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Nesocichla eremita 

Scope:Global
Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_onStatus_vu_offStatus_en_offStatus_cr_offStatus_ew_offStatus_ex_off

Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Turdidae

Scientific Name: Nesocichla eremita
Species Authority: Gould, 1855
Common Name(s):
English Tristan Thrush

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Taylor, J. & Butchart, S.
Contributor(s): Rowlands, B. & Ryan, P.G.
Facilitator/Compiler(s): O'Brien, A., Robertson, P., Symes, A., Taylor, J.
Justification:
This species is classed as Near Threatened because it has a small population, which occupies a restricted range. There is presently no serious threat to the species and no evidence of declines in either its population or range, but if such evidence was obtained this species might qualify for a higher threat category.

Previously published Red List assessments:
  • 2008 – Near Threatened (NT)
  • 2004 – Near Threatened (NT)
  • 2000 – Lower Risk/near threatened (LR/nt)
  • 1994 – Lower Risk/near threatened (LR/nt)
  • 1988 – Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description:Nesocichla eremita is endemic to Tristan da Cunha (to UK) in the South Atlantic Ocean, where it is found on Tristan, Inaccessible, Nightingale, Middle and Stoltenhoff islands with distinct subspecies on each of the three main islands. In 1972-1974, island population sizes were estimated as follows (in pairs): Tristan 40-60; Inaccessible 100-500; Nightingale 300-500; Middle 20-40; and Stoltenhoff 10-20 (Richardson 1984). In the 1980s, the Inaccessible population was revised to 850 pairs, and the total population for the group to 6,000 birds (Fraser et al. 1994). More recently, the Tristan population has been estimated (very crudely, but conservatively) as at least several hundred birds (P. G. Ryan in litt. 2000).

Countries occurrence:
Native:
Saint Helena, Ascension and Tristan da Cunha
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:120
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):300
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In 1972-1974, island population sizes were estimated as follows (in pairs): Tristan 40-60; Inaccessible 100-500; Nightingale 300-500; Middle 20-40; and Stoltenhoff 10-20. In the 1980s, the Inaccessible population was revised to 850 pairs, and the total population for the group to 6,000 birds. More recently, the Tristan population has been estimated (very crudely, but conservatively) as at least several hundred birds (P. G. Ryan in litt. 2000). It is best placed in the band 2,500-9,999 individuals, equating to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.

Trend Justification:  There is presently no serious threat to the species and no evidence of declines in either its population or range, thus the species's population is currently suspected to be stable.
Current Population Trend:Stable
Additional data:
Number of mature individuals:1500-7000Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:The species uses virtually all available habitats including boulder-strewn shorelines, tussock grassland, fern-bush and wet heath. It feeds opportunistically on dead birds, fish offal, kitchen scraps and the eggs and fledglings of other birds as well as earthworms and invertebrates taken from leaves and detritus (Fraser et al. 1994, del Hoyo et al. 2005). Breeding takes place in September-February (del Hoyo et al. 2005). Its nest is a rough cup of woven tussock fronds and grass stalks with some moss and leaves, placed on or just above the ground. It lays two or three, sometimes four, eggs. The fledging period is c.20 days (del Hoyo et al. 2005).

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):4.3
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): On Tristan, predation by black rats Rattus rattus is a possible threat. Translocations of birds between islands, a common practice in the past, resulting in hybridisation, is another concern (P. G. Ryan in litt. 2000).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Cats were a major problem on Tristan, but have been eradicated (del Hoyo et al. 2005).

Conservation Actions Proposed
Carry out surveys to obtain an up-to-date total population estimate. Monitor population trends through regular surveys. Assess the impact of predation by rats. Control rat numbers on Tristan, and prevent further introductions of mammalian predators. Legislate against the transportation of the species between islands.


Citation: BirdLife International. 2012. Nesocichla eremita. The IUCN Red List of Threatened Species 2012: e.T22708541A39745117. . Downloaded on 26 July 2016.
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