Enviros estimate that more than 4 million migrating birds are killed each year in the U.S. as they collide with communications towers, and the problem is becoming more severe as thousands of new towers crop up to serve cell phones and digital pagers. Bird conservationists are particularly worried about new mega-towers that will be constructed over the next three years for digital TV, some of which could reach the height of the Empire State Building. The U.S. Fish and Wildlife Service plans soon to issue voluntary construction guidelines for tower height, location, and lighting that would help curb bird deaths, but it’s unclear how willing the communications industry will be to spend the extra money necessary to make its towers more bird-friendly.