He did not account for radio towers, airport ceilometers, or, even, the other 50 percent of TV towers. Manville said that today's migratory birds have at least 80,000 towers to deal with, over 50,000 of which are lit. The greatest single night mortality recorded to date occurred in 1963. Kan. Unlit towers and their supporting guy wires clearly pose problems, especially during inclement weather. However, recent studies indicate that lit towers create an even greater threat.
Lighted towers appear to attract birds.
The effects seem to be much like moths attracted to lights. The birds begin to circle the tower. It's easy to picture the mass chaos and carnage. During peak migration there could be hundreds of thousands of migrants filling the night skies. As the migrants become attracted to, or disoriented by, the lights of the tower, they begin to circle the tower, creating a tornado of birds, circling and crashing into each other, the tower and the guy wires.