Rowettia goughensis

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	PASSERIFORMES	EMBERIZIDAE

Scientific Name:

Rowettia goughensis

Species Authority:

(Clarke, 1904)

Common Name/s:

English

–

Gough Bunting, Gough Finch

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered B1ab(iii,v) ver 3.1

Year Assessed:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Calvert, R., Symes, A., Butchart, S.

Contributor/s:

Cooper, J., Ryan, P.

Justification:
This 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 very rapidly. Urgent conservation intervention, which would also benefit the island's breeding seabirds, is needed to reverse this decline.

History:

2009	–	Critically Endangered
2008	–	Critically Endangered
2004	–	Vulnerable
2000	–	Vulnerable
1996	–	Vulnerable
1994	–	Vulnerable

Geographic Range [top]

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 present⁶. Modern population estimates have varied and may not accurately reflect population trends; there were thought to be c.200 pairs in 1972-1974² (substantially lower than previous estimates), 1,500 pairs in 1991³, 400-500 pairs in 2000-1⁴ and similar numbers in 2007⁶. Monitoring indicated that the density of territorial pairs roughly halved between 1990 and 2007⁶,
Countries:	Native: Saint Helena
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	The population was estimated at c.1000 individuals in 2007 (Ryan and Cuthbert 2008).
Population Trend:	Decreasing

Habitat and Ecology [top]

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 peatbogs³. 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 chicks⁶. It feeds primarily on invertebrates (80% of foraging time), but also eats fruit³, grass seeds, and scavenges broken eggs and birds². It nests on the ground amongst or under vegetation, but mostly on steep slopes or cliffs, and usually lays two eggs, rarely one³. Different plumage types suggest that it takes at least three years to acquire full adult plumage³.
Systems:	Terrestrial

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 peatbogs³. 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 chicks⁶. It feeds primarily on invertebrates (80% of foraging time), but also eats fruit³, grass seeds, and scavenges broken eggs and birds². It nests on the ground amongst or under vegetation, but mostly on steep slopes or cliffs, and usually lays two eggs, rarely one³. Different plumage types suggest that it takes at least three years to acquire full adult plumage³.

Systems:

Terrestrial

Threats [top]

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 islands³. Recent research from Gough Island has shown that mice are a significant predator of breeding seabirds⁶, 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 areas⁵. 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 population⁶. 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 1983³.

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 islands³. Recent research from Gough Island has shown that mice are a significant predator of breeding seabirds⁶, 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 areas⁵. 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 population⁶. 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 1983³.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway Gough is a nature reserve and World Heritage Site and is uninhabited apart from staff who run a meteorological station¹. Territory mapping to investigate pair density in different habitats was conducted in 2000-2001, in addition to an assessment of the potential role of mice as nest predators^4,5. Further investigation of diet overlap with mice, and predation by mice has been undertaken during 2003-2006. Initial results from a feasibility study into the removal of the mice appear promising⁷. Conservation Actions Proposed Carry out regular surveys to monitor the population. Eradicate mice from Gough Island³. Minimise the risk of other alien species becoming established on the island, particularly any rat Rattus species³.

Conservation Actions:

Conservation Actions Underway
Gough is a nature reserve and World Heritage Site and is uninhabited apart from staff who run a meteorological station¹. Territory mapping to investigate pair density in different habitats was conducted in 2000-2001, in addition to an assessment of the potential role of mice as nest predators^4,5. Further investigation of diet overlap with mice, and predation by mice has been undertaken during 2003-2006. Initial results from a feasibility study into the removal of the mice appear promising⁷.

Conservation Actions Proposed
Carry out regular surveys to monitor the population. Eradicate mice from Gough Island³. Minimise the risk of other alien species becoming established on the island, particularly any rat Rattus species³.

Citation:	BirdLife International 2010. Rowettia goughensis. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 08 February 2012.
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