Abstract
Despite the ubiquity and magnitude of food provision to wildlife, our understanding of its ecological effects and conservation implications is very limited. Supplementary feeding of ungulates, still one of the main paradigms of game management in Europe, occurs in natural areas on an enormous scale. We investigated the indirect effects of this practice on nest predation risk in the Polish Eastern Carpathians (Bieszczady Mountains). We hypothesized that the predators attracted to ungulate baiting sites would also forage for alternative prey nearby, increasing the nest predation risk for ground-nesting birds in the vicinity. We conducted a paired experiment by placing artificial nests (N = 120) in feeding and control sites (N = 12) at different distances from the ungulate feeding site. We also documented the use of three ungulate feeding sites by potential nest predators with automatic cameras. The proportion of depredated nests was 30% higher in the vicinity of feeding sites than at control sites (65%±31.5 vs 35%±32.1). The probability of a nest being depredated significantly increased with time and at shorter distances from the feeding site. We predicted that the area within 1-km distance from the feeding site would have a high risk (>0.5) of nest predation. We recorded 13 species of potential ground-nest predators at ungulate baiting sites. Most frequent were Eurasian jays Garrulus glandarius, mice and voles Muroidea, ravens Corvus corax, brown bears Ursus arctos, and wild boar Sus scrofa. Nest predators made most use of supplementary feeding sites (82% pictures with predators vs 8% with ungulates, the target group). Our study alerts of the impacts of ungulate feeding on alternative prey; this is of special concern when affecting protected species. We urge for a sensible management of ungulate feeding, which considers potential indirect effects on other species and the spatial and temporal components of food provision.
Highlights
Supplementary feeding of wildlife is occurring on a colossal scale nowadays
The proportion of nests lost to predation was significantly higher (Wilcoxon matched pairs test, W = 35.5, p = 0.036) and almost double in the vicinity of ungulate feeding sites than at control sites (Fig. 3)
Results of the Generalized Linear Mixed Model explaining the variation in the probability of artificial ground nests (N = 120) being depredated in relation to the distance to ungulate feeding sites (m, log-transformed) and the number of days elapsed since nest deployment (6 and 15 days)
Summary
Supplementary feeding of wildlife is occurring on a colossal scale nowadays. Food supplementation has been widely used across the globe as a conservation and management tool, for threatened species. Herbivore concentrations around feeding sites are associated with overgrazing of the palatable vegetation and changes in the plant composition in the area [11,19,27] These cascading effects may get special relevance when food subsidies are provided in natural and semi-natural areas and when they affect species of conservation concern. In North America, this practice has been intensively debated [32], in relation to disease transmission risk [25,26], and has been widely restricted or prohibited [13] The goals of this practice have been to maintain high densities of animals for hunting; to improve their nutritional status, survival and reproductive performance, especially in winter, as well as the quality of trophies; to prevent damages in forestry and agriculture; and to attract ungulates to shooting spots or for recreation [11,12,13]. We documented a significant negative effect of ungulate feeding sites on nest predation risk
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