Troglodytes cobbi

Cobb’s wren is found only in the Falkland Islands.

Troglodytes_cobbiOn 28 July 1908 on Carcass Island Arthur Cobb shot a wren using rice as the charge. The specimen was skinned and sent to the Natural History Museum in London, where it was studied and described as a new species, Cobb’s Wren Troglodytes cobbi. Though considered later by some ornithologists to be a form of the continental House Wren, it was confirmed (1993) as one of the two endemic Falkland bird species, with the Falkland Flightless Steamer Duck. 

This bird is restricted to outer islands that have remained free of introduced predators (cats, rats and mice). It has Vulnerable conservation status (BirdLife International) primarily because of the destruction of its tussac grass habitat, introduction of predators and the small geographic range of its scattered population (estimated at about 6,000 pairs on 29 islands in 2001).

The ideal habitat for this bird appears to be dense tussac grass growing from high water mark behind a boulder beach with accumulated dead kelp (seaweed) in which invertebrates thrive.

A Species Action Plan (384kb PDF) has been produced by Falklands Conservation and the Falkland Islands Government to protect this endemic bird.

 Arthur Cobb after whom this small bird is named.

Description

This is a small bird up to 13 cm long. It has a dark chestnut back, with a grey-brown head and is buff-white below. The wings and tail are closely barred dark brown and chestnut. The bill is blackish and slightly curved. Adults fade to dull brown above during the summer when newly fledged juveniles have a dark head and bright chestnut back.

Behaviour

Cobb’s wren is very tame. It will feed close to people on a beach, and slip between or under boulders like a mouse. In tussac grass it also vanishes silently when disturbed in preference to flying away.

The call notes are a harsh, buzzing chiz or cheez, which become loud and explosive when the bird is excited. Song is a mixed phrase of rapid trills, whistles and harsh notes lasting about two seconds. It sings mostly from late August to November and less frequently through to April. Males can live at least six years and probably remain faithful to their breeding territories throughout the year.

Cobb’s wren on a boulder beach, Carcass Island.

Food


Camel Cricket

Cobb’s wrens feed on small invertebrates, including insects and sea lice on beaches. They also take camel crickets and will feed their nestlings on moth larvae.

Breeding

The birds breed between October and December, laying 3-4 pinkish eggs spotted with red and are probably double brooded. The nest is a domed ball of grasses with a deep cup lined with soft feathers, built in a cavity in a tussac pedestal or below rocks.

Predators

Cobb’s wren searching for food amongst the kelp.

It is probable that rats, mice and feral cats have destroyed whole populations of Cobb’s wren. This bird is incapable of surviving where these predators have been introduced in the Falklands. It has also suffered from long-term destruction of tussac grass habitat.

The above information has been obtained from publications by Robin Woods, with his kind permission.