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Endémique

• Scientific Name: Myrmotherula unicolor
• Spanish Name: Hormiguerito unicolor
• Family: Thamnophilidae
• Known Nicknames: Unicolored Antwren
• Average Length: 9–10 cm / 3.5–3.9 in
• Average Weight: 8–10 g / 0.28–0.35 oz
• Envergure : N/A
• Key Feature: Uniformly gray plumage with a white throat and belly in males; females are brownish with a buffy underside
• Régime alimentaire principal : Insectivore
• Range: Southeastern Brazil (from Bahia to Santa Catarina)
• Habitat: Understory and mid-story of humid lowland Atlantic Forest
• Social Structure: Often found in pairs or small family groups, sometimes joining mixed-species flocks
• Nesting/Breeding: Cup-shaped nest placed in a fork of a small tree or shrub
• Statut de conservation : Quasi menacé (NT)
• Évolution démographique : En baisse

The Unicolored Antwren (*Myrmotherula unicolor*) is a small, cryptically colored passerine bird endemic to the lowland forests of southeastern Brazil, most famously the Atlantic Forest. As its name suggests, this species lacks the bold streaking or spotted patterns common among its antwren relatives, instead sporting a uniform, soft slate-gray plumage in males and a warm, unmarked olive-brown in females, with a faint pale eye-ring that adds a touch of definition to its otherwise plain face. A special feature of this bird is its highly specialized foraging behavior: it is an obligate army ant follower, rarely straying far from swarms of Eciton burchellii, where it deftly snatches insects and spiders flushed from the leaf litter, moving with quick, acrobatic hops through the understory. Despite its subtle appearance, the male’s distinctive, high-pitched, accelerating trill—often described as a "laughing" call—is a reliable clue to its presence in its dense, humid habitat, making it a sought-after gem for birdwatchers exploring Brazil’s coastal forests.

Faits amusants

The Unicolored Antwren engages in a bizarre “ant-following” behavior, but unlike classic antbirds, it rarely eats the army ants themselves—instead, it snatches insects and spiders that flee in panic from the raiding swarm, often perching just inches above the chaos to pluck prey mid-air. Males perform a peculiar “wing-flash” display during courtship and territorial disputes, rapidly flicking their wings open to reveal bright white underwing patches that contrast starkly with their otherwise slate-gray plumage. One of its most unique adaptations is a faint, high-pitched “squeak” call so quiet it’s often mistaken for a cricket, allowing it to communicate without attracting predators. Additionally, this species has an unusually strong preference for bamboo thickets within Atlantic Forest understory, where it clings upside-down to stems like a tiny acrobat, probing leaf nodes for hidden arthropods.

Habitats et répartition

The Unicolored Antwren is restricted to the Atlantic Forest of southeastern Brazil, where it occupies lowland and foothill forests up to about 1,000 meters in elevation. Its habitat consists of humid, primary and mature secondary forests, often with dense undergrowth and vine tangles, as well as forest edges and adjacent tall restinga woodlands. Geographically, its range extends from southern Bahia south through Espírito Santo, Rio de Janeiro, and São Paulo, reaching into northeastern Paraná.

Comportements & Reproduction

The Unicolored Antwren is generally monogamous, with pairs defending small territories year-round. These pairs form the core social unit, as the species does not exhibit cooperative breeding or complex group hierarchies. Courtship involves the male performing short, fluttering display flights while singing, often while carrying a leaf or spiderweb as a nesting material offering. Both sexes participate in nest construction, building a deep, cup-shaped nest suspended in a fork of slender branches, typically low to the ground. The female lays two eggs, which are incubated by both parents for approximately 14-16 days. A unique reproductive strategy includes the frequent use of spiderweb to bind the nest structure, providing elasticity and durability against wind and rain. After hatching, both parents feed the nestlings, and the young fledge after about 10-12 days, though they remain dependent on the parents for several additional weeks before dispersing.

Alimentation

The Unicolored Antwren is an insectivorous bird, with its diet consisting almost exclusively of small arthropods. It forages actively in the understory and midstory of Atlantic Forest, gleaning prey from leaves, twigs, and mossy branches. A particularly interesting aspect of its feeding behavior is its strong association with mixed-species foraging flocks, where it often follows army ant swarms. While it does not eat the ants themselves, it capitalizes on the chaos caused by the ants, capturing various insects and spiders that flee from the advancing swarm. This strategy allows it to access a higher density of prey than it would find foraging alone.

Couleurs

The male Unicolored Antwren is a uniform, dark bluish-gray overall with a small, concealed white patch on its back, while the female is a warm, rich rufous-brown with a paler throat and belly. Both sexes lack bold streaks or wing bars, with subtle, slightly paler feather edges on the underparts. This plain coloration provides effective camouflage against the dappled light and bark of their humid forest understory habitat.

Distribution Map

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

Détails de l'attraction

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