Brown-cheeked Bulbul (Alophoixus bres): request for information

Brown-cheeked Bulbul Alophoixus bres (BirdLife International species factsheet) was split from Grey-cheeked Bulbul A. tephronogenys in 2016. The species is restricted to Java and Bali, Indonesia, and inhabits primary and secondary lowland forest. A recent analysis assigned the species a very high risk of extinction on the basis of expert opinion on trapping intensity in Indonesia in combination with estimates of habitat loss since 2000 (Symes et al. 2018). The hunting impact was predicted to be exceptionally high (99.8%), suggesting that Brown-cheeked Bulbul would be all but wiped out by trapping within a 10-year period. Habitat loss was not considered to impact this species.

Eaton et al. (2015) drew attention to the concern that in Kalimantan, the pre-split species was seen as a ‘substitute’ for the exceptionally popular Straw-headed Bulbul Pycnonotus zeylanicus (now Critically Endangered due to exceptionally rapid population decline over almost its entire range) and could be expected to decline rapidly. However, surveys in heavily-trapped forest in south Sumatra recorded that Grey-cheeked Bulbul actually significantly increased in abundance between 1998 and 2011 (Harris et al. 2017). Nevertheless, the volume of trade also dramatically increased, in line with a greater than six-fold increase in the price demanded (Harris et al. 2015).   

Brown-cheeked Bulbul is being traded in high numbers on Java. Chng et al. (2015) recorded 212 individuals from 38 shops across three markets in Jakarta in three days in 2014; 111 individuals were recorded from central and eastern Java in three days in 2015 (Chng and Eaton 2016), and 22 individuals were for sale in Bandung in September 2016 (Chng et al. 2016). No price information is given for this species in the market inventories (Chng et al. 2015, Chng and Eaton 2016, Chng et al. 2016).

The major issue is a dearth of information on the wild population of this species. Within the last ten years, it has been recorded at remaining forested sites scattered across Java (all considered accessible to trappers), and in several locations on Bali (eBird 2019). From the numbers recorded in trade, a continuing population decline can be suspected within the species’s range due to exploitation. However, some further information is required to judge the rate of this decline. At present, there is insufficient evidence to suspect a decline that exceeds the threshold for listing at Vulnerable (>30% decline in 10 years), but the apparent persistence at locations throughout the range may mask considerable reductions in abundance. It is difficult to reconcile even this scant information with the analysis within Symes et al. (2018): if these data were accurate, multiple local extirpations would be occurring. Is there evidence for this?

Criterion A – Here, it is proposed that the species be listed as Near Threatened under Criteria A2d+3d+4d, on the assumption that there is at least a moderately rapid decline occurring. Further detail on the basis for the suspected very rapid decline could allow for assessment at a threatened category.  

Criterion B – The species exceeds the range size thresholds hence is assessed as Least Concern under Criterion B.

Criteria C and D – There is no population estimate for the species, and it is not possible to derive one from an extrapolation of a density estimate where trapping may or may not have greatly suppressed the abundance. Hence the species cannot presently be assessed under Criteria C and D.

Criterion E – To the best of our knowledge no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.

Therefore, it appears that the only criteria where the species might approach or meet the threshold for Vulnerable are A2d+3d+4d. To better assess the species against these criteria, we urgently request up-to-date information regarding the suspected or inferred rate of decline of Brown-cheeked Bulbul.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of its Red List status. Therefore, please make sure your comments are relevant to the discussion outlined in the topic.

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.

References

Chng, S.C.L., Eaton, J.A., Krishnasamy, K., Shepherd, C.R. and Nijman, V. (2015) In the Market for Extinction: An inventory of Jakarta’s bird markets. TRAFFIC. Petaling Jaya, Selangor, Malaysia.

Chng, S.C. and Eaton, J.A., 2016. In the market for extinction: eastern and central Java. TRAFFIC Southeast Asia.

Chng, S.C., Guciano, M.A., Eaton, J.A. 2016. In the market for extinction: Sukahaji, Bandung, Java, Indonesia. Bird. Asia. 26: 22-28.

Eaton, J. A., Shepherd, C. R., Rheindt, F. E., Harris, J. B. C., van Balen, S., Wilcove, D. S., & Collar, N. J. (2015). Trade-driven extinctions and near-extinctions of avian taxa in Sundaic Indonesia. Forktail, (31), 1-12.

eBird. 2019. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, N. Y., U.S.A. http://www.ebird.org. (Accessed 22/05/2019)

Harris, J.B.C., Green, J.M., Prawiradilaga, D.M., Giam, X., Hikmatullah, D., Putra, C.A. and Wilcove, D.S. (2015). Using market data and expert opinion to identify overexploited species in the wild bird trade. Biological Conservation 187: 51-60.

Harris, J.B.C., Tingley, M.W., Hua, F., Yong, D.L., Adeney, J.M., Lee, T.M., Marthy, W., Prawiradilaga, D.M., Sekercioglu, C.H., Winarni, N. and Wilcove, D.S. (2017). Measuring the impact of the pet trade on Indonesian birds. Conservation Biology 31(2): 394-405.

Symes, W. S., Edwards, D. P., Miettinen, J., Rheindt, F. E., & Carrasco, L. R. (2018). Combined impacts of deforestation and wildlife trade on tropical biodiversity are severely underestimated. Nature communications 9(1): 4052.

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