Archived 2018 topic: A reassessment of the Red List status of several Asian hornbill species

BirdLife is currently undertaking a review of the Red List status of forest dependent species following analyses of forest loss carried out by Tracewski et al. (2016) (see background forum topic here). A subset of Asian hornbill species come out of this analysis as potentially quite highly impacted by deforestation, and hunting may be adding to declines in these species; especially as deforestation makes more forest accessible for hunters (see Kinnaird and O’Brien 2007).

Hornbills are hunted for a range of reasons (see Kinnaird and O’Brien 2007); be it consumptive (as food or medicines), decorative (e.g. to make decorative items out of their ‘ivory’ casques or their feathers being used in traditional dress), the pet trade or persecution. Kinnaird and O’Brien (2007) estimate that at least 67% of hornbill species in Asia are hunted, and that any harvesting over 5% of the standing biomass will lead to local declines or disappearance (for a 2kg species occurring at 1 pair per km2). Therefore, not only is hunting widespread but it has the propensity to be having a severe impact on some Asian hornbill species, although clear figures about the impact of hunting on individual hornbill species are scarce.

One species where hunting is considered to be having a major impact is Helmeted Hornbill (Rhinoplax vigil) (see Beastall et al. 2016). In 2015 Helmeted Hornbill (Rhinoplax vigil) was uplisted from Near Threatened to Critically Endangered because of the potential threats from deforestation, and importantly from the high hunting pressure on this species due to the illegal trade of its  unique solid casque, which was suspected to be rapidly increasing and spreading across its range. It has also been suggested that the high demand for the Helmeted Hornbill’s casque may additionally be impacting other hornbill species, as poachers hunting for Helmeted Hornbills may shoot other large hornbill species either by accident or to make sure they don’t miss the opportunity to get hold of their target species (R. Wirth in litt. 2017). Therefore, it seemed appropriate to assess these species separately from the general deforestation topic.

When assessing the species contained within this topic, each species was re-assessed against all Red List criteria. All of these species have a range size that far exceeds the thresholds for Vulnerable under criterion B, and to the best of our knowledge no full quantitative analysis of the probability of extinction has been conducted for any species and so they cannot be assessed against criterion E. Of the species within this topic, only Great Hornbill (Buceros bicornis) has a population size estimate, which is thought to approach but not meet the threshold for Vulnerable under criterion C. All other species have not had their population size estimated, but are currently not thought to approach the threshold for Vulnerable under criterion C or D. Therefore, this topic will focus on criterion A (population reduction), although any comments regarding clearer estimates of population size for these species would be welcome.

As criterion A requires an assessments over a 3 generation period, we present for each species a) the % of forest habitat within the species range that was lost between 2000 and 2012 (per Tracewski et al. [2016]), b) the three-generation period based on generation lengths held in current Red List assessments for each species, and c) the extrapolated % decline as a result of forest loss over three generations assuming continued habitat destruction. The potential impact of hunting is then taken into account for each species, and a new Red List status is proposed.

 

Wrinkled Hornbill (Rhabdotorrhinus corrugatus) – Current listing NT A2c+3c+4c

  • % forest lost within range 2000-2012 = 18.3%
  • Three-generation period = 57 years
  • Extrapolated % decline over three generations = 61.7%

In addition to the generic threat of hunting, and the potential for other large hornbills to be taken as ‘bycatch’ by hunters targeting Helmeted Hornbills, this species is intolerant of degraded or secondary habitat. Therefore, the rate of decline is potentially even greater than that of forest loss. It is tentatively suspected that the overall rate of decline would still fall in the range 50-79% over three generations, and so it is proposed that the species be listed as Endangered under criteria A3cd+4cd.

 

White-crowned Hornbill (Berenicornis comatus) – Current listing NT A2c+3c+4c

  • % forest lost within range 2000-2012 = 13.4%
  • Three-generation period = 57 years
  • Extrapolated % decline over three generations = 49.6%

While this species may be tolerant of some habitat degradation, the rate of habitat loss is exceptionally close to the threshold for Endangered. Therefore, given the potentially additional generic threat of hunting to Asian hornbills, and the potential for other large hornbills to be taken as ‘bycatch’ by hunters targeting Helmeted Hornbills, it may be precautionarily suspected that declines over three generations may fall into the range 50-79%. Hence it is proposed that the species be listed as Endangered under criteria A3cd+4cd.

