Main food taken
Takes a wide variety of mostly invertebrate prey. The following description of prey taken is from Zimmer and Isler (2003), much of which is from Wetmore (1972): "Stomach contents from Panama include beetles (Cerambycidae, Curculionidae, Carabidae, Chrysomelidae), cockroaches and their egg cases (Blattidae), grasshoppers (Acrididae), earwigs (Dermaptera), bugs (Heteroptera), lepidopteran larvae, spiders, centipedes (Chilopoda), and two elongate seeds. Additional prey reported from field observations include crickets (Gryllidae) and mantids (Mantidae)." Also occasionally takes small lizards and frogs (Stiles and Skutch 1989). Willis and Oniki (1972) report the consumption of a walking-stick (Phasmatodea); ants occasionally reported (Poulin and Lefebvre 1996).
Microhabitat for foraging
"Lurks in dark undergrowth of wet forest, especially in thickets along streams or edges or at overgrown treefall gaps; in tall, rank second growth, canebrakes" (Stiles and Skutch 1989). The species generally prefers dense vegetation (vine tangles, streamside thickets, etc.), but may forage in more open understory so long as dense patches of vegetation are not too distant (Willis and Oniki 1972, Marcotullio and Gill 1985, SW pers. obs.). Foraging typically occurs at heights of < 1 m (Cody 2000); several sources state that foraging on the ground itself is infrequent (Hilty and Brown 1986, Ridgely and Gwynne 1989, Ridgely and Tudor 1994). The authors’ field observations and the frequent occurrence of muddy legs on captured birds suggest that subspecies exsul in northern Costa Rica does spend a fair amount of time foraging on the ground (see also Cody 2000). The amount of time spent on the ground may be underestimated if the species is only observed when attending antswarms, as Willis and Oniki (1972) did, or if the species is called into view using playback. However, even Willis and Oniki (1972, their table 1) document a substantial number of foraging observations on the ground. In Costa Rica (subspecies exsul) frequently observed foraging at the leafbases of understory palms (Geonoma, Asterogyne spp.), where the birds dig vigorously into the accumulated debris often found there (SW pers. obs.).
Forages at army antswarms only opportunistically, as when a swarm passes through a territory; "The activities of army ants offer no special appeal" (Slud 1964). Not uncommonly found at antswarms on Barro Colorado Island, Panama, perhaps because of high densities of Chestnut-backed Antbird territories (Willis 1985). Infrequently noted at antswarms in Colombia (Hilty 1974).
Food capture and consumption
Willis and Oniki (1972) succinctly summarize the typical foraging behavior of the Chestnut-backed Antbird: "From low perches, it peers carefully at overhanging vegetation or debris and at the ground. Occasionally it stretches the limber neck far up to peer over some obstruction. On long, low flights, it flutters between patches of vegetation, or hurriedly bounds and flutters from one low perch to another to reach new areas." They also state that individuals tend to "peck at their prey, rather than sally or dart for it." Similarly, Zimmer and Isler (2003) state that most prey is obtained via perch-gleaning, although jump-gleaning, pouncing and sallying also are common behaviors. When foraging on the ground, often tosses dead leaves and other debris aside, not unlike leaf-tossers (Sclerurus spp.; Slud 1964, SW pers. obs.).
Legs of larger prey (e.g., orthopterans) are systematically removed before the body is ingested (Willis and Oniki 1972, Zimmer and Isler 2003).
Food selection and storage
Nothing published. Does not store food.
Nutrition and energetic
Little published. Individuals spent > 90% of daylight foraging in a study in Costa Rica (subspecies occidentalis; Marcotullio and Gill 1985).
Metabolism and temperature regulation
Little published. Cloacal temperatures in Panama of 41.5-42.3o C (mean = 41.9, N = 5; Oniki 1972). Willis and Oniki (1972) describe a behavior they called "sunning," but speculated that this may more likely be an effort to dry feathers or perhaps kill parasites rather than a temperature regulation mechanism.
Drinking, pellet-casting, and defecation