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Cobb's Wren Troglodytes cobbi

Justification
Although this species is more widespread than previously believed, it is only found on predator-free islands, and its overall range is very small. It is classified as Vulnerable because it is highly susceptible to the impact of any potential invasion by rats. Further surveys and monitoring, combined with ongoing conservation efforts to secure its range, could result in a downlisting to Near Threatened.

Taxonomic source(s)
Campagna, L.; St Clair, J. J. H.; Lougheed, S. C.; Woods, R. W.; Imberti, S.; Tubaro, P. L. 2012. Biological Journal of the Linnean Society. Divergence between passerine populations from the Malvinas - Falkland Islands and their continental counterparts: a comparitive phylogeographical study DOI: 10.1111/j.1095-8312.2012.01898.x.
Woods, R. W. 1993. Cobb's Wren Troglodytes (aedon) cobbi of the Falkland Islands. Bulletin of the British Ornithologists' Club 113: 195-207.

Taxonomic note
Troglodytes aedon (Sibley and Monroe 1990, 1993) has been split into T. aedon and T. cobbi following Woods (1993) and Campagna et al. (2012), contra SACC (2005, 2009), pending consideration of the Campagna et al. (2012) paper by SACC. "

Identification
13.5 cm. Smallish, dark wren. Uniformly dark chestnut-brown upperparts. Greyer head. Pale greyish-buff underparts. Wings and tail barred dark brown and pale buff. Slender blackish bill. Voice Harsh chiz notes. Song is complex and variable, mixed phrase of trills and whistles with harsh notes.

Distribution and population
Troglodytes cobbi has a very scattered distribution in the Falkland Islands (Malvinas). Surveys in 1983/1984-1992/1993 indicated breeding on 12 offshore islands and islets, and estimated the total population at 1,300-2,400 pairs (Woods and Woods 1997). In later years, surveys indicated breeding on 35 islands (N. Huin in litt. 2007), and estimated the total population at 4,500-8,000 pairs (R. W. Woods in litt. 1999, Woods 2000). Currently it is estimated to breed on 70 islands, half of which are smaller than 50 ha (Woods and Otley 2008). Most of the islands are in small groups, separated by up to 64 km of sea, and there is no evidence to suggest an interchange between these island populations (Woods 1993, Woods and Woods 1997). However, it is likely that dispersing immatures are able to cross small bays (R. W. Woods in litt. 1999). In 1983, sample plots on Kidney and Carcass Islands produced population densities of four territorial males per hectare in optimum habitat and two males per hectare in less suitable conditions (R. W. Woods in litt. 1999).

Population justification
An estimate of 9,000-16,000 individuals is given by Woods (2000). In 2008 this estimate had remained unchanged at 9,000-16,000 individuals or 6,000 pairs (12,000 mature individuals).

Trend justification
No new data on population trends have been provided since Woods (2000). This species is assumed to be stable, owing to lack of current direct threats.

Ecology
Optimum habitat is dense tussock-grassland, growing from the high-water mark behind boulder beaches with accumulated dead kelp in which invertebrates thrive. The species is also found in rushes and among rock outcrops up to 1.6 km from coastal tussock on islands with no introduced predators. The nest is usually well-hidden in a gap amongst tussock stems or a tussock pedestal, or in a rock-crevice. Eggs are laid between early October and December, and there are probably two broods per season (Woods 1993, Woods and Woods 1997).

Threats
The species is threatened by the potential introduction of mammalian predators to its breeding islands, especially rats (probably brown rat Rattus norvegicus) because it feeds at ground-level in exactly the habitat used by foraging rats (R. W. Woods in litt. 1999). Its present distribution is inversely related to the presence of such predators, whose impact may have increased with the historic destruction of its habitat (Woods 1993, Woods and Woods 1997). Rats and probably feral cats have destroyed entire populations (Woods and Woods 1997). Grazing pressure and uncontrolled fires are also potential threats (G. Munro in litt. 2007).

Conservation Actions Underway
In 1998, Double and Outer Islands, off Spring Point, West Falkland, were acquired by Falklands Conservation (Woods 2000), and rat eradication started in 2000, covering these islands and two others, Top and Bottom Islands at Port William (R. Ingham in litt. 2000). In total, rats have now been eradicated from 22 islands (G. Munro in litt. 2007). Of the remaining islands within the range, 162 are known to have no introduced land predators, 75 have confirmed rats and/or mice present and a further 553 have not been surveyed (most of them are small or tiny islands) (N. Huin in litt. 2007). Conservation Actions Proposed
A conservation action plan has been produced (Woods and Otley 2008). Continue surveys to monitor population trends. Conduct ecological studies in order to understand the necessary conditions for the species's conservation (Woods and Woods 1997). Eradicate rats from selected small islands covered with mature tussock-grass to encourage recolonisation (Woods and Woods 1997, R. W. Woods in litt. 1999).

References
Woods, R. 2000. Update on Cobb's Wren. Warrah 17: 11.

Woods, R. W. 1993. Cobb's Wren Troglodytes (aedon) cobbi of the Falkland Islands. Bulletin of the British Ornithologists' Club 113: 195-207.

Woods, R. W.; Woods, A. 1997. Atlas of breeding birds of the Falkland Islands. Anthony Nelson, Oswestry, U.K.

Woods, R.; Otley, H. 2008. A Species Action Plan for Cobb's Wren 2009-2019.

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
Gilroy, J., Pilgrim, J., Pople, R., Sharpe, C J

Contributors
Ingham, R., Munro, G., Woods, R.W.

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

Recommended citation
BirdLife International (2014) Species factsheet: Troglodytes cobbi. Downloaded from http://www.birdlife.org on 22/10/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/10/2014.

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 - Cobb’s wren (Troglodytes cobbi) 0

Key facts
Current IUCN Red List category Vulnerable
Family Troglodytidae (Wrens)
Species name author Chubb, 1909
Population size 12000 mature individuals
Population trend Stable
Distribution size (breeding/resident) 270 km2
Country endemic? Yes
Links to further information
- Additional Information on this species