# Long-distance post-release movements challenge the metapopulation restoration of Bearded Vultures

Cécile Tréhin, Olivier Duriez, François Sarrazin, Benoit Betton, Jocelyn Fonderflick, Franziska Loercher, Etienne Marlé, Jean-François Seguin, Julien Traversier, Noémie Ziletti, et al.

► To cite this version:

Cécile Tréhin, Olivier Duriez, François Sarrazin, Benoit Betton, Jocelyn Fonderflick, et al. Long-distance post-release movements challenge the metapopulation restoration of Bearded Vultures. Ecosphere, 2024, 15 (8), pp.e4856. 10.1002/ecs2.4856. hal-04768641

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ARTICLE

Macrosystems Ecology

# Long-distance post-release movements challenge the metapopulation restoration of Bearded Vultures

Cécile Tréhin<fnref n="1" />,<fnref n="2" />,<fnref n="3" /> ID | Olivier Duriez<fnref n="4" /> ID | François Sarrazin<fnref n="1" /> ID |

Benoit Betton<fnref n="5" /> | Jocelyn Fonderflick<fnref n="6" /> | Franziska Loercher<fnref n="7" /> |

Etienne Marlé<fnref n="8" /> | Jean-François Seguin<fnref n="9" /> | Julien Traversier<fnref n="10" /> |

Noémie Ziletti<fnref n="11" /> | Jean-Baptiste Mihoub<fnref n="1" /> ID

**Correspondence**

Jean-Baptiste Mihoub
Email: jean-baptiste.mihoub@mnhn.fr

**Funding information**

LIFE, Grant/Award Numbers: NAT/
FR/000050, NAT/FR/101074131;
BiodivRestore ERA-NET, Grant/Award
Number: 101003777

**Handling Editor:** Jeffrey F. Kelly

**Abstract**

Restoring ecological dynamics is a key objective of conservation translocations. Exemplarily, reconnecting the reintroduced alpine populations with native Pyrenean populations through re-establishing locally extinct populations in between, in the Causses and the Pre-Alps, is a major goal for the long-term conservation of Bearded Vultures in Europe. Understanding Bearded Vultures' post-release movements and foraging behavior is critical to understanding the settlement of newly restored populations and to supporting conservation measures. The telemetric monitoring of 43 translocated and wild-born juveniles allowed us to investigate whether differences exist in post-release movements and foraging behavior during the first year of life between reintroduced and native populations. Medium- and long-distance exploration movements start during the spring following fledging for both translocated and wild-born individuals. However, birds translocated in the most distant release site (Causses) exhibited greater exploration distances with no clear directional movement pattern, had smaller home ranges, and had a stronger preference for supplementary feeding stations than those from other populations. Although some

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

© 2024 The Authors. Ecosphere published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

<footnote n="1">¹Centre d'Ecologie et des Sciences de la Conservation (CESCO), Sorbonne Université MNHN, CNRS, Paris, France</footnote>

<footnote n="2">²U3E (Ecology and Ecotoxicology Experimental Unit), INRAE, Rennes, France</footnote>

<footnote n="3">³INRAE, pôle OFB-INRAE-Institut Agro-UPPA MIAME-Management of Diadromous Fish in their Environment, U3E, Rennes, France</footnote>

<footnote n="4">⁴CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France</footnote>

<footnote n="5">⁵Parc Naturel Régional du Vercors, Lans-en-Vercors, France</footnote>

<footnote n="6">⁶Parc National des Cévennes, Florac, France</footnote>

<footnote n="7">⁷Vulture Conservation Foundation (VCF) and International Bearded Vulture Monitoring (IBM), Zurich, Switzerland</footnote>

<footnote n="8">⁸Aster, Conservatoire des Espaces Naturels – Haute-Savoie, Antenne de Sallanches, Sallanches, France</footnote>

<footnote n="9">⁹Syndicat mixte du Parc naturel régional de Corse, Maison des Services publics, Corte, France</footnote>

<footnote n="10">¹⁰Association Vautours Baronnies, Rémuzat, France</footnote>

<footnote n="11">¹¹Ligue de Protection des Oiseaux (LPO Grands Causses), Le Bourg, Peyreleau, France</footnote>
birds translocated in the Pre-Alps displayed similar behaviors, the pattern is not as strong as in the Causses, likely because of the proximity to the breeding populations reintroduced in the Alps or differences in the number and management of supplementary feeding stations. Preference for supplementary feeding stations (SFS) mostly occurred in the Pre-Alps and the native populations, but was lower in the Causses. Seasonal variations in SFS preference were consistent among populations, with a peak in the first spring following fledging. Beyond documenting post-release movements in Bearded Vultures, we suggest better accounting for the demographic consequences of behaviors to track conservation translocation effectiveness, at both local and regional scales.

### KEYWORDS

establishment phase, exploration movements, foraging behavior, *Gypaetus barbatus*, reintroduction, satellite telemetry

## INTRODUCTION

Conservation translocations such as reintroductions aim to enhance long-term species viability and restore ecological processes by releasing organisms into the wild (Sarrazin & Barbault, 1996; Seddon et al., 2014). Aiming at re-establishing extinct populations locally and then reengaging demographic and genetic flows through dispersal at wider spatial scales, metapopulation restoration simultaneously targets these two objectives. Yet, initial dis-equilibrium characterizing the establishment phase of translocated populations may lead to unusual post-release movements such as exacerbated exploration behavior or long-distance dispersal (Le Gouar et al., 2012; Mihoub et al., 2009, 2011). Without necessarily implying increased mortality, the frequency and the magnitude of post-release movements can severely impact the establishment or the growth of reintroduced populations (Mihoub et al., 2009, 2011), potentially leading to local reintroduction failures and overall challenging the success of metapopulation restoration (Le Gouar et al., 2008). Foraging or breeding behaviors are particularly important to consider because they represent key drivers of post-release movements in many animals. Better understanding of factors triggering post-release movements is therefore key to inform on the establishment probabilities of focal reintroduced populations as well as on the potential for future connections within a metapopulation, especially in species with long-distance movement abilities.

In birds, raptors and especially vultures are among the most threatened avian guild, and the observed global decline of these strict scavengers largely results from increased nonnatural mortality due to anthropogenic activities (Safford et al., 2019). Formerly widespread in western

Europe, Bearded Vulture (*Gypaetus barbatus*) populations were extirpated from the Alps at the end of the 19th century because of human persecutions (Mingozzi & Estève, 1997), and only two small native populations remained in Pyrenees and Corsica. An international reintroduction program of captive-bred birds started in 1986 led to the establishment of a fragmented population in the eastern and the central Alps (Schaub et al., 2009). However, the viability of the alpine population remains fragile, suffering from low genetic diversity and continued isolation from the larger and native Pyrenean population. In order to reconnect these two populations, a reintroduction program was launched in 2010 in the French Pre-Alps (Vercors) and another in 2012 in the Massif Central (hereafter Causses). Together with the creation of a network of supplementary feeding stations (SFS) between the Pyrenees and Causses and between Causses and Pre-Alps, these reintroduction programs were strengthened to restore these populations.

