Mexico’s bird drop may have been driven by predator

A swarm of hundreds of birds crashed to the ground outside his house. The carcasses were strewn across the street, the birds dead on impact.

That’s the vision a handful of people woke up to in Chihuahua, Mexico on February 7th.

Millions around the world were shocked by the massacre when security camera footage was released, but it left people with more questions than answers.

“The cause of this bizarre and troubling incident is honestly an open question at this point,” said Carlos Botero, assistant professor of biology at Washington University in St. Louis.

The footage didn’t show the entire swarm of birds, but Botero surmised that they could have flown through a cloud of lethal chemicals. Autopsies of the dead bird specimens need to be completed to determine if that was the case, he said.

A predator could also have made the birds fly frantically, Botero added.

Richard Broughton, an ornithologist at the UK’s Center for Ecology and Hydrology, was pretty sure the ploy was to avoid a predator like a peregrine falcon.

“Birds form tight flocks, called ‘murmurs’, that whirl in the sky to try to confuse the hawk so it can’t pick a target,” Broughton, a bird expert, said in an email.

To counter this strategy, the hawk dives straight into the flock of birds to separate a target, Broughton explained. When that happens, those pasts try to avoid it.

In the video, viewers are likely seeing the birds trying to escape a predator that attacked them from above, he said. The birds descended, but some couldn’t get there fast enough, Broughton added.

WARNING: GRAPHIC CONTENT

Security footage shows a flock of yellow-headed blackbirds drop dead in the northern Mexican state of Chihuahua pic.twitter.com/mR4Zhh979K

— Reuters (@Reuters) February 14, 2022

Assuming the time stamp of 7:42 pm local time on the video is accurate, the birds were likely leaving their nocturnal roost nearby, said Andrew Farnsworth, a senior research associate at the Laboratory of Ornithology at Cornell University (LOUC) in Ithaca, New York. York.

In addition to the predatory theory, Farnsworth suggested that a loud noise scaring the birds was another possibility. This has happened in the past with other bird species, he said.

How common is this behavior?

It’s very rare for birds to fall to the ground and it’s not normal behavior, Botero said.

There are other instances of birds dying from abrupt collisions, Farnsworth said.

In 1999, about 110 reis, a type of large sea duck, were found dead on Canada’s Baffin Island. There were no obstacles in their way, so it’s likely that they fell because of poor visibility, which can be attributed to the cataracts in their eyes, according to a study.

In 1985 and 2003, dozens of geese were found dead in fields in southern Manitoba, Canada. The researchers initially thought they were poisoned, but the serious injuries the geese sustained suggested they could be disoriented on moonless nights or frightened by a storm.

What are these birds?

Experts have identified the birds as yellow-headed cranes, migratory birds that live in the west and on the prairies of North America. In winter they form large flocks, which is what was captured on video.

eBird, an online bird observation database, at LOUC tracks the migration pattern of these birds on a map as they fly south from Mexico in the winter and then back to the United States and Canada in the summer. At the time the footage was shot, most of the birds would be in Mexico, with a few scattered across the southwestern United States.