Archived 2012-2013 topics: Black-throated Babbler (Stachyris nigricollis) and Fluffy-backed Tit-babbler (Macronous ptilosus): downlist both to Least Concern?

This discussion was first published as part of the 2012 Red List update, but remains open for comment to enable reassessment in 2013. BirdLife species factsheets for Black-throated Babbler and Fluffy-backed Tit-babbler Black-throated Babbler Stachyris nigricollis and Fluffy-backed Tit-babbler Macronous ptilosus both have very large but disjunct ranges in the Thai-Malay Peninsula, Sumatra and Borneo. S. nigricollis is described as a resident of primary and secondary evergreen forests, overgrown plantations, edge habitats and scrub, whereas M. ptilosus is said to inhabit evergreen forest, including selectively logged areas, secondary growth and bamboo stands. They are both listed as Near Threatened under criterion A on the basis that they are suspected to be undergoing a population decline of 1-19% over 10 years owing to on-going habitat loss and degradation driven by timber extraction, habitat conversion and forest fires. These species’ listing as Near Threatened, based on their suspected rate of decline, may not be tenable given their ability to persist in human-altered habitats. Species listed as Near Threatened under criterion A are usually undergoing declines estimated to approach a rate of 30% over three generations or 10 years (typically 20-29% over this time period). Both S. nigricollis and M. ptilosus have been listed as Near Threatened as a precautionary measure, but their habitat requirements suggest that they should both be downlisted to Least Concern on the basis that they are no longer considered to approach the thresholds for Vulnerable under any of the IUCN criteria. Comments are invited on these proposed category changes and additional information is sought, including estimates of the rates of population decline over a period of 11-12 years (estimate of three generations) and details of the species’ habitat requirements and the severity of threats.

Related posts:

  1. Archived 2011-2012 topics: Nonggang Babbler (Stachyris nonggangensis): uplist to Vulnerable?
  2. Archived 2011-2012 topics: Short-tailed Scimitar-babbler (Jabouilleia danjoui): downlist to Least Concern?
  3. Archived 2010-2011 topics: White-throated Wren-babbler (Rimator pasquieri): uplist to Endangered?
  4. Archived 2010-2011 topics: Pale-throated Wren-babbler (Spelaeornis kinneari): uplist to Vulnerable?
  5. Archived 2010-2011 topics: Grey-backed Tachuri (Polystictus superciliaris): downlist to Least Concern?
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3 Responses to Archived 2012-2013 topics: Black-throated Babbler (Stachyris nigricollis) and Fluffy-backed Tit-babbler (Macronous ptilosus): downlist both to Least Concern?

  1. Ding Li Yong says:

    “Ability to persist in human-altered habitats”must be carefully considered species. Both species certainly can persist in lightly to moderately logged forests, but based on the evidence from observations across the region, heavily disturbed secondary forests and scrubs do not contain the species. Peh et al. (2006) studied degraded lands including plantations and scrub in southern peninsular Malaysia and failed to find the species despite long term sampling and indicates that the species may not actually persist well in human-disturbed like plantations and scrub.

    The evidence from Singapore (see Castellata et al. 2000) shows that both are unable to persist in secondary forest fragments long term. Both species are extinct from Singapore’s forest for more than four decades at least and suggest that while they may persist short term in secondary forests and plantations, these are suboptimal habitats and the remnant populations eventually die out. Similarly, a sampling of land bridge island forest fragments in northern peninsular Malaysia may have found both species on contiguous forest sites, but failed to find both on small island fragments of less than 200 ha again highlight vulnerability of both species to extinction. Edwards et al. (2010) found both in logged forests, which shows that they may show some level of tolerance to disturbance, but again requires fairly intact forest habitats. The rapid loss of even lowland logged and disturbed forests in South-east Asia, especially in Sumatra and many parts of Kalimantan means that even secondary habitats remain vulnerable to future loss. Posa (2011) failed to find both species in degraded peat swamp forest. Given that both species are predominantly babblers of lowland forests, this means both remain at risk.

    In Panti forest reserve, I found both species to be relatively common in logged forests, and are easily seen near forest edges, but absent from heavily disturbed areas, or adjacent areas of plantation, imply inability to persist once habitat has been heavily degraded. In Taman Negara and the Lake Kenyir basin, long term visits and sampling found both species to be moderately common in lowland forest and uncommon to rare in hilly forest. Forest fragments in Lake Kenyir do not contain both species even after many weeks of sampling. In the Ampang Forest Reserve which is mostly on hilly terrain, both species remains relatively uncommon, compared to other babbler species.

    Suggest keeping both species as near-threatened, given sensitivity to habitat disturbance, and from the data from a variety of sources across the region.

    References
    Castelleta et al (2000). Conservation Biology 14: 1870 – 1880
    Edwards et al. (2010). Proceedings of the Royal Society B (doi: 10.1098/rspb.2010.1062)
    Peh et al. (2006) Diversity and Distributions 12: 572 – 581.
    Posa (2011) Biological Conservation 144: 2548 – 2556.
    Yong et al. (2011) Journal of Tropical Ecology 27: 1 – 14.

  2. Joe Taylor says:

    The following comments were sent by Will Duckworth on 24 November 2011:

    I can only comment on the status in relation to Similajau National Park, Sarawak. Here, the tit babbler is abundant in scrub (over former clearfell) to the south of the park. This is several miles from the nearest ‘forest’, which comprises, however, about 30 sq km of almost untouched lowland forest and 2-3 x that area of degraded forest. Perhaps the birds are dispersing into the scrub from there. I don’t know the calls of Black-throated Babbler so don’t know if it is similarly distributed.

  3. Philip Round says:

    I completely fail to understand why two species which are largely restricted to extreme lowlands throughout their ranges should be considered for downlisting, especially given the continuing huge scale of unregulated conversion of forest land in (e.g.) Indonesia. Granted, my experience of both species is largely based on a small part of their global range (peninsular Thailand), where both are now extremely scarce and local, and where there are scarcely any habitat patches large enough to support either away from the immediate margins of perilously few protected areas). Isn’t it likely that a similar scenario will be repeated in Malaysia and Indonesia, where continued expansion/intensification of oil-palm and other cultivation will threaten to scrape the last vestiges of lowland vegetation from most of the land surface? I would recommend retaining both Fluffy-backed Tit Babbler and Black-throated Babbler as (at least) near-threatened, unless there is compelling evidence otherwise.

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