Archived 2018 topic: Crested Argus (Rheinardia ocellata): revise global status?

Crested Argus has two subspecies with range as follows (McGowan and Kirwan 2018):

R. o. ocellata – Annamite mountain chain in central and southern Vietnam (south to the Da Lat Plateau) and neighbouring eastern Laos.

R. o. nigrescens – mountains in C Peninsular Malaysia, mainly within Taman Negara National Park.

It is currently classified as Near Threatened on the basis of a moderately rapid population decline (approaching 30%) suspected to be taking place over three generations (16 years). It was argued by N. Brickle and J. C. Eames in litt. (2004) that there was little to suggest that the overall population was in decline, but a moderately rapid decline was maintained on a precautionary basis given the potential of locally high hunting pressure and continuing habitat loss.

There is little information available to calculate the population size, but the current Red List assessment uses a preliminary estimate that the population lies within the band 10,000-19,999 individuals, very roughly equating to 6,000-15,000 mature individuals.

The lack of recent records from the Indochinese part of the range does however suggest that a significant decline may have taken place, and it has been suggested that the species may now warrant listing in a category higher than Near Threatened (R. J. Timmins in litt. 2017).

At the previously reliable site of Bach Ma National Park (Vietnam) it was apparently last heard in 2010 (Radstaak undated). The same report considered that Lo Xo Pass was now “most likely…the only spot to hear this species in Indochina”. Other recent records from Indochina do indeed appear to be few and far between, even allowing for the elusive nature of the species. Automatic recorders detected the species at three sites within Ngoc Linh Nature Reserve (on the border of Kon tum and Quang Nam provinces) in 2016 (Vu Tien Thinh et al. 2017), while in Laos, it was heard at Khoun Xe Nong Ma protected area in 2017 (Mayer 2017). The only record on eBird within the last ten years is apparently of three individuals at Dak Blo Road (Kon Tum) in 2011 (https://ebird.org/view/checklist/S22418325).

The range of subspecies nigrescens is small, although wider than once thought, including the eastern flank of the East Coast Range of Peninsular Malaysia, where it is restricted to a narrow altitudinal band (D. Wells in litt. 2005). Previously it had been known only from eight sites within, or very close to, Taman Negara National Park. Populations on each mountain are likely to be small, and based on past field surveys the total population of this race was estimated at c. 200–2000 individuals; field studies in mid 1970s indicated population density of c. 8 birds/km² in 125–250 km² of habitat (McGowan and Kirwan 2018). Although it appears to be under less immediate threat than the Indochinese population, there is a lack of recent information from the Malaysian range.

Assessment against Red List Criteria

Criterion A – If the overall population was suspected to be decreasing by 30-49% in three generations (18 years) it would warrant listing as Vulnerable under Criterion A. If suspected declines were even higher, exceeding 50% in three generations (18 years) it would warrant listing as Endangered or higher. Declines approaching 30% in three generations would mean the species would continue to warrant listing as Near Threatened under the same criterion. Clearly there is very limited information to calculate trends for this species, therefore a careful analysis of the likely extent and severity of threats to the species across the range should be used to produce a best estimate for the rate of population change.

Criterion B – The species has an extent of occurrence (EOO) of 4,590,000 km2 so it does not meet the threshold for listing as Vulnerable under criterion B1. Please note that this is the area of a minimum convex polygon around the known range, and does not equate to the extent of suitable habitat for the species. The global area of occupancy (AOO) has not been calculated, but given the EOO, the AOO likely exceeds the threshold for Vulnerable under this criterion (2,000km2). Therefore, the species likely does not warrant listing as globally threatened under this criterion.

Criterion C – The global population is currently thought to lie within the range 6,000-15,000 mature individuals, although there is a very high degree of uncertainty about the total population size.  It could warrant listing as Vulnerable under criterion C2a(i) if total population was <10,000 mature individuals with ≤1,000 in each subpopulation, and a continuing population decline was inferred to be taking place (or if the total population was <2,500 mature individuals with 250-1,000 in the largest subpopulation). It would warrant listing as Endangered under criterion C2a(i) if the total global population is estimated to number <2,500 mature individuals with ≤250 in each subpopulation, and an inferred continuing population decline.

Criterion D – The population size and range are too large to warrant listing this species as Vulnerable under this criterion.

Criterion E – To the best of our knowledge, no quantitative analysis of extinction risk has been conducted for this species. Therefore, it cannot be assessed against this criterion.

The only relevant criteria for the assessment of this species are criteria A and C. The likely rate of population decline, along with potential population (and subpopulation) size are therefore key to determining whether a status change is warranted.

Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the information that is sought, or about the species’ Red List status.

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6 Responses to Archived 2018 topic: Crested Argus (Rheinardia ocellata): revise global status?

  1. Simon Mahood says:

    Note that the Dak Blo Road and the Lo Xo Pass are different names for the same site.

  2. Yong Ding Li says:

    Small numbers of the nominate subspecies has been documented recently in Khe Nuoc Trong by the survey team from Viet Nature (BirdLife in Vietnam), more details of encounter rates will be made available in upcoming papers. In Peninsular Malaysia, surveys have revealed a small, but potentially significant population of the nigrescens subspecies north-east (and outside the boundary of the Taman Negara), occurring from above 900m asl. More on this population will also be released very shortly. All data were collected using camera traps.

