Hundreds of blackbirds dropped from the sky on February 7 in the Alvaro Obregon area of Cuauhtemoc city, Mexico, with the concerning phenomenon caught on CCTV.
The yellow-headed migratory birds can be seen falling to earth as a flock. When police were called to the scene at around 8:30am, the dead animals littered the sidewalk.
Some of the flock is seen flying away, while others remain motionless on the ground.
The incident itself is understood to have occurred at 5am. Yellow-headed blackbirds travel south to Mexico from Canada each winter.
A vet who examined the dead birds suggested they may have died after inhaling toxic fumes, perhaps from a heater, according to local paper El Heraldo de Chihuahua. The vet also proposed that the birds may have been electrocuted by power lines.
Some social media users have suggested the incident could have been a murmuration – the collective movement of bird flocks often involved sudden changes in direction – which went wrong.
Dr.Richard Broughton, an ecologist with the UK Centre for Ecology & Hydrology, agreed, saying he was almost sure that a predatory bird drove the murmuration crashing towards the ground.
A similar phenomenon was seen a week prior, as 200 birds mysteriously dropped dead from the sky near the villages of Waterston and Hazelbeach in Wales.