Little information available on the diet. Haverschmidt (1968) reported the following as food: worms (Vermes) and insects: Orthoptera, Homoptera (Membracidae), and Coleoptera (Lamellicornia). Rarely, the Green Ibis will consume slightly larger prey, such as small frogs, fish, or plants (Hancock et al. 1992).
Seven species of ibises occur sympatrically in Venezuela (Frederick and Bildstein 1992). Frederick and Bildstein (1992) documented niche partitioning among these seven species at one site, where the Green Ibis comprised only 5% of the local ibis population, during the dry season. The Green Ibis usually dispersed to feed alone at the water's edge, never venturing into water deeper than two cm (Frederick and Bildstein 1992). Unlike other species, they fed consistently throughout all hours of the day (Frederick and Bildstein 1992). This species also had high capture rates and probing efficiencies, though they did not walk or probe as much as others, rarely taking arthropods larger than one cm (Frederick and Bildstein 1992). In order to further reduce competition for food, it appears the Green Ibis shifts to forest habitats during the wet season (Frederick and Bildstein 1992).
Green Ibis also use an open wing foraging behavior during the later hours of the day in which the bird opens and closes one or both wings before resuming probes (Ogden and Thomas 1985). This behavior may improve visibility during the hours when the setting sun casts a glare on the shallow water (Ogden and Thomas 1985).