Reduced predation of artificial nests in border-edge cuts on woodlots

Forest fragmentation has resulted in abrupt, artificial edges that may not provide transitional shrub habitat needed by edge- and shrub-nesting species. The creation of border-edge cuts (shrub transitional zones 15-40 m wide) at woodlot edges increases horizontal and vertical understory cover, and may affect habitat suitability for edge nesting species. Using artificial nests, wr tested the hypothesis that predation rates in border-edge cuts were lower than in uncut edges. During May-June 1997, we placed 10 artificial nests: containing 2 northern bobwhite (Colinus virginianus) eggs in each edge. Nests: were monitored fur depredation for 14 days. Most nest predation was attributed to avian predators. snakes. and small mammals. with a few nests depredated by large mammals. Mean pre dation rates were more than twice as high in uncut edges (88 +/- 7%; (x) over bar +/- SE) as in border-edge cuts (36 +/- 11%). Vegetation cover from 0 to 2 m at the nest site was greater at nests: in bolder-edge cuts (85.6 +/- 4.1%) than in uncut edges (59.5 =/- 3.3%). Predation rates within edges were negatively correlated with mean cover from 0 to 2 m at the nest site (r = -0.90) and mean cover at nest height (r=-0.86), However, predation rates on natural nests found the previous year in both edge types did not follow the same trend, indicating that further research is needed on both the differences in individual bird species' productivity and predator communities between the 2 edge types.