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Ashy Antwren Myrmotherula grisea
BirdLife is updating this factsheet for the 2016 Red List
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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.

Taxonomic source(s)
SACC. 2006. A classification of the bird species of South America. Available at: #

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.

Distribution and population
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).

Population justification
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.

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).

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 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.

Collar, N. J.; Gonzaga, L. P.; Krabbe, N.; Madroño Nieto, A.; Naranjo, L. G.; Parker, T. A.; Wege, D. C. 1992. Threatened birds of the Americas: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, Cambridge, U.K.

Herzog, K. S.; Hennessey, A. B.; Kessler, M.; Garcia-Soliz, V. 2008. Distribution, natural history and conservation status of two near-threatened endemics of the Bolivian Yungas, Bolivian Recurvebill Simoxenops striatus and Yungas Antwren Myrmotherula grisea. Bird Conservation International 18: 331-348.

Herzog, S.K., Hennessey, A.B., Kessler, M. and Garcia-Soliz, V.H. 2008. Distribution, natural history and conservation status of two endemics of the Bolivian Yungas, Bolivian recurvebill Simoxenops striatus and Yungas antwren Myrmotherula grisea. Bird Conservation International 18(4): 331-348.

IUCN. 2015. The IUCN Red List of Threatened Species. Version 2015-4. Available at: (Accessed: 19 November 2015).

Parker, T. A.; Bates, J.; Cox, G. 1992. Rediscovery of the Bolivian Recurvebill with notes on other little-known species of the Bolivian Andes. Wilson Bulletin 104: 173-177.

Perry, A.; Kessler, M.; Helme, N. 1997. Birds of the central río Tuichi valley, with emphasis on dry forest, Parque Nacional Madidi, Depto. La Paz, Bolivia. Ornithological Monographs 48: 557-576.

Robbins, M. B.; Geale; D.; Walker, B.; Davis, T. J.; Combe, M.; Eaton, M. D.; Kennedy, K. P. 2011. Foothill avifauna of the upper Urubamba Valley, dpto. Cusco, Peru. Cotinga 33: 41-52.

Wege, D. C.; Long, A. J. 1995. Key Areas for threatened birds in the Neotropics. BirdLife International, Cambridge, U.K.

Further web sources of information
Detailed species account from the Threatened birds of the Americas: the BirdLife International Red Data Book (BirdLife International 1992). Please note taxonomic treatment and IUCN Red List category may have changed since publication.

Detailed species account from the Threatened birds of the Americas: the BirdLife International Red Data Book (BirdLife International 1992). Please note, taxonomic treatment and IUCN Red List category may have changed since publication.

Explore HBW Alive for further information on this species

Recuento detallado de la especie tomado del libro Aves Amenazadas de las Americas, Libro Rojo de BirdLife International (BirdLife International 1992). Nota: la taxonomoía y la categoría de la Lista Roja de la UICN pudo haber cambiado desde esta publicación.

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Capper, D., Mahood, S., Pople, R., Sharpe, C J, Stuart, T. & Symes, A.

Fjeldså, J., Hennessey, A., Herzog, S., MacLeod, R. & Tobias, J.

IUCN Red List evaluators
Butchart, S.

Recommended citation
BirdLife International (2016) Species factsheet: Myrmotherula grisea. Downloaded from on 22/10/2016. Recommended citation for factsheets for more than one species: BirdLife International (2016) IUCN Red List for birds. Downloaded from on 22/10/2016.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Least Concern
Family Thamnophilidae (Antbirds)
Species name author Carriker, 1935
Population size mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 83,800 km2
Country endemic? No
Links to further information
- Additional Information on this species