No product can be guaranteed to stop all collisions in real world conditions. Glass can vary in appearance from one façade of a building to another or with time of day, depending on solar angle, reflected environment and other factors. The Threat Factor number is determined under standard conditions and does not capture that variety. Instead, Threat Factor is a relative index, and products with lower TFs are considered more effective at preventing collisions. A TF of 30 suggests that collisions will be reduced by at least 50 percent and is ABC's upper threshold for recommending a product. Products with UV patterns should be considered carefully for some applications: Materials with ultra-violet patterns will vary in effectiveness with the amount of UV light present. This means that when the UV index is low – under low light conditions in early morning or evening or if the glass is shaded, or when it is overcast – UV patterns will be less visible to birds. In addition, not all types of birds can see UV. For example, songbirds can see UV, raptors and pigeons cannot. Because Threat Factors can be effected by low-e coatings, published Threat Factors apply only to the glass assembly tested.
Prescriptive rating
Stained glass in general is very bird-friendly, as well as serving purposes of devotion or decoration. There is even photovoltaic stained glass! However, if a stained glass panel is insulated, by mounting an external ‘storm window’, it is important to make sure that reflections from that panel of glass don’t cause collisions.
Non-adhesive, easy to apply and remove; 2x2" spacing recommended. Although field tested on the inside surface by Dr. Daniel Klem, this was on uncoated window glass. ABC recommends them on the exterior surface only.
These decals, intended to be applied to the inside of the glass, have only been tested on ordinary window glass and may be less effective on windows with reflective coatings. 2x2" spacing is recommended.
Place decals using 2"x2" spacing guidelines
Decals applied to the outside of the glass can be very effective, if applied with 2x2" spacing. Apply to the exterior side of the glass, first cleaning the surface. Many commercial window cleaners leave a residue that can interfere with adherence. We recommend using a 50% water/50% rubbing alcohol solution. Make sure the glass surface is completely dry before installation.
Use non-toxic paint to put up pattern or picture using 2x2" spacing guidelines
Tempera is a quick, inexpensive solution for collisions. It can be applied casually, or with a stencil , to the outside of the glass. You could create different patterns for every holiday. Patterns last a surprisingly long time, even after rain, but can be removed almost instantly.
Use non-toxic paint to put up pattern or picture using 2x2" spacing guidelines
Paint of all types can provide inexpensive, long lasting and highly effective solutions for glass collisions. Plan carefully for acrylic or oil paint, as they may be difficult to remove.
Image drawn on outside of window, using oil-based pen
Painted images can be excellent collision deterrents but must follow guidelines for spacing and other pattern elements to be effective. The pattern shown here meets basic spacing criteria and monitoring at the University has shown it to be successful at reducing collisions.
Recommend installation with 2" x 2" spacing
Prescriptive evaluation; reflection test
External insect screens eliminate problem reflections and reduce impact if a bird does hit a window. Screens should cover the entire glass area of a window and should be mounted at least one inch away from the exterior surface of the glass.
Prescriptive; reflection test
Stucco, concrete, brick and stone with a matte finish should be safe for birds in any application.
