• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

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.

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

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	64 km2	medium
Area of Occupancy (breeding/resident)	64 km2	good
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	2550-6360, 4100 mature individuals	poor	estimated	2020
Population trend	decreasing	medium	inferred	-
Generation length	3.05 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals 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 A more recent survey in 2016 (Director of National Parks unpublished, in Nance et al. 2021) detected little change.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	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Norfolk Island (to Australia)	extant	native	yes

Country/Territory	IBA Name
Norfolk Island (to Australia)	Norfolk Island

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

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

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Recommended citation
BirdLife International (2024) Species factsheet: Slender-billed White-eye Zosterops tenuirostris. Downloaded from https://datazone.birdlife.org/species/factsheet/slender-billed-white-eye-zosterops-tenuirostris on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 23/11/2024.