A systematic review of the effects of recreational activities on nesting birds of prey

Human disturbance to wildlife is a growing topic of concern owing to increasing human access to the countryside. Here we use systematic review methodology to specifically synthesize available information on the impact of recreational activities on raptor breeding parameters. Presently there is insufficient information to quantitatively meta-analyze this topic. The most frequent effect turned out to be decreased time for nest attendance but information on effects on breeding parameters was inconclusive. The only outcome susceptible to quantitative meta-analysis was the influence on nest location of a number of anthropic structures. Out of these we chose distance to the closest paved road, because it was the metric recorded in the largest number of studies, and because it can be taken as a surrogate of recreational access to the countryside. We detected an overall statistically significant impact on the displacement of nests from roads from a total of 25 studies, compared to random points in unoccupied areas suitable for breeding. The magnitude of the displacement was probably a biologically relevant magnitude (back-transformed ln response ratio 1.28; 1.07–1.57 bootstrap 95% CI). Importantly, statistical modelling of effect sizes as a function of raptor body size and nesting site substrate (tree nesting vs. cliff nesting) identified an effect of both nesting habitat and body size on nest placement by raptors in relation to roads. Big raptors nesting in trees exhibited greater displacement distances from nests to roads than big raptors nesting in cliffs, and hence we suggest that conservation efforts should take special attention to this vulnerable raptor group which includes some threatened species.