When news reports about this unusual event reached us, time was short. We did not have time to read any details, and now it is clear that waiting for science to comment was a useful delay.

Thanks to Juan Siliezar for the explanation:

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Those birds that crashed and died? It wasn’t fumes

After internet theorists react to viral video, Harvard researchers answer with science

You’ve probably seen the video — or at least heard some chirpings about it.

Footage from a security camera in Cuauhtémoc, a city in Chihuahua, Mexico, shows a massive flock of migratory birds swooping down like a cloud of black smoke and crashing onto pavement and the roof of a house. While many of the yellow-headed blackbirds recovered, about 100 died.

Ever since the mass crash, on Feb. 7, viewers of the viral video have sought to explain what happened. Suggestions from scientists and anyone with a Twitter account have included: the birds were reacting to a predator, inhaled toxic fumes, were zapped by a power line, or became victims of electromagnetic interference. Some sleuths have floated 5G technology as the culprit.

Harvard ornithologist Scott V. Edwards, Alexander Agassiz Professor of Organismal and Evolutionary Biology, and Flavia Termignoni Garcia, a postdoctoral researcher from his lab who studies bird behavior, believe the truth lies in flock dynamics.

They say that when migratory birds fly in large flocks, they follow the leader. One bird sets the pace and direction, the others just go along with what everyone else is doing. “They’re not looking very distant; they’re actually following their closest neighbor in the flock so basically taking cues on where to move based on their closest neighbor,” Edwards said.

Yellow-headed blackbirds, which live primarily in the northern U.S. and Canada but winter in Mexico, have ben known to travel in groups of 3,000, so it’s easy to see how one mistake could lead many to their doom…

Read the whole article here.