Troglodytes sissonii 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Troglodytidae

Scientific Name: Troglodytes sissonii
Species Authority: (Grayson, 1868)
Common Name(s):
English Socorro Wren
Thryomanes sissonii Stotz et al. (1996)
Thryomanes sissonii BirdLife International (2004)
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 Notes: Formerly placed in the genus Thryomanes. Use of the genus Troglodytes follows Martínez Gómez et al. (2005).

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
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.
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:
2008 Near Threatened (NT)
2004 Near Threatened (NT)
2000 Lower Risk/near threatened (LR/nt)
1994 Lower Risk/near threatened (LR/nt)
1988 Threatened (T)

Geographic Range [top]

Range Description: 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).

Countries occurrence:
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 140
Continuing decline in extent of occurrence (EOO): Unknown
Extreme 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.
Current Population Trend: Unknown
Additional data:
Continuing decline of mature individuals: Unknown
Extreme fluctuations: No Population severely fragmented: No
Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All 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). 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).

Systems: Terrestrial
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 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 [top]

Conservation Actions: 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.

Citation: BirdLife International. 2012. Troglodytes sissonii. The IUCN Red List of Threatened Species 2012: e.T22711380A39652807. . Downloaded on 01 December 2015.
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