A number of recent studies have demonstrated that many species of migratory birds are in a state of serious decline. The major reasons include the loss and degradation of habitat, introduced species, pesticides, predation by domestic and feral cats, oil spills and pollution. But most recently attention has focused on the issue of bird mortality from collisions with man-made structures, particularly with telecommunication towers. Because the Federal Aviation Administration requires that any structure over 199 feet in height be lit, tall towers pose the greatest risk to birds.
Most songbirds migrate at night using the stars as navigational aids.
Certain weather conditions lower the birds' visibility causing them to fly at lower than normal altitudes and bringing them into contact with towers and their support wires. It is conservatively estimated that 4 million birds are killed each year through collisions with towers. Although there are several studies that document localized impacts, better information is needed to determine the cumulative impacts of tower kills. In order for future research to be credible and useful, a standardized research protocol should be developed. It is hoped that the development of this research protocol will be facilitated by the recently established U.S. Fish and Wildlife Service's Tower Working Group.