Courtship is most often seen among individuals that change partners often or are promiscuous. A spectrum of pairing relationships is seen. Some birds have a long-term partner throughout the year; others form pairs during periods of courtship and nest attendance. How long a relationship lasts is affected by many factors, including addition and removal of adults, maturation of juveniles, and occurrence of trios and quartets. In most pairs, both individuals usually construct and defend the nest site. In rare cases, one individual undertakes both duties. Within trios, the dominant pair begins the nesting process by choosing and then defending the site.
Males and females co-operate in building a pillar-shaped mud nest, and both incubate the egg laid by the female. Both parents also take turns incubating the egg. Upon hatching, the chicks have gray plumage; they do not gain the typical pink adult coloration for 2-3 years. Both male and female flamingos can produce a nutritious milk-like substance in their crop gland to feed their young.