Lakes such as Natron and Bogoria hold water heavily loaded with sodium carbonate, giving pH values that can exceed ten, and temperatures raised by geothermal inflow. Few organisms tolerate the chemistry, which is precisely the point: the cyanobacterium Arthrospira flourishes there without competition, and the lesser flamingo has a bill built to filter it.
The birds cope with the conditions rather than resisting them chemically. Their leg skin is thick and tough, and they rely on freshwater springs and seeps at lake edges for drinking and rinsing. Salt glands above the eyes excrete excess sodium. Concentrated in a handful of usable lakes, the population is unusually vulnerable, and Lake Natron in Tanzania is the principal breeding site, with other African colonies at Etosha Pan, Makgadikgadi Pan and Kamfers Dam.
The frequent claim that these lakes calcify or mummify animals that touch them overstates matters. Preserved carcasses found on the shores are birds that died and then dried in an evaporative, alkaline crust, not animals killed on contact.