The need for “bird-friendly” glass is increasing significantly. More and more cities, provinces and states are aware of the impact a glass building façade can have on bird collisions. As more focus is put on how to design safer buildings for birds, it is also important to understand the metrics used and how glass is tested to obtain performance data.
According to The Wilson Journal of Ornithology and The American Bird Conservancy (ABC), two main methods are used to test the effectiveness of bird deterrent treatments for glass. ABC is using a flight cage or tunnel test, consisting of a long wooden rectangular cage or tunnel where the light comes from only one end. This opening has 2 sides, one which is obstructed by the material being tested, and the other has a control sample. Birds are released into the cage, and are observed. If the bird goes towards the obstructed side, it is marked as a strike and if they fly towards the unobstructed side it is scored as avoidance. (Please note that there is a fine net in front of the glass to prevent the birds from actually colliding into the glass).
On the other hand, Professor Daniel Klem conducts field experiments, to evaluate the effectiveness of bird safe glass. The method uses wooden-framed windows with the glass material being tested, simulating those in houses, which are placed on a 2 hectare area of mowed pasture bordered by forest and shrubs. A bird feeder is placed 30 feet in front of each window and the flights of individual birds moving from the feeder toward the windows are recorded and assessed. The field experiment test is conducted over a period of 90 days. This method is perceived to be more reliable in evaluating bird collision prevention methods, because it better reflects actual glazing solutions in buildings.
To this date, results from these tests indicate that patterns on glass panes are only effective if spaced two to four inches apart. Moreover, methods used to prevent bird collisions that are applied to surface one are most effective. This coincides perfectly with the use of acid-etched glass on surface one, a solution brought about by the Textures AviProtek product line.
Test protocols will continue to evolve in an effort to best replicate the use of actual glazing solutions on building façades. For example, the next generation of tunnel tests will be done with glass being front-lit, as opposed to being back-lit.
Test results on glass panes fully etched or with a pattern meeting the 2” x 4” rule, show threat factors lower than 30, the threshold established by ABC to determine if a glass product is bird safe or not.
Based on the above information, Walker Textures® acid-etched glass products offer a very effective bird friendly solution. Glass continuously etched on interior (#2) surface of an IGU, offers a threat factor of 25, and glass continuously etched on the exterior (#1) surface of an IGU has a threat factor of 5. The Textures AviProtek acid-etched patterns, applied on surface 1 are also quite effective, with threat factors under 30, while offering nice viewing areas.