Because of the very late access to reproduction in this species (first breeding attempts at 8 years on average in the wild; Antor et al., 2007), it is to date too early to assess the success of this program by estimating breeding dispersal and establishment of translocated birds effectively. Nevertheless, studying post-release movements and foraging habitat use of translocated Bearded Vultures can provide essential information for evaluating the potential for establishing new population core and dispersal processes expected within the metapopulation, and eventually help revise the implementation of the reintroduction programs adaptively.

In raptors, movement patterns are quite consistent with respect to age, with young moving more frequently and at greater distances than adults (e.g., Cinereous Vulture [*Aegypius monachus*], Reading et al., 2020; Golden
Eagle [*Aquila chrysaetos*], Sur et al., 2020). Likewise, territorial individuals usually show more restricted movements than non-territorial ones, which wander widely (Spanish Imperial Eagle [*Aquila adalberti*], Fernández et al., 2009; Golden Eagle, Moss & Hipkiss, 2014; Bearded Vulture, Margalida et al., 2016; Cinereous Vulture, Reading et al., 2020; Cape Vulture, Martens et al., 2018). However, sex-specific movements are more inconsistent across or within species, reflecting complex interactions between internal factors such as territorial (breeding) status (e.g., in Bearded Vulture) and/or external factors related to environmental characteristics (e.g., Golden Eagle; White-tailed Eagle [*Haliaeetus albicilla*], Engler & Krone, 2022). In birds, females generally move more often and farther than males (Greenwood, 1980), such as in nonterritorial Eurasian Griffon Vulture, *Gyps fulvus* (Morant et al., 2023; Spiegel et al., 2015), Bearded Vulture (García-Jiménez et al., 2018), and Osprey, *Pandion haliaetus* (Monti et al., 2014), and usually have larger home ranges (e.g., territorial Bearded Vulture, Margalida et al., 2016). However, some species did not show any sex differences for nonterritorial individuals in the distance moved (e.g., Spanish Imperial Eagle, Morandini et al., 2020; Morandini & Ferrer, 2017; Muriel et al., 2016) or home range sizes (Cinereous Vulture, Carrete & Donázar, 2005; Golden Eagle, Moss & Hipkiss, 2014). In the same species, a sex-biased dispersal is observed in some populations but not in others (White-tailed Eagle, Engler & Krone, 2022; Rymešová et al., 2021). And in some cases, males have even been reported to move more than females (territorial and nonterritorial Golden Eagle, Sur et al., 2020; nonterritorial Bearded Vulture, Margalida et al., 2016). Besides, beyond mere differences between individuals or habitat suitability in terms of breeding site or food availability, public information such as the presence of conspecifics is also known to be a major driver in habitat selection (Danchin, 2004). Conspecific attraction can indeed affect exploration and dispersal behaviors in raptors. Translocated Spanish Imperial Eagles released in areas without adults moved greater distances than wild-born or juveniles released in areas with adults (Morandini & Ferrer, 2017) and showed earlier and increasing exploration movements as they matured despite being initially philopatric (Muriel et al., 2016). In Bearded Vulture, breeding establishment was promoted in areas already occupied by congeners (Margalida et al., 2013), and such behavioral mechanism may have led to the local establishment failure of reintroduced populations (Eurasian Griffon Vulture, Le Gouar et al., 2008). Therefore, despite Bearded Vultures being mostly philopatric (Jenny et al., 2018), translocated individuals may not be as faithful to their reintroduction site as wild-born individuals are to their natal population.

The purpose of this study is to test the homogeneity of post-release movement behaviors among wild-born and translocated juvenile Bearded Vultures and to carry out a detailed analysis on (1) the phenology of their post-fledging exploration movements, (2) the quantification of space use through home ranges, and (3) their foraging habitat use. This study relied on GPS tracking data collected from captive-bred birds translocated during two reintroduction programs (Causses and Pre-Alps) and from wild birds fledged in native populations (French Pyrenees and Corsica) or from the population reintroduced in the Alps (Haute-Savoie). Specifically, we aimed to determine whether internal factors such as sex or birth origin (translocated captive-bred or wild-born) or external factors related to the local characteristics of the geographical region of fledging affect post-release movement behaviors. We hypothesized that post-release behaviors of juvenile Bearded Vultures would differ between populations with respect to distance from the nearest established populations due to the effect of conspecific attraction or food availability. We expect individuals translocated in locations distant from established populations to display more exploration behaviors and to move greater distance than wild-born individuals. Home range sizes may also be smaller in areas with a dense network of SFS, providing an abundant and somewhat predictable food resource that may reduce movements, as reported for Eurasian Griffon Vultures (Fluhr et al., 2021; Morant et al., 2023) and for Bearded Vultures (Margalida et al., 2013). In addition, we suspect the phenology of exploration behaviors and home range sizes to be season-dependent, with lower movements during winter as in other soaring raptors (Gavashelishvili et al., 2012; Hiraldo & Donázar, 1990; Reading et al., 2020; Sur et al., 2020). These movement patterns will be discussed in line with those predictions as well as regarding the outcomes of such translocations for restoration potential of the metapopulation of Bearded Vultures in Europe.

# METHODS

## Study species

The Bearded Vulture is a long-lived raptor with late maturity (>5 years) and low fecundity (max 1 fledgling per year), compensated by high survival probability (Margalida et al., 2020). It feeds almost exclusively on bones from carcasses of wild and domestic ungulates (Roselaar, 1980). As this resource is spatially and temporally unpredictable, Bearded Vultures can travel great distances daily within their home range seeking carcasses, especially nonterritorial individuals (García-Jiménez et al., 2018). Breeding adults are territorial (Margalida et al., 2013) and build their nests in steep cliffs (Hirzel
<figure><img src="image_2.png" /><figcaption>**FIGURE 1** Legend on next page.</figcaption></figure>
et al., 2004; Margalida, Donázar, et al., 2008). Hatching generally occurs in February–April, and fledging in June–August (Roselaar, 1980).

