Abstract
Despite the consensus among ecologists and conservationists of the importance of maintaining scavenger feeding patterns based primarily on natural prey sources, human‐mediated feeding remains a widely used management tool for threatened wildlife. Thus, it is important to understand the key factors favoring certain species and age‐groups at supplementary feeding sites. Through a detailed videomonitored experiment of carrion inputs at different locations in the Iberian Peninsula (home of >90% of European vultures), we assessed how variables related to weather, time, demography, management and alternative food availability influenced the occurrence patterns of different age‐classes of vultures at feeding sites. The most threatened and less gregarious species (bearded vulture Gypaetus barbatus and Egyptian vulture Neophron percnopterus) attended to earlier inputs, thus reducing interspecific competition with the Eurasian griffon vulture Gyps fulvus. The bearded vulture was favored by a larger biomass supply at the feeding sites during the chick‐rearing period, while the Egyptian vulture preferred frequent and abundant inputs. Non‐adult cinereous vultures Aegypius monachus were favored at times of lower abundance of natural resources and in the densest networks of feeding sites, while adults preferentially attended sites with periodic inputs close to breeding colonies in areas with lower availability of other natural prey. Finally, the Eurasian griffon vulture showed a preference for continued and periodic inputs, and for feeding sites with numerous other feeding sites in the surroundings. Our results help to inform the management of supplementing food provision with the aim of enhancing its value to reverse the unfavorable conservation status of endangered species and to mitigate the negative effects of the current global threats impacting them.
Highlights
Supplementary feeding programs have been implemented to reverse the devastating impact of carcasses from cattle medicated with veterinary drugs such as diclofenac on Asian vultures (Gilbert et al 2007), to reduce the negative effects of poisoned baits on threatened African vultures (Virani et al 2011, Ogada et al 2012) and to alleviate the depletion and alteration of carcasses occurrence due to legislative changes in Europe (Donazar et al 2009b, Margalida and Colomer 2012)
The most parsimonious model determining the attendance patterns of non-adult bearded vultures at feeding sites included variables related to the time: earlier hours of provision during the chick-rearing period were positively related to the number of individuals, as well as those associated with the management, preferring supplementary feeding sites with a greater annual biomass in the previous years during the chick-rearing period (Fig. 1, Table 3)
The best model explaining the presence of adults at feeding sites included the abundance of extensive livestock around the site and the interaction between the life-cycle phase and the provisioning frequency, Fig. 1
Summary
Carrion ecology and its role in the feeding of wild scavengers is a field of study that has gained special relevance in recent years (Barton et al 2013, Oro et al 2013, Fielding et al 2014), from the perspective of conservation management in European and African countriesMORENO-OPO ET AL.(Cortes-Avizanda et al 2010, Margalida et al 2011a, Duriez et al 2012, Kane et al 2015, Moreno-Opo et al 2015). A general consensus exists among ecologists and conservationists that supplementary feeding should be used as a temporary management option, determined by very specific performance requirements (Gonzalez et al 2006, Robb et al 2008, Ewen et al 2015) In this sense, the relationship between scavengers and food availability should be primarily shaped by natural scenarios regulating the population dynamics of the involved species, which should evolve and interact without human intervention (Oro et al 2013, Fielding et al 2014). Supplementary feeding for scavengers can be defined as the set of activities around the provision of carrion by humans for its exploitation by the targeted species through a wide variation of procedures and protocols These include the management of fenced feeding sites with abundant and predictable carrion inputs from intensive farming, to the non-removal of dead livestock on extensive farms or wild ungulates as a result of hunting activities. This requires knowledge of how the frequency of carcass inputs, time (hour and season), geographic location, weather conditions and the format in which the carrion is presented, impact the occurrence of different scavenger species at feeding points
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