The sharp-tailed ibis (Cercibis oxycerca) is a species of ibis native to open wet savannas in parts of northern South America.
Taxonomy and systematics The sharp-tailed ibis is monotypic, being the only representative of the genus Cercibis. Much remains unknown about this ibis's evolutionary history; however, phylogenetic analyses based on skull morphology and function suggest that it is closely related to the spoonbills.
Description This large ibis measures 75–86 cm in length, with males being slightly larger than females. In adult males, the flat wing measures 390–415mm lengthways, and the culmen measures 156–168mm from the base of the bill. In adult females, the wing is 376–413mm long and the culmen 144–197mm. The species is distinguished by its notably long tail, the longest among all extant ibis species; measuring 250–301mm in males and 256–272mm in females. The tail projects beyond the tips of the folded wings when the ibis stands; and beyond the trailing legs in flight. The plumage is predominantly black with greenish glossing; and with purplish tinges on the upper back, hindneck, wings and tail. The forehead and cheek region are occasionally greyish brown. Juveniles appear similar to adults, but their plumage lacks a metallic sheen. The bill, legs, toes, and bare facial skin are orangey-red; the throat is yellowish-orange, and a feathered grey strip extends below the eye from the lower mandible. An inconspicuous fuzzy crest extends down the back of its head and upper neck. The iris is greyish red, but is sometimes scarlet red, which may be associated with breeding. Nothing is however known of changes in soft part colourations as part of courtship. Overall, the sharp-tailed ibis is superficially similar to many sympatric ibises such as the glossy ibis and the bare-faced ibis; but clearly differs through its longer tail and larger body size. This ibis is particularly vocal. The call is a loud, distinct single or double cuk or turuck; or kut and kut-kaaaoh. These calls resemble the sound of a saxophone or toy trumpet. Flight calls have been transcribed as a long drawn-out tuuut, as a cuk cuk cuk cuk and as a loud nasal TUUR-DEE. The male is believed to utter the TUUR element, and the female utters the following DEEE in response. The timbre of the TUUR-DEE call has earned it the local Spanish name Tarotaro. The sharp-tailed ibis has a slow, laboured flight; with individuals flying low above the ground and often only covering short distances such as between neighbouring trees. However, they have been observed to fly across wide-open expanses of grassland toward roosting or feeding sites. Due to its noisy wing beating, it is often heard before coming into view.
Distribution and habitat The sharp-tailed ibis inhabits wet lowland savannas and riverbanks of northern South America east of the Andes, at less than 300-500m above sea level. It is native to Venezuela, eastern Colombia, southwestern Guyana, Brazil and Suriname. In Venezuela, it is typically found along or near the Orinoco and Apure rivers. In the llanos of eastern Colombia, it is found along the Casanare and Cravo Sur rivers, as well as the Colombian stretch of the Apure. In Brazil, it often occurs to the northwest of the Amazon and frequents the grasslands near to the Rio Negro and Rio Branco. However, it is also present to the west near Rio Guanco and to the south in northwest Mato Grosso. This ibis also sometimes uses gallery forests in which to roost and breed. This ibis is patchily distributed throughout its global range and despite a relatively large total population; it is generally uncommon on a local scale and is considered to be the least numerous ibis species in the Venezuelan llanos. It is however more abundant there during the rainy season. It does not associate with other wading bird species, often distancing itself from its heterospecifics. It is primarily found in male-female pairs and in small intraspecific groups comprising three to five individuals. Despite this ibis's territoriality, individuals very rarely forage alone. The two individuals of a dyad differ markedly in body size, which suggests that they constitute a paired male and female given the differences in biometrics between the sexes. The groups of more than two individuals appear to comprise a paired male and female along with their juvenile offspring. In observations of flocks of three, the individual assumed to be the offspring is notably smaller with less developed facial colourations.
Ecology
Food and feeding
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