• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
Considered Vulnerable due to its restricted range; it occurs at only five sites (four in India, one in Nepal) which are highly fragmented and vulnerable to stochastic pressures and subject to ongoing habitat degradation. It is not currently considered more threatened because all, or nearly all, of its range is contained within protected areas.

Population justification
The population size of this species is not precisely known, but given it is confined to only five sites it is suspected to be relatively small. The largest (or second-largest) remaining population, in Chitwan National Park, was estimated to number 1,400-2,200 mature individuals (Baral and Chaudhary 2006, Inskipp et al. 2016). The population in Kaziranga National Park is likely to be a similar size (or possibly slightly larger) (A. Choudhury in litt. 2016). There has been no attempt to estimate the other three sites of occupancy, but the area of suitable habitat in each of them is smaller than Chitwan and Kaziranga. Accordingly, these three sites combined is thought to host approximately 1,400-4,400 mature individuals (the minimum bound being the minimum number at one of Kaziranga/Chitwan, the upper bound being double the upper bound of one of Kaziranga/Chitwan). Combined, the global population is estimated to number 4,200-8,800 mature individuals.

Trend justification
Suspected to be declining, albeit probably very slowly, in response to ongoing habitat pressures (Krishnan 2021). Populations are greatly fragmented, and while it is evident the species is able to persist short-term in isolated pockets of habitat, the viability of these in the long-term is unknown.

This species has a fragmented distribution, with records from only five areas (all protected) areas (Krishnan 2021). In Nepal, recent records from only Royal Chitwan National Park (BirdLife International 2001, eBird 2023). In India, known from four protected areas: (1) Manas National Park (Choudhury 2007, eBird 2023); (2) Kaziranga National Park (Barua and Sharma 1999, eBird 2023); (3) Rajiv Gandhi Orang National Park (Chakdar et al. 2019, eBird 2023); and (4) Keibul Lamjao National Park (eBird 2023). There are unsupported recent claims from elsewhere in north-east India but extensive surveys in 2015 failed to find the species on any island or in any floodplain grassland outside protected areas (A. Rahmani in litt. 2016). Claims from Bhutan, Bangladesh and Myanmar are all considered unconfirmed or erroneous (BirdLife International 2001, Rasmussen and Anderton 2012, eBird 2023).

It is a sedentary resident of tall grasslands in the lowlands, where it is usually found near water, and at least historically on grassy plateaux at 900-1,200 m in Meghalaya, India. In India it is thought to inhabit Saccharum sponteneum and Imperata cylindrica grassland however more work is needed to determine its exact habitat requirements (A. Rahmani in litt. 2016). In Nepal it is known to use Narenga porphyrocoma grassland (Baral and Chaudhary 2006). It is gregarious, but generally shy and difficult to observe, except during the breeding season, March-June, when it is more vocal and conspicuous.

The rapid and extensive loss and modification of tall grasslands and reedswamp throughout its range has been the principal cause of considerable declines in range (and axiomatically abundance) over the past century. To a much lesser extent, these declines are suspected to be still ongoing, as a result of drainage, conversion to agriculture (primarily rice-paddy, sugarcane, mustard and tea plantations), overgrazing by domestic livestock, over harvesting of grass for thatch production, untimely cutting and burning of grass, inappropriate grassland management within protected areas and heavy flooding in the Brahmaputra valley, as a result of run-off from an increasingly denuded catchment. Saccharum sponteneum and Imperata cylindrica grasslands are heavily exploited for materials for thatch and for grazing. These grasslands are burnt during the summer dry period to encourage new growth, however this period of burning also coincides with the species' breeding period (A. Rahmani in litt. 2016). It is also threatened by the growth of invasive alien plant species such as Mikania micrantha, Mimosa diplotricha and Bombax ceiba which can overrun grasslands and other habitats and render areas unsuitable (Baral and Chaudhary 2006, Inskipp et al. 2016, A. Rahman in litt. 2016). Dam construction within the species's range poses a threat to the species owing to changes in the flooding regime (A. Rahman in litt. 2016). As a grassland specialist and highly sedentary species and because of habitat fragmentation it is unlikely to recolonize new suitable areas unless assisted (H. Baral and C. Inskipp in litt. 2016). All of these threats have been greatly abated in recent years due to a broadly effective national park network.

Conservation Actions Underway
The species is listed as Critically Endangered under B2ab(iii) in Nepal (Inskipp et al. 2016). It is known to occur in at least five protected areas, Chitwan National Park, Nepal and Kaziranga National Park, Manas National Park, Orang National Park, Keibul Lamjao National Park, India (A. Choudhury in litt. 2016, A. Rahman in litt. 2016).

Conservation Actions Proposed
Conduct surveys in remaining suitable habitat throughout its range to establish its current distribution and population status and develop a monitoring scheme (A. Rahman in litt. 2016). Survey suitable grassland reserves within the species' range for possible reintroductions (H. Baral and C. Inskipp in litt. 2016), noting that natural (re)colonisation is now highly unlikely given how fragmented remaining populations now are. Extend, upgrade and link existing protected areas, and establish new ones, in order to adequately conserve remaining tracts of grassland. Control livestock-grazing in protected areas to reduce rates of tall grassland loss and degradation. Promote widespread conservation awareness initiatives focusing on grassland regeneration and sustainable management of grassland to maximise both thatch productivity for local people and available habitat for threatened grassland birds. Control alien invasive plant species and implement flood control measures in and around national parks (A. Rahman in litt. 2016). Develop an action plan for the species (A. Rahman in litt. 2016).

20-21 cm. Medium-sized, slim, brown babbler with slightly down-curved, blackish, slender bill and long tail. Dusky whitish lores and narrow eyebrow, whitish to bluish-white eyes, faintly cross-barred tail. Juvenile more rufescent above than adult, more rufescent-buff below and has pale basal half to lower mandible. Voice Song includes shrill, rather high yi chiwiyu chiwiyu'chiwiyu'chiwiyu'chiwiyu and clear high wiii-wii-jiu-di, wiii-wii-dju-di or wi-yu-ii. Also, four to six note chiu-chiu-chiu-chiu and discordant, high tiu-tiu-tiu, tit-tit and tiu-tiu-tit-tit-tu-tu. Hints Listen for song in wet or riverine grassland.

Text account compilers
Berryman, A.

Contributors
Baral, H.S., Inskipp, C., Lobo, P., Prince, M., Rahman, A., Choudhury, A.U. & Rahmani, A.

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Recommended citation
BirdLife International (2024) Species factsheet: Slender-billed Babbler Argya longirostris. Downloaded from https://datazone.birdlife.org/species/factsheet/slender-billed-babbler-argya-longirostris on 23/12/2024.
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 23/12/2024.