[4] Much remains unknown about this ibis's evolutionary history;[5] however, phylogenetic analyses based on skull morphology and function suggest that it is closely related to the spoonbills.

[5] The plumage is predominantly black with greenish glossing;[4][5] and with purplish tinges on the upper back, hindneck, wings and tail.

[5] 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.

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.

[8] 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.

[4][5] 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.

[17] It typically forages in moist soil, shallow mud[9] and along marshy edges of lagoons[13] and rice fields.

[14] There may also be differences between these sympatric ibis species in specific dry-season probing depths and microhabitat use within the large-scale savannas.

[18] Its tendency to forage in pairs or small groups may be partly attributable to the relatively dispersed distribution of its insect prey in the llanos.

[15] This ibis probably migrates locally during the wet season to higher altitude feeding grounds which may serve as a refuge from the extensive flooding of the lowland grassland.

[17] Its persistence as a primarily terrestrial forager in its semi-aquatic habitat suggests that its relatively dry higher-altitude feeding grounds which remain unflooded in the wet season are sufficiently extensive, or that the dry season is sufficiently long to ensure high annual prey availability in the lowlands.

[15] The sharp-tailed ibis breeds solitarily in gallery forests, where egg-laying is believed to occur from August to September; and fledged offspring remain with their parents until late February.

[19] In a six-year wading bird survey of Masaguaral in the llanos, the sharp-tailed ibis was never seen on the lowland grasslands during the dry-season months of August and December.

[11] Its secretive nesting behaviours probably explains its apparent absence from the open llanos grasslands during the breeding season.

[12] The sharp-tailed ibis has been evaluated by the IUCN as Least Concern since 2004 because this bird does not approach Vulnerable under the population trend and range size criteria.