I once wrote that Great Tits are not just cute, colorful little fluff balls at the feeder, but also clever—and sometimes brutal—inhabitants of our world. Recently I stumbled upon a real ornithological gem: an archival BBC film from 1958, showing a Great Tit opening a milk bottle left on someone’s doorstep! The film is short, black and white, and yet it says more about avian intelligence than many textbooks. A moving and fascinating little scene from old Britain.

The birds that figured out how to steal milk!

It all began in the 1920s. That’s when individual Great Tits in Britain discovered that under the thin aluminium foil cap of milk bottles—those delivered daily to people’s doorsteps—there was a true delicacy: cream. The birds learned to carefully pierce the cap with their beaks and sip the rich layer from the top of the milk.

This behavior slowly spread among more and more individuals. It wasn’t genetic inheritance, but pure bird culture—one tit would watch another, learn, then try it out itself. By the late 1950s, Great Tits across the country knew the trick, and milk bottle opening had become a nearly everyday sight in British towns and villages.

But culture can vanish.

The British never had to invent a way to stop these clever birds. The world simply changed on its own. By the early 1960s, more and more people were buying milk in supermarkets, and refrigerators had entered homes. Doorstep milk deliveries disappeared.

And with them—the chance to practice the bird tradition. Younger tits had no one to copy. The trick was no longer useful. And so, quite naturally and without human intervention, an entire avian cultural skill faded away.

This is a textbook case of animal culture loss—a phenomenon that until recently was studied almost exclusively in humans. And yet, birds, dolphins, monkeys, and even fish can pass knowledge to one another. But only as long as their environment allows it.

The Great Tit — master of adaptation, but also a predator!

Meanwhile, the world keeps changing, and the Great Tit adapts in surprisingly brutal ways.

Between 2005 and 2009, research in Poland and Hungary shocked many nature lovers. It turned out that desperate Great Tits in winter are capable of killing hibernating bats deep in caves—by smashing their skulls and eating their brains.

Yes, you read that right. This was independently observed in two separate places: in Pieniny National Park in Poland and in northern Hungary. It wasn’t just an odd incident, but a deliberate survival tactic to get protein when other food sources were gone.

Other studies, conducted between 2007 and 2016 in various EU countries, show that Great Tits are increasingly attacking and killing other birds—mainly in the struggle for nesting sites.

In winter, when food is scarce, they also eat carrion and even hunt smaller birds. The most shocking discovery: active tit nests where dead birds were found with head wounds and missing brains. Everything suggests that the victim’s brain is treated as a particularly valuable food source—a quick shot of fat and energy.

Is all this climate’s fault?

Scientists agree—climate change, urbanization, and pesticide use all strongly influence bird behavior. Warmer winters mean migratory birds don’t travel as far, and resident species like the Great Tit stay and dominate breeding areas. Conflict is inevitable.

Add to that the decline of insects—especially in winter—and you have the perfect recipe for avian survival battles, where there’s no room for gentleness.

What can we learn from this?

This story is more than just a fascinating tale about a clever Great Tit and its dark behavior in caves. It’s a reminder of how profoundly our world and our actions affect wildlife.

So maybe, when you watch a Great Tit at your feeder this winter, you should think not only about what seed to pour in—but also about how to protect the world where these small, shadowy creatures still have a place of their own.