm.
Photo: Artscape

Bird's Eye View

Artscape offers a bird deterrent window film decal kit called Bird's Eye View. Similar to Window Alert, these geometric lenses are intended to refract UV light as a bird collision deterrent while offer an aesthetically pleasing appearance for humans. Artscape states that these decals are proven to be highly effective at reducing bird window collisions.

Again, it isn't the UV that is at work here, but rather the physical film itself that birds see. As these decals are designed for interior application and require the consumer to purchase numerous kits in order to achieve full coverage of their window(s), Artscape's claim that Bird's Eye View decals are highly effective is questionable. To learn how to make this product highly effective, consider adopting FLAP Canada's Visual Marker Standards.

UV Conclusion

Although UV technologies hold much promise as viable solutions to bird/window collisions, the effectiveness of existing products is being challenged by field studies. A great deal of research still needs to be done before they can be rolled out as a bird conservation/window collision panacea.

Photo: April Gocha

First Surface Frit

Glass with ceramic frit patterns embedded in it is one of the most popular bird-collision deterrents for new construction. Frit was originally designed to help reduce interior cooling costs while providing aesthetically pleasing patterns that complement a building. These markers are typically baked onto the second and/or third surface of glass. This choice of surface is designed to protect the frit from weather, pollution and cleaning, thereby prolonging the life of the marker.

Since it is more effective to place deterrent markers on the first surface, glass manufacturers are now exploring methods to apply first surface frit that can withstand exposure to the elements.

One company leading the way in this emerging technology is Goldray Industries. They have developed a bird friendly frit that is permanently fused to the first surface (outside surface) of glass.

CLICK HERE to learn about bird deterrent products that DO NOT work.

CLICK HERE to learn about emerging bird deterrent technologies.

CLICK HERE to learn about 'Do It Yourself" bird deterrent techniques.

CLICK HERE to learn about home bird deterrent products.

CLICK HERE to learn about bird deterrent techniques for new construction.

FLAP Canada Can Help

If you have questions or comments or need help with a unique bird/window collision problem, contact us at 416-366-3527(FLAP) or email We will be happy to help.

Make a donation to FLAP Canada and support bird-conservation efforts. Donors receive two issues a year of our newsletter, Touching Down, and periodic bulletins about our rescue and research work on behalf of birds.