## Current distribution and conservation actions

In 1960, the distribution in western Europe was restricted to less than 50 pairs in Spain (Andalucia and the Pyrenees) and Corsica. In the Pyrenees, legal protection and the implementation of SFS (see below) allowed the population to increase from 45 pairs in 1987 to 164 pairs in 2016 (Margalida et al., 2020). In Corsica, besides protection and a network of 10 SFS, the population continuously declined and counted five pairs in 2018 (Seguin et al., 2010). In the central-eastern Alps, reintroductions of captive-bred birds started in 1986 and restored a population that counted 66 laying pairs in 2023 (International Bearded Vulture Monitoring, IBM). The Alpine population is composed of four distinct nuclei: one in the Southern Alps between France and Italy (Mercantour-Argentera), one between France, Switzerland, and Italy (around Mont-Blanc), one between Switzerland and Italy (Grison-Stelvio National Park), and the last one in Austria (Hohe Tauern National Park). Even though Bearded Vulture is listed as “Near Threatened” at the global and European scale on the IUCN Red List (2021a, 2021b), the species is “Endangered” in France (IUCN France et al., 2016). Major threats are low genetic diversity due to population declines or extinctions over past centuries, illegal poisoning and lead intoxication, mortality by collision on power lines, direct persecutions, as well as other anthropogenic disturbances and habitat degradation (Margalida, Heredia, et al., 2008).

Reintroduction in the Pre-Alps and Causses started in 2010 and 2012, respectively, and were later coordinated by the EU LIFE Gypconnect program (https://webgate.ec.europa.eu/life/publicWebsite/project/LIFE14-NAT-FR-000050/restoration-of-connections-between-the-alpine-and-pyrenean-populations-of-bearded-vulture-gypaetus-ba-rbatus) (Figure 1). Two to five birds have been translocated each year between 2010 and 2021 at each release site through the hacking method: captive-bred juveniles were placed into an artificial nest at the release site 1 month before the fledging date. In Corsica, similar

translocations of two juveniles per year have been conducted between 2016 and 2020.

At all sites, Bearded Vultures were able to feed at “true” SFS dedicated to them, specifically provisioned with bones (Duriez et al., 2022). In Causses and Pre-Alps, Bearded Vultures could feed at a widespread network of SFS, combining “true” SFS but also at more numerous “recycling feeding stations” provisioned with entire carcasses for the whole scavenger bird community (Duriez et al., 2022). In Corsica, nine SFS are provisioned with bones of domestic ungulates all year round, and 15 SFS are provisioned from November to May in the French Pyrenees, in addition to 6 SFS created in Aude (eastern Pyrenees), as well as 22 SFS in the Spanish Pyrenees (see details in Appendix S1).

## GPS tracking

Each bird was fitted with a GPS tag, fixed with a nonabrasive Teflon harness, attached using a leg-loop technique (Anderson et al., 2020). The mass of the tags ranged from 35 to 85 g (<1% of bird mass). The monitoring starting date was set at the fledging date. Overall, we used more than 750,000 GPS locations from 43 Bearded Vultures fledged from five regions in France (37 translocated captive-bred and 6 wild-born birds; see Figure 1). All GPS tags were powered by solar panels allowing multiyear monitoring. Data were automatically transmitted by the mobile phone network (GSM) and stored in the study named “Bearded Vulture in France – National Action Plan” in www.movebank.org database.

Though the monitoring covered a period from 2007 to 2018, the monitoring duration for each individual varied from 1 month to more than 4 years after fledging (Appendix S2: Figure S1). Monitoring stopped either because of the death of the bird, tag loss, or failure. Although most tags were programmed to record GPS positions at 1-h intervals (n = 21), others were set at intervals of a few minutes (n = 11), or to 2 or 4 h (n = 10) or even 1 day (n = 1). Moreover, for a given bird, the GPS interval could vary according to the battery charge level.

## Analyses of exploration movements

Exploration movement behaviors can vary between populations and among individuals within a population

**FIGURE 1** Study regions, translocation efforts, and tracks of Bearded Vultures monitored. (A) Geographical delimitations of study regions, with respect to the number of individuals monitored and their birth origin (W, wild-born; R, released captive-bred for translocation), the overall tracking period, and the total area of the region. (B) Tracks of Bearded Vultures monitored according to their region of fledging.
(Minderman et al., 2009). Bearded Vulture movements monitored in our study fall along a continuum, from very restricted movements around fledging site (release or nest location) to quite extensive movements of thousands of kilometers away (see movement tracks in Figure 1). Resident behavior can be described by the ordinary, sedentary movements an individual performs within a known and nonrisky environment (Réale et al., 2007), whereas exploration behaviors can be identified using criteria such as larger distance or speed, more linear trajectory, or higher proportion of (new) environment explored (Minderman et al., 2009; Nilsson et al., 2014). A critical step in our analysis was therefore to characterize and discriminate residence and exploration periods in a way that would be relevant at each individual scale and consistent among individuals.

To that end, we combined two methodological approaches by coupling a net square displacement (NSD) analysis with a trajectory segmentation analysis, as neither of the two methods alone would allow satisfactory discrimination of the different movement periods (Soriano-Redondo et al., 2020). The NSD analysis is a powerful approach for quantifying the expansion of the explored area in time and space using tracking data, based on the Euclidian distance traveled from the first location (release site or nest in our

study) and all subsequent locations (Bastille-Rousseau et al., 2016; Bunnefeld et al., 2011). However, it does not allow identifying when distinct movement periods started or ended (Soriano-Redondo et al., 2020), especially in cases in which movements are slow and gradual over space (Figure 2; see also Appendix S3: Section S1). In contrast, the trajectory segmentation analysis enables discriminating distinct movement periods by classifying homogeneous segments of movements based on relative behavioral changes within the trajectory of each individual (Lavielle, 1999, 2005), but fails to account for scaling issues of distances resulting from interindividual variations (see also Appendix S3: Section S2).

To address these issues, we defined criteria and respective thresholds for each methodological approach. Based on the NSD method, we calculated NSDmax as the maximum absolute square distance between the fledging point and the furthest location ever reached by the bird within the period considered, in order to set an absolute distance threshold among individuals (see Appendix S3: Section S1 for details). Based on the segmentation analysis, we calculated the distance between the current location and the location 3 days earlier (Dx3) to detect reliable behavioral change. We then retained the maximum Dx3 over the entire monitoring period (Dx3-max) for each individual in

<figure><img src="image_3.png" /><figcaption>**FIGURE 2** Evolution of median net square displacement (NSD) scaled from the first spring after fledging until the end of the second year for all individuals, with respect to their region of fledgling. Note that the x-axes begin in May, which represents the first year after fledging. Individual paths are shown by the dashed gray line and mean population path is shown by a black solid line. Values close to 0 correspond to displacements near to the starting location (release or nest site) while greater values correspond to farther displacements.</figcaption></figure>
order to set absolute thresholds of behavior change shared by all birds (see Appendix S3: Section S2 for details). Using the distribution Dx3-max and NSDmax obtained across all individuals (Figure 3A,B), we finally identified three categories of exploration statuses: “resident,” “medium-distance exploration,” and “long-distance exploration” (Figure 3C). Thresholds used to split the categories were chosen according to biological relevance as well as to get a balanced sample size of individuals between the exploration categories.

