VU
Slender-billed Babbler Chatarrhaea longirostris



Justification

Justification of Red List Category
This elusive species is thought to have a small, fragmented population which is declining as a result of the extensive destruction and degradation of its tall grassland habitats. It therefore qualifies as Vulnerable.

Population justification
The population is estimated to number 2,500-9,999 individuals, based on a detailed analysis of historical and recent records in BirdLife International (2001). This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. The estimate equates to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals. The largest remaining population, in Chitwan National Park, is estimated to number 1,400-2,200 individuals (Baral and Chaudhary 2006, Inskipp et al. 2016), but there have been few recent surveys elsewhere in its range and the population in Kaziranga National Park could well be larger than the Chitwan population when the extent of available habitat and frequency of sightings are considered (A. Choudhury in litt. 2016). A survey in 2015 failed to find the species on any island or in any floodplain grassland outside protected areas (A. Rahmani in litt. 2016).

Trend justification
Recent information on population trends is lacking, but on-going habitat loss and degradation across the species's range suggest that a rapid population decline is likely to be continuing.

Distribution and population

This species has a fragmented distribution in the terai of central Nepal and north and north-east India (BirdLife International 2001). Although described as locally common in the 19th century, recent records come from just three areas, in Nepal (where it is locally fairly common, but known from only one locality - Chitwan National Park and in some community managed forests/grasslands in the park buffer zone [H. Baral and C. Inskipp in litt. 2016]). In India it is known from Kaziranga National Park, Orang National Park, Manas National Park, Dibru-Saikhowa National Park, Keibul Lamjao National Park and possibly D'Ering Sanctuary (A. Choudhury in litt. 2016, A. Rahmani in litt. 2016). Its declining population is estimated at 1,440-2,160 individuals, based on surveys in 2005 [Baral and Chaudhary 2006]), at Gorumara NP in Bengal (M. Prince in litt. 2002, P. Lobo in litt. 2003), and also in Assam. There are unconfirmed historical reports from Bangladesh and Myanmar. A survey in India in 2015 failed to find the species on any island or in any floodplain grassland outside protected areas (A. Rahmani in litt. 2016).

Ecology

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.

Threats

The rapid and extensive loss and modification of tall grasslands and reedswamp throughout its limited range is the main threat to the species. This is occurring 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's breeding period (A. Rahmani in litt. 2016). It is also threatened by the growth of invasive alien plant species such as Mikania micranthaMimosa 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).

Conservation actions

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 six protected areas, Chitwan National Park, Nepal and Kaziranga National Park, Manas National Park, Orang National Park, Dibru-Saikhowa National Park, Keibul Lamjao National Park, India (A. Choudhury in litt. 2016, A. Rahman in litt. 2016, A. Rahmani in litt. 2016). Chitwan, Kaziranga, Orang and Manas support good populations (A. Rahmani 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, A. Rahmani in litt. 2016). Survey suitable grassland reserves within the species's range for possible reintroductions (H. Baral and C. Inskipp in litt. 2016). 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).

Identification

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.

Acknowledgements

Text account compilers
Benstead, P., Gilroy, J., Taylor, J., Ashpole, J

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


Recommended citation
BirdLife International (2019) Species factsheet: Chatarrhaea longirostris. Downloaded from http://www.birdlife.org on 13/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/11/2019.