ABSTRACT— A vast and growing amount of evidence supports the interpretation that, except for habitat destruction, collisions with clear and reflective sheet glass and plastic cause the deaths of more birds than any other human-related avian mortality factor. From published estimates, an upper level of 1 billion annual kills in the U.S. alone is likely conservative; the worldwide toll is expected to be billions. Birds in general act as if sheet glass and plastic in the form of windows and noise barriers are invisible to them. Casualties die from head trauma after leaving a perch from as little as one meter away in an attempt to reach habitat seen through, or reflected in, clear and tinted panes. There is no window size, building structure, time of day, season of year, or weather conditions during which birds elude the lethal hazards of glass in urban, suburban, or rural environments.

The best predictor of strike rate is the density of birds in the vicinity of glass, and vegetation, water, and feeders best explain increased density and mortality at a specific site. Glass is an indiscriminate killer, taking the fittest individuals of species of special concern as well as the common and abundant. Preventive techniques range from physical barriers, adhesive films and decals to novel sheet glass and plastic, but no universally acceptable solution is currently available for varying human structures and landscape settings. Key Words: architecture, avian mortality, birds, glass, landscape, window-kill, windows.

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