Griffon Vulture (Gyps fulvus Hablizl, 1783) is an obligate scavenger, gregarious, soaring over large areas for foraging, cliff dwelling bird of prey, formerly widely spread on the Balkan Peninsula (Balkans), but faced a dramatic decline in 20th century (Cramp and Simmons 1980, Demerdzhiev et al. 2007, Andevski 2013, Demerdzhiev et al. 2014, Botha et al. 2017). As a result of wide-scale campaigns for eradication of predators through the use of poisonous baits, in combination with direct persecution and reduction in available food supplies in some areas, around 1980, the population of the species shrunk to ca. 450 pairs in Greece, mainly in Crete (Xirouchakis and Tsiakiris 2009); ca. 200 pairs in former Yugoslavia; and up to only 10 pairs in Bulgaria, becoming locally extinct in Albania and Romania (Cramp and Simmons 1980). In the beginning of the 21st century, despite the successful conservation of the species in Westren Europe - Spain, Portugal and France, where 90% of the European population currently breeds, Griffon Vulture remained marginal, fragmented and threatened on the Balkans with less than 600 breeding pairs (Botha et al. 2017).

Since the 1980s, due to intensification of the conservation activities in Bulgaria, Serbia, Croatia and Crete, the Griffon Vulture increased locally, although some colonies became deserted (e.g. Bosnia and Herzegovina) or continued to decline, remaining on the verge of extinction, primarily in mainland Greece and North Macedonia (Andevski 2013).

Although the places where the species is, or was until recently, breeding on the Balkan Peninsula are generally known by local conservation groups and presented in various technical reports, official documents and local studies (Andevski 2013, Grubac 2014), the spatial distribution and seasonal territory use patterns of Griffon Vultures are still insufficiently known on a regional level, especially in the light of the urgent need for concentration and proper focusing of specific conservation and management efforts.

The movements of Griffon Vultures have been studied elsewhere (Elosegui and Elosegui 1977, Griesinger 1998, Gil et al. 2009) and by other means also on the Balkans (Xirouchakis and Andreou 2009, Susic 2000, Grubac 2014). Those researchers have used ringing and radio transmitters fitted to single birds; metal and colour ring recovery data and wing tagging have all proven that Griffon Vultures and especially the young individuals carry out long-distance migrations. More recently, GPS-based studies on the local territory use and movements of Griffon Vultures from some countries on the Balkans, similar to studies that have been conducted earlier on the Iberian Peninsula and elsewhere (García-Ripollés et al. 2011, Bahat et al. 2001), have also been published for Greece (Crete) (Xirouchakis et al. 2021), Serbia (Hribsek et al. 2021), Eastern Alps and Croatia (Genero et al. 2020) and Bulgaria (Peshev et al. 2018, Stoynov et al. 2018). However, there is still no comprehensive study and detailed analysis of the use of the entire territory, (cross)movements, spatial behaviour and sojourn patterns of the species from the Balkan Peninsula in a regional context. Such a study would possibly reveal the complete picture and provide answers for a list of conservation problems, such as cross-border and local poisoning of different origin (targeting predators, lead- and drug poisoning etc.), electrocution/collision and habitat degradation, all of which have been explicitly highlighted by Botha et al. (2017) as acting on a large scale and thus harder to control.

Griffon Vulture is listed as "Least concern" globally and in Europe in the IUCN Red List (BirdLife International 2017), because of its wide range and a relatively high population number - a total of 648,000-688,000 mature individuals globally, only 10% of which are in Europe. At the same time, the species is regionally listed in all national Red Data Books across the Balkans as "threatened" (Iankov et al. 2015, Susic 2013) and is an object of conservation interest and efforts. Furthermore, the very fast decline of the vulture populations in India between 1990-2000 (Pain et al. 2008), as well as the continuous decline of the entire group in Africa (Botha et al. 2017) justifies the need for preventative actions, timely research and better understanding of the spatio-temporal patterns and any potential conservation implications on related species.

The aim of the current study is to present and analyse the territory use and sojourn patterns of Griffon Vulture, based on high-resolution GPS tracking for the first time on a regional Balkan Peninsula scale. The home range of the species, its core areas, seasonal sojourn and roosting places are revealed on regional and local level and the conservation implications of these findings are discussed.

