Troglodytes sissonii 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Troglodytidae

Scientific Name: Troglodytes sissonii (Grayson, 1868)
Common Name(s):
English Socorro Wren
Thryomanes sissonii BirdLife International (2004)
Thryomanes sissonii Stotz et al. (1996)
Thryomanes sissonii Collar and Andrew (1988)
Thryomanes sissonii Collar et al. (1994)
Thryomanes sissonii BirdLife International (2000)
Thryomanes sissonii Sibley and Monroe (1990, 1993)
Thryomanes sissonii AOU checklist (1998 + supplements)
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Keitt, B., Martínez-Gómez, J. & Tershy, B.
Facilitator/Compiler(s): Capper, D., Harding, M., Isherwood, I., O'Brien, A., Sharpe, C J, Taylor, J. & Ashpole, J
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.

Previously published Red List assessments:

Geographic Range [top]

Range Description:This species 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).

Countries occurrence:
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:150
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):1050
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: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. The population may now be increasing in southern Socorro following sheep and cat eradication efforts (J.E. Martínez-Gómez in litt. 2016) however further evidence is required to confirm this increasing trend.
Current Population Trend:Unknown
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:This species inhabits woodland and brushy hillsides (del Hoyo et al. 2005). It is more common near forest patches, individual trees, dead trunks and occasionally bushes and is now observed near human settlements (J.E. Martínez-Gómez in litt. 2016). 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).

Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):3.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): The proliferation of sheep on the island since the 19th century led to deforestation of large parts of the southern lowlands, where the species is no longer common (J. Martínez-Gómez in litt. 1998). The effect of intensive grazing was a considerable threat to its already very small range. However now that sheep have been eradicated from Socorro (Ortíz-Alcaraz et al. 2016) surveys will be required to assess whether the population is able to recover and expand. Feral cats also pose a threat however eradication efforts are underway (J.E. Martínez-Gómez in litt. 2016). 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 [top]

Conservation Actions: Conservation Actions Underway
A programme to eradicate feral sheep from Socorro was conducted from 2009 to 2012 (Ortíz-Alcaraz et al. 2016). Cat eradication efforts are ongoing (J.E. Martínez-Gómez in litt. 2016). The species is included on the 'Watch List' of the State of North America's Birds as a species of high conservation concern (NABCI 2016).

Conservation Actions Proposed
Carry out surveys to assess the population size. Monitor population trends through regular surveys.

Citation: BirdLife International. 2016. Troglodytes sissonii. The IUCN Red List of Threatened Species 2016: e.T22711380A94291840. . Downloaded on 25 September 2017.
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