Forest birds use vegetated fauna overpass to cross multi-lane road

Abstract

Although wildlife overpasses have been constructed in many countries to provide safe crossing passages over roads, most have been focused on larger species of mammals. Bird use of these large structures has largely been ignored, although the impact of roads on birds is of increasing concern, especially among smaller, forest-interior species. We studied birds crossing a four-lane road over the road either above the surface or via a vegetated wildlife overpass near Brisbane, Australia, over two years. A total of 14 species were detected crossing the road between the forest edges away from the structure. These were mainly larger species (median weight 110g). In contrast, 25 species of mainly smaller species (median weight 15g) were detected using the wildlife overpass, primarily within the dense planted foliage, with an additional 14 species crossing the road directly above the structure. Although detected only occasionally during the study, the presence of species typically known only from the forest interior in the foliage of the wildlife overpass was especially noteworthy. Moreover, there was strong evidence that the wildlife overpass was being actively used as a corridor. Thus, as many smaller forest-dwelling species appear to be reluctant to cross roads, the construction of this vegetated wildlife overpass appears to have facilitated opportunities for movement that has been exploited by local species. Finally, these results strongly suggest that many of the large number of wildlife overpasses could be converted into safe passages over roads for a much larger proportion of the local biodiversity than has often been previously considered.