The American White Ibis (Eudocimus albus) is a species of wading bird in the ibis family Threskiornithidae. It occurs from the mid-Atlantic and Gulf coast of the United States south through most of the New World tropics. This ibis is a middle-sized bird with an overall white plumage, bright red-orange down-curved bill and long legs, and black wing tips that are usually only visible in flight. Males are larger and have longer bills than females. In the breeding season, the range spans along the Gulf and Atlantic Coast and also along the coasts of Mexico and Central America, and birds gather in huge colonies near water. Outside the breeding period, the range extends further inland in North America and also includes the Caribbean. It is also found along the northwestern South American coastline in Colombia and Venezuela. Populations in central Venezuela overlap and interbreed with the Scarlet Ibis. The two have been classified as a single species.
The diet consists primarily of small aquatic prey such as insects and small fishes. Depending on the habitat and the prey abundance, the American White Ibis will adjust its diet although studies have found crayfish to be its preferred source of food in most regions. It is a tactile, non-visual forager whose main foraging behavior is probing its beak into the water to feel for and to capture its prey.
Predominantly monogamous, the American White Ibis pairs up during the breeding season and both parents care for the young, although males tend to engage in extra-pair copulation with other females to increase their reproductive success. Males have also been found to pirate food away from unmated females and juveniles during the breeding season. Human pollution has affected the behavior of the American White Ibis via an increase in the concentrations of methylmercury from release of untreated waste into various habitats. Consumption of methylmercury affects the hormone levels of the birds, disrupting their mating and nesting behavior and leading to lower reproduction rates.