[ intro ].

Brain-eating zombies don't exist. The dead don't hunger for brains.

The living, however, are another story. If you were feeling disappointed at the lack of prospects for a zombie apocalypse, well, you can still look forward to the brain-eating, killer songbird apocalypse. Yes, I said brain-eating, killer songbirds.

In a remarkable example of animals developing novel adaptations to challenging situations, members of a certain population of great tits have developed a taste... for bat brains. Under ordinary circumstances, these birds eat insects, though they will also take seeds from feeders, thus nurturing the illusion that they're all lovely and chirpy and innocent like songbirds are supposed to be. There were clues about their darker nature, though!

Like, great tits are already adept at disemboweling — they feed fat caterpillars to their young, which they first lovingly prepare by picking out the guts. So we really should have seen this whole thing coming. Now, I should point out that brain-eating is not usual behavior for great tits in general, but rather for a select group of them that live near a particular cave in Hungary. [PIHP-ih-STREHLL] The cave is occupied by hibernating pipistrelle bats .

And in a paper published in 2009, researchers documented great tits patrolling the mouth of the cav e and listening for the sounds the bats make when they're awake. Then, the researchers reported something horrifying:. The birds would fly into the cave, locate the bats, and peck their heads open, usually while they were still alive.

The bats are easy targets because they're sluggish, and not difficult for the birds to catch. But it's not like this was the bird's first choice. The scientists studying this phenomenon found that the birds will typically only do this in hard times.

Winters in northeast Hungary are harsh, so the birds don't have as much access to their usual menu of caterpillars and spiders. That suggests all this a survival strategy that this group of individuals has developed in response to food shortages. And it's not a brand new thing, either.

People have been anecdotally observing the brain-eating behavior in this group at least since the mid-1990s. So the researchers think it's most likely a learned behavior, passed down from great tit to great tit. That said, there are also reports of other populations of these birds eating bat brains in Sweden and Poland, so maybe it's more widespread.

Although in those cases, it's less clear if the birds did a murder, or just snacked on bats that were already dead. In any case, it's hard to say why these birds might have defaulted to eating bats during hard times, and specifically, why they might be zeroing in on the brains. It might just be because that's the killing blow.

After all, the birds do eat other parts of the bats, too, so it's not like they're exclusively brain snobs or anything. But it probably has something to do with opportunity. The bats provide a ready source of nutrition, and their vocalizations make them easy to find.

So, they become an ideal snack for those rough winter months. Now, this story would be disturbing enough if it were just about bats. But turns out, great tits have also been observed eating the brains of pied flycatchers, another type of songbird.

Although in those cases, it's as a way to defend their turf. In a 2019 study, researchers proposed that this is happening because the warming climate is causing the breeding periods of the two species to overlap, which creates conflict. Still, it's kind of a leap to go from “you're in my territory” to “I'm going to eat your brains,” and no one is really sure why the great tits end up with zombie-like food preferences.

But, hey. Brains do contain a lot of nutritious fats, so maybe they've picked up on the fact that they're energy-rich and delicious. So… maybe that's what the zombies were after all along.

Thanks for watching this episode of SciShow, and thanks to our patrons for making it possible for us to tell you about brain-eating murderbirds. Just wanted to get that in there one more time. If you want to help support our family of channels, go to patreon.comscishow to get started. [ outro ].