The Griffon Vulture (Gyps fulvus) was once widespread throughout Bulgaria, but poison-related incidents led to the extinction of the species in certain areas. To restore the breeding population of the species, between 2010-2020, 61 rehabilitated and captive-bred Griffon Vultures from Spain, France and several European zoos were released from an acclimatisation aviary in the Vrachanski Balkan Nature Park in north-western Bulgaria. With the first breeding success in the wild in 2015, the population is growing since then. A recently published study analyses the results of this successful ten-year reintroduction project.
The reintroduction of Griffon Vultures in the Vrachanski Balkan Nature Park
Until the 1950s, there were 7 breeding sites within the Vrachanski Balkan Nature Park (VBNP). Poison-related incidents, often targeting mammal predators, had a strong impact on the Griffon Vulture population and the breeding colony became extinct in 1970. For a long period, the species was considered absent from the area.
With the aim of restoring the population to its historical breeding sites, the Action Plan for the Recovery and Conservation of Vultures in the Balkan peninsula was created in 2004, and the VBNP was one of the places chosen to reintroduce the species. After extensive preparatory work and a detailed visibility study, the reintroductions started in 2010, with the release of the first Griffon Vulture guild of wild-hatched individuals from Spain. During the ten years of the “establishment phase” (according to Armstrong and Seddon, 2008), 52 Griffon Vultures were translocated and released to VBNP. Most of the vultures hatched in the wild and were rehabilitated in Spain and France, but some individuals were also born in captivity in various European Zoos. The majority were immature birds, but also some juveniles and adults were released.
Methodologies of the reintroduction project
As Griffon Vultures arrived in Bulgaria, they entered an acclimatisation aviary, where they could socialise with other individuals while getting used to the new environment. Following the “soft-release” methodology, developed and applied in the Massif Central region of France in the 1980s by Terrasse and Choisy (2007), after an initial period kept in the acclimatisation aviary, vultures were encouraged to leave the aviary and forage on their own.
A fenced feeding station was installed in front of the aviary, to ensure they would stay around the release area. Food was provided at least twice a week, mainly livestock carcasses. Thanks to the PVC rings and wing tags that each bird received (along with the metal ornithological rings), the local team was able to monitor the behaviour and moves of Griffon Vultures, that came recurrently to feed in the station. Additionally, 17 Griffon Vultures were also fitted a GPS transmitter, which helped to calculate the home and dispersal range and detect cases of mortality.
Some Griffon Vultures established in VBNP migrated from different regions
Included in a large-scale national process to restore former colonies of the species, Griffon Vultures were also released in the same period in the Eastern Balkan Mountains (Sinite Kamani Nature Park and Kotlesnka Planina SPA) and in the Central Balkan National Park and Kresna SPA. Some of the released vultures were seen in the VNBP feeding station, along with other Griffon Vultures from a natural population in the Eastern Rhodope Mountains (Bulgaria). Individuals from Serbia, Croatia, Israel, Italy, Greece, and North Macedonia were also identified on site.
At the beginning of the reintroduction programme, 0.80 of the individuals observed in VBNP were released in the area, but the number gradually decreased as more birds from other regions visited the feeding station. According to the authors,
“these numbers reflect the growing importance of VBNP for the vultures released locally and as a core area offering suitable conditions, attracting and retaining many exogenous birds.”
Breeding success and mortality of the Griffon Vulture reintroduction project
It takes around 5 years for a Griffon Vulture to reach sexual maturity. The first breeding behavours were seen in 2013, but breeding success was only recorded in 2015, with 5 pairs successfully fledging their chicks in the wild. Since then, 42 chicks fledged, and the number of pairs gradually increased to 23 in 2019.
In 2020, however, the number of breeding pairs dropped to 18 due to a mass poisoning event that happened in September 2019. Two of the 5 Griffon Vultures that died had a GPS transmitter, which enabled a fast response and the removal of the poisoned carcass. The incident prompted legal action by the Ministry of Environment in Bulgaria, that committed to adopting a national stratgy to combat illegal wildlife poisoning. In total, 21 vultures released in the VBNP were found dead, mainly by poisoning. Electrocution was also a significant mortality cause.
The future of the restored Griffon Vulture population
With an estimated population of 55-70 individuals and 20-23 breeding nuclei spread in 3-5 colonies, the reintroduction project was considered very successful. The VBNP is now an important refuge for Griffon Vultures, acting as a source population to secure the future of the species in Bulgaria.
Although no more reintroductions are planned, since the establishment phase is considered complete, the newly established population is still vulnerable and susceptible to poisoning incidents. To ensure food availability, the local team will maintain the feeding station active, and a second feeding station in the eastern area of the park will also be activated.
The importance of international cooperation and EU funded projects
Many of the birds released in the VBNP were translocated from Spain. Thanks to a long-term collaboration with Junta de Andalucía, Junta de Extremadura and AMUS, wild-hatched Griffon Vultures that enter rehabilitation centres are translocated to other European countries. They have helped strengthen locally endangered (and in some cases extinct) populations of Griffon Vultures in Sardinia and Cyprus, and Cinereous Vultures across the Balkans Mountains. European Zoos and captive breeding centres were also fundamental to the success of reintroduction projects ongoing in Europe.
The Green Balkans, the Fund for Wild Flora and Fauna and the Birds of Prey Protection Society were the Bulgarian NGOs involved in the reintroduction project in the four release sites across the Bulgarian Mountains. Financial support of the EU’s LIFE Programme was determinant, with the project “Vultures Return to Bulgaria” and the “Vultures Back to Life”, in which the Vulture Conservation Foundation (VCF) was also a partner.
We have been following from close the reintroduction programme and supported the local partners with our experience, providing methodology, know-how transfer and data collection tips for releasing and monitoring birds. We are very proud of these outcomes in Bulgaria and congratulate all partner organisations and other stakeholders involved in the programme.
Source: Stoyanov G, Peshev HV, Kmetova–Biro E, Stoynov E, Ivanov I, Vangelova N, Nikolova Z, Mitrevichin E, Grozdanov A (2023) Results of the re-introduction of the Griffon Vulture (Gyps fulvus) in Vrachanski Balkan Nature Park, Bulgaria – completion of the establishing phase 2010–2020. https://doi.org/10.3897/BDJ.11.e100834