Troglodytes cobbi

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	PASSERIFORMES	TROGLODYTIDAE

Scientific Name:

Troglodytes cobbi

Species Authority:

Chubb, 1909

Common Name/s:

English

–

Cobb's Wren

Assessment Information [top]

Red List Category & Criteria:

Vulnerable D2 ver 3.1

Year Published:

2008

Assessor/s:

BirdLife International

Reviewer/s:

Gilroy, J., Butchart, S.

Contributor/s:

Ingham, R., Munro, G., Woods, R.

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.

History:

2006	–	Vulnerable
2004	–	Vulnerable
2000	–	Vulnerable
1996	–	Vulnerable
1994	–	Vulnerable
1988	–	Not Recognized

Geographic Range [top]

Range Description:	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 pairs⁴. Surveys have indicated breeding on 35 islands⁷, and estimated the total population at 4,500-8,000 pairs^3,5. 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^2,4. However, it is likely that dispersing immatures are able to cross small bays⁵. 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 conditions⁵.
Countries:	Native: Falkland Islands (Malvinas)
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	No new data on population size. Given estimate is taken from Woods (2000).
Population Trend:	Stable

Habitat and Ecology [top]

Habitat and 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^2,4.
Systems:	Terrestrial

Habitat and 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^2,4.

Systems:

Terrestrial

Threats [top]

Major Threat(s):	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 rats⁵. Its present distribution is inversely related to the presence of such predators, whose impact may have increased with the historic destruction of its habitat^2,4. Rats and probably feral cats have destroyed entire populations⁴. Grazing pressure and uncontrolled fires are also potential threats⁶.

Major Threat(s):

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 rats⁵. Its present distribution is inversely related to the presence of such predators, whose impact may have increased with the historic destruction of its habitat^2,4. Rats and probably feral cats have destroyed entire populations⁴. Grazing pressure and uncontrolled fires are also potential threats⁶.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway In 1998, Double and Outer Islands, off Spring Point, West Falkland, were acquired by Falklands Conservation³, and rat eradication started in 2000, covering these islands and two others, Top and Bottom Islands at Port William¹. In total, rats have now been eradicated from 22 islands⁶. 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)⁷. Conservation Actions Proposed Continue surveys to monitor population trends. Conduct ecological studies in order to understand the necessary conditions for the species's conservation⁴. Eradicate rats from selected small islands covered with mature tussock-grass to encourage recolonisation^4,5.

Conservation Actions:

Conservation Actions Underway
In 1998, Double and Outer Islands, off Spring Point, West Falkland, were acquired by Falklands Conservation³, and rat eradication started in 2000, covering these islands and two others, Top and Bottom Islands at Port William¹. In total, rats have now been eradicated from 22 islands⁶. 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)⁷.

Conservation Actions Proposed
Continue surveys to monitor population trends. Conduct ecological studies in order to understand the necessary conditions for the species's conservation⁴. Eradicate rats from selected small islands covered with mature tussock-grass to encourage recolonisation^4,5.

Citation:	BirdLife International 2008. Troglodytes cobbi. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 24 May 2012.
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