Archived 2016 topics: Rufous-rumped Grassbird (Graminicola bengalensis) is being split: list G. bengalensis as Near Threatened or Least Concern and G. striatus as Vulnerable?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines

Lynx Edicions and BirdLife International will soon publish the second volume of the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Rufous-rumped Grassbird Graminicola bengalensis is being split into G. bengalensis and G. striatus, following the application of criteria set out by Tobias et al. (2010).

Prior to this taxonomic change, G. bengalensis was listed as Near Threatened under criteria A2c+3c+4c;C1+2a(i), on the basis that it was known to be declining moderately rapidly as a result of habitat degradation (BirdLife International 2016). G. bengalensis (as now defined following the taxonomic change) is found in tall (>1 m) lowland wet grassland, reed-swamp and other emergent vegetation near or in freshwater swamps or riverbanks (Baral et al. 2006). Its main stronghold is Nepal, where the population has been estimated at c. 2,000 pairs (Leader et al. 2010). It also occurs in Bangladesh, where it has mostly disappeared (Collar and Robson 2007) but has been recorded in small numbers in the north-east of the country (Thompson and Johnson 2003); and India where it is rarely reported but has been noted at several sites (see Leader et al. 2010). The total population size therefore is likely to fall within the range of 2,500-9,999 mature individuals. Conversion of its wetland habitat is likely to be causing declines in this species, but the rate of decline is uncertain. It is not thought that it may be sufficient to meet the threshold for Vulnerable given the population size (>10% over 3 generations [c.11years]), however, if there is evidence to suggest that it approaches this rate of decline then it may warrant listing as Near Threatened under criterion C1. In the absence of this information the species would warrant listing as Least Concern.

G. striatus occurs in wetland grassland and is known from South-East Asia (see Leader et al. 2010, Eaton et al. 2014). The species has recently been re-found in Myanmar (Eaton et al. 2014), but the population there is assumed to be very low (Leader et al. 2010) and Eaton et al. (2010) reported the species for the first time in Cambodia. There have been no modern records from Vietnam and Thailand, and so the species has been assumed to be extinct there (Leader et al. 2010). Extensive work has been done in south-east China, which has generated single records from Gaungxi and Guangdong (Lee et al. 2006, see Leader et al. 2010), and in Hong Kong the population has been estimated at 50-100 pairs (Leader et al. 2010) or maybe 490 individuals (So et al. 2012). Therefore the overall population size is suspected to be low (< 2,500 mature individuals), but the size of at least the Chinese sub-population is likely to be >250 mature individuals, pending further surveys. The population is likely to be declining as land is converted to agriculture, as well as the regeneration of shrubland, tree planting and grazing leading to a decrease in the amount of suitable grassland for this species (Leader et al. 2010). Therefore, the species likely warrants listing as Vulnerable under criterion C2a(i).

Comments are invited on these proposed categories and further information would be welcomed.

References:

Baral, H. S., Wattel, J. and Ormerod, S. J. 2006. Status, distribution, ecology and behaviour of Rufous-rumped Grass-warbler Graminicola bengalensis Jerdon with reference to Nepal. Journal of the Bombay Natural History Society 103(1): 44-48.

BirdLife International 2016. Species factsheet: Graminicola bengalensis. Downloaded from http://www.birdlife.org on 04/10/2016.

Collar, N. J. and Robson, C. 2007. Family Timaliidae (babblers). Pp.70– 291 in J. del Hoyo, A. Elliott & D. A. Christie, eds. Handbook of the birds of the world, 12. Barcelona: Lynx Edicions.

Eaton, J.A., Mahood, S.P. and Eames, J.C. 2014. Chinese Grassbird Graminicola striatus in South-East Asia: lost, forgotten and re-found. BirdingAsia 22: 19-21.

Leader, P.J., Carey, G.J., Olsson, U., Baral, H.S. and Alström, P. 2010. The taxonomic status of Rufous-rumped Grassbird Graminicola bengalensis, with comments on its distribution and status. Forktail 26: 121-126.

Lee, K. S., Lau, M. W-N., Fellowes, J. R. and Chan, B. P. L. 2006. Forest bird fauna of South China: notes on current distribution and status. Forktail 22: 23–38.

So I. W. Y., Wan J. H. C., Lee W. H. and Cheng W. W. W. 2012. Study on the distribution and habitat characteristics of the Chinese Grassbird Graminicola striatus in Hong Kong. Hong Kong Biodiversity 22: 1–9

Thompson, P. M. and Johnson, D. L. 2003. Further notable bird records from Bangladesh. Forktail 19: 85–102

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.

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2 Responses to Archived 2016 topics: Rufous-rumped Grassbird (Graminicola bengalensis) is being split: list G. bengalensis as Near Threatened or Least Concern and G. striatus as Vulnerable?

  1. Simon Mahood says:

    Sounds fair enough re. G. striatus

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to list:

    G. bengalensis as Least Concern.

    G. striatus as Vulnerable under criterion C2a(i).

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.