Uneven Large-Scale Movement Patterns in Wild and Reintroduced Pre-Adult Bearded Vultures: Conservation Implications

Abstract

After the quasi-extinction of much of the European vertebrate megafauna during the last few centuries, many reintroduction projects seek to restore decimated populations. However, the future of numerous species depends on the management scenarios of metapopulations where the flow of individuals can be critical to ensure their viability. This is the case of the bearded vulture Gypaetus barbatus, an Old World, large body-sized and long-lived scavenger living in mountain ranges. Although persecution in Western Europe restrained it to the Pyrenees, the species is nowadays present in other mountains thanks to reintroduction projects. We examined the movement patterns of pre-adult non-breeding individuals born in the wild population of the Pyrenees (n = 9) and in the reintroduced populations of the Alps (n = 24) and Andalusia (n = 13). Most birds were equipped with GPS-GSM radio transmitters, which allowed accurate determination of individual dispersal patterns. Two estimators were considered: i) step length (i.e., the distance travelled per day by each individual, calculated considering only successive days); and ii) total dispersal distance (i.e., the distance travelled between each mean daily location and the point of release). Both dispersal estimators showed a positive relationship with age but were also highly dependent on the source population, birds in Andalusia and Alps moving farther than in Pyrenees. Future research should confirm if differences in dispersal distances are the rule, in which case the dynamics of future populations would be strongly influenced. In summary, our findings highlight that inter-population differences can affect the flow of individuals among patches (a key aspect to ensure the viability of the European metapopulation of the endangered bearded vulture), and thus should be taken into account when planning reintroduction programs. This result also raises questions about whether similar scenarios may occur in other restoration projects of European megafauna.

Man‐induced activities modify demographic parameters in a long‐lived species: effects of poisoning and health policies

“…Thus, although the percentage of pairs that do not start laying annually is important (range 29.4À58.1%), the decision to start breeding, which could be influenced by the physical condition of the individual (Jenouvrier et al 2005), appears not to compromise the reproduction of Bearded Vultures. This suggests that, in this isolated population, several buffering mechanisms (e.g., changes in the structure of breeding age, low dispersal movements) may contribute to maintain stability in the percentage of pairs that start laying (Sergio et al 2011, Margalida et al 2013. In this sense, the carcass disposal policy does not seem to affect population movements because pre-adult individuals remained in the study area without greater pre-dispersal movements (Margalida et al 2013).…”

“…This suggests that, in this isolated population, several buffering mechanisms (e.g., changes in the structure of breeding age, low dispersal movements) may contribute to maintain stability in the percentage of pairs that start laying (Sergio et al 2011, Margalida et al 2013. In this sense, the carcass disposal policy does not seem to affect population movements because pre-adult individuals remained in the study area without greater pre-dispersal movements (Margalida et al 2013). With respect to non-natural mortality, although mortality factors affect mostly adult age classes (Margalida et al 2008b, Oro et al 2008, they seem to play no role in the start of breeding.…”

The flight feather moult pattern of the bearded vulture (Gypaetus barbatus)

“…During the following months, they will wander over extensive areas, and they must learn to become self-sufficient, acquire flight skills, find food resources, and exploit them efficiently. This period is, therefore, critical for survival (Margalida et al 2013;Gil et al 2014;López-López et al 2014). Possibly as a consequence, we found that 2nd cy birds delayed start of primary moult until late in May, and only few birds were able to moult secondaries during the last month before the end of the moulting season, in winter.…”

Importance of Long-Term Studies to Conservation Practice: The Case of the Bearded Vulture in the Pyrenees

“…changes in the structure of breeding age, low dispersal movements and/or the availability of natural food) may contribute to maintain stable the proportion of pairs that start laying (Sergio et al 2011;Oro et al 2012;Margalida et al 2013). In this sense, the carcass disposal policy does not seem to affect population movements because pre-adult individuals remained in the study area without greater pre-dispersal movements (Margalida et al 2013). Thus, a possible explanation is related to the high food availability in the Pyrenees (Margalida et al 2011a).…”

“…To our knowledge, this would be another example of the detrimental effects of food supplementation programmes on the conservation of threatened species (Robertson et al 2006). Reducing food supply or progressively moving feeding stations outside of the Pyrenees may encourage floaters to settle in other areas where they could find breeding opportunities (see Margalida et al 2008aMargalida et al , 2013. The translocation of floaters of the endangered Seychelles magpie-robin Copsychus sechellarum from a population-saturated island to an unoccupied one was a successful conservation strategy, since individuals become breeders (Kokko and Sutherland 1998).…”