Gyps vulture populations across the Indian subcontinent collapsed in the 1990s and continue to decline. Repeated population surveys showed that the rate of decline was so rapid that elevated mortality of adult birds must be a key demographic mechanism. Post mortem examination showed that the majority of dead vultures had visceral gout, due to kidney damage. The realisation that diclofenac, a non-steroidal anti-inflammatory drug potentially nephrotoxic to birds, had become a widely used veterinary medicine led to the identification of diclofenac poisoning as the cause of the decline. Surveys of diclofenac contamination of domestic ungulate carcasses, combined with vulture population modelling, show that the level of contamination is sufficient for it to be the sole cause of the decline. Testing on vultures of meloxicam, an alternative NSAID for livestock treatment, showed that it did not harm them at concentrations likely to be encountered by wild birds and would be a safe replacement for diclofenac. The manufacture of diclofenac for veterinary use has been banned, but its sale has not. Consequently, it may be some years before diclofenac is removed from the vultures' food supply. In the meantime, captive populations of three vulture species have been established to provide sources of birds for future reintroduction programmes.

Populations of the White-rumped Vulture Gyps bengalensis, Indian Vulture G. indicus and Slender-billed Vulture G. tenuirostris declined rapidly during the mid-1990s all over their ranges in the Indian subcontinent because of poisoning due to veterinary use of the non-steroidal anti-inflammatory drug diclofenac. This paper reports results from the latest in a series of road transect surveys conducted across northern, central, western and north-eastern India since the early 1990s. Results from the seven comparable surveys now available were analysed to estimate recent population trends. Populations of all three species of vulture remained at a low level. The previously rapid decline of White-rumped Vulture has slowed and may have reversed since the ban on veterinary use of diclofenac in India in 2006. A few thousand of this species, possibly up to the low tens of thousands, remained in India in 2015. The population of Indian Vulture continued to decline, though probably at a much slower rate than in the 1990s. This remains the most numerous of the three species in India with about 12,000 individuals in 2015 and a confidence interval ranging from a few thousands to a few tens of thousands. The trend in the rarest species, Slender-billed Vulture, which probably numbers not much more than 1,000 individuals in India, cannot be determined reliably.

The provision of supplementary food at vulture restaurants is a well-established tool in the conservation of vulture species. Among their many applications, vulture restaurants are used to provide a safe food source in areas where carcasses are commonly baited with poisons. Rapid and extensive declines of vultures in the Indian subcontinent have been attributed to the toxic effects of diclofenac, a pharmaceutical used in the treatment of livestock, to which vultures are exposed while feeding on the carcasses of treated animals. A vulture restaurant was established at the Oriental White-backed Vulture Gyps bengalensis colony at Toawala, in Punjab province Pakistan, to test the effectiveness of the technique in modifying ranging behaviour and mortality at the colony. Six male vultures were fitted with satellite transmitters to describe variation in movement and home-range during periods when safe food was alternately available and withheld at the vulture restaurant. There was considerable variation in individual home-range size (minimum convex polygons, MCP, of 1,824 km2 to 68,930 km2), with birds occupying smaller home-ranges centred closer to the restaurant being more successful in locating the reliable source of food. Fixes showed that 3 of the tagged vultures fed at the vulture restaurant and the home-range of each bird declined following their initial visit, with a 23–59% reduction in MCP. Mean daily mortality during provisioning was 0.072 birds per day (8 birds in 111 days), compared with 0.387 birds per day (41 birds in 106 days) during non-provisioning control periods. Vultures tended to occupy greater home-ranges, cover greater distances each day and spend proportionately more time in the air during the late brooding and post-breeding seasons. Attendance at the vulture restaurant also declined during this period with fewer birds visiting less often and no tagged vultures visiting the vulture restaurant at all. These findings indicate that vulture restaurants can reduce, but not eliminate, vulture mortality through diclofenac exposure and represent a valuable interim measure in slowing vulture population decline locally until diclofenac can be withdrawn from veterinary use.

Populations of Critically Endangered White-rumped Gyps bengalensis and Slender-billed G. tenuirostris Vultures in Nepal declined rapidly during the 2000s, almost certainly because of the effects of the use in livestock of the non-steroidal anti-inflammatory drug diclofenac, which is nephrotoxic to Gyps vultures. In 2006, veterinary use of diclofenac was banned in Nepal and this was followed by the gradual implementation, over most of the geographical range of the two vulture species in Nepal, of a Vulture Safe Zone (VSZ) programme to advocate vulture conservation, raise awareness about diclofenac, provide vultures with NSAID-free food and encourage the veterinary use in livestock of a vulture-safe alternative NSAID (meloxicam). We report the results of long-term monitoring of vulture populations in Nepal before and after this programme was implemented, by means of road transects. Piecewise regression analysis of the count data indicated that a rapid decline of the White-rumped Vulture population from 2002 up to about 2013 gave way to a partial recovery between about 2013 and 2018. More limited data for the Slender-billed Vulture indicated that a rapid decline also gave way to partial recovery from about 2012 onwards. The rates at which populations were increasing in the 2010s exceeded the upper end of the range of increase rates expected in a closed population under optimal conditions. The possibility that immigration from India is contributing to the changes cannot be excluded. We present evidence from open and undercover pharmacy surveys that the VSZ programme had apparently become effective in reducing the availability of diclofenac in a large part of the range of these species in Nepal by about 2011. Hence, community-based advocacy and awareness-raising actions, and possibly also provisioning of safe food, may have made an important contribution to vulture conservation by augmenting the effects of changes in the regulation of toxic veterinary drugs.

