Arthropods constitute the bulk of the diet, although seeds, fruit, and small vertebrates are consumed occasionally (Shubart et al. 1965, Manhães et al. 2010). Stomach contents from southern Mexico revealed arthropods typical of tree trunks such as ants (especially Pheydole spp.), small beetles, pseudoscorpions, and spiders, with lesser quantities of Hemiptera, termites, plant hoppers (Homoptera) and trace quantities of other arthropods or snails (Puebla-Olivares 2001). A study from Minas Gerais, Brazil, found diet to consist primarily of adult and larval beetles (64%) and roach egg cases (24%), in addition to small quantities of bugs, flies, ants, plant hoppers, and termites (Durães and Marini 2005). Another study in southeastern Brazil reported a preponderance (78%) of Hymenoptera, especially ants (58%; Manhães et al. 2010), whereas another study from that region reported a preponderance (49%) of adult and larval beetles (Lopes et al. 2005). Most prey are small (< 5 mm), but some exceed 17 mm in length, and the species may preferentially select larger prey (¿ekercio¿lu et al. 2002).
The Olivaceous Woodcreeper forages while rapidly hitching linearly or spirally up trunks or around large limbs (Skutch 1967), perhaps especially on tree species that have relatively smooth bark, such as Cecropia spp. or Ficus spp. (Dickey and van Rossem 1938, Hilty 2003), although trees with rough bark or having their branches covered with mosses or lichens are selected preferentially in some areas (Brooke 1983, Soares and Anjos 1999). This species forages along branches larger than those used by other species (Buskirk 1976) and larger than what is available in the habitat (Brooke 1983), but some individuals forage along thick vines (Soares and Anjos 1999), and the species uses slimmer trunks and branches than do larger woodcreeper species that co-occur with it (Brooke 1983). Dead trees tend to be avoided (Soares and Anjos 1999).
This species is chiefly a bird of mid-strata and the sub-canopy—consider mean foraging heights above ground of 8.4 m in eastern Peru (Munn and Terborgh 1979) and 7.5 m in the Atlantic Forest (Brooke 1983)—but some birds will descend to the understorey (Graber and Graber 1959, Brooke 1983, Peres and Whittaker 1991, Piratelli et al. 2000), and foraging height may vary by region (Marantz et al. 2003). Still, this species tends to forage higher, on average, than do much larger woodcreeper species that co-occur with it. Brooke (1983) reported that they hitch upward along a trunk an average of 2 m before moving to another tree or branch. Prey is captured in one of two ways: either an arthropod is taken midair during short, erratic sallies after it flushed during the bird's rapid ascent or it is pecked or gleaned from bark surface (Slud 1964, Skutch 1967, Pierpont 1986). Only rarely does a bird search a cluster of dead leaves suspended in a tree (Pierpont 1986).
The Olivaceous Woodcreeper does not follow army ants in Amazonia (Pierpont 1986), but studies have documented the species’ presence at swarms of both Eciton burchelli and Labidus praedator in s.outhern Mexico (Coates-Estrada and Estrada 1989), Costa Rica (Kumar and O’Donnell 2007), southwestern Panama (Roberts et al. 2000), and southeastern Brazil (Faria and Rodrigues 2009). At the last site, this woodcreeper was detected at 31% of ant swarms, but it tended to remain on a swarm’s periphery (Faria and Rodrigues 2009). Pizo and Melo (2010) reported that the species attended swarms less often than would be expected given its abundance.
Metabolism and Temperature Regulation
Little is known about the specific metabolism of this species. Nevertheless, given its body temperature, which varies between 36.0º and 43.6ºC (Oniki 1980, 1981, Oniki and Willis 1999, 2001), the metabolic rate is likely to be high.