Eudocimus ruber

The scarlet ibis (Eudocimus ruber) is a species of ibis in the bird family Threskiornithidae. It inhabits tropical South America and islands of the Caribbean. In form it resembles most of the other twenty-seven extant species of ibis, but its remarkably brilliant scarlet coloration makes it unmistakable. It is one of the two national birds of Trinidad and Tobago. This medium-sized wader is a hardy, numerous, and prolific bird, and it has protected status around the world. Its IUCN status is Least Concern. The legitimacy of Eudocimus ruber as a biological classification, however, is in dispute. Traditional Linnaean taxonomy classifies it as a unique species, but some scientists have moved to reclassify it as a subspecies of a more general American ibis species, along with its close relative, the American white ibis (Eudocimus albus). The species was first classified by Carl Linnaeus in 1758. Initially given the binomial nomenclature of Scolopax rubra (the name incorporates the Latin adjective ruber, 'red'), the species was later designated Guara rubra and ultimately Eudocimus ruber. Biologically the scarlet ibis is very closely related to the American white ibis (Eudocimus albus) and is sometimes considered conspecific with it, leaving modern science divided over their taxonomy. The two birds each have exactly the same bones, claws, beaks, feather arrangements and other features – their one marked difference lies in their pigmentation. Traditional taxonomy has regarded the two as separate and distinct. Early ornithological field research revealed no natural crossbreeding among the red and white, lending support to the two-species viewpoint. More recent observation, however, has documented significant crossbreeding and hybridization in the wild. 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. They observed individuals of the two species mating and pairing, as well as hybrid ibises with pale orange plumage, or white plumage with occasional orange feathers, and have proposed that these birds be classified as a single species. Hybridization has been known to occur frequently in captivity. However, the two color forms persist in the wild despite overlapping ranges and hybrid offspring having a distinctive color type, so according to the cohesion species concept they would be functionally different species. Some biologists now wish to pair them with Eudocimus albus as two subspecies of the same American ibis. Others simply define both of them as one and the same species, with ruber being a color variation of albus. Adult plumage is virtually all scarlet. The 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. They have a long, narrow, decurved bill. Their legs and neck are long and extended in flight. A juvenile scarlet ibis is a mix of grey, brown, and white. As it grows, a heavy diet of red crustaceans produces the scarlet coloration. The color change begins with the juvenile's second moult, around the time it begins to fly: the change starts on the back and spreads gradually across the body while increasing in intensity over a period of about two years. The scarlet ibis is the only shorebird with red coloration in the world.