To investigate whether exploration movement behaviors changed with age, the exploration status of

each bird was characterized at three time intervals: from fledgling to 6-month-old (0.5 year), from fledgling to 1-year-old, and from fledgling to 1.5-year-old. The status of “medium-distance explorer” and “long-distance explorer” was respectively assigned if the bird had made at least one medium-distance or one long-distance exploration trip during this period (“long-distance explorer” prevailing over “medium-distance explorer”). Other birds were considered as resident. When monitoring stopped before the end of a given time interval, the most distant movement status traveled so far was retained.

<figure><img src="image_4.png" /><figcaption>**FIGURE 3** Categories of exploration movement status based on maximal distance traveled over three consecutive days (Dx3-max) used in the trajectory segmentation analysis and maximal net square distance from fledging site (release or nest location) over the monitoring duration (NSDmax). (A) Distribution of Dx3-max and (B) NSDmax values reached 1 year after the post-fledgling period by each bird tracked (N = 18) and exploration thresholds considered to distinguish exploration movement status (respectively, A1 = 150 km and A2 = 300 km; B1 = 40,000 km² and B2 = 120,000 km²). (C) Exploration statutes according to Dx3-max and NSDmax thresholds are resident (green), medium-distance explorer (orange), and long-distance explorer (red). See Appendix S3 for details.</figcaption></figure>
We tested the effects of sex and region of fledging (geographic population) on (1) the exploration statuses by applying Fisher's exact tests on the proportion of birds within each exploration category; (2) the phenology of the exploration considering both the departure date of the first exploration and the duration of the exploration periods using linear models checking homoscedasticity and normality assumptions. For these two metrics of exploration phenology, we also tested the difference between “medium-distance explorer” and “long-distance explorer.” For each bird, the maximum distance from the first location reached 1 year after fledging (Dmax-1y, obtained from the square root of NSDmax) was also examined using the same factors in order to refine the differentiation of the exploration behaviors using a quantitative approach. We only considered the 1-year period after fledging because the exploration status mostly changed between 6 months and 1 year and not much afterward, and the number of birds monitored was dramatically reduced after this duration (see Results). For this analysis, log transformation was used after checking the normality and homoscedasticity of the residuals. We standardized all factors (region, sex, and exploration status) using the *standardize* function in R (package *standardize*, Eager, 2022) that places all variables (both numeric and categorical, based on contrast matrices) on the same scale based on a model formula. Additionally, we reported effect size by providing partial eta-squared coefficients ($\eta^2$) and associated 95% CI, which reflects the percent of the variance explained by a factor while accounting for other factors, using the *eta_squared* function from the *effectsize* library in R (Ben-Shachar et al., 2020).

Although the location time series of each individual can represent several thousand data points, the small number of individuals monitored imposed a restriction on the number of effects to be tested to maintain statistical power and robustness. Consequently, some regions had to be pooled in order to limit the number to four treatments for this factor: Causses, Pre-Alps (Baronnies and Vercors), mountains (Mercantour, Haute-Savoie, Pyrenees), and Corsica. Moreover, we did not conduct formal statistical tests on the effect of birth origin (wild-born vs. translocated captive-bred) because of the very low number of wild-born individuals and the strong unbalance in comparison to translocated captive-bred individuals (N = 37), as well as the strong correlation between birth origin and region of fledging ($\chi^2_3$ = 9.24, *p* = 0.026). Rather, birth origin was conducted through visual inspection of the graphical representation.

## Analyses of home ranges and foraging habitat selection

We calculated the home range sizes for each bird during residence periods lasting >30 days over their entire monitoring period as well as within five particular seasons based on solstice and equinox dates (first summer, first autumn, first winter, first spring, second summer), to determine whether seasonal differences occurred due to variations in trophic or climatic conditions and whether home range size changed with age. We used the fixed kernel method (*adehabitatHR* package available with R; Calenge, 2006) to estimate a utilization distribution (UD). Conventionally, the area where animals concentrate 95% of their activities (UD95) was used to represent the home range while the area where animals concentrate 50% of their activities (UD50) was defined as the core area. Because fixed kernel methods assume that the locations are independent (i.e., low temporal or spatial autocorrelation), we subsampled the datasets that considered only one position per hour for birds tracked for a time interval <1 h. For birds tracked for a time interval >1 h, we checked that the resulting home ranges remained in the variation range of the other individuals. The UD function was estimated in each pixel of a raster grid. As the estimation of UD function is not very sensitive to the resolution (Silverman, 1986), we chose a resolution of 250 × 250 m, corresponding to the resolution of the habitat map used for habitat selection analyses. For robustness, the calculation of home ranges was done only if at least 30 locations were available (Seaman et al., 1999).

Considering both metrics UD95 and UD50, we also investigated (1) whether a bird retained the same home range size before and after an exploration movement, and (2) whether home range sizes were different, be it due to a change in home range within its region of fledging or rather due to a settlement in another region. For medium-distance and long-distance explorers, we calculated home ranges during (1) the month before departure and the month following establishment in a new residence period in (2) the same region or (3) in another region. The effect of season, sex, birth origin, and region of fledging on home range sizes was analyzed using a generalized linear mixed model (GLMM, package *nlme*, Pinheiro et al., 2017) with Gaussian distribution and accounting for repeated measurements on the same individual as random effect. Again all factors were standardized using the *standardize* function in R (package *standardize*, Eager, 2022), and effect size was also reported using partial eta-squared coefficients and associated 95% CI as previously described (Ben-Shachar et al., 2020).
The selection of foraging habitats was analyzed using resource selection functions (RSFs) with random effects on individual identity following the method of Muff et al. (2020) and Northrup et al. (2022). These functions allow for assessing the probability that the individual will use a specific habitat, taking into account the proportion of that habitat within its environment. RSFs allow the comparison of observed locations associated with each type of habitat with a set of locations assumed to be available to the individuals (randomly sampled within their environments). We considered four habitat categories. Three habitat categories were identified from a reclassification of the 44 habitat categories (label 3) of the Corine Land Cover 2012 (European Environment Agency—250 × 250 m): (1) “open habitats” supposedly favorable to forage (Hirzel et al., 2004), (2) “closed habitats” assumed to be less favorable (due to reduced visibility below trees), and (3) other habitat types (see Appendix S4: Table S1 for details about the grouping of CLC label 3). A buffer zone of 1 km around SFS locations has been used as a fourth habitat category to assess the effective use of SFS by Bearded Vultures.

