Algae are one of the few things that can live in extremely caustic soda lakes, and the only animals able to stand in the burning water and strain the algae out are the flamingos. But they can't drink the water. For that - and to bathe - they go to the edge of the lake, where springs are fresher away from the caustic cauldron. Not only do the flamingos have to tolerate caustic water, but every year there is a dry season, when no rain refreshes the springs and the lake shrinks. Then the flamingos' world becomes more caustic and more crowded.