You probably thought ducks were cute waddlers who liked to eat your stale bread. Poof, your bubble has been burst. The BBC reports wild mallard ducks have been spotted eating other birds, swallowing one nearly whole, an "extraordinary" behavior that has never been observed before. Zoologist Silviu Petrovan of the University of Cambridge was birdwatching at a reservoir in Romania when he spotted a flock of mallards hunting a fledgling that had landed on the water. A female duck grabbed the grey wagtail in her beak, dunked it several times beneath the water, then ate it, Petrovan says. A black redstart landed soon after and "was almost instantaneously attacked" by 10 juveniles, per the study in the journal Waterbirds.
Though mallards in California have been sighted munching on sand crabs, the ducks usually eat plants, insects, and the occasional small fish. As far as scientists can tell, such predatory behavior not involving fish or amphibians has never been seen before. It's not only "very rare" but also likely a new phenomenon, says Petrovan, noting mallards have "not ... really evolved" to digest bones and feathers. "The mallard was massively struggling to eat that wagtail, presumably because it couldn't actually tear it to pieces" due to the design of its bill. So why would a duck eat a bird at all? Petrovan suggests "pressure for those fast-growing juveniles to get animal protein intake." (These birds are probably safe.)