Is the population trend of the Bearded Vulture Gypaetus barbatus in Upper Mustang, Nepal, shaped by diclofenac?

The Bearded Vulture (or Lammergeier) Gypaetus barbatus has been uplisted to Near Threatened because of declines throughout most of its range. In Upper Mustang, Nepal, the species underwent a substantial decline between 2002 and 2008. Diclofenac poisoning, through the consumption of contaminated livestock carcasses, is a serious threat to a number of scavenging raptors in South Asia. It is not known whether Bearded Vultures are intolerant to diclofenac; however, the timing and magnitude of the decline in Upper Mustang parallel those seen in the population of Himalayan Griffons Gyps himalayensis and the populations of six other South Asian vulture species, most of which are known to be intolerant to diclofenac. In this study, we continued the Upper Mustang survey for Bearded Vultures and use generalised linear models to examine the population trend between 2002 and 2014. We confirm a substantial decline after 2004 and show that this trend continued, albeit at a slower rate, up to 2014. However, we also show that subpopulations in remote valleys did not decline. We suggest that these trends are a strong indication that Bearded Vultures are intolerant of diclofenac and that the biology of the species and additional targeted threats are limiting its recovery in Upper Mustang.