Species

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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. A tiny population may however remain and therefore it is treated as Critically Endangered.

Taxonomic source(s)
Christidis, L.; Boles, W. E. 1994. The taxonomy and species of birds of Australia and its territories. Royal Australasian Ornithologists' Union, Melbourne.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Identification
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.

Distribution and population
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).

Population justification
The remaining population is assumed to be tiny (fewer than 50 individuals and mature individuals), with only scattered sightings since 1978

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).


Threats
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 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. Possibilities of captive breeding and securing additional funding to finance recovery efforts are being pursued. A predator exclusion fence has been proposed for Norfolk Island National Park to create a predator free "island" within the park (B. Watson in litt. 2006), and the proposal is now supported by the WWF and the Norfolk Island government. The Australian government 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 throughout Norfolk Island, with a view to rat eradication throughout the island (G. Dutson in litt. 2012). 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.

Related state of the world's birds case studies

• Are we doing enough to save the world's birds?

References
Garnett, S. T.; Crowley, G. M. 2000. The action plan for Australian birds 2000. Environment Australia, Canberra.

Further web sources of information
Alliance for Zero Extinction (AZE) species/site profile. This species has been identified as an AZE trigger due to its IUCN Red List status and limited range.

Australian Govt - Action Plan for Australian Birds 2000 - Recovery Outline

Click here for more information about the Alliance for Zero Extinction (AZE)

View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Bird, J., Calvert, R., Derhé, M., Garnett, S., Khwaja, N., McClellan, R., Stattersfield, A., Symes, A.

Contributors
Christian, M., Dutson, G., Holdaway, R., Ward, R., Watson, B.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Zosterops albogularis. Downloaded from http://www.birdlife.org on 20/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.