Scarlet ibises are medium-sized wading birds with remarkably brilliant scarlet coloration. Their feathers may show various tints and shades, but only the tips of their wings deviate from their namesake color. A small but reliable marking, these wingtips are a rich inky black (or occasionally dark blue) and are found only on the longest primaries - otherwise, the birds' coloration is "a vivid orange-red, almost luminous in quality." Scarlet ibises have red bills and feet however the bill is sometimes blackish, especially toward the end. A juvenile Scarlet ibis is a mix of grey, brown, and white. As it grows, a heavy diet of red crustaceans produces scarlet coloration.
Scarlet ibises are found throughout South America and the Caribbean islands. Native flocks exist in Brazil; Colombia; French Guiana; Guyana; Suriname; and Venezuela, as well as the islands of the Netherlands Antilles, and Trinidad and Tobago. There is an outlying colony in the Santos-Cubatão mangroves of Baixada Santista district in southeastern Brazil, which is considered critically endangered. Scarlet ibises perform seasonal shifts and migrations within their range. they inhabit wetlands and other marshy habitats, including mudflats, mangroves, shoreline, shallow bays, lakes, estuaries, and rainforest.
Scarlet ibises are sociable and gregarious birds. They live in flocks of thirty or more. Members stay close, and mating pairs locate their nests in close proximity to other pairs in the same tree. For protection, flocks often congregate in large colonies of several thousand individuals. They also regularly participate in mixed flocks, gaining additional safety through numbers: storks, spoonbills, egrets, herons, and ducks are all common companions during feedings and flights. Scarlet ibises are highly migratory and are able to fly on very long distances; during migration, they move as flocks in a classic V formation. When flying the birds soar and glide usually at great heights and speeds. Scarlet ibises are active during the day and spend most of their time foraging. When feeding, they use their distinctive long, thin bills to probe for food in soft mud or under plants. When they need to communicate with each other, the birds will make a honking noise. The nestlings have a shrill cry used to let parents know that they are hungry.
Scarlet ibises are carnivores and mainly feed on insects especially scarabs and ground beetles. They also consume shrimp, small crabs, mollusks and other crustaceans.
Scarlet ibises are serially monogamous; they form pairs that remain faithful within a single breeding season and cohabitant, sharing parental responsibilities for the young. To attract a female, the male will perform a variety of mating rituals such as "preening, shaking, bill popping, head rubbing, and high flights. In southeastern Brazil, Scarlet ibises gather in colonies in mid-September and build nests at the beginning of November. Egg-laying within the colony is usually synchronous, with females laying eggs in three waves in early November, late December, and late January. Mating pairs build nests in a simple style, typically "loose platforms of sticks" sometimes described as "artless". They roost in leaf canopies, mostly preferring the convenient shelter of young waterside mangrove trees. Scarlet ibises like wet, muddy areas such as swamps, but for safety, they build their nests in trees well above the water. If they can, they nest on islands, where their eggs and chicks are less likely to be in danger from predators. After mating there is a gestation period that lasts 5 to 6 days; after that, the female lays a clutch of 3 to 5 smooth, matte eggs which typically incubate for 19-23 days. The chicks are altricial; they are hatched helpless and with their eyes closed. The young fledge 35-40 days after hatching and become independent when they are 75 days old.
Scarlet ibises have protected status throughout the world, however, despite that, populations of these beautiful birds are declining due to overhunting, collection of eggs and selling of young as pets. Another main threat to this species is habitat loss due to heavy pollution and the loss of nesting, foraging and feeding grounds. Scarlet ibises also suffer from disturbance on breeding and foraging areas because of recreational activities.
According to the What Bird resource, the total population size of the Scarlet ibis is 100,000 to 150,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.