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Zosterops albogularis 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Zosteropidae

Scientific Name: Zosterops albogularis
Species Authority: Gould, 1837
Common Name(s):
English White-chested White-eye, White-breasted Silvereye
Spanish Gafudo Gorgiblanco
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: 13-14 cm. Medium-sized, warbler-like bird. Sexes similar. Bright green head, olive-green back, clear white underparts and white eye-ring. Similar spp. Distinguished from other White-eyes Zosterops spp. by large size and white underparts.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(v);C2a(i,ii);D 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., Dutson, G., Holdaway, R., Ward, R. & Watson, B.
Facilitator/Compiler(s): Bird, J., Calvert, R., Derhé, M., Garnett, S., McClellan, R., Stattersfield, A., Symes, A. & Khwaja, N.
Justification:
This species appears to have declined as a result of predation by introduced rats, exacerbated by habitat destruction and degradation through invasion of exotic weeds. Formal surveys have failed to find any in the last two decades. There have been a number of other reports during 1978-2005, however a three-week survey in 2010 failed to find the species and estimated a 90% chance that the species is functionally extinct (Dutson 2013). A tiny population may however remain and therefore it is treated as Critically Endangered.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Zosterops albogularis is endemic to Norfolk Island (to Australia). It was reported as "very plentiful" by Hull (1909) and 12 specimens were taken in one week in 1926 by Correia. However, the population is thought to have fallen below 50 individuals by 1962 (Mees 1969), and by the 1970s it had become confined to weed-free indigenous forest in and around the Norfolk Island National Park. Although formal searches have failed to find any in the last three decades, there have been scattered sightings throughout this period (Schodde et al. 1983),  including one in 1987, two in 1991, four in 1994 and one in 2000. Since then a number of unconfirmed reports have been logged from the Norfolk Island National Park, most recently in 2006 (B. Watson in litt. 2006, G. Dutson in litt. 2009, 2010). The remaining population, if any exists, is likely to be very small; a comprehensive three-week survey in November 2009 based on 353 point counts failed to find the species and concluded there was a 90% chance that it was functionally extinct (G. Dutson in litt. 2009, 2010, Dutson 2013).

Countries occurrence:
Native:
Norfolk Island
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:5
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 remaining population is assumed to be tiny (fewer than 50 individuals and mature individuals), with only scattered sightings since 1978.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:1-49Continuing decline of mature individuals:Yes
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 appears to occur mostly in weed-free indigenous forest, feeding high in shrubs and trees. However, there are old records of it nesting in orchards (Hull 1909), in red guava Pisidium cattleianum trees, and feeding on olive fruits (Mees 1969).

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):3.5
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): The principal threat is probably predation by black rat Rattus rattus, which is thought to have been introduced in the mid-1940s. The effects of predation have been exacerbated by the clearance of much native forest and invasion of the remainder by exotic weeds. As a result, favoured habitat has been reduced to less than 1% of the area of the island. Competition from the self-introduced Silvereye Z. lateralis, which was first recorded on the island in 1904, may also have contributed to the decline, and recent drought years may have stressed the population further (R. Ward in litt. 2006). Predation by feral cats Felis catus may also be a threat. The species may be vulnerable to climate changes and appears to fare poorly during dry years.

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
CITES Appendix I. Surveys were carried out for the species, without success, in 2009 (G. Dutson in litt. 2012). Rat baiting, cat trapping and control of other invasive plants and animals is occurring in Norfolk Island National Park. Responsible cat ownership is being encouraged through sponsorship of cat neutering clinics. The species is being considered in a multi-species management plan for Norfolk Island National Park.  A predator exclusion fence was proposed for Norfolk Island National Park to create a predator free "island" within the park (B. Watson in litt. 2006), but this idea hasn't gained traction, likely due to the costs and maintenance involved (M. Christian pers comms 2016). The Australian commonwealth has recently rated Norfolk Island very high on its list of the Australian islands in which they are considering the eradication of invasive rodents, with a possible $20 million investment in the chosen islands over a number of years (M. Christian in litt. 2008).

Conservation Actions Proposed
Determine a method for finding the birds reliably and conduct thorough surveys to estimate the remaining population size. Survey both native and introduced vegetation, as some recent reports refer to the latter (R. Holdaway in litt. 2012). Establish cooperative rodent control programmes in areas where community support is strong (M. Christian pers comms. 2016). Enhance rat baiting and cat trapping on Norfolk Island and monitor their efficacy. If birds are located, perhaps consider whether establishing a captive-breeding population is feasible. Continue to restore native habitat across Norfolk Island. Introduce to Phillip Island following revegetation. Gain support and funding from external sources to facilitate conservation actions.


Citation: BirdLife International. 2016. Zosterops albogularis. The IUCN Red List of Threatened Species 2016: e.T22714229A95227966. . Downloaded on 23 March 2017.
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