<trp-post-container data-trp-post-id='360574'>Rough-legged Tyrannulet

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En bref

  • Scientific Name: Phyllomyias burmeisteri
  • Spanish Name: Tiranuelo patirrojo
  • Famille : Tyrannidae
  • Known Nicknames: Rough-legged Tyrannulet, Burmeister's Tyrannulet
  • Average Length: 11.5–13 cm / 4.5–5.1 in
  • Average Weight: 9–13 g / 0.32–0.46 oz
  • Envergure : N/A
  • Key Feature: Rough, scutellated tarsi (leg scales) and a pale yellow belly
  • Primary Diet: Primarily Insectivore (arthropods, small insects)
  • Range: Southeastern Brazil, eastern Paraguay, and extreme northeastern Argentina
  • Habitat: Montane and lowland Atlantic Forest, forest edges, and secondary growth
  • Social Structure: Solitary or in pairs; occasionally joins mixed-species flocks
  • Nesting/Breeding: Cup-shaped nest built in a tree fork or shrub
  • Statut de conservation : Préoccupation mineure (LC)
  • Évolution démographique : Stable

The Rough-legged Tyrannulet (*Phyllomyias burmeisteri*) is a small, unassuming yet fascinating flycatcher of South America’s montane forests, distinguished by a unique anatomical feature: its tarsi (lower legs) are rough, scale-like, and featherless, a rare adaptation thought to aid in gripping slippery, mossy branches in its humid, high-altitude habitat. About 11 cm long, it has a drab olive-green back, pale yellowish underparts, and a subtle whitish eyebrow, blending seamlessly into the canopy of cloud forests from Venezuela to Argentina. A special behavioral trait is its habit of hovering like a hummingbird to pluck insects from foliage, while its soft, trilling call often betrays its presence before it is seen.

Faits amusants

Despite its name, the Rough-legged Tyrannulet doesn’t actually have notably rough legs; the name likely refers to a subtle scaling on the tarsus. This small flycatcher has a peculiar habit of joining mixed-species foraging flocks, where it often acts as a sentinel, flicking its wings and tail in an agitated manner to alert other birds to predators. It also possesses a rare adaptation among tyrannulets: a slightly hooked bill tip, which helps it pry loose prey like caterpillars and spiders from tight crevices in bark. When singing, males perform a quirky, mechanical “buzz-and-rattle” call that sounds more like an insect than a bird, often delivered from a high, exposed perch.

Habitats et répartition

The Rough-legged Tyrannulet inhabits humid montane and subtropical forests, typically at elevations between 800 and 2,200 meters. It is most often found in the canopy and edges of primary and mature secondary forest, as well as in adjacent clearings with tall trees, but it avoids open or heavily degraded areas. Its geographical range is restricted to the eastern slope of the Andes, occurring from central Peru through Bolivia into northwestern Argentina, with a single isolated population in southeastern Brazil (the Serra do Mar and adjacent highlands).

Comportements & Reproduction

The Rough-legged Tyrannulet is typically observed alone or in pairs, suggesting a socially monogamous mating system during the breeding season. Courtship involves the male performing short, fluttering flights while vocalizing, often from exposed perches to attract a female. They are likely territorial, with the pair defending a nesting area. The nest is a small, cup-shaped structure made of plant fibers and moss, usually placed in a tree fork. Females lay two eggs, and both parents are believed to share incubation duties and feeding of the young. A unique strategy is their use of dense, thorny vegetation for nesting, which provides protection from predators in their montane forest habitat. No elaborate cooperative breeding or extra-pair copulations have been documented for this species.

Alimentation

The Rough-legged Tyrannulet is primarily an insectivore, with its diet consisting almost entirely of small arthropods gleaned from foliage and branches in the mid-story and canopy of humid montane forests. It actively forages by making short, fluttery flights to snatch prey from leaf surfaces or bark, rarely hovering for extended periods. An interesting fact is that, unlike many similar flycatchers, it shows a strong preference for caterpillars, often plucking them from the undersides of leaves, and it has been observed to occasionally consume small berries and fruits during the non-breeding season when insect prey becomes less abundant.

Couleurs

The Rough-legged Tyrannulet is primarily olive-green above with a pale yellowish belly and throat, featuring two distinct pale yellowish wing bars and a faint whitish supercilium. Its legs are uniquely feathered down to the toes, a rare adaptation among tyrant flycatchers. The face shows subtle dusky streaks, and the overall dull coloration provides effective camouflage in the dappled light of its montane forest understory.

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