Grey-breasted Babbler (Malacopteron albogulare) is found in lowland forest habitats (particularly peatswamp and heath forest on alluvial plains) in Peninsular Malaysia as well as the islands of Sumatra and Borneo. Habitat loss is considered to be the primary threat to this species, with land conversion, logging and forest fires all taking their toll on its forest habitats. As such the species has been considered to be undergoing a moderately rapid decline, and has been listed as Near Threatened under criteria A2c+3c+4c (see BirdLife International 2017).
The species is considered to be scarce (del Hoyo et al. 2007) and it is encountered only rarely, with most records coming from Borneo (see Yong et al. 2014). It could be that the lack of records for this species is due to its behaviour, as mist netting has often shown it to be more common than previously believed (again see Yong et al. 2014 for a summary). However, there have been few recent records from areas of suitable habitat (D. L. Yong in litt. 2007) and it has disappeared from several sites where it had been previously known (Yong et al. 2014). Additionally, the Grey-breasted Babbler is considered to react strongly to playback yet survey work in the early 2010s only found the species at two sites (D. Bakewell in litt. 2013). It has been suggested that the species may warrant reassessment to see whether it may merit uplisting to Vulnerable (Yong et al. 2014), and so the species has been reassessed here against all criteria.
Criterion A – Data from Tracewski et al. (2016) suggests that forest loss within the species’ range has been at a rate of 16.2% over 3 generations (14.4 years). If it is therefore assumed that population declines are at a similar rate to forest loss then the species would no longer be considered to be approaching the threshold for Vulnerable under this criterion (30% decline over 3 generations) and so it would no longer warrant listing under criterion A.
Criterion B – The species’ range is too large (Extent of Occurrence = 1,900,000km2; Area of Occupancy not directly calculated, but likely >>2,000km2) to qualify for listing under this criterion.
Criterion C – There is no clear data to accurately estimate the global population of this species, but given the very low reporting rates it is plausible that the population size could be <10,000 mature individuals. However, mist netting has found the species to be more common than previously thought in some areas and reported population densities are c.21-22 individuals per km2 (Dutson et al. 1991, Wilkinson et al. 1991). The sparse and scattered reporting of the species could mean that it may persist in only very small pockets throughout its range and without further information the population size is in effect unknown, although potentially very small.
If there were such information available to show that the population size is <10,000 mature individuals, for the species to be listed as Vulnerable under criterion C it would need to meet other conditions, which are laid out below (see also IUCN 2001, 2012).
C1 – To be listed under this criterion it must be undergoing an ‘observed’, ‘estimated’ or ‘projected’ continuing decline over 3 generations or 10 years of 10%. Data from Tracewski et al. (2016) suggests that habitat loss is occurring at 16.2% over 3 generations. However, while we can ‘infer’ a continuing decline from this we can only at best ‘suspect’ a decline at this rate (see IUCN Standards and Petitions Subcommittee 2017), and given that this criterion requires a high level of data confidence, the species would not meet this conditions for listing under criterion C1. However, it could warrant listing as Near Threatened under this criterion.
C2a(i) – To be listed under this criterion, the largest subpopulation must contain ≤1,000 mature individuals. Given the high level of uncertainty over the global population estimate, it is equally as difficult to accurately estimate the size of individual subpopulations. Therefore, there is insufficient evidence to warrant the species being listed under this criterion, although further information regarding population and subpopulation estimates may mean it meets the threshold for listing under this criterion.
C2a(ii) – 100% of the population would need to be found in one subpopulation for the species to be listed under this criterion. This is unlikely to be the case and so the species would not warrant listing under this criterion.
C2b – To be listed under this criterion the species would need to undergo extreme fluctuations. There is no evidence of this and so the species cannot be listed under this criterion.
Overall, therefore, the lack of clear knowledge of population and subpopulation sizes in this species mean that we cannot accurately compare it to the thresholds and conditions for listing under criterion C. Given the current information the species may warrant listing as Near Threatened under criterion C1, but further information regarding population and subpopulation sizes is urgently required for a clearer assessment.
Criterion D – The population size and range of this species are likely to be too large to warrant listing under this criterion.
Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been carried out for this species. Therefore, it cannot be assessed against this criterion.
Therefore, further information is sought regarding the overall population size, and the likely size of different subpopulations of the species. In the absence of this information the species could remain as Near Threatened, but under criterion C1 rather A2c+3c+4c; although even this may require further information.
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 discussion outlined in the topic.
BirdLife International. 2017. Species factsheet: Malacopteron albogulare. Downloaded from http://www.birdlife.org on 27/11/2017.
del Hoyo, J.; Elliott, A.; Christie, D. 2007. Handbook of the Birds of the World, vol. 12: Picathartes to Tits and Chickadees. Barcelona, Spain: Lynx Edicions.
Dutson, G.; Wilkinson, R.; Sheldon, B. 1991. Hook-billed Bulbul Setornis criniger and Grey-breasted Babbler Malacopteron albogulare at Barito Ulu, Kalimantan. Forktail 6: 78-82.
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. Available at: www.iucnredlist.org/technical-documents/categories-and-criteria.
IUCN Standards and Petitions Subcommittee. 2017. Guidelines for Using the IUCN Red List Categories and Criteria. Version 13. Prepared by the Standards and Petitions Subcommittee. Downloadable from 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.
Wilkinson, R.; Dutson, G.; Sheldon, B. 1991. The Avifauna of Barito Ulu, Central Borneo with additional notes on the mammals. ICBP Study Report No. 48. Cambridge: ICBP.
Yong, D. L.; Lim, K. C.; Eaton, J. A.; Tan, K. H.; Lau, W. T.; Foley, C. 2014. The Grey-breasted Babbler Malacopteron albogulare, a poorly known Sundaic species. BirdingASIA 21: 71-75.