Data Zone
Justification of Red List category
White-tailed Cisticola is restricted to a single floodplain system that has been subject to rapid and ongoing conversion of natural wet grassland vegetation to agriculture such that it is suspected to be currently undergoing a moderately rapid population reduction. The extent of occurrence is small and within this the quality and area of habitat is inferred to be declining. As such the species is considered Near Threatened.
Population justification
The species is described as the commonest cisticola within the Kilombero valley. Jones and John (2008) recorded it at 14 of 15 surveyed localities and in 81% of 159 point counts, while Rannestad et al. (2015) recorded 177 during surveys along a 60 km river transect. The density has been assessed at different times of year and in different habitats within the Kilombero riparian zone (Rannestad et al. 2015). Highest densities were recorded in both grass-bush habitat and reeds in June (during the highest water levels), with 31.3 ± 6.7 individuals per km2, in each habitat (Rannestad et al. 2015). These values are considered likely to related to mature individuals given that this likely the peak breeding season and detectability is high due to territorial vocalisation. Densities in other periods were lower, suggesting greater dispersion of individuals, reduced detectability, or seasonal movements out of the surveyed area. All three factors may be operating, given the seasonal flooding of the habitat likely concentrates individuals and may be the trigger for breeding (with resulting increased detectability).
The extent of assumed suitable habitat is unclear, even more so than for the sympatric C. bakerorum given that this species may occur in degraded habitat (Fjeldså et al. 2021). Wilson et al. (2017) report 1,515 km2 of wet grassland and reeds in 2016, while Leemhuis et al. (2017) report 2,166 km2 in the 'wetland' land cover class in 2016. Msofe et al. (2019) report an area of 'wetland' (excluding waterbodies) of 261 km2, suggesting considerable inconsistency in the land cover classifications used. With the species using drier habitat as well (Fjeldså et al. 2021), the area of suitable habitat is likely to be considerably larger than the very restricted value for wetland given by Msofe et al. (2019). Hence the population size likely exceeds 10,000 mature individuals: e.g. 31.3 mature individuals per km2 across the habitat extent values of Wilson et al. (2016 and Leemhuis et al. (2019) results in numbers between 47,420 and 67,796 individuals. These values are considered only indicative, given that the area values may not be accurately measuring the species' habitat extent if it does use a wider range of vegetation than C. bakerorum.
The population size is suspected to be declining due to the rate of conversion of wetland vegetation within the Kilombero valley (Wilson et al. 2016, Proswitz et al. 2021). Projecting the most recent rate of wetland grassland loss forwards (estimated in 2004 and 2016: Wilson et al. 2017) indicates the loss of 31% of the remaining vegetation by 2032, and 32% for the ten years between 2023 and 2033. However, as the species has been reported to use areas degraded by grazing, it is likely that the rate of population reduction is lower than this rate of conversion. On a precautionary basis the population is suspected to be declining at a rate between 20-29% over ten years.
Trend justification
The species is associated with the floodplain vegetation of the Kilombero valley, which is being converted to agriculture by a rapidly increasing human population (predicted to double by 2030: Proswitz et al. 2021) at a rate equivalent to at least 25% over the past ten years and in excess of 30% for the ten year period including the present year and for the ten year period commencing 2023 (based on data comparing land classifications over time in Wilson et al. [2017] and Leemhuis et al. [2017]).
This species does not appear to be extremely closely tied to the extent of the natural floodplain vegetation however, and the connection between the rate of habitat loss and the population size of C. anderseni is unclear. On a precautionary basis, given that the level of vegetation conversion is so rapid, it is suspected that there is a corresponding reduction in the population of between 10-25% over the past ten years 20-29% for the current and future ten year periods. Quantifying this is an important part of the monitoring work to be undertaken for the Integrated Management Plan for the Kilombero Valley Ramsar Site over the next decade (Wilson et al. 2017, Ministry of Natural Resources and Tourism 2018).
Cisticola anderseni is restricted to the Kilombero Valley floodplain in Tanzania, a very flat basin formed by the confluence of a number of rivers adjacent to the Udzungwa Mountains to the north and west and the Mahenge highlands to the east. Within this restricted area the species is apparently well-distributed and common (Rannestad et al. 2015, Fjeldså et al. 2021), and has been recorded within areas degraded by grazing by cattle and goats (Fjeldså et al. 2021). Records are slightly more widely distributed than those of C. bakerorum, which is more closely tied to flooded vegetation.
The southern limit to the distribution in the valley is taken to exclude the southernmost extent of the floodplain outside of the Ramsar Site, given the lack of records and confirmed absence from one site in this area (Fjeldså et al. 2021). To the north there are confirmed records to the Great Ruaha river (eBird 2022, GBIF.org 2022) and this is tentatively considered the edge of the range. One record further north in Mikumi National Park (Kaestner 1998) may not be precisely located and it is uncertain if it regularly occurs in this area, which is slightly lower than the elevation limits (240-305 m) given in Fjeldså et al. (2021). Excluding areas north of the Great Ruaha river, the current extent of occurrence (EOO) is estimated at 7,800 km2.
There is no estimate of the area of occupancy within this EOO, given the uncertainty over this species' strict habitat requirements. While this extent is uncertain, the ongoing rate of conversion of habitat estimated from within the range (Leemhuis et al. 2017, Wilson et al. 2017, Msofe et al. 2019) is inferred to be causing a continuing decline in the area and quality of habitat.
