Nature Diary
Flamingoes

Flamingoes are found mostly in the western and southern parts of India. They are very social birds and live in large colonies. They are usually found near water, because they are wading birds, although they are excellent fliers.
The most characteristic feature of these birds is their orange-red colouring and very long legs. Some of the species like Greater Glamingo can be 75 cm tall. They keep the legs tucked in when flying so that they look very elegant and stream-lined. 
Flamingoes mostly feed on small insects and algae in the water. They use their bills to separate mud and silt from the food they eat. Even more strangely, they are used upside-down. The filtering of food items is assisted by hairy structures called lamellae along the jaw bones, as well as the large, rough-surfaced tongue.
The pinkish color of flamingoes comes from carotenoids in their diet. American flamingoes are a brighter red color because of the beta carotene availability in their food while the lesser flamingoes seen in India are a paler pink due to ingesting a smaller amount of this pigment.
They secrete oil from their tail, which they rub over their feathers in a process called preening. This helps to water proof them so they can swim in water.
A peculiarity of these birds is that they are often seen standing on one leg, whether on land or in shallow water. For a long time scientists believed that this was in order to conserve body heat. After all, it can be cold, standing in the water. By removing one leg from the water, it decreases the rate at which it cools off. Since they are warm-blooded birds, it seems to make sense that they tuck in one leg firmly against their body and stand on one leg only (they alternately stand on the right or left leg).
But they show this behaviour on land as well. Now it is believed that flamingoes do this to conserve (save) energy, not heat. A detailed study in 2017 showed that flamingoes may have a mechanism that locks the joints in their legs. This is similar to how a horse can sleep standing up without any effort. The locking of the joints means that there is hardly any muscle activity required for balancing, and so practically no energy required to hold the pose. While this seems to be the favoured explanation today, it is not clear how exactly the ligaments and tendons lock the joints in place.
Flamingoes aren’t the only animals to engage in this behaviour. Ducks, geese and swans do this as well. But because flamingoes have such long legs, we see it more. We can even see this behaviour in humans to some extent if they’re in a queue: people will rest more weight on one leg than the other.
Sources: https://www.newscientist.com, Wikipedia