Habitat selection analysis was performed using the *glmmTMB* function in R (package *glmmTMB*), allowing the fit of a GLMM using Template Model Builder (TMB), which is well-suited to fitting complex spatiotemporal models and adapted for RSF analyses (Muff et al., 2020). We inferred the foraging behavior of birds from this habitat selection analysis within their home ranges. For each individual, random points were generated using the *random_point function* in R (package *amt* version 0.1.7) within its home range (UD95), with a ratio of 10 random available locations to 1 observed location. Random points and observed locations were used as response variables in the RSF analysis to quantify the probability of habitat use. RSFs were performed at the metapopulation scale, including locations of all birds, regardless of their region of origin or sex. Habitats and seasons were tested as fixed effects as factor variables using respectively the three habitat categories (open habitats, closed habitats, and SFS, excluding other habitats category) and the five consecutive seasons (from first summer to second summer). The model included interactions between habitat and season in order to detect seasonal changes in habitat use (see Appendix S6: Table S1). The model includes random effects of individual identity to account for heterogeneity in the locations among individuals, and a random on the region identity as identified above (Causses, Pre-Alps, mountains, and Corsica) to account for context-specific habitat selection within particular areas. We used *predict* function in R (*base* package version 4.2.0) to predict the probability of use of each habitat for each factor level. Regional differences in habitat selection were further

investigated using post hoc analysis of individual groupings.

# RESULTS

## Post-fledging exploration behaviors

During the 0- to 0.5-year period, 90% of the birds were classified as “resident” (N = 43; Figure 4A). Among birds monitored for up to 1 year, 24% were “resident,” 28% were “medium-distance explorers,” and 48% were “long-distance explorers” (N = 36; Figure 4A). These proportions became respectively 25%, 19%, and 56% up to 1.5 years (N = 18; Figure 4A). Overall, departure decisions for both medium-distance and long-distance exploration mainly occurred between 6 months and 1 year after fledging (Figure 4B). We did not find any significant effect of sex on the exploration status at 1 year (Fisher’s exact test, *p* = 0.509), as well as for the maximum distance reached after 1 year (Dmax-1y; $F_{1,13} = 2.9145$, *p* = 0.112, $\eta^2 = 0.18$ [0.00, 1.00]). Conversely, the region of fledging had a significant effect on both exploration statuses (Fisher’s exact test, *p* = 0.034) and Dmax-1y ($F_{3,13} = 3.788$, *p* = 0.037, $\eta^2 = 0.47$ [0.03, 1.00]). All Bearded Vultures were resident in Corsica, whereas the proportion of explorers was the highest in the Causses (70%, respectively 60% and 10% for long and medium distance; Figure 5). In the Pre-Alps, the proportion of explorers was higher (63%) than in the mountains (50%), especially for long distance (respectively 36% and 20%). Examining the maximum distance reached after 1 year (Dmax-1y) confirmed these differences among regions: birds from the Causses traveled on average further and with higher individual variability (371 ± 398 km) than in the Pre-Alps (291 ± 189 km) or in the mountains (242 ± 109 km). Corsican birds traveled on average the shortest distance (83.4 ± 3.38 km). Even if the effect of sex was not significant, males seem to have explored further than females, with higher proportions of explorers and higher Dmax-1y.

Irrespective of the regions, Bearded Vulture movements showed a consistent phenological pattern over the first 18 months after fledging (Figure 2). Although the extent of the area explored from the fledging site varied with a factor of 10 according to the region (NSD < 10,000 km² in Corsica; >100,000 km² for the Causses), birds typically spent their first summer close to the fledging site (NSD < 10,000 km²). Distances from the fledging site remained limited during the first autumn and winter for all individuals, but started increasing in spring, either suddenly or gradually, including for residents (Figure 2). The median date of departure did not
<figure><img src="image_5.png" /><figcaption>**FIGURE 4** Overall proportion of exploration status categories, departure date, and duration of all Bearded Vultures tracked. (A) Proportions of resident (green), medium-distance explorers (orange), and long-distance explorers (red) among birds tracked for 0.5, 1, and 1.5 years. (B) Departure dates of first exploration events. (C) Durations of exploration periods in days. Median dates of departure for medium-distance (m1) and long-distance (m2) explorers are indicated with dashed vertical lines.</figcaption></figure>

significantly differ between medium-distance and long-distance explorers (respectively March 16 and April 30; $F_{1,15} = 0.925, p = 0.352, \eta^2 = 0.06$ [0.00, 1.00]), and 85% of the departures occurred between February and June (Figure 4B). However, the average duration of the medium-distance exploration periods was longer than for long-distance exploration periods (42.8 vs. 10.5 days, respectively; $F_{1,8} = 7.498, p = 0.026, \eta^2 = 0.48$ [0.05, 1.00], Figure 4C), and shorter for males than for females (20 vs. 45.8 days, respectively; $F_{1,8} = 8.078, p = 0.022, \eta^2 = 0.50$ [0.07, 1.00]). Region of fledging had no significant effect on the date or the duration of the exploration period. In contrast, the direction of movement trajectories strongly varied along birth origin and region of fledging. Compared with wild-born individuals, the directional pattern for captive-bred individuals was as much inconsistent as their release site was distant from already established populations (Appendix S5).

## Resident spatial behaviors

The home range sizes (UD95) varied significantly according to the season ($\chi^2_4 = 42.12, p < 0.001, \eta^2 = 0.35$ [0.20, 1.00]), the region of fledging ($\chi^2_3 = 7.82, p = 0.049, \eta^2 = 0.15$ [0.02, 1.00]; Figure 6A–D), and the sex ($\chi^2_1 = 8.36, p = 0.004, \eta^2 = 0.18$ [0.00, 1.00]; Figure 6E). With regard to the season, home ranges progressively extended in the first year, becoming larger from summer to autumn and winter (1616, 2993, and 3369 km²,

respectively) and being the largest in the first spring after fledging (9016 km²). Afterward, home range sizes stabilized or decreased (Pre-Alps and Corsica) between the first spring and the second summer (on average 7247 km²). Regarding regions, the home ranges of birds from the Causses and from Corsica were notably smaller (1591 and 2181 km², respectively) than those in the Pre-Alps and the mountain regions (4484 and 5369 km², respectively; Figure 6A–D). No sex difference could be noticed among released birds, and the larger home ranges of wild-born males compared with females (4490 vs. 2935 km², respectively; Figure 6E) should be taken with caution due to the small number of wild-born individuals.

