Status and distribution of the globally threatened Bristled Grassbird Chaetornis striata (Jerdon, 1841) (Fam. Sylviidae) in Nepal

Abstract

Lowland grasslands in Nepal were thoroughly surveyed in 1996-1999 to assess the status and distribution of the globally threatened Bristled Grassbird Chaetornis striata. Birds were located on foot, from elephants and from jeeps by sight and sound backed up by mistnets and tape playback. The status information was updated again by visiting these areas in 2010-2012. Bristled Grassbirds were recorded in Sukla Phanta and Koshi Tappu Wildlife Reserves, and Chitwan National Park where most of the Nepal population is confined. From the research, it was found that they were most associated with newly formed Saccharum and Imperata dominated grasslands during summer. The low numbers present during winter suggested that this species was primarily a summer migrant to Nepal. A total population for Nepal is presented based on a reliable density estimate. Loss and degradation of grassland habitat and invasion of Mikania micrantha were identified as the major threats. Further research on migratory status, better control of cattle grazing inside reserves, expansion of Protected Areas to include more grassland, and listing of Bristled Grassbird as protected under the wildlife law of Nepal for its conservation are highly recommended. DOI: http://dx.doi.org/10.3126/init.v5i0.10244 The Initiation 2013 Vol.5; 1-15

Population status, habitat preference and distribution of Bristled GrassbirdChaetornis striatain Bangladesh

“…As the survey sites were identified, point count stations were randomly spaced 500 m apart by placing the first point count station at a random starting point at a minimum 250 m from the edge of the river. Point count stations falling within habitats known to be unsuitable (disturbed grassland areas; Baral et al 2013, Singh and Buckingham 2015, Krishnan 2021 were not excluded from point counts in order to determine habitat preference of Bristled Grassbird in riverine floodplain grasslands.…”

“…The date of the counts can be a critical detection covariate due to change in behaviour of the target species as the breeding season progresses (Cornils et al 2015, Buckland et al 2016. The Bristled Grassbird is highly active during the early stage of the breeding season when the males perform breeding courtship displays by flying and calling and females respond (Baral et al 2013, Singh and Buckingham 2015, Krishnan 2021. Courtship behaviour declines over the course of the breeding season, thus affecting the detection probability (Buckland et al 2005, Thomas et al 2010.…”

“…Based on previous work on this (Singh and Buckingham 2015, Baral et al 2013, Khan et al 2015, Krishnan 2021 and related species such as the Striated Grassbird Megalurus palustris (Madge 2020), we recorded geographical and habitat variables that are known to influence Bristled Grassbird occurrence and abundance. Habitat variables such as distance to waterbodies (river, pool), bare sand, and human activities (agricultural interventions, livestock grazing, fire and grass harvesting) were recorded at each point count station.…”

“…This high density in Nepal could be because of unadjusted estimates and possible positive bias resulting from call playbacks, which led nearby Bristled Grassbirds into the counting plots that were rather small with short intervals between them (Thompson 2002, Buckland et al 2005. Baral et al (2013) estimated 10 birds per km 2 , which is 81.84 AE 33.34% lower than 54 AE 15 birds km 2 (Singh and Buckingham 2015), although both studies used playback methods (but line transects instead of point counts) to estimate density of Bristled Grassbird. Therefore, these largely dissimilar population estimates of Bristled Grassbirds from Nepal may be incomparable to our results from Bangladesh since different methods were used to compute densities.…”

“…This South Asian endemic is thought to be undergoing a rapid population decline due to the loss of dense floodplain grassland habitats, and is listed as globally ‘Vulnerable’ (BirdLife International 2019). The species is likely to face severe threats in the near future, as floodplain grasslands continue to be converted and degraded throughout its range in Bangladesh, India, Nepal, and Pakistan (del Hoyo et al 2006, Baral et al 2013, BirdLife International 2019, Collar et al 2017). The current global population of the Bristled Grassbird is estimated to be 3,500–15,000 individuals, although population size is difficult to assess because the species often remains undetected owing to its secretive behaviour during the non-breeding season, and therefore it is likely to be overlooked outside its breeding seasons and known areas (Singh and Buckingham 2015, Baral et al 2013, BirdLife International 2019).…”