Data Zone
Justification of Red List category
Ruvu Weaver has only recently been established as certainly a separate species after having initially been recognised more than a hundred years ago. It has a small range and is suspected to have a very small or small population size. Because of the latter it is assessed as Near Threatened, however it is noted that the species' distribution does not appear to have changed significantly in a century and there do not appear to be significant threats to the species, which occurs in dynamic early succession habitat and has a degree of flexibility in nesting site habitat. Monitoring of colonies is recommended to produce a more precise population estimate.
Population justification
The population size is uncertain due to species status only being clarified recently. However, an initial assessment based on the distribution of colonies located, including extensive searches in stretches where the species is absent, suspects a small population size that is likely in the low thousands (Oschadleus et al. 2021). While this is not an estimate, the population size is therefore suspected to fall between 1,000 and 5,000 individuals, indicating that the lower bound of the number of mature individuals falls below 1,000. Further exploration of the habitat along the rivers along which it is known to occur may result in an increase in this initial value.
Trend justification
In the absence of significant threats likely to have population implications, and in observing the persistence of the species in the same localities and apparently across a similar distribution as noted more than a century previously, the population is suspected to be stable.
Ruvu Weaver occurs along three rivers in eastern Tanzania; the Ruvu River up to 100 km upstream, along the lower Wami River and along the lower Rufiji River from Lake Tagalala to the Selous Game Reserve (Oschadleus et al. 2021). This restricted range does not overlap with that of Kilombero Weaver P. burnieri, which occurs upstream of Lake Tagalala. The full occupancy of the identified range is unknown, but the area of occurrence may be moderately small, while the extent of occurrence is estimated at 17,900 km. There is no evidence that the range of the species has altered significantly since the first description of the species in 1891 (Hartlaub 1891), though more research is required.
The species appears to be restricted to the vicinity of river channels and uses bankside or emergent vegetation for nesting. Its nest is similar to African Golden Weaver P. subaureus, kidney-shaped with the entrance at the base and directly attached to stems at the roof but is less tightly woven (Oschadleus et al. 2021). Nests have been found on a variety of bushes, bamboo and Phragmites stems with up to 15 nests in a tree (Oschadleus et al. 2021).
The restriction of the species to riverside habitats along only three rivers may expose the species to threats that alter the hydrology of those rivers. It appears to have flexibility in its use of vegetation and occurs in a dynamic landscape with seemingly little change to its distribution since first collected over 120 years ago. This suggests that the changes to the habitat to date have not adversely impacted the species. There is a potential future threat from a proposal to construct a large reservoir 140 km upstream of Mtoni: this is suspected to result in an increase in open habitats in this area that may favour the ecologically (and visually) similar P. subaureus and therefore reduce the range and population of the present species (Oschadleus et al. 2021). The distribution of P. subaureus has expanded in this region and the sympatric occurrence of the two may be explained by secondary contact rather than being a stable situation (Oschadleus et al. 2021). While uncertain, this may result in negative competitive impacts on Ruvu Weaver but as yet hybridisation or exclusion have not been documented. The two species do not appear to be especially closely related (Fjeldså et al. 2020) hence reproductive isolation may be robust, but competition may occur.
Conservation Actions Proposed
Research into this species should initially focus on the further exploration of suitable habitat for additional colonies/occupied rivers to determine the occupied range and allow for the creation of a formal population estimate. Weaver colonies should be monitored as part of efforts to determine trends for all bird species in Tanzania. Impacts of proposed dam schemes must include provision for the maintenance of similar flow rates in downstream areas.
Text account compilers
Martin, R.
Recommended citation
BirdLife International (2025) Species factsheet: Ruvu Weaver Ploceus holoxanthus. Downloaded from
https://datazone.birdlife.org/species/factsheet/ruvu-weaver-ploceus-holoxanthus on 24/01/2025.
Recommended citation for factsheets for more than one species: BirdLife International (2025) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 24/01/2025.