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Gerygone modesta 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Acanthizidae

Scientific Name: Gerygone modesta
Species Authority: Pelzeln, 1860
Common Name(s):
English Norfolk Gerygone, Norfolk Island Gerygone
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 9-10 cm. Small, dull-coloured warbler. Dull grey-brown above and whitish below, greyer on face and flanks. Sexes similar. Slender, longish, black bill. White line from base of bill, above dark lores, over eyes. Broken white orbital ring. Tail has indistinct darker subterminal band with white spots except on central feathers. Juvenile more yellow, especially on throat. Similar spp. White-eyes Zosterops spp. are larger with prominent white eye-ring, more yellow or green overall and with differing voice. Voice Warble, rising and falling in pitch.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Christian, M., Holdaway, R. & Ward, R.
Facilitator/Compiler(s): Benstead, P., Garnett, S., McClellan, R., Symes, A. & Taylor, J.
Justification:
This species is classified as Near Threatened because although it has a very small range and population on a single island, its population is estimated to be stable or increasing and it has not been significantly affected by introduced predators, including rats, and therefore there is not thought to be any plausible threat likely to lead to very rapid future declines. If such a plausible future threat were to be identified it would warrant classification as Vulnerable, and any evidence of declines would likely lead to its reclassification in a higher threat category.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Gerygone modesta is endemic to Norfolk Island (to Australia). It is widespread and abundant on the island, and is thought to number c.10,000 individuals (Garnett et al. 2011). The population is probably stable (R. Ward, M. Christian and R. Holdaway in litt. 2007, Garnett et al. 2011).

Countries occurrence:
Native:
Norfolk Island
Additional data:
Estimated area of occupancy (AOO) - km2:36Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:45
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The population within Norfolk Island National Park is estimated at at least 3,800 pairs (G. Dutson pers. obs.), with many more hundreds outside the park. The total population is therefore estimated at c.10,000 mature individuals (Garnett et al. 2011).

Trend Justification:  The population is suspected to be stable or slightly increasing (Garnett and Crowley 2000; R. Ward, M. Christian and R. Holdaway in litt. 2007, Garnett et al. 2011), and there are no immediate serious threats to the species.
Current Population Trend:Stable
Additional data:
Number of mature individuals:10000Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:It is found only in remnant areas of tree or shrub growth on the island, such as rainforest, thicket, gardens and white oak pasture, and is common in weedy forest dominated by the exotic red guava Psidium cattleianum and African olive Olea africana but at a density about half that in native forest (G. Dutson pers. obs.). It is scattered and much less common in patchy forest and scrub away from the National Park (G. Dutson pers. obs.).

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):5.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): Although clearing for timber, cultivation, pasture and ongoing development (R. Ward, M. Christian and R. Holdaway in litt. 2007) has removed some habitat, there are no apparent serious threats that are likely to affect the viability of the population in the foreseeable future, but its restriction to such a small area could make it susceptible to catastrophe such as newly-introduced predators or disease. The population may be affected by the clearing of hedges and vacant land for the development of domestic and commercial buildings (R. Ward, M. Christian and R. Holdaway in litt. 2007). It coexists with the introduced black rat Rattus rattus and cats, and its behaviour and the positioning of its domed nests reduces the probability of predation (Garnett and Crowley 2000).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Norfolk Island National Park was declared in 1986, and encompasses the main remaining stands of native forest on the island. Although the control of mammalian predators takes place within the Norfolk Island National Park, in 2006, it was noted that the control of rats was budget-constrained and limited in its effectiveness (S. Garnett in litt. 2006). There is an ongoing programme to control exotic shrubs within native forest in the National Park (Garnett et al. 2011). The Norfolk Island Region Threatened Species Recovery Plan (Director of National Parks 2010) recommends a set of recovery measures required to reduce or remove threats to native species on the island.

Conservation Actions Proposed
Monitor the population through the analysis of birdwatchers' records. Install predator-proof fencing around the national park and other important habitat and remove introduced predators from within these areas (R. Ward, M. Christian and R. Holdaway in litt. 2007). The elimination of mammalian predators from the island in areas of local community support, with measures to prevent their reintroduction (Director of National Parks 2010), may benefit the species, despite them not being a serious threat.


Citation: BirdLife International. 2016. Gerygone modesta. The IUCN Red List of Threatened Species 2016: e.T22704731A95227052. . Downloaded on 29 March 2017.
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