CR
Slender-billed Vulture Gyps tenuirostris



Justification

Justification of Red List Category
This species is classified as Critically Endangered because it has suffered an extremely rapid population decline, particularly across the Indian subcontinent, largely as a result of feeding on carcasses of animals treated with the veterinary drug diclofenac, perhaps in combination with other causes.

Population justification
Considerable confusion over the taxonomy and identification of Gyps vultures has occurred, making it difficult to be sure of the population size. In 2015, the population was estimated to be c.1,000 individuals in India (Prakash et al. 2019; MoEFCC 2020), 47 individuals in Cambodia (Sum & Loveridge 2016), fewer than 50 individuals in Nepal (DNPWC 2015), and a single breeding pair in Bangladesh (MoEF 2016). Very little is known about the size of the population in Myanmar, however counts made at vulture restaurants during 2003-2006 suggest a population of c.21 individuals (Hla et al. 2010). The total population is therefore thought to be c.1,100-1,300 individuals, roughly equating to 730-870 mature individuals.

Trend justification
This species declined across South-East Asia during the 20th century probably as a result of the collapse of wild ungulate populations and, to some degree, persecution. Survey results indicate that declines throughout the Indian Subcontinent probably began in the 1990s and were extremely rapid, resulting in an overall population decline of this species and G. indicus (which were only recognised as separate species in 2001) of greater than 97% over a 10-15 year period (Prakash et al. 2007), equating to 99% over three generations (36.09 years [Bird et al. 2020]). The combined population appeared to be relatively stable from 2003-2011 (Prakash et al. 2012), but declined again during 2011-2015, with a mean rate of decline from 2000-2015 of c.11% per year (Prakash et al. 2019), equating to 98.5% over three generations. In Nepal the species was formerly fairly common and widespread, but during 2002-2011 it declined by 18.7% per year (Chaudhary et al. 2012), equating to >99% over three generations, although there has since been a partial recovery (Galligan et al. 2020; Bhusal et al. 2019). It is now extremely rare in the east of Nepal and local and uncommon in the centre and west (Inskipp et al. 2016). The population in Cambodia, which until recently had remained remained relatively stable (with a steady increase during 2004-2013), declined from 68 to 37 individuals during 2013-2016 (Loveridge et al. 2019), equating to a decline of >99% over three generations.

Distribution and population

Gyps tenuirostris is found in India north of, and including, the Gangetic plain, west to at least Himachal Pradesh and Haryana, south to southern West Bengal (and possibly northern Orissa), east through the plains of Assam, and through southern Nepal, and north and central Bangladesh. It formerly occurred more widely in South-East Asia, but it is now thought to be extinct in Thailand and Malaysia, and the only recent records are from Cambodia, southern Laos and Myanmar. Considerable confusion over the taxonomy and identification of Gyps vultures has occurred, making it difficult to be sure of claims for this species. However, it appears to be allopatric or parapatric with Indian Vulture G. indicus where their ranges abut (or potentially do so) in northern India.

It was once common, but in South-East Asia populations declined through the latter half of the nineteenth century and the first half of the twentieth century, and are now probably very small and restricted in distribution and limited mainly to Cambodia (where the first nests recorded in the country were recently found and surveys in 2015 recorded a total of 47 individuals at vulture 'restaurants' [Sum & Loveridge 2016]) and Myanmar (counts made at vulture restaurants suggest a population of c.21 individuals [Hla et al. 2010]). Given the lack of intensive agriculture and associated chemical use in South-East Asia and the continued presence of large areas of suitable habitat for the species, the primary reason behind its decline in the region is thought to be the demise of large ungulate populations and improvements in animal husbandry resulting in a lack of available carcasses for vultures (Anon 2003, 2005).

