Bertoni’s Antbird

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Bertoni's Antbird

Quick Facts

  • Scientific Name: Drymophila rubricollis
  • Spanish Name: Hormiguero de Bertoni
  • Family: Thamnophilidae
  • Known Nicknames: Bertoni's Antwren
  • Average Length: 12–13 cm / 4.7–5.1 in
  • Average Weight: 11–14 g / 0.39–0.49 oz
  • Wingspan: N/A
  • Key Feature: Male has black throat and breast with white streaks; female has rufous crown and olive-brown upperparts
  • Primary Diet: Insectivore
  • Range: Southeastern Brazil, eastern Paraguay, and northeastern Argentina
  • Habitat: Understory of humid Atlantic Forest and bamboo thickets
  • Social Structure: Solitary or in pairs
  • Nesting/Breeding: Cup nest built in low vegetation
  • Conservation Status: Least Concern (LC)
  • Population Trend: Stable

Bertoni's Antbird (*Drymophila rubricollis*) is a striking and elusive inhabitant of the Atlantic Forest in southeastern Brazil, Paraguay, and northeastern Argentina. This small, long-tailed passerine is distinguished by its unique "ruby-throat": males boast a vivid, deep crimson patch on the throat and upper chest, contrasting sharply with their otherwise black-and-white streaked body, while females are more subdued with buffy underparts and a paler, often hidden rufous throat. A special feature is its strong association with bamboo thickets, where it forages actively for insects and spiders, often clinging acrobatically to vertical stems. Its loud, descending song—a series of clear, whistled notes—is a hallmark of its dense, humid habitat, making it easier to hear than to see, and it is a key species for birders seeking the unique endemics of the South American highlands.

Fun Facts

Bertoni’s Antbird has a peculiar habit of following army ant swarms, but unlike many ant-following birds that snatch fleeing insects, it specializes in picking off the ants’ parasitic flies that hover nearby. Its scientific name, *rubricollis*, means “red-necked,” referring to the male’s striking rusty collar, which it fluffs aggressively during territorial disputes. Remarkably, it can mimic the calls of other antbird species to confuse rivals or lure in prey. The species is also an expert at “anting”—rubbing ants on its feathers to secrete formic acid as a natural insecticide and antifungal treatment.

Habitats & Distribution

Bertoni's Antbird inhabits the understory and edges of humid montane forests, particularly favoring areas with dense bamboo thickets (Guadua species) and tangled vine growth. It is typically found at elevations ranging from 600 to 2,200 meters, where it forages low in the vegetation. Its geographical range is restricted to the Atlantic Forest region of southeastern South America, occurring primarily in northeastern Argentina (Misiones Province), eastern Paraguay, and adjacent southeastern Brazil (from southern São Paulo state south to Rio Grande do Sul). The species is considered endemic to this relatively small, fragmented area of the Atlantic Forest biome.

Behaviours & Reproduction

Bertoni’s Antbird is a socially monogamous species, typically observed in stable pairs that defend a shared territory year-round within the dense understory of Atlantic Forest. Mating occurs during the austral spring and summer, with courtship involving duetted vocalizations and mutual preening. The pair builds a deep, cup-shaped nest woven from plant fibers and moss, often suspended in a fork of bamboo or small branches. Females lay two white eggs with reddish speckles, and both parents share incubation duties for about 14–17 days. After hatching, the adults cooperatively feed the chicks, which fledge after roughly 12–14 days. A unique reproductive strategy is their reliance on bamboo thickets for nesting and foraging, which ties their breeding success to the mast seeding cycles of bamboo, though this is more related to habitat selection than a direct reproductive adaptation. No cooperative breeding or extra-pair copulations have been documented in this species.

Diet

Bertoni's Antbird is an insectivorous bird that primarily forages for arthropods, with a diet heavily focused on ants, beetles, caterpillars, spiders, and other small invertebrates gleaned from leaf litter and low vegetation. A particularly interesting aspect of its diet is its strong association with army ant swarms, where it acts as an obligate or near-obligate ant-follower, capturing prey flushed by the moving columns rather than consuming the ants themselves. This specialized feeding strategy means the bird relies on the disturbance created by the swarm to access hidden insects and spiders that flee the ants, making its diet seasonally dependent on the unpredictable movements of these ant colonies. Additionally, it occasionally supplements its diet with small fruits and seeds, but invertebrates make up the vast majority of its nutritional intake.

Colors

Bertoni's Antbird has a rufous throat and upper breast contrasting with a white belly and dark gray upperparts. The male shows a black mask and white supercilium, while the female is duller with buffy tones. Its black-and-white streaked back and wings provide disruptive camouflage in dappled understory light.

Distribution Map

Places linked to this species. A sighting is never guaranteed.