Many thousands of lesser flamingos have flocked to Tanzania's Lake Natron to begin nesting.
Early reports suggest that this could become the most significant breeding event since 2007.
But the flamingos' breeding success will depend on a combination of environmental factors.
The gathering is one of nature's "fantastic spectacles", said Sarah Ward, of the University of Southampton.
Three-quarters of the world population of lesser flamingos (Hoenicopterus minor) live in East Africa and use Lake Natron as their nesting site.
"Large breeding events involving over a million [lesser] flamingos are not unusual if conditions at Lake Natron are suitable and if the flamingos are in good health," explained Ms Ward, a PhD research student studying the relationship between East African lakes and lesser flamingo populations at the university's Institute of Complex Systems Simulation (ICSS) and geography departments.