Flamingos, often observed standing gracefully in shallow alkaline lakes with their heads submerged, may appear to be merely feeding. However, beneath the surface, a complex and fascinating feeding strategy is taking place. Recent studies on Chilean flamingos at the Nashville Zoo have revealed how these remarkable birds utilize their feet, heads, and beaks to generate swirling vortices in the water, allowing them to effectively concentrate and consume their prey.
According to Victor Ortega Jiménez, an assistant professor of integrative biology at the University of California, Berkeley, who specializes in biomechanics, flamingos are not passive filter feeders as commonly believed. "They are actually predators actively searching for moving organisms in the water," he explains. The challenge lies in how they can gather these elusive animals for feeding. Ortega Jiménez likens their technique to that of spiders, which create webs to trap insects. In the case of flamingos, they harness the power of water vortices to trap small creatures like brine shrimp.
In collaboration with researchers from the Georgia Institute of Technology, Kennesaw State University, and the Nashville Zoo, Ortega Jiménez's findings were published in the journal Proceedings of the National Academy of Sciences. The research highlights that flamingos utilize their flexible webbed feet to stir up sediment on the lake's bottom, creating whorls of water that they then draw to the surface by lifting their heads, akin to plungers. This action forms mini tornadoes in which the flamingos’ heads remain submerged, using their uniquely shaped beaks to further direct sediment and food into their mouths for filtering.
The flamingo's beak is specially designed, being flattened at the front so that when the bird's head is inverted in the water, it aligns parallel to the lake bottom. This anatomical adaptation allows flamingos to employ a technique known as skimming. By extending their long, S-shaped necks and rapidly clapping their beaks, they generate sheet-like vortices, known as von Kármán vortices, to trap moving prey.
Ortega Jiménez emphasizes that these active feeding behaviors challenge the traditional view of flamingos as passive feeders. "It seems like they are filtering just passive particles, but in reality, they are capturing moving animals," he states. The principles discovered through this research could inspire innovations in various fields, including the design of more effective systems for concentrating microplastics from water, advanced self-cleaning filters based on chattering mechanisms, and robots that mimic the flamingo's ability to traverse muddy terrains.
Ortega Jiménez's fascination with flamingo feeding behavior began during a visit to Zoo Atlanta with his family before the COVID-19 pandemic. Captivated by their feeding patterns, he decided to investigate further. Initially a postdoctoral fellow at Kennesaw State University, he later moved to the Georgia Institute of Technology, where he collaborated with engineers and gained access to flamingos at the Nashville Zoo. The team filmed the birds feeding in a controlled environment, utilizing lasers to visualize the vortices created by their movements.
After transitioning to the University of Maine as an assistant professor, Ortega Jiménez refined 3D-printed models of flamingo beaks and feet, allowing for a more precise study of their feeding mechanics. In 2024, he joined UC Berkeley, where he conducted experiments to quantify how effective chattering and foot movements are in capturing live brine shrimp. Using a real flamingo beak attached to an actuator, he simulated the chattering action and found that this behavior significantly increased the number of shrimp captured.
The flamingo's feeding behavior begins with its feet. Observing them in shallow water, one can often see their unique dancing-in-place or circular movements. Their floppy webbed feet enable them to stir up sediment without the suction that complicates movement for other species. When they walk or run, flamingos slide their feet into the water, a technique that has potential applications for robotics designed to navigate wet or muddy environments.
Ortega Jiménez's research involved creating models of both rigid and flexible flamingo feet to analyze how each design influences fluid dynamics. He discovered that the flexible feet are more adept at generating sediment vortices with each step, while rigid designs primarily cause turbulence. Additionally, he modeled the flamingo's beak to demonstrate how pulling the head upward creates vertical vortices that help concentrate food particles.
Moving forward, Ortega Jiménez aims to explore the role of the flamingo's piston-like tongue and the comb-like edges of the beak in filtering prey from briny, sometimes toxic, water. "Flamingos are remarkably specialized for filter feeding," he notes. "It's not just their heads, but their necks, legs, feet, and the entire suite of behaviors they employ to effectively capture tiny and agile organisms." This comprehensive research highlights the intricate feeding strategies of flamingos and their potential implications for technology and biology.
Co-authors of the study include Tien Yee from KSU-Marietta, postdoctoral fellow Pankaj Rohilla, graduate student Benjamin Seleb, Professor Saad Bhamla from Georgia Tech, and Jake Belair of the Nashville Zoo.
