Signs of foraging by wild boar as an indication of disturbance to ground-nesting birds

Wild boar (Sus scrofa) population increases have been spectacular in many countries, including France. Wild boar can substantially affect many ecosystem components, including birds, but indicators to monitor such effects are currently lacking. We examined the usefulness of monitoring wild boar foraging traces resulting from rooting behaviour to evaluate wild boar disturbance on ground-nesting birds and developed a simple indicator of kilometric foraging (Ikf). This study measured the effect of wild boar on bird abundance, taking into account vegetation characteristics. Using standardised spot counts, we found ground-nesting bird abundances negatively correlated with Ikf. Our results showed a significant decrease of 45% in ground-nesting bird abundance in areas strongly foraged and disturbed by wild boar. By contrast, the abundance of birds depending on ground or trees for food resources but nesting out of reach of wild boar were not correlated to rooting behaviour traces. Thus, we conclude that Ikf may be a simple and suitable indicator that managers can use on a large scale to monitor wild boar potential disturbance and ecological footprint on ground-nesting birds and other taxa. Further studies are needed to test and validate this new indicator in areas other than the Sainte-Baume Regional Park.