Cobb’s wren (Troglodytes cobbi)

Description

What’s the World’s Favourite Species?

Cobb’s wren fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Cobb’s wren description

Cobb’s wren (Troglodytes cobbi) is a small, charismatic bird ⁽⁴⁾, found only on the Falkland Islands archipelago. A somewhat dull coloured bird, Cobb’s wren has uniformly dark chestnut-brown upperparts, pale grey under-parts and a grey-brown head. The wings and tail are barred dark brown and chestnut. The distinctively long and slightly down-curved bill is black and the eyes and legs are brown. It is often seen moving from boulder to boulder like a mouse, and will disappear from disturbances in this way, in preference to flying ⁽⁵⁾.

Also known as

house wren, rock wren (in the Falkland Islands).

Synonyms

Troglodytes aedon cobbi.

Size

Length: 12 cm ⁽²⁾

Weight

17 – 20 g ⁽³⁾

Cobb’s wren biology

Breeding between October and December, Cobb’s wren lays three or four eggs per clutch in a dome-shaped nest built by the male of grasses, with an entrance hole near the top ^{(1) (3) (4) (8) (9)}. The nest is lined with the soft feathers of several bird species, and is well hidden in tussac grass or in a rock crevice ^{(3) (4)}, between ground level and 60 centimetres above the ground ⁽⁵⁾. It is possible that a breeding pair will produce two clutches a year. Cobb’s wren is tame and disregards human presence if it does not feel threatened, often feeding near them ⁽²⁾.

Cobb’s wren feeds on invertebrates found within dead kelp on beaches, within tussac grass, and under or around boulders ^{(2) (8)}. Although often difficult to see, Cobb’s wren will reveal its presence through song, a mixed phrase of rapid trills, whistles and harsh notes, used to defend territories and attract mates during the breeding season ^{(9) (10)}. Males on Carcass Island have been shown to live for at least six years, and probably stay in the same territory for life ^{(4) (10)}.

Cobb’s wren range

Cobb’s wren is found on about 100 offshore ^{(6) (7)}, predator-free islands in the Falkland Islands archipelago, including Sea Lion, Carcass, Speedwell, Lively and most of the Jason Islands group ^{(4) (5) (8)}.

Cobb’s wren habitat

Found most commonly around the tussac grassland behind kelp-strewn, boulder beaches. Cobb’s wren is also found in rushes and amongst rock outcrops, up to one and a half kilometres from the coast ^{(1) (5) (8)}.

Cobb’s wren status

Cobb's wren is classified as Vulnerable (VU) on the IUCN Red List ⁽¹⁾.

Cobb’s wren threats

With a distribution already limited to the 750 plus archipelago of the Falkland Islands, Cobb’s wren has apparently become locally extinct on many of the offshore islands and the two main islands, East and West Falkland. Those islands with suitable Cobb’s wren habitat, such as tussac, other vegetation and boulder beaches with kelp, but with populations of introduced mammals, such as brown rat (Rattus norvegicus) and feral cats, have been found to lack any Cobb’s wren populations. There is currently no concrete evidence that such mammals predate Cobb’s wren, but there is a mass of circumstantial evidence showing that when these mammals establish on islands with Cobb’s wren, it is lost from the islands within a few years. Rats hunt along the shoreline where Cobb’s wren prefers to forage, so it is therefore reasonable to assume that rats come into conflict with Cobb’s wren. Cobb’s wren is also threatened by the loss of its habitat, through livestock grazing and fires ^{(1) (4) (8)}.

Cobb’s wren conservation

Rat eradication programs started on the islands in 2001 ⁽⁶⁾. So far, eradications to remove rats have been attempted on 56 islands, with 20 of these confirmed as successful to date ⁽⁷⁾. There are established rat populations on at least a further 41 islands and probably many more ⁽⁸⁾.

Proposed conservation plans for Cobb’s wren include continued surveys to obtain some population numbers, with further studies to help understand the ideal conditions for conservation. Further rat eradication is planned on islands carrying tussac grass to encourage re-colonisation ⁽¹⁾ and it is probable that through the eradication of invasive predators and knowledge gained from surveys, Cobb’s wren could be reclassified as Near Threatened ⁽¹⁾.

Bio-security plans and management plans are being put in place to reduce the chances of accidental introduction of further invasive species to islands with Cobb’s wren populations ⁽⁴⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For more information on conservation in the Falkland Islands, see:

• FalklandsConservation:
  http://www.falklandsconservation.com/

For more information on the conservation of birds, see:

• The Royal Society for the Protection of Birds:
  http://www.rspb.org.uk/

For more information on Cobb's wren and other bird species please see:

• BirdLife International:
  http://www.birdlife.org

Authentication

Authenticated (27/10/10) by Robin W Woods, MBE FLS, ornithologist and botanist, resident in Devonshire UK, and Nick Rendell, Environmental Officer, Falkland Islands Government.
http://www.epd.gov.fk

Glossary

Feral

Previously domesticated animals that have returned to a wild state.

Invertebrates

Animals with no backbone, such as insects.

Territory

An area occupied and defended by an animal, a pair of animals or a colony.

References

1. IUCN Red List (September, 2010)
   http://www.iucnredlist.org/
2. Ridgely, R.S. and Tudor, G. (2009) Field Guide to the Songbirds of South America: The Passerines. University of Texas Press, Texas.
3. Natural History Museum - Cobb's wren (September, 2010)
   http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/endangered-species/troglodytes-cobbi/index.html
4. Woods, R. and Otley, H. (2008) A Species Action Plan for Cobb’s Wren: 2009 – 2019. Falklands Conservation, Falkland Islands. Available at:
   http://www.falklandsconservation.com/news/2009/Cobbs_Wren_SAP_FINAL.pdf
5. Falklands Conservation - Cobb's wren (September, 2010)
   http://www.falklandsconservation.com/wildlife/birds/cobbswren.html
6. Woods, R. (October, 2010) Pers. comm.
7. Poncet, S. (October, 2010) Pers. comm.
8. BirdLife International - Cobb's wren (September, 2010)
   http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=9769&m=0
9. Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford, UK.
10. Woods, R.W. and Woods, A. (2006) Birds and Mammals of the Falkland Islands. Wildguides, Hampshire, UK.