Why Do Flamingos Stand on One Foot?

Zoo visitors often ask why flamingos stand one one foot--this curious behavior is frequently observed by the public. Until recently, scientists only had guesses as to the answer. In 2009, a behavioral study by Matthew Anderson and Sarah Williams, published in Zoo Biology, was the first to observe flamingos to find out why they behave this way. The evidence suggested flamingos are trying to prevent heat loss to the water they're wading in.

Hypotheses

Avian biologists had previously put forth many explanations for flamingos standing on one leg. One was it prevented their legs from getting tired, giving them a chance to rest. A second was that it would let them escape from predators faster. Still others proposed that, like dolphins, flamingos could let one half of their brain sleep at a time, and the resting leg was controlled by the resting half of the brain. Finally people proposed that it helped preserve body heat.

Eliminating Hypotheses

By watching flamingos for long periods of time, Anderson and Williams found that it took longer for them to move if resting on one leg instead of two, and that resting on one leg and then the other took more energy. That meant standing on one leg made flamingos more vulnerable to predators, not less.

Conclusions

Williams and Anderson watched flamingos at the Philadelphia Zoo and found that flamingos were more likely to stand on one leg in the water than on land. They also saw that when the water was warmer, more birds would be on two legs. They concluded the flamingos were avoiding heat loss to the water. By submerging only one foot, flamingos were able to cut that in half.

Features

While observing the flamingos, researchers also noted on which leg the birds were standing. They saw that while flamingos tend to spend long periods of time on one foot, they did not prefer one leg over the other. Favoring one foot could cause circulation problems and damage the leg, so it made sense they distributed the burden evenly.

Other Findings

Though Anderson and Williams did not find flamingos preferred to rest on one leg over the other, they did find that when resting their heads, there was a strong tendency to have their heads to the right. Birds that rested their heads to the left were more likely to end up engaging in aggressive behavior with other members of the flock. Social dynamics are important in these very social birds.

References

• BBC Earth News article: "Why flamingoes stand on one leg"
• Zoo Biology: Anderson and Williams Study (.pdf)

Resources

• San Diego Zoo Animal Bites: Flamingos