The most thorough description of foraging behavior comes from Theodore A. Parker III (reported in Lowery and Tallman 1976) and Isler and Isler (1987), with confirmatory observations by Mark et al. (2008) and Witt and Lane (in press). Foraging behavior involves moving rapidly among bushes in conspecific flocks of 5-15 individuals or mixed-species flocks. They mainly do upright gleaning of lower leaf surfaces and stems of shrubs along the edge of elfin woods. Foraging activity starts in the interior of a shrub and works outwards. They occasionally descend to ground vegetation or into the canopy.
Social and interspecific behavior
T.A. Parker III in Lowery and Tallman (1976) described the conspecific foraging flocks of 5-15 individuals as compact. Additionally, they joined mixed species foraging flocks of tanagers, conebills (Conirostrum), and flowerpiercers (Diglossa). Species in particular listed as flock associates of the Pardusco are Drab Hemispingus (Hemispingus xanthophthalmus); Rufous-browed Hemispingus (Hemispingus rufosuperciliaris); Three-striped Hemispingus (Hemispingus trifasciatus); White-browed Conebill (Conirostrum ferrugineiventre); Blue-backed Conebill (Conirostrum sitticolor); Moustached Flowerpiercer (Diglossa mystacalis); Scarlet-bellied Mountain-Tanager (Anisognathus igniventris); and Chestnut-bellied Mountain-Tanager (Delothraupis castaneiventris).
There is no published information on predation of Nephelornis oneilli, other than a mention that the Aplomado Falcon (Falco femoralis) occasionally was seen in the Acomayo area (Lowery and Tallman 1976).