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

Justification of Red List category
This species occurs at low densities, and is inferred to have a small population experiencing a continued decline. It has therefore been listed as Near Threatened.

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%.

Ploceus nicolli occurs at low densities in the East and West Usambara, Uluguru and Udzungwa Mountains in Tanzania. In the West Usambaras, the nominate subspecies occurs in small numbers at Shume, Magamba and Mazumbai (N. Baker in litt. 1999). In the East Usambaras, it is fairly common at two sites within the Nilo Forest Reserve (Cordeiro 1998; Seddon et al. 1999) - probably the subspecies's last remaining stronghold (Seddon et al. 1999). P. n. anderseni is found in the Uluguru Mountains (three records, all from Uluguru North Forest Reserve (Svendsen and Hansen 1995), but not recorded during surveys in 1999-2001 [Burgess et al. 2002]) and the Udzungwa Mountains, including Udzungwa National Park, Ndundulu Forest and the Nyumbanitu Mountains, as well as in a tiny patch of forest c.95 km east of Iringa and in the Udzungwa Scarp Forest Reserve (D. Moyer in litt. 1999). There is a possible record from the Rubeho Mountains, but this has not been confirmed (Fjeldså et al. 1997). The Udzungwa mountains are likely to support the largest population of this species, though it is found at low densities (Jensen et al. 2020). The total population has been guessed to number over 1,000 individuals (Seddon et al. 1999). However, the population in the Udzungwas alone might number 1,000-2,000 individuals (L. Hansen in litt. 2007), although it has been conservatively guessed at 'some hundred' (Dinesen et al. 2001).

It inhabits montane evergreen forest, as well as forest edge (Zimmerman et al. 1996) and disturbed forest (Cordeiro 1998). Birds have also been seen in plantations and in cultivated areas, but only where mature trees still exist (Seddon et al. 1999). It usually occurs in mixed-species parties, often with P. bicolor, feeding in the upper canopy, gleaning insects from epiphyte-covered branches (Svendsen and Hansen 1995; Cordeiro 1998).

The increasing human population throughout its range is clearing or altering forest for agriculture, replacing natural forest with plantations, cutting timber and collecting firewood, resulting in loss, degradation and fragmentation of the species's habitat (Svendsen and Hansen 1995, Cordeiro 1998). Although the main montane forest block (120 km²) in the Ulugurus is protected by its inaccessible terrain, the lower slopes are being steadily cleared. Forest in the Ulugurus declined from c.300 km² in 1955 to c.230 km² in 2001, mostly due to clearance for cultivation below 1,600 m (Burgess et al. 2002).  The Ulugurus forests are also under increasing pressure from harvesting for firewood and construction resulting from the increasing population (L. Hansen in litt. 2020). In Nilo Forest Reserve, understory cultivation (mainly of cardamom) occurs in c.36% of the forest, and a further 6% is cultivated for arable crops (Cordeiro 1998). Habitat in the Nyumbanitu Mountains, Ukami and Ndundulu Forests and Udzungwa National Park has recently been affected by the clearing of broad tourist trails, allowing easier access by hunters and predatory mammals (L. Hansen in litt. 2007). Tourism has increased since the 1990s, and an estimated 30-40% of the forest is accessible to tourists (L. Hansen in litt. 2020). Aside from this degradation, the species's habitat in the Udzungwas is not seen as being immediately threatened, although pressure is increasing (L. Dinesen in litt. 2007).

Conservation Actions Underway
Conservation action at some sites focuses on assisting local initiatives and increasing the involvement of local communities in forest management (Buckley and Matilya 1998; L. Dinesen in litt. 2007). The Udzungwa localities fall within forest catchment reserves or have national park status (L. Dinesen in litt. 2007). An extensive survey to re-evaluate the forest and avifauna is planned for 2023 (L. Hansen in litt. 2020).

Conservation Actions Proposed
Conduct a survey to assess the species's population size across its range, and survey the Rubeho Mountains to confirm previous reports of the species's occurrence. Monitor population and habitat trends. Establish a coordinated management scheme for Mt Nilo Forest Reserve and adjacent forest in the East Usambaras (Cordeiro 1998). Improve the management of existing protected areas within the species's range. Increase the area of suitable habitat that is covered by protected areas or community-based forest management.

13-14 cm. Medium-sized, nuthatch-like weaver of forest. Most likely to be seen in the upper strata and canopy only. Matt black upperparts. Dark brown, almost black, head with dull yellow forehead and yellowish nuchal patch. Lemon-yellow underparts. Below the blackish bib there is a diffuse orange-brown patch, broadest at its centre. Female similar but with brown head. Bright yellow eye in both sexes. Bill black. Similar spp. Forest Weaver P. bicolor lacks chestnut breast-band and has ivory coloured bill. Voice Soft but rather high pitched si swee-ee. Rather vocal when feeding. Voice not far from that of Grey Cuckoo-Shrike Coracina caesia. Hints Shy. Most frequently seen above 1,400 m in Mazumbai forest, West Usambara Mountains, Tanzania.

Text account compilers
Clark, J.

Contributors
Baker, N., Dinesen, L., Ekstrom, J., Evans, M., Hansen, L., Moyer, D., Shutes, S., Starkey, M., Symes, A., Taylor, J. & Westrip, J.R.S.

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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.