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Socorro Wren Troglodytes sissonii

Justification
This species is listed as Near Threatened because it has an extremely small range on one island, but it remains very common. Any evidence of a decline in the population would qualify it for a higher threat category.

Taxonomic source(s)
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

Taxonomic note
Formerly placed in the genus Thryomanes. Use of the genus Troglodytes follows Martínez Gómez et al. (2005).

Synonym(s)
Thryomanes sissonii BirdLife International (2000), Thryomanes sissonii Sibley and Monroe (1990, 1993), Thryomanes sissonii AOU checklist (1998 + supplements), Thryomanes sissonii Collar and Andrew (1988), Thryomanes sissonii Collar et al. (1994), Thryomanes sissonii BirdLife International (2004), Thryomanes sissonii Stotz et al. (1996)

Distribution and population
Troglodytes sissonii inhabits arid lowland scrub and semi-deciduous forest on Isla Socorro (c.150 km2) in the Revillagigedo Islands, Mexico (Howell and Webb 1995). It was described as the second most common landbird on the island in 1991 (Santaella and Sada 1991) and remains very common at all elevations (J. Martínez Gómez in litt. 1998).

Population justification
Partners in Flight estimated the population to number fewer than 50,000 individuals (A. Panjabi in litt. 2008), thus it is placed in the band 20,000-49,999 individuals here.

Trend justification
The population trend is difficult to determine because of uncertainty over the impacts of habitat modification on population sizes.

Ecology
This species inhabits woodland and brushy hillsides (del Hoyo et al. 2005). Its diet is unknown, but it has been observed foraging low in vegetation, on the ground, and on tree trunks. Families with fledged young have been observed in April, suggesting early breeding. One nest has been found in the knothole of a decayed tree (del Hoyo et al. 2005).

Threats
The proliferation of sheep on the island since the 19th century has led to deforestation of large parts of the southern lowlands, where the species is no longer common (J. Martínez Gómez in litt. 1998). Until sheep are eradicated from the island or effectively controlled, the continuing effect of intensive grazing may reduce its already very small range. There is no direct evidence that it is preyed upon by Socorro Mockingbird Mimodes graysoni (J. Martínez Gómez in litt. 1998 contra Parkes 1990).

Conservation Actions Underway
The eradication of sheep was planned for 2008-2009 (B. Tershy in litt. 2007). Conservation Actions Proposed
Carry out surveys to assess the population size. Monitor population trends through regular surveys. Eradicate sheep from Socorro.

References
del Hoyo, J.; Elliott, A.; Christie, D. 2005. Handbook of the Birds of the World, vol. 10: Cuckoo-shrikes to Thrushes. Lynx Edicions, Barcelona, Spain.

Howell, S. N. G.; Webb, S. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford.

Parkes, K. C. 1990. Was the Socorro Mockingbird (Mimodes graysoni) a predator on small birds? Wilson Bulletin 102: 317-320.

Santaella, L.; Sada, A. M. 1991. The avifauna of the Revillagigedo Islands, Mexico: additional data and observations. Wilson Bulletin 103: 668-675.

Further web sources of information
Explore HBW Alive for further information on this species

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

Text account compilers
Capper, D., Harding, M., Isherwood, I., O'Brien, A., Sharpe, C J, Taylor, J.

Contributors
Keitt, B., Martínez-Gómez, J., Tershy, B.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Troglodytes sissonii. Downloaded from http://www.birdlife.org on 16/09/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/09/2014.

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.

Additional resources for this species

ARKive species - Socorro wren (Troglodytes sissonii)

Key facts
Current IUCN Red List category Near Threatened
Family Troglodytidae (Wrens)
Species name author (Grayson, 1868)
Population size mature individuals
Population trend Unknown
Distribution size (breeding/resident) 140 km2
Country endemic? Yes
Links to further information
- Additional Information on this species