The Washington PostDemocracy Dies in Darkness

A viral video of birds falling from the sky sparked countless theories. But there’s a likely answer.

Yellow-headed blackbirds are migratory and travel south to Mexico from Canada and the northern United States during winter. (Ian Davies/Macaulay Library, Cornell Lab of Ornithology)

The residential street in Cuauhtémoc — a city in the Mexican state of Chihuahua, some 216 miles away from Texas — was seemingly quiet when, in one fell swoop, a cloud of birds suddenly dropped from the sky.

In a matter of seconds, most of the birds flew upward. But scores of others were left as black and yellow corpses on the ground.

The eerie and bizarre scene, captured by a surveillance camera on Feb. 7, has since gone viral. It has also sparked an online debate over what could have possibly caused the birds to so abruptly plummet to their deaths.

Security footage captured scores of yellow-headed blackbirds falling to the ground in Cuauhtémoc, Mexico, on Feb. 7. (Video: Alejandra Herlinda Iglesias Gonzalez via Storyful)

Theories being bandied about online range from electrocution after smacking into a power line to more outlandish suggestions, such as the interference of 5G technology or a collision with an invisible spaceship. A local zoo technician suggested the birds had died after inhaling toxic gas from the region’s high levels of pollution — driven by the “use of wood-burning heaters, agrochemicals, and cold weather in the area,” according to local outlet El Heraldo de Chihuahua, which first reported the story.

But what seems strange and ripe for speculation actually makes more sense by understanding biology, birds and their survival, experts said.

Kevin J. McGowan, an ornithologist at the Cornell Lab of Ornithology, said “the only thing that makes sense” was that the birds were fleeing from a predator — and some mistakes were made in their escape.

“This truly was an ‘oops’ moment for the birds,” he said. “A really big ‘oops’ moment.”

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The birds that were too late to hit the brakes in the video are yellow-headed blackbirds, a migratory species first described in 1825 by the nephew of French Emperor Napoleon Bonaparte. Their calls sound like a rusty door opening, with raspy “oka-wee-wee” sounds. Fleeing winter weather, the yellow-headed blackbirds jumble into massive flocks, McGowan said, making their way from Canada and the northern United States toward Mexico during the year’s colder months.

Chihuahua is a known location for these birds to winter. According to the Cornell Lab of Ornithology’s eBird program — a database compiling bird sightings from around the world — large flocks of some 3,000 yellow-headed birds have been spotted this year in the Mexican state. In 2010, McGowan said, over 30,000 were reported.

Known for their golden head and black plumage, the species flies with a sort of herd mentality, the ornithologist said. Without a clear leader, McGowan said the robin-sized birds “have the same goal so they agree to move in the same direction” — much like a school of fish or an angry mob.

When they are being attacked by a predator — such as falcons, hawks and owls, all of which inhabit Chihuahua — the birds inch closer together to create a tightknit pack.

“The big flocks can make these quick twisting motions, move together very quickly and they all are following the one right next to them who makes the most decisive move,” McGowan said. “They’re wingtip to wingtip in this tight bunch that makes it harder for the predators to actually pick out one and keep up with it.”

But their survival mode is not always foolproof. They can sometimes misjudge their speed or the distance from the sky to the ground — resulting in the uncommon, but not unheard of, visual of a flock of birds being dumped from the sky.

Other scientists agreed with McGowan. Richard Broughton, an ecologist at the UK Centre for Ecology and Hydrology, told the Guardian that the flock looked “like a wave at the beginning, as if they are being flushed from above.” Ronald L. Mumme, an ornithologist and biology professor at Allegheny College, said the birds dove, became disoriented, and many crashed to the ground and injured themselves,” Newsweek reported.

The reason the other theories do not pan out comes down to bird dynamics, McGowan said.

“Birds are light and fluffy, so they have a lot of wind resistance,” he said. “They don’t fall straight down very quickly, like a baseball. And in this case, they went flying down. It was a purposeful motion.”

If they had died in the air from inhaling poisonous gases — or even hit a spaceship — the birds would have tumbled down with a different motion and not risen again after crashing to the ground. Electrocution, as others have posited, is also an unlikely candidate. “I mean with that many birds, they would’ve taken out the power line completely,” McGowan said.

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There is also no evidence that birds are affected by 5G technology — that is, unless they crash into a network tower.

“There are a lot of conspiracy theories out in the world right now,” McGowan said. “This is weird and unusual, but it’s understandable when you put all the pieces of biology and put in a couple of what-ifs. We do find these accidents happening. Every organism out there is going to die and sometimes they die in weird ways. This was one of those weird ways.”

Now, for the thousands of yellow-headed blackbirds that survived and will make their way back north, the ornithologist had a piece of advice.

“Please be more careful,” he said.

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