Flamingos' feet and angled beak create tiny tornadoes to capture prey

When picturing a flock of flamingos, we often imagine long pink legs planted in a shallow lake and heads submerged as they filter feed. Though it looks peaceful, there’s a lot going on beneath the surface. These birds are manifesting storms of swirling tornadoes, using their webbed feet and angled L-shaped beak to help them capture prey.

A new study, published in Proceedings of the National Academy of Sciences, has revealed that flamingos are specialized predators, using active predatory strategies. This is far from the prevailing view of flamingos being passive filter feeders.

“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 at the University of California, Berkeley. “It seems like they are filtering just passive particles, but no, these animals are actually taking animals that are moving.”

To begin the research, the team trained Chilean flamingos (Phoenicopterus chilensis) to feed from a water-filled aquarium and then filmed them with high-speed cameras to analyze their foraging behavior. Using this data, 3D-printed physical models were created to mimic the behavior of flamingos.

The search for food particles begins with the “stomp dance” using their webbed feet. Flamingos frequently stomp their flexible feet in the water. During stomping, the webbed foot opens when descending and closes when the foot ascends. This action stirs up sediments and millimeter-scale organisms like brine shrimp and mayfly larvae, and generates miniature tornado-like whorls that spiral upward. The 3D models confirmed that floppy legs are crucial to produce an effective vortex.

Now the head and beak come into the play. The flamingo deploys its L-shaped beak in the water such that the angled front of the beak is parallel to the ground. The bird now starts “chattering,” i.e., rapidly opening and closing its beak about 12 times per second. This creates an additional vortex, effectively trapping prey.

And this is not all. While feeding with its head upside down, the flamingo quickly and frequently retract their heads from the bottom. The quick retraction produces strong tornado-like vortices that stir and upwell particulate sediments, aiding the stomp dance.

“Flamingos are super-specialized animals for filter feeding,” says Ortega Jiménez. “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.”

Apart from these findings simply shedding new light on their feeding routine, researchers suspect these flamingo tornado principles may help develop better systems to extract tiny particles, like microplastics, from water.

The study has been published in the Proceedings of the National Academy of Sciences.

Source: University of California, Berkeley