A simmering sea of pink, they are one of the marvels of the natural world.
This astonishing picture taken by specialist aerial photographer Yann Arthus-Bertrand shows flamingos on Lake Nakuru in Kenya's Rift Valley, where up to 1.5 million have been seen at a time. Scroll down for more...
Pink paddler: Thousands of flamingos enjoy the vast algae food source in Lake Nakaru, part of Kenya's Rift Valley
Widely regarded as the greatest bird spectacle on earth, the myriad flamingos gather there to feed on the abundant blue-green algae which thrive in the warm alkaline waters, with their high soda content caused by intense evaporation in the burning African sun.
Scientists believe that the vast flamingo population at Nakuru can consume as much as 500 tons of algae every day.
They feed with their long necks bent down and their bills upside down in the water, using their tongues to pump in and out to suck in the salty, alkaline water and mud.
Filters in the bill catch the microscopic algae floating in the water, as well as the small shrimps which give them their pink colour.
Fortunately, given the brackish water, flamingos have a poor sense of taste and no sense of smell.
There are two types of flamingo species on the lake: the Lesser flamingo, distinguished by its deep red carmine bill and pink plumage, and the Greater, which has a bill with a black tip.
Conservationists are increasingly concerned that pollution from local industries is causing the flamingo population at Lake Nakuru - a protected area - to fall.
Arthus-Bertrand has travelled the world photographing flamingos - and has captured their elegance in flight with this astonishing picture (right) taken in the Saharan oasis of Ouargla, eastern Algeria. But for sheer breathtaking spectacle, nowhere can match the flamingos of Kenya's Rift Valley.
In the pink: Stunning photo of 1.5million flamingos on lake | the Daily Mail