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Gallinula nesiotis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES GRUIFORMES RALLIDAE

Scientific Name: Gallinula nesiotis
Species Authority: P. Sclater, 1861
Common Name/s:
English Gough Moorhen, Tristan Moorhen
Taxonomic Notes: Gallinula nesiotis and G. comeri (Collar and Stuart 1985) have been lumped as G. nesiotis following Sibley and Monroe (1990, 1993) and supported by Groenenburg et al. (2008) and Groenenburg et al. (2009).

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor/s: BirdLife International
Reviewer/s: Butchart, S. & Taylor, J.
Contributor/s: Hilton, G. & Ryan, P.
Facilitator/s: Ekstrom, J., Khwaja, N., McClellan, R., Pilgrim, J., Shutes, S., Stattersfield, A., Taylor, J. & Symes, A.
Justification:
This species is listed as Vulnerable because it is restricted to a very small range on just two small islands and, although it coexists with introduced rats on the island of Tristan da Cunha, the accidental introduction of rats, or another predator, to its stronghold on Gough Island remains a risk.

Geographic Range [top]

Range Description: Gallinula nesiotis is found on Gough Island and Tristan da Cunha (St Helena to UK) in the South Atlantic Ocean. The nominate subspecies, endemic to Tristan, was driven extinct in the late-19th century (Nicoll 1906). In 1956, seven birds from the Gough population were reintroduced to Tristan, and this population remains on the island. In 1983, the Gough population was estimated at 2,000-3,000 pairs in 10-12 km2 of suitable habitat (Watkins and Furness 1986). This estimate has been recalculated as 4,250 pairs, based on the same pair density data but using new data on relative densities in different habitats and total habitat areas (Cuthbert and Sommer 2004). In 1984, the Tristan population was estimated at c.250 pairs and increasing. It is now distributed throughout the island, being scarce or absent only in the west (P. G. Ryan in litt. 2000).

Countries:
Native:
Saint Helena, Ascension and Tristan da Cunha
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The total population is estimated at 9,000 mature individuals based on past survey data, including 4,250 pairs on Gough based on 1983 data, and 250 pairs on Tristan in 1984 (P. G. Ryan in litt. 2000). This is roughly equivalent to 13,000-14,000 individuals in total.
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: On Gough, it is found near the coast, in boggy areas and close to streams, being most common in fern-bush, and somewhat less common in level areas of tussock grassland; it is very scarce or absent in wet heath (Watkins and Furness 1986, P. G. Ryan in litt. 1999, P. G. Ryan in litt. 2000, Cuthbert and Sommer 2004). On Tristan, where no tussock remains, it is found in fern-bush (P. G. Ryan in litt. 1999). It feeds on vegetable matter, seeds, invertebrates and carrion, and scavenges petrel carcasses. It also forages for invertebrates in abandoned and active albatross nests, petrel burrows, and will feed on garbage (Watkins and Furness 1986). It breeds from September to March, on Gough peaking between October and December, and laying between two and five eggs (Watkins and Furness 1986, P. G. Ryan in litt. 1999).

Systems: Terrestrial; Freshwater

Threats [top]

Major Threat(s): It is likely that G. nesiotis was extirpated from Tristan as a result of predation by black rat Rattus rattus (P. G. Ryan in litt. 1999), though this may have been in combination with feral cat and pig predation, habitat destruction and hunting by islanders (P. G. Ryan in litt. 2000). The successful establishment of G. nesiotis on Tristan suggests that it is able to cope with current levels of predation by rats, but the greatest risk to the species is still the accidental introduction of this (or another) predator to its stronghold on Gough. Birds have been observed taking live House Mice Mus musculus and scavenging mouse carcasses on Gough (Wanless and Wilson 2007), making it vital that any attempted mouse eradication using poisoned baits takes adequate measures to reduce the potential impact of secondary poisoning on moorhens .

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
On Tristan, a programme to eradicate cats was successful in the 1970s. Gough is a nature reserve and World Heritage Site and is uninhabited apart from the staff who run a meteorological station (Cooper and Ryan 1994). A repeatable monitoring protocol for the species was devised during 2000/1 (Cuthbert and Sommer 2004). 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 Moorhen) 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
Minimise the risk of the introduction of exotic flora and fauna, particularly mammalian predators, to Gough (P. G. Ryan in litt. 1999). Repeat population monitoring at intervals of 5-10 years.

Citation: BirdLife International 2012. Gallinula nesiotis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 24 April 2014.
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