During spring and fall migrations, billions of birds take to the night skies. The high-altitude darkness protects them from predators.

Well, most predators. New research shows an unlikely creature can successfully hunt these migrating animals.

It’s a bat.

In a paper published Thursday in the journal Science, researchers detailed how the largest bat in Europe, the greater noctule bat, nabbed a European robin, before chewing and eating the prey in flight. This stands in stark contrast to the bats’ typical diet of insects.

The idea that these bats sometimes eat birds had already been inferred from indirect data collected by Carlos Ibáñez, a researcher with the Doñana Biological Station in Seville, Spain, and his colleagues. They had found clues such as feathers and bird DNA in the bats’ droppings. But until this paper, it remained unclear exactly how bats weighing around 50 grams — the size of a medium chicken egg — could catch birds approaching half their weight.

“We finally figured out the murder mystery,” said Laura Stidsholt, a bat researcher at Aarhus University in Denmark and an author of the study.

While bats are best known for hunting insects, some larger species can occasionally prey on frogs, lizards and fish. Tropical bats have also been known to snack on perching songbirds.