Despite the apparent increase in home range size for birds that returned to their initial home range, the difference was not significant ($\chi^2_2 = 2.612, p = 0.271$; Figure 6F). Besides, 85% ($n = 7$) of medium-distance explorers returned to the same population, while 87% ($n = 8$) of long-distance explorers settled in a new area after the exploration period.

Overall, Bearded Vultures were more attracted by SFS and open habitats (mean probability of use of 26.3% and 11.3%, respectively) than closed habitats (4.3%; see Figure 7; $\chi^2_3 = 25,462, p < 0.001$). Habitat preferences differed between seasons ($\chi^2_{16} = 2233, p < 0.001$). Foraging behavior toward open habitat was quite consistent through the annual cycle (coefficient estimates between 0.94 and 1.20), but the use of SFS was lower during the summer periods (1.71 and 0.99) and peaked
<figure><img src="image_6.png" /><figcaption>**FIGURE 5** Comparison of movement variables of all tracked Bearded Vultures with respect to external (region or fledging) or internal (sex or birth origin) characteristics. (A) Proportion of resident (green), medium-distance explorers (orange), and long-distance explorers (red). (B) Maximal distance after 1 year (Dmax-1y); (C) first exploration date; and (D) first exploration duration. Black lines in the middle of blue boxes indicate median values; lower and upper limits of the boxes indicate first and third quartiles, respectively. Vertical lines indicate the 5th and 95th percentiles.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**FIGURE 6** Comparison of home range sizes (UD95) and core area sizes (UD50) with respect to internal (sex, birth origin, and exploration status) or external characteristics (region of fledging and season). (A–D) Seasonal change scaled from the first to the second summer after fledgling of Bearded Vultures among the different regions. (E) Sex (f, female; m, male) and birth origin (released translocated captive-bred and wild-born). (F) Home range size (HR) before and after exploration movement: 1 month before departure (original HR) and 1 month after either return to the region of fledging (HR return) or establishment in another region (HR shift). UD, utilization distribution.</figcaption></figure>

during the first spring following fledging (2.67). Random variances associated with individual were similar to regional variations (respectively 0.013 and 0.016). Attraction toward SFS was the weakest in the Causses

and the strongest in the Pre-Alps and the mountains (Figure 7). In contrast, there were no consistent differences between males and females (see Appendix S6: Figure S1).
<figure><img src="image_8.png" /><figcaption>**FIGURE 7** Comparison of habitat use of all tracked Bearded Vultures across seasons (scaled from the first to the second summer after fledgling) with respect to their region of fledgling. Habitat uses are represented as response values for each landscape covariate estimated from the resource selection functions analysis and are expressed as predicted probability of use for the three habitat categories: closed habitats, open habitats, and supplementary feeding stations (SFS) obtained for each season and each region separately (see Appendix S6 for details).</figcaption></figure>

## DISCUSSION

Our study highlights strong interpopulation differences in exploration movements and foraging habitat preferences of Bearded Vultures during the first year after fledgling and particularly during the first year post-release in newly reintroduced populations. Seasonal timing of exploration departures were however highly consistent across populations.

### Exploration movements

During the first year after fledgling, movements intensified and showed a strong temporal synchrony, irrespective of the study regions or birth origin. From fledgling to the first winter, both captive-bred and wild-born Bearded Vultures behaved overall as a resident, with movements remaining restricted within their fledgling area (<100 km). Such resident behaviors could be explained by the need for young birds to learn soaring-gliding techniques in their first summer (Harel et al., 2016) or reflect harsh climatic conditions that limit soaring-gliding flight during winter as

documented in Eurasian Griffon Vultures and California Condors, *Gymnogyps californianus* (Rivers, Johnson, Haig, Schwarz, Burnett, et al., 2014). On the other hand, in the spring of their second calendar year, Bearded Vultures increased their movement activities, with a peak of exploration departures concentrated between March and June, and displayed larger home ranges. After 1 year, more than half of the Bearded Vultures have displayed long-distance explorations, usually characterized by short but intensive traveling periods (~10 days), and about 20% of birds have exhibited medium-distance explorations over longer time periods (~40 days) and more progressive displacement from their fledgling site. Eventually, less than a third of the birds remained resident after 1 year. These findings are similar to other raptors, for which immature or nonbreeding individuals often display highly seasonal movements and can cover great distances of several hundreds of kilometers: Bearded Vulture (Krüger et al., 2014; Margalida et al., 2013), Golden Eagle (Moss & Hipkiss, 2014; Sur et al., 2020), Cinereous Vulture (Carrete & Donázar, 2005; Gavashelishvili et al., 2012; Reading et al., 2020), and Eurasian Griffon Vulture (Monsarrat et al., 2013).
The frequency and the magnitude of these exploration behaviors, as well as the directional patterns, were however strongly dependent on the region of fledging. The effect of the birth origin itself could not be evidenced conclusively because of the small sample size of individuals monitored for 1 year or more (N = 18) and of confounding effects with the region of fledging. Nevertheless, Bearded Vultures translocated in regions with low elevation, small area, and that were the most distant from established populations displayed exploration behaviors in much higher proportion, moving farther and in more scattered directions than wild-born and translocated individuals released closest to established populations. For instance, the vast majority of birds translocated in the most isolated site (70% in Causses) were either medium- or long-distance explorers moving up to 1000 km or more, whereas wild-born birds from Corsica island were all resident and traveled relatively short distances (<200 km). These differences could result from several factors that were not mutually exclusive.

Exploration movements in Corsica island could be limited because large raptors may be reluctant to cross large marine areas (Bildstein et al., 2009). Although a few observations of Bearded Vultures crossing the Mediterranean have been documented (Grussu & Seguin, 2015), birds from Corsica may thus have been overall stuck on the island. In contrast, the exploration behavior of birds fledged on the mainland continent may have been enhanced by the terrestrial geographical continuum, with some adjustments depending on the environmental habitat characteristics and the social environment (e.g., presence of conspecifics).