White-tailed Cisticola is reported to be the commonest cisticola within the Kilombero Floodplain, occurring in similar areas to C. bakerorum but apparently in a wider range of typically drier, more open habitats and in shorter vegetation (Fjeldså et al. 2021). All records fall within the same elevational range as C. bakerorum, between 240-305 m asl. (Fjeldså et al. 2021). Observations have been made of the species running on the ground in the manner of a pipit Anthus spp. (Fjeldså et al. 2021). Rannestad et al. (2015) record highest densities in reed and grass-bush habitat, but the species was also recorded in stands of makongo (Persicaria senegalensis) and on sand islands. No seasonal movements have been reported, but densities vary in different habitats through the year (Rannestad et al. 2015).
Within the Kilombero valley there has been rapid conversion of wetland habitat in the floodplain to agricultural use over the past three decades (Wilson et al. 2017, Proswitz et al. 2021). However, it is unclear as to the extent to which these changes have impacted populations of the species, despite their considerable extent. It is assumed that the loss of natural vegetation has impacted the population of the species, although the observation that it occurs in areas degraded by grazing in conjunction with a preference for slightly drier habitats suggests that the impacts will be less severe than for C. bakerorum. Even so, the area of wetland/grassland is estimated to have decreased by 33% between 1991 and 2016, at a rate that appears to be accelerating (Wilson et al. 2017, Proswitz et al. 2021). The human population of the Kilombero valley has been increasing rapidly since the start of the 21st century, predicted to result in the measured rate of wetland loss at least continuing or more likely accelerating over the next decade unless complex interacting drivers are countered (Proswitz et al. 2021). Loss of wetland to agricultural use has come from large businesses purchasing land for irrigated crops, particularly rice, and the expansion of the area farmed by small-holders across the wetlands, including a rapid increase in pastoralists and cattle prior to a forced relocation by the government in 2012 (Nindi et al. 2014).
Further threats come from the control of water upstream of the Kilombero basin. There were two hydropower generation schemes operating in 2017 with more hydropower projects planned for the upstream Kilombero basin (Ministry of Natural Resources and Tourism 2018). An assessment of the current hydrology of the Kilombero River mainstem and the tributaries showed largely unaltered flow regimes and ecological functioning, abstraction and regime modifications, but identified significant risks that the condition would decline and that an analysis of current irrigation plans threaten to reduce dry-season flows to below target sustainable levels (Ministry of Natural Resources and Tourism 2018). Additional irrigation is likely with the continuing increase in the human population within the floodplain, such that a considerable proportion of the flooded grassland area on which the species depends may dry out in future dry seasons. However, the extent to which the species depends on the extent of flooding of vegetation is uncertain, given the reported use of much drier habitats than C. bakerorum.
Conservation actions in place
The majority of the species' range lies within the Kilombero Valley Ramsar Site, designated in 2002 and covering 7,967 km2 (RIS 2002, Finlayson et al. 2016, Wilson et al. 2017). It is also an Important Bird Area (Fishpool and Evans 1998, Baker and Baker 2002) and with the recognition of this species and C. bakerorum now meets the criteria for an Endemic Bird Area (Stattersfield et al. 1998). Conservation actions are a key element to the most recent Integrated Management Plan (Ministry for Natural Resources and Tourism 2018), within which this species is mentioned as a part of the qualifying criteria, albeit as one of two undescribed cisticola species. The plan contains recommendations to address concerns highlighted by an earlier Ramsar Advisory Mission report (Wilson et al. 2017), but the extent to which these have been subsequently implemented is unclear. There has been considerable research into the human pressure within the Kilombero Valley and the impact on the condition of the natural habitat and species (e.g. see Proswitz et al. [2021] for the complex drivers of environmental change in the valley).
Conservation actions needed
The key challenge is to retain sufficient suitable natural vegetation within an area subject to high pressure for agricultural conversion. It remains necessary to establish clear agreed conservation zones within the Ramsar Site where sufficient habitat can persist, noting that it is a dynamic landscape. Monitoring to assess the reduction in extent of apparently suitable habitat should continue as part of the implementation of the Integrated Management Plan, and this should also include effort to monitor distribution and abundance of this and the other two bird species endemic to the area. The extent to which the species can persist in human-altered wetland areas is unknown: it is suggested that the species has fairly general habitat requirements and may be less affected than Kilombero Cisticola by conversion to agriculture. In order to monitor rates of habitat loss it would be helpful to more accurately determine the species' habitat requirements.
12.1 cm. A streak-backed marsh cisticola with a prominent white supercillium and extensive bright white tips to the tail feathers, except the central pair. Generally the plumage is dull grey-brown, and buffy underneath. The song is distinctive, with repeated phrases of two or three notes at varying pitches: it also occasionally gives a half-second long 'winding' trill.
Text account compilers
Martin, R.
Recommended citation
BirdLife International (2024) Species factsheet: White-tailed Cisticola Cisticola anderseni. Downloaded from
https://datazone.birdlife.org/species/factsheet/white-tailed-cisticola-cisticola-anderseni on 01/12/2024.
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 01/12/2024.