Forty-four years of study reveal a number of historic accounts of birds striking windows, but no comprehensive investigations until the 1970s. Past and current investigations repeatedly document and validate that birds behave as if clear and reflective windows are invisible to them. Building upon the published works of the 1970s-1990s, current investigators have improved and further quantified annual estimates of avian mortality attributable to sheet glass and plastic, and the species, structure, and landscape settings involved in these unintended and unwanted strikes resulting in injury and death. The results of research addressing the evaluation of preventing bird-window collisions have revealed several effective methods, but additional short- and long- term solutions are needed to ensure the human-built environment is safe for birds worldwide.
Daniel Klem, Jr. is Sarkis Acopian Professor of Ornithology and Conservation Biology at Muhlenberg College in Allentown, Pennsylvania. Among other diverse avian investigations, for 44 years and continuing to the present he studies, writes, and teaches about the threat that sheet glass and plastic pose to birds. He is motivated by available and growing evidence that bird-window collisions are an important animal welfare, architectural, conservation issue for birds and people worldwide.