Malaysian Whistling-thrush Myophonus robinsoni is currently listed as Least Concern because although it has a small range it was not previously believed to approach the thresholds for Vulnerable under any of the IUCN criteria.
Recently, a study was carried out on whistling-thrushes Myophonus spp. in Peninsular Malaysia by Bakewell et al. (2010, in prep.). Surveys undertaken for this study did not locate M. robinsoni in the Cameron Highlands, calling into question the reliability of relatively recent sight records from that area, although there are indisputable records of trapped birds from the 1950s and 1960s. Indeed, in the latest study the species was recorded at only one of the surveyed locations, Fraser’s Hill. The same recent surveys confirmed that the dicrorhynchus race of Blue Whistling-thrush M. caeruleus occurs in montane areas, an aspect of its distribution over which there was uncertainty following much earlier observations, and which may have contributed to erroneous records of M. robinsoni, owing to poorly understood diagnostic criteria (Bakewell et al. 2010, Bakewell et al. in prep.). The study by Bakewell et al. (2010, in prep.) has allowed BirdLife to map the range of M. robinsoni with greater confidence. The revised EOO estimate for the species is 4,400 km2 (calculated from the area over which the species is considered to be extant or probably extant), based on the results of recent surveys, as well as past records.
Updated BirdLife range map for Malaysian Whistling-thrush
A further implication arising from the frequent misidentification of M. c. dicrorhynchus in montane areas is that the population of M. robinsoni, which is currently estimated at 10,000-19,000 individuals by BirdLife, may actually be smaller than previously thought, with Bakewell et al. (2010) finding no evidence against Collar’s (2005) presumption that there are fewer than 10,000 mature individuals, in the absence of better knowledge.
Suitable areas for M. robinsoni, primarily in the Cameron and Genting Highlands and at Fraser’s Hill, continue to be threatened by habitat degradation caused through sedimentation and pollution of waterways – largely as a result of infrastructure development, pesticide run-off and fly-tipping of waste, land clearance and tree-felling for agriculture and construction, the introduction of non-native species and the local climatic effects of overdevelopment and vegetation removal (Yeap et al. 2007, Bakewell et al. 2010, Bakewell et al. in prep.). However, the majority of habitat in the Titwangsa Range remains largely undisturbed (D. Bakewell in litt. 2010). The threatening processes that are affecting areas of its habitat are suspected to be driving ongoing local declines in the population of M. robinsoni. Although it is suspected to be declining and the range and population size estimates meet the thresholds for Endangered under the B criterion and Vulnerable under the C criterion, the species does not qualify for these categories because its population is not considered to be severely fragmented and there is insufficient information available to ascertain its sub-population structure – specifically whether all sub-populations number 1,000 individuals or less, or if all individuals are in one sub-population.
It is therefore proposed that the species be uplisted to Near Threatened under criteria B1a+b(i,ii,iii,v); C2a(i,ii). Comments on this proposed category change would be welcomed and further information on the species is requested.
Bakewell, D. N., Lim, K. C. and Shahrul, A. M. S. (2010) A preliminary assessment of the field identification, status, distribution and population of regionally endemic whistling-thrush taxa in Peninsular Malaysia. Report on a survey funded by the Tan Kean Cheong Bird Conservation Memorial Fund.
Bakewell, D. N., Lim, K.C., Shahrul, A. M. S. and Muin, M. A. (in prep.) Malaysian Whistling-thrush Myophonus robinsoni – Field Identification, Distribution and Conservation Concerns. BirdingASIA.
Collar, N. J. (2005) Family Turdidae (Thrushes), in del Hoyo, J., Elliott, A. and Christie, D. A. eds. Handbook of the Birds of the World, Vol 10. Cuckoo-shrikes to Thrushes. Barcelona : Lynx Edicions. Pp 714–715.
Yeap , C. A., Sebastian, A. C. and Davison, G. W. H. (2007) Directory of Important Bird Areas in Malaysia : key sites for conservation. Kuala Lumpur : Malaysian Nature Society (MNS Conservation Publication No.8).