In 1961, the good people of the small town of Capitola, California were terrorized by seemingly-insane seabirds. Eight people reported injuries and countless others ran in fear. Inspired by this strange event, along with an unrelated 1952 short story by Daphne du Maurier, Alfred Hitchcock brought the freaky scene to the big screen in The Birds. But here's the reality of what happened near the idyllic beach community of Santa Cruz. From Salon:
"Dead and stunned seabirds littered the streets and roads," reported the Santa Cruz Sentinel that very day, and the newspaper wasn't exaggerating[…] Since sooty shearwaters' diet is fish-based, this meant that partially digested anchovies were sprayed on citizens and property along with the feathers, feces and — even more mysteriously – the corpses of the aggressive avians themselves. When residents rushed out of their homes with flashlights so they could better see, the birds savagely swooped toward the light beams. The birds flew into television lines, caused power outages and littered fish skeletons all over the streets. The community was suffused in "an overpowering fishy stench," according to the Sentinel.
It wasn't until 2011 when Louisiana State University oceanographer Sibel Bargu Ates published a paper solving the mystery of what led the birds to behave so badly. It turns out, there was an abundance of a certain kind of diatom—a kind of plankton—that produces a neurotoxin called domoic acid. Unusually warm weather not only spurred the growth of the brain-altering plankton, it also delayed the birds' departure from the region. So the seabirds happily ate the diatoms and then, well, lost their minds.
The rest is cinematic history.