Flamingos reach sexual maturity several years after hatching and usually begin to breed at about six years of age.
Flamingo colonies may breed at different times of the year. Breeding success is based on synchronous nesting of a flamingo colony so that chicks of a colony hatch around the same time in any one year. Colonies very rarely nest more than once a year.
Breeding and nest building may depend on rainfall and its effect on food supply.
Groups of flamingos perform ritualized stretching and preening when courting begins.
Males group together and often run with bills pointed toward the sky and necks held straight out.
Birds interested in one another call to each other frequently and in unison.
Pair bonding is very strong, and flamingos may be monogamous. However, flamingos have been observed to mate with more than one partner.
A female will most often initiate copulation by walking away from the group. A male follows close behind.
The female stops, lowers her head, and spreads her wings. This behavior is an invitation to the male to mount her.
Mating occurs in the water. The male jumps onto the female's back from behind, firmly planting his feet on her wing joints.
After mating, the male stands on the female's back, then jumps off over her head.
Flamingos build nest mounds made of mud, small stones, straw, and feathers. These mounds can be as high as 30 cm (12 in.).
Mound building begins up to six weeks before the eggs are laid.
Using their bills, both male and female participate in mound building by bringing mud and other objects toward their feet.
As they slowly construct the mound, the parents make a shallow well on the top, where the female will lay the egg.
Mound building continues during incubation, as the flamingos pick up materials close to the nest.