 

Rhinoceros Hornbill (Buceros rhinoceros) – Current listing NT A2c+3c+4c

  • % forest lost within range 2000-2012 = 11.8%
  • Three-generation period = 55.2 years
  • Extrapolated % decline over three generations = 43.8%

In addition to the impact of forest loss, this species is known to be impacted by hunting, with the species being caught for food, trade and the use of body parts in ceremonial dress (Kemp and Boesman 2017a). The potential that other large hornbills are being taken as ‘bycatch’ by hunters targeting Helmeted Hornbills has also been suggested. The rate of decline due to hunting alone is uncertain, but given the high rate of habitat loss, the species may at least warrant uplisting to Vulnerable under criteria A3cd+4cd (30-49% decline over three generations), and potentially could warrant listing as Endangered under the same criteria.

 

Black Hornbill (Anthracoceros malayanus) – Current listing NT A2c+3c+4c

  • % forest lost within range 2000-2012 = 18.1%
  • Three-generation period = 27.6 years
  • Extrapolated % decline over three generations = 36.7%

In addition to the generic threat to Asian hornbills of hunting, this species’ preference of flat lowland forest means that it may be particularly impacted by habitat loss (Kemp et al. 2017a). Given the extrapolated % decline over three generations due to forest loss, it is therefore suspected that the overall rate of decline for this species would fall in the range 30-49% over three generations. Thus it is proposed that this species be uplisted to Vulnerable under criteria A3cd+4cd.

 

Wreathed Hornbill (Rhyticeros undulatus) – Current listing LC

  • % forest lost within range 2000-2012 = 8.0%
  • Three-generation period = 57 years
  • Extrapolated % decline over three generations = 32.8%

This species is considered intolerant of habitat loss, requiring large areas of undisturbed forest (Kemp and Boesman 2017b), and is at least hunted locally (del Hoyo et al. 2001). Therefore, the rate of decline in this species is likely greater than the rate of forest loss, and is provisionally suspected to fall in the range 30-49% over three generations. Thus it is proposed that this species be listed as Vulnerable under criteria A3cd+4cd.

 

Great Hornbill (Buceros bicornis) – Current listing NT A2cd+3cd+4cd; C1

  • % forest lost within range 2000-2012 = 6.4%
  • Three-generation period = 55.2 years
  • Extrapolated % decline over three generations = 26.1%

It has been suggested that the main cause of decline in this species is habitat loss (Kemp and Boesman 2017c), although it is also targeted by hunters in several areas throughout its range. Its predictable behaviour in returning to certain feeding sites makes is susceptible to hunting (R. Naniwadekar and A. Datta in litt. 2016), with it being consumed as food and traditional medicine, its casque and feathers used as decorative items in local communities, and it may also be impacted by the pet trade (Eames 2008, Kemp and Boesman 2017b, R. Naniwadekar and A. Datta in litt. 2016). Therefore, the species is suspected to at least warrant being retained under its current listing as Near Threatened, but given the potentially high impact of hunting it is precautionarily proposed that Great Hornbill be uplisted to Vulnerable under criteria A3cd+4cd (30-49% decline over three generations).

 

Bushy-crested Hornbill (Anorrhinus galeritus) – Current listing LC

  • % forest lost within range 2000-2012 = 12.0%
  • Three-generation period = 29.4 years
  • Extrapolated % decline over three generations = 26.9%

This species does appear able to cope with a degree of habitat degradation, though avoids heavily impacted areas (Kemp et al. 2017b). Given the rate of forest loss it appears that the species at least warrants uplisting to Near Threatened, although it is uncertain whether the impact of hunting may mean that its overall rate of decline reaches the threshold for Vulnerable. Therefore, it is suggested that the species be at least uplisted to Near Threatened under criteria A3cd+4cd (declines approaching 30% in three generations), though we request further information as to whether the level of hunting pressure across the range may be sufficient to warrant the species’ listing as Vulnerable under the same criteria (30-49% decline over three generations).

 

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 about these proposed listings. Further information about the species can be found on their BirdLife Datazone pages.

 

References

Beastall, C.; Shepherd, C. R.; Hadiprakarsa, Y.; Martyr, D. 2016. Trade in the Helmeted Hornbill Rhinoplax vigil: the ‘ivory hornbill’. Bird Conservation International 26: 137-146.

del Hoyo, J.; Elliott, A.; Sargatal, J. 2001. Handbook of the birds of the world, Vol 6: Mousebirds to Hornbills. Barcelona, Spain: Lynx Edicions.