In India and Nepal, the species was common until very recently, but since the mid-1990s it has suffered a catastrophic decline of up to 96.8%, with a combined average decline in India of this species and G. indicus of over 16% annually between 2000 and 2007 (Prakash et al. 2007). In Nepal the species was formerly fairly common and widespread, but during 2002-2011 it declined by 18.7% per year (Chaudhary et al. 2012), although there may have since been a partial recovery (Galligan et al. 2020). It is now extremely rare in the east of Nepal and local and uncommon in the centre and west (Inskipp et al. 2016). Extensive research has identified the non-steroidal anti-inflammatory drug (NSAID) diclofenac to be the cause behind this rapid population collapse (Green et al. 2004, Oaks et al. 2004a, Shultz et al. 2004, Swan et al. 2005). This drug, used to treat domestic livestock, is ingested by vultures feeding on their carcasses, leading to renal failure and causing visceral gout (Oaks et al. 2004a,b; Swan et al. 2005, Gilbert et al. 2006). Probably owing to the effects of diclofenac, breeding success in parts of its Indian range is reportedly low; of 14 nests found in Assam just four had chicks (Choudhury et al. 2005). Diclofenac is apparently entirely absent in Cambodia, adding greater importance to that remaining small population. Likewise, surveys conducted in Myanmar in late 2006 and early 2007 found no firm evidence of diclofenac use (Eames 2007). 

Ecology

It inhabits dry open country and forested areas usually away from human habitation. In South-East Asia it was found in open and partly wooded country, generally in the lowlands. This species feeds almost entirely on carrion, scavenging at carcass dumps and slaughterhouses, and at carcasses dumped in the fields and along rivers. It has only been recorded nesting in trees, usually large ones, usually at a height of 7-25 m, sometimes near villages but usually more remote. It is a solitary nester. While feeding, considerable mixed species aggregations can form (where it can be one of the more regularly aggressive vulture species [Hille et al. 2016]), and regular communal roost sites are used. It is social and usually found in conspecific flocks, interacting with other vultures at carcasses. Movements are poorly known, and the degree of connectivity of apparently separate populations is not known. Vultures also play a key role in the wider landscape as providers of ecosystem services. They were previously heavily relied upon to help dispose of animal and human remains in India.

Threats

By mid-2000, Gyps vultures were being found dead and dying in Nepal, Pakistan, and throughout India, and major declines and local extirpations were being reported. The anti-inflammatory drug diclofenac, used to treat domestic livestock, has been identified as the cause of mortality. Vultures are exposed to diclofenac (and other Non-Steroidal Anti-Inflammatory Drugs [NSAIDs]) through scavenging on the carcasses of largely cattle and buffalo that had been treated prior to death (often as part of palliative care) and left for scavengers to consume (as is tradition in Hindu cultures). Vultures are unable to process diclofenac and other vulture-toxic NSAIDs that therefore cause renal failure and death (Oaks et al. 2004a, Shultz et al. 2004, Swan et al. 2005, Gilbert et al. 2006). Modelling has shown that to cause the observed rate of decline in Gyps vultures, just one in 760 livestock carcasses need contain diclofenac residues (Green et al. 2004) and sampling carcasses of livestock in India between 2004 and 2005 showed that 10% were contaminated with diclofenac (Taggart et al. 2009). Despite awareness programmes to educate locals about the association between diclofenac and vulture mortality, a survey in Nepal indicated that the vast majority of people still do not link diclofenac use to a decline in vulture populations (Anon 2009), potentially leading to a slower uptake of a vulture safe alternative drug (meloxicam). Also, despite bans and the wide availability of meloxicam, diclofenac is still widely found in carcasses and vultures (Cuthbert et al. 2014, 2016). This may be because the drug continues to be produced for human consumption, which is then sold on for veterinary purposes (Cuthbert et al. 2011, T. Galligan in litt. 2016); though this is not so much of a problem in Nepal and Pakistan (SAVE 2015). Other veterinary drugs (ketoprofen, flunixin, nimesulide, aceclofenac and fenbendazole) have also recently been identified to be potentially lethal to vulture species (Naidoo et al. 2009, Zorrilla et al. 2015, Cuthbert et al. 2016, Galligan et al. 2016, Sharma 2016).

In South-East Asia, the near-total disappearance of the species pre-dated the present crisis, and probably results from the collapse of large wild mammal populations due to overhunting and improved management of deceased livestock leading to scarcity of available food (Clements et al. 2013), but persecution and poisoning is also thought to be a problem. In Cambodia vultures are still threatened by extremely low population densities of wild ungulates, a decline in the number of free-ranging domestic ungulates, felling of nesting trees for timber and accidental poisoning at carcasses laced with pesticides (S. Mahood in litt. 2012; Sum & Loveridge 2016). 

Other potential contributory factors to declines in this species are direct persecution, pesticide use and electrocution/ collision with energy infrastructure (Botha et al. 2017) but these are probably of minor significance.

