Pros and Cons, of Vulture Restaurants
Cortes-Avizanda, Ainara, Endangered Species Update
In Europe, the availability of food resources (i.e. carcasses) for scavengers has decreased during the latest decades mainly due to stricter sanitary legislation which, after the irruption of the BSE (Bovine spongiform encephalopathy), have lead to removal of all livestock carcasses and human hunter kills from the field. This is of great conservation concern because all European scavengers are protected species and some of them are in rapid population decline. Accordingly, European and regional administrations have supported the creation of "vulture restaurants" to provide scavengers with regular carcasses. Currently, these supplementary feeding stations have become the main food source for all avian scavengers which changes the spatio-temporal distribution of the food: before, carcasses were unpredictable both in space and time like other trophic pulse resources such as tree-masting or insect explosions which appear and are randomly distributed and unpredictable (Ostfeld and Keesing 2000; Rose and Polis 1998), and which suppose a "price" for the species or group of species that feed on it. Now, however, carcasses have become aggregated and predictable both in space and time.
The proliferation of vulture restaurants may lead to positive and negative effects both on scavengers and other species in the ecosystems. Spain holds important Old world scavenger populations and Spain is the country where more vulture restaurants have been created. As consequence of this proliferation of vulture restaurants, several research studies have appeared in the literature describing a spectacular increase of the breeding population of one species i.e. the griffon vulture (Gyps fulvus) (ca. 10,500, resident) (Del Moral and Marti, 2001; authors' unpublished data) while other avian scavenger populations continue declining (BirdLife, 2004). In the case of the endangered Egyptian vulture (Neophron percnopterus), it has been reported that vulture restaurants help the maintenance of breeding pairs and even that the breeding success of neighbor pairs to these food sources was higher in comparison to other pairs in the Ebro valley (Grande et al. 2009); this also permits the maintenance of large communal roosts during summer (Donazar et al. 1996; Grande et al. 2009). Indeed, vulture restaurants are currently a useful tool to support new individuals in the southern region of Spain (Cadiz, Andalucia) where the presence of the breeding pairs of Egyptian vultures is clearly declining (Benitez et al. 2009). However, the vulture restaurants' attempts to conserve the endangered population of bearded vultures (Gypaetus barbatus) in the Pyrenees have had undesirable responses: while the number of breeding pairs increased, the breeding success dropped dramatically. Research detected that the large assemblages of food prolonged in time aggregated the juveniles instead of being widespread. Bearded vultures are birds that do not live in groups so these concentrated individuals used to disturb the nearer breeding pairs. Moreover, because of this large availability of food, it has been detected that the number of new breeding pairs established near vulture restaurants increased too. In this scenario, the competitive interactions between all bearded vultures (juveniles and breeders) increased and vulture restaurants became stressful in this area for neighboring breeding pairs that continuously defend their territories (Carrete et al. 2006a, b; Oro et al. 2009).
Nevertheless, few studies have investigated the indirect effects of the prolonged presence of facultative species at those sites with a continuous hyper-concentration of carrion resources. Facultative species consume carcasses less efficiently and more slowly than the specialists or strict carrion-eaters and most importantly, they do not feed only on carcasses but also rely on small prey. This question becomes especially important when the possible species affected are of conservation concern. …