Major flamingo breeding event begins on Lake Natron
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.
Pretty in pink
East Africa's lesser flamingos are nomadic and feed in a chain of alkaline soda lakes along the Rift Valley but Lake Natron is the only significant nesting site.
Islands on the huge, shallow soda lake are so inaccessible that researchers' observations of breeding lesser flamingos and their numbers can often only be made from aircraft, or from sightings of young flamingos at other lakes after they have fledged.
While it is difficult to monitor numbers, initial reports estimate that there are hundreds of thousands of birds, meaning this could be the most significant breeding attempt since 2007.
"Large groups have been heard flying towards Lake Natron at night by guides in the Maasai Mara," Ms Ward commented.
A 700,000-strong group of birds that has recently left Lake Bogoria, Kenya, is also thought to have headed to the Lake Natron breeding ground.Precarious position
The success of flamingo breeding events is largely dependent on the availability of food and the right amount of rainfall on the lake.
Some years the flamingos only breed in very low numbers or not at all.
Low water levels caused by drought is thought to be why so few flamingos have bred at the site in recent years.
"When the water level is just right, salt islands are exposed in the centre of Lake Natron where the flamingos can build their nests and raise their young with little disturbance from outside," said Ms Ward.
The caustic environment of the soda lake and isolation of the islands allows the birds to breed without interference from predators.
When water levels are too low, "predators like hyena can reach the nests and cause large numbers of flamingos to desert their nests," explained Ms Ward.
The flamingos' arrival has coincided with heavy rainfall that may threaten the breeding event. If water levels become too high, nests can be flooded.
The lesser flamingos, which are classed as "near-threatened" on the IUCN Red List, face additional environmental challenges from a planned industrial development on Lake Natron.
Although development plans are currently on hold, the IUCN says such disruption to the breeding grounds could threaten the species.
According to Ms Ward: "If this [breeding] attempt is particularly successful it will be a good boost for the flamingo population, but with so many potential hurdles to overcome we will have to wait and hope for good conditions."