Data Zone
Justification of Red List category
A poorly known species endemic to Viet Nam and (where it has only recently been discovered) Lao PDR. It remains locally common in some areas it is found, and large areas of its range remain unexplored. Within its range forest cover is being lost at a moderately rapid rate and the species is therefore precautionarily listed as Near Threatened.
Population justification
The population size of this species has never been estimated. On the Dalat Plateau, Viet Nam, it is evidently highly localised (Eames et al. 1995, Mahood and Eames 2012, eBird 2023) with no obvious correlating habitat variables between confirmed sites to enable even a crude estimation of what percentage of its mapped range might be occupied. In the Mang Den region (Kon Tum province, Viet Nam) it appears to be more (at least locally) abundant (Wheatley 2015); while here it is confirmed from only a relatively small area, the total area of suitable habitat is considerably larger (and very poorly explored). The species' recent discovery in Dong Ampham, Lao PDR (Berryman 2023) [approximately 100 km north-west], in habitat broadly identical to that the species is found in Mang Den (A. Berryman pers. obs) supports suggestion that the species is probably more widespread in this section of the Annamites, although may remain very localised.
Given the great uncertainty over this species' true distribution (or, more accurately, great uncertainty about its habitat preferences and tolerances within it), the population size is here considered unknown. However, given the area of forest within the mapped range covers c.8,000km2 (and this may prove an underestimate), even if only a very small proportion of this is occupied (as seems probable), the population size is unlikely to be very small given its local abundance (e.g., approximately 40 birds encountered in a relatively small area of the Mang Den forests: Wheatley 2015).
Trend justification
Suspected to be declining in response to habitat loss and degradation. There is no direct evidence that the species is trapped for the cagebird trade (unlike its sole congener: Nijman et al. 2021).
Given uncertainties over this species' range, and abundance throughout it, determining plausible rates of decline is challenging. This difficulty is made only more acute by a lack of understanding of its habitat tolerances. At most occupied sites, it inhabits native forest that is either primary or only lightly degraded; however, at others (e.g. Ta Nung Valley, Da Lat), it persists in very degraded forests, while being inexplicably absent from surrounding, less modified, areas. Nonetheless, within its probable range, forest cover loss has occurred moderately rapidly in recent years, equivalent to rates of 8-27% over the past three generations (11 years: 2011-2022) with uncertainty principally driven by the difficulties in determining its range (Global Forest Watch 2023, based on data from Hansen et al. [2013] and methods disclosed therein). Translating this into plausible bounds of population decline introduces even greater uncertainty with respect to habitat modification tolerances. Possible rates of population decline are therefore set broadly, as between 5 and 29% over the past three generations, with a precautionary best estimate at the upper end of this (15-29%). Future rates of decline are set the same in the absence of any indication that forest cover loss has recently slowed.
The distribution of this species is not fully known, in part because its habitat requirements are so poorly understood and it is evidently highly localised. Historically it was known from only five specimens collected at two localities in 1938-1939, but was rediscovered in 1994 on the Da Lat Plateau, Viet Nam (Eames et al. 1995), to which it was for a long time assumed endemic. It was subsequently found at seven sites on the Da Lat Plateau (Mahood and Eames 2012), before its discovery at Mang Den, Kon Tum province (Viet Nam) 250 km north of Da Lat (Wheatley 2015). Both populations in Viet Nam continue to be observed regularly (eBird 2023). Somewhat unexpectedly, in December 2022 the species was discovered in Dong Ampham, Lao PDR (Berryman 2023), raising the question of whether it might yet prove more widely distributed in the Annamites.
Habitat needs poorly understood. On the Da Lat plateau, it occurs in some heavily degraded forest sites, such as Ta Nung Valley, but otherwise is typically found in closed-canopy forest (Mahood and Eames 2012, eBird 2023). At Mang Den (Kon Tum, Viet Nam) and at Dong Ampham (Lao PDR) it has been found in lightly degraded forests (Berryman 2023). Observations of this species have been made between 900 and 1,700 m, although most records appear confined to 900-1,200 m. Generally encountered in singles, pairs, and occasionally small groups of up to five, it is arboreal and forages with mixed-species flocks for invertebrates, particularly caterpillars, primarily in the outer canopy of broadleaved evergreen and coniferous trees (Hill et al. 2001).
The main threat identified for this species is forest loss. Remote sensing data (Hansen et al. 2013, Global Forest Watch 2023) indicate that this may be causing moderately rapid population declines, although there is great uncertainty regarding this species' tolerances. The causes of these losses is generally shifting agriculture and plantations. At Dong Ampham, Lao PDR, gold mining was identified as a threat by Berryman (2023), but this is likely to be highly localised and driving only negligible population declines. This species has never been recorded in trade, although may occasionally have been caught for the songbird trade in Viet Nam (other laughingthrush species are highly demanded). More research needed.
Conservation Actions Underway
None specific to this species is known, although it ostensibly benefits from protected areas within its range.
Conservation Actions Proposed
Conduct ecological studies to better determine its habitat needs and tolerances. Undertake more wide-ranging surveys within plausible areas of its range to understand its occupancy and range; in particular, determine if it occurs in Lao PDR away from Dong Ampham. Continue to monitor habitat trends in its range. Determine the extent to which, if at all, trapping is a threat to this species. Establish protected areas within areas of lowland forest this species is known to occupy.
22 cm. Slim babbler with slaty-grey crown, blackish mask and boldly blackish-streaked flanks. Dull rufous upperparts with blackish-brown streaks and faint, pale shaft streaks on crown, nape and mask. White rest of underparts. Mostly slaty-grey, white-tipped tail, mostly grey greater coverts and secondaries and white-fringed, blackish primaries. Juvenile has browner crown with broader buffish streaks, duller head-sides, smaller flank-streaks, browner greater coverts and secondaries and narrower, white tail feather tips. Voice Song is loud wip'ip'ip-wiu-wiu-wiu-wiu-wiu-wiu-wiu (usually 7-8 wiu notes). Hints Listen for song in montane forest.
Text account compilers
Berryman, A.
Contributors
Mahood, S., Wheatley, T. & Davidson, P.
Recommended citation
BirdLife International (2024) Species factsheet: Grey-crowned Crocias Laniellus langbianis. Downloaded from
https://datazone.birdlife.org/species/factsheet/grey-crowned-crocias-laniellus-langbianis on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/12/2024.