When Hitchcockian horror came true: The 1960s killer bird swarm that inspired "The Birds"

Sixty years ago in March 1963, Alfred Hitchcock's classic horror movie "The Birds" introduced viewers to a small seaside town in California that is suddenly and inexplicably attacked by ferocious feathered fiends. Ostensibly based on a 1952 short story by Daphne du Maurier, "The Birds" features seagulls, crows and a range of other bird species as they ruthlessly slash at terrified humans with razor-sharp beaks and talons. The high concept flick was a box office hit and is widely considered to be one of the greatest creature features ever made.

Yet while du Maurier's short story is certainly worth a read, Hitchcock was also inspired by a real-life tale in many ways more bizarre than its fictional counterpart. Like "The Birds," it was set in early 1960s rural California — Capitola, to be exact, which is adjacent to the Monterey Bay (in the movie, the action is set in Bodega Bay). Just like the characters in the film, the real-life residents of Capitola in 1961 were shocked when swarms of birds attacked them out of nowhere. Yet unlike the movie — in which no explanation for the birds' behavior is ever supplied — there is actually a plausible scientific explanation for why the Capitola birds seemed to declare war on the nearby humans.

When residents of Capitola woke up that foggy early morning on August 18, 1961, they were greeted by flocks of birds dive-bombing into their houses. Although a number of species were involved, the majority of the birds were later identified as sooty shearwaters, which are usually harmless to humans and instead are best known for acrobatically diving into waters for fish. As their name indicates, sooty shearwaters have a gray-and-brown palette that makes them rather unremarkable visually; if a seagull's wings were stretched out, and it rolled around in a chimney or fireplace, it would look something like a sooty shearwater. Yet the same aerial skills that made sooty shearwaters into nightmares for fish were suddenly being employed against humans. In addition to crashing into buildings, the hundreds and hundreds of birds were tumbling through the air as if they were drunk on a bender.

"Dead and stunned seabirds littered the streets and roads," reported the Santa Cruz Sentinel that very day, and the newspaper wasn't exaggerating. In addition to living out a scene that would later become iconic (albeit with pigeons) in the schlocky 2003 sci-fi movie "The Core," the sooty shearwaters had also drenched Capitola in vomit. 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.

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Eight people reported being bitten by the birds, and it seemed that every resident had a story. An officer using a sheriff's car nearly crashed as sooty shearwaters plowed into his vehicle. A teenager was struck by a bird as he left his house. One oblivious resident was surprised by a swarm of angry birds when she blearily opened her door at 6 AM; although she succeeded in keeping them out of her house, she did not manage to do so before they sprayed her residence with their bodily fluids. "The smell is terrible," she complained, noting that the birds had vomited fish guts all over her lawn.

Yet residents also took pity on the birds, expressing distress at the ones who had died and trying to help those who seemed merely confused. Perhaps it was unsurprising that reporter Wally Trabing closed his account with a quick reference to Hitchcock taking an interest in the then-recent events. Trabing had earlier noted that only one demographic seemed happy: "Cats were drawn to the area and were running about the areas."

So what happened? While Hitchcock would never live to discover the truth, Dr. Sibel Bargu Ates — an oceanography professor and Associate Dean of Academics at Louisiana State University's College of the Coast and Environment — cracked the mystery in a 2011 paper to the scientific journal Nature Geoscience. As it turns out, there is a neurotoxin called domoic acid that can be produced by a diatom (a form of microalgae), which in turn is part of the diet of animals preyed upon by birds like sooty shearwaters.

"Pseudo-nitzschia [was in] abundance during the summer of 1961 [and] was of the same order of magnitude as that observed during more recent animal stranding events related to domoic acid poisoning," Bargu told Salon by email. "The upwelling of bottom waters declined at the time, and the inflow of oceanic surface waters increased, probably leading to the development of warm water and low-wind conditions." Not only did this cause the seabirds to stay in California for longer than usual — they breed in the Southern Hemisphere in nations like New Zealand — but it promoted the growth of this neurotoxin at precisely the wrong time.

"Therefore, we think toxic Pseudo-nitzschia were probably responsible for the odd behavior and death of sooty shearwaters in August 1961," Bargu told Salon. In addition to the obvious vomiting, symptoms of poisoning with this neurotoxin include "confusion, disorientation, scratching, seizures, coma and even death."

And what about the events in "The Birds"? Hitchcock may have been a talented filmmaker, but did he get the science right? Could birds poisoned by a neurotoxin really join together in cross-species flocks, coordinate attacks on humans, swoop down chimneys in orderly procession, intentionally break through windows and even figure out how to blow people up?

In a word: No.

"I love the movie, and it was very scary to watch when I was young," Bargu told Salon with a smile. "But none of the birds' 'intentional' actions featured in the movie are accurate and they are not possible." Bargu even dismissed the film's ornithologist character, who describes birds as being inherently non-violent.

"Animals' 'violent' actions are not originating from 'they do it because they think it is fun, entertaining etc.,'" Bargu wrote, but they still "may be aggressive at times because they feel a threat to their survival, their offspring, their clan, etc."

Still, what happened in 1961 was not a one-off. Nature could still create its own real-life sequel. 

"Yes indeed," Bargu told Salon when asked if there could be another mass domoic acid poisoning. "Three decades later, in 1991, another mass poisoning occurred in the same area — this time, of fish-eating, disoriented, and dying brown pelicans. And another one in 1998, another one [in the] 2000s. . ."