I suggest the title should say "Polychlorinated Biphenyls cause birds to sing a different tune". In the context of Hacker News, the title suggested to me that

I suggest the title should say "Polychlorinated Biphenyls cause birds to sing a different tune". In the context of Hacker News, the title suggested to me that someone had engineered a Printed Circuit Board that would interfere with birds' brains, perhaps by emitting magnetic fields to mess with their sense of north, or something.