In form, it resembles most of the other twenty-seven extant species of ibis, but its remarkably brilliant scarlet coloration makes it unmistakable.

[7] Early ornithological field research revealed no natural crossbreeding among the red and white, lending support to the two-species viewpoint.

Researchers Cristina Ramo and Benjamin Busto found evidence of interbreeding in a population where the ranges of the scarlet and white ibises overlap along the coast and in the Llanos in Colombia and Venezuela.

A small but reliable marking, these wingtips are a rich inky black (or occasionally dark blue) and are found only on the longest primaries[10] – otherwise the birds' coloration is "a vivid orange-red, almost luminous in quality.

[10] Though it spends most of its time on foot or wading through water, the bird is a very strong flyer:[14] they are highly migratory and easily capable of long-distance flight.

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.

[10] Outlying colonies have been identified in the coastal areas of the states of Espírito Santo, Rio de Janeiro, São Paulo (for example in the Santos-Cubatão mangroves of the Baixada Santista district), Paraná and Santa Catarina.

[21] Scarlet ibis vagrants have been identified in Belize, Ecuador, and Panama; Aruba, Cuba, Dominica, Grenada, and Jamaica; sightings have even been made in the United States.

[1] The species may well have been a natural vagrant to the Gulf Coast in the 19th century or earlier – in The Birds of America, John James Audubon made brief remarks regarding three rubra specimens he encountered in Louisiana.

[26] To attract a female, the male will perform a variety of mating rituals such as "preening, shaking, bill popping, head rubbing, and high flights.

As with most birds, mating does not involve any coupling or insertion: instead, a transfer of seminal fluids occurs during external contact between the cloacal openings.

[11] Popularly imagined to be eating only shrimp, a recent study in the Llanos has found that much of their diet consists of insects, of which the majority were scarabs and ground beetles.

[29] They do, however, eat much shrimp and other similar fare like ragworms (Nereis), mollusks (such as Melampus), small crabs (Aratus, Uca and Ucides) and other crustaceans, such as crayfish.

[10] 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.

[1] Though several local populations appear to be in decline, global totals remain relatively large and the current rate of losses is not considered a threat to the species' survival.

[1] Nonetheless, recent losses by established populations in French Guiana have become a concern for conservationists, and in Brazil the bird has been included on a national list of endangered species.

[39] Using the bird as a literary symbol, American author James Hurst composed a popular short story, "The Scarlet Ibis" (1960).