Avian Use of Wildlife Overpasses

Abstract

Roads and road networks impact negatively on wildlife in a number of ways. Of major importance are vehicle-caused mortality, habitat fragmentation and barriers to animal movement. Together, the last two can lead to functional isolation of faunal populations, which, in turn, can potentially jeopardise the long-term persistence of wildlife populations. Wildlife overpasses are used to mitigate threats associated with the roads they span. Important conservation objectives are to allow safe passage and to maintain levels of dispersal between fragmented habitat areas, thereby allowing gene-flow and sustaining population viability of target species. It might be assumed that birds, having the ability to fly, can accommodate the effects of fragmentation well, and will benefit little from wildlife overpasses. A major objective of my study therefore was to evaluate the conservation value of a wildlife overpass in allowing passage of birds between forest areas bisected by a major road. • Methodology: The study was centred on the wildlife overpass which spans Compton Road, a 60m-wide, major four-lane arterial road in suburban Brisbane. The 15m-wide vegetated overpass connects two subtropical Eucalyptus forest reserves, which are bisected by the major road. • Surveys were undertaken to compare bird abundance and species composition on the overpass and in nearby forest sites.