New Study Confirms: We can stop birds from dying at windows, and we already have the tools. In his 2025 paper “Bird-window collisions: a critical review” (The Wilson Journal of Ornithology), Dr. Daniel Klem Jr., the world’s leading authority on bird-glass collisions, reaffirms what decades of research have made clear: “Treating windows with visible patterning — following the 2×4 or 2×2 rule — provides 95–100% effective protection against bird strikes.” Across 90 countries and 1,740 species, from hummingbirds to warblers, the evidence is there: clear and reflective glass remains invisible to birds. These collisions contribute to billions of deaths annually. Dr. Klem highlights that vulnerable species in North America include the Golden-winged Warbler, Ruby-throated Hummingbird, Painted Bunting, and Wood Thrush, many of which are experiencing population declines. His message is urgent: “We humans know how and can stop birds from killing themselves flying into windows in the human-b...