On rare occasions, forages in shrubby areas with small mixed species parties containing Conirostrum species as well as other tanagers, new world warblers and tyrant-flycatchers (Hilty 2011). Forages from near the ground to treetops searching for insects and nectar among flowers and tips of branches (Isler and Isler 1987). In Peru, a behavior of entering the flowers of Tristerix mistletoe has been observed (Graves 1982). The bill remains open after it pierces the flower (Isler and Isler 1987). During the rainy season it forages on the ground near the treeline, hops or flutters from place to place, and often remains on the ground for some time before flying up to shrubs (Isler and Isler 1987). Prefers Brachyotum shrubs, Gynoxys bushes gardens, and eucalyptus (Fjeldså and Krabbe 1990).
Usually are found in pairs during breeding season but typically by themselves during non-breeding period, holding their territory against nectar feeders (Hilty 2011) fulfilling a specific niche in the environment where they are found.
Social and interspecific behavior
They take part in high stress competitive interactions, not only with other Diglossa brunneiventis individuals but also with other species of the flowerpiercers and species from different groups like hummingbirds (Trochilidae) and warblers (Parulidae) (Isler and Isler 1987). Individuals are aggressive towards each other and to other flowerpiercer species and maintain a territory year round (Isler and Isler 1987). They are not commonly found in mixed-species flocks, except for the Colombian population (Moynihan 1979). Flies low between patches of scrub (Moynihan 1979).