In the current study, a total of 51 Griffon Vultures of different ages were equipped with GPS/GSM transmitters in Bulgaria (n = 43), Greece (n = 6) and North Macedonia (n = 2) (Table 1). In order to obtain a more detailed and concise picture, we tagged a total of 20 imported captive individuals, released within local re-introduction projects (Stoynov et al. 2018), a total of 25 wild ones, randomly captured using a hole on the rooftop of existing vulture acclimatisation aviaries (Iezekiel et al. 2003), situated in the areas of Kresna Gorge (UTM FM73), Vrachanski Balkan Nature Park (UTM FN99) and Kotlenska Planina SPA (UTM MH65) in Bulgaria, as well as six individuals, captured in distress in different sites of Greece and North Macedonia and released after rehabilitation.

During the transmitter fitting, the age of the wild-captured birds was determined and recorded by year of hatching using the moulting pattern age determination in Griffon Vulture in line with Zuberogoitia et al. (2013).

The GPS/GSM transmitters (produced by Ornitela UAB - www.ornitela.com) weighed from 30 to 50 g. or < 1% of the body mass of the birds tracked - following the recommendation of < 3% for flying birds (Kenward 2001). The devices were attached either to the birds' lower back by leg-loop harness (OT-30 and OT-50), prepared by three assembled strings (round silicone cord 2 mm + tubular teflon ribbon 0.25" and 0.44") according to Vulture Conservation Foundation (VCF) - internal rules (Daniel Hegglin and Franziska Lorcher - pers. comm.) or pierced to the birds' patagium (OT-P33), together with a vinyl wing-tag. In order to guarantee that the device would fall off in a couple of years, a vulnerable attaching element was deliberately used while fitting. The transmitters were mounted following the best practice in animal welfare - the heads of the birds were covered to ensure minimal stress and the transmitter placement time was reduced to less than ten minutes.

Bird locations were obtained using a global positioning system (GPS), transmitted via a public mobile phone/internet system network (GSM/GPRS). The devices were programmed to save the location data if birds were outside of the coverage area of the given network operator and then to send it once the transmitter was back within range. GPS fixes were acquired every 10 min during the day (between 0500 and 2000 h UTC+2) with dormancy periods during the night. Prior to analysis, the tracking data were inspected and visualised in the Quantum GIS free and open-source cross-platform desktop geographic information system (QGIS.org 2021) to check for outliers and all duplicate coordinates were removed. The data from re-introduced and rehabilitated individuals were used after the 50th day following their release into the wild, to avoid bias due to re-acclimatisation. Only locations taken in the interval between 0600-1800 h UTC+2 within the borders of the Balkan Peninsula were used to determine the home ranges, while the rest of the coordinates in the studied hourly range were used for establishing the roosting sites. The location error was less than 20 m.

Only locations from the Balkan Peninusla and the related areas in the Alps were used in the current study, while location data from the Middle East (movement and sojourn), where some of the tracked birds moved for wintering, were excluded. In addition, birds that were tracked for less than 50 days after release were excluded from further analysis. Data from 48 tracked Griffon Vultures were used for calculations. The information presented and analysed was collected in the period 2016-2021.

The four seasons were defined by the winter and summer solstices and spring and autumn equinox dates. The split aimed at best reflecting the life cycle and foraging and sojourn patterns of the tracked individuals and to distinguish between wintering, summering, spring and autumn migration, seasonal residence and breeding (for the adult birds). If a given vulture had only sent fixings for less than 50% of a particular season (< 45 days), the data of that vulture for that incomplete season were not included in the overall calculations. This was done in order to avoid allocating significance to occasional sites only visited a small number of times yet reflected in the shorter data sample.

Home range estimations

Defining vulture zones in the Balkan Peninsula

Presence and visits of identified vulture zones by different individuals

The results, presented below, are based on a total of 1,138,383 GPS coordinate locations (an average number of 23,716 ± 18,886 positions per bird, range 2,515 – 76,431 of total fixes per bird); and an average of 62.99 fixes per day, collected over a total of 18,072 days (average 376.5 ± 276.12 per bird, range 50 – 1,160), acquired from a total of forty eight Griffon Vultures tracked between January 2016 and March 2021.

Home range estimation

Seasonal home range estimations

Тhe seasonal home range estimations are provided in Table 2. Furthermore, detailed information on the size of the home range of each individual bird for each season is provided as Suppl. material 1.

Table 2.

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Seasonal home range estimations.

