To call his mate, a male Adélie penguin uses a tried-and-true formula: flap flippers, tilt head to sky, then cut loose with a braying screech of a love song. It’s called an ecstatic call, and among penguins, it’s contagious. “One starts, and pretty soon everyone’s doing it,” said ecologist David Ainley. Ainley, who studies Adélie colonies in…