VU
Slender-billed White-eye Zosterops tenuirostris



Taxonomy

Taxonomic source(s)
Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
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.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - C2a(ii)

Red List history
Year Category Criteria
2022 Vulnerable C2a(ii)
2016 Near Threatened D2
2013 Near Threatened D2
2012 Near Threatened D2
2008 Endangered B1a+b(ii,iv,v); B2a+b(ii,iv,v); C2a(ii)
2004 Endangered
2000 Endangered
1996 Vulnerable
1994 Vulnerable
1988 Lower Risk/Least Concern
Species attributes

Migratory status not a migrant Forest dependency High
Land mass type Average mass -
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 64 medium
Extent of Occurrence breeding/resident (km2) 64 good
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 2550-6360, 4100 poor estimated 2020
Population trend Decreasing medium inferred -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations 1 - - -
Percentage in largest subpopulation 100 - - -

Population justification: There were an estimated 4,030 (95% CI 2,550–6,360) Z. tenuirostris in Norfolk Island National Park in 2009 (Dutson 2013). A more recent survey in 2016 (Director of National Parks unpublished, in Nance et al. 2021) detected little change. There are now very few birds left outside the national park (Nance et al. 2021), hence the best estimate of the population is made at 4,100 mature individuals.

Trend justification:

Within the national park, data collected between 2009 (4,030 mature individuals; 95% CI 2,550-6,360) and 2016 ostensibly indicate no change in population size, though differences in survey techniques preclude direct comparisons of these years. There has however been a continued decline of birds outside of the national park: from 300-500 in the 1980s, including some areas where the bird was quite common (Robinson 1988) to very few now (Nance et al. 2021). Thus, while the population within the national park is assumed to be stable, an overall population decline is inferred based on reports that outside the national park, numbers continue to decline, principally as a result of black rats (Rattus rattus), which are yet to have been eradicated. These declines are therefore likely to continue into the future until either the threat has been eliminated, or the species becomes confined to the national park.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Norfolk Island (to Australia) N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Norfolk Island (to Australia) Norfolk Island

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Moist Lowland major resident
Altitude 0 - 300 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Agriculture & aquaculture Annual & perennial non-timber crops - Small-holder farming Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture Livestock farming & ranching - Small-holder grazing, ranching or farming Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion
Biological resource use Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest] Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Felis catus Timing Scope Severity Impact
Ongoing Whole (>90%) Slow, Significant Declines Medium Impact: 7
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus rattus Timing Scope Severity Impact
Ongoing Whole (>90%) Slow, Significant Declines Medium Impact: 7
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Unspecified species Timing Scope Severity Impact
Ongoing Majority (50-90%) Negligible declines Low Impact: 5
Stresses
Ecosystem degradation
Residential & commercial development Housing & urban areas Timing Scope Severity Impact
Past, Unlikely to Return Majority (50-90%) Slow, Significant Declines Past Impact
Stresses
Ecosystem degradation, Ecosystem conversion

Recommended citation
BirdLife International (2022) Species factsheet: Zosterops tenuirostris. Downloaded from http://www.birdlife.org on 30/09/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 30/09/2022.