If you’ve ever really looked at how flamingos eat, you know how captivatingly peculiar it is. They bob their inverted heads in the water and do a kind of waddle cha-cha as they inch their way across shallow water, filter-feeding small crustaceans, insects, microscopic algae and other tiny aquatic morsels.

Victor Ortega-Jiménez, an integrative biologist at the University of California, Berkeley, remembers being fascinated by this behavior the first time he saw it in 2019, during a trip with his wife and child to the Atlanta zoo. Ever since, he has been wondering what, exactly, was going on beneath the surface.

“The birds looked beautiful, but the big question for me was, ‘What’s happening with the hydrodynamic mechanisms involved in flamingos’ filter feeding?’” he said.

Back home, he was surprised to find no explanation in the scientific literature — so he decided to produce one himself. Several years of meticulous research later, he and his colleagues arrived at a surprising discovery, described Monday in the Proceedings of the National Academy of Sciences. Flamingos, they found, are active predators that harness the physics of how water flows to sweep up prey and funnel it directly into their mouths.

“We are challenging the idea that flamingos are just passive filter feeders,” Dr. Ortega-Jiménez said. “Just as spiders produce webs, flamingos produce vortices.”