One of the natural world's most breathtaking sights -- the pink and crimson clouds of flamingos that flock over East Africa -- is under threat.
Scientists have discovered that birds are dying in their thousands along the Rift Valley lakes of Kenya and Tanzania. However, they are baffled about the reason. Possible causes include avian cholera, botulism, metal pollution, pesticides or poisonous bacteria, researchers say.
In addition, fears for the future of the lesser flamingo -- Phoeniconaias minor -- have also been raised by plans to pipe water from one of their key breeding areas, the shores of Lake Natron.
"This could have quite a disastrous effect on water levels, which are critical for successful breeding," ornithologist Neil Baker, head of the Tanzania Bird Atlas project, said in Science.
The lesser flamingo is the smallest and most numerous of the world's six flamingo species; it thrives in the soda-rich waters of the Rift Valley, particularly on the shores of Lake Nakuru. Millions of the birds turn the lakes into "crucibles of pink and crimson fire," according to one description.
The lakes are crucial to the birds' breeding success because flamingos feed off the blooms of cyanobacteria that thrive there. In addition, the lakes' caustic waters provide protection for their chicks from predators.
But in recent years scientists have noted that mass deaths, which used to occur sporadically along the Rift Valley lakes, are more frequent. In the past few months, more than 30,000 flamingos were found dead along the shores of Nakuru. A local newspaper has since described the place as a "flamingo death camp."
Most attention has focused on the environmental changes to the lakes. Water levels have lowered and concentrations of soda in the water have increased. This increases the risk of toxic bacteria growing there, scientists say.