Myrmotherula grisea 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Thamnophilidae

Scientific Name: Myrmotherula grisea Carriker, 1935
Common Name(s):
English Ashy Antwren, Yungas Antwren
Taxonomic Source(s): SACC. 2005 and updates. A classification of the bird species of South America. Available at: #
Identification information: 10 cm. Small, arboreal, gleaning antwren showing strong sexual dimorphism. Male entirely uniform grey, with unmarked wing-coverts. Female olivaceous-brown above with more rufescent unmarked wings and tail and uniformly bright ochraceous underparts. Voice Series of eight loud but melancholic kíu or kee calls at same pitch and pace. Also harsh, chattery calls.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Fjeldså, J., Hennessey, A., Herzog, S., MacLeod, R. & Tobias, J.
Facilitator/Compiler(s): Capper, D., Mahood, S., Pople, R., Sharpe, C J, Stuart, T. & Symes, A.
This species's range and abundance have been recently studied, and it has been found to be more widely distributed and commoner than previously thought (Collar et al. 1992). It is no longer considered to have a small range and is found within  large areas of intact primary forest. Its presence has been confirmed at more than 10 locations, and it is suspected to be undergoing only slow rates of population decline. For these reasons, it has been downlisted to Least Concern, as it can no longer be considered to approach the thresholds for Vulnerable under any of the IUCN criteria.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Myrmotherula grisea is restricted to the Yungas (east Andean foothills) of La Paz, Beni, Cochabamba and Santa Cruz, central and west Bolivia, and has recently been found in extreme south-west Puno, Peru (Herzog et al. 2008). In 2007 and 2009, birds were captured in the upper Urubamba Valley, Cusco, Peru, some 500 km north-west of this (Robbins et al. 2011). It occurs more or less continuously in suitable habitat across its range, and a recent study on Cordillera Mosetenes, which appears to hold over half the total population, estimated a density of 15 individuals per km2 (Herzog et al. 2008).

Countries occurrence:
Bolivia, Plurinational States of; Peru
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:186000
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:24Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):600
Upper elevation limit (metres):1500
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Herzog et al. (2008) estimated the population to be 70,000-80,000 individuals.

Trend Justification:  This species is suspected to lose 12.6-13.7% of suitable habitat within its distribution over three generations (15 years) based on a model of Amazonian deforestation (Soares-Filho et al. 2006, Bird et al. 2011). Given the susceptibility of the species to fragmentation and/or edge effects, it is therefore suspected to decline by <25% over three generations.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:2-100Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No
No. of individuals in largest subpopulation:1-89

Habitat and Ecology [top]

Habitat and Ecology:It occurs in foothill forest with a dense, structurally complex understorey, often with Chusquea bamboo, at 600-1,500 m, but is apparently most numerous in a narrow elevational zone above the normal upper limits of its congeners White-flanked Antwren M. axillaris and Grey Antwren M. menetriesii (S. K. Herzog in litt. 1999, Herzog et al. 2008). It occurs in a variety of habitats, having been recorded in extremely wet evergreen forest (S. K. Herzog in litt. 1999), vine-tangles in the transitional zone between semi-deciduous or dry forest and riparian forest (Perry et al. 1997), and in relatively dry, semi-deciduous forest (S. K. Herzog in litt. 1999).

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):5.1
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): It is threatened by deforestation within its small geographic and elevational range, especially in La Paz and Cochabamba. Its preferred forest habitats are more accessible and easier to burn than true montane forest, with soils suited to the cultivation of staple food and export crops. Consequently, the region is a favoured target for colonists from the altiplano, and encroachment into protected areas is occurring. Exploration for natural resources takes place in Bolivia's national parks, making mining a potential future threat (B. Hennessey in litt. 1999). Nevertheless, vast amounts of pristine forest remain in inaccessible areas within the species's elevational range, although it may be excluded by the harsh climate in some of these areas (J. Fjeldså in litt. 1999, B. Hennessey in litt. 1999).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
A significant proportion of its range is protected in Amboró National Park (Santa Cruz), Carrasco National Park (Cochabamba), Isiboro Sécure National Park (Beni/La Paz), Pilón Lajas Biosphere Reserve and Indigenous Territory and Madidi National Park (La Paz) (Wege and Long 1995, Perry et al. 1997, S. K. Herzog in litt. 1999).

Conservation Actions Proposed
Survey remaining forests in upper tropical zone in Bolivia. Maintain the integrity of Amboró and Carrasco National Parks to ensure their integrity, particularly with respect to encroachment by settlers.

Citation: BirdLife International. 2016. Myrmotherula grisea. The IUCN Red List of Threatened Species 2016: e.T22701520A93833965. . Downloaded on 26 May 2018.
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