The industry moves quickly to quell what it insists are unsubstantiated claims that the signals cause cancer. Federal regulations do not allow communities to ban cellular towers except in rare cases, so the industry hardly ever loses such battles, but it would rather avoid them. But another battle may emerge over the flashing warning lights atop some towers that may endanger migrating birds. Somewhere between 2 million and 40 million migratory songbirds die each year when they are confused by broadcast tower lights, scientists say. The birds swirl around the towers, colliding with guy wires, each other, or the ground.
Some scientists believe the signals scramble the birds' navigational senses.