The Scarlet Ibis (Eudocimus ruber) inhabits tropical South America and islands of the Caribbean. It looks like most of the other twenty-seven species of ibis, but its colour makes it unmistakable!
Biologically the Scarlet Ibis is very closely related to the American White Ibis. 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. Observation has documented significant crossbreeding and hybridisation in the wild. Individuals of the two species have produced hybrid ibises with pale orange plumage, or white plumage with occasional orange feathers. Hybridisation has been known to occur frequently in captivity.
Adult plumage is virtually all scarlet although the feathers may show various tints and shades. A juvenile Scarlet Ibis is a mix of grey, brown, and white. As it grows, a heavy diet of red crustaceans produces the scarlet colouration. The colour 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 colouration in the world.
Adults are 55--63 centimetres , and the males, slightly larger than females, typically weigh about 1.4 kilograms. Their bills are also on average around 22% longer than those of females. The life span of the Scarlet Ibis is approximately sixteen years in the wild and twenty years in captivity. An adult Scarlet Ibis has a wingspan of around 54 centimetres. The bird is a very strong flyer and easily capable of long-distance flight. They move as flocks in a V formation.
Flocks gather in wetlands and other marshy habitats, including mud flats, shoreline and rainforest.
Mating pairs build nests in a simple style, typically "loose platforms of sticks"of a quality sometimes described as "artless." They roost in leaf canopies, mostly preferring the convenient shelter of young waterside mangrove trees.
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. After a gestation period of five to six days, the female lays a clutch of three to five smooth, matte eggs which typically incubate for 19--23 days. After a successful courtship, pairs remain faithful and cohabitant, sharing parental responsibilities for the young.
Their distinctive long, thin bills are used to probe for food in soft mud or under plants. Popularly imagined to be eating only shrimp, a recent study in Llanos has found that much of their diet consists of insects, of which the majority were scarabs and ground beetles . One species in particular, a scarab beetle Dyscinetus dubius, formed a large part of the diet. In contrast, the diet of the co-occurring American White Ibis there differed, the latter consuming more bugs, fish and crustaceans. They do, however, eat much shrimp and other similar fare like small crabs, molluscs and other crustaceans. The large quantity of shrimp and other red shellfish produces a surfeit of astaxanthin, a carotenoid which is the key component of the birds' red pigmentation. When kept in zoos, the birds' diet is often supplemented by beetroots and carrots to maintain colour vibrance in their plumage.
The Llanos are notable in that these wetland plains support seven species of ibis in the one region. Here, Scarlet Ibis are the most aggressive, and attack other species to steal their food. They have also been observed trailing White-faced Whistling Duck (Dendrocygna viduata) and domestic livestock, and catching insects disturbed by them.
The Scarlet Ibis is a sociable and gregarious bird, and very communally-minded regarding the search for food and the protection of the young. They live in flocks of thirty or more. Members stay close, and mating pairs arrange 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 share time among other avian creatures, gaining additional safety through numbers: storks, spoonbills, egrets, herons and ducks are all common companions during feedings and flights.
