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The American white ibis (''Eudocimus albus'') is a species of bird in the ibis family, Threskiornithidae. It is found from North Carolina via the Gulf Coast of the United States south through most of the coastal New World tropics. This particular ibis is a medium-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. The breeding range runs along the Gulf and Atlantic Coast, and the coasts of Mexico and Central America. 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 by some authorities as a single species. Their diet consists primarily of small aquatic prey, such as insects and small fishes. Crayfish are its preferred food in most regions, but it can adjust its diet according to the habitat and prey abundance. Its main foraging behavior is probing with its beak at the bottom of shallow water to feel for and capture its prey. It does not see the prey. During the breeding season, the American white ibis gathers in huge colonies near water. Pairs are predominantly monogamous 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 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, which is released into the environment from untreated waste. Exposure to methylmercury alters the hormone levels of American white ibis, affecting their mating and nesting behavior and leading to lower reproduction rates. ==Taxonomy== The American white ibis was one of the many bird species originally described by Carl Linnaeus in the 1758 10th edition of his ''Systema Naturae'', where it was given the binomial name of ''Scolopax albus''. The species name is the Latin adjective ラテン語:''albus'' "white". Alternative common names that have been used include Spanish curlew and white curlew.〔 English naturalist Mark Catesby mistook immature birds for a separate species, which he called the brown curlew. Local creole names in Louisiana include ''bec croche'' and ''petit flaman''. Johann Georg Wagler gave the species its current binomial name in 1832 when he erected the new genus ''Eudocimus'', whose only other species is the scarlet ibis (''E. ruber''). There has long been debate on whether the two should be considered subspecies or closely related species, and the American Ornithologists' Union considers the two to be a superspecies as they are parapatric.〔 The lack of observed hybrids was a large factor in the view that the species were separate.〔 However, in a field study published in 1987, 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 region of 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; their proposal that these birds be classified as a single species, has been followed by least one field guide. Hybrid ibises have also been recorded in Florida, where the scarlet ibis has been introduced into wild populations of American white ibis. Birds of intermediate to red plumage have persisted for generations.〔 Ornithologists James Hancock and Jim Kushlan also consider the two to be a single species, with the differences in plumage, size, skin coloration and degree of bill darkening during breeding season forming the diagnostic characters. They have proposed the populations recontacted in northwestern South America after a period of separation, and that the color difference is likely due to the presence of an enzyme that allows uptake of pigment in the diet. They have questioned whether white-plumaged birds of South America are in fact part of the ''ruber'' rather than the ''albus'' taxon, and acknowledge that more investigation is needed to determine this.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「American white ibis」の詳細全文を読む スポンサード リンク
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