Eames, J. C. 2008. Rufous-necked and Great Hornbills confiscated in Myanmar. The Babbler: BirdLife in Indochina: 15.

Kemp, A. C.; Boesman, P. 2017a. Rhinoceros Hornbill (Buceros rhinoceros). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/55909 on 16 October 2017).

Kemp, A. C.; Boesman, P. 2017b. Wreathed Hornbill (Rhyticeros undulatus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/55926 on 16 October 2017).

Kemp, A. C.; Boesman, P. 2017c. Great Hornbill (Buceros bicornis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/55908 on 16 October 2017).

Kemp, A. C.; Boesman, P.; Sharpe, C. J. 2017a. Black Hornbill (Anthracoceros malayanus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/55906 on 16 October 2017).

Kemp, A. C.; Kirwan, G. M.; Sharpe, C. J. 2017. Bushy-crested Hornbill (Anorrhinus galeritus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/55884 on 16 October 2017).

Kinnaird, M. F.; O’Brien, T. G. 2007. The Ecology & Conservation of Asian Hornbills. Farmers of the Forest. The University of Chicago Press, Chicago.

Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

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16 Responses to Archived 2018 topic: A reassessment of the Red List status of several Asian hornbill species

  1. Praveen J says:

    Great Hornbill:
    I agree with the suggested uplisting of Great Hornbill based on its status in southern India. Though there are still large populations in Periyar & Anamalai subclusters of southern Western Ghats, all of them are undergoing severe pressure in non-protected areas (roughly 50% of its habitat is outside PA network in these clusters) though they are relatively safer inside protected areas.

  2. Ding Li Yong says:

    Wrinkled Hornbill – Not only the bycatch issue is pertinent, this species is also dependent on lowland forest, especially swamp forest, riparian forest and coastal dipterocarp forest, the most threatened of the Sundaic forest assemblages. The species occurs in low densities in logged forests – and have become quite rare in forest remnants in the southern Thai-Malay peninsula – e.g. Panti, Mersing, Arong, Lenggor among others; there are few recent records from Peninsular Thailand. The species merits at least EN – in recognition of these threats.

    • Simon Mahood says:

      Agreed. Wrinkled is a special case. It is very much dependent on low lying level forest, in which it of course needs large trees with holes in which to nest. For habitat reasons it is very rarely seen at regularly visited protected Sundaic lowland forest sites such as Danum and Taman Negara – they are not the right habitat for the species.

      The rate of loss or degradation (logging of large trees) of level lowland forests in the Sundaic region must significantly exceed the loss of general lowland forest formations overall, which given its specific habitat requirements surely makes this species a candidate for EN or CR status.

      • James Eaton says:

        I agree on Wrinkled Hornbill. In Peninsular Malaysia, two States with large areas of peatswamp forest I have not encountered a single bird despite numerous visits in recent years.
        I full inventory of the Pekan Peatswamp Forest in Pahang would be worthwhile to clarify the situation there where it, at least used to be, still present. Presumably a similar situation persists in West and South Kalimantan (can anyone shed any recent light, Adam Miller, Bas van Balen?) and lowland Sumatra.
        On Sumatra, Way Kambas National Park was always a reliable site to see the species (though only adults), until 2010, but since then, despite numerous visits I know no longer encounter the species here.
        Endangered at the very least, and yet another species that has most likely passed Critically Endangered decrease in population but due to lack of research is unlikely to be proven, with numbers now too low to for current research to show such a decline.

        • Yong Ding Li says:

          I found only one individual in the Lenggor Forest this year, and none in Panti (formerly regular in the 2000s). Definitely more work needed from Southeast Pahang, and the various lowland sites across Borneo and Sumatra. Perhaps WCS Indonesia, which has a programme in Way Kambas can provide some background on the situation there, and elsewhere in Lampung. Samunsam Wildlife Sanctuary which we just surveyed in south Sarawak had lots of suitable habitat, found no individuals, but Black Hornbill was locally common.