The presence or absence of resident conspecifics may have played an important role in either enhancing the distance and scattering the direction of exploration movements in areas distant from established populations, or at the opposite, limiting and directing explorations as a result of conspecific attraction in areas close to existing populations (Danchin, 2004). This hypothesis could explain (1) the high proportion of medium-distance exploration movements in the mountain ranges resulting from progressive displacements along the mountain ranges already populated by Bearded Vultures (internal Alps and Pyrenees); (2) the high proportion of long-distance explorers moving the farthest and in a wide array of directions in isolated populations surrounded by less favorable habitats (such as the Causses, located more than 300 km from other populations); (3) the medium-distance exploration directed toward existing populations of the Alps by captive-bred Bearded Vultures translocated in the Pre-Alps. Similar contrasted movement patterns between wild-born and captive-bred translocated individuals, with comparable interpretations

about the effects of behavioral mechanisms related to conspecific attraction, have been shown in Bearded Vulture (Margalida et al., 2013) and other raptors such as Spanish Imperial Eagle (Morandini & Ferrer, 2017; Muriel et al., 2016).

## Home range and foraging habitat selection

During the residence periods, home range sizes were smaller in the Causses and Corsica compared with the high mountains of the Alps and Pyrenees. Home range sizes in the Alps and Pyrenees during the first spring and second summer (9382 and 11,072 km²) were very similar to those found by Margalida et al. (2016) in immature Bearded Vultures from the Pyrenees (~9295 km²), and show similar phenological pattern as in California Condors (Rivers, Johnson, Haig, Schwarz, Burnett, et al., 2014). In contrast, Bearded Vultures in the Causses were mainly staying around three canyons, occupying therefore a very small area in the Massif Central. In the Alps, Pyrenees, and to a lesser extent the Pre-Alps, a large amount of typically suitable mountainous habitat likely promoted space use over a much larger area than in the Causses or Corsica. In the absence of conspecifics and because movement behaviors of immature raptors may be primarily driven by food search (Morandini et al., 2020), it is possible that young Bearded Vultures released in the Causses stayed around their release site where food is abundant, whereas they could forage more extensively and possibly followed conspecifics in other regions, with the exception of Corsica, which may have restricted movement due to geographical isolation. Wild-born males appeared to have larger home ranges than females, although this result should be considered with care as the sample size was small (n = 6).

Regarding foraging habitat, Bearded Vultures showed a consistent preference for SFS over open habitats and, in turn, over closed habitats. Despite that home range sizes and movement distances can markedly change across seasons, habitat preferences remain overall consistent during the year and among regions, independent of differences in wildlife or SFS density. Open habitats allow detecting and accessing carcasses of wild or domestic ungulates, as well as facilitate taking off from the ground, whereas attraction for SFS can be explained by a predictable food provision in time and space. These findings are consistent with both theoretical and empirical evidence: according to the marginal value theorem (Charnov, 1976), individuals may use preferentially and stay longer in areas where food availability is high compared with surrounding environments. Empirically, Eurasian Griffon Vultures preferred open habitat and SFS in the
Causses, especially in winter (Fluhr et al., 2017; Monsarrat et al., 2013), and California Condors preferentially use open or sparse habitats, such as coastal dunes, in a consistent way throughout the year (Rivers, Johnson, Haig, Schwarz, Glendening, et al., 2014). Although general patterns of habitat use appear consistent both within and between species, differences for particular habitat types or SFS can be observed due to interspecific food preferences or heterogeneity in food availability between regions (Spanish Imperial Eagle, Morandini et al., 2020; California Condor, Rivers, Johnson, Haig, Schwarz, Glendening, et al., 2014).

The consistent use of open habitat over seasons might reflect regular foraging movements for detecting carcasses of wild or domestic ungulates outside SFS. Although foraging preferentially targeted SFS throughout the year, the use of SFS decreased in summer and was the highest in spring. The availability of wildlife carcasses as well as the importance of summer transhumance generating livestock movements (Arrondo et al., 2023) can increase the amount of food available for vultures and other avian scavengers, therefore decreasing the attraction of SFS. In contrast, SFS may attract Bearded Vultures toward SFS the most in spring time, corresponding to the rearing period of chicks, due to food scarcity after the winter period or because of important livestock mortality. The contrasted selection of SFS may reflect the differences in SFS management, ungulates density, and accessibility, as well as the presence or absence of conspecifics and other vulture species among regions. Intra- and interspecific social information may facilitate food search through a facilitatory process to detect carcasses within an ecological community (Gil et al., 2018), such as through conspecific and heterospecific attraction in scavenger species assemblages (Sebastián-González et al., 2021). In addition, both inter- and intraspecific hierarchies and interactions through competition, search, or access to food might play a role in the degree of preference for SFS (Arrondo et al., 2019). For instance, the presence or the absence of Eurasian Griffon Vultures or other obligate and facultative scavengers, as well as their respective density, may differently affect the foraging behaviors of Bearded Vultures between regions.

## Conclusion: Implications for conservation

Our study suggested that the translocation of very mobile organisms to restore demographic connections between populations at the European scale is realistic, provided that the establishment of the new populations at the reintroduction sites could be achieved. Yet, taking the

establishment of captive-bred individuals on the release site for granted would be overoptimistic. In particular, another important finding for the establishment of released individuals on the translocation area is that long-distance explorers were not only in the highest proportion in the Causses, the most isolated site, but they also settled their home range in another region afterward in most cases. In contrast, medium-distance explorers, in highest proportion in the mountains and to a lesser extent in the Pre-Alps, mostly get back to their region of fledgling (85%). In addition to challenging the success of local population re-establishment and metapopulation restoration through dispersal, exacerbated post-released exploration behaviors may make translocated individuals more vulnerable to mortality as they explore more distant or less suitable areas (Hall et al., 2021; Le Gouar et al., 2012; Mihoub et al., 2009). In addition to the recommendations of Van Overveld et al. (2020) to better incorporate vulture social behaviors into conservation practices, our study underlines that large-scale exploratory movements must also be integrated to prevent unforeseen outcomes. For instance, two young Bearded Vultures from the Alps and Causses were killed by collision with wind turbines between 2020 and 2023 in the Netherlands, thousands of kilometers away from their fledging sites.

Accurately assessing and quantifying animal movements are essential to the improvement of biodiversity conservation. In particular, post-release movements in conservation translocation may both show unusual patterns and be critical for the outcomes of restoration programs, be it the establishment of a population or the restoration of connection between populations within metapopulations (Le Gouar et al., 2012). Post-release movements may indeed lead released individuals to leave the release area, either through permanent emigration (Eurasian Griffon Vulture, Le Gouar et al., 2008) or decreased survival (Eurasian Griffon Vulture, Fozzi et al., 2023; Cinereous Vulture, Rousteau et al., 2022). Although these outcomes are not systematic, because in some cases individuals reared in captivity may behave comparably to those from the wild (California condor, Rivers, Johnson, Haig, Schwarz, Burnett, et al., 2014), post-released movements strongly depend on release methods (Fozzi et al., 2023) or site characteristics (Le Gouar et al., 2008; Rivers, Johnson, Haig, Schwarz, Burnett, et al., 2014; Rousteau et al., 2022). Understanding movement strategies is necessary to define the spatial and temporal scales at which the habitat quality should be assessed, managed, protected, or restored for the target species, particularly when movement increases the risk of negative effects on survival or modifies the probability of recruitment in a target breeding area.