Season	Total number of seasons studied for all birds, n	Core area 50%, km2					Home range 95%, km2
		mean	median	st. deviation	min	max	mean	median	st. deviation	min	max
Spring	44	34.8602	8.9035	57.947	1.04	244.085	984.604	508.227	1120.12	14.837	4855.93
Summer	55	26.2727	12.21	37.9947	1.233	193.352	1033.56	696.312	1041.45	110.111	5292.27
Autumn	50	11.5356	6.305	11.7446	0.867	48.415	421.864	225.127	477.72	16.452	2187.2
Winter	56	7.76018	5.1155	9.12612	0.096	44.963	258.682	129.543	298.938	2.1	1256.35

There was a significant difference in the home range sizes amongst the four seasons (F = 11.51, df = 3, p < 0.001; Fig. 1). Post-hoc analysis revealed that home ranges in spring were significantly larger for those in the autumn (p = 0.002) and winter (p = 0.001), but not for those in the summer (p = 0.58). A similar outcome was found for the core areas calculated (F = 5.87, df = 3, p = 0.001; Fig. 2).

Figure 1.  

Seasonal home range 95% area in km² of the Griffon Vulture in the Balkan Peninsula.

Figure 2.  

Seasonal 50% core area in km² of the Griffon Vulture in the Balkan Peninsula.

Defining vulture key zones in the Balkan Peninsula

Our results reveal that Griffon Vulture movement activity and home range size vary considerably throughout the seasons (see Figs 1, 2), especially between their wintering and summering grounds, while exhibiting considerable overlapping amongst the tracked individuals. Specifically, immature Griffon Vultures travel long distances across all Balkan countries, but always gather with conspecifics, showing strong fidelity to active vulture breeding/roosting sites. In addition to that, all tracked birds prefer to either visit or frequently use (> 95% of the time) the same seven general zones on the mainland Balkans we hereby refer to as "vulture key zones" (hereafter VKZ) – one in Serbia (Western Serbia), one shared between North Macedonia and Bulgaria (Struma - Vardar Valleys), one shared between Bulgaria and Greece (Eastern Rhodopes), two lying entirely in Bulgaria (Vrachanski Balkan Nature Park and Eastern Balkan Mountains), one in Greece (Western Greece) and one shared between Kvarner Archipelago islands in Croatia, the Julian Alps - Italy and Slovenia and Hohe Tauern National Park - Austria (Alpo-Adriatic) (Fig. 3).

Figure 3.  

Home ranges 95% and core areas 50%, identifying the Griffon Vulture key zones on the Balkan Peninsula.

Several smaller sub-zones were also defined within the general ones (see Table 3), which might be recognised and managed as actual and potential Vulture Safe Areas (VSA), as proposed in Peshev et al. (2018).

Table 3.

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Griffon Vulture zones on the Balkans, core areas and home range sizes, sub-zones, type of presence and food sources utilised in the given area (based on field observations and available expert data).