  3. We are of the view for uplisting for Great Hornbill (Buceros bicornis) from Near Threatened to Vulnerable, not only in view of pressures from hunting, but also due to severe impacts and demands being placed on their habitats. Apart from the issue of hunting in the north-eastern states of India, the serious concern of diversions/approved diversions of many river valleys and forested regions in these parts for developmental projects is a very grave issue today. Large protected habitats in India, does certainly offer a better protection for this species but this is not true in cases where they inhabit areas covered under commercial plantations. We are aware that certain plantation firms in India, have taken a more proactive role in safeguarding the interests of this bird but these are few, and with days to come irregular climatic patterns surely to impact their habitats in the hills, this species is facing threats which are going up.

  4. Anwaruddin Choudhury says:

    I agree upgradation of both Wreathed and Great Pied to Vulnerable. They are losing habitat and also being poached besides losing nesting trees regularly. Their absence in areas where they were plenty even in 1990s in northeastern India is too conspicuous.

  5. Le Manh Hung says:

    Thanks for the good news! I was thinking how and when those species (Great and Wreath Hornbills) will be uplisted. We were also listed those species in the Vietnam Government Degree on the rare and threatened species and is also going to uplisting their status in Vietnam Red Data Book.

  6. Rohit Naniwadekar says:

    This is a joint comment by Dr. Aparajita Datta and Dr. Rohit Naniwadekar for the Great hornbill

    An uplisting of the Great hornbill from Near Threatened to Vulnerable is desirable.

    We are writing here about the status of the species in the north-eastern region of India which forms a substantial part of its global range. Our large-scale surveys in Arunachal Pradesh (Naniwadekar et al. 2015 – Oryx; Naniwadekar, et al. 2016) have shown that Great Hornbills have gone locally extinct/extirpated from several sites. Another study was done in 2013-14 where interview-based occupancy surveys for five hornbill species were carried out across five other states (Assam, Tripura, Nagaland, Meghalaya and Mizoram) in north-east India. This large-scale survey states showed a reduction in >30% of its range over the past two decades (Naniwadekar, et al. 2016). We sampled 370 grids of 50 km2. The Great hornbill was not reported from 58% of 370 sampled grids. Of the total 3153 forested grids (1,54,497 km2) for which the prediction was done, the number of grids with relatively high probability of habitat use (≥ 0.75) for the Great Hornbill was 146 (7,154 km2). One of the major findings was that suitable areas for the Great Hornbill (4.6%) were less than 5% of the entire landscape (~1,50,000 km2). Protected Area extent and extent of forest cover were important variables governing the occurrence of the Great hornbill. Earlier studies in Arunachal Pradesh had demonstrated the importance of Protected Areas for Great Hornbill with mean densities of Great Hornbill being higher inside Protected Areas as compared to outside (Dasgupta and Hilaluddin 2012, Naniwadekar & Datta 2013, Naniwadekar et al. 2015). Therefore, the role of Protected Areas in the conservation of this species is very significant. The extent of forest cover in a grid was an important factor for the Great Hornbill. In Thailand, annual home ranges of Great Hornbill are known to be more than 100 km2 (Keartumsom et al. 2011). The need for large ranges makes the presence of large tracts of forest an important factor for the Great Hornbill. Across north-east India, Great Hornbills are hunted for their body parts and meat with 43% of 397 respondents using Great Hornbill meat for consumption, 27% for the casque, 23% using Great Hornbill feathers for cultural reasons/ trophy, and 20% using Great Hornbill body fat for varied medicinal purposes and even for polishing guns (Naniwadekar, Datta et al. in prep). Hunting is known to drive local populations of hornbills to extinction (Datta 2002, Naniwadekar et al. 2015). Habitat-use probability of the Great Hornbill was negatively associated with human population. Higher human populations are indicative of greater human pressures on forest (due to timber and fuelwood extraction) and for hunting. Great Hornbills are known to prefer lowland and foothill forests, in fact, usually below 1000 m in north-east India. These preferred lower elevation areas face significant pressures from logging and habitat conversion.
    Datta, A. 2002. Status of hornbills and hunting among tribal communities in eastern Arunachal Pradesh. Unpublished Report. Submitted to the Wildlife Conservation Society, New York and WCS-India Program, Bangalore.
    Keartumsom, Y., V. Chimchome, P. Poonswad, A. Pattanavibool, and N. Pongpattananurak. 2011. Home range of Great Hornbill (Buceros bicornis Linnaeus, 1758) and Wreathed Hornbill (Rhyticeros undulatus (Shaw) 1881) in non-breeding season at Khao Yai National Park, Nakhon Ratchasima Province. Journal of Wildlife in Thailand 18:47–55.
    Naniwadekar, R., and A. Datta. 2013. Spatial and temporal variation in hornbill densities in Namdapha Tiger Reserve , Arunachal Pradesh , north-east India. Tropical Conservation Science 6:734–748.
    Naniwadekar, R., C. Mishra, K. Isvaran, M. D. Madhusudan, and A. Datta. 2015b. Looking beyond parks: the conservation value of unprotected areas for hornbills in Arunachal Pradesh, Eastern Himalaya. Oryx 49:303–311.
    Naniwadekar, R., A. Datta, R. Raghunath, T. Karthik, M. Ghosalkar, B. Borah, & L. Lotha. 2016. Hornbill distribution in a biodiversity hotspot: occupancy modelling for hornbills in north-east India. Final report submitted to the Forest Departments of Assam, Meghalaya, Tripura, Nagaland and Mizoram.

