Troglodytes tanneri 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Troglodytidae

Scientific Name: Troglodytes tanneri
Species Authority: Townsend, 1890
Common Name(s):
English Clarion Wren, Clarión Wren
Identification information: 13 cm. Plain, grey-brown wren. Buff supercilium and eye-ring. Dark barring on tail and wings. Pale buff underparts, barred darker on undertail. Voice Long, dry insect-like rattle. Also chattering and tchek notes. Song similar to House Wren T. aedon.

Assessment Information [top]

Red List Category & Criteria: Vulnerable D1+2 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. & Tershy, B.
Facilitator/Compiler(s): Capper, D., Isherwood, I., Mahood, S., Pople, R., Sharpe, C J
This species qualifies as Vulnerable owing to its very small population and range, and hence its susceptibility to invasion by a mammalian predator.

Previously published Red List assessments:
2008 Vulnerable (VU)
2004 Vulnerable (VU)
2000 Vulnerable (VU)
1996 Vulnerable (VU)
1994 Vulnerable (VU)
1988 Threatened (T)

Geographic Range [top]

Range Description: Troglodytes tanneri is endemic to Isla Clarión in the Revillagigedo Islands, Mexico. Only 20 individuals were recorded in 1986 (Everett 1988), but subsequent visits to the island have found the species to be common (Howell and Webb 1989, Santaella and Sada 1991, Wanless et al. 2009). The population was estimated at 170-200 pairs in 1988, with the highest densities around buildings and adjacent areas (Howell and Webb 1989).

Countries occurrence:
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 33
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 1
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Upper elevation limit (metres): 335
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The population is estimated to number 340-400 individuals, roughly equating to 230-270 mature individuals.

Trend Justification:  There are no new data on population trends, and in the absence of information regarding introduced predators, the population is still suspected to be stable, although this warrants further investigation.
Current Population Trend: Stable
Additional data:
Number of mature individuals: 230-270 Continuing decline of mature individuals: Unknown
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 1 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: Yes
No. of individuals in largest subpopulation: 100

Habitat and Ecology [top]

Habitat and Ecology: It occurs in all habitats throughout the island from rocks on the beach to shrubbery at the highest elevations (Santaella and Sada 1991). Nests are built in bushes, cacti, buildings and derelict vehicles (Santaella and Sada 1991, Howell and Webb 1995a).

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): Introduced herbivores have extensively modified the native vegetation on Clarión (Stattersfield et al. 1998), but this has not had an impact upon this species. However, introduced rabbits Oryctolagus cuniculus may subsidise native predators, such as Burrowing Owl Athene cunicularia and racer snake Coluber sp. and increase their impact on wren populations. The introduction of a mammalian predator would have extremely serious consequences. The possibility of a cat introduction is small, but mouse or rat introductions are more likely (B. Tershy in litt. 1999), and there is no active introduction prevention plan in place (B. Tershy and B. Keitt in litt. 2007).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
The Revillagigedo Islands were declared a biosphere reserve in 1994 (Stattersfield et al. 1998). There is a plan to eradicate introduced herbivores from Clarión; pigs and sheep have already been eradicated but rabbits remain (B. Tershy in litt. 1999, Wanless et al. 2009). The Mexican navy restricts access to the island and helps to prevent further introductions (B. Tershy in litt. 1999, B. Tershy and B. Keitt in litt. 2007).

Conservation Actions Proposed
Carry out surveys to obtain an up-to-date population estimate. Monitor population trends through regular surveys. Eradicate introduced rabbits from Clarión. Continue to prevent the introduction of mammalian predators.

Citation: BirdLife International. 2012. Troglodytes tanneri. The IUCN Red List of Threatened Species 2012: e.T22711493A39653216. . Downloaded on 25 November 2015.
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