Historically, the olive ibis was included in various genera such as Geronticus, Comatibis and Harpiprion before finally being classified among the Bostrychia.

[6] B. o. cupreipennis and rothschildi are roughly equal in size, olivacea is slightly larger, and akleyorum is the largest of all subspecies and also has the longest bill.

[6] The number of available specimens of this species is however considered too small to confirm whether this pattern of size variation among the subspecies holds generally.

[10] The olive ibis has a distinctive brown crest which is purple near the neck, clearly distinguishing it at close range from the similar hadada and spot-breasted ibises.

[12] This ibis has a straggling but strong and powerful flight with a wingbeat that is apparently similar to that of night herons.

[13] The natal young have uniformly brownish-black down, and their bare facial patches reportedly have the same pattern and spatial extent relative to the feathered tracts as those of adults.

The call is a distinctive, loud, squawky “gar-wa”, repeated several times and uttered in flight high above the trees.

[3] This ibis remains silent during the day when feeding in its typical habitat, so is difficult to detect at this time.

[3] This species is patchily distributed in dense forests from the West to East coast of tropical Africa.

The countries in which it natively occurs are Cameroon, the RCongo, DRCongo, Cote d’Ivoire, Gabon, Ghana, Kenya, Liberia, Nigeria, Sierra Leone and Tanzania, besides Príncipe and São Tomé islands.

[16] It is readily distinguished from the similar hadada ibis by elevation of habitat since the latter occurs at altitudes in this region of less than 6,000 feet.

[8] The olive ibis is probably largely sedentary, although short migrations appear to happen in Liberia in extremely dry weather; during which individuals move from northern Grand Gedeh county to regions further south such as Glaro, Sapo and Sinoe.

[3] The olive ibis preferentially roosts in tops of large dead trees at night such as silk-cotton and probably uses the same ones daily.

[19] In both cases, the nest measured 20–40 cm in diameter, was situated 2-4m above the surface of the water and precariously balanced in slender branches.

Generally, the nest is loosely composed of dead branches supported on a tree limb and appears surprisingly unstable for a bird of its size.

[3] When disturbed, the olive ibis makes no sound as it flies away[12] and hides itself in thickly leaved trees.

[22] However, numerous non-living specimens have been kept in museums around the world; such as in Brussels, Paris, Philadelphia, Leyden and Lisbon.

[1] It is not globally threatened, but the putatively small world population is considered to be declining due to deforestation and hunting.

[1] Because of the difficulty in identifying wild individuals, this species may be more common than documented;[3] especially also considering its frequently heard vocalisations.