Nº	Vulture key zone/ Country	Vultures located in the zone	Area used by vutures, 50% core area, km2	Area used by vutures, 95% Home range, km2	Sub-zone(s) within the main site	Type of presence	Food resources used by vultures - Feeding sites (FS) place/name
1	Alpo - Adriatic, Austria/ Italy/ Croatia	K7A-B5, V3, Y8, (n=3)	291.37	6803,04	Kvarner Archipelago, Croatia (islands of Cres, Krk, Plavnik, Prvich and Pag)	Breeding	Year-round free grazing livestock
					Lago di Cornino Nature Park, Italy	Breeding and summering	Feeding site
					Hohe Tauern National Park, Austria	Summering	Summer livestock grazing
2	Western Serbia, Serbia	56, B69, BY3, K9U, V3, Y1, Y2, Y6, Y8, Y9, (n=10)	190.22	4741.83	Uvats Gorge, Mileshevka Gorge, Treshnitsa Gorge	Breeding, wintering, summering, on passage	Uvats Gorge FS, Treshnitsa Gorge FS, Year-round grazing livestock
3	Vrachanski Balkan Nature Park, Bulgaria	1X, 56, A4, C1-M, C5, F4, F6, P-B2F, XE, Y1, Z7, E1 (n=12)	54.17	2249.32	Vrachanski Balkan	Breeding, wintering, summering, on passage	Vrachanski Balkan FS, Year-round grazing livestock
4	Eastern Balkan Mountain, Bulgaria	1X, B65, H1, K5M, M2, V3, XJ, Y1, Y5, (n=9)	30.416	1171.38	Kotlenska Planina SPA	Breeding, wintering, summering, on passage	Kotel FS, Year-round grazing livestock
					Sinite Kamani Nature Park	Breeding, wintering, summering, on passage	Sinite Kamani FS, Year-round grazing livestock
5	Struma and Vardar Velleys, Bulgaria/ North Macedonia	1H, 2H, 5, 56, A42020, B69, B70-UG, B71-XU, BY1, BY3, BY7, C5, C7, C9, DEFILE, EX, HW, K2M, K9U, OX, V3, V5, V8, W0818, Y1, Y2, Y4, Y5, Y6, Y8, Y9, (n=31)	190.36	7578.93	Kresna Gorge	Breeding, wintering, summering, on passage	Kresna Gorge FS, Year-round grazing livestock
					Pirin National Park	Summering	Summer livestock grazing
					Demir Kapiya, Tikvesh and Mariovo	Breeding, wintering, summering, on passage	Vitachevo FS, Year-round grazing livestock
					Kaymakchalan	Summering	Summer livestock grazing
6	Eastern Rhodopes, Bulgaria/ Greece	1H,1X, 2H,56, A42020, Alexis, B69, BY1, BY7, C5, C7, C9, H1, K9U, P-B2F, V3, V8, W0818, Y1, Y4, Y5, Y9, (n=22)	422.63	8371.15	Dadia, Greece	Breeding, wintering, summering, on passage	Dadia FS, Year-round grazing livestock
					Studen Kladenets, Bulgaria	Breeding, wintering, summering, on passage	Studen Kladenets FS, Year-round grazing livestock
					Madjarovo, Bulgaria	Breeding, wintering, summering, on passage	Madjarovo FS, Year-round grazing livestock
					Kompsatos, Greece	Breeding, wintering, summering, on passage	Year-round grazing livestock
7	Western Greece, Greece	1H, 2H, 56, Alexis, C9, GD-22, GS, K3A-B2, K7A-B5, OX, (n=10)	363.54	7242.78	Akarnanika Mts/ Messolonghi/Embesos	Breeding, wintering,	Winter livestock grazing livestock
					Pindus Mts	Summering, on passage	Summer livestock grazing

1. Alpo-Adriatic Zone

The VKZ extends beyond the borders of the Balkan Peninusla. It is shared amongst Croatia, Italy, Slovenia and Austria (see Fig. 4) with several centres - Lago di Cornino Nature Reserve (N46.22, E13.02, Italy), where Griffon Vulture has been re-introduced and started breeding in the 1990s (Mihelic and Genero 2005), the Kvarner Archipelago (North Adriatic) - islands of Cres, Krk, Plavnik, Prvich and Pag (N44.98, E14.40, Croatia), Hohe Tauern National Park (N47.14, E12.85, Austria) with some extentions towards the Triglav National Park (N46.36, E13.55, Slovenia) - also reported by Mihelic and Genero (2005) and Genero et al. (2020). The 50% core area of the zone is 291.37 km² and the 95% home range is calculated at 6,803.04 km² (based on the location data of three tracked birds). The sample of tracked birds for this VKZ is small and, although our findings are supported from previously-gathered data (Goran Susic - pers. comm.), but also published studies (Genero et al. 2020), additional research is necessary. A vulture feeding site was operating regularly in Lago di Cornino National Park, Italy and occasionally on the Island of Cres, Croatia, throughout the study period. The active Griffon Vulture breeding colonies within the zone are located in Lago di Cornino in Italy and on the Kvarner Archipelago (North Adriatic) in Croatia (Islands of Cres, Krk, Plavnik, Prvich and Pag).

Figure 4.  

Seasonal home ranges in the Alpo-Adriatic Griffon Vulture key zone.

2. Western Serbia

This VKZ lies entirely in Serbia (Fig. 5), centred at the towns of Nova Varos and Sienica along the Uvats River (N43.42, E19.93) and the Treshnitsa River (N44.14, E19.54) where the breeding colonies are. The Griffon Vulture 50% core area, estimated for the zone, is 190.22 km², with a home range of 4,741.83 km² (based on the location data of a total of 10 tracked birds), values above the mean for the Balkan Peninsula. Regular feedings with several tens to hundred of tonnes of slaughter offal/cattle carcasses per year were provided in Uvats Gorge, as well as some less regular feedings were also carried out in Treshnitsa and Mileshevka Gorges (Marinković et al. 2020) during the study period. From the beginning of 2020, another feeding site started operating more to the south - in the area of Pester Plateau Special Nature Reserve, but that one works irregularly.

