"Silent Spring" caught the attention of many Americans. Before this not many worried about environmental problems and conservation. The book looked at problems with DDT and other pesticides (chemicals that kill pests, like mosquitoes and flies). It was thought these pesticides were safe, but they were actually causing many birds to die. DDT stayed in insects and fish which were eaten by birds. The birds then laid eggs with thin shells that would break. Some birds, like the Bald Eagle almost disappeared from the United States. In her book Carson said that without changes in how we use pesticides, there may not be birds left at some time in the future. Instead of hearing birds sing in the spring, it would be quiet, and that is how the book got its title.