BirdLife International factsheet for Gola Malimbe.
This discussion was first published as part of the 2020 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2021 Red List update this post remains open and the date of posting has been updated.
The Gola Malimbe (Malimbus ballmanni) is found in Africa, with a range that encompasses Sierra Leone, Guinea, Côte d’Ivoire, and Liberia. It inhabits lowland primary forest, lightly logged high forest, and very old secondary forest (BirdLife International, 2020).
The population size is estimated to 10,000-19,999 individuals, equating to 6,667-13,333 mature individuals. The population in Liberia’s Sapo National Park has recently been estimated at roughly 22,000 individuals (Freeman et al. 2018). Extrapolated data for the total population must be treated with caution as the species appears to be very rare and localised in the western part of its range (J. Lindsell in litt., 2007). Therefore, the overall population estimate remains at 10,000-19,999 individuals, but further surveys of other populations may alter this estimate in the future.
The only known threat to this species appears to be habitat loss and degradation resulting from commercial and illegal logging (Anon. 2000, via BirdLife International, 2020), and deforestation for agricultural and mining activities (Freeman et al., 2018).
Gola Malimbe has previously been considered Endangered under criterion A2c+3c+4c. However, recent data regarding the rate of forest loss may mean that this is no longer tenable and the species may warrant a change in Red List status. Gola Malimbe has therefore been reassessed here against all the criteria.
Criterion A: The population trend for this species has not been directly estimated. However, the only known threat for this species is habitat loss and degradation. Between 2000-2018, there was an estimated 7.4% reduction in tree cover across this species’s range (Global Forest Watch, 2020). IUCN guidelines stipulate that rates of decline should be measured over the longer of 10 years or 3 generations (IUCN Standards and Petitions Committee, 2019). The generation length for Gola Malimbe has been recalculated to 3.3 years (Bird et al., 2020)*. Therefore, the rates of reduction for this species are calculated over 10 years.
Assuming that the population size declines at the same rate as habitat loss, this equates to a 4.2% reduction over the last 10 years. Additionally, Tracewski et al. (2016) found negligible levels of deforestation in their analysis. A 10-year reduction rate of 4.2% is too low to trigger the threatened category (≥30% population size reduction) under this criterion. Gola Malimbe may therefore be considered Least Concern under criterion A.
Criterion B: The Extent of Occurrence (EOO) for this species is calculated to be 75,300 km². This is too high to trigger the threatened threshold (EOO <20,000 km²). Gola Malimbe may therefore be considered Least Concern under criterion B1. The Area of Occupancy (AOO) has not been quantified following IUCN Guidelines (IUCN Standards and Petitions Committee 2019), and therefore the species cannot be assessed against criterion B2.
Criterion C: The population size is estimated to be 6,667-13,333 mature individuals. Assuming that the true population is closer to the lower end of the estimate, this meets the threshold for Vulnerable (<10,000 mature individuals). However, in order to fully qualify as threatened under this criterion, other sub-criteria must be met. A continuing decline can be inferred from the continuing habitat loss. The number of subpopulations for this species is estimated to be 2-100, which precludes the criterion that all individuals are in one subpopulation. The rest of the subpopulation structure is unknown, and this species is not believed to experience any extreme fluctuations. As such, Gola Malimbe does not fully meet the requirements for classification as threatened here, and may therefore be considered Least Concern under criterion C.
Criterion D: The population size is estimated to be 6,667-13,333 mature individuals. This is too high to trigger the threatened threshold under this criterion (<1000 mature individuals). Gola Malimbe may therefore be considered Least Concern under criterion D.
Criterion E: To the best of our knowledge, no quantitative analysis has been carried out for this species. We therefore cannot assess Gola Malimbe against criterion E.
We therefore suggest that Gola Malimbe (Malimbus ballmanni) be listed as Least Concern. We welcome any comments to the proposed listing.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status and the information requested. By submitting a comment, you confirm that you agree to the Comment Policy.
*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
Bird, J. P.; Martin, R.; Akçakaya, H. R.; Gilroy, J.; Burfield, I. J.; Garnett, S.; Symes, A.; Taylor, J.; Šekercioğlu, Ç.; Butchart, S. H. M. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.
BirdLife International (2020) Species factsheet: Malimbus ballmani. Downloaded from http://www.BirdLife.org on 12/05/2020
Benedictus Freeman, Filibus Danjuma Dami & Mary Molokwu-Odozi (2018): Status of globally threatened birds of Sapo National Park, Liberia, Ostrich, DOI: 10.2989/00306525.2018.1502694
Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 13 May 2020).
IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categories and Criteria. Version 14. http://www.iucnredlist.org/documents/RedListGuidelines.pdf
Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.