Chilling video has emerged on the internet where hundreds of birds can be seen crashing to their deaths mid-flight in the Mexican state of Chihuahua. The birds — later identified as yellow-headed blackbirds — were discovered lifeless on sidewalks by residents of Cuauhtémoc City, the Spanish-language El Heraldo de Chihuahua reported.

What happened

The footage from a security camera shows the flock of migratory birds descending on to houses like a cloud of black smoke. Most birds manage to fly off but subsequent footage shows carcasses of the distinctive black and yellow birds scattered on streets of the city.

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.

The cause of death remains unclear but experts said it was most likely that the flock was “flushed” from above by a predatory bird swooping down to make a catch.

Here’s a footage posted by Reuters on Twitter:

Possible reasons of death

According to the local paper El Heraldo de Chihuahua, a veterinarian suggested blame for the incident could lie with high levels of pollution, driven by the use of wood-burning heaters, agrochemicals, and cold weather in the area.

Another suggestion was that the birds were electrocuted while resting on power lines. There was speculation on social media that it could have been caused by 5G technology.

What experts said

But Dr Richard Broughton, an ecologist with the UK Centre for Ecology & Hydrology, said that although he could not see a raptor in the footage, he was 99% sure it was caused by a predatory bird. A predator could have made the birds swirl tightly and driven them towards the ground, with higher birds forcing lower ones to crash into the buildings or the ground.