found: Work cat.: The danger of plate glass, 2005:t.p. (birds strike our windows every day; more birds die because of collisions with glass than any other factor associated with human activity; from 100 million to 1 billion birds are killed by window strikes each year; bird collisions)
found: Avery, M.L. Review of avian mortality due to collisions with manmade structures, 1979:p. 5 (an estimated 80 million birds die each year from colliding with windows; window kills)
found: Trapp, J.L. Bird kills at towers and other human-made structures, 1998:introd. ("The bibliography focuses primarily on collisions with communication towers, lighted buildings, and (to a lesser degree) windows.")
found: Wikipedia, Nov. 6, 2009(Towerkill is a phenomenon in which large numbers of birds are killed by antenna towers. The U.S. Fish and Wildlife Service estimates that between 5 and 50 million birds are killed in the U.S. each year by towerkill. Window crashes, by comparison, kill between 100 and 900 million birds a year, and are still by far the largest human-related cause of bird death.)