Data Zone
Justification of Red List category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Population justification
The population size has not been quantified, but the species is commonly observed across its range (eBird 2022). The population is suspected to exceed 10,000 mature individuals, but may potentially be substantially larger.
Trend justification
Although data on population trends are lacking, slow declines are suspected on the basis of ongoing habitat loss and degradation.
Within the range, 3% of tree cover is lost over ten years (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein). The species shows some tolerance of secondary and open forests (Zimmer and Isler 2020), and population declines are therefore likely equally low and localised; they are here tentatively placed in the band 1-9% over ten years.
Myrmotherula unicolor occurs along the lower slopes and coastal plains from Rio de Janeiro to northern Rio Grande do Sul, south-east Brazil.
It inhabits the under- and mid-storey of both undisturbed and second growth humid forest. It apparently prefers stunted forest with a canopy height of 8-10 m and an abundance of vines and suspended dead leaves in the undergrowth, but also occurs in coastal restinga woodlands (Whitney and Pacheco 1995, Zimmer and Isler 2020). Although it reaches higher elevations, most records are below 500 m (Whitney and Pacheco 1995). It frequently associates with mixed-species flocks (Whitney and Pacheco 1995, 1997).
The most severe threat to this species is the loss of its habitat (Silveira et al. 2022). Virtually all lowland Atlantic forest outside protected areas has been deforested within its historical range for human encroachment, logging and conversion for agricultural purposes. The lowlands and foothills of south Rio de Janeiro and São Paulo have become easily accessible to humans since the 1970s, with most of the lower forest cleared or heavily degraded (Whitney and Pacheco 1995).
Conservation Actions Underway
It occurs in several protected areas across its range, including Serra da Bocaina, Tijuca and Serra dos Órgãos national parks.
Conservation Actions Proposed
Conduct surveys of suitable habitats within and surrounding the known range to determine its true abundance. Monitor the population trend. Monitor rates of habitat loss. Gazette remaining tracts of primary forest for protection. Promote environmental awareness in communities near protected areas.
9.5 cm. Small, uniformly plain antwren. Male all grey, somewhat paler below, most with small, blackish throat patch. Female fulvous-brown above, olivaceous-buff below with whitish throat. Russet tail. Similar spp. All sympatric Myrmotherula have pale tips to coverts. Female Salvadori's Antwren M. minor has indistinct pale buff covert tips, but is less rufescent above with grey crown, brighter underparts and shorter tail. Voice Male song is short, high, plaintive eeeeeee. Raspy and strident plee-e contact calls.
Text account compilers
Hermes, C.
Contributors
Butchart, S., Gilroy, J., Lima, D.M., Phalan, B. & Subirá, R.
Recommended citation
BirdLife International (2024) Species factsheet: Unicolored Antwren Myrmotherula unicolor. Downloaded from
https://datazone.birdlife.org/species/factsheet/unicolored-antwren-myrmotherula-unicolor on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.