NEST PREDATION IN AN URBANIZING LANDSCAPE:THE ROLE OF EXOTIC SHRUBS

摘要: Nest predation is considered a primary force shaping avian communities, and landscape-scale features (e.g., amount of fragmentation) are generally recognized as factors mediating nest predation. These same features, however, may pro- mote invasion by exotic plants, which may, in turn, increase risk We examined whether the use shrubs (Lonicera spp. Rosa multiflora Thumb.) affected across 12 riparian forest sites along rural-urban gradient ( ,1- 47% urban land cover within 1 km). From 2001 to 2003, 188 Northern Cardinal (Cardinalis cardinalis) American Robin (Turdus migratorius) nests #5 m tall were monitored. substrate, height, distance from edge recorded for each nest, whereas placement patch characteristics measured only (n 5 68). To further assess relative rates native vs. while controlling edge, use, we conducted an artificial experiment at two rural sites. Artificial 79) placed similar heights honeysuckle, rose, substrates transect 50-75 edge. substrate landscape type alone failed account differences daily mortality rates. Instead, effect varied with matrix, such that urbanizing landscapes twice likely be dep- redated than substrates, irrespective also suffered higher failure substrates. Daily greater shrubs, due reduced height larger shrub volume surrounding nest. Nests 1.5-2 lower ground patches containing 6-9 times more volume. improve search efficiency mammalian predators, appear main predators our study Based on marks present recovered clay eggs, 68% events attributed mammals. findings demonstrate can reduce nesting success birds cause increased landscapes. This illustrates another way plants diminish habitat quality limit capacity forests contribute wildlife conservation; therefore, restoring com- munity prove beneficial.