Conservation actions

Conservation Actions Underway
CITES Appendix II, CMS Appendices I & II, Raptors MOU Category 1. It has been reported from many protected areas across its range. The governments of India, Nepal and Pakistan passed legislation in 2006 banning the veterinary use of diclofenac, and Bangladesh followed suit in 2010. A letter from the Drug Controller General of India in 2008 warned more than 70 drugs firms not to sell the veterinary form of diclofenac, and to mark human diclofenac containers 'not for veterinary use' (BirdLife International 2008). These bans have led to a reduction of diclofenac within ungulate carcasses (the principal food source for vultures) in India (Cuthbert et al. 2011a ) and a study of 11 administrative districts in Nepal found diclofenac use dropped by 90% since 2006 following the introduction of measures to reduce its use (Anon 2008). However, levels of diclofenac contamination still remain high and human forms of the drug are still sold for veterinary use (Cuthbert et al. 2011a,b). In response to the misuse of human diclofenac, the Government of India banned the manufacture of all diclofenac products in vial sizes larger than 3 ml (the single dose for humans) in 2015, which is predicted to make the drug too expensive and too complicated to use on large-bodied animals and thereby stop its misuse in livestock (T. Galligan in litt. 2016). Efforts to replace diclofenac with a suitable alternative are on-going and are showing signs of success with evidence for a decrease in diclofenac and an increase in the safe alternative (Cuthbert et al. 2011c ). An alternative drug, meloxicam, which is out of patent and manufactured in Asia has been tested on Gyps vultures with no ill-effects (Swan et al. 2006a, Swarup et al. 2007); though three additional drugs, aceclofenac, nimesulide and ketoprofen, are known to be toxic to vultures, and approximately another 10 drugs need to be tested (Galligan 2013, Cuthbert et al. 2016).

SAVE (Saving Asia's Vultures from Extinction) has developed the concept of Vulture Safe Zones; areas (with a minimum of 100 km radius, equating to 30,000 km2) around important vulture breeding colonies, where education and advocacy efforts are focussed on eliminating the use of diclofenac and other vulture-toxic drugs (Galligan 2013, Mukherjee et al. 2014). Conservation activities include: meeting key groups (e.g. pharmacists, veterinarians and livestock owners); engaging government officials (e.g. drug control, livestock services and forest departments) at tehsil, district and state levels; engaging with the public (e.g. festival programmes, media coverage and signage); diclofenac-free district declaration; community-run formal or informal Vulture Safe Feeding Sites (i.e., vulture [Jatayu] restaurants); vulture-related income generation for villages at nesting or feeding sites; diclofenac-meloxicam exchanges; husbandry and veterinary training camps; and national and international ecotourism to feeding sites and conservation breeding sites (T. Galligan in litt. 2016). There are currently 12 provisional Vulture Safe Zones being established in countries including India, Nepal and Bangladesh (Mukherjee et al. 2014). These areas will provide a safe environment into which birds bred in captivity can be released (Bowden et al. 2012).

Vulture restaurants are used as ecotourism attractions in parts of the species's range to raise awareness and fund supplementary feeding programmes and research - in Cambodia these are run by The Cambodia Vulture Conservation Project and a partnership between national and international conservation NGOs (e.g. Masphal and Vorsak 2007, H. Rainey in litt. 2008). Birds have been satellite tagged in various parts of their range to improve understanding of their movements, foraging range, site fidelity etc., in order to develop suitable conservation strategies for the species (Ellis 2004). Socioeconomic surveys in Nepal have shown that local people are strongly in favour of vulture conservation because of the associated ecological services that they provide (Gautam and Baral 2003).

