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

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
-	C2a(i)	C2a(i); D1

Red List history

Year	Category	Criteria
2021	Near Threatened	C2a(i); D1
2016	Endangered	C2a(i)
2012	Endangered	C2a(i)
2008	Endangered	C2a(i)
2004	Endangered
2000	Endangered
1996	Vulnerable
1994	Vulnerable
1988	Threatened

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	51,900 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	600-1700 mature individuals	poor	inferred	2000
Population trend	decreasing	medium	inferred	2016-2027
Rate of change over the past 10 years/3 generations (longer of the two periods)	1-15%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	1-15%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	1-15%	-	-	-
Generation length	3.6 years	-	-	-
Number of subpopulations	2-3	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: The total population has been guessed to number over 1,000 individuals (Seddon et al. 1999), and possibly over 2,500 individuals, but not more than 5,000 (L. Hansen in litt. 2016). The population in the Udzungwas alone might number 1,000-2,000 individuals (L. Hansen in litt. 2007), although it has also been guessed at 'some hundred' (Dinesen et al. 2001). Therefore, the population is conservatively placed in the range of 1,000-2,499 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This is roughly equivalent to 667-1,666 mature individuals, rounded here to 600-1,700 mature individuals.

Trend justification: This species is inferred to be declining due to ongoing forest loss (Global Forest Watch 2021). The forest is being cleared, altered and fragmented for agriculture, plantations and timber extraction (Svendsen and Hansen 1995; Cordeiro 1998).

Between 2000-2019, this species experienced forest cover loss of 8.1% (Global Forest Watch 2021). This species has a high forest dependency and assuming that the population declines at a similar rate, this would equate to a rate of decline of c.5% over the past 3 generations. Green et al. (2013) estimated that the entire Eastern Arc mountain range lost 26% of forests between 1975-2000, which would equate to a decline rate of 11% over 3 generations. Between 2016-2019, this species's experienced a loss of forest cover of 3% (Global Forest Watch 2021). Projected forward over 3 generations, this would equate to a loss of 8%. The overall population decline is suspected to fall into the band 1-15%.

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

Country/Territory	IBA Name
Tanzania	East Usambara Mountains
Tanzania	Rubeho Mountains
Tanzania	Udzungwa Mountains
Tanzania	Udzungwa National Park
Tanzania	Uluguru Mountains
Tanzania	West Usambara Mountains

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	900 - 1850 m	Occasional altitudinal limits	(max) 2200 m

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Wood & pulp plantations - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Species disturbance, Ecosystem degradation

Purpose	Scale
Pets/display animals, horticulture	international

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Recommended citation
BirdLife International (2024) Species factsheet: Usambara Weaver Ploceus nicolli. Downloaded from https://datazone.birdlife.org/species/factsheet/usambara-weaver-ploceus-nicolli on 26/12/2024.
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 26/12/2024.