Re-introduction of Griffon Vulture (Gyps fulvus) in the Eastern Balkan Mountains, Bulgaria – completion of the establishment phase 2010-2020

Abstract

The current study presents and analyses the results from the recently completed 11-year-establishment phase, following the start of the local re-introduction of the Griffon Vulture (Gyps fulvus) in Kotlenska Planina SPA and Sinite Kamani Nature Park in the Eastern Balkan Mountains of Bulgaria in the period 2010-2020. As a result of the re-introduction efforts and release of 153 individuals, the Griffon Vulture has been successfully reproducing again in the Eastern Balkan Mountains since 2016, after more than 40-50 years of absence. At 2020, the local population consists of some 80 local and up to 80-115 birds, together with sojourn individuals. Amongst them, 23-25 breeding pairs, located in five different colonies and two more frequently used roosting sites. The current average productivity remains relatively low: 0.41 fledglings/territorial pair and fledging success of 0.61 fledglings/breeding pair between 2016 and 2020, but shows a trend to increase with time and the growing experience of the young locally re-introduced population. The mortality confirmed between 2010-2021 accounts for 33%, mostly due to electrocution as a post-release effect in the first six months following their release. Our data show that the newly established population in the Eastern Balkan Mountains mostly forages on feeding sites, having a comparatively small 95% home range: 281.88 ± 91 km2 and 50% core area: 6.6 ± 2.28 km2 (range 4.7–8.5 km2). We, therefore, consider the establishment phase of the re-introduction of Griffon Vulture in this particular site as successfully completed, but management should continue. Furthermore, the area of the Eastern Balkan Mountains can currently be regarded as a "source" for the species within the source-sink population regulation concept in the national and Balkan context.

Seasonal and age-specific dynamics of the Griffon Vulture’s home range and movements in the Eastern Rhodopes

“…We conducted all further analyses with the remaining 415,434 GPS locations. We estimated vultures' foraging home range by applying the kernel density approach (Kenward 2001). We used iterative plug-in bandwidth selection (Amstrup et al 2004, Gitzen et al 2006.…”

Insights on the best release strategy from post-release movements and mortality patterns in an avian scavenger

“…Translocations are usually based on two different release strategies: soft and hard release (for translocation 7 ; for reintroduction 8 , 9 , 10 , 11 , 12 , 13 , 14 ). Soft release is based on the delayed release of individuals from a temporary enclosure, while hard release involves the immediate and direct release of individuals without any previous acclimatization.…”

Results of the re-introduction of the Griffon Vulture (Gyps fulvus) in Vrachanski Balkan Nature Park, Bulgaria – completion of the establishing phase 2010–2020

“…The practical re-introduction started in 2010 with the release of the first group of Griffon Vultures imported from Spain. The local initiative was a part of a large-scale national process to restore former colonies of the species, with simultaneous releases in the Eastern Balkan Mountains (Sinite Kamani Nature Park and Kotlesnka Planina SPA) ( Kmetova-Biro et al 2021 ), Central Balkan National Park and Kresna SPA ( Stoynov et al 2018b ).…”