Figure 5.  

Seasonal home ranges in the Western Serbia Griffon Vulture key zone.

3. Vrachanski Balkan Nature Park

This VKZ lies entirely in Bulgaria (Fig. 6), centred near the town of Vratsa (N43.19, E23.52), where active Griffon Vulture breeding colonies were established, following a successful re-introduction project started in 2010. A vulture feeding site, providing some 45-60 tonnes over 200 feeding occasions per year, was operating during the study period near the village of Dolno Ozirovo (N43.25, E23.37). The 50% core area of Griffon Vulture in the zone was estimated at 54.17 km² and the 95% home range is 2,249.32 km², based on the location data of a total of 10 tracked birds.

Figure 6.  

Seasonal home ranges in the Vrachanski Balkan Nature Park Griffon Vulture zone.

4. Eastern Balkan Mountains

This VKZ lies entirely within Bulgaria, centred at the towns of Kotel (N42.88, E26.44) and Sliven (N42.70, E26.34) (Fig. 7), where several small Griffon Vulture breeding colonies were established, following a series of re-introduction projects started in 2010 (Kmetova–Biro et al. 2021). Two vulture feeding sites, each providing some 30-40 tonnes within more than 150 feeding events per year were operating during the study period - one near Kotel (N42.92, E26.46) and another in the Sinite Kamani Nature Park near the town of Sliven (N42.73, E26.30). The Griffon Vulture 50% core area of the zone was calculated at 30.42 km² and the 95% home range at 1,171.38 km² (based on the location data of a total of 22 tracked birds), representing the smallest vulture ranges found on the Balkan Peninsula.

Figure 7.  

Seasonal home ranges in the Eastern Balkan Mountains Griffon Vulture zone.

5. Struma and Vardar Valleys

This VKZ is shared between North Macedonia and Bulgaria (Fig. 8), with two centres - Tikvesh area around the town of Kavadartsi - autochthonous colonies (N41.26, E21.96, North Macedonia) and the Kresna Gorge (N41.79, E23.14, Bulgaria), where Griffon Vulture has been successfully re-introduced since 2010 (Peshev et al. 2019). The ranges extend in summer to the high mountain pastures in the area of Kaymakchalan on the border of Greece and North Macedonia (N40.92, E21.78) and Pirin National Park (N41.71, E23.43) in Bulgaria. The 50% core area of the species is calculated at 190.36 km² and the 95% home range is 7,578.93 km² (based on the location data of a total of 31 tracked birds). These are amongst the largest values on the Balkan Peninsula, while at the same time, the zone hosts the smallest number of breeding pairs and constantly-present individuals. Two feeding sites were operating throughout the study period - some 45-60 tonnes of food within more than 200 feeding events per year were provided in Kresna Gorge, Bulgaria (N41.84, E23.16); while some 30-50 feedings with a total of 3-5 tonnes of food per year were occasionally provided in Vitachevo area, North Macedonia (N41.31, E22.50).

Figure 8.  

Seasonal home ranges in the Struma and Vardar Valleys Griffon Vulture key zone.

6. Eastern Rhodopes

This VKZ is shared between Bulgaria and Greece, centred at the breeding colonies around Studen Kladenets (N41.64, E25.52) and Madjarovo (N41.65, E25.87) in Bulgaria and the Dadia-Lefkimi-Soufli Forest National Park (N41.09, E26.14) and Kompsatos river valley (aka Tracian Metora) (N41.22, E25.15) in Greece. Our location data show that the area around the village of Esochi, Greece (N41.23, E25.77) is more frequently visited for foraging in spring and summer. The 50% core area of the Griffon Vultures in this zone was calculated at 422.63 km² and the 95% home range at 8,371.15 km² (based on the location data of a total of 31 tracked birds), both being the largest estimated on the Balkan Peninsula (Fig. 9). Here, several vulture feeding sites were operating throughout the study period - two in the area of Studen Kladenets (N41.59, E25.64 and N41.62, E25.53), one near Madjarovo (N41.64, E25.87) in Bulgaria and one in Dadia-Lefkimi-Soufli Forest National Park (N41.10, E26.24), each supplied with several tens of tonnes of food per year with a frequency of at least once a week (Arkumarev et al. 2021). Lately, some GPS-tracked Griffon Vultures started visiting the old known breeding site in Nestos Gorge, which was abandoned in 2012 (Andevski 2013), but just recently, a small group with at least one breeding pair recolonised it (Lavrentis Sidiropoulus, pers. comm.) and eventually started to attract migrants and roaming individuals.

