White-flanked Antwren

The White-flanked Antwren, Myrmotherula axillaris, is a diminutive bird, part of the Thamnophilidae family, known for its characteristic antbirds. This species exhibits sexual dimorphism, with males and females donning distinct plumage. The males are adorned with a dark gray upper body and a blackish tail with white tips, while their underparts are a striking contrast of black and white. Females, on the other hand, display a mottled pale olive-brown face with olive-brown upperparts that transition to a reddish yellow-brown on the rump, and their underparts are a blend of white, rich buff, and reddish brown.

Identification Tips

When identifying the White-flanked Antwren, look for the male's dark gray upperparts and blackish tail with white tips, and the female's olive-brown to reddish yellow-brown upperparts. Both sexes have the distinctive white flanks that give the species its name. Juvenile males resemble adult females but with a mix of yellow-brown and gray upperparts and wings, and mixed white and gray underparts.

Habitat

This species thrives in the understorey and mid-storey of evergreen forests, including terra firme, várzea, igapó, and transitional types, as well as secondary woodlands. They are known to inhabit a range of altitudes from sea level up to about 1,400 meters, with specific altitudinal limits varying by region.

Distribution

The White-flanked Antwren is widely distributed from Honduras to Panama in Central America, across every mainland South American country except Argentina, Chile, Paraguay, and Uruguay, and is also found on Trinidad.

Behaviour

The White-flanked Antwren is a year-round resident, known for its active foraging behavior. It feeds on arthropods, primarily insects and spiders, and is often seen foraging in dense vegetation, from about 2 to 12 meters above the ground. It typically forages alone, in pairs, or in family groups, and is frequently part of mixed-species feeding flocks.

Song & Calls

The song of the White-flanked Antwren varies among subspecies, with some delivering a rapid series of abrupt notes and others a countable series of whistles. Calls are relatively consistent across subspecies, including a sharp 'wheep', a short 'pip', a longer 'chirr', and a rattle.

Breeding

Breeding seasons vary across the range, generally falling within February to December. The nest is a deep cup made of dead leaves and leaf skeletons, suspended in a branch fork and camouflaged by overhanging leaves. Clutch size is typically two eggs, which are incubated by both parents.

Similar Species

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Diet and Feeding

The White-flanked Antwren's diet consists mainly of arthropods. It forages actively, gleaning leaves and taking prey from vine tangles and along branches. Occasionally, it may follow army ant swarms to capture prey.

Conservation status

The IUCN has classified the White-flanked Antwren as Least Concern. It has an extremely large range and is considered fairly common to common in most of its range. It is found in many protected areas and seems to be more tolerant of disturbance than other congeners.