The Report of the International South Asian Vulture Recovery Plan Workshop in 2004 gave a comprehensive list of recommendations including establishing a minimum of three captive breeding centres each capable of holding 25 pairs (Bombay Natural History Society 2004). Captive breeding efforts began in 2006 when 18 Slender-billed Vultures were captured for the captive-breeding facility in Pinjore, India. The centre is part of a captive breeding programme established by the RSPB and Bombay Natural History Society. In April 2008, there were 28 birds at the three Indian breeding centres (Pain et al. 2008), increasing to 35 birds in 2009 (Bowden 2009). Two individuals bred in captivity for the first time in 2009. By November 2015, the total number in breeding centres in India was 218, 15 at a centre in Pakistan and 57 at a centre in Nepal (SAVE 2015). The Central Zoo Authority of India has also set up several Vulture Consevration Breeding centres (T. Galligan in litt. 2016). A website has been set up to allow researchers to contribute data on known colonies to identify founder individuals for captive breeding efforts that represent the full geographical spread of the species (M. Gilbert in litt. 2004). Captive breeding centres often receive vultures that have been found poisoned and then rehabilitated by rescue centres such as the Centre for Wildlife Rehabilitation and Conservation, Assam, which is run by the International Fund for Animal Welfare (IFAW), the Wildlife Trust of India and the Assam Forest Department (Wildlife Trust of India 2019). Surveys utilising vulture restaurants were carried out in Myanmar in late 2006 and early 2007, accompanied by searches for nesting colonies, research into vulture deaths and investigation of possible diclofenac use in livestock (Eames 2007).

The species is covered by a Multi-species Action Plan (MsAP) for the conservation of African-Eurasian vultures (Botha et al. 2017). An updated 5-year (2020-2025) action plan has been produced for vulture conservation in India (MoEFCC 2020), a 9-year (2016-2025) action plan for Cambodia (Sum & Loveridge 2016) and Bangladesh (MoEF 2016), and a 4-year (2015-2019) action plan was was written for Nepal but has not been updated (DNPWC 2015). In 2012 the governments of India, Pakistan, Nepal and Bangladesh adopted a number of priority actions for the conservation of vultures, proposed by SAVE. These include banning large multi-dose vials of human diclofenac, testing other NSAIDs for toxicity to vultures and expanding the Vulture Safe Zones initiative (Galligan 2013). In 2014, SAVE produced A Blueprint for the recovery of South Asia’s Critically Endangered Gyps vultures that presents key conservation actions for the region and timelines for each action (SAVE 2014). 

Conservation Actions Proposed
Multiple Conservation Actions were proposed as part of SAVE (2014) and SAVE (2015). Measure the frequency of diclofenac treated carcasses available to vultures. Support the ban on the veterinary use of diclofenac (as well as the removal of human-use diclofenac in vials of >3 ml), and attempt to implement a ban on other vulture-toxic NSAIDs. Regulate the production of veterinary drugs to identify vulture-safe NSAIDs. Support species management or restoration, as needed. Initiate public awareness and public support programmes. Identify the location and number of remaining individuals and identify actions required to prevent extinction. Monitor remaining populations, in particular replicate conservation and research activities in Myanmar that have been implemented in Cambodia. Provide supplementary food sources where necessary for food-limited populations in South-East Asia, and maintain and promote Vulture Safe Zones, including trans-boundary efforts. Within VSZs, promote livestock management training and provide free veterinary camps. Support captive breeding efforts at a number of separate centres, and identify the most appropriate sites for release of captive-bred individuals. Attempt to estimate the potential value, in terms of ecosystem services, provided by wild vultures. Protect nesting areas.

Identification

80-95 cm. Thin, rather long-necked vulture. Perched adults have dark bill with pale culmen; black cere; a near-total lack of feathering on the black head and neck. Cold brown overall colouration and scruffy, ill-kempt appearance. Juveniles are very similar but have black head and necks with a hint of white down on the nape and upper neck. Underparts are pale streaked. In flight the white downy thigh patches are distinctive. Similar spp. Jizz is remarkably different from other Gyps vultures due to slender snake-like neck, thin elongated bill, angular crown and scruffy appearance. Eye ring is dark and does not contrast with facial skin. Head and neck skin is bare and thickly creased and wrinkled.

Acknowledgements

Text account compilers
Haskell, L.

Contributors
Baral, H.S., Clements, T., Cuthbert, R., Galligan, T., Gilbert, M., Htin Hla, T., Inskipp, C., Khan, M., Mahood, S., Paudel, K., Rahmani, A., Rainey, H., Riseborough, R., Benstead, P., Bird, J., Ashpole, J, Westrip, J.R.S., Butchart, S., Crosby, M., Symes, A., Calvert, R., Allinson, T, Wheatley, H., Martin, R. & Taylor, J.


Recommended citation
BirdLife International (2022) Species factsheet: Gyps tenuirostris. Downloaded from http://www.birdlife.org on 05/07/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 05/07/2022.