Hundreds of yellow-headed blackbirds were caught on camera appearing to fall from the sky, some of them dying, in a mysterious event that occurred in the northern Mexican city of CuauhtÃ©moc.
The graphic footage, captured by a surveillance camera, shows the flock of migratory birds descending on to houses like a cloud of black smoke.
While most birds manage to fly off after "crashing down," subsequent footage shows carcasses of the birds scattered across the street, which local newspapers described as a scene similar to a horror movie. Watch the video below:
The incident happened on the morning on 7 February, according to local reports. The birds tend to breed farther north, in the US and Canada, and migrate south for winter in Mexico.
Expert Claims Flock of Birds 'Flushed' by a Predator
According to local news outlet El Heraldo de Chihuahua, a veterinarian believed the strange occurrence took place due to high levels of pollution, driven by use of wood-burning heaters, agrochemicals and cold weather in the area. Another possible explanation was that the birds were electrocuted while resting on power lines. The video even fueled conspiracy theories that the birds fell from the sky due to 5G technology.
The cause of death still remains unclear but now experts are claiming it may have been caused by a predatory bird swooping down to make a catch. As reported by The Guardian, Dr Richard Broughton, an ecologist with the UK Centre for Ecology & Hydrology, said that although a raptor was not visible in the footage, he was 99% sure it was caused by a predatory bird.
A predator could have made the birds swirl tightly in a flock and driven them towards the ground, with higher birds forcing lower ones to crash into the buildings or the ground.
"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," he said. "You can see that they act like a wave at the beginning, as if they are being flushed from above."
Dr Alexander Lees, a senior lecturer in conservation biology at Manchester Metropolitan University, also agreed with Dr. Broughton's theory. "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," he said.
"There always seems to be a kneejerk response to blame environmental pollutants, but collisions with infrastructure are very common. 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."