Flamingos Create ‘Mini Tornados’ In Water To Capture Prey

A new study reveals how flamingos use their feet, heads and beaks to create “water tornados” to funnel brine shrimp and other prey directly into their mouths.

“Flamingos are actually predators, they are actively looking for animals that are moving in the water, and the problem they face is how to concentrate these animals, to pull them together and feed,” said Victor Ortega Jiménez, an assistant professor of integrative biology at the University of California, Berkeley, who specializes in biomechanics. “Think of spiders, which produce webs to trap insects. Flamingos are using vortices to trap animals, like brine shrimp.”

Researchers from UC Berkeley and collaborators at the Georgia Institute of Technology in Atlanta; Kennesaw State University in Marietta, Ga.; and the Nashville Zoo in Tennessee studied Chilean flamingos at the Nashville Zoo, and analyzed 3D-printed models of the feet and L-shaped bills. Their findings were published this week in the journal Proceedings of the National Academy of Sciences.

The team filmed the flamingos feeding in a large tray of water, using a laser to illuminate gas bubbles and reveal the vortices created by their heads and beaks. 3D-printed models helped researchers more precisely study how they moved the water and particles during beak clapping or “chattering.”

The study reveals that flamingos first “dance,” using their webbed feet to churn the sediment and “propel it forward in whorls” that they draw to the surface by “jerking their heads upward like plungers.” The action creates “mini tornados,” and as the bird’s head remains upside-down in the vortex, it chatters its angled beak to create smaller vortices that directs sediment and food into their mouth, where it’s filtered.

The flamingo’s “unique” beak is flat on the angled front end, and remains parallel to the bottom while their head is upside down in the water. That allows the bird to engage in another technique called “skimming,” in which it uses its S-shaped neck to push its head forward while rapidly clapping its beak, creating sheetlike vortices called von Kármán vortices to trap prey.

“We observed when we put a 3D printed model in a flume to mimic what we call skimming, they are producing symmetrical vortices on the sides of the beak that recirculate the particles in the water so they actually get into the beak,” Ortega Jiménez said. “It’s this trick of fluid dynamics.”

The findings refute the flamingo’s reputation as a “passive” filter feeder.

“It seems like they are filtering just passive particles, but no, these animals are actually taking animals that are moving,” Ortega Jiménez said.

He said he was inspired to undertake the study after visiting a zoo and noticing only light ripples on the surface of the water where the flamingos fed.

“We don’t know anything about what is happening inside. That was my question,” he said. Next, he plans to study the flamingo’s “piston-like” tongue and how the comb-like edges of the beak filter prey out of briny — and sometimes toxic — water.

“Flamingos are super-specialized animals for filter feeding,” he said. “It’s not just the head, but the neck, their legs, their feet and all the behaviors they use just to effectively capture these tiny and agile organisms.”