Flamingo Feeding Flows

How flamingos stir, stomp, and chatter to bend flow and trap prey

 

Flamingos chattering underwater to induce flow towards the beak.

are flamingos water-benders?

Flamingos are known for their brightly colored pink feathers, notably obtained by their diet of brine shrimp. But how do flamingos, with their large beaks, collect enough tiny food to feed their large bodies? Whales can intake large volumes of water to collect a large number of plankton and shrimp by sailing through the ocean. The flamingo cannot intake large volumes of water like a whale, but does it have another method to cycle water and collect tiny prey?

We observed three interesting behaviors that hint at the mechanisms flamingos use to capture prey. First, they stomp and stir the sediments while feeding. Second, they “chatter” their beak and pulse their throat. Third, they rapidly retract their necks in and out of the water. We analyzed these behaviors using particle imaging analysis of captive flamingos, mechanical models, and with fluid simulations.

 
 

Major questions

  1. How does upside-down feeding and neck movement influence flow and affect nearby prey?

  2. How do chattering and stomping affect the fluid vortices and particle movement?

  3. Can the flamingo’s method inform our design of filtration systems and fluid technology?

 

What we’ve discovered

Beak Shape and Bobbing Create Upwelling

While feeding upside down, flamingos frequently retract their heads from the bottom, facilitated by their elongated and S-curved flexible necks. This quick retraction (~40 cm/s), occurring in ~400 ms, produces strong tornado-like vortices, stirring particulate sediments at the bottom and upwelling them towards the surface. During this upside-down feeding, the anatomical upper bill lies beneath and, due to the bent shape, presents a flat surface primed for vortical interaction.

Marching Stomp Method To Make Vortices with Morphing Feet

While feeding, flamingos keep their heads upside down in front of their marching feet. Using a bio-engineered morphing foot that passively opens and closes, we discovered that the stomping produces strong horizontal vortices with each cycle, reinvigorating the previous one and effectively trapping small fast-swimming pond organisms like copepods and boatman bugs. The asymmetry in toe and web morphology pushes the vortices to where the beak filter feeds.

Flamingos Point Against the Flow to Trap Prey

Flamingos' “backward” interfacial feeding (beak points downstream) contrasts with typical filtering vertebrates like whales or fish (mouth opens upstream). Using a 3D-printed L-shaped beak in a flume, we found they generate a von Kármán vortex street with a strong recirculation zone. The L-shaped beak is essential for skim-feeding at the interface, allowing them to capture food particles within the recirculation zone. Live brine shrimp, both adults and eggs, are collected into the beak and unable to escape the strong recirculation zone induced downstream.

Simulations Demonstrate How Flamingo Morphology Affects Flow

We used numerical simulations to see how foot and beak morphology to create and leverage vortices for feeding. First, simulations show that the foot generates a pair of toroidal vortices, creating a strong vorticity region near where the beak feeds. Second, simulations also show the bent shape of the flamingo’s mandibles positions the beak tip within the recirculating zone.

Flamingo Beak Chattering Produces Directional Flow

Using particle image velocimetry on living flamingos feeding while clapping their mandibles underwater at 12 Hz, we found that flamingos produce a directional flow, unexpected in typical in-and out-flow pumping. We demonstrated, using a mechanical chattering beak from a flamingo cadaver, that asymmetric beak oscillations are enough to produce this directional flow. We engineered a flamingo-inspired filtration system and found that the beak chattering can increase particle filtration up to 9x. This finding can be applied to remove microplastics or harmful microorganisms from water bodies and address membrane fouling/clogging issues in real-world applications.

 

Read the papers

 

Flamingos use L-shaped beak and morphing feet to induce vortical traps for prey capture (2025)

 

See the comic

Saad Bhamla