Evaluating the relative effectiveness of patterns on glass as deterrents of bird collisions with glass

Studies documenting bird mortality from collisions with glass on buildings estimate hundreds of millions of birds die each year in North America from this cause alone. To reduce this mortality, it is essential to provide an objective assessment of the relative collision threat posed by glass and other materials incorporating patterns intended to deter collisions, similar to ratings for insulation value and breaking strength, for use by building professionals such as architects, engineers, planners, and other decision makers. We wanted to determine whether we could use a non-injurious binomial choice test developed in Austria, with local bird taxa in Pennsylvania, to provide objective collision threat ratings. Preliminary work in 2010-11 tested three patterns tested in Austria in 2004-6 and produced virtually identical scores leading to the conclusion that the test should apply generally to passerines. Additional trials indicated that variables including dimensions of pattern elements, spacing and orientation may interact in producing tunnel scores. The tunnel test has the potential to: a) determine how size, orientation and spacing of pattern elements impact collision-reduction effectiveness, b) rate commercially available glass, and c) evaluate new bird-friendly technologies. Keywords: Glass collisions, Bird collisions, Anthropogenic bird mortality, Tunnel test, Glass testing, Bird strikes