The population collapse of resident Gyps vulture species in South Asia, caused by the use of a veterinary drug diclofenac, has highlighted an urgent need to monitor numbers of other vulture species in the region. This study assessed population trends of Himalayan Griffon Gyps himalayensis in the mountainous region of Upper Mustang, Nepal, which is an important breeding area for the species. Vultures were surveyed in 2002, 2004 and 2005 by recording the number of birds sighted along 188 km of transects, and observing numbers of birds at breeding colonies. The number of birds recorded per day and per kilometre of transect declined by 67% and 70% respectively over the period of study. The number of active nests declined by 84% from 2002 to 2005. The veterinary drug diclofenac was available in pharmacies in the Mustang region. Young Himalayan Griffons, which migrate to the lowland areas of Nepal and, in increasing numbers to India, are highly likely to be subject to diclofenac poisoning. If this rate of population decline occurs throughout the Himalayan region, the conservation status of the species will need to be urgently reassessed.

Following the catastrophic decline in populations of three species of South Asian Gyps vultures, we conducted a study to explore socio-economic variables that could facilitate conservation efforts. A questionnaire survey was carried out in 103 randomly selected households in the Rampur valley, one of the Important Bird Areas of Nepal, during 2004. Among respondents, 38% were female, 62% male, 28% illiterate and 72% literate. Households belonged to three ethno-religious groups (Hindu castes, ethnic groups and Muslim) and 96% of households had some parcels of registered land to farm. About 90% of households reared one or more types of livestock while the mean Livestock Size Unit was 3.32 per household. Livestock diseases and ailments were common and usually treated with diclofenac. Livestock carcass disposal practices were favourable to vultures because 60% of households dumped carcasses in open fields. Diclofenac is lethal to vultures; 3% of diclofenac-contaminated carcasses were available annually. The majority (78%) of respondents had favourable attitudes towards the concept of vulture conservation. Diclofenac contamination and the destruction of nesting habitat were two major threats to vultures. Ensuring healthy food through economic incentives, inculcating new values through environmental education and soliciting popular participation for habitat conservation are recommended.

Vulture populations are declining steeply worldwide. Vulture ‘restaurants’ or feeding stations are a tool for maintaining and monitoring numbers, but individual species may be disadvantaged by the effects of carcass distribution, carcass size and interspecific aggression. To test the degree to which restaurants give opportunities for each species to access the food provided, we studied behaviour and morphology in three Critically Endangered species of vulture in Cambodia: the gregariously breeding and feeding White-rumped Vulture Gyps bengalensis and Slender-billed Vulture G. tenuirostris, and the solitary Red-headed Vulture Sarcogyps calvus. We video-recorded attendance time, attendance order and dominance behaviour at different-sized carcasses. Interspecific aggression at carcasses was least frequently shown by the ‘small’ White-rumped Vulture. The relatively ‘large’ Slender-billed and ‘medium’ Red-headed Vultures showed aggression more regularly and at similar levels. However, the latter avoids conflict by waiting until Gyps vultures are no longer crowding at the carcass, although its arrival at carcasses was correlated with total number of vultures present. While more numerous than Red-headed, the two Gyps vultures are more dependent on large carcasses, which increases their vulnerability to further declines in wild large ungulate species. Body size, number of individuals, hunger levels and carcass size and availability all influence carcass attendance behaviour. An increase in the number and spatial distribution of restaurants as well as of carcass size range could boost numbers of all vulture species.

