Eighteen grams—that’s about the weight of a two-euro coin. In the northeast of Hungary, researchers Péter Estók, Sándor Zsebők, and Björn Siemers observed how coal tits, small birds weighing just this much, hunt hibernating common pipistrelles in a cave during winter. Over two winters, they documented 18 direct predation events. The birds move slowly and systematically along the cave walls, listening for the faint sounds of the bats. Once they detect a bat, they use their beaks to crack open the skull and access the brain, a method similar to how some nocturnal raptors hunt in the dark. This behavior has been observed for more than ten years, suggesting that the coal tits are passing the skill down through generations. To test this, the researchers conducted an experiment where they played recordings of waking bat calls. The birds clearly heard the sounds and were drawn to the source, confirming that they use auditory cues to locate their prey. When the researchers provided an alternative food source, the birds stopped returning to the cave, showing that their bat-hunting behavior was driven by a need for food during scarce times. Once seeds and berries became available, the birds no longer targeted the bats. The study, co-supervised by the Max Planck Institute of Ornithology, raises intriguing questions about cultural learning in birds. While no formal evidence confirms that the behavior is passed on through observation, the persistence of the behavior over a decade suggests that it is not just the work of one clever bird but a learned skill shared among the group. This is similar to a famous case in the UK, where blue tits learned to open milk bottles to drink the cream, and the behavior spread rapidly across the population. However, in the case of the Hungarian coal tits, the behavior has so far only been documented in one specific cave with particular conditions, such as a large entrance that allows light in, which is essential for the birds to navigate the semi-dark environment. The coal tit is a familiar sight at bird feeders, and the common pipistrelle is a widespread bat species in France. Both species can live in close proximity, sometimes hibernating just meters apart in cellars or under rooftops. While the behavior observed in Hungary is notable, the researchers emphasize that it is localized to a specific cave with harsh winters and adequate light. At this stage, there is no evidence to suggest that similar behavior would threaten bat colonies in other regions. The study adds to the growing understanding of how animals, including birds, can adapt their behavior in response to environmental challenges, sometimes through the transmission of learned skills across generations.