I"m always surprised when I learn how few people realize Daphne du Maurier wrote the story that Hitchcock turned into a movie.

>> Of all the many short stories she wrote, "The Birds" is the masterpiece, in part, at least, because it provides no real explanation for the apocalyptic violence it depicts. https://www.theguardian.com/books/2007/may/05/fiction.daphnedumaurier