Three species of resident Gyps vulture are threatened with extinction in South Asia due to the contamination of domestic ungulate carcasses with the drug diclofenac. Observed rates of population decrease are among the highest recorded for any bird species, leading to total declines in excess of 99.9% for the Oriental White-backed Vulture Gyps bengalensis in India between 1992 and 2007. Vultures have declined in Nepal, but quantitative information on the rate and scale of decreases is unavailable. Road transect surveys for vultures, following the same route, methodology and timing, were undertaken in lowland areas of Nepal for seven years from 2002 to 2011. The seven survey transects followed Nepal’s East-West highway and covered 1,010 km in three years of the survey, and 638 km in the remaining four years. Slender-billed Vultures G. tenuirostris were very scarce, with a maximum of five individuals in 2002 and none recorded in 2010 and 2011. Oriental White-backed Vultures were most commonly recorded, but decreased from 205 to 68 birds over the survey period, with an estimated annual rate of decline of 14% a year. If population decreases commenced in Nepal in the same year as in India, then White-backed Vultures in Nepal have declined by 91% since the mid-1990s. Few resident Gyps vultures remained in Eastern and Central regions of Nepal, with just one, nine and six birds recorded in the three surveys that covered these regions. The majority of threatened Gyps vultures in lowland Nepal are now found in Western and Mid Western regions, where conservation efforts have been focused in the last six years. Removing veterinary diclofenac from across the country and continuing to manage effective “vulture safe zones” are essential to conserve Nepal’s remaining vulture populations.

Populations of three vulture species of the genus Gyps, the Egyptian Vulture Neophron percnopterus and Red-headed Vulture Sarcogyps calvus have declined markedly on the Indian subcontinent since the mid-1990s and all are now Critically Endangered or Endangered. Gyps vultures have been killed by the widely used non-steroidal anti-inflammatory drug diclofenac, ingested when they feed on carcasses of domesticated ungulates treated with the drug shortly before death. However, it is not known whether Egyptian Vulture and Red-headed Vulture are also sensitive to diclofenac. Veterinary use of diclofenac was banned in India in 2006. Since then, the prevalence and concentration of diclofenac in domesticated ungulates carcasses has decreased and population declines of Gyps vultures have slowed or reversed. Here, we examine counts of Egyptian and Red-headed Vultures obtained on road transects in and near protected areas between 1992 and 2011. We found indications that the declines in both species appear to have slowed and possibly increased after the ban was introduced, though the small numbers of birds counted make this conclusion less robust than that for the Gyps species. These results suggest that both species may have been adversely impacted by diclofenac and that government bans on this drug, which are beginning to take effect, may benefit a wider range of vulture species in the Indian subcontinent than was previously thought.

Three Critically Endangered Gyps vultures endemic to South Asia continue to decline due to the use of diclofenac to treat livestock. High nephrotoxicity of diclofenac to Gyps vultures, leading to death, has been established by experiment and observation, in four out of five Gyps vulture species which occur in South Asia. Declines have also been observed in South Asia’s four other non-Gyps vulture species, but to date there has been no evidence about the importance of diclofenac as a potential cause. Neither is there any evidence on the toxicity of diclofenac to the Accipitridae other than vultures. In this study, gross and microscopic lesions and diclofenac tissue levels in Steppe Eagles Aquila nipalensis found at a cattle carcass dump in Rajasthan, India, show evidence of the toxicity of diclofenac for this species. These findings suggest the possibility that diclofenac is toxic to other accipitrid raptors and is therefore a potential threat to much wider range of scavenging species in South Asia.

The Upper Mustang region of Nepal holds important breeding populations of Himalayan Griffon Gyps himalayensis. Despite this species being considered ‘Least Concern’ on the IUCN Red List, the population in Upper Mustang had declined substantially in the early to mid-2000s. During that period, the non-steroidal anti-inflammatory drug diclofenac was commonly used to treat illness and injury in domesticated ungulates throughout Nepal. The timing and magnitude of declines in Himalayan Griffon in Upper Mustang resemble the declines in resident populations of the ‘Critically Endangered’ White-rumped Vulture Gyps bengalensis and Slender-billed Vulture Gyps tenuirostris in Nepal, both of which are also known to be highly sensitive to diclofenac. Since 2006, the veterinary use of diclofenac has been banned in Nepal to prevent further vulture declines. In this paper, we analyse the population trend in Himalayan Griffon in Upper Mustang between 2002 and 2014 and show a partial recovery. We conclude that the decline is now occurring at a slower rate than previously observed and immigration from areas where diclofenac was either not or rarely used the probable explanation for the recovery observed.

Populations of Oriental White-backed Vulture Gyps bengalensis and Long-billed Vulture G. indicus declined in India between the mid 1980s and late 1990s. Regional reports from India described declines of 95–100% across a wide area. This study was conducted to investigate the breeding success and pattern of mortality in two vulture colonies (Dholewala and Changa Manga) within Punjab Province, Pakistan between December 2000 and June 2001. Breeding success was found to be 62% in Dholewala and 59% in Changa Manga. A total of 668 sick and dead vultures were collected of which 591 were less than one month post mortem. No significant variation was found in the weekly mortality rate of adult and subadult vultures during the study period spanning winter through summer. A peak in mortality rate was observed during late April and early May that corresponded to mortality of newly fledged juveniles. Minimum annual mortality rate in the adult breeding population was calculated to be 11.4% and 18.6% in Dholewala and Changa Manga respectively. In a subsample of dead vultures (n = 185) visceral gout was found in 80% of adults, 63% of subadults, 19% of juveniles and 13% of nestlings. These mortality rates were consistent with a rapid population decline. Results imply that the mortality factor responsible for the decline in Gyps vultures described in India is also present in Pakistan and will potentially lead to a population decline of a comparable magnitude.