Figure 9.  

Seasonal home ranges in the Eastern Rhodopes Griffon Vulture zone.

7. Western Greece

This VKZ lies in south-western continental Greece, with three centres - at Messolonghi (N38.50, E21.37), Akarnanika Mountain (N38.74, E20.95) and Embesos (N38.99, E21.34), where local breeding colonies and related wintering sites for vultures from across the Balkan Peninsula are found. The birds were found to move to high mountain pastures of Pindus Mountains with centres in Agrafa (N39.14, E21.69), Tzumerka (N39.44, E21.21) and Karpenisi (N38.94, E21.80) in the summer. The total Griffon Vulture core area 50% of the zone was estimated at 363.54 km² and home range 95% of 7,242.78 km² (based on the location data of a total of 10 tracked birds) being the second largest in the Balkan Peninsula during the study period (Fig. 10). No vulture feeding site was operating in the area during the study period.

Figure 10.  

Seasonal home ranges in the Western Greece Griffon Vulture key zone.

Presence and visits of the respective key vulture zones by different individuals

The present research reveals seven well-distinguished key zones for the remnant and locally-re-introduced nuclei of the Griffon Vulture population on the Balkan Peninsula, clearly outlined by the analysis of the collected telemetry data. The monitored individuals spent virtually the whole period of the research (> 95%) in one or more of those seven key zones or in targeted movements between them, demonstrating an extremly high preference for those environmentally suitable areas, involving also species with strong social interactions.

All of the seven identified Griffon Vulture zones on the Balkans offer similar key benefits for the vultures - suitable breeding/roosting sites with gorges, ravines and cliffs nearby; extensive summer and winter pasturelands; presence of conspecifics and all, but Western Greece, have actively managed vulture feeding stations. The seven key zones form a coherent network and are used as stepping-stones for Griffon Vultures during their migration movements and roaming, but also wintering and summering.

The obtained results are of crucial importance for the conservation of the species on the Balkans as they show that the wide range of management efforts could be specifically targeting particular core areas. The knowledge that social scavengers, such as Griffon Vulture, could be spatially concentrated and could be used elsewhere to precisely target adequate management efforts in space and time.

The telemetry-based conclusions are directly related to the concept of VSA and support the urgent need to actively monitor, control and mitigate all risk factors (such as poisoning, electrocution, collision, poaching etc.) and prevent habitat deterioration (e.g. large scale wind farm development, pastureland abandonment) in these well-defined key zones. This is likely the most cost-effective strategy for the conservation of all vulture species during the human-dominated present (the so-called Anthropocene) on the Balkan Peninsula and elsewhere.

The knowledge of the key characteristics of the present Griffon Vulture key zones, identified in Southeast Europe, will assist the potential establishment of new ones, where colonies of the species have existed in the near past. This could help to further increase the coherence of the network of vulture key zones and facilitate the natural dispersal of the metapopulation, lowering the conservation risks in all remaining single sites.

The study was carried out within the Life for Kresna Gorge LIFE11NAT/BG/363 project of the Fund for Wild Flora and Fauna (2012-2016); the Vultures Return in Bulgaria LIFE08NAT/BG/278 project of Green Balkans and FWFF in Vrachanski Balkan Nature Park and the Eastern Balkan Mountains (2010-2014) and the Vultures Back to Life LIFE14NAT/BG/649 project (2015-ongoing), all of which co-financed by the LIFE financial instrument of EC.

Some of the GPS/GSM transmitters and part of the study and its publication were financially supported by the Whitley Fund for Nature (https://whitleyaward.org/) through the project "Saving the last vultures in Balkans introducing Vulture Safe Areas as a model for scavengers conservation in the Anthropocene".

In addition to that, some GPS/GSM transmitters were purchased within the Balkan Against-poison Project of Vulture Conservation Foundation with the support of MAVA Foundation.