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Local expert explains viral video of 100s of birds in Mexico diving to the ground

Why did they crash to the ground all at once like that?

A yellow-headed blackbird. Alan Vernon/Wikimedia Commons

Imagine looking out your window and seeing a black cloud of birds rapidly diving straight down all at once only to smash against the pavement.

That’s the shocking sight people who lived on a particular street in Mexico witnessed on Feb. 7. Lucky — or perhaps unlucky — for us, the whole thing was caught on security footage and has gone viral on social media.

The following video contains graphic images of dead animals.

So how did this happen?

Boston.com reached out to local bird expert Ethan Temeles, a biology and environmental studies professor at Amherst College, to find out.

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Firstly, he said, the birds in the video are yellow-headed blackbirds, which he said are very beautiful in person.

Secondly, he said he agrees with other experts that the cause of the dive was likely due to the flock encountering a predator in the sky.

Importantly, Temeles said, the birds were not frozen or dead when they hit the ground.

He said that one thing that can cause birds to fall down to the ground in a group is unknowingly hitting a part of the sky with very low temperatures and freezing mid-flight, which causes them to fall frozen to the ground.

Another reason birds may fall from the sky is when they come across a very strong pesticide or another dangerous chemical in the air and die, he said.

But most of these birds were still alive after taking a dive, which rules out those two possibilities, Temeles said.

“The birds were still moving, and it indicated that there must have been some predator,” he said. “Maybe they hit a wave of migrating hawks or something like that.”

Temeles explained that diving down is one of the best ways for a flying creature to avoid a predator. This is because it is faster and easier than flying up or dodging to the side. Birds might dive down and then hide in a bush until the predator is gone.

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In this case, Temeles said, there may have been something blocking the birds from seeing that they were plummeting straight to the ground, such as fog. This would explain why so many did not stop themselves from slamming into the ground.

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