A recent study conducted by researchers from the University of California, Berkeley, and Georgia Tech has uncovered that flamingos are not mere passive filter feeders; instead, they are active predators that employ flow-guided traps to catch nimble invertebrates.
Flamingos feed by dragging their flattened beaks forward along the shallow lake bottom. To enhance feeding efficiency, they stomp their feet to stir up the bottom, create swirling vortices with their heads, and repeatedly slap their beaks to catch food like brine shrimp. Image credit: aztli ortega.
“Flamingos are predators actively seeking out moving animals underwater. The challenge they face is how to concentrate these prey items to attract and capture them.”
“Consider how spiders spin webs to catch insects. Flamingos utilize vortices to trap creatures such as brine shrimp.”
Dr. Ortega Zimenez and his team conducted the study using Chilean flamingos (Phoenicopterus chilensis) sourced from the Nashville Zoo, where they were kept in aquariums for several weeks.
https://www.youtube.com/watch?v=nbkrxu7n6kw
Utilizing high-speed cameras and particle image velocity measurements, the researchers documented and analyzed feeding behaviors, employing flow visualization techniques involving fine food particles and oxygen bubbles.
They discovered that the birds use their floppy, swaying feet to disturb the bottom sediment and propel themselves forward in a swirling motion. Additionally, the flamingos convulse their heads upward like plungers while creating mini-tornados to draw food from the water’s surface.
As the birds keep their heads inverted in a watery vortex, their angled beaks create small vortices that direct sediment and food into their mouths, enhancing their feeding efficiency.
The unique structure of the flamingo’s beak, with its flattened shape and angled front, enables a technique known as skimming. This involves the bird extending its long, S-shaped neck to push its head forward while rapidly beating its beak, generating a sheet-like vortex (von Karman vortex) that captures prey.
“These complex active feeding behaviors challenge the long-held belief that flamingos are merely passive filter feeders,” noted Dr. Ortega Zimenez.
“While they may appear to be filtering only passive particles, these birds are actively preying on moving organisms.”
https://www.youtube.com/watch?v=mdziufdf3ka
The authors also applied computational fluid dynamics to simulate the 3D flow around the beak and feet of the flamingos.
They confirmed that the vortices indeed concentrate particles, similar to experiments that used a 3D printhead with aggressively swimming shrimp and passively floating brine shrimp eggs.
“We observed that when we placed 3D printed models in the water to replicate skimming, they generated symmetrical vortices along the sides of the beak, cycling particles in the water effectively,” Dr. Ortega Zimenez shared.
The team’s findings will be published in Proceedings of the National Academy of Sciences.
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Victor M. Ortega Zimenez et al. 2025. Flamingos use their L-shaped beak and morphing legs to induce vortex traps for prey capture. pnas 122 (21): E2503495122; doi: 10.1073/pnas.2503495122
Source: www.sci.news
