Review of Avian Mortality Due to Manmade Structures, by Michael L. Avery.
Daniel Klem in 1979 estimated 80 million birds killed per year or about one per building in the US, even though some buildings kill many more than one bird. That year, R. C. Banks put the number at only 3.5 million birds per year.
We think Klem's number is too low, and in any event there are many more buildings exist in the US now than did in 1979. Klem's calculation came in his doctoral dissertation at Southern Illinois. He has devoted a great deal of time and research effort to the topic of bird collisions since then.
Klem's work suggested that bird kills from collisions with buildings happen at all seasons and involving both clear glass and reflective glass. All kinds of birds run into buildngs and die---young and old, many species.
In addition, many other kinds of structures kill birds, including antenna and broadcast towers (and their guys) and overhead power lines.
Daniel Klem is currently working on a study for New York City Audubon using the Project Safe Flight data tht the volunteers have collected.
For many years, the effects of manmade structures on birds have been known. It has taken a long time for humans to take notice of these effects on the natural world.