Overview

Brief Summary

Introduction

Troglodytes cobbi (Cobb’s wren) is a wren found only in the Falkland islands. Troglodytes cobbi is named Cobb’s wren after Arthur F. Cobb who collected the first specimen from which the species was described on Carcass Island, Falkland Islands, in July 1908.Classified as ‘Vulnerable’ to extinction by the IUCN due to
  • the very small overall range (270km²) of the wrens habitat
  • living on islands with a high susceptibility to invasion by rats


Threats
Under threat predominantly from the potential
  • introduction of mammalian predators to islands where it breeds
  • the loss of its natural tussac habitat by burning and livestock grazing
  • cannot survive on islands in the presence of rats
    • may co-exist with a few domestic cats on larger islands
    • feral cats and rats have probably already destroyed whole populations
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 1 person

Average rating: 3.0 of 5

Taxonomy

Cobb’s wren forms a superspecies with:

Morphology
  • Crown and nape grey-brown, becoming browner on the back and shoulders and brighter rusty-brown on the rump.
  • Primaries and secondaries blackish-grey on inner webs, the outer webs with warm brown transverse bars, forming alternating ‘black and brown’ bars visible on the closed wing.
  • Rectrices warm brown, with narrow blackish bars across the entire tail.
  • Lores, cheeks and ear-coverts unmarked grey-brown; chin and throat lighter grey-brown.
  • Chest and belly unmarked grey-brown; flanks and undertail coverts rusty-brown.
  • Iris brown; bill blackish; legs dark brown.


Diagnostic description
A dark wren with uniformly dark chestnut-brown upperparts, pale greyish-buff underparts and greyish head. Wings and tail barred blackish and pale buff. Slender backish bill.Similar in appearance to Northern and Southern house wrens (Troglogytes aedon and T. musculus), though distinguished by its larger size, generally greyer plumage and very different ecology.

Look alikes
The only other wren present on the Falkland Islands is the Sedge Wren (Cistothorus platensis), which is smaller, shorter-billed, paler, and with obvious black and buff striations on the shoulders
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Comprehensive Description

Biology

Size
  • Length: 12 – 13 cm long (bill tip to tail tip)
  • Weight: 19.1g (mean), 17g - 20g (min-max)


Reproduction
  • Song heard between late August and mid-April.
  • Strongly territorial during breeding and faithful to territory from year to year.
  • The nest is a domed ball made of grasses with an entrance hole 6cm to 8cm wide near the top. It is lined with soft feathers of several species and is usually well hidden in tussac stems, a tussac pedestal or in a rock crevice between ground level and 60 cm above ground.
  • Three to four pinkish eggs, covered with tiny red or light brown spots, are laid between early October and December. Two broods are probably reared in a season.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Distribution

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 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).

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range

Falkland Islands.

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Ecology

Habitat

Habitat and Ecology

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 (Woods 1993, Woods and Woods 1997).


Systems
  • Terrestrial
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

General Ecology

Distribution ecology

Distribution
Endemic to the Falkland Island archipelago were it is only found on small offshore, predator-free islands.

Habitat
Associated with tussac grass (Parodiochloa flabellata), a very tall and dense Falkland plant.Optimum habitat is dense tussac-grassland growing from the high-water mark behind boulder beaches with accumulated dead kelp in which invertebrates thrive.It also occurs in rushes and among rock outcrops up to 1 mile from coastal tussac.

Population biology
Surveys in 1998/1999 estimated the total population at 4,500 – 8,000 pairs.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Behavior

Behaviour

Generally tame and confiding.Feeds in tussock grass and among boulders, moving mouse-like between crevices.When disturbed will disappear silently under cover in preference to flying.

Migration
Sedentary.No evidence of movement other than possibly between closely adjacent islands.

Feeding
Feeds on invertebrates for which it forages in tussac grass, around and under boulders and among washed-up kelp on beaches.Food items include:
  • Small insects
  • Lice
  • Crickets
  • Moth larvae
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Molecular Biology and Genetics

Molecular Biology

Barcode data: Troglodytes cobbi

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Statistics of barcoding coverage: Troglodytes cobbi

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Specimens with Barcodes: 8
Species With Barcodes: 1
Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
D2

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Symes, A. & Butchart, S.

Contributor/s
Ingham, R., Munro, G. & Woods, R.W.

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.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Conservation status
Classified as ‘Vulnerable’ due to its very small overall range (270km²) and the high susceptibility of islands on which it occurs to invasion by rats.

Threats
Under threat predominantly from the potential introduction of mammalian predators to islands where it breeds. Also threatened by the loss of its natural tussac habitat by burning and livestock grazing.It cannot survive on islands in the presence of rats, but may co-exist with a few domestic cats on larger islands. However, feral cats and rats have probably already destroyed whole populations.

Trends
Population currently thought to be stable.

Management
Rat eradication on suitable islands is the most important conservation strategy.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Natural History Museum, London

Partner Web Site: Natural History Museum

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population

Population
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).

Population Trend
Stable
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Threats

Major 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).

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management

Conservation Actions

Conservation Actions
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).

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Wikipedia

Cobb's wren

Cobb's wren (Troglodytes cobbi) is a fairly small (12-13.5 cm) wren which is endemic to the Falkland Islands. It was formerly classified as a subspecies of the house wren (Troglodytes aedon) but is now commonly considered to be a separate species due to differences in plumage, voice, ecology and morphology.

The common name commemorates Arthur Cobb, an author from the Falkland Islands.[2]

Description[edit]

The plumage is brown, greyer on the head and breast and more rufous on the tail. There are dark bars on the flight feathers and tail. The bill is long, blackish and slightly curved. The main confusion species is the sedge wren which is smaller with a shorter bill, buff eyestripe and dark streaks on the back and head. Cobb's wrens have a number of buzzing calls and their song is a series of jumbled trills and whistles. The song can be heard from August to February and varies between individuals with different males having different song patterns.

Behaviour[edit]

The birds typically inhabit dense stands of tussac grass near the coast. They are often found on beaches searching among kelp and debris to find small invertebrates such as insects and amphipods. They are tame and can often be approached closely. When disturbed they prefer to slip away like a mouse between boulders or tussac clumps rather than fly.

Breeding[edit]

The nest is a ball of grass lined with feathers and tussac root fibres. It is built on or near the ground among tussac or in a rock crevice. The eggs are pinkish with small reddish spots, three or four are laid in a clutch. The eggs are laid from early October to December and two broods are probably raised during the breeding season.

Status and conservation[edit]

This wren is restricted to small rat-free islands with a population of only 4,500-8000 pairs (1997/1998 estimate). The species is considered to be vulnerable to extinction as it is fragmented into small populations which could disappear if their islands were colonized by rats or cats. The birds' habit of feeding and breeding at ground level makes them very vulnerable to predation unlike the sedge wren which lives higher up and can coexist with predators.

The plight of the Cobb's wren was recently brought to broader attention by being featured as Canon's endangered species of the month for the February 2009 issue of National Geographic Magazine.

References[edit]

  1. ^ BirdLife International (2012). "Troglodytes cobbi". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Beolens, Bo; Watkins, Michael (2003). Whose Bird? Men and Women Commemorated in the Common Names of Birds. London: Christopher Helm. p. 85. 
Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

Source: Wikipedia

Unreviewed

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!