Why do flamingos stand on one leg?
The best explanation is that it saves energy and heat. Flamingos seem to lock into a stable one-legged pose that takes almost no muscle effort to hold.
Going deeper
Standing in cool water loses body heat through the legs, so tucking one up may help keep warm. Flamingos do stand on one leg more often in colder conditions.
A 2017 study found that flamingo bodies can balance on one leg passively, without muscle effort, thanks to how their joints line up. Standing on one leg may actually be more restful for them than standing on two.