A viral video of a flock of birds falling from the sky and slamming into pavement in Mexico made the rounds online last week, as experts are now explaining what really happened.
Security footage from Feb. 7 showed the flock of yellow-headed blackbirds suddenly fall to the ground in the Mexican state of Chihuahua, leaving dozens dead on the ground.
Most of the birds appeared to fly off after crashing into the roof of a house, but as the birds leave, you can see just how many were left scattered in the streets.
WARNING: GRAPHIC CONTENT
— Reuters (@Reuters) February 14, 2022
Security footage shows a flock of yellow-headed blackbirds drop dead in the northern Mexican state of Chihuahua pic.twitter.com/mR4Zhh979K
Dr. Richard Broughton, an ecologist with the UK Centre for Ecology & Hydrology, told The Guardian that he is certain the incident was caused by a predatory bird.
"This looks like a raptor like a peregrine or hawk has been chasing a flock, like they do with murmurating starlings, and they have crashed as the flock was forced low," Broughton said. "You can see that they act like a wave at the beginning, as if they are being flushed from above."
A veterinarian told the local newspaper El Heraldo de Chihuahua, who first reported the story, that the high-levels of pollution caused by "wood-burning heaters, agrochemicals, and cold weather" could have been a factor in the flock of birds falling from the sky.
Others online said that the birds could have been electrocuted while resting on power lines, and some even brought up a theory that 5G technology had something to do with it.
However, Dr. Alexander Lees, a senior lecturer in conservation biology at Manchester Metropolitan University, agreed with the theory there was a predatory bird flying after them and caused the incident.
"For my part and from one video and no toxicology, I’d still say the most probable cause is the flock murmurating to avoid a predatory raptor and hitting the ground," Lees told The Guardian.
Lees went on to explain how the flock of birds moves and why unexpected incidents like this may be frightening to see, but aren't uncommon in nature.
"There always seems to be a kneejerk response to blame environmental pollutants, but collisions with infrastructure are very common," Lees said. "In a tightly packed flock, the birds are following the movements of the bird in front rather than actually interpreting their wider surroundings, so it isn’t unexpected that such events happen occasionally."
Kevin J. McGowan, an ornithologist at the Cornell Lab of Ornithology, told The Washington Post that "the only thing that makes sense" is the birds were trying to escape a predator. He said that yellow-headed blackbirds migrate from Canada and the northern United States to Mexico during the winter, and added that Chihuahua is a popular location for these birds in the colder months.
The Cornell Lab of Ornithology’s eBird program reported that nearly 3,000 flocks of yellow-headed birds have been spotted in the Mexican state, as McGowan said that there were over 30,000 reported in 2010. He then explained how these birds fly in a large group.
"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."
McGowan added that the incident was no accident, saying that the birds flew downward with a purpose.
"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."
Despite all of the theories online as to why the birds slammed to the ground, McGowan said that's just part of nature sometimes.
"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."