  7. Rohit Naniwadekar says:

    A joint comment on uplisting the status of the Wreathed Hornbill by Dr. Aparajita Datta and Dr. Rohit Naniwadekar

    An uplisting of the Wreathed hornbill to Vulnerable is desirable.

    Update on the status of the species in north-east India which is an important part of its global range.

    In north-east India, based on extensive field and questionnaire surveys, Wreathed Hornbill breeding populations are restricted to Arunachal Pradesh and parts of Assam and North Bengal. An interview-based occupancy survey for five hornbill species were carried out across five states (Assam, Tripura, Nagaland, Meghalaya and Mizoram) in north-east India. The Wreathed hornbill was detected in 49% of 370 sampled grids. Of the total forested 3153 grids, (1,54,497 km2) for which the prediction was done, 60 grids (2,940 km2) had relatively high probability of habitat use (≥ 0.75) by Wreathed Hornbill. Even though its habitat-use probability has not declined much from the past, the species had lower detection probabilities in the present indicating lower abundances of the species compared to 20 years ago. Suitable areas for the Wreathed Hornbill (1.9%) is less than 5% of the landscape. Wreathed hornbill presence was positively associated with extent of forest cover and Protected Area and negatively associated with human population. Protected Areas are important for Wreathed hornbill with mean densities being higher inside Protected Areas (Dasgupta and Hilaluddin 2012, Naniwadekar & Datta 2013, Naniwadekar et al. 2015a). Wreathed Hornbills are known to range over 170 km2 annually (Keartumsom et al. 2011). Diet is mainly lipid-rich non-fig fruits (Datta and Rawat 2003, Naniwadekar et al. 2015b). The availability of these fruits varies over space and time (Datta and Rawat 2003, Naniwadekar et al. 2015b). To track these resources, Wreathed Hornbills in north-east India move across elevational gradients. The species is hunted, though less so than the Great hornbill. Based on 314 interviews, 43% used the meat, 27% used the head as a trophy, 13% used Wreathed Hornbill feathers for cultural and other reasons and 15% used its body fat as a medicine (Naniwadekar et al 2016). Given its wide-ranging movements over elevational gradients, conservation of Wreathed Hornbills is going to be a challenge. It requires lowland and foothill forests for nesting and it ranges in the higher elevations in the non-breeding season. For example, most of the population that visits Namdapha Tiger Reserve in high densities is probably breeding in neighbouring Myanmar (Naniwadekar et al. 2013). Similarly, most Wreathed Hornbill sightings in Mizoram and Nagaland are in the non-breeding seasons and we suspect that the birds breed in the lowland forests of neighbouring Myanmar. During this period, they are moving outside protected areas making them vulnerable to hunting pressures (Naniwadekar et al. 2015a). The lowland forests in Arunachal Pradesh and Assam have faced extensive pressures from logging and forest conversion and are being lost rapidly. Given that its long-term survival is dependent on forests that span international borders there is a likelihood that its range is shrinking in the north-eastern region.

