Flamingos are famous for their long legs, their pink hue, and their iconic stance—they’re often seen wading into water, one leg at a time, searching for food. But they’re equally famous for their mysterious behavior: a number of theories have been proposed as to why the birds regularly stand on only one leg while resting, with some suggesting that this helps conserve heat in cold waters, others that it reduces muscle fatigue, and still others that it provides camouflage from predators in an aquatic habitat.
Until recently, however, the scientific community was split on why flamingos do this. In a study published this week in Biology Letters, scientists Young-Hui Chang and Lena Ting from Georgia Tech and Emory University set out to determine how much force was required for flamingos to keep their balance while standing on one leg. They clamped a flamingo’s leg and rotated it forward and backward to test how well the bird could support its weight without using active muscle control.
What they found was that flamingos’ one-legged stance is actually much more stable than it appears. Chang and Ting found that when the bird tilts its body, it causes small changes in the center of gravity (CoG), which are centered around the inner knee rather than at the foot. As a result, the ankle joint snaps shut, locking the leg into place, making the bird more stable and preventing it from swaying too much.
To further test their findings, the researchers measured how quickly flamingos were able to start moving after they’d rested in either the one-footed or two-footed position. They found that the flamingos were actually faster off the mark when they started in the two-footed position, ruling out the idea that the legs would take longer to tire out in the unipedal stance.
The team also examined cadaver flamingos to learn more about the structure of the leg bones and joints. They found that when a flamingo is in the one-legged stance, the ankle joint doesn’t snap shut. Instead, it forms a kind of “lock” with the foot bone that holds the leg into its locked position, requiring very little active muscle movement to maintain stability.
Finally, the team tested the thermoregulation theory by observing the percentage of flamingos who preferred to stand on one leg in different weather conditions. They found that flamingos were more likely to favor the one-leg stance in warm weather, which suggests they’re trying to minimize the amount of heat lost from their bare legs as they wade into colder waters. Despite these findings, Anderson says his team will continue to monitor flamingos to see if their behavior changes in response to environmental variables and to understand more about the mechanics of flamingos’ unique, one-legged balancing act. In the meantime, we’ll just enjoy seeing Floyd and all of our other flamingos standing on one leg while they relax. It’s just so pretty! See photos of the Zoo’s flamingos here.