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

Taxonomic note

Zosterops conspicillatus and Z. saypani (del Hoyo and Collar 2016) were previously lumped as Z. conspicillatus following Slikas et al. (2000).

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.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	-

Red List history

Year	Category	Criteria
2022	Near Threatened	B1a+2a; D2
2016	Endangered	A3e+4e; B1ab(v)
2012	Not Recognised
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Lower Risk/Near Threatened
1988	Not Recognised

Migratory status	not a migrant	Forest dependency	medium
Land-mass type		Average mass	8 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	3,090 km2	medium
Area of Occupancy (breeding/resident)	444 km2
Number of locations	4-5	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	410000-630000, 510000 mature individuals	good	estimated	2014
Population trend	stable	poor	suspected	-
Generation length	2.55 years	-	-	-
Number of subpopulations	4-5	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: Among the commonest landbirds in its range (Pyle et al. 2010). The population was estimated to be 534,029 (95% CI: 427,858-650,667) individuals on Saipan in 2007 (Camp et al. 2009), 225,360 (95% CI: 192,080-283,200) individuals on Tinian and 3,388 (95% CI – 2,492-4,909) individuals on Aguijan in 2008 (Amidon et al. 2014). A total of 196 Saipan White-eyes, captured on Saipan, were translocated to northern islands in the chain with no permanent human populations; in 2008 and 2009 to the island of Sarigan (100 birds), and in 2015 and 2016 to the island of Guguan (96 birds) [K. Reininger in litt. 2021]. In June 2016, point transect surveys were conducted on Sarigan to evaluate the initial success of the translocation program. A population estimate of 8,239 birds from this survey (Amidon 2017) indicate the translocated birds had survived and were readily reproducing thus are considered in the population totals given here. A post-translocation survey of Guguan is planned, however given current uncertainty over whether they are reproducing, that they constitute a viable breeding population cannot be assumed and precautionarily this population is excluded from the totals given herein. The population size is not believed to have substantially changed since these estimates were made and therefore the population size is estimated at 630,000-950,000 individuals, or approximately 410,000-630,000 mature individuals.

Trend justification: A future decline of this species was formerly considered an inevitability due to the accidental introduction of Brown Tree Snakes Boiga irregularis. However, this threat has so far been kept at bay, principally due to biosecurity measures (see Yackel Adams et al. 2021). In the absence of additional threats acting on this species, the population is therefore considered to be stable while on the islands of its recent introduction (Sarigan and Guguan) it may be increasing until carrying capacity is reached.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Northern Mariana Islands (to USA)	extant	native	yes

Country/Territory	IBA Name
Northern Mariana Islands (to USA)	Aguiguan Island and Naftan Rock
Northern Mariana Islands (to USA)	Northern Saipan
Northern Mariana Islands (to USA)	Tinian Island
Northern Mariana Islands (to USA)	Topachau-Susupe-Kagman

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Plantations	suitable	resident
Artificial/Terrestrial	Rural Gardens	suitable	resident
Forest	Subtropical/Tropical Moist Lowland	major	resident
Shrubland	Subtropical/Tropical Moist	suitable	resident
Altitude	0 - 475 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Boiga irregularis	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Rapid Declines		Low Impact: 5
		Stresses Reduced reproductive success, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Saipan White-eye Zosterops saypani. Downloaded from https://datazone.birdlife.org/species/factsheet/saipan-white-eye-zosterops-saypani 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.