Gough bunting  (Rowettia goughensis)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

The Gough bunting is a large, stocky, olive-coloured bunting, endemic to Gough Island in the South Atlantic Ocean. The more or less uniformly olive-green colouration of the male, which is slightly paler on its underparts, is disrupted only by the yellowish plumage of the forehead and eyebrow, and the prominent black ‘bib’ just below the thick-based, pointed black bill. Females lack the black bib and juveniles, by contrast, possess a buff-olive plumage, heavily streaked above and below with dark brown. The contact call consists of a keet keet sound and the song of a high, keening whistle (2).

Endemic to Gough Island of the Tristan da Cunha group (St Helena, UK) in the South Atlantic Ocean. The population was estimated at approximately 200 pairs in 1974 and 1,500 pairs in 1991, but recent surveys of breeding territories in 2007 suggest a population of just 400 – 500 pairs (2).

Most common in tussock-grassland, wet heath and among scrub up to 800 m, occuring at lower densities in fern-bush and peat-bogs (2) (3).

To date, few observations of the breeding behaviour of this species have been made (4). Nests are built on the ground amongst or under vegetation, but mostly on steep slopes or cliffs (2), and clutches usually consisting of two eggs appear to be laid around September and October (4). Adult plumage is not reached for at least three years, but sexual maturity and activity may not necessarily correlate (2).

The diet consists primarily of invertebrates (80% of foraging time), but also of fruit, grass seeds, and scavenged birds and broken eggs (2).

This bird’s occurrence in a restricted habitat of one very small island makes it extremely vulnerable to natural disasters like fires and hurricanes, or to introduced diseases, and especially to the accidental introduction of non-native predators (3). Indeed, the introduced house mouse Mus musculus poses the greatest present threat through competition and predation (2). Buntings are found at low density in lowland areas where mice are abundant (2), and experiments with ‘dummy’ eggs imply that mouse predation on their nests is very high (5). Thus, researchers think the bird may have been forced by these mice from the best nesting sites into less suitable upland regions (5). Over the last 15 years, the proportion of juveniles in the population has declined from 50% to 20%, this appears to indicate that there are now too few young surviving to reproductive age to sustain the population.

The accidental introduction of the black rat Rattus rattus from Tristan is also a huge potential threat, having caused devastation on Tristan to a number of bird species. Worryingly, a dead rat was discovered in a packing case in 1967, another was found on the Gough supply ship in 1974, and there was an unconfirmed rat sighting on the island in 1983 (2).

Gough Island is both a Nature Reserve and World Heritage Site, and while this provides good protection from human disturbance, it does not offer the Gough bunting any protection from the mouse predation that is driving it towards extinction (2). A study of the mice conducted by The Royal Society for the Protection of Birds (RSPB) and funded by the UK government's Overseas Territories Environment Programme has shown that their eradication from the island is feasible. Unfortunately, however, until adequate funding from the UK government is supplied this will not occur (6). Gough Island is widely recognised as having one of the most diverse bird colonies in the world, including four endangered species, and every effort should therefore be made to protect it and the rich biodiversity it hosts (7).

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

To learn more about the Gough bunting and its threats visit:

• BirdLife International:
  http://www.birdlife.org/news/news/2008/12/gough_island.html
• The Royal Society for the Protection of Birds (RSPB):
  http://www.rspb.org.uk