    Datta, A., and G. S. Rawat. 2003. Foraging patterns of sympatric hornbills during the nonbreeding season in Arunachal Pradesh, Northeast India. Biotropica 35:208–218.
    Dasgupta, S., and Hilaluddin. 2012. Differential effects of hunting on populations of hornbills and imperial pigeons in the rainforests of the Eastern Indian Himalaya. Indian Forester 138:902–909.
    Keartumsom, Y., V. Chimchome, P. Poonswad, A. Pattanavibool, and N. Pongpattananurak. 2011. Home range of Great Hornbill (Buceros bicornis Linnaeus, 1758) and Wreathed Hornbill (Rhyticeros undulatus (Shaw) 1881) in non-breeding season at Khao Yai National Park, Nakhon Ratchasima Province. Journal of Wildlife in Thailand 18:47–55.
    Naniwadekar, R., and A. Datta. 2013. Spatial and temporal variation in hornbill densities in Namdapha Tiger Reserve , Arunachal Pradesh , north-east India. Tropical Conservation Science 6:734–748.
    Naniwadekar, R., C. Mishra, K. Isvaran, M. D. Madhusudan, and A. Datta. 2015a. Looking beyond parks: the conservation value of unprotected areas for hornbills in Arunachal Pradesh, Eastern Himalaya. Oryx 49:303–311.
    Naniwadekar, R., C. Mishra, and A. Datta. 2015b. Fruit resource tracking by hornbill species at multiple scales in a tropical forest in India. Journal of Tropical Ecology 31:477–490.
    Naniwadekar, R., A. Datta, R. Raghunath, T. Karthik, M. Ghosalkar, B. Borah, & L. Lotha. 2016. Hornbill distribution in a biodiversity hotspot: occupancy modelling for hornbills in north-east India. Final report submitted to the Forest Departments of Assam, Meghalaya, Tripura, Nagaland and Mizoram.

  8. Rob Martin (BirdLife International) says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2018 Red List would be to list:

    Wrinkled Hornbill as Endangered under criteria A3cd+4cd

    White-crowned Hornbill as Endangered under criteria A3cd+4cd

    Rhinoceros Hornbill as Vulnerable under criteria A3cd+4cd

    Black Hornbill as Vulnerable under criteria A3cd+4cd

    Wreathed Hornbill as Vulnerable under criteria A3cd+4cd

    Great Hornbill as Vulnerable under criteria A3cd+4cd

    Bushy-crested Hornbill as Near Threatened, approaching the threshold for listing under criteria A3cd+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.

  9. J. W. Duckworth says:

    For these hornbills the enormous assessment windows under A (reflecting very long generation lengths) mean that even modest calendar-timescale (i.e. as we observe thm in 10 or 20 years heavy surveying) declines are in Red List terms for more ‘serious’ than for a passerine. a 25% loss in 10 years for a fast-breeding passerine will place it in NT. 25% loss per decade for a hornbill with an assessment window of 55 years will place it in CR! I can see two ramifications of this for the hornbills.
    With the long assessment windows under A2 (c. 55 years) to the calculated aspect of forest loss should be added, for species with a significant proportion of their populations in northern SE Asia (Lao, Viet Nam, Cambodia, northern Thailand, probably parts of Myanmar), enormous hunting-driven losses have occurred. Even in the largest blocks of forest in Lao PDR (which are in the order of 3000-4000 sq km) large hornbills are now seriously reduced to make it, in some areas, difficult to find any even in a week or two of appropriate observation. The northern half of Lao is particularly badly affected compared with the southern. Yet at the start of the assessment window (about 1960!) Wreathed and Great certainly had enormous populations in Lao PDR (Wreathed was still pretty buoyant in many of the large blocks in the early 1990s) and presumably in much of the rest of SE Asia. Eyeballing the proportion of the 1960 range for great and Wreathed that was in this catastrophic hunting-led loss, I think it plausible that Vulnerable for both these species is an underestimate of the loss. For this chronically heavy-hunting part of these species’s range, I’m sure the population now compared with 1960 is less than 10%. Thus, declines of about 30% (as extrapolated for habitat-driven factor) for the last 3 gens in the rest of these species’ ranges would surely push the globally average decline well over 50%. (And that’s assuming that hunting-driven losses in the Sundaic and South Asian parts of these species’s ranges since 1960 are effectively trivial, i.e. there’s little more ‘hornbill-[nearly-]empty forest’ now than there was then). This also suggests that if the current categorisation of Rufous-necked Hornbill is intended still to remain VU, then assuming that its generation length is similar to the other SE Asian large hornbills, it, particularly, should also be considered for categorisation as EN: this has a higher proportion of its global range in the chronically heavy hunting area than either Wreathed or Great.
    It would be useful to see more clarity on how the forest loss rates were extended back for such a long period. In the preamble it states “c) the extrapolated % decline as a result of forest loss over three generations assuming continued habitat destruction” – is this intended to imply ‘rates of loss over the entire last three generations comparable to those in the 2000-2012 window’? If so, this is certainly not apt for some of the area. Per-year losses in Thailand in 2000-2012 considerably underestimate per year losses in the 1960s and 1970s for example. It may be that overall the changing rates in different countries might balance each other out and so indeed the globally averaged 55-yr habitat loss rate is indeed proportionate to that in 2000-2012, but this should be presented with some explanation more than the assumption implied above. RL guidelines specifically caution against ‘blindly’ extrapolating a trend from a well-measured few years back over a period much longer than the measured one.
    I also wonder – adding to the comments above specific to the sp. – if the situation for Wrinkled Hornbill is appropriately encapsulated in EN. That species’s strong association with level lowlands and restriction to large Sundaic landmasses makes it a risk that the 2000-2012 annual loss rate of habitat will be a serious underestimate of that in the 1960s-1980s. By 2000 most of such forest had been converted in Malaysia and its Thai range, and even in parts of Indonesia (I don’t know much about that). Particularly for this one a more nuanced treatment of forest lost in the last three generations is importnt to be made (or made explicit if it’s already been done): on such a long time-span there isn’t much of a difference between 60% (as given, tentatively, above, well within EN) and 80% (edge of CR territory).
    At tyhe moment I’m only suggesting a more detailed look at these factors – I can’t make in my head a precvise-enoguh mental picture of forest loss rate heterogeneity across each species’s range across the last 5-6 decades to have a good feel for what the real figures should be (i.e. they might be just what is put above), and don’t know enough about hunting-dirven losses outside northern SE asia to feel really how the heterogeneity in those across each species’s range would exacerbate the habitat-loss base-rate of decline.