Assessing post-release movements would allow us to better forecast the demographic consequences of
individual movements on population viability, for example, through modeling, and to investigate the effects of land use changes or to compare different management strategies. For instance, changes in livestock farming systems in the Mediterranean region have translated into land abandonment, increasing the extent of forested areas and shifting from domestic to wild ungulates. These processes could reduce foraging areas, food detectability, and availability in time and space for the scavenger community (Arrondo et al., 2019) if alternative, nature-based solutions countering encroachment and compatible with food provisioning are not anticipated, such as rewilding (Martin-Díaz et al., 2020). To our knowledge, the complexity of the interactions between ethical, social, economic, political, and ecological processes makes it difficult to predict the future dynamics of rewilding in socio-ecosystems from local to large scale over Europe. Nevertheless, these dynamics should be monitored to measure their impact on scavenger populations.

Despite seasonal and regional differences, and even higher among individual variations, the overall preference for SFS of captive-bred translocated Bearded Vultures suggested that food supply can reduce post-release movements and promote fidelity within the release areas. Nevertheless, this resident behavior may only be temporary and would last just as long as movements are essentially triggered by food search, such as in juvenile or nonbreeding stages, and/or in particular seasons when resources are scarce and weather conditions did not facilitate movements, such as winter for soaring birds. Therefore, the expected outcomes associated with this resident behavior may occur in the very short term only, even when food is provisioned and other vulture species are present in the release area, such as in the Causses. As demonstrated here, this residence period may be immediately followed by a period of intense exploratory movements over much larger distances when environmental conditions change and/or individuals matured in areas where no or too few conspecific individuals are present. In this respect, translocated Bearded Vultures displayed rather contrasted post-release behaviors compared with those of established populations, particularly when they were released at isolated sites. Interestingly, these behavioral movement patterns corroborated previous findings in Bearded Vultures, with reintroduced individuals in Alps and Andalusia moving farther than wild individuals in the Pyrenees (Margalida et al., 2013). As a matter of fact, 1 year after release, about 50% of the birds from reintroduced populations have already explored other established breeding populations in the Pyrenees and the internal Alps,

whereas the reverse had not been observed yet. Consequently, post-release movements of translocated birds may indicate the potential for future demographic connections though it may still indicate a risk of failure to establish new populations at reintroduction sites. However, more follow-up releases may overcome the risk of leaving if that risk is due to social cueing. Indeed, we expect that birds that stayed would, by their presence, encourage newly released birds to stay.

Habitat selection relating to social cueing, such as conspecific attraction, may be particularly problematic as translocated individuals could permanently settle in the remnant populations rather than in the translocation area, and eventually lead to reintroduction failure (Le Gouar et al., 2008). As none of the translocated individuals has reached sexual maturity, it is premature to conclude whether the high mobility of Bearded Vultures translocated as juveniles could contribute to achieving the goals of continental-scale restoration program such as the LIFE Gypconnect program, that is, reconnecting isolated populations through dispersal. While it is too early to evaluate the success of the actions implemented within this translocation program, further analyses focusing on other proxies of success over a longer monitoring time period may help complete our findings. For instance, reporting the breeding location of translocated birds when they become mature, quantifying the survival rates of birds within the populations, or measuring actual dispersal rate evidencing demographic connections would provide new insights on the long-term restoration of such metapopulation viability.

## AUTHOR CONTRIBUTIONS

Jean-Baptiste Mihoub, Olivier Duriez, and François Sarrazin conceived the ideas and designed the methodology. Benoit Betton, Jocelyn Fonderflick, Franziska Loercher, Etienne Marlé, Jean-François Seguin, Julien Traversier, Noémie Ziletti, and Olivier Duriez contributed to data collection. Cécile Tréhin analyzed the data. Cécile Tréhin and Jean-Baptiste Mihoub led the writing of the manuscript. All the authors contributed critically to the drafts and gave final approval for publication.

## ACKNOWLEDGMENTS

The authors are grateful to all people involved in the fieldwork for tagging and monitoring Bearded Vultures studied here as well as the partners of the LIFE Gypconnect consortium who dedicated their efforts to the restoration of the species in Europe, especially P. Orabi for his excellent coordination of the project. We also warmly thank S. Benhamou, R. Patin, and
N. King-Gillies for their precious advice and support at the early stage of the analysis. We are also particularly thankful to two anonymous reviewers who have contributed to significantly improve the manuscript.

## FUNDING INFORMATION

This work was supported by two EU program LIFE Projects (LIFE Gypconnect, LIFE14 NAT/FR/000050 and LIFE GypAct, LIFE NAT/FR/101074131). JBM and FS also benefited from the scientific context of the Transloc Project funded through the 2020-2021 Biodiversa+ and Water JPI joint call for research projects, under the BiodivRestore ERA-NET Cofund (GA number 101003777), with the EU and the French ANR. This research did not receive any further specific funding from other agencies in the public, commercial, or not-for-profit sectors.

## CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

## DATA AVAILABILITY STATEMENT

Metadata and R code (Tréhin et al., 2024) are available from Zenodo: https://doi.org/10.5281/zenodo.10721077. GPS telemetry data are available from MoveBank (www.movebank.org) in the study "Bearded Vulture in France - National Action Plan ID_PROG 961." Tracking data may be obtained by qualified researchers by contacting the coordinator of the PROG 961 action plan referenced in MoveBank.

## ORCID

Cécile Tréhin https://orcid.org/0000-0002-8625-3513

Olivier Duriez https://orcid.org/0000-0003-1868-9750

François Sarrazin https://orcid.org/0000-0001-5901-4819

Jean-Baptiste Mihoub https://orcid.org/0000-0002-5354-850X

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## SUPPORTING INFORMATION

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**How to cite this article:** Tréhin, Cécile, Olivier Duriez, François Sarrazin, Benoit Betton, Jocelyn Fonderflick, Franziska Loercher, Etienne Marlé, et al. 2024. “Long-Distance Post-Release Movements Challenge the Metapopulation Restoration of Bearded Vultures.” *Ecosphere* 15(8): e4856. https://doi.org/10.1002/ecs2.4856