Bestandseffekter af menneskelige forstyrrelser af rovfugle

Raptorial birds often express considerable shyness towards humans, which is probably an adaptive result of generations of human persecution in the past. Shyness may therefore persist in raptor populations for several generations after receiving legal protection. Negative disturbance reactions do not only include observable flight responses. Avoidance of disturbed areas may also affect population size negatively due to indirect habitat loss. Studies of flight distances and population density in relation to road density (index of local human activity) of Common Buzzards Buteo buteo in Denmark based on data collected by volunteers from Kolding raptor group suggest that larger-bodied and long-lived raptors still exhibit substantial human avoidance and suffer avoidance-mediated habitat loss. Based on this information, it is plausible that increased recreational activity in Danish state forests may lead to reduced population size through avoidance-mediated habitat loss. At present, the population consequences of increased recreational activities in governmentally managed nature areas have not been systematically evaluated. Population data reported from a single state forest support the notion, however, that strongly increased human activity may cause substantial reductions of local breeding densities of raptors. If population density of largebodied raptors and other disturbance-sensitive wildlife species is a management priority, a first step should be to analyse the extent to which increased public activity in general and actions aimed at facilitating increased recreation use (establishment of mountain bike trails, shelter places etc.) have led to reduction in numbers of breeding pairs and breeding success of raptor species compared to earlier times as well to forest areas with less liberal rules for public access. Trials with different types of restrictions of public access to delimited zones of potential breeding habitats may further provide experimentally based evidence of the effect of recreational activity during the breeding season on breeding density and breeding success of raptors as well as on other disturbance-sensitive wildlife. To establish this evidence, census data on number, distribution and breeding success of raptors, registered for decades by volunteers organised in Birdlife Denmark’s raptor groups will be of pivotal importance.