    • Rob Martin (BirdLife International) says:

      Thank you for the detailed reply and I agree there is the potential for different rates of loss over the past half-century and more. Precisely due to the difficulties with casting backwards the full three-generation length for these large, slow-living species and the lack of comparable data, it was not considered that the data was sufficient to appraise these species against criterion A2. Hence we simply did not extrapolate the forest loss back from 2000-2012 dataset. These are difficult judgements, but we can have higher confidence in the current moving window under criterion A4 and make the reasonable judgement that current rates of loss will continue forwards under A3.

  10. Simon Mahood says:

    I know the forums are closed and so this is a comment for the next review period. With the uplisting of many Asian hornbills under A, when really these species have probably undergoing declines of a suitable magnitude for this uplisting for the last 20-50 years, it might be worth next year taking a look at some of the African species. Projections of forest loss, hunting (increased access due to road building), and logging (of which the importance for hornbills was, I think, under-estimated in the Asian discussion), can be couched in vague enough terms such that potentially some of the African hornbills can be uplisted 20-50 years before the Asian species were but based on similar reasoning. For birds with long generation lengths the use of A2, A3, A4 can be such a powerful conservation tool, like with albatrosses, the mass uplisting of an entire suite of birds due to a common factor, with dire predictions but sufficient time that conservation measures could be put in place and downlisting follows. Redlisting at its best. This is much less use when most of the damage has already been done.

  11. Jonathan Beilby says:

    The trade in all of these hornbills appears quite intense. I often see the wreathed and rhino hornbills for sale online in Java. Indeed populations of both have decreased dramatically (anecdotal evidence from trappers). The oriental pied was still common in areas I visited, but did not find much evidence of the rhinoceros hornbill on Java.

    The great hornbill seemed to be less evidently traded, but does not occur on Java. I heard from bird keepers that the sunda wrinkled hornbill (R. corrugatus) was hard to find in the trade; potentially an indication of low numbers in the wild?

  12. Claudia Hermes (BirdLife International) says:

    Recommended categorisations to be put forward to IUCN

    Following further review, the recommended categorisations for these species have been changed.

    Black Hornbill is now recommended to be listed as Vulnerable under Criteria A2cd+3cd+4cd.
    Bushy-crested Hornbill is now recommended to be listed as Near Threatened, approaching the threshold for listing under criteria A2cd+3cd+4cd.

    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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