Mysterious bird behaviour caught on a security camera in Mexico has led to a swathe of theories about the event.
Footage shot on February 7 at Chihuahua, near the United States border, shows a large flock crash into a road and a yellow house.
While a number of the yellow-headed blackbirds appear to recover quite quickly and fly away, dozens can be seen lying motionless.
Police documented the carnage, taking photos of the tiny migratory birds which did not survive the incident.
A local vet speculated the deaths could have been induced by toxic fumes or an overcharge from electricity cables.
Social media was abuzz with wild conspiracy theories including 5G and solar winds, however the actual reason is likely much simpler.
Expert shares theory about why birds crashed into ground
After viewing the footage on a large screen, Sean Dooley from BirdLife Australia, concluded the flock was mostly likely trying to avoid a predator and crashed.
The birds appear to have assembled in a murmuration, a behaviour that creates large breathtaking patterns in the sky.
Like with schools of fish, which are similar in appearance, this behaviour is used as a defence mechanism to avoid predators.
“They’re creating a moving target of multiple parts, and by constantly shifting their position it's distracting for predators which aren’t able to hone in on any individual birds,” Mr Dooley told Yahoo News Australia.
“The way that murmurations work is that each bird is actually trying to get into the centre of the of the flock.
“So they adjust according to what the six or seven birds around them are doing, so you get these incredible results.”
Mr Dooley believes the birds may have miscalculated where the ground was while trying to avoid a falcon or some other bird of prey.
Another possibility is that a predator flew through the murmuration, causing birds to fly off course.
“Anytime birds die, people automatically jump to a worst case apocalyptic type scenario be it mass poison, pollution, 5G or whatever,” he said.
“This event really fits the MO of a flock avoiding a predator and making a tragic miscalculation.”
Other strange events:
Birds crash into skyscrapers on migratory routes
Birds frequently collide with infrastructure installed in the path of their migratory routes.
Numbers of deaths in North America are “insanely high”, according to Mr Dooley, who said that unlike in Australia, authorities do a good job of collecting data about the issue.
Collisions with skyscrapers, houses and powerlines are common, and wind turbines also take out a small number.
Migratory birds are known to have a higher attrition rate than territorial varieties.
One example is Australia’s orange-bellied parrot which is federally listed as critically endangered.
“Whether (they’re dying) on migration from Tasmania, or whether it's happening on their wintering grounds on the mainland, we don't know,” Mr Dooley said.
“But certainly the number of birds that come back to the breeding site in Tasmania each year is always far lower than those that left at the end of the previous breeding season.”
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