Archived 2011-2012 topics: White-eared Night-heron (Gorsachius magnificus): request for information

Initial deadline for comments: 31 January 2012 [note that this has been moved back by about two months].

BirdLife species factsheet for White-eared Night-heron

White-eared Night-heron Gorsachius magnificus is an enigmatic resident of tropical and subtropical forests, often with associated aquatic habitats, in southern China and northern Vietnam. It is listed as Endangered under criterion C2a(i) on the basis that its population numbers fewer than 1,000 mature individuals, with the largest subpopulation numbering fewer than 250 individuals, and is thought to be in decline owing to hunting and forest clearance for timber and agricultural expansion, as well as damming of some sites for flow regulation.

Extensive survey effort has recently resulted in many records from new locations, leading to a considerable extension of its known range and suggesting that the species has been under-recorded and may in fact breed over a wider area of southern China and northern Indochina (He Fen-qi et al. 2007a,b, Pilgrim et al. 2009). There are now thought to be 11 relatively separate sub-populations (He Fen-qi et al. 2007b). It has also been noted that the species is capable of surviving and breeding in rather degraded habitats (He Fen-qi et al. 2007a). Although the population is still suspected to be in rapid decline owing to on-going threats, the increase in its known range raises the question of whether the current population estimate of 250-999 mature individuals should be revised upwards.

Further information on this species is requested, with particular emphasis on population estimates and sub-population structure, and comments are also invited on the suspicion of a rapid population decline.

References:

He F. Q., Fellowes, J. R., Chan, B. P. L., Lau, M. W. N., Lin J. S. and Lee K. S. (2007a) An update on the distribution of the ‘Endangered’ White-eared Night Heron Gorsachius magnificus in China. Bird Conserv. Int. 17: 93-101.

He F. Q., Zhou F., Yang X. J., Yang L., Deng X. J., Hu H. X., Lin J. S., Jiang H. D., Lin Z., Li L., Zhu K. M., Anderson, B., Zhang H. H. and Dong J. T. (2007b) Study on the status of distribution and subpopulation of the White-eared Night Heron (Gorsachius magnificus). Acta Zootaxonomica Sinica 32: 802-813.

Pilgrim, J. D., Walsh, D. F., Tran T. T., Nguyen D. T., Eames, J. C. and Le M. H. (2009) The Endangered White-eared Night Heron Gorsachius magnificus in Vietnam: status, distribution, ecology and threats. Forktail 25: 143-147.

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  4. Archived 2011-2012 topics: Black-footed Albatross (Phoebastria nigripes): eligible for downlisting?
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2 Responses to Archived 2011-2012 topics: White-eared Night-heron (Gorsachius magnificus): request for information

  1. It’s possible that the population approaches 1,000 but I wouldn’t assume this – anyway I think it’s very unlikely to number as many as 2,500. I’m not sure we know enough about the biology for reliable speculation about subpopulation structure, but for assessment purposes it doesn’t matter whether they’re all separate or not. Further decline is probable due to hunting and disturbance, so it qualifies as EN under C2(a) by either (i) or (ii), depending on whether the scattered populations are assumed to be separate. It’s probable that some are separate, so (i) seems a safer bet.

  2. The Heron Specialist Group has reviewed the Globally Threatened Bird Forum Request for Information regarding the status of the White-eared Night Heron. The Group does not support an increase in the estimated population size nor change in status of this species. The species was down listed from CR to EN in 2000. This down listing, which the Specialist Group considered at the time to be premature, was based on the possibility that more extensive surveys might find additional populations. Since that time such extensive surveys were undertaken by He Fenqi and colleagues and indeed, as hoped, more populations were found. While the surveys extend both the range and known habitat breadth of the species, these populations each are small and likely mostly isolated. With respect to populations size, there is no evidence that would suggest that the world species population size is greater than 999 individuals. There remains as much of an argument that the population remains under 250 individuals. With respect to isolation, it is likely that most if not all currently known populations are isolated. It certainly is the case that no population segment exceeds 250 individuals. While there is a lack of information on population fluctuations, there can be little doubt that the species has been undergoing a long term decline due to habitat loss, hunting for food, and other human impacts. There is no evidence to suggest the decline is abated, only that more sites are now known. The species continues to qualify as EN under criteria C2(a) (i) or C2(a) (ii).

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