The catastrophic declines of three species of ‘Critically Endangered’ Gyps vultures in South Asia were caused by unintentional poisoning by the non-steroidal anti-inflammatory drug (NSAID) diclofenac. Despite a ban on its veterinary use in 2006 (India, Nepal, Pakistan) and 2010 (Bangladesh), residues of diclofenac have continued to be found in cattle carcasses and in dead wild vultures. Another NSAID, meloxicam, has been shown to be safe to vultures. From 2012 to 2018, we undertook covert surveys of pharmacies in India, Nepal and Bangladesh to investigate the availability and prevalence of NSAIDs for the treatment of livestock. The purpose of the study was to establish whether diclofenac continued to be sold for veterinary use, whether the availability of meloxicam had increased and to determine which other veterinary NSAIDs were available. The availability of diclofenac declined in all three countries, virtually disappearing from pharmacies in Nepal and Bangladesh, highlighting the advances made in these two countries to reduce this threat to vultures. In India, diclofenac still accounted for 10–46% of all NSAIDs offered for sale for livestock treatment in 2017, suggesting weak enforcement of existing regulations and a continued high risk to vultures. Availability of meloxicam increased in all countries and was the most common veterinary NSAID in Nepal (89.9% in 2017). Although the most widely available NSAID in India in 2017, meloxicam accounted for only 32% of products offered for sale. In Bangladesh, meloxicam was less commonly available than the vulture-toxic NSAID ketoprofen (28% and 66%, respectively, in 2018), despite the partial government ban on ketoprofen in 2016. Eleven different NSAIDs were recorded, several of which are known or suspected to be toxic to vultures. Conservation priorities should include awareness raising, stricter implementation of current bans, bans on other vulture-toxic veterinary NSAIDs, especially aceclofenac and nimesulide, and safety-testing of other NSAIDs on Gyps vultures to identify safe and toxic drugs.

The cliff-nesting Long-billed Vulture Gyps indicus is one of four critically endangered Asian Vultures. In India, this species has declined catastrophically, but in Pakistan only small population declines have been recorded. Mortality of this species has been linked to poisoning by veterinary diclofenac, which was banned throughout south Asia in 2006. Between 2003 and 2012 we measured abundance of adult, sub-adult, juvenile, and dead vultures, and nest occupancy and productivity at the largest known Long-billed Vulture colony in Pakistan. We compared population parameters from before (2003−2006) and after (2007−2012) the ban on veterinary diclofenac. Our data and models indicate that vulture abundance, nest occupancy, and nest productivity declined 61%, 73%, and 95%, respectively, in the three years before the diclofenac ban, and then increased 1–2 years after the ban by 55%, 52%, and 95%. Furthermore, we observed 87% of total vulture mortalities prior to the diclofenac ban. Our results demonstrate for the first time since the onset of the Asian vulture crisis that the ban on veterinary diclofenac is an effective management tool for reversing Long-billed Vulture population declines.

The Critically Endangered Oriental White-backed Vulture Gyps bengalensis has declined across most of its range by over 95% since the mid-1990s. The primary cause of the decline and an ongoing threat is the ingestion by vultures of livestock carcasses containing residues of non-steroidal anti-inflammatory drugs, principally diclofenac. Recent surveys in Pakistan during 2010 and 2011 revealed very few vultures or nests, particularly of White-backed Vultures. From 2011 in the Tharparkar District of Sindh Province we monitored a colony of Oriental White-backed Vultures. Between 2011 and 2014 the number of active nests in this colony increased from 11 to 34 while nest density decreased from 13.7 to 9.2 nests km-2, suggesting that the colony is expanding. We conclude that the rate of increase is being subsidised by immigration, as the population demographics do not support the observed rate of increase in nests. We present the first analysis of spatial breeding dynamics for the Oriental White-backed Vulture and describe how a clustered pattern of nest trees in colonies supports a highly clustered pattern of nests. The spatial pattern of nests relies on both the distribution of trees and the ability of trees to support more than one nest. These results highlight that the preservation of larger nest trees and the sustainable management of timber resources are essential components for the conservation management of this species. We emphasise the high importance of this colony and a nearby Long-billed Vulture Gyps indicus colony in this area of Pakistan. Recommended conservation management actions include the continuation of a Vulture Safe Zone established in 2012, measuring breeding success, assessing dispersal and determining the impact of mortality on these populations.