|Scientific Name:||Rowettia goughensis|
|Species Authority:||(Clarke, 1904)|
Nesospiza goughensis Dowsett and Forbes-Watson (1993)
|Red List Category & Criteria:||Critically Endangered B1ab(ii,iii,v) ver 3.1|
|Reviewer(s):||Taylor, J. & Butchart, S.|
|Contributor(s):||Cooper, J. & Ryan, P.G.|
|Facilitator/Compiler(s):||Benstead, P., Calvert, R., Ekstrom, J., Mahood, S., McClellan, R., Shutes, S., Stattersfield, A., Symes, A., Taylor, J.|
This species is listed as Critically Endangered owing to an ongoing range contraction caused by excessive predation by introduced mice. Mouse predation has forced this species out of coastal areas into sub-optimal upland habitat and is causing the population to decline. Urgent conservation intervention, which would also benefit the island's breeding seabirds, is needed to reverse this decline.
|Range Description:||Rowettia goughensis is endemic to Gough Island, Tristan da Cunha (St Helena to UK) in the South Atlantic Ocean. Evidence suggests that it was much more common in the 1920s than at present (Ryan and Cuthbert 2008). Modern population estimates have varied and may not accurately reflect population trends; there were thought to be c.200 pairs in 1972-1974 (Richardson 1984) (substantially lower than previous estimates), 1,500 pairs in 1991 (P. G. Ryan in litt. 1999), 400-500 pairs in 2000-1 (Cuthbert and Sommer 2004) and similar numbers in 2007 (Ryan and Cuthbert 2008). Monitoring indicated that the density of territorial pairs roughly halved between 1990 and 2007 (Ryan and Cuthbert 2008),|
Native:Saint Helena, Ascension and Tristan da Cunha
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population was estimated at c.1000 individuals in 2007, roughly equivalent to 670 mature individuals.|
|Habitat and Ecology:||It is most common in tussock-grassland, wet heath and fjeldmark up to 800 m, and occurs at lower densities in fern-bush and peatbogs (Ryan and Cuthbert 2008). Breeding occurs from September to December, and chicks fledge in November and December. Clutch size is usually two eggs. The female constructs the nest, which is an open cup constructed on or close to the ground, sheltered by overhanging vegetation or a rock. Both sexes are involved in raising chicks (Ryan and Cuthbert 2008). It feeds primarily on invertebrates (80% of foraging time), but also eats fruit (Ryan and Cuthbert 2008), grass seeds, and scavenges broken eggs and birds (Richardson 1984). It nests on the ground amongst or under vegetation, but mostly on steep slopes or cliffs, and usually lays two eggs, rarely one (P. G. Ryan in litt. 1999). Different plumage types suggest that it takes at least three years to acquire full adult plumage (Ryan and Cuthbert 2008).|
|Major Threat(s):||The introduced house mouse Mus musculus poses the greatest threat through competition and predation. Mice are known to have substantially altered invertebrate populations on other sub-Antarctic islands and R. goughensis is much less abundant on Gough than other bunting species on nearby mouse-free islands (Ryan and Cuthbert 2008). Recent research from Gough Island has shown that mice are a significant predator of breeding seabirds (Ryan and Cuthbert 2008), thus the probability is that bunting nests are depredated. Buntings are found at low density in the lowlands where mice are abundant on Gough Island, and predation rates of dummy eggs are up to thirty times higher in these areas (Cuthbert and Hilton 2004). The proportion of juveniles in the population has declined from 50% to 20% over the last 15 years, suggesting that recruitment is too low to sustain the population (Ryan and Cuthbert 2008). The accidental introduction of the black rat Rattus rattus from Tristan is a potential threat - 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 (Wace 1986).|
Conservation Actions Underway
Gough is a nature reserve and World Heritage Site and is uninhabited apart from staff who run a meteorological station (Cooper and Ryan 1994). Territory mapping to investigate pair density in different habitats was conducted in 2000-2001, in addition to an assessment of the role of mice as nest predators (Cuthbert and Sommer 2004, Cuthbert and Hilton 2004). Further investigation of diet overlap with mice, and predation by mice was undertaken during 2003-2006. Following a 2006 review of the impacts of introduced rodents on Tristan da Cunha and Gough a feasibility study was published in 2008. The study recommended what research still needed to be undertaken before an eradication effort should be attempted, and since 2008 researchers on the island have been conducting this work. Activities have included investigating whether mice living in caves and lava tunnels would be exposed to poison bait dropped by helicopter (the answer seems to be yes), and how best to protect sufficient numbers of the two endemic land birds (including Gough Bunting) from the risks of both primary and secondary non-target poisoning. A draft operational plan for eradicating mice from Gough was prepared in 2010, setting out in detail a work plan and a timeframe for the eradication, using experience gained from other eradication projects such as the ongoing work on Macquarie Island (Torr et al. 2010).
Conservation Actions Proposed
Carry out regular surveys to monitor the population. Eradicate mice from Gough Island (Ryan and Cuthbert 2008). Minimise the risk of other alien species becoming established on the island, particularly any rat Rattus species (P. G. Ryan in litt. 1999).
|Citation:||BirdLife International 2012. Rowettia goughensis. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 31 July 2015.|
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