  3. Le Trong Trai says:

    In Vietnam, range distribution of this species stretches from Nghe An province (north) to Da Lat plateaux (south). Before 2000, this species was occurred in many places and now status became worst, locally extinct or very rare. Major threats: the first is hunting (snare)/indiscriminate hunting and the second is habitat loss. Camera trapping results conducted by Viet Nature (former BirdLife Vietnam programme) in some places indicated that: Ke Go Nature Reserve, Ha Tinh province: extinct (very common in 1996, 1997); Khe Nuoc Trong proposed nature reserve (Quang Binh province): seven birds from 60 photos were taken (2014-2016); Phong Dien Nature Reserve: a few birds were photographed in 2015 and 2016.
    In Khe Nuoc Trong, Viet Nature conducted a comprehensive survey in 2015 and have result: Twenty four groups of Crested Argus were detected in this survey. The hazard-rate function was selected as the best model in modeling detection probability. The detection probability for the whole survey is 0.54. We estimated the population size of Crested Argus in the surveyed area to be 48 groups and density to be 0.9 group/km2.
    Bac Huong Hoa Nature reserve, Quang Tri province: a few call were heard in 2013 and 2014. Overall status of this species is rare and scattered within their range distribution. Therefore, its conservation status would be treated as Globally Threatened Endangered (at least). Camera trapping and expert surveys should be needed; habitat protection (site protection); monitoring plan and law enforcement.

  4. Rob Martin (BirdLife International) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2018 Red List would be to list this species as Vulnerable under criteria A2cd+3cd+4cd.

    There is now a period for further comments until the final deadline in mid-July, 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 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  5. J. W. Duckworth says:

    For a three-generation assessment window of 18 year I think VU underestimates seriously the rate of loss in the last there generations. This species was still abundant in much of its Lao range (which is, however, only a small part of the global range so has a proportionately small effect on the global population change relevant to A). Its habitat use in Lao and Viet Nam overlaps quite well with that of Saola /Pseudoryx nghetinhensis/ the Saola Working Group of the IUCN SSC Asian Wild Cattle Specialist Group has a good feel for the prevalence of this species in camera-trapping in prime habitat from the large amount of camera-trapping that has taken place in Indochinese Crested Argus range in the last decade or so. It is now recorded only locally with many such surveys (suitable in length and style for a specie evidently readily photographed when present) failing to find it all. I do not have to hand the precise information but form various discussions with Saola-focused people I think the retraction in number of localities in which it is found (relative to the number given credible search) and in prevalence at those localities in which it still occurs, under A2 (decline in last three generations) VU may well be seriously underestimating (at 30-50%) the loss in the last 3 gens. At minimum, EN (50-80% loss) is appropriate. And the above says nothing in detail relevant to A3 – anticipated loss rate in the next 3 generations. All the indications are that industrial snaring is intensifying in its proportionate effects in Lao and VN; thre is not one area where snaring has been reduced by effective management to levels low enough not to continue to drive declines in remaining populations. If Crested Argus were an Indochinese endemic, I would have little hesitation in proposing CR under A3. The problem in this is that as a result of the swingeing recent declines in Indochina the proportion of the global population there is now very much lower than it was 18 years ago, and may be so low that the Malaysian population could comprise such a numerically significant proportion of the global population that its relative stability (if I’ve got this right – I know nothing about it first-hand) could moderate an anticipated Indochina-specific future decline of 80-90% between now and 2036 (and thus firmly within CR) to one much lower as a global average of I’china + Malaysia. Some speculation on the proportion of the current global population in each of the two sectors is critical to giving this species a credible application of the Red List C&C. I suspect that if the full information on camera-trapping results across Indochinese wet evergreen forest known by the Saola Working Group were available to the assessors of this species it is quite likely that a precautionary approach would go for CR under of A2, A3 and – depending on the proportion in Indochina A4. These camera-trapping data would take someone a meaningful amount of time to synthesis but the thinking behind applying to what they show can be seen in recently completed Red List assessments for other ground-dwelling snare-sensitive species like Owston’s Civet /Chrotogale owstoni/ (EN) and Large-antlered Muntjac /Muntiacus vuquangensis/ (CR). In general attributes (generation length, level of sensitivity to industrial snaring, detectability by typical camera-trapping methods and *prevalence on camera-trapping across Indochinese wet evergreen forest in the last decade*) Owston’s Civet and Crested Argus seem fairly similar. If Owston’s Civet did not have a now-substantial proportion of its population in upper highland areas which for various reasons are relatively unlikely to receive intensive industrial snaring, it would unquestionably have been categorised as CR, not EN, under A2, A3 and A4 (as were Large-antlered Muntjac and Saola, which do not have populations in the upper highlands). Unless the proportion of the Crested Argus global population in peninsula Malaysia 3 generations ago was large (40-50% or more) and/or the Malaysian population has been strongly increasing since 2000 (the real population not simply the known population) I cannot see how it is reasonable to put it as only VU under A2 and A3.

  6. James Westrip (BirdLife) says:

    Recommended categorisation to be put forward to IUCN

    Following further review, the recommended categorisation for this species has been changed, such that the species is proposed to be listed as Endangered.

    Final 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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