The Birds, the jaw-dropping thriller that has spooked the nation since 1963, was inspired by a real - and equally eerie - event. The mystery that prompted Alfred Hitchcock to make the film has been solved: The birds had ingested a toxin that caused them to act strangely. In 1961, two years before the debut of one of the freakiest films in history, hoards of disoriented seabirds rammed themselves into the sides of homes in the Monterey Bay area.