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

Taxonomic note

Acrocephalus rimitarae (del Hoyo and Collar 2016) was previously listed as A. rimatarae.

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
B1ab(v)	B1ab(v)+2ab(v); C2a(ii)	A2b+3b+4b; B1ab(v)+2ab(v); C2a(i,ii); D1+2

Red List history

Year	Category	Criteria
2021	Critically Endangered	B1ab(v)
2017	Critically Endangered	B1ab(iii,v)
2016	Vulnerable	D1+2
2012	Vulnerable	D1+2
2008	Vulnerable	D1; D2
2006	Vulnerable
2004	Vulnerable
2000	Vulnerable
1994	Not Recognised
1988	Not Recognised

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	7 km2	medium
Area of Occupancy (breeding/resident)	16 km2
Number of locations	1	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	600-1900 mature individuals	medium	estimated	2017
Population trend	decreasing	poor	estimated	2012-2022
Rate of change over the past 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	30-49%	-	-	-
Generation length	3.19 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: The species is considered to be abundant over much of Rimatara (P. Raust in litt. 2012, C. Blanvillain in litt. 2016 per G. Dutson in litt. 2016). Various population estimates have been made which differ widely depending on methods used and the season in which the surveys took place. Applying a correction to account for differences in methodology would lead to higher estimates from the transect surveys (Blanvillain et al. 2015). There was a 35% difference in the numbers recorded in May and September 2017, with the lower number recorded in May, possibly due to the birds behaving more secretively in winter (SOP-Manu 2019).

Point count observations in 2002 gave a population estimate of 3,851 birds (Blanvillain 2002), but transect surveys in the same year estimated 740 individuals (Raust and Sanford 2002). In 2004, transect surveys gave an estimate of 675 individuals (Gouni 2004) and territory mapping techniques used by Thibault and Cibois (2006a) gave estimates of 1,777-2,567 breeding birds (roughly 2,665-3,850 individuals), with a population density estimate of just over 3 birds per hectare in good habitat (Thibault and Cibois 2006a). Transect surveys in 2009 produced a population estimate of 677 individuals (Albar et al. 2009).

The most recent surveys were carried out in autumn-winter 2017, following the transect methodology used by previous surveys, with the addition of the use distance sampling. Without applying distance sampling, the resulting population estimate was 1,475 individuals in May 2017 and 958 individuals in September (SOP-Manu 2019). Following the application of distance sampling software, the population size was estimated at 2,225 (1,780 - 2,781) individuals in May 2017 and 1,444 (1,022 - 2,040) individuals in September 2017 (SOP-Manu 2019). This roughly equates to 681 - 1,854 mature individuals, here placed in the band 600-1,900 mature individuals.

Trend justification: Although the differences in survey methods used make it difficult to determine trends, the most recent estimates are lower than the estimate obtained by point count suveys in 2002 (3,851 individuals; Blanvillain 2002) and the estimated number of individuals derived from territory mapping in 2004 (roughly 2,665-3,850 individuals; Thibault & Cibois 2006a), so the population is considered to be declining (SOP-Manu 2019). Based on these figures, a reduction of 30-49% over the past ten years is suspected, and is assumed to be continuing into the future at a similar rate.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
French Polynesia	extant	native	yes

Country/Territory	IBA Name
French Polynesia	Rimatara

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Plantations	major	resident
Forest	Subtropical/Tropical Dry	suitable	resident
Shrubland	Subtropical/Tropical Dry	major	resident
Wetlands (inland)	Bogs, Marshes, Swamps, Fens, Peatlands	suitable	resident
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Acridotheres tristis	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Rapid Declines		Low Impact: 5
		Stresses Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus exulans	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Negligible declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus norvegicus	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Negligible declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus rattus	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Rapid Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Residential & commercial development	Tourism & recreation areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Rimatara Reed-warbler Acrocephalus rimitarae. Downloaded from https://datazone.birdlife.org/species/factsheet/rimatara-reed-warbler-acrocephalus-rimitarae on 22/12/2024.
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 22/12/2024.