But as you see in the NATURE program FIRE BIRD, the lesser flamingo (Phoenicopterus minor) is perfectly suited to this hostile environment. The region's four million flamingoes form tribes thousands of birds strong, living off the volcanic lakes that, although caustic, teem with the microscopic algae these birds eat.

The most alkaline of these shallow, corrosive bodies of water is Lake Natron, located near the extinct Gelai Volcano in northern Tanzania. High mineral concentrations of sulfur, chlorine, phosphorus, and soda cause the water to turn caustic. The center of a volcanic soda lake holds the highest concentration of minerals. At the edges, an influx of fresh water from streams provides a much-needed oasis.

When a lake recedes, experienced flamingoes take this as a signal to move on. The birds know a shrinking lake will soon die, taking with it the algae they eat. And so begins the migration of hundreds of thousands of flamingoes, who may have to soar for days, covering hundreds of miles in their search for a suitable lake.