The White-rumped Tanager primarily is an insectivore, but also eats fruit from species of Byrsonima, Anonna, Eugenia, and Erythroxulum; they also seasonally capture flying ants and termites (Isler and Isler 1999). Because their habitat experiences intense seasonality, they often have to switch food types, as well as substrate type and foraging mode (Ragusa-Netto 1997). They most frequently eat caterpillars (by gleaning bushes or trees), followed by larvae, orthopterans, coleopterans, and spiders (Ragusa-Netto 1997).
Usually, the substrates from which arthropod prey is captured are green leaves (39% of observations) or bark (34% of observations; Ragusa-Netto 1997). When the dry season begins (from June-September), they begin foraging mostly on bark (Ragusa-Netto 1997). A study by Ragusa-Netto (1997) on Cypsnagra foraging behaviors found that they also feed on flowers from the tree Pouteria torta during July-August.
Food capture and consumption: The most common foraging mode is gleaning, but these tanagers also employ probing in bark (Ragusa-Netto 1997). A less frequent foraging mode was sallying, which only was observed in September and October when the White-rumped Tanager chased flying ants and termites, which emerge at the end of the rainy season (Ragusa-Netto 1997).