Anthropogenic influences on the ecology of forest songbirds within Sleeping Bear Dunes National Lakeshore: Focusing on roads

Human disturbance of natural ecosystems has increased over the last several decades and as the human population continues to grow, anthropogenic disturbance is expected to intensify. Anthropogenic disturbance creates direct and indirect effects with complex interactions that lead to species or taxa specific responses. Here, I review literature on the influence of roads and automobile traffic on birds. Birds are directly affected by roads through habitat loss and road-mortality and are indirectly affected by changes in habitat quality that may influence reproductive success, dispersal, abundance, community composition, and behavior. The severity of these impacts varies with habitat structure, traffic volume, speed limit, and traffic noise. Within a bird community, some species may benefit from road systems with increased reproductive success or abundance, while other species may be harmed. Synthesis of the avian road ecology literature, helps determine which species are most at risk from roads systems and how best to mitigate road system impacts. I further report the results of two studies examining the effects of roads and traffic on forest songbirds in Sleeping Bear Dunes National Lakeshore.;Bird abundance and species richness along roads and trails with different levels of vehicular disturbance and road conditions in forested habitats was studied using point counts along road edges and interior points. There was not a significant difference in total bird abundance, species richness, or individual species abundance between road edges and interior points. The lack of effect of roads and traffic on forest bird abundance and species richness in this system may be due to low traffic volume (<5000 vehicles/day).;Secondly, an artificial nest study was used to examine relative predation pressure and predators along paved and unpaved roads. Nests were placed at 25m, 50m, 75m, and 100m from roads. By the 12th day after nest placement 79% of artificial nests were depredated. Predation was higher along paved roads than unpaved roads, but distance from the road did not influence nest predation. Nest predators were identified by marks in plasticine eggs in 104 of 151 depredated nests, and mammals accounted for 94.2% of identified predation. Logistic regression of nests depredated by raccoons compared with nests depredated by non-raccoon predators showed raccoon depredation was higher along paved roads than unpaved roads, and this result was complicated by an interaction between northern hardwood and coastal forest habitats. These data suggest that roads have an impact on predator activity which negatively affected artificial nest success; however, artificial nest predation was not directly compared with real nest predation. Further studies would be necessary to obtain the direct effects of roads on breeding success of birds.;Within the Sleeping Bear Dunes region another anthropogenic influence was the introduction of white-tailed deer (Odocoileus virginianus ) to North Manitou Island. This introduction led to the functional extinction of Canada yew (Taxus canadensis), a favored browse species. Canada yew is still abundant on neighboring South Manitou Island. An artificial nest study was used to compare predation pressure in Canada yew patches with outside these patches. By the 12th day after nest placement 95% of artificial nests were depredated. Depredation was detected first at yew nests 6 times and 13 times at non-yew nests. Predators were identified by teeth and bill marks for 51 of the 95 depredated nests with birds accounting for nest depredation in 78% of cases. Predator-specific predation did not vary significantly between yew and non-yew artificial nests.