A security camera in Ciudad Cuauhtemoc, Mexico, captured some unsettling footage last week: A huge flock of yellow-throated blackbirds crashing out of the sky. Plenty of the birds got back up, but many others appeared to die in the event, which is just the latest in a longstanding pattern of bird die-offs.
The footage was taken in the early morning on February 7, according to the local media outlet El Hierro de Chihuahua, and was verified by the fact-checking website Snopes. It first shows an empty city street, which is then blotted out by a huge bird flock, which slams into the cityscape from above. The birds blanket the area and scatter across the street, and many return to the sky. But many others remain motionless on the ground.
The birds in the video are yellow-headed blackbirds (Xanthocephalus xanthocephalus), a migratory species that ranges from Mexico to the upper reaches of Canada. The blackbirds aren’t the first birds to do this: similar events happened in 2011, 2013, and 2021. Last year’s event, in New York City, had an obvious cause: Artificial Light at Night (ALAN), which can disorient migratory birds that use the stars to navigate. A lit-up city of glassy skyscrapers is a terrible trap for birds.
But Ciudad Cuauhtemoc, in the Mexican state of Chihuahua, isn’t exactly New York City. Experts aren’t sure what caused the recent event, though there are many theories. Andrew Farnsworth, an ornithologist at Cornell University’s Lab of Ornithology, told Gizmodo that, based on the video’s timing, the birds may have been leaving their nocturnal roost and beginning their diurnal activities. A possible cause of the dive-bombing behaviour, he said, is that the population was startled by either a predator or a loud noise. Many bird species perform intricate, coordinated flying manoeuvres called “murmurations,” sometimes to disorient and thereby deter predators.
“It is hard to say but from the video it looks like something really startled/surprised the flock, such as a predator, and caused the flock to take evasive action, with some hitting the ground and nearby structures,” said Martha Desmond, an ornithologist at New Mexico State University, in an email to Gizmodo. “While this can be shocking to see, these events do occur — just usually not caught on camera.”
As upsetting as these events are, it’s important to keep the numbers in perspective. Bird die-offs like the one in Mexico are dwarfed by the harm caused by humankind. “The greatest threats to migratory and migrating birds in North America include habitat loss and change, feral cats, collisions with buildings and other structures (and vehicles), and poisoning, for example, many potentially exacerbated by climate change,” Farnsworth said.
A 2019 study in Science found that there were 3 billion fewer birds in North American than in 1970, a 30% loss. With such alarmingly drastic population changes, it’s hard to see a single mass death event in Mexico as anything but an unfortunate blip